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Endogenous and dietary indoles: a class of antioxidants and radical scavengers in the ABTS assay.  

Science.gov (United States)

Indoles are very common in the body and diet and participate in many biochemical processes. A total of twenty-nine indoles and analogs were examined for their properties as antioxidants and radical scavengers against 2,2'-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) ABTS*+ radical cation. With only a few exceptions, indoles reacted nonspecifically and quenched this radical at physiological pH affording ABTS. Indoleamines like tryptamine, serotonin and methoxytryptamine, neurohormones (melatonin), phytohormones (indoleacetic acid and indolepropionic acid), indoleamino acids like L-tryptophan and derivatives (N-acetyltryptophan, L-abrine, tryptophan ethyl ester), indolealcohols (tryptophol and indole-3-carbinol), short peptides containing tryptophan, and tetrahydro-beta-carboline (pyridoindole) alkaloids like the pineal gland compound pinoline, acted as radical scavengers and antioxidants in an ABTS assay-measuring total antioxidant activity. Their trolox equivalent antioxidant capacity (TEAC) values ranged from 0.66 to 3.9 mM, usually higher than that for Trolox and ascorbic acid (1 mM). The highest antioxidant values were determined for melatonin, 5-hydroxytryptophan, trp-trp and 5-methoxytryptamine. Active indole compounds were consumed during the reaction with ABTS*+ and some tetrahydropyrido indoles (e.g. harmaline and 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid ethyl ester) afforded the corresponding fully aromatic beta-carbolines (pyridoindoles), that did not scavenge ABTS*+. Radical scavenger activity of indoles against ABTS*+ was higher at physiological pH than at low pH. These results point out to structural compounds with an indole moiety as a class of radical scavengers and antioxidants. This activity could be of biological significance given the physiological concentrations and body distribution of some indoles. PMID:15129740

Herraiz, Tomas; Galisteo, Juan

2004-03-01

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SCAVENGING ACTIVITY OF DICLOFENAC: INTERACTION WITH ABTS RADICAL CATION AND PEROXYL RADICALS  

OpenAIRE

The scavenging activity of diclofenac was estimated by its capability to bleach ABTS radical cation, and ORAC (oxygen radical absorbance capacity) methodology. In addition, GC-MS technique was used to establish if the lactamic derivative of diclofenac was formed as final product in the interaction with peroxyl radicals. Diclofenac bleached ABTS radical cation in a concentration-dependent way. In ORAC assays, diclofenac inhibited the consumption of fluorescein and c-phycocyanin mediated by per...

Rojo, C.; A?lvarez-figueroa, M. J.; Soto, M.; Can?ete, A.; Pessoa-mahana, D.; Lo?pez-alarco?n, C.

2009-01-01

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Evaluation of Antioxidative Activity of Croatian Propolis Samples Using DPPH? and ABTS?+ Stable Free Radical Assays  

OpenAIRE

Propolis is one of the richest sources of plant phenolics (flavonoids and phenolic acids), which are widely recognized as rather strong antioxidants. The aim of our work was to use colored stable free radical (DPPH· and ABTS·+) spectrophotometric and thin-layer chromatographic (TLC) assays to study the antioxidative behavior of the phenolics (caffeic acid, galangin and pinocembrin) most commonly present in Croatian propolis samples obtained from different Croatian regions. We propose a math...

Ivona Jasprica; Mirza Bojic; Ana Mornar; Erim Besic; Kajo Bucan; Marica Medic-Saric

2007-01-01

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SCAVENGING ACTIVITY OF DICLOFENAC: INTERACTION WITH ABTS RADICAL CATION AND PEROXYL RADICALS  

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Full Text Available The scavenging activity of diclofenac was estimated by its capability to bleach ABTS radical cation, and ORAC (oxygen radical absorbance capacity methodology. In addition, GC-MS technique was used to establish if the lactamic derivative of diclofenac was formed as final product in the interaction with peroxyl radicals. Diclofenac bleached ABTS radical cation in a concentration-dependent way. In ORAC assays, diclofenac inhibited the consumption of fluorescein and c-phycocyanin mediated by peroxyl radicals. An ORAC-fluorescein, and ORAC-c-phycocyanin value of 0.3, and 0.004 was estimated, respectively. From the downcurvature observed in Stern-Volmer-like plots, we postulated that the low protection of c-phycocyanin is related to secondary damage of c-phycocyanin by the secondary radical of diclofenac. By GC-MS studies only a 2,6-dichloroaniline derivative was detected as product afterthe reaction with peroxyl radicals.

C ROJO

2009-01-01

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SCAVENGING ACTIVITY OF DICLOFENAC: INTERACTION WITH ABTS RADICAL CATION AND PEROXYL RADICALS  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in english The scavenging activity of diclofenac was estimated by its capability to bleach ABTS radical cation, and ORAC (oxygen radical absorbance capacity) methodology. In addition, GC-MS technique was used to establish if the lactamic derivative of diclofenac was formed as final product in the interaction w [...] ith peroxyl radicals. Diclofenac bleached ABTS radical cation in a concentration-dependent way. In ORAC assays, diclofenac inhibited the consumption of fluorescein and c-phycocyanin mediated by peroxyl radicals. An ORAC-fluorescein, and ORAC-c-phycocyanin value of 0.3, and 0.004 was estimated, respectively. From the downcurvature observed in Stern-Volmer-like plots, we postulated that the low protection of c-phycocyanin is related to secondary damage of c-phycocyanin by the secondary radical of diclofenac. By GC-MS studies only a 2,6-dichloroaniline derivative was detected as product afterthe reaction with peroxyl radicals.

C, ROJO; M. J, ÁLVAREZ-FIGUEROA; M, SOTO; A, CAÑETE; D, PESSOA-MAHANA; C, LÓPEZ-ALARCÓN.

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Evaluation of Antioxidative Activity of Croatian Propolis Samples Using DPPH? and ABTS?+ Stable Free Radical Assays  

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Full Text Available Propolis is one of the richest sources of plant phenolics (flavonoids and phenolic acids, which are widely recognized as rather strong antioxidants. The aim of our work was to use colored stable free radical (DPPH· and ABTS·+ spectrophotometric and thin-layer chromatographic (TLC assays to study the antioxidative behavior of the phenolics (caffeic acid, galangin and pinocembrin most commonly present in Croatian propolis samples obtained from different Croatian regions. We propose a mathematical model providing a more sophisticated interpretation of the obtained results and a new parameter named antioxidative efficiency (AOE is introduced. The kinetic behaviour of chosen standards determined by spectrophotometric assays follows the exponential decrease of the absorption curve. Explained numerically, AOE represents the absolute value of the first derivative of an absorbance curve in the point A0/e (where A0 is the absorbance measured at t = 0 and e is the natural logarithm base. The advantage of this newly introduced parameter is that it provides an easy and accurate mutual comparison between the rates of antioxidative efficiency of different propolis samples. A TLC assay was only applicable in the case of the DPPH· radical. Dose-response curves were described using a linear function with AOE expressed as a coefficient of the slope. The chromatographic method was shown to be very rapid, reliable and easy-to-perform.

Ivona Jasprica

2007-05-01

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EVALUATION OF THE EXTINCTION COEFFICIENT OF THE ABTS DERIVED RADICAL CATION  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in spanish Conocer el valor exacto del coeficiente de extinción del radical catión derivado del ABTS es un pre-requisito para su empleo en la evaluación de la capacidad antioxidante de compuestos puros polifuncionales o mezclas complejas. Nosotros hemos realizado emperimentos que permiten establecer límites in [...] feriores y superiores para su valor. Los límites obtenidos 1.0 x 10(4) M-1 cm-1 Abstract in english The exact knowledge of the value of the extinction coefficient of the ABTS derived radical is necessary for its quantitative use in the evaluation of the antioxidant capacity of pure compounds and/or complex mixtures. We have performed experiments in order to stablish its lower and upper limits of i [...] ts value. The limits obtained, 1.0 x 10(4) M-1 cm-1

Carola, Henriquez; Eduardo, Lissi.

2002-12-01

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Alteration of fatty acids content during cow's and goat's milk fermentation with ABT-2 culture  

OpenAIRE

In this paper, changes in composition and contents of each fatty acid during fermentation with ABT-2 culture were examined. The objective of this study was to determinate the increase of short (SCFA) and medium (MCFA) chain fatty acids in goat's and cow's milk during fermentation with ABT-2 culture. The hypothesis of this study was that higher contents of SCFA and MCFA are produced in goat's milk in comparison with cow's milk, during fermentation with ABT-2 culture. Obtained results have show...

Vedran Sla?anac; Jovica Hardi; Hrvoje Pavlovi?; Mato Vlaini?; Mirela Lu?an

2005-01-01

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EVALUATION OF THE EXTINCTION COEFFICIENT OF THE ABTS DERIVED RADICAL CATION  

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Full Text Available The exact knowledge of the value of the extinction coefficient of the ABTS derived radical is necessary for its quantitative use in the evaluation of the antioxidant capacity of pure compounds and/or complex mixtures. We have performed experiments in order to stablish its lower and upper limits of its value. The limits obtained, \t\t\t\t1.0 x 10(4 M-1 cm-1 Conocer el valor exacto del coeficiente de extinción del radical catión derivado del ABTS es un pre-requisito para su empleo en la evaluación de la capacidad antioxidante de compuestos puros polifuncionales o mezclas complejas. Nosotros hemos realizado emperimentos que permiten establecer límites inferiores y superiores para su valor. Los límites obtenidos \t\t\t1.0 x 10(4 M-1 cm-1 <= épsilon 734 <= 1.6 x 10(4 M-1 cm-1 son compatibles con los valores reportados en la literatura. Sin embargo, el uso de estos valores conduced a coeficientes estequiométricos anormalmente altos para sus reacciones con comuestos simples como monofenoles y triptofano.

Carola Henriquez

2002-12-01

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Kinetics of oxidation of benzyl alcohols by the dication and radical cation of ABTS. Comparison with laccase-ABTS oxidations: an apparent paradox.  

Science.gov (United States)

Laccase, a blue copper oxidase, in view of its moderate redox potential can oxidise only phenolic compounds by electron-transfer. However, in the presence of ABTS (2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonate) as a redox mediator, laccase reacts with the more difficult to oxidise non-phenolic substrates, such as benzyl alcohols. The role of ABTS in these mediated oxidations is investigated. Redox interaction with laccase could produce in situ two reactive intermediates from ABTS, namely ABTS++ or ABTS*+. These species have been independently generated by oxidation with Ce(iv) or Co(iii) salts, respectively, and their efficiency as monoelectronic oxidants tested in a kinetic study towards a series of non-phenolic substrates; a Marcus treatment is provided in the case of ABTS++. On these grounds, intervention of ABTS++ as a reactive intermediate in laccase-ABTS oxidations appears unlikely, because the experimental conditions under which ABTS++ is unambiguously generated, and survives long enough to serve as a diffusible mediator, are too harsh (2 M H2SO4 solution) and incompatible with the operation of the enzyme. Likewise, ABTS*+ seems an intermediate of limited importance in laccase-ABTS oxidations, because this weaker monoelectronic oxidant is unable to react directly with many of the non-phenolic substrates that laccase-ABTS can oxidise. To solve this paradox, it is alternatively suggested that degradation by-products of either ABTS++ or ABTS*+ are formed in situ by hydrolysis during the laccase-ABTS reactions, and may be responsible for the observed oxidation of non-phenolics. PMID:15999194

Branchi, Barbara; Galli, Carlo; Gentili, Patrizia

2005-07-21

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Synthesis, crystal structure, ABTS radical-scavenging activity, antimicrobial and docking studies of some novel quinoline derivatives  

Science.gov (United States)

In this study, a series of nine novel 2-chloroquinolin-3-yl ester derivatives have been synthesized via a two-step protocol from 2-chloroquinoline-3-carbaldehyde. The structures of all these compounds were confirmed by spectral data. The single crystal X-ray structure of two derivatives, (2-chloroquinolin-3-yl)methyl acetate [6a] and (2-chloro-6-methylquinolin-3-yl)methyl acetate [6e] have also been determined. The synthesized compounds were further evaluated for their ABTS radical-scavenging activity and antimicrobial activities. Amongst all the tested compounds, 6a exhibited maximum scavenging activity with ABTS. Concerning antibacterial and antifungal activities, compound (2-chloro-6-methoxyquinolin-3-yl)methyl 2,4-dichlorobenzoate [6i] was found to be the most active in the series against B. subtilis, S. aureus, E. coli, K. pneumonia, C. albicans and A. niger species. The structure-antimicrobial activity relationship of these derivatives were studied using Autodock.

Tabassum, Sumaiya; Suresha Kumara, T. H.; Jasinski, Jerry P.; Millikan, Sean P.; Yathirajan, H. S.; Sujan Ganapathy, P. S.; Sowmya, H. B. V.; More, Sunil S.; Nagendrappa, Gopalpur; Kaur, Manpreet; Jose, Gilish

2014-07-01

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Alteration of fatty acids content during cow's and goat's milk fermentation with ABT-2 culture  

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Full Text Available In this paper, changes in composition and contents of each fatty acid during fermentation with ABT-2 culture were examined. The objective of this study was to determinate the increase of short (SCFA and medium (MCFA chain fatty acids in goat's and cow's milk during fermentation with ABT-2 culture. The hypothesis of this study was that higher contents of SCFA and MCFA are produced in goat's milk in comparison with cow's milk, during fermentation with ABT-2 culture. Obtained results have shown that fermentation process in goat's milk is faster than in cow's milk. The number of viable cells of probiotic bacteria Lactobacillus acidophilus La-5 and Bifidobacterium spp. was statistically greater in goat's milk than in cow's milk; consequently, pH value decreased more obviously in goat's milk than in cow's milk during whole fermentation process. Increase of SCFA and MCFA contents during fermentation was noted in both types of milk due to activity of bifidobacteria derived from ABT-2 culture. However, considerably higher amounts of examined SCFA and MCFA were produced in goat's milk than in cow's milk.

Vedran Sla?anac

2005-04-01

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Fatty acid hydroxytyrosyl esters: structure/antioxidant activity relationship by ABTS and in cell-culture DCF assays.  

Science.gov (United States)

A large series of hydroxytyrosyl esters of C2-C18 fatty acids with increasing lipophilicity was prepared by a new highly efficient method based on acylation of methylorthoformate-protected hydroxytyrosol. All products were tested for relative antioxidant effect using ABTS assays in ethanolic medium and DCF assays in L6 cells. No linear correlation between lipophilicity and antioxidant effect was found. ABTS assays showed a growing antioxidant capacity, with respect to hydroxytyrosol, only for medium-sized ester chains (C4-C10) and a nearly constant capacity for the higher homologues. This has been rationalized by molecular dynamics experiments in terms of partial shielding of the catecholic hydroxyls by long-chain esters. A similar and dose-dependent pattern was observed in DCF assays in L6 cells, but a sharp antioxidant activity drop resulted for long-chain esters, probably due to membrane entrapment. PMID:20397651

Tofani, Daniela; Balducci, Valentina; Gasperi, Tecla; Incerpi, Sandra; Gambacorta, Augusto

2010-05-12

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The BH3-mimetic ABT-737 targets the apoptotic machinery in cholangiocarcinoma cell lines resulting in synergistic interactions with zoledronic acid  

OpenAIRE

Abstract Purpose In TFK-1 and EGI-1 cholangiocarcinoma cell lines, zoledronic acid (ZOL) determines an S-phase block without apoptosis. Here, we investigated the occurrence of apoptosis stigmata when ZOL is associated to the BH3-mimetic ABT-737. Methods In EGI-1 and TFK-1 cholangiocarcinoma cell lines untreated or treated with ABT-737 alone or in combination with ZOL, the pro-survival protein’s pattern (...

Romani, Antonello A.; Desenzani, Silvia; Morganti, Marina M.; Baroni, Maria Cristina; Borghetti, Angelo F.; Soliani, Paolo

2010-01-01

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Optimisation of the azinobis-3-ethyl-benzothiazoline-6-sulphonic acid radical scavenging assay for physiological studies of total antioxidant activity in woody plant germplasm.  

Science.gov (United States)

A robust spectroscopic method for determining total antioxidant activity in aqueous extractions has been applied to tissues from diverse woody plant species, including seeds of Coffea arabica and in vitro shoots from Ribes nigrum, Picea sitchensis and Shorea leprosula. The assay involves scavenging of an ABTS [2,2'-azinobis-(3-ethyl-benzothiazoline-6-sulphonic acid)] radical generated by the reaction of potassium persulphate with ABTS to produce an ABTS*(+) chromophore (lambda=734 nm). Antioxidants reduce ABTS*(+) back to ABTS with a concomitant decrease in absorbance. Aqueous extractions from C. arabica and S. leprosula had considerably higher (110-205 micromol Trolox eq. g(-1) FW) total antioxidant activities than P. sitchensis and R. nigrum (6-11 micromol Trolox eq. g(-1) FW). Further studies in two of these species showed that the inclusion of water-insoluble polyvinylpyrrolidone during aqueous tissue extraction enabled the combined phenolic and alkaloid antioxidant activity to be determined. These fractions accounted for 85% and 60% of total antioxidant activity for C. arabica seeds and R. nigrum shoots, respectively. The ABTS radical scavenging assay is presented herein as a robust method for determining total antioxidant activity in germplasm from diverse woody plant tissues and species. Its applicability to study oxidative stress in tissue cultures and germplasm employed in plant biotechnology, breeding and stress physiology programmes is discussed. PMID:16762559

Johnston, Jason W; Dussert, Stéphane; Gale, Samantha; Nadarajan, Jayanthi; Harding, Keith; Benson, Erica E

2006-04-01

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Antioxidant components of Viburnum opulus L. determined by on-line HPLC-UV-ABTS radical scavenging and LC-UV-ESI-MS methods.  

Science.gov (United States)

Antioxidant activity of the juice and seed and skin extracts prepared with methanol, acetonitrile, and water of Viburnum opulus L. grown in Eastern Black Sea Region were studied with an on-line HPLC-ABTS method and off-line antioxidant methods, among which a linear positive correlation was observed. The fruit extracts were analysed with the HPLC-UV method optimised with 14 standard phenolics. Identification of the phenolic components in the juice was made using an HPLC-UV-ESI-MS method. Nineteen phenolic compounds in juice were identified by comparing the retention times and mass spectra with those of the standards and the phenolics reported in the literature. The major peaks in the juice belonged to coumaroyl-quinic acid, chlorogenic acid, procyanidin B2, and procyanidin trimer. Quite different antioxidant composition profiles were obtained from the extracts with the solvents of different polarities. The antioxidant activities of the seed extracts were higher than those of the skin extracts in general. PMID:25577058

Karaçelik, Ayça Akta?; Küçük, Murat; ?skefiyeli, Zeynep; Aydemir, Sezgin; De Smet, Seppe; Miserez, Bram; Sandra, Patrick

2015-05-15

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Autographic Assay for the Rapid Detection of Antioxidant Capacity of Liquid and Semi-solid Pharmaceutical Formulations Using ABTS•+ Immobilized by Gel Entrapment  

OpenAIRE

An autographic assay suitable for the detection of antioxidant compounds in a complex matrix (liquid and semi-solid pharmaceutical formulations) or in isolated compounds was described. The pre-formed radical monocation of 2,2?-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS•+) was generated by oxidation of ABTS with potassium persulfate and reduced in the presence of hydrogen-donating antioxidants. For a further comparative estimation of its applicability and sensitivity, differen...

Zampini, Iris Catiana; Ordon?ez, Roxana Mabel; Isla, Mari?a Ine?s

2010-01-01

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Isoprene, sulphoxy radical-anions and acidity  

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Full Text Available Transformation of isoprene coupled with autoxidation of SIV in aqueous solutions was studied experimentally and by chemical-kinetic modelling over broad range of solution acidities (pH=3–9 to complement the research on aqueous-phase and heterogeneous transformation of isoprene reported recently by many laboratories. Isoprene significantly slowed down the autoxidation in acidic and basic solutions, and accelerated it slightly in neutral solutions. Simultaneously, production of sulphate ions and formation of solution acidity were significantly reduced. Formation of sulphite and sulphate derivatives of isoprene – sulphurous acid mono-(2-methyl-4-oxo-but-2-enyl ester (m/z=162.9, sulphurous acid mono-(4-hydroxy-2-methyl-but-2-enyl ester (m/z=164.9, sulphuric acid mono-(2-methyl-4-oxo-but-2-enyl ester (m/z=178.9, sulphuric acid mono-(4-hydroxy-2-methyl-but-2-enyl ester (m/z=180.9 – was indicated by mass spectroscopic analysis of post-reaction mixtures. The results of experiments were explained by changes in a subtle quantitative balance of three superimposed processes whose rates depended in different manner on the acidity of reacting solutions – the scavenging of sulphoxy radicals by isoprene, the formation of sulphoxy radicals during further reactions of isoprene radicals, and the autoxidation of SIV itself. A chemical mechanism based on this idea was explored numerically to show good agreement with experimental data. Interaction of isoprene with sulphur(IV species and oxygen can possibly result in formation of new organosulphate components of atmospheric aerosols and waters, and influence distribution of reactive sulphur and oxygen species in isoprene-emitting organisms exposed to SIV pollutants.

K. J. Rudzi?ski

2008-12-01

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Trapping of fatty acid allyl radicals generated in lipoxygenase reactions in biological fluids by nitroxyl radical.  

Science.gov (United States)

Nitroxyl radicals can trap fatty acid allyl radicals on ferric-lipoxygenases at lower oxygen content, which are an intermediate in the lipoxygenase reaction. In the present study, we examined whether nitroxyl radical-trapping of fatty acid allyl radicals on the enzyme proceeds in biological fluids with abundant antioxidants. The fatty acid allyl radical-nitroxyl radical adducts were quantified by HPLC with electrochemical detection (HPLC-ECD); the adducts in eluate degraded into nitroxyl radical by passing through heating coil at 100 degrees C, and then nitroxyl radical was detected by electrochemical detector. Soybean 15-lipoxygenase and nitroxyl radical (3-carbamoyl-2,2,5,5-tetramethyl-3-pyrroline-N-oxyl, CmDeltaP) were mixed with rat serum prepared from fresh venous blood, and the solution was stood at 37 degrees C for 1 h. One volume of the solution was mixed with 5 vols of cold acetonitrile. After centrifugation, the supernatant was subjected to HPLC-ECD. Arachidonate allyl radical-CmDeltaP adducts as well as linoleate allyl radical-CmDeltaP adducts were detected in the solution, and the content of these adducts remarkably increased in the presence of phospholipase A(2). It is proved for the first time that nitroxyl radical traps fatty acid allyl radicals generated in the lipoxygenase reaction in biological fluid without competition from endogenous antioxidants. PMID:20082280

Takajo, Tokuko; Tsuchida, Kazunori; Yokota, Azusa; Koshiishi, Ichiro

2010-07-01

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Determination of protective properties of Bardejovske Kuple spa curative waters by rotational viscometry and ABTS assay  

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Full Text Available Mineral waters from Bardejovske Kupele spa are natural, strongly mineralized, with healing effects. They are classified as hydrocarbonic - containing chloride and sodium - carbonic, cold, hypotonic, with a relatively high boric acid content. Potential anti-oxidative effects of curative waters from Bardejovske Kupele were investigated against the hyaluronan (HA degradation. High-molar-mass HA was exposed to the action of ascorbate and cupric ions, which initiate free-radical chain degradation. Time-dependent changes of dynamic viscosity (h of the HA solutions were monitored by rotational viscometry. The radical scavenging capacity of curative waters was determined by the ABTS assay. Despite a significantly high content of transition metal ions, especially iron, remarkable protective effects of the two curative spa waters were found, namely Alzbeta and Klara. Even though “Alzbeta´s“ iron content was 3.5-fold higher than “Klara´s“, “Alzbeta“ was shown to have better protective properties against the HA degradation compared to “Klara“. Bolus addition of ferric ions to the reaction system instead of the natural iron-containing curative water caused a significant HA degradation. The ABTS decolorization assay revealed that the curative spa waters were proven as poorly effective scavengers of the ABTS·+ cation radical.

TOPOLSKA Dominika

2014-02-01

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Total Phenolic Content and Free Radical Scavenging Activity of Malva parviflora L. (Malvaceae  

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Full Text Available The free radical scavenging activity of the methanolic extract of Malva parviflora L. was examined using spectroscopic method against 2, 2-diphenyl-1-picrylhydrazyl radical (DPPH•, radical cation ABTS•+ (2, 2`-azinobis [3-ethylbenzothiazoline-6-sulfonic acid] diammonium salt and the ferric reducing agent. Total phenolic, flavonoid and proanthocyanidin contents were also determined to assess their effects on the antioxidant activity of the extract. The results showed that the methanol extract of M. parviflora differed in its capacity to quench or inhibit DPPH• and ABTS•+. The extract showed a greater ability to quench ABTS•+ by inhibiting 94.3% of the radical cation while it inhibited 9.3% of DPPH•. The free radical scavenging activities were compared using BHT and rutin as reference antioxidants. The plant possessed a higher flavonoid content than phenolics and proanthocyanidins and a positive linear correlation was established between these polyphenols and the free radical scavenging activities.

A.J. Afolayan

2008-01-01

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ESR study of the acid dissociation of NH protons. II. Cyclic peptide radicals and related radicals  

International Nuclear Information System (INIS)

Free radicals formed by the reaction of OH or O- radicals with alicyclic compounds containing a peptide group (-CONH-) and structurally related compounds have been studied by the in situ radiolysis-steady state ESR method. Eight cyclic peptide radicals resulting from hydrogen abstraction from the C-H bond adjacent to the peptide group have been observed. They are divided into two groups on the basis of the skeletal structure of the radicals: greater than C-NH-CO- and greater than C-CO-NH-. In basic solutions significant changes occur in the ESR parameters of these radicals which can be interpreted in terms of the dissociation of the NH proton in a peptide group. The pK/sub a/ values for the NH proton dissociation have been determined to be in the range of 7.6 to 13.6 for eight cyclic peptide radicals from 5-methyl-2-pyrrolidinone, 2-pyrrolidinone, 2-pyrrolidone-5-carboxylic acid, hydantoin (for both first and second NH proton dissociations), 1-methylhydantoin, 2-thiohydantoin (second dissociation only), succinimide, and 2,5-piperazinedione (first dissociation only) and 10.9 for a related cyclic radical from 2-oxazolidone. These pK/sub a/ values are considerably lower than those for corresponding linear peptide radicals, partly because ?-electron density on the nitrogen atom decreases in cyclic peptide radicals with a more delocalized ?-electron system. Within each group of cyclicpeptide radicals with greater than C-NH-CO- or greater than C-CO-NH- the sameNH-CO- or greater than C-CO-NH- the same trend of changes in ESR parameters was observed upon the dissociation of peptide proton

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Unexpectedly high indoor hydroxyl radical concentrations associated with nitrous acid  

OpenAIRE

The hydroxyl (OH) radical is the most important oxidant in the atmosphere since it controls its self-oxidizing capacity. The main sources of OH radicals are the photolysis of ozone and the photolysis of nitrous acid (HONO). Due to the attenuation of solar radiation in the indoor environment, the possibility of OH formation through photolytic pathways indoors has been ignored up to now. In the indoor air, the ozonolysis of alkenes has been suggested as an alternative route of OH formation. Mod...

Go?mez Alvarez, Elena; Amedro, Damien; Afif, Charbel; Gligorovski, Sasho; Schoemaecker, Coralie; Fittschen, Christa; Doussin, Jean-francois; Wortham, Henri

2013-01-01

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Antioxidant activity of selected phenols estimated by ABTS and FRAP methods  

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Full Text Available Introduction: Phenols are the most abundant compounds in nature. They are strong antioxidants. Too high level of free radicals leads to cell and tissue damage, which may cause asthma, Alzheimer disease, cancers, etc. Taking phenolics with the diet as supplements or natural medicines is important for homeostasis of the organism. Materials and methods: The ten most popular water soluble phenols were chosen for the experiment to investigate their antioxidant properties using ABTS radical scavenging capacity assay and ferric reducing antioxidant potential (FRAP assay. Results and discussion: Antioxidant properties of selected phenols in the ABTS test expressed as IC50 ranged from 4.332 ?M to 852.713 ?M (for gallic acid and 4- hydroxyphenylacetic acid respectively. Antioxidant properties in the FRAP test are expressed as ?mol Fe2 /ml. All examined phenols reduced ferric ions at concentration 1.00 x 10-3 mg/ml. Both methods are very useful for determination of antioxidant capacity of water soluble phenols.

Izabela Biskup

2013-09-01

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A pulse radiolysis study of some dicarboxylic acids of citric acid cycle. The kinetics and spectral properties of the free radicals formed by reaction with the OH radical  

International Nuclear Information System (INIS)

The reactions between the OH radical and fumaric acid, maleic acid, malic acid and succinic acid were studied using pulse radiolysis techniques. The rates of reaction, the absorption spectra of the resultant free radicals and the rates of disappearance of those radicals were determined as a function of pH over virtually the entire pH range (pH 2-14). (orig.)

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The antioxidant activity of wines determined by the ABTS(+) method: influence of sample dilution and time.  

Science.gov (United States)

The free radical scavenging activity of 42 Spanish commercial wines was determined using the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS(+)). The ABTS(+) radical was generated enzymatically using a horseradish peroxidase and hydrogen peroxide. The presence of wine phenolic compounds caused the absorbance of the radical to decay at 414nm. The measurement conditions were optimised. The total phenolic content of wines ranged from 1262 to 2389mgl(-1) for red wines and 70 to 407mgl(-1) for white wines, expressed as gallic acid equivalents. The phenolic content of Sherry wines was similar to that of white wines. Optimum dilutions for white and Sherry wines were set up as a function of their total phenolic content (for total phenol index, TPI300mg gallic acid per liter, dilution 1:10 to 3:10). Red wines absorb at the wavelength of measurement and dilutions between 0.35:10 and 0.1:10 are advisable. Reaction kinetics were also monitored and the antioxidant activity, expressed as Trolox Equivalent Antioxidant Capacity (TEAC), was determined at 2 and 15min of reaction. The mean values for TEAC(2min) were 5.01+/-1.40mM for red wines, 0.46+/-0.32mM for white wines and 0.26+/-0.19mM for Sherry wines. At 15min, mean values were 6.93+/-2.41mM for red wines, 0.67+/-0.47mM for white wines and 0.26+/-0.19mM for Sherry wines. The correlation coefficients were better at 2min (r=0.9012) than at 15min (r=0.8462) when compared with TPI. Hence, TEAC(2min) seems to be a more appropriate measure. PMID:18969632

Villaño, D; Fernández-Pachón, M S; Troncoso, A M; García-Parrilla, M C

2004-10-01

27

Comparative Evaluation of the Radical-Scavenging Activities of Fucoxanthin and Its Stereoisomers  

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Full Text Available Fucoxanthin (Fuco is a characteristic carotenoid of brown seaweeds. In the present study, Fuco and its stereoisomers 9'Z-Fuco, 13Z- and 13'Z-Fuco were extracted from Laminaria japonica Aresch. They were isolated and purified by silica gel column chromatography, Sephadex LH-20, and reversed-phase HPLC. The radical-scavenging activities of the three stereoisomers were evaluated toward 1,1-diphenyl-2-picrylhydrazyl (DPPH radical, 2-2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS radical, hydroxyl radical, and superoxide radical. The order of 1,1-diphenyl-2-picrylhydrazyl (DPPH radical-scavenging activity was 13Z- and 13'Z-Fuco > (all-E-Fuco > 9'Z-Fuco. The order of 2-2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS and hydroxyl radical-scavenging activities were 9'Z-Fuco > (all-E-Fuco > 13Z-and 13'Z-Fuco. The order of superoxide radical-scavenging activity was 13Z- and 13'Z-Fuco > (all-E-Fuco > 9'Z-Fuco. The scavenging activities of Fuco and its stereoisomers toward the four radical types were all dose-dependent. The ABTS, DPPH, and superoxide radical-scavenging activities were all weaker than that of tocopherol (VE, while their hydroxyl radical-scavenging activities were stronger than that of VE. The results confirmed that Fuco and its stereoisomers have potent antioxidant activities.

Yiping Zhang

2014-02-01

28

treatment with laccase and abts  

Directory of Open Access Journals (Sweden)

Full Text Available El sistema ABTS (ácido 2,2´-[3-etil benzotiazolin-6-sulfónico]-lacasa se empleó para decolorar tanto tela de mezclilla como una solución preparada de índigo. Después del tratamiento, la mezclilla adquirió un aspecto de usada, sin que las fibras mostraran evidencia de daño, mientras que la solución de índigo se decoloró. Adicionalmente, el análisis de la biodegradación de los desechos acuosos de la decoloración de la mezclilla y la solución decolorada control de índigo mostraron que, en ambos casos el agua residual fue fácilmente biodegradada tanto aeróbica como anaeróbicamente, mientras que la solución control de índigo requirió de 5 días para biodegradarse aeróbicamente y no sufrió ningún cambio en el sistema anaeróbico. El ABTS oxidado ó la lacasa por sí solos no decoloraron la mezclilla ni la solución de índigo bajo las mismas condiciones experimentales en que se empleó la combinación de ambos ABTS-lacasa. Esto se explica porque, durante la reacción de decoloración, el mediador se recicla varias veces entre la enzima y el colorante, de tal forma que en 30 minutos, una molécula de ABTS oxida 800 moléculas de índigo, además la velocidad de decoloración fue dos órdenes de magnitud mayor que la velocidad cuando se empleó el ABTS ó la enzima en forma individual.

Myrna Sol\\u00EDs-Oba

2008-01-01

29

Hydroxyl radical scavenging activity of naturally occurring furan fatty acids.  

Science.gov (United States)

As a part of our work on the antioxidant properties of naturally occurring furan fatty acids (F acids), we evaluated their hydroxyl radical (HO.) scavenging activity by an electron spin resonance (ESR) spin trapping technique with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). The additions of F acids to the incubation mixture of Fe2(+)-diethylenetriaminepentaacetic acid complex, H2O2 and DMPO decreased the intensity of the DMPO-OH adduct signal in a dose-dependent way. This decrease was not attributed to the destruction of DMPO-OH adduct by F acids. Kinetic competition studies indicated that the decrease in DMPO-OH signal intensity was mainly due to the competition of F acids with DMPO for HO., and not to the inhibition of the HO. generation system itself. F acids were found to react rapidly with HO. at approximately a diffusion-controlled rate (1.7 x 10(10)M-1 s-1). Comparison with the common HO. scavengers indicated that the rate constant of F acids is higher than those of mannitol and ethanol, and is compatible with those of histidine and dimethylsulfoxide, demonstrating that F acids are a potent HO. scavenger. It is suggested that F acids may serve as antioxidants in biological systems through their ability to scavenge HO.. PMID:8996648

Okada, Y; Kaneko, M; Okajima, H

1996-12-01

30

Unexpectedly high indoor hydroxyl radical concentrations associated with nitrous acid.  

Science.gov (United States)

The hydroxyl (OH) radical is the most important oxidant in the atmosphere since it controls its self-oxidizing capacity. The main sources of OH radicals are the photolysis of ozone and the photolysis of nitrous acid (HONO). Due to the attenuation of solar radiation in the indoor environment, the possibility of OH formation through photolytic pathways indoors has been ignored up to now. In the indoor air, the ozonolysis of alkenes has been suggested as an alternative route of OH formation. Models and indirect measurements performed up to now according to this hypothesis suggest concentrations of OH radicals on the order of 10(4)-10(5) molecules per cubic centimeter. Here, we present direct measurements of significant amounts of OH radicals of up to 1.8?10(6) molecules per cubic centimeter during an experimental campaign carried out in a school classroom in Marseille. This concentration is on the same order of magnitude of outdoor OH levels in the urban scenario. We also show that photolysis of HONO is an important source of OH radicals indoors under certain conditions (i.e., direct solar irradiation inside the room). Additionally, the OH concentrations were found to follow a linear dependence with the product J(HONO)?[HONO]. This was also supported by using a simple quasiphotostationary state model on the OH radical budget. These findings force a change in our understanding of indoor air quality because the reactivity linked to OH would involve formation of secondary species through chemical reactions that are potentially more hazardous than the primary pollutants in the indoor air. PMID:23898188

Gómez Alvarez, Elena; Amedro, Damien; Afif, Charbel; Gligorovski, Sasho; Schoemaecker, Coralie; Schoemacker, Coralie; Fittschen, Christa; Doussin, Jean-Francois; Wortham, Henri

2013-08-13

31

[Free radicals, polyunsaturated fatty acids, cell death, brain aging].  

Science.gov (United States)

Neuronal death generally involves, directly or indirectly, free radical attack and peroxidation. Targets are nucleic acids, proteins, the cytoskeleton, the extracellular matrix and especially membrane polyunsaturated fatty acids. a) One example for the fundamental role of fatty acids. Dietary fatty acids, and more particularly essential polyunsaturated fatty acids, have a direct influence on the composition of cerebral membranes, and hence on their functioning. Each of the two series of polyunsaturated fatty acids plays a particular role. In animals, a deficiency in linolenic acid causes serious perturbations in the nervous system. In fact, feeding animals with oils that have a low n-3 content leads to severe abnormalities in the composition of membranes, both of the brain and other organs. The rate of recovery from these anomalies is extremely slow in the brain, but rapid in the liver. Compared to certain other organs, the nervous system is neither protected against deficiency nor has it priority in the satisfaction if its needs. A decrease in acids of the linolenic series in the membranes results in a 40% reduction of Na-K-ATPase in nerve endings and a 20% reduction in 5'-nucleotidase. It also leads to anomalies in the electroretinogram which disappear with age. This deficiency in linolenic acid has little effect on motor function and disturbes activity and emotivity only slightly, but it seriously affects learning tasks. The presence of linolenic acid in the diet confers greater resistance to certain neurotoxic substances (triethyl lead, for example). Fatty acids essential for the brain could be those with very long chains. They are probably synthesized in the liver from linolenic and linoleic acids. They can also be supplied directly by food. However, if the diet contains a large proportion of very long chain fatty acids (fish oils), the lipid composition of all organs, including the brain, is altered. During the period of brain development there is a linear relation between the polyunsaturated fatty acid content of the brain and that of the diet. The requirement in linolenic acid is 200 mg/100 g of diet (0.4% of calories). That of linoleic acid is 1,200 mg/100 g of diet (2.4% of calories). b) Peroxidation of polyunsaturated fatty acids. Arachidonic acid is released by lysis of phospholipids (it is directly toxic), its peroxidized derivatives are extremely toxic. Peroxidation of membrane lipids alters enzymatic activity, the relationship between receptor and ligand, transport, and the symmetry of the lipid bilayer.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:2846129

Bourre, J M

1988-01-01

32

Studies on the antioxidant activity of Lippia citriodora infusion: scavenging effect on superoxide radical, hydroxyl radical and hypochlorous acid.  

Science.gov (United States)

Lippia citriodora is an herbal species which contains several flavonoids and phenolic acids. In view of the pharmacological interest in natural phenolic compounds as antioxidants, this study examined the superoxide radical, hydroxyl radical and hypochlorous acid scavenging activities of L. citriodora infusion. Superoxide radical was generated either in an enzymatic or in a chemical system, and scavenging ability was assessed by the inhibition of nitroblue tetrazolium reduction. Hydroxyl radical was generated by the reaction of an iron-EDTA complex with H2O2 in the presence of ascorbic acid, and was assayed by evaluating deoxyribose degradation. Hypochlorous acid scavenging activity was tested by measuring the inhibition of 5-thio-2-nitrobenzoic acid oxidation. The results demonstrate that this infusion has a potent superoxide radical scavenging activity and a moderate scavenging activity of hydroxyl radical and hypochlorous acid. The chemical composition of the lyophilized infusion was also determined in an attempt to establish its relationship with the antioxidant activity found in the present study. PMID:12392088

Valentão, Patricia; Fernandes, Eduarda; Carvalho, Félix; Andrade, Paula Branquinho; Seabra, Rosa Maria; de Lourdes Basto, Maria

2002-10-01

33

Pulse radiolytic study of the acid dissociation of OH protons in radicals related to salicylic acid  

International Nuclear Information System (INIS)

The deprotonation of carboxylated benzosemiquinone radicals prepared by pulse radiolytic oxidation of dihydroxybenzoic acids has been examined by time-resolved absorption spectrophotometry. The pK/sub a/ for dissociation of the OH proton in 3-carboxyl-1,4-benzosemiquinone is found to be 6.47 or 2.4 units higher than that in the unsubstituted radical. This pK/sub a/ is, however, well below that of the OH proton in salicyclic acid (13.6) so that hydrogen bonding is appreciably decreased by the delocalization of the unpaired spin in this radical. Protonation of the basic form of the radical occurs at the diffusion-controlled rate. The rate constant for deprotonation by OH- is relatively low, 4.7 X 107 M-1 s-1, so that reaction with base becomes important only above pH 10. As a result this radical provides an excellent system for studying acid-base equilibration processes in near neutral solutions. Azide ion is shown to be an efficient catalyst which allows the acid-base equilibrium to be examined on the 10-?s time scale. Deprotonation is also catalyzed by the dihydroxybenzoic acid used as the radical source. Analogous studies on 4-carboxy-1,3-benzosemiquinone give the pK/sub a/ as 7.9. In spite of this high pK/sub a/, which indicates the rate constant for spontaneous dissociation of this radical to be > 103 s-1, the rate constant for deprotonation by OH-, 4.9 X 108 M-1 s8 M-1 s-1, is considerably higher than in the case of 3-carboxy-1,4-benzosemiquinone

34

Extracellular ABTS-oxidizing activity of autochthonous fungal strains from Argentina in solid medium.  

Science.gov (United States)

The screening for extracellular oxidases and peroxidases from autochthonous filamentous fungi isolated from different substrates is an important step towards the detection of extracellular fungal oxidative systems. Thirty-one autochthonous fungal strains from Argentina, belonging to different ecophysiological and taxonomic groups, were plate-screened for their ability to produce extracellular oxidoreductases. Modified Kirk solid medium containing the chromogen 2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) was used to determine the presence of this extracellular activity. The fungi tested were grouped according to the colour intensity of the modified Kirk medium in: a) species without extracellular ABTS-oxidizing activity; b) species with low extracellular ABTS-oxidizing activity; c) species with moderate extracellular ABTS-oxidizing activity; d) species with high extracellular ABTS-oxidizing activity. The assay revealed extracellular ABTS-oxidizing activity in 90% of the strains tested. All species of Basidiomycetes used exhibited ABTS-oxidizing activity, except Laeticorticium roseum. Aspergillus terreus and Epicoccum purpurascens (Deuteromycetes) did not show extracellular oxidative activity on ABTS. Agrocybe aegerita, Amauroderma boleticeum, Cladosporium cladosporioides, Coriolopsis rigida, Grammothele subargentea, Graphium putredinis, Hexagona hydnoides, Hexagona papyraceae, Loweporus lividus, Peniophora albobadia, Phellinus everhartii, Phellinus gilvus; Phellinus linteus; Pleurotus laciniatocrenatus, Pycnoporus sanguineus, Rigidoporus ulmarius, Steccherinum rawakense, Talaromyces helicus, Trametes elegans, Trametes pavonia, Trametes villosa and Trichaptum sector are reported here for the first time as species capable of producing ABTS-oxidizing extracellular oxidorreductases. PMID:15813698

Saparrat, M C; Margarita-Bucsinszky, A M; Alfio-Tournier, H; Cabello, M N; Arambarri, A M

2000-06-01

35

A convenient label free colorimetric assay for pyrophosphatase activity based on a pyrophosphate-inhibited Cu(2+)-ABTS-H2O2 reaction.  

Science.gov (United States)

The evaluation of pyrophosphatase (PPase) activity plays an important role in diagnosing diseases and understanding the function of PPase in the related biological events. In this work, an inhibition effect of pyrophosphate (PPi) on Cu(2+)-catalyzed H2O2-mediated oxidation of 2,2-azinobis(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) was observed. We utilize this inhibition effect to develop a convenient label free visual method for PPase activity detection. A hydroxyl radical could be generated from a Cu(2+)-based Fenton-like reaction, and then reacted with ABTS to produce colored ABTS?(+). The strong complexation between PPi and Cu(2+) disturbed this Cu(2+)-catalyzed ABTS-H2O2 reaction probably due to changing redox potentials of Cu(2+) towards H2O2. The PPase-catalyzed hydrolysis of PPi into Pi prohibited the complexation, resulting in the recovery of catalytic capability of Cu(2+). As a result, the solution color changed from colorless to green with a remarkable increase of absorbance. Compared with the traditional PPase assays, the developed visual assay is cost-effective and easy to implement. And a high sensitivity for PPase with a detection limit of 0.027 U mL(-1) was achieved. Moreover, the proposed colorimetric strategy was also applied to evaluate PPase inhibition and exhibited a good assay performance in complex biological samples. PMID:25316090

Zhang, Liangliang; Li, Mei; Qin, Yingfeng; Chu, Zhidan; Zhao, Shulin

2014-12-01

36

Radical and Non-Radical Mechanisms for Alkane Oxidations by Hydrogen Peroxide?Trifluoroacetic Acid  

Energy Technology Data Exchange (ETDEWEB)

The oxidation of cyclohexane by the H2O2?trifluoroacetic acid system is revisited. Consistent with a previous report (Deno, N.; Messer, L. A. Chem. Comm. 1976, 1051), cyclohexanol forms initially but then esterifies to cyclohexyl trifluoroacetate. Small amounts of trans-1,2-cyclohexadiyl bis(trifluoroacetate) also form. Although these products form irrespective of the presence or absence of O2, dual mechanisms are shown to operate. In the absence of O2, the dominant mechanism is a radical chain reaction that is propagated by CF3• abstracting H from C6H12 and SH2 displacement of C6H11• on CF3CO2OH. The intermediacy of C6H11• and CF3• is inferred from production of CHF3 and CO2 along with cyclohexyl trifluoroacetate, or CDF3 when cyclohexane-d12 is used. In the presence of O2, fluoroform and CO2 are suppressed, the reaction rate slows, and the rate law approaches second order (first order in peracid and in C6H12). Trapping of cyclohexyl radicals by quinoxaline is inefficient except at elevated (75 °C) temperatures. Fluoroform and CO2, telltale evidence for the chain pathway, were not produced when quinoxaline was present in room temperature reactions. These observations suggest that a parallel, nonfree radical, oxenoid insertion mechanism dominates when O2 is present. A pathway is discussed in which a biradicaloid-zwiterionic transition state is attained by hydrogen transfer from alkane to peroxide oxygen with synchronous O?O bond scission.

Camaioni, Donald M.; Bays, J. Timothy; Shaw, Wendy J.; Linehan, John C.; Birnbaum, Jerome C.

2001-02-09

37

Pulse radiolysis studies on reactions of ?-hydroxyalkyl radicals with nicotinamide and 6-methyl nicotinic acid  

International Nuclear Information System (INIS)

Reactions of ?-hydroxyalkyl radicals derived from 2-propanol, ethanol and methanol with nicotinamide (NICAM) and 6-methyl nicotinic acid (6-MNA) were studied at various pHs using pulse radiolysis technique. It is found that ?-hydroxyalkyl radicals react with NICAM and 6-MNA at pHs when nitrogen is in the protonated state. In these reactions, radical adducts of NICAM/6-MNA with ?-hydroxyalkyl radicals are formed which have absorption maxima at about 340–350 nm which subsequently decay to give pyridinyl type of radicals of NICAM and 6-MNA having ?max at 410 nm. Rate constants for the reactions of (CH3)2C·OH, CH3C·HOH and ·CH2OH radicals with NICAM and 6-MNA were found to have linear dependence on reduction potentials of corresponding ?-hydroxyalkyl radicals. Adducts formed in the reactions of CH3C·HOH and ·CH2OH radicals with both NICAM and 6-MNA decayed slowly compared to the decay of adduct formed in reactions with (CH3)2C·OH radicals. - Highlights: ? Adduct formation in the reactions of ?-hydroxyalkyl radicals with nicotinamide and 6-methyl nicotinic acid was studied by pulse radiolysis technique. ? Adducts undergo decay to give pyridinyl type of radicals of nicotinamide and 6-methyl nicotinic acid. ? Linear dependence of adduct formation rate constants on reduction potential of reducion potential of reducing radicals is seen.

38

Characterization of the hyperline of D1/D0 conical intersections between the maleic acid and fumaric acid anion radicals  

International Nuclear Information System (INIS)

The cation and anion radicals of symmetrical 1,2-disubstituted ethylenes are expected to have a symmetry-allowed conical intersection (CI) between the ground doublet state (D0) and the lowest excited doublet state (D1) near a 90 deg.-twisted geometry. By the complete active space self-consistent field method, we characterized the hyperline formed by D1/D0 CIs between the anion radicals of maleic acid (cis) and fumaric acid (trans). An implication of the results for the known one-way cis?trans photoisomerization of the maleic acid anion radical and other related ion radicals is presented

39

EPR study of gamma induced radicals in amino and iminodiacetic acid derivatives  

Energy Technology Data Exchange (ETDEWEB)

In this study, electron paramagnetic resonance spectroscopy was used to investigate free radicals formed in gamma irradiated L-glutamine hydrochloride, iminodiacetic acid hydrochloride and N-(2-hydroxyethyl) iminodiacetic acid powders. The free radicals produced in L-glutamine hydrochloride powders were attributed to the CH{sub 2}CHCOOH radical; and those in iminodiacetic acid hydrochloride and N-(2-hydroxyethyl) iminodiacetic acid powders to the HNCHCH{sub 2}(CO OH){sub 2} and HOCH{sub 2}CH{sub 2}NCHCH{sub 2}(CO OH){sub 2}, respectively. The g-values of the radicals and the hyperfine structure constants of the free electron with the environmental protons and {sup 14}N nucleus were determined. The samples were not displayed before they were not irradiated. The free radicals were found stable at room temperature for more than six months. Some spectroscopic properties and suggestions concerning possible structure of the radicals are discussed in this paper. (author)

Aydin, Murat [Adiyaman University (Turkey). Faculty of Education; Baskan, M. Halim [Dicle University, Diyarbakir (Turkey). Faculty of Education; Osmanoglu, Y. Emre [Dicle University, Diyarbakir (Turkey). Inst. of Science

2009-09-15

40

Phenylpropanoid acid esters from Korean propolis and their antioxidant activities.  

Science.gov (United States)

Ten phenylpropanoic acid esters were isolated from an ethanolic extract of Korean propolis. Their structures were elucidated by spectroscopic methods including NMR and ESI-MS. Caffeic acid esters with catechol moiety exhibited significant ABTS and DPPH radical scavenging activity and protective effect against DNA damage by a Fenton reaction. PMID:24928402

Lee, In-Kyoung; Han, Myung-Suk; Kim, Dae-Won; Yun, Bong-Sik

2014-08-01

41

Enantioselective radical reactions. Evaluation of nitrogen protecting groups in the synthesis of beta-amino acids.  

Science.gov (United States)

We have investigated the effect of nitrogen protecting groups in radical addition trapping experiments leading to beta(2)-amino acids. Of the three N-protecting groups examined, the phthalimido group was optimal with respect to both yields and enantioselectivity. Additionally, radical additions to more complex acrylates were also investigated, which provided access to functionalized beta(2)-amino acids in modest selectivity. PMID:16799704

Sibi, Mukund P; Patil, Kalyani

2006-02-20

42

Enantioselective radical reactions. Evaluation of nitrogen protecting groups in the synthesis of ?2-amino acids  

Science.gov (United States)

We have investigated the effect of nitrogen protecting groups in radical addition trapping experiments leading to ?2-amino acids. Of the three N-protecting groups examined, the phthalimido group was optimal with respect to both yields and enantioselectivity. Additionally, radical additions to more complex acrylates were also investigated, which provided access to functionalized ?2-amino acids in modest selectivity. PMID:16799704

Sibi, Mukund P.; Patil, Kalyani

2006-01-01

43

Enantioselective radical reactions. Evaluation of nitrogen protecting groups in the synthesis of ?2-amino acids  

OpenAIRE

We have investigated the effect of nitrogen protecting groups in radical addition trapping experiments leading to ?2-amino acids. Of the three N-protecting groups examined, the phthalimido group was optimal with respect to both yields and enantioselectivity. Additionally, radical additions to more complex acrylates were also investigated, which provided access to functionalized ?2-amino acids in modest selectivity.

Sibi, Mukund P.; Patil, Kalyani

2006-01-01

44

Reaction of azide radicals with amino acids and proteins  

International Nuclear Information System (INIS)

This study showed that the azide radical N3 reacted selectively with amino acids in neutral solution preferentially with tryptophan (k(N3 + TrpH) = 4.1 x 109 dm3 mol-1s-1) and in alkaline solution also with cysteine and tyrosine (k(N3 + CyS-) = 2.7 x 109 dm3 mol-1s-1 and k(N3 + TyrO-) = 3.6 x 109 dm3 mol-1s-1). Oxidation of the enzyme yADH by N3 involved primary attacks mainly at tryptophan residues, and subsequent slow secondary reactions. N3-induced inactivation of yADH is likely to occur upon oxidation of tryptophan residues in the substrate binding pocket (58-TrpH and 93-TrpH) since the substrate ethanol, although unreactive with N3 protected yADH and since elADH, which does not contain tryptophan in the substrate pocket, was comparatively resistant against N3-attack. N3 exhibited low reactivity with nucleic acid derivatives and it was inert towards aliphatic compounds such as methanol and sodium dodecysulphate. (author)

45

Mechanism and kinetics in reactions of caffeic acid with radicals by pulse radiolysis and calculation  

International Nuclear Information System (INIS)

The interaction of caffeic acid with eaq-, (CH3)2(OH) CCH2·, CO2·-, H·, ·OH and N3· radicals were studied by ?-, pulse radiolysis and molecular orbital calculation. UV-visible spectra of electron/·OH adducts, semi-quinone radicals of caffeic ions, and the stable products from the reactions were derived. The rate constants were determined. The attacked sites and the most favorable structures of the transient radicals were predicted. Reaction mechanisms were proposed. (author)

46

Mechanism and kinetic of caffeic acid in reactions with radicals by pulse radiolysis and calculation  

International Nuclear Information System (INIS)

The interaction of caffeic acid with eaq-, (CH3)2(OH)CCH2; CO2, H, OH and N3 radicals were studied by ?-, pulse radiolysis and molecular orbital calculation. The rate constants were determined. UV-visible spectra of electron/OH adducts, semi-quinone radicals of caffeic ions, and the stable products from the reactions were derived. The attacked sites and the most favorable structures of the transient radicals were predicted. Reaction mechanisms were proposed. (author)

47

ANTIOXIDANT PROPERTIES OF LIGNANS AND FERULIC ACID FROM THE RESINOUS EXUDATE OF LARREA NITIDA  

Directory of Open Access Journals (Sweden)

Full Text Available From the resinous exudate of twigs end leaves of Larrea nitida, two lignans nor isoguaiacine 1 and meso-nor-dihydroguaiaretic acid 2 and ferulic acid 3 were isolated. The antioxidant activities of resin and pure compounds were assesed by bleaching of the ABTS derived radical-cation

RENÉ TORRES

2003-09-01

48

ANTIOXIDANT PROPERTIES OF LIGNANS AND FERULIC ACID FROM THE RESINOUS EXUDATE OF LARREA NITIDA  

OpenAIRE

From the resinous exudate of twigs end leaves of Larrea nitida, two lignans nor isoguaiacine 1 and meso-nor-dihydroguaiaretic acid 2 and ferulic acid 3 were isolated. The antioxidant activities of resin and pure compounds were assesed by bleaching of the ABTS derived radical-cation

RENÉ TORRES; FRANCISCO URBINA; CLAUDIA MORALES; BRENDA MODAK; FRANCO DELLE MONACHE

2003-01-01

49

ANTIOXIDANT PROPERTIES OF LIGNANS AND FERULIC ACID FROM THE RESINOUS EXUDATE OF LARREA NITIDA  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in english From the resinous exudate of twigs end leaves of Larrea nitida, two lignans nor isoguaiacine 1 and meso-nor-dihydroguaiaretic acid 2 and ferulic acid 3 were isolated. The antioxidant activities of resin and pure compounds were assesed by bleaching of the ABTS derived radical-cation [...

RENÉ, TORRES; FRANCISCO, URBINA; CLAUDIA, MORALES; BRENDA, MODAK; FRANCO DELLE, MONACHE.

2003-09-01

50

Localization and quantification of carbon-centered radicals on any amino acid of a protein  

International Nuclear Information System (INIS)

A general strategy to localize and quantify carbon-centered radicals within proteins is described. The methodology was first exemplified on amino acids and then on a peptide. This method is applicable to any protein system regardless of size, and the site of hydrogen abstraction by OH radical on all residues within proteins is easily and accurately detected. (authors)

51

Free-proton range ENDOR study of the inhomogeneous radical distribution in irradiated succinic acid  

International Nuclear Information System (INIS)

Free-proton range ENDOR signals were studied in the case of an x-ray irradiated polycrystalline sample of succinic acid. The line shape of the out-of-phase signal, which is believed to arise from the radical cluster with the lowest radical density, was found to be strongly deformed under an intense microwave field

52

Hydroxyl radical modify amino acids and prevent E. coli growth  

International Nuclear Information System (INIS)

The authors report that hydroxyl radical (/sup ./OH) damage to amino acids (AA) affects their incorporation into E. coli proteins. Modification of AA (Try, Trp, Met, Cys, His, Lys, Asn, Gln) by /sup ./OH was achieved by exposure to 60Co radiation (1-100 krads at 600 rads/min) in N2O saturated water. Following exposure to /sup ./OH, the modified AA were added to suspensions of 8 AA requiring E. coli mutants in M9 medium + glucose. Mutants incubated with the /sup ./OH modified AA underwent less growth than those incubated with unmodified AA; with a declining exponential relationship between /sup ./OH exposure of AA and cell growth. The sensitivity of each AA to modification by /sup ./OH was as follows: Tyr > Trp > Met > Cys > His > Lys > Asn > Gln. Essentially the same pattern was observed for inhibition of mutant growth, which was proportional to the concentration of remaining unmodified (i.e. native) AA. Furthermore, cell growth was restored to normal levels by replenishment of native AA. When AA were irradiated at 50?M and then diluted to concentrations expected to support exponential growth (different for each AA) the radiation doses at which mutant growth was inhibited by 63% were as follows (in krad): Tyr 41, Trp 48, Met 53, Cys 56, His 57, Lys 68, Asn 80, Gln 116. /sup ./OH-modified 3H-Trp was not a substrate for protein synthesis in Trp requiring mutants but was taken up by the cells. Modified Trp was also not incorporated in cell-free synthesis experiments. No toxicity was observed when wild type E. coli, in M9 medium + glucose, were supplemented with any of the/sup ./OH-modified AA. Thus /sup ./OH-modified AA do not support E. coli growth

53

Measurement of antioxidant activity with trifluoperazine dihydrochloride radical cation  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english A novel, rapid and cost-effective trifluoperazine dihydrochloride (TFPH) decolorization assay is described for the screening of antioxidant activity. A chromogenic reaction between TFPH and potassium persulfate at low pH produces an orange-red radical cation with maximum absorption at 502 nm in its [...] first-order derivative spectrum. TFPH was dissolved in distilled water to give a 100 mM solution. The TFPH radical cation solution was made by reacting 0.5 mL of the solution with K2S2O8 (final concentration: 0.1 mM) and diluting to 100 mL with 4 M H2SO4 solution. A linear inhibition of color production was observed with linearly increasing amounts of antioxidants, with correlation coefficients (R²) ranging from 0.999 to 0.983. The antioxidant capacity of standard solutions of an antioxidant was evaluated by comparing with the inhibition curve using Trolox as the standard. Comparison of antioxidant capacity determined with this newly developed TFPH assay and with the well-known 2,2'-azinobis-[3-ethylbenzthiazoline-6-sulfonic acid] (ABTS)-persulfate decolorization assay indicated the efficacy and sensitivity of the procedure. The proposed assay is less expensive (costs about US$4 per 100 assays) and requires only 20 min for preparation of radical cation solution in comparison with ABTS assay, in which almost 12-16 h are required for preparation of a stable ABTS radical cation solution. The present assay has the advantage over ABTS assay that it can be used to measure the antioxidant activity of the samples, which are naturally found at a pH as low as 1, because the radical cation itself has been stabilized at low pH.

M.N., Asghar; I.U., Khan.

2008-06-01

54

Measurement of antioxidant activity with trifluoperazine dihydrochloride radical cation  

Directory of Open Access Journals (Sweden)

Full Text Available A novel, rapid and cost-effective trifluoperazine dihydrochloride (TFPH decolorization assay is described for the screening of antioxidant activity. A chromogenic reaction between TFPH and potassium persulfate at low pH produces an orange-red radical cation with maximum absorption at 502 nm in its first-order derivative spectrum. TFPH was dissolved in distilled water to give a 100 mM solution. The TFPH radical cation solution was made by reacting 0.5 mL of the solution with K2S2O8 (final concentration: 0.1 mM and diluting to 100 mL with 4 M H2SO4 solution. A linear inhibition of color production was observed with linearly increasing amounts of antioxidants, with correlation coefficients (R² ranging from 0.999 to 0.983. The antioxidant capacity of standard solutions of an antioxidant was evaluated by comparing with the inhibition curve using Trolox as the standard. Comparison of antioxidant capacity determined with this newly developed TFPH assay and with the well-known 2,2'-azinobis-[3-ethylbenzthiazoline-6-sulfonic acid] (ABTS-persulfate decolorization assay indicated the efficacy and sensitivity of the procedure. The proposed assay is less expensive (costs about US$4 per 100 assays and requires only 20 min for preparation of radical cation solution in comparison with ABTS assay, in which almost 12-16 h are required for preparation of a stable ABTS radical cation solution. The present assay has the advantage over ABTS assay that it can be used to measure the antioxidant activity of the samples, which are naturally found at a pH as low as 1, because the radical cation itself has been stabilized at low pH.

M.N. Asghar

2008-06-01

55

Mechanism and kinetics in reactions of caffeic acid with radicals by pulse radiolysis and calculation  

Energy Technology Data Exchange (ETDEWEB)

Molecular orbital calculation and pulse radiolysis method are combined in the studies of interaction of caffeic acid with e{sub aq}{sup -}, (CH{sub 3}){sub 2}(OH)CCH{sub 2}{sup .}, CO{sub 2}{sup .-}, H{sup .}, {center_dot}OH and N{sub 3}{sup .} radicals. Reaction rate constants, UV-visible spectra of electron|{center_dot}OH adducts, semiquinone radicals of caffeic ions, and the resulted stable products were derived from experimental data. While the radical attacked sites and the most favorable structures of the transient radicals were predicted by calculation. Reaction mechanisms were proposed. (author)

Li Xifeng; Cai Zhongli; Katsumura, Yosuke [Tokyo Univ., Tokai, Ibaraki (Japan). Nuclear Engineering Research Lab

2000-07-01

56

Homogentisic acid autoxidation and oxygen radical generation: implications for the etiology of alkaptonuric arthritis.  

Science.gov (United States)

The metabolic disorder, alkaptonuria, is distinguished by elevated serum levels of 2,5-dihydroxyphenylacetic acid (homogentisic acid), pigmentation of cartilage and connective tissue and, ultimately, the development of inflammatory arthritis. Oxygen radical generation during homogentisic acid autoxidation was characterized in vitro to assess the likelihood that oxygen radicals act as molecular agents of alkaptonuric arthritis in vivo. For homogentisic acid autoxidized at physiological pH and above, yielding superoxide (O2-)2 and hydrogen peroxide (H2O2), the homogentisic acid autoxidation rate was oxygen dependent, proportional to homogentisic acid concentration, temperature dependent and pH dependent. Formation of the oxidized product, benzoquinoneacetic acid was inhibited by the reducing agents, NADH, reduced glutathione, and ascorbic acid and accelerated by SOD and manganese-pyrophosphate. Manganese stimulated autoxidation was suppressed by diethylenetriaminepentaacetic acid (DTPA). Homogentisic acid autoxidation stimulated a rapid cooxidation of ascorbic acid at pH 7.45. Hydrogen peroxide was among the products of cooxidation. The combination of homogentisic acid and Fe3+-EDTA stimulated hydroxyl radical (OH.) formation estimated by salicylate hydroxylation. Ferric iron was required for the reaction and Fe3+-EDTA was a better catalyst than either free Fe3+ or Fe3+-DTPA. SOD accelerated OH. production by homogentisic acid as did H2O2, and catalase reversed much of the stimulation by SOD. Catalase alone, and the hydroxyl radical scavengers, thiourea and sodium formate, suppressed salicylate hydroxylation. Homogentisic acid and Fe3+-EDTA also stimulated the degradation of hyaluronic acid, the chief viscous element of synovial fluid. Hyaluronic acid depolymerization was time dependent and proportional to the homogentisic acid concentration up to 100 microM. The level of degradation observed was comparable to that obtained with ascorbic acid at equivalent concentrations. The hydroxyl radical was an active intermediate in depolymerization. Thus, catalase and the hydroxyl radical scavengers, thiourea and dimethyl sulfoxide, almost completely suppressed the depolymerization reaction. The ability of homogentisic acid to generate O2-, H2O2 and OH. through autoxidation and the degradation of hyaluronic acid by homogentisic acid-mediated by OH. production suggests that oxygen radicals play a significant role in the etiology of alkaptonuric arthritis. PMID:3121448

Martin, J P; Batkoff, B

1987-01-01

57

Reactions of reducing and oxidizing radicals with caffeic acid: a pulse radiolysis and theoretical study  

International Nuclear Information System (INIS)

Molecular calculations coupled with pulse radiolysis studies are performed to understand the reactions of radicals with caffeic acid. From molecular calculation, we find that eaq- and ·OH tend to form adducts with caffeic acid, while N3· tends to abstract H from 4-hydroxyl group in benzene ring, generating a semi-quinoid radical. Based on comparison of the heat of formation, the most favorable radical attack sites and the most stable radical structures are predicted. The calculation results suggest that the stability of the electron adducts 9, (6.0±0.4)x107 and (2.0±0.2)x107 M-1 s-1, respectively), determined by pulse radiolysis. Molecular calculations seem to be a powerful tool to predict the stability and structures of transient radicals. (author)

58

Radical Scavenging Capacity of Methanolic Phillyrea latifolia L. Extract: Anthocyanin and Phenolic Acids Composition of Fruits  

OpenAIRE

Radical scavenging capacity of a crude methanolic extract from the fruits of Phillyrea latifolia L., commonly known as green olive tree or mock privet, was investigated with reference to anthocyanin standards, as flavonoids, and phenolic acid standards, as phenylpropanoids. Characterization with high performance liquid chromatography-diode array detection (HPLC-DAD) indicated the presence of keracyanin, kuromanin, cyanidin, ferulic acid, caffeic acid and rosmarinic acid at amounts of 289.1, 9...

Naciye Erkan; Erol Ayranci

2013-01-01

59

Pulse radiolysis studies on reactions of ?-hydroxyalkyl radicals with nicotinamide and 6-methyl nicotinic acid  

Science.gov (United States)

Reactions of ?-hydroxyalkyl radicals derived from 2-propanol, ethanol and methanol with nicotinamide (NICAM) and 6-methyl nicotinic acid (6-MNA) were studied at various pHs using pulse radiolysis technique. It is found that ?-hydroxyalkyl radicals react with NICAM and 6-MNA at pHs when nitrogen is in the protonated state. In these reactions, radical adducts of NICAM/6-MNA with ?-hydroxyalkyl radicals are formed which have absorption maxima at about 340-350 nm which subsequently decay to give pyridinyl type of radicals of NICAM and 6-MNA having ?max at 410 nm. Rate constants for the reactions of (CH3)2Crad OH, CH3Crad HOH and rad CH2OH radicals with NICAM and 6-MNA were found to have linear dependence on reduction potentials of corresponding ?-hydroxyalkyl radicals. Adducts formed in the reactions of CH3Crad HOH and rad CH2OH radicals with both NICAM and 6-MNA decayed slowly compared to the decay of adduct formed in reactions with (CH3)2Crad OH radicals.

Dhiman, S. B.; Naik, D. B.

2012-06-01

60

Lanthanide Lewis acid-mediated enantioselective conjugate radical additions.  

Science.gov (United States)

[reaction: see text] Lanthanide triflates along with proline-derived ligands have been found to be efficient catalysts for enantioselective conjugate addition of nucleophilic radicals to enoates. N-Acyl oxazolidinones, when used as achiral additives, gave meaningful enhancements in the ees for the product. PMID:12182591

Sibi, Mukund P; Manyem, Shankar

2002-08-22

61

E.S.R. of spin-trapped radicals in ?-irradiated polycrystalline amino acids. Chromatographic separation of radicals  

International Nuclear Information System (INIS)

The free radicals produced by ?-radiolysis of polycrystalline amino acids (L-valine, L-leucine, L-isoleucine and L-proline) at room temperature in the absence of air were investigated by spin trapping with 2-methyl-2-nitrosopropane (MNP). The spin adducts produced by dissolving the irradiated solids in aqueous MNP solutions were separated by high-performance liquid chromatography and then identified by e.s.r. Deamination (ring-opening reaction for L-proline) was observed for all amino acids. For L-valine and L-leucine, H-abstraction from the tertiary carbon in the side chains occurred. For isoleucine, H-abstractions for the ?-carbon of the amino acid and from a non-terminal carbon in the side chain were found. (author)

62

Study of the structure of free radicals in gamma irradiated amino acid derivatives  

Energy Technology Data Exchange (ETDEWEB)

Electron paramagnetic resonance spectroscopy has been used for the study of the free radicals produced in the powders of L-arginine monohydrochloride, ala-ala and DL-{beta}-leucine gamma-irradiated at room temperature. The structures of the radicals formed in compounds were determined as NH{sub 2}(NH)NHCHCH{sub 2}CH{sub 2}CH(NH{sub 2})CO OH, CH{sub 3}CHCOOH and (CH{sub 3}){sub 2} CCH(NH{sub 2})CH{sub 2}COOH respectively. The paramagnetic species were found to be stable at room temperature more than three months. It was determined that unpaired electron interacted with nearby protons and {sup 14}N nucleus in these radicals. The g values of the radicals and the hyperfine structure constants of the free electron were also measured. These results were compared with the earlier studies in amino acid and derivatives radicals and discussed. (author)

Aydin, Murat, E-mail: maydin@adiyaman.edu.t [Adyyaman University, Adyaman (Turkey). Faculty of Education

2010-12-15

63

Study of the structure of free radicals in gamma irradiated amino acid derivatives  

International Nuclear Information System (INIS)

Electron paramagnetic resonance spectroscopy has been used for the study of the free radicals produced in the powders of L-arginine monohydrochloride, ala-ala and DL-?-leucine gamma-irradiated at room temperature. The structures of the radicals formed in compounds were determined as NH2(NH)NHCHCH2CH2CH(NH2)CO OH, CH3CHCOOH and (CH3)2 CCH(NH2)CH2COOH respectively. The paramagnetic species were found to be stable at room temperature more than three months. It was determined that unpaired electron interacted with nearby protons and 14N nucleus in these radicals. The g values of the radicals and the hyperfine structure constants of the free electron were also measured. These results were compared with the earlier studies in amino acid and derivatives radicals and discussed. (author)

64

Identification of free radicals induced by gamma irradiation in amino acid derivatives  

International Nuclear Information System (INIS)

Powders of N-acetyl-L-leucine and N-methyl-L-glutamic acid were gamma irradiated and the free radicals formed were investigated at room temperature by electron paramagnetic resonance technique. The free radicals formed in compounds were attributed to the (CH3)2CCH CH2CH(NHCOCH3)COOH and HOOCCH2CH2C(NHCH3)COOH radicals respectively. Both radicals are very stable and we could observe them for five months without almost intensity diminution at room temperature. The g values of the radicals and the hyperfine structure constants of the free electron with nearby protons and 14N nucleus were determined. The results were found to be in good agreement with the existing literature data. (author)

65

Identification of free radicals induced by gamma irradiation in amino acid derivatives  

Energy Technology Data Exchange (ETDEWEB)

Powders of N-acetyl-L-leucine and N-methyl-L-glutamic acid were gamma irradiated and the free radicals formed were investigated at room temperature by electron paramagnetic resonance technique. The free radicals formed in compounds were attributed to the (CH{sub 3}){sub 2}CCH CH{sub 2}CH(NHCOCH{sub 3})COOH and HOOCCH{sub 2}CH{sub 2}C(NHCH{sub 3})COOH radicals respectively. Both radicals are very stable and we could observe them for five months without almost intensity diminution at room temperature. The g values of the radicals and the hyperfine structure constants of the free electron with nearby protons and {sup 14}N nucleus were determined. The results were found to be in good agreement with the existing literature data. (author)

Aydin, Murat, E-mail: muraydinat@gmail.co [Adiyaman University (Turkey). Faculty of Education

2010-09-15

66

Identification of free radicals induced by gamma irradiation in amino acid derivatives  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Powders of N- acetyl- L- leucine and N- methyl- L- glutamic acid were gamma irradiated and the free radicals formed were investigated at room temperature by electron paramagnetic resonance technique. The free radicals formed in compounds were attributed to the (CH3)2CCH2CH(NHCOCH3)COOH and HOOCCH2CH [...] 2C (NHCH3)COOH radicals respectively. Both radicals are very stable and we could observe them for five months without almost intensity diminution at room temperature. The g values of the radicals and the hyperfine structure constants of the free electron with nearby protons and 14N nucleus were determined. The results were found to be in good agreement with the existing literature data.

Murat, Aydin.

2010-09-01

67

Study of the structure of free radicals in gamma: irradiated amino acid derivatives  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Electron paramagnetic resonance spectroscopy has been used for the study of the free radicals produced in the powders of L-arginine monohydrochloride, ala-ala and DL-?-leucine gamma-irradiated at room temperature. The structures of the radicals formed in compounds were determined as NH2(NH)NHCHCH2CH [...] 2CH(NH2)COOH, CH3CHCOOH and (CH3)2C CH(NH2)CH2COOH respectively. The paramagnetic species were found to be stable at room temperature more than three months. It was determined that unpaired electron interacted with nearby protons and 14N nucleus in these radicals. The g values of the radicals and the hyperfine structure constants of the free electron were also measured. These results were compared with the earlier studies in amino acid and derivatives radicals and discussed.

Murat, Aydin.

2010-12-01

68

Tetrahydrofuran alpha-azido esters: Precursors of anomeric alpha-amino acid monomers via radical bromination  

OpenAIRE

A general route for the synthesis of tetrahydrofuran ?-azido esters as the equivalent of monomeric furanose anomeric ?-amino acids is described. Highly selective radical bromination of a range of suitably protected carbohydrate C-glycosyl derivatives affords bromo-esters which undergo efficient displacement by azide to give anomeric ?-amino acid derivatives.

Smith, Md; Long, Dd; Martin, A.; Campbell, N.; Bleriot, Y.; Fleet, Gwj

1999-01-01

69

E.s.r. of spin-trapped radicals in ?-irradiated polycrystalline amino acids, N-acetyl amino acids and dipeptides  

International Nuclear Information System (INIS)

The radicals produced in several polycrystalline amino acids, N-acetyl amino acids and dipeptides by ?-radiolysis at room temperature were investigated by spin-trapping. After irradiation in the solid state, the samples were dissolved in aqueous solutions of t-nitrosobutane and the trapped radicals identified by e.s.r. For ?-amino acids, deamination radicals were found, and in some cases H-abstraction radicals were also observed. No decarboxylation radicals could be detected. For N-acetyl amino acids, except for N-acetylglycine, the major radical was the decarboxylation radical. For N-acetylglycine the H-abstraction radical from the glycine residue was observed. For dipeptides of the type x-glycine, the radical formed by removal of H from the ?-carbon of the carboxyl-terminal residue was always spin-trapped. Some primary deamination radicals and minor amounts of decarboxylation radicals could also be observed. For dipeptides of the type x-alanine, glycine-x and alanine-x, the decarboxylation radical was always the major spin-trapped radical. Some primary and secondary deamination radicals were also detected. (author)

70

OH-radical induced degradation of hydroxybenzoic- and hydroxycinnamic acids and formation of aromatic products—A gamma radiolysis study  

Science.gov (United States)

The OH-radical induced degradation of hydroxybenzoic acids (HBA), hydroxycinnamic acids (HCiA) and methoxylated derivatives, as well as of chlorogenic acid and rosmarinic acid was studied by gamma radiolysis in aerated aqueous solutions. Primary aromatic products resulting from an OH-radical attachment to the ring (hydroxylation), to the position occupied by the methoxyl group (replacement -OCH 3 by -OH) as well as to the propenoic acid side chain of the cinnamic acids (benzaldehyde formations) were analysed by HPLC-UV and LC-ESI-MS. A comparison of the extent of these processes is given for 3,4-dihydroxybenzoic acid, vanillic acid, isovanillic acid, syringic acid, cinnamic acid, 4-hydroxycinnamic acid, caffeic acid, ferulic acid, isoferulic acid, chlorogenic acid, and rosmarinic acid. For all cinnamic acids and derivatives benzaldehydes were significant oxidation products. With the release of caffeic acid from chlorogenic acid the cleavage of a phenolic glycoside could be demonstrated. Reaction mechanisms are discussed.

Krimmel, Birgit; Swoboda, Friederike; Solar, Sonja; Reznicek, Gottfried

2010-12-01

71

OH-radical induced degradation of hydroxybenzoic- and hydroxycinnamic acids and formation of aromatic products-A gamma radiolysis study  

Energy Technology Data Exchange (ETDEWEB)

The OH-radical induced degradation of hydroxybenzoic acids (HBA), hydroxycinnamic acids (HCiA) and methoxylated derivatives, as well as of chlorogenic acid and rosmarinic acid was studied by gamma radiolysis in aerated aqueous solutions. Primary aromatic products resulting from an OH-radical attachment to the ring (hydroxylation), to the position occupied by the methoxyl group (replacement -OCH{sub 3} by -OH) as well as to the propenoic acid side chain of the cinnamic acids (benzaldehyde formations) were analysed by HPLC-UV and LC-ESI-MS. A comparison of the extent of these processes is given for 3,4-dihydroxybenzoic acid, vanillic acid, isovanillic acid, syringic acid, cinnamic acid, 4-hydroxycinnamic acid, caffeic acid, ferulic acid, isoferulic acid, chlorogenic acid, and rosmarinic acid. For all cinnamic acids and derivatives benzaldehydes were significant oxidation products. With the release of caffeic acid from chlorogenic acid the cleavage of a phenolic glycoside could be demonstrated. Reaction mechanisms are discussed.

Krimmel, Birgit; Swoboda, Friederike [University of Vienna, Department of Nutritional Sciences, Section Radiation Biology (Austria); Solar, Sonja, E-mail: sonja.solar@univie.ac.a [University of Vienna, Department of Nutritional Sciences, Section Radiation Biology (Austria); Reznicek, Gottfried [Department of Pharmacognosy, Althanstrasse 14, A-1090 Vienna (Austria)

2010-12-15

72

OH-radical induced degradation of hydroxybenzoic- and hydroxycinnamic acids and formation of aromatic products-A gamma radiolysis study  

International Nuclear Information System (INIS)

The OH-radical induced degradation of hydroxybenzoic acids (HBA), hydroxycinnamic acids (HCiA) and methoxylated derivatives, as well as of chlorogenic acid and rosmarinic acid was studied by gamma radiolysis in aerated aqueous solutions. Primary aromatic products resulting from an OH-radical attachment to the ring (hydroxylation), to the position occupied by the methoxyl group (replacement -OCH3 by -OH) as well as to the propenoic acid side chain of the cinnamic acids (benzaldehyde formations) were analysed by HPLC-UV and LC-ESI-MS. A comparison of the extent of these processes is given for 3,4-dihydroxybenzoic acid, vanillic acid, isovanillic acid, syringic acid, cinnamic acid, 4-hydroxycinnamic acid, caffeic acid, ferulic acid, isoferulic acid, chlorogenic acid, and rosmarinic acid. For all cinnamic acids and derivatives benzaldehydes were significant oxidation products. With the release of caffeic acid from chlorogenic acid the cleavage of a phenolic glycoside could be demonstrated. Reaction mechanisms are discussed.

73

Biotechnological treatment for colorless denim and textil wastewater treatment with laccase and ABTS / Tratamiento biotecnológico para la decoloración de la mezclilla y efluentes textiles empleando lacasa y ABTS  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: English Abstract in spanish El sistema ABTS (ácido 2,2'-[3-etil benzotiazolin-6-sulfónico])-lacasa se empleó para decolorar tanto tela de mezclilla como una solución preparada de índigo. Después del tratamiento, la mezclilla adquirió un aspecto de usada, sin que las fibras mostraran evidencia de daño, mientras que la solución [...] de índigo se decoloró. Adicionalmente, el análisis de la biodegradación de los desechos acuosos de la decoloración de la mezclilla y la solución decolorada control de índigo mostraron que, en ambos casos el agua residual fue fácilmente biodegradada tanto aeróbica como anaeróbicamente, mientras que la solución control de índigo requirió de 5 días para biodegradarse aeróbicamente y no sufrió ningún cambio en el sistema anaeróbico. El ABTS oxidado ó la lacasa por sí solos no decoloraron la mezclilla ni la solución de índigo bajo las mismas condiciones experimentales en que se empleó la combinación de ambos ABTS-lacasa. Esto se explica porque, durante la reacción de decoloración, el mediador se recicla varias veces entre la enzima y el colorante, de tal forma que en 30 minutos, una molécula de ABTS oxida 800 moléculas de índigo, además la velocidad de decoloración fue dos órdenes de magnitud mayor que la velocidad cuando se empleó el ABTS ó la enzima en forma individual. Abstract in english The ABTS (2,2'-[3-etil benzotiazolin-6-sulphonic]acid)-Laccase system was applied for discoloration of both commercial denim fabric and a synthetic indigo solution. After treatment, the denim fabric looked like an aged one, although fibers did not exhibit any damage and the synthetic indigo solution [...] was bleached. Additionally, an analysis of both the denim discoloration residual water and the synthetic indigo solution biodegradation, showed that in the two cases the residual water was easily biodegraded in either an aerobic or anaerobic mode, while the control indigo solution required 5 days to be biodegraded in an aerobic mode, and it became unaltered in anaerobic mode. The oxidized ABTS or the laccase could not bleach denim or the synthetic indigo solution in the same experimental conditions as when using the system ABTS-laccase. This is explained considering that, during this process, as when using the mediator recycles several times between the laccase and the indigo, in such way that in a 30 min period, one molecule of ABTS oxidized 800 indigo molecules; also, the observed discoloration rate was two orders of magnitude higher than the rates observed when either the oxidized mediator or the enzyme by itself were applied.

Myrna, SOLÍS-OBA; Javier, ALMENDÁRIZ; Gustavo, VINIEGRA-GONZÁLEZ.

2008-03-01

74

Free radical initiation in proteins and amino acids by ionizing and ultraviolet radiations and lipid oxidation. Part III: free radical transfer from oxidizing lipids  

International Nuclear Information System (INIS)

Parallels and similarities in chemical and functional damage to proteins by ionizing and uv radiations and oxidizing lipids have been recognized for some time. However, only recently have oxidizing lipids been shown directly by electron spin resonance to be radiomimetic also in their capacity for protein free radical production. Accordingly, this review is a detailed comparison of gamma-radiation, uv radiation, and lipid oxidation for what is presently known concerning (1) the specific modes of energy deposition and free radical formation, (2) the free radicals formed in proteins and amino acids, and (3) the typical damage correlating with these radicals

75

Electron spin resonance study of radiation-induced radicals in polycrystalline aromatic carboxylic acids containing a thioether group  

International Nuclear Information System (INIS)

Radicals and radical ions formed on ?-radiolysis of aromatic carboxylic acids containing a thioether group in the polycrystalline state at 77K and on subsequent warming over the temperature range of 95-293K were identified using the electron spin resonance technique. In all carboxylic acids studied, monomeric sulfur radical cations (X-S+-Y-COOH) and radical anions formed by an addition of an electron to the carboxyl group (X-S-Y-COOH)- were detected at 95K. On further warming over the 150-293K range various S-centered radicals (XS) and C-centered radicals were observed. The results are discussed in terms of the following competitive reaction pathways: fragmentation, decarboxylation, and deprotonation of the parental monomeric sulfur radical cations. Carbon dioxide was identified and quantified (G=0.2-3.5) in all carboxylic acids exposed to ?-radiation

76

Reactions of reducing and oxidizing radicals with caffeic acid: a pulse radiolysis and theoretical study  

Energy Technology Data Exchange (ETDEWEB)

Molecular calculations coupled with pulse radiolysis studies are performed to understand the reactions of radicals with caffeic acid. From molecular calculation, we find that e{sub aq}{sup -} and {center_dot}OH tend to form adducts with caffeic acid, while N{sub 3}{sup {center_dot}} tends to abstract H from 4-hydroxyl group in benzene ring, generating a semi-quinoid radical. Based on comparison of the heat of formation, the most favorable radical attack sites and the most stable radical structures are predicted. The calculation results suggest that the stability of the electron adducts radicals <{center_dot}OH adducts of caffeic ions, in good agreement with their experimental second-order decay rate constants (2k=(1.1{+-}0.2)x10{sup 9}, (6.0{+-}0.4)x10{sup 7} and (2.0{+-}0.2)x10{sup 7} M{sup -1} s{sup -1}, respectively), determined by pulse radiolysis. Molecular calculations seem to be a powerful tool to predict the stability and structures of transient radicals. (author)

Li Xifeng; Cai Zhongli; Katsumura, Yosuke E-mail: katsu@q.t.u-tokyo.ac.jp; Wu Guozhong; Muroya, Yusa

2001-07-01

77

Influence of different free radicals on scavenging potency of gallic acid.  

Science.gov (United States)

The M05-2X/6-311++G(d,p) and B3LYP-D2/6-311++G(d,p) models are used to evaluate scavenging potency of gallic acid. The hydrogen atom transfer (HAT), sequential proton loss electron transfer (SPLET), and single electron transfer followed by proton transfer (SET-PT) mechanisms of gallic acid with some radicals ((•)OO(-), (•)OH, and CH3OO(•)) were investigated using the corresponding thermodynamic quantities: bond dissociation enthalpy (BDE), ionization potential (IP), and proton affinity (PA). Namely, the ?HBDE, ?HIP, and ?HPA values of the corresponding reactions in some solvents (water, DMSO, pentylethanoate, and benzene) are investigated using an implicit solvation model (SMD). An approach based on the reactions enthalpies related to the examined mechanisms is applied. This approach shows that a thermodynamically favored mechanism depends on the polarity of reaction media and properties of free radical reactive species. The most acidic 4-OH group of gallic acid is the active site for radical inactivation. The results of this investigation indicate that the SPLET mechanism can be a favored reaction pathway for all three radicals in all solvents, except for (•)OH in the aqueous solution. In water, gallic acid can inactivate (•)OH by the HAT mechanism. PMID:24965934

?orovi?, Jelena; Markovi?, Jasmina M Dimitri?; Stepani?, Višnja; Begovi?, Nebojša; Ami?, Dragan; Markovi?, Zoran

2014-07-01

78

Kinetic observation of rapid electron transfer between thymine and thymidine anion radicals and caffeic acid. A pulse radiolysis study  

International Nuclear Information System (INIS)

Rapid electron transfer from thymine or thymidine anion radicals to caffeic acid with rate constant of 1 x 109 M-1s-1 was observed by pulse radiolysis, leading to the formation of anion radicals of caffeic acid which is characterized with absorption maximum at 360 nm. Caffeic acid has a higher one-electron reduction potential than the target molecule (thymine or thymidine) and acts as a electrophilic protector which prevent the target anion radical from its irreversible protonation at C6 leading to its 5-yl radical via fast electron transfer. The kinetic demonstrations have provided dynamic evidence of charge transfer protection mechanism

79

Kinetic observation of rapid electron transfer between thymine and thymidine anion radicals and caffeic acid: a pulse radiolysis study  

Energy Technology Data Exchange (ETDEWEB)

Rapid electron transfer from thymine or thymidine anion radicals to caffeic acid with rate constant of 1 x 10{sup 9} M{sup -1}s{sup -1} was observed by pulse radiolysis, leading to the formation of anion radicals of caffeic acid which is characterized with absorption maximum at 360nm. Caffeic acid has a higher one-electron reduction potential than the target molecule (thymine or thymidine) and acts as a electrophilic protector which prevent the target anion radical from its irreversible protonation at C6 leading to its 5-yl radical via fast electron transfer. The kinetic demonstrations have provided dynamic evidence of charge transfer protection mechanism. (author).

Zuo, Z.H.; Yao, S.D.; Lee, H.C.; Lin, W.Z.; Zhang, J.S.; Lin, N.Y. [Academia Sinica, Shanghai, SH (China). Shanghai Inst. of Nuclear Research

1995-03-01

80

Kinetic observation of rapid electron transfer between thymine and thymidine anion radicals and caffeic acid: a pulse radiolysis study  

International Nuclear Information System (INIS)

Rapid electron transfer from thymine or thymidine anion radicals to caffeic acid with rate constant of 1 x 109 M-1s-1 was observed by pulse radiolysis, leading to the formation of anion radicals of caffeic acid which is characterized with absorption maximum at 360nm. Caffeic acid has a higher one-electron reduction potential than the target molecule (thymine or thymidine) and acts as a electrophilic protector which prevent the target anion radical from its irreversible protonation at C6 leading to its 5-yl radical via fast electron transfer. The kinetic demonstrations have provided dynamic evidence of charge transfer protection mechanism. (author)

81

Radical Scavenging Capacity of Methanolic Phillyrea latifolia L. Extract: Anthocyanin and Phenolic Acids Composition of Fruits  

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Full Text Available Radical scavenging capacity of a crude methanolic extract from the fruits of Phillyrea latifolia L., commonly known as green olive tree or mock privet, was investigated with reference to anthocyanin standards, as flavonoids, and phenolic acid standards, as phenylpropanoids. Characterization with high performance liquid chromatography-diode array detection (HPLC-DAD indicated the presence of keracyanin, kuromanin, cyanidin, ferulic acid, caffeic acid and rosmarinic acid at amounts of 289.1, 90.4, 191.4, 225.2, 221.2 and 190.1 mg/100 g fresh weight (FW of fruits, respectively. Chlorogenic and p-coumaric acids were found to exist in lower amounts. Trolox equivalent antioxidant capacity (TEAC and IC50 values of the plant extract were found to be 1.8 mM Trolox equivalents (TE/g FW of fruits and 69.4 µg/mL, respectively, indicating the close radical scavenging activity of the extract to those of keracyanin and p-coumaric acid. The crude methanolic P. latifolia L. fruit extract was seen to be fairly potent in radical scavenging. Total phenolic content (TPC of the plant extract was found to be 1652.9 mg gallic acid equivalent (GAE/100 g FW of fruits.

Naciye Erkan

2013-01-01

82

Effect of Acid and Base Catalyzed Hydrolysis on the Yield of Phenolics and Antioxidant Activity of Extracts from Germinated Brown Rice (GBR  

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Full Text Available The influence of both acidic and basic hydrolysis on the yield, total phenolic content and antioxidative capacity of methanolic extract of germinated brown rice (GBR was studied. Total phenolic content (TPC, total flavonoid content (TFC, 2,2?-diphenyl-1-picrylhydrazyl (DPPH radical scavenging, 2,2?-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS radical cation scavenging, and ferric reducing antioxidant power (FRAP tests were used for the measurement of antioxidant ability. There was a significant difference (p < 0.05 in the TPC and DPPH radical scavenging assay results when comparing neutral with acidic and basic catalysed hydrolysis. The yield of the crude extract was slightly higher in acidic hydrolysis than in basic hydrolysis (p > 0.05. The TPC and TFC were highest in acidic hydrolysis. A significant correlation was observed between ABTS radical cation scavenging and FRAP. The antioxidant activity measured using DPPH radical scavenging assay showed high activity in acidic hydrolysis, while the ABTS radical cationscavenging activity and FRAP showed the highest values in basic hydrolysis. The samples were further evaluated using HPLC to determine the individual phenolic concentrations in different hydrolytic media contributing to the antioxidant effects. This study revealed that acidic and basic hydrolysis can improve the yield, phenolic content, and antioxidant activity of germinated brown rice.

Shahid Iqbal

2012-06-01

83

Kinetic observation of rapid electron transfer between thymine and thymidine anion radicals and caffeic acid. A pulse radiolysis study  

International Nuclear Information System (INIS)

Utilizing pulse radiolysis and kinetic spectrophotometric monitoring techniques, rapid electron transfer reaction from thymine and thymidine anion radicals to caffeic acid was observed respectively. Anion radicals of caffeic acid with absorption maximum at 360 nm have been generated via foregoing electron transfer reaction with rate constant of 1 x 109 mol-1Ls-1. Accordingly the subsequent protonation of thymine anion radicals should be prevented by the electrophilic protector. These kinetic demonstrations have provided direct evidence of charge transfer protection mechanism

84

Reactions of clofibric acid with oxidative and reductive radicals-Products, mechanisms, efficiency and toxic effects  

Science.gov (United States)

The degradation of clofibric acid induced by hydroxyl radical, hydrated electron and O2-•/HO2• reactive species was studied in aqueous solutions. Clofibric acid was decomposed more effectively by hydroxyl radical than by hydrated electron or O2-•/HO2•. Various hydroxylated, dechlorinated and fragmentation products have been identified and quantified. A new LC-MS method was developed based on 18O isotope labeling to follow the formation of hydroxylated derivatives of clofibric acid. Possible degradation pathways have been proposed. The overall degradation was monitored by determination of sum parameters like COD, TOC and AOX. It was found that the organic chlorine degrades very effectively prior to complete mineralization. After the treatment no toxic effect was found according to Vibrio fischeri tests. However, at early stages some of the reaction products were more harmful than clofibric acid.

Csay, Tamás; Rácz, Gergely; Salik, Ádám; Takács, Erzsébet; Wojnárovits, László

2014-09-01

85

Free radical damage of nucleic acids and their components. I. Direct absorption of energy  

International Nuclear Information System (INIS)

An attempt is made to summarize our present understanding of free radical formation and reactions when energy from ionizing radiations is deposited directly in nucleic acids. The scope of the discussion is limited to recent progress, with reference to older work only when needed for coherence

86

Search for oxygen-centered free radicals in the lipoxygenase/linoleic acid system  

International Nuclear Information System (INIS)

Studies of the oxygenation of linoleic acid by soybean lipoxygenase utilizing electron spin resonance spectroscopy and oxygen uptake have been undertaken. The spin trap, alpha-(4-pyridyl-1-oxide)-N-t-butylnitrone (4-POBN) was included in the lipoxygenase system to capture short-lived free radicals. Correlation of radical adduct formation rates with oxygen uptake studies indicated that the major portion of radical adduct formation occurred when the system was nearly anaerobic. Incubations containing [17O]oxygen with nuclear spin of 5/2 did not have additional ESR lines as would be expected if an oxygen-centered 4-POBN-lipid peroxyl radical adduct were formed indicating that the trapped radical must be reassigned as a carbon-centered species. To establish the presence of [17O2]oxygen in our incubations, a portion of the gas from the lipoxygenase/linoleate experiments was used to prepare the 4-POBN-superoxide radical adduct utilizing a superoxide producing microsomal/paraquat/NADPH system

87

Radical formation in the radiolysis of solid adipic acid by ?-rays and heavy ions  

International Nuclear Information System (INIS)

Radical formation in solid adipic acid irradiated with ?-rays, 175 MeV Ar8+, 220 MeV C5+, and 350 MeV Ne8+ ions was studied by ESR method. The radical yield for the ion irradiations (number of radicals per incident ion) is constant below a critical fluence of about 5 x 1010 ionscm-2 for the Ar ions, 1011 ionscm-2 for the C and the Ne ions. Above the critical fluence, the yield decreases with increasing ion fluence. The G-value of the radical formation was obtained from the constant yield at the low fluences: 5.6 for the C ion, 2.3 for the Ne ion, and 0.65 for the Ar ion. The G-value for the Ar ion is about 1/(10) of the value of 6.3 for ?-irradiation. The larger effect of radiation quality for adipic acid than the effect for alanine is ascribed to the difference in the dose-yield relationship of the radical formations. (orig.)

88

Turning on ribonucleotide reductase by light-initiated amino acid radical generation  

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Ribonucleotide reductases (RNRs) catalyze the conversion of nucleotides to deoxynucleotides in all organisms, providing the monomeric precursors required for DNA replication and repair. The class I RNRs are composed of two subunits; the R1 subunit contains the active site for nucleotide reduction and allosteric effector binding sites, whereas the R2 subunit houses the essential diirontyrosyl (Y·) radical cofactor. A major unresolved issue is the mechanism by which the tyrosyl radical on R2 (Y122, Escherichia coli numbering) reversibly generates the transient thiyl radical (S·) on R1 that initiates nucleotide reduction. This intersubunit radical initiation is postulated to occur through a defined pathway involving conserved aromatic amino acids (R2: Y122, W48, Y356; R1: Y731, Y730) over a long distance of 35 Å. A 20-mer peptide identical to the C-terminal tail of R2 (356–375) and containing Y356 is a competitive inhibitor with respect to R2, and it effectively blocks nucleotide reduction. We now report that a 21-mer peptide, in which a tryptophan has been incorporated at the N terminus of the 20th mer, can replace the R2 subunit and initiate nucleotide reduction by photoinitiated radical generation. The deoxynucleotide generated depends on the presence of allosteric effector and is pathway-dependent. Replacement of Y731 of R2 with phenylalanine prevents deoxynucleotide formation. These results provide direct evidence for the chemical competence of aromatic amino acid radicals and the importance of Y356 in R2 in the radical initiation process of the class I RNRs. PMID:15123822

Chang, Michelle C. Y.; Yee, Cyril S.; Stubbe, JoAnne; Nocera, Daniel G.

2004-01-01

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A Comparative Study of the Radical-scavenging Activity of the Phenolcarboxylic Acids Caffeic Acid, p-Coumaric Acid, Chlorogenic Acid and Ferulic Acid, With or Without 2-Mercaptoethanol, a Thiol, Using the Induction Period Method  

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Full Text Available Phenolcarboxylic acid antioxidants do not act in vivo as radical-scavengers in isolation, but rather together with GSH (glutathione, a coantioxidant, they constitute an intricate antioxidant network. Caffeic acid, p-coumaric acid, ferulic acid and chlorogenic acid with or without 2-mercaptoethanol (ME, as a substitute for GSH, was investigated by the induction period (IP method for polymerization of methyl methacrylate (MMA initiated by thermal decomposition of 2,2'-azobisisobutyronitrile (AIBN, a source of alkyl radicals, R. and benzoyl peroxide (BPO, a source of peroxy radicals, PhCOO. using differential scanning calorimetry (DSC. Upon PhCOO. radical scavenging, the stoichiometric factors (n, number of free radical trapped by one mole of antioxidant for caffeic acid, ferulic acid, p-coumaric acid and chlorogenic acid were 2.4, 1.8, 1.7 and 0.9, whereas upon R. radical scavenging, the corresponding values were 1.3, 1.2, 1.0 and 0.8, respectively. Antioxidants with n values close to 2 suggest the stepwise formation of semiquinone radicals and quinones. By contrast, those with n values close to 1 suggest the formation of dimers after single-electron oxidation, possibly due to recombination of corresponding aryloxy radicals. The ratio of the rate constant of inhibition to that of propagation (kinh/kp declined in the order chlorogenic acid > p-coumaric acid > ferulic acid > caffeic acid. The ratio of the observed IP for the phenolcarboxylic acid/2-mercapto-ethanol (ME mixture (1:1 molar ratio (A to the calculated IP (the simple sum of phenol acid antioxidant and ME (B was investigated. Upon R. scavenging, the caffeic acid or p-coumaric acid/ME mixture was A/B > 1, particularly the former was 1.2, suggesting a synergic effect. By contrast, upon PhCOO. scavenging, the corresponding mixture was A/B < 1, particularly the latter was 0.7, suggesting an antagonistic effect. Upon both radicals scavenging, the A/B for the ferulic acid or chlorogenic acid/ME mixture was approximately 1. The reported beneficial antioxidant, anti-inflammatory and anticancer effects of caffeic acid and p-coumaric acid may be related to their prooxidant-antioxidant balance in the presence of GSH.

Seiichiro Fujisawa

2008-10-01

90

Free Radical Scavenging and Antibacterial Activity of Crude Extracts from Selected Plants of Medicinal Value Used in Zululand  

OpenAIRE

Ledebouria revoluta, Berkheya setifera and Carissa bispinosa are some of the medicinal plants used in South African traditional medicine. An investigation to evaluate antimicrobial, anti-inflammatory and free radical scavenging activities of the root crude extracts and fractions from the three plants was carried out. Reduction by 2, 2-azinobis (3-ethylbenzothiazoline)-6-sulfonic acid (ABTS.+) and 2, 2-di (4-tert-octylphenyl)-1-picrylhydrazyl (DP...

Muleya, E.; Ahmed, A. S.; Sipamla, A. M.; Mtunzi, F. M.

2014-01-01

91

Niobium Complexes As Lewis Acid and Radical Catalysts  

Energy Technology Data Exchange (ETDEWEB)

The reaction of lithium pentaphenylcyclopentadiende (Li C{sub 5}Ph{sub 5}) with niobium pentachloride in dichloromethane or toluene produces insoluble red-orange solids whose C/H/Cl analyses are not consistent with C{sub 5}Ph{sub 5}NbCl{sub 4}. Addition of an acetonitrile solution of LiC{sub 5}Ph{sub 5} with NbCl{sub 5} gives C{sub 5}Ph{sub 5}NbCl{sub 4} observed as a transient product by NMR spectroscopy, which then abstracts H from the acetonitrile solvent to give HC{sub 5}Ph{sub 5} and presumably NbCl{sub 4}CH{sub 2}CN. Reversal of the order of addition gives the {center_dot}C{sub 5}Ph{sub 5} radical as characterized by MS and EPR spectroscopy. Attempts to prepare the trimethylsilyl derivative Me{sub 3}SiC{sub 5}Ph{sub 5} (a less reducing cyclopentadienyl group) were unsuccessful. Reaction was observed only in tetrahydrofuran, producing only Me{sub 3}SiO(CH{sub 2}){sub 4}C{sub 5}Ph{sub 4}(m-C{sub 6}H{sub 4}(CH3)) characterized by {sup 1}H, {sup 13}C NMR and mass spectroscopy. The trimethylsilyltetraphenylcyclopentadienyl derivative, Me{sub 3}Si(H)C{sub 5}Ph{sub 4}, was characterized by {sup 1}H, {sup 13}C NMR and mass spectroscopy. This compound reacts with NbCl{sub 5} to give HCl and ClSiMe{sub 3} and a mixture of HC{sub 5}Ph{sub 4}NbCl{sub 4} and Me{sub 3}SiC{sub 5}Ph{sub 4}NbCl{sub 4}.

Wayne Tikkanen

2005-10-01

92

From D-glucuronic acid to L-iduronic acid derivatives via a radical tandem decarboxylation-cyclization.  

Science.gov (United States)

A synthesis to L-iduronic derivatives, major components of heparin derived pentasaccharides was accomplished by formal inversion of configuration at C-5 of a D-glucuronic acid derivative through radical formation at C-5 using Barton decarboxylation followed by intramolecular radical addition on an acetylenic tether at O-4 giving exclusively a bicyclic sugar of L-ido configuration. Oxidation and ring opening of this bicyclic sugar led to a L-iduronate. This method opens the way to short syntheses of pentasaccharidic moiety of Idraparinux and congeners. PMID:24508514

Salamone, Stéphane; Boisbrun, Michel; Didierjean, Claude; Chapleur, Yves

2014-03-11

93

Mechanism and kinetics in reactions of caffeic acid with radicals by pulse radiolysis and calculation  

Energy Technology Data Exchange (ETDEWEB)

The interaction of caffeic acid with e{sub aq}{sup -}, (CH{sub 3}){sub 2}(OH) CCH{sub 2}{sup {center_dot}}, CO{sub 2}{sup {center_dot}}{sup -}, H{sup {center_dot}}, {center_dot}OH and N{sub 3}{sup {center_dot}} radicals were studied by {gamma}-, pulse radiolysis and molecular orbital calculation. UV-visible spectra of electron/{center_dot}OH adducts, semi-quinone radicals of caffeic ions, and the stable products from the reactions were derived. The rate constants were determined. The attacked sites and the most favorable structures of the transient radicals were predicted. Reaction mechanisms were proposed. (author)

Li, Xifeng; Cai, Zhongli; Katsumura, Yosuke [Tokyo Univ., Tokai, Ibaraki (Japan). Nuclear Engineering Research Lab

2000-03-01

94

Spectroscopic studies on the antioxidant activity of p-coumaric acid.  

Science.gov (United States)

p-coumaric acid (4-hydroxycinnamic acid), a phenolic acid, is a hydroxyl derivative of cinnamic acid. It decreases low density lipoprotein (LDL) peroxidation and reduces the risk of stomach cancer. In vitro radical scavenging and antioxidant capacity of p-coumaric acid were clarified using different analytical methodologies such as total antioxidant activity determination by ferric thiocyanate, hydrogen peroxide scavenging, 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH) scavenging, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging activity and superoxide anion radical scavenging, ferrous ions (Fe(2+)) chelating activity and ferric ions (Fe(3+)) reducing ability. p-Coumaric acid inhibited 71.2% lipid peroxidation of a linoleic acid emulsion at 45?g/mL concentration. On the other hand, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), ?-tocopherol and ascorbic acid displayed 66.8%, 69.8%, 64.5% and 59.7% inhibition on the peroxidation of linoleic acid emulsion at the same concentration, respectively. In addition, p-coumaric acid had an effective DPPH scavenging, ABTS(+) scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe(3+)) reducing power and ferrous ions (Fe(2+)) chelating activities. Also, those various antioxidant activities were compared to BHA, BHT, ?-tocopherol and ascorbic acid as references antioxidant compounds. These results suggested that p-coumaric acid can be used in the pharmacological and food industry because of these properties. PMID:23892112

Kiliç, Ismail; Ye?ilo?lu, Ye?im

2013-11-01

95

Photolysis of nitrous acid as a primary source of OH radicals indoors  

Science.gov (United States)

Hydroxyl radical (OH) is the most important oxidant in the atmosphere controlling its self- oxidizing capacity. The main sources of OH radicals are the photolysis of ozone and the photolysis of nitrous acid (HONO). Due to the attenuation of solar radiation in the indoor environment, the possibility of OH formation through photolytic pathways indoors has been, up to now, ignored. We present the first direct measurement of OH radicals in the indoor environment. To the present moment, only indirect measurements based on the follow-up of different tracers or model studies had been carried out. The measurements were carried out between July, 19 and July, 30, 2011 in a classroom of 170 m3 with two large windows, oriented northwest. The effect of different concentrations of NO2 and RH were tested for their effect on the generation of HONO. In order to measure the generation of OH radicals under different light intensities, the experiments were performed at three different periods during the day, corresponding to different light intensity levels: 1) (11 a.m. to 15.00 p.m.), 2) (15.00 p.m. to 19.00 p.m.) and 3) (21.00 p.m. to 00:30 a.m.). A pool of state-of-the-art analytical instrumentation was deployed to tackle the objectives set. We measured OH radical concentrations of up to 1.8 106 cm-3 in the indoor environment (Gomez Alvarez et al., 2013). We also show that photolysis is an important source of OH radicals indoors under certain conditions, i.e. direct solar irradiation inside the room. HONO was the most probable precursor, considering the different sources leading to OH formation by photolysis. Additionally, the OH concentrations were found to follow a linear dependence with J(HONO) [HONO]. This was also supported by employing a simple quasi-photostationary state model (PSS) on the OH radical budget. These findings force a change in our understanding of indoor air quality as the reactivity linked to OH would involve formation of secondary species through chemical reactions, potentially more hazardous than the primary pollutants in the indoor air. This calculation indicates that, since the levels of concentration of OH radicals found in this study are one order of magnitude higher than predicted before, reactivity with OH becomes relevant as these reactions take place during a smaller time scale than typical air exchange rates indoors. Gómez Alvarez, E.; Amedro, D.; Afif, C. ; Gligorovski, S.; Schoemacker , C.; Fittschen, C. ; Doussin, J. F.; Wortham, H. (2013) Unexpectedly high indoor hydroxyl radical concentrations associated with nitrous acid. Proc. Natl. Acad. Sci. USA Accepted.

Gomez Alvarez, E.; Amedro, D.; Afif, C.; Gligorovski, S.; Schoemacker, C.; Fittschen, C. M.; Doussin, J.; Wortham, H.

2013-12-01

96

Indole-3-pyruvic and -propionic acids, kynurenic acid, and related metabolites as luminophores and free-radical scavengers.  

Science.gov (United States)

Chemiluminescence associated with oxidation by free radicals was investigated in an alkaline, hemin-catalysed hydrogen peroxide system, using the following tryptophan metabolites as radical scavengers: indole-3-pyruvic, indole-3-propionic, kynurenic, xanthurenic and quinaldic acids and 4-hydroxy-quinoline. Light emission from oxidation of the indolic compounds was only partially inhibited by the hydroxyl-radical scavenger DMSO, but strongly suppressed by the superoxide-anion scavenger Tiron, whereas chemi-luminescence generated from kynurenic acid was strongly inhibited by either of these compounds. Light emission from oxidation of kynurenic acid lasts for a surprisingly long period of time: At 0.4 mM and 20 degrees C, luminescence increased for 5 hours and continued at a high rate for more than a day. Comparison of structural analogues indicated that the 4-hydroxyl and carboxyl groups of kynurenic acid are essential for effective light emission, and that an additional 8-hydroxyl residue leading to an intramolecular hydrogen bond diminishes the reaction rate. PMID:10721080

Hardeland, R; Zsizsik, B K; Poeggeler, B; Fuhrberg, B; Holst, S; Coto-Montes, A

1999-01-01

97

Pyrite-induced hydroxyl radical formation and its effect on nucleic acids  

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Full Text Available Abstract Background Pyrite, the most abundant metal sulphide on Earth, is known to spontaneously form hydrogen peroxide when exposed to water. In this study the hypothesis that pyrite-induced hydrogen peroxide is transformed to hydroxyl radicals is tested. Results Using a combination of electron spin resonance (ESR spin-trapping techniques and scavenging reactions involving nucleic acids, the formation of hydroxyl radicals in pyrite/aqueous suspensions is demonstrated. The addition of EDTA to pyrite slurries inhibits the hydrogen peroxide-to-hydroxyl radical conversion, but does not inhibit the formation of hydrogen peroxide. Given the stability of EDTA chelation with both ferrous and ferric iron, this suggests that the addition of the EDTA prevents the transformation by chelation of dissolved iron species. Conclusion While the exact mechanism or mechanisms of the hydrogen peroxide-to-hydroxyl radical conversion cannot be resolved on the basis of the experiments reported in this study, it is clear that the pyrite surface promotes the reaction. The formation of hydroxyl radicals is significant because they react nearly instantaneously with most organic molecules. This suggests that the presence of pyrite in natural, engineered, or physiological aqueous systems may induce the transformation of a wide range of organic molecules. This finding has implications for the role pyrite may play in aquatic environments and raises the question whether inhalation of pyrite dust contributes to the development of lung diseases.

Leifer Nicole

2006-04-01

98

Interaction of the radiosensitizer paranitroacetophenone with radiation-induced radicals on nucleic acid components  

International Nuclear Information System (INIS)

The techniques of optical and conductiometric pulse radiolysis were used to investigate the reactions of PNAP with the free radicals produced by .OH attack on uracil, dihydrouracil, ribose, and deoxyribose. Electron transfer from sugar radicals to PNAP occurs with moderate efficiency, the yields being 37 and 23 percent for deoxyribose and ribose, respectively. In the case of uracil and dihydrouracil, however, the radicals produced by reaction with .OH do not transfer an electron to PNAP; instead, an addition product with the sensitizer is probably formed. This transient product absorbs strongly in the near uv. A comparison with other electron-affinic sensitizers, namely, nifuroxime and menaquinone, indicates that radical addition reactions, and not electron-transfer reactions, are of major significance in the interaction of these sensitizers with the radicals produced by .OH attack on nucleic acid bases. Reports in the literature used as evidence in support of the electron-transfer mechanism are shown to be faulty, due to improper analysis of the experimental data. An attempt is made to rationalize the various results reported for electron-affinic sensitizers

99

Interaction of aromatic alcohols, aldehydes and acids with ?-hydroxyl-containing carbon-centered radicals: A steady state radiolysis study  

International Nuclear Information System (INIS)

Benzaldehyde and its derivatives efficaciously oxidize in aqueous solutions ?-hydroxyl-containing carbon-centered radicals (?-HCR) of various structures, suppressing thereby the radical recombination and fragmentation reactions. The compounds containing cinnamic moieties are capable of adding ?-hydroxyethyl radicals (?-HER) to the carbon–carbon double bonds conjugated with the aromatic system to form molecular products identifiable by mass spectrometry. On radiolysis of aqueous ethanol solutions, reduction of ?-HER by aromatic alcohols and acids has been shown to proceed via formation of their adducts with hydrated electron species. - Highlights: ? Benzaldehydes oxidize ?-hydroxyl-containing carbon-centered radicals. ? Phenylproranoids add ?-hydroxyethyl radicals to the activated C=C bonds. ? Aromatic alcohols and acids form radical-adducts with eaq? in aqueous solutions.

100

Towards fuel cell membranes with improved lifetime: Aquivion® Perfluorosulfonic Acid membranes containing immobilized radical scavengers  

Science.gov (United States)

A facile synthesis, based on a wet impregnation technique and a thermal treatment, of a novel silica-supported cerium-oxide-based radical scavenger bearing sulfonic acid functionalities is presented. This material is loaded as a filler in ePTFE reinforced membranes (called R79-02S) prepared starting from Aquivion® Perfluoro-Sulfonic Acid (PFSA) dispersions. The aim is to mitigate the peroxy radicals attack to the polymeric membrane under fuel cell operating conditions. These membranes show much longer (7 times more) life-time in Accelerated Stress Tests (AST) and reduced fluoride release (about one half) in Fenton's tests than the radical scavenger-free membrane without any loss in electrochemical performance. Scavenger-free Aquivion® PFSA-based membrane durability is about 200 h in AST whereas the same membrane containing the newly developed radical scavenger exceeds 1400 h. These results confirm the stability of the modified membranes and the excellent activity of the composite scavenger in mitigating the polymer electrolyte degradation.

D'Urso, C.; Oldani, C.; Baglio, V.; Merlo, L.; Aricò, A. S.

2014-12-01

101

A comparison of abts and dpph methods for assessing the total antioxidant capacity of human milk  

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Full Text Available Introduction. The Total Antioxidant Capacity (TAC of human milk reflects the concentration and the activity of many components which prevent oxidative degradation of fats and proteins. This study compares the effectiveness of ABTS and DPPH tests with regard to the recovery, precision and sensitivity (detection and quantification limit of (TAC values in human milk. Material  and methods. TAC values were determined in twenty five samples of human milk obtained from healthy mothers, residents of Gda?sk, on the 14th day postpartum. Results.  The average TAC of human milk determined by ABTS assay was 19.61 ±3.311 mg TE (Trolox Equivalents/100 cm3, the average values obtained by the DPPH assay reached 9.95 ±4.36 mg TE/100 cm3. For each milk sample the TAC determined by the ABTS test was significantly higher than the values pro- duced by the DPPH test. The above findings can be attributed to the presence of substances whose spectra overlap with DPPH• spectra. ABTS test was characterised by a higher sensitivity and repeatability of the determination of TAC in human milk compared to the DPPH test. Conclusions. Comparing the calculated values for the validation parameters of both methods and taking into account the solubility of DPPH only in polar matrices, slower reaction of selected antioxidants with DPPH radical, and the presence in human milk constituents absorbing electromagnetic radiation in the absorption of DPPH be assumed that the ABTS test is more appropriate method of  determining of TAC in breast milk.

Dorota Martysiak-?urowska

2012-03-01

102

Free Radical Scavenging Activity of Kielmeyera variabilis (Clusiaceae)  

OpenAIRE

As part of our ongoing research on antioxidant agents from Brazilian flora, we screened the free radical scavenging activity of two extracts and eight fractions of Kielmeyera variabilis (Clusiaceae) using DPPH· (2,2-diphenyl-1-picrylhydrazyl-hydrate) and ABTS·+ [2,2'-azinobis(3-ethylenebenzothiazoline-6-sulfonic acid)] colorimetric assays. The ethyl acetate and n-butanol fractions of the leaves of K. variabilis displayed the strongest activity (IC50 of 3.5 ± 0.3 and 4.4 ± 0.2 ?g mL?...

Dulce Helena Siqueira Silva; Vanderlan da Silva Bolzani,; Marcos Marçal Ferreira Queiroz; Scheila Cristina Gutkoski Skrzek; Luis Octávio Regasini; Aline Coqueiro

2013-01-01

103

The B-cell lymphoma 2 (BCL2)-inhibitors, ABT-737 and ABT-263, are substrates for P-glycoprotein  

International Nuclear Information System (INIS)

Highlights: ? The BCL2-inhibitor ABT-263 is a substrate for P-glycoprotein. ? Apoptosis is inhibited by P-glycoprotein expression. ? Overexpression of P-glycoprotein may contribute to resistance to ABT-263 or ABT-737. -- Abstract: Inhibition of BCL2 proteins is one of the most promising new approaches to targeted cancer therapy resulting in the induction of apoptosis. Amongst the most specific BCL2-inhibitors identified are ABT-737 and ABT-263. However, targeted therapy is often only effective for a limited amount of time because of the occurrence of drug resistance. In this study, the interaction of BCL2-inhibitors with the drug efflux transporter P-glycoprotein was investigated. Using 3H labelled ABT-263, we found that cells with high P-glycoprotein activity accumulated less drug. In addition, cells with increased P-glycoprotein expression were more resistant to apoptosis induced by either ABT-737 or ABT-263. Addition of tariquidar or verapamil sensitized the cells to BCL2-inhibitor treatment, resulting in higher apoptosis. Our data suggest that the BCL2-inhibitors ABT-737 and ABT-263 are substrates for P-glycoprotein. Over-expression of P-glycoprotein may be, at least partly, responsible for resistance to these BCL2-inhibitors.

104

The B-cell lymphoma 2 (BCL2)-inhibitors, ABT-737 and ABT-263, are substrates for P-glycoprotein  

Energy Technology Data Exchange (ETDEWEB)

Highlights: {yields} The BCL2-inhibitor ABT-263 is a substrate for P-glycoprotein. {yields} Apoptosis is inhibited by P-glycoprotein expression. {yields} Overexpression of P-glycoprotein may contribute to resistance to ABT-263 or ABT-737. -- Abstract: Inhibition of BCL2 proteins is one of the most promising new approaches to targeted cancer therapy resulting in the induction of apoptosis. Amongst the most specific BCL2-inhibitors identified are ABT-737 and ABT-263. However, targeted therapy is often only effective for a limited amount of time because of the occurrence of drug resistance. In this study, the interaction of BCL2-inhibitors with the drug efflux transporter P-glycoprotein was investigated. Using {sup 3}H labelled ABT-263, we found that cells with high P-glycoprotein activity accumulated less drug. In addition, cells with increased P-glycoprotein expression were more resistant to apoptosis induced by either ABT-737 or ABT-263. Addition of tariquidar or verapamil sensitized the cells to BCL2-inhibitor treatment, resulting in higher apoptosis. Our data suggest that the BCL2-inhibitors ABT-737 and ABT-263 are substrates for P-glycoprotein. Over-expression of P-glycoprotein may be, at least partly, responsible for resistance to these BCL2-inhibitors.

Vogler, Meike, E-mail: mv62@le.ac.uk [MRC Toxicology Unit, University of Leicester, LE1 9HN Leicester (United Kingdom); Dickens, David, E-mail: David.Dickens@liverpool.ac.uk [Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, L69 3GL Liverpool (United Kingdom); Dyer, Martin J.S., E-mail: mjsd1@le.ac.uk [MRC Toxicology Unit, University of Leicester, LE1 9HN Leicester (United Kingdom); Owen, Andrew, E-mail: aowen@liverpool.ac.uk [Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, L69 3GL Liverpool (United Kingdom); Pirmohamed, Munir, E-mail: munirp@liv.ac.uk [Department of Molecular and Clinical Pharmacology, Institute of Translational Medicine, University of Liverpool, L69 3GL Liverpool (United Kingdom); Cohen, Gerald M., E-mail: gmc2@le.ac.uk [MRC Toxicology Unit, University of Leicester, LE1 9HN Leicester (United Kingdom)

2011-05-06

105

A Comparative Study of the Radical-scavenging Activity of the Phenolcarboxylic Acids Caffeic Acid, p-Coumaric Acid, Chlorogenic Acid and Ferulic Acid, With or Without 2-Mercaptoethanol, a Thiol, Using the Induction Period Method  

OpenAIRE

Phenolcarboxylic acid antioxidants do not act in vivo as radical-scavengers in isolation, but rather together with GSH (glutathione), a coantioxidant, they constitute an intricate antioxidant network. Caffeic acid, p-coumaric acid, ferulic acid and chlorogenic acid with or without 2-mercaptoethanol (ME), as a substitute for GSH, was investigated by the induction period (IP) method for polymerization of methyl methacrylate (MMA) initiated by thermal decomposition of 2,2'-azobisisobutyronitrile...

Seiichiro Fujisawa; Yoshinori Kadoma

2008-01-01

106

Products of aqueous vitamin B5 (pantothenic acid) formed by free radical reactions  

Energy Technology Data Exchange (ETDEWEB)

The radiolysis of aqueous vitamin B5 (pantothenic acid) has been investigated under various experimental conditions. The highest vitamin degradation (G=3.22) was observed in solutions saturated with N{sub 2}O, where 90% OH radicals are operating. As final products, the following were established: aldehydes, carboxylic acids and ammonia. Their yield strongly depends on the presence/absence of air as well as on N{sub 2}O (used to convert e{sub aq} {sup -} into OH) and was determined as a function of absorbed radiation dose. HPLC-analysis showed that in all media, a main product is formed, having the highest yield in aerated solutions. Based on the chemical analysis, it appears that the OH radicals are most involved in the degradation process. A precise sequence of the reaction steps could not be given presently, because of the implication of many simultaneous reactions.

Schittl, H. [Section of Radiation Biology, Department of Nutritional Sciences, University of Vienna, Althanstr. 14, UZA II, A-1090 Vienna (Austria); Quint, R.M. [Section of Radiation Biology, Department of Nutritional Sciences, University of Vienna, Althanstr. 14, UZA II, A-1090 Vienna (Austria); Getoff, N. [Section of Radiation Biology, Department of Nutritional Sciences, University of Vienna, Althanstr. 14, UZA II, A-1090 Vienna (Austria)]. E-mail: nikola.getoff@univie.ac.at

2007-10-15

107

PHENOLIC ACIDS AND FREE RADICAL SCAVENGING ACTIVITY OF ALCHEMILLA JUMRUKCZALICA PAWL  

Directory of Open Access Journals (Sweden)

Full Text Available Comparative study of free radical scavenging activity and phenolic acid content of Bulgarian endemic Alchemilla jumrukczalica and the commercial herbal - Alchemilla vulgaris complex was carried. The methanol extracts of studied samples showed significant antiradical activity. The concentration of the extracts needed for 50% inhibition of DPPH was found to be 12,09 µg/ml and 19,62 µg/ml for A. jumrukczalica and A. vulgaris complex, respectively. Ten free and seventeen bonded phenolic acids were identified and quantified by performed of gas chromatography mass-spectrometry (GC-MS. Gentisic, protocatechuic, salicylic and trans-cinnamic acids were represented in the greatest quantity among the identified phenolic acids. This is the first detailed analysis on qualitative and quantitative composition of phenolic acids in Alchemilla species.

M. Nikolova et al.

2012-03-01

108

Dimers in ?-pinene secondary organic aerosol: effect of hydroxyl radical, ozone, relative humidity and aerosol acidity  

OpenAIRE

The formation of secondary organic aerosol (SOA) from both ozonolysis and hydroxyl radical (OH)-initiated oxidation of ?-pinene under conditions of high nitric oxide (NO) concentrations with varying relative humidity (RH) and aerosol acidity was investigated in the University of North Carolina dual outdoor smog chamber facility. SOA formation from ozonolysis of ?-pinene was enhanced relative to that from OH-initiated oxidation in the presence of initially high-NO condition...

Kristensen, K.; Cui, T.; Zhang, H.; Gold, A.; Glasius, M.; Surratt, J. D.

2014-01-01

109

Formation and reactivity of phenylperoxyl radicals in aqueous solutions  

International Nuclear Information System (INIS)

The reaction of phenyl radicals with oxygen, to produce phenylperoxyl radicals, and the reactions of several phenylperoxyl radicals with a number of organic compounds in aqueous solutions have been studied by pulse radiolysis. Phenyl radicals were produced by reduction of aryl halides with hydrated electrons. The rate constant for the reaction of 4-carboxyphenyl with O2 was determined from the rate of buildup of the peroxyl radical absorption at 520 nm as a function of [O2] and found to be 1.6 x 109 L mol-1 s-1. Phenyl radicals react with 2-PrOH by H abstraction; a rate constants of 4 x 106 L mol-1 s-1 was determined for 4-carboxyphenyl by competition with the reaction of this radical with O2. Phenylperoxyl radicals react with 4-methoxyphenolate ions, trolox C(6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), ascorbate ions, chlorpromazine, and ABTS [2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate ion)] by one-electron oxidation. The rate constants for such reactions, determined from the rate of formation of the one-electron oxidation product as a function of substrate concentration, were found to be near 108-109 L mol-1 s-1. 24 refs., 4 figs., 1 tab

110

Free radical-induced cross-linking of polydeoxythymidylic acid in deoxygenated aqueous solution  

International Nuclear Information System (INIS)

Radiation-generated hydroxyl radicals and hydrogen atoms were shown to induce the cross-linking of polydeoxythymidylic acid (mol.wt approx. 170000) in N2O-saturated aqueous solution. The irradiated samples were hydrolysed with formic acid and then analysed by high performance liquid chromatography. Products were isolated and subsequently characterized by capillary gas chromatography-mass spectrometry. The presence of previously described monomeric thymine products was also shown. Yields were determined and mechanisms of formation were described for the products. (author)

111

Free-radical-mediated conjugate additions. Enantioselective synthesis of butyrolactone natural products: (-)-enterolactone, (-)-arctigenin, (-)-isoarctigenin, (-)-nephrosteranic acid, and (-)-roccellaric acid.  

Science.gov (United States)

Lewis acid-mediated conjugate addition of alkyl radicals to a differentially protected fumarate 10 produced the monoalkylated succinates with high chemical efficiency and excellent stereoselectivity. A subsequent alkylation or an aldol reaction furnished the disubstituted succinates with syn configuration. The chiral auxiliary, 4-diphenylmethyl-2-oxazolidinone, controlled the stereoselectivity in both steps. Manipulation of the disubstituted succinates obtained by alkylation furnished the natural products (-)-enterolactone, (-)-arctigenin, and (-)-isoarctigenin. The overall yields for the target natural products were 20-26% over six steps. Selective functionalization of the disubstituted succinates obtained by aldol condensation gave the paraconic acid natural products (-)-nephrosteranic acid (8) and (-)-roccellaric acid (9). The overall yield of the natural products 8 and 9 over four steps was 53% and 42%, respectively. PMID:11895386

Sibi, Mukund P; Liu, Pingrong; Ji, Jianguo; Hajra, Saumen; Chen, Jian-xie

2002-03-22

112

ACID GAS REMOVAL CHARACTERISTICS OF CORONA RADICAL SHOWER SYSTEM FOR A TREATMENT OF STATIONARY ENGINE FLUE GAS  

Science.gov (United States)

Acid gas removal experiments are carried out in large bench scale corona radical shower reactor. A simulated engine flue gas is air mixed with NO, SO2 and CH4. Optimums for acid gas removal rate have been conducted in terms of the ammonia to acid gas molar ratio, the applied volt...

113

In vitro antioxidant and radical scavenging of Guinean kinkeliba leaf (Combretum micranthum G. Don) extracts.  

Science.gov (United States)

The antioxidant properties of the water and ethanol leaf extracts of kinkeliba (Combretum micranthum) were investigated, including scavenging of the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical (IC?? values: 8.02?±?0.34 for the ethanol extract [KE] and 9.1?±?0.28 for the water extract [KW]), the 2,2'-azinobis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical (IC(50) values: 7.4?±?0.14 for KE and 11.8?±?0.01 for KW) and the hydroxyl radical (58.1% for KE and 61.1% for KW). The ferric thiocyanate method, reducing power, metal chelating activity, an assay of protein oxidation and the ?-carotene-linoleic bleaching assay were also used. Butylated hydroxytoluene and ascorbic acid were used as the reference antioxidant compounds. At 20 mg mL?¹ concentration, KW and KE provided 36.8% and 75.1% inhibition of lipid peroxidation of linoleic acid emulsion, respectively. The IC?? values of the ethanol extract in ABTS and DPPH tests were significantly lower than those from the water extract. Furthermore, crude polyphenols were extracted from kinkeliba leaf with 90% ethanol solution using a water bath treatment and then purified by a macroporous resin, AB-8. The polyphenols from kinkeliba leaf were subjected to analyses by RP-HPLC and ESI-MS. The dominant polyphenols in kinkeliba leaf were identified as gallic acid, rutin trihydrate, (+)-catechin and benzoic acid. PMID:21480049

Touré, Alhassane; Xu, Xueming; Michel, T; Bangoura, M

2011-07-01

114

E.s.r. studies on the mechanism of hydroxyl radical-induced strand breakage of polyuridylic acid  

International Nuclear Information System (INIS)

Reaction of photolytically produced radical OH radicals with polyuridylic acid [poly(U)] in neutral solutions resulted in the electron spin resonance (e.s.r.) spectrum of the C(5)-OH-6-yl (= 6-yl) radical 1b of the nucleobase. At pH ? 4 the spectrum of the base radical had disappeared and instead the cyclic 2'-oxo-3'-yl sugar radical 2a was observed. The assignment of the sugar radical was supported by model reactions with SO4-radical as the radical inducing agent. Time-resolved e.s.r. measurements showed that the rate of decay of the 6-yl base radical at neutral pH is virtually the same as that of the strand break (sb) formation. These results prove that: (i) in agreement with an earlier proposal the C(2') mechanism contributes to sb formation of poly(U), and (ii) the decay of the 6-yl radical is the rate-determining step in the reaction sequence leading to strand breakage. The change in the e.s.r. spectra at pH 4 is due to an increase in the rate of sb formation with increasing proton concentration. (author)

115

E. s. r. studies on the mechanism of hydroxyl radical-induced strand breakage of polyuridylic acid  

Energy Technology Data Exchange (ETDEWEB)

Reaction of photolytically produced radical OH radicals with polyuridylic acid (poly(U)) in neutral solutions resulted in the electron spin resonance (e.s.r.) spectrum of the C(5)-OH-6-yl (= 6-yl) radical 1b of the nucleobase. At pH /le/ 4 the spectrum of the base radical had disappeared and instead the cyclic 2'-oxo-3'-yl sugar radical 2a was observed. The assignment of the sugar radical was supported by model reactions with SO/sub 4//sup -radical/ as the radical inducing agent. Time-resolved e.s.r. measurements showed that the rate of decay of the 6-yl base radical at neutral pH is virtually the same as that of the strand break (sb) formation. These results prove that: (i) in agreement with an earlier proposal the C(2') mechanism contributes to sb formation of poly(U), and (ii) the decay of the 6-yl radical is the rate-determining step in the reaction sequence leading to strand breakage. The change in the e.s.r. spectra at pH 4 is due to an increase in the rate of sb formation with increasing proton concentration. (author).

Hildenbrand, K.; Schulte-Frohlinde, D.

1989-05-01

116

Reaction of sulphate radical anion (SO4·-) with cyanuric acid. A potential reaction for its degradation?  

International Nuclear Information System (INIS)

A novel reaction between sulfate radical anion (SO4·-) and cyanuric acid (CA), a non-degradable end product of the oxidative degradation of the triazine based herbicide, atrazine, is presented using laser flash photolysis and steady state radiolysis techniques at pH 5. A second order rate constant of 1.9x107 dm3 mol-1 s-1 has been determined and the transient intermediate (?max=330 nm) is assigned to a radical cation of CA (CA·+). The degradation profile indicated that about 76% of CA have been decomposed after an absorbed ?-radiation dose of 18 kGy. It is therefore proposed that the reaction of SO4·- could be utilised for the degradation of CA in aqueous medium which is normally stable to any Advanced Oxidation Processes. (author)

117

Vitamin C (ascorbic acid) induced hydroxyl radical formation in copper contaminated household drinking water: role of bicarbonate concentration.  

Science.gov (United States)

We have previously shown that Vitamin C (ascorbic acid) can trigger hydroxyl radical formation in copper contaminated household drinking water. We report here that the capacity of ascorbic acid to catalyze hydroxyl radical generation in the drinking water samples is strongly dependent on the bicarbonate concentration (buffer capacity and pH) of the samples. We found that at least 50 mg/l bicarbonate was required in the water samples to maintain the pH over 5.0 after ascorbic acid addition. At this pH, that is higher than the pKa1 4.25 of ascorbic acid, a hydroxyl radical generating redox cycling reaction involving the mono-anion of vitamin C and copper could take place. The ascorbic acid induced hydroxyl radical generating reaction could easily be mimicked in Milli-Q water by supplementing the water with copper and bicarbonate. Our results demonstrate that ascorbic acid can induce a pH dependent hydroxyl radical generating reaction in copper contaminated household tap water that is buffered with bicarbonate. The impact of consuming ascorbic acid together with copper and bicarbonate containing drinking water on human health is discussed. PMID:14567450

Jansson, Patric J; Asplund, Klara U M; Mäkelä, Johanna C; Lindqvist, Christer; Nordström, Tommy

2003-08-01

118

Radical scavenging activity and composition of raspberry (Rubus idaeus) leaves from different locations in Lithuania.  

Science.gov (United States)

Raspberry (Rubus idaeus) leaves, collected in different locations of Lithuania were extracted with ethanol and the extracts were tested for their antioxidant activity (AA) by using ABTS(.)(+) decolourisation and DPPH(.) scavenging methods. All extracts were active, with radical scavenging capacity at the used concentrations from 20.5 to 82.5% in DPPH(.) reaction system and from 8.0 to 42.7% in ABTS(.)(+) reaction. The total amount of phenolic compounds in the leaves varied from 4.8 to 12.0 mg of gallic acid equivalents (GAE) in 1 g of plant extract. Quercetin glucuronide, quercetin-3-O-glucoside and rutin were identified in the extracts. PMID:17215088

Venskutonis, P R; Dvaranauskaite, A; Labokas, J

2007-02-01

119

Triethylborane-initiated room temperature radical addition of hypophosphites to olefins: synthesis of monosubstituted phosphinic acids and esters.  

Science.gov (United States)

A novel and practical approach to monosubstituted phosphinic acid (alkylphosphonous acid) derivatives from hypophosphite salts or esters is described. Phosphorus-centered radical formation is initiated with Et(3)B/O(2), and the reaction is conveniently conducted at room temperature in an open flask. In contrast to previously reported conditions for the radical reaction of hypophosphorous acid and sodium hypophosphite (peroxide initiators, acid catalysis, heat), the method proceeds under neutral conditions and therefore tolerates a wide range of functional groups. Previously inaccessible phosphinic acids can be prepared in a single step from cheap starting materials. Excellent selectivity is observed for monoaddition, and symmetrical dialkyl phosphinates do not form in significant amounts. Monosubstituted phosphinic acids are usually obtained in better than 90% purity by a simple extractive workup; however, isolated yields are diminished if the substituent is polar. Because radicals derived from hypophosphites are electrophilic, the reaction is limited to the use of electron-rich olefins. The reaction conditions can also be employed in the room temperature radical reduction of alkyl halides and provide an exceptionally mild and environmentally friendly alternative to the use of tributyltin hydride. The remarkable mild nature of the reaction conditions allows for the radical reaction of sensitive alkyl hypophosphites to occur, in which case, a catalytic amount of Et(3)B suffices to deliver alkyl phosphinate esters in reasonable yield. PMID:11578230

Deprèle, S; Montchamp, J L

2001-10-01

120

Caffeic Acid Inhibits the Formation of 7-Carboxyheptyl Radicals from Oleic Acid under Flavin Mononucleotide Photosensitization by Scavenging Singlet Oxygen and Quenching the Excited State of Flavin Mononucleotide  

OpenAIRE

We examined the effects of caffeic acid (CA) and related compounds on 7-carboxyheptyl radical formation. This analysis was performed using a standard D2O reaction mixture containing 4.3 mM oleic acid, 25 ?M flavin mononucleotide (FMN), 160 mM phosphate buffer (pH 7.4), 10 mM cholic acid, 100 mM ?-(4-pyridyl-1-oxide)-N-tert-butylnitrone, and 1 mM Fe(SO4)2(NH4)2 during irradiation with 7.8 J/cm2 at 436 nm. 7-Carboxyheptyl radical formation was inhibited by CA, catechol, gallic acid, chlorog...

Marie Asano; Hideo Iwahashi

2014-01-01

121

Reactivity of chlorine radical with submicron palmitic acid particles: kinetic measurements and product identification  

Science.gov (United States)

The heterogeneous reaction of Cl• radicals with submicron palmitic acid (PA) particles was studied in an aerosol flow tube in the presence or in the absence of O2. Fine particles were generated by homogeneous condensation of PA vapours and introduced into the reactor, where chlorine atoms were produced by photolysis of Cl2 using UV lamps surrounding the reactor. The effective reactive uptake coefficient (?) has been determined from the rate loss of PA measured by gas chromatography-mass spectrometer (GC/MS) analysis of reacted particles as a function of the chlorine exposure. In the absence of O2, ? = 14 ± 5 indicates efficient secondary chemistry involving Cl2. GC/MS analysis has shown the formation of monochlorinated and polychlorinated compounds in the oxidized particles. Although the PA particles are solid, the complete mass can be consumed. In the presence of oxygen, the reaction is still dominated by secondary chemistry but the propagation chain length is smaller than in the absence of O2, which leads to an uptake coefficient ? = 3 ± 1. In the particulate phase, oxocarboxylic acids and dicarboxylic acids were identified by GC/MS. The formation of alcohols and monocarboxylic acids is also suspected. A reaction pathway for the main products and more functionalized species is proposed. All these results show that solid organic particles could be efficiently oxidized by gas-phase radicals not only on their surface but also in bulk by mechanisms which are still unclear. They help to understand the aging of primary tropospheric aerosol containing fatty acids.

Mendez, M.; Ciuraru, R.; Gosselin, S.; Batut, S.; Visez, N.; Petitprez, D.

2013-12-01

122

Reactivity of chlorine radical with submicron palmitic acid particles: kinetic measurements and products identification  

Science.gov (United States)

The heterogeneous reaction of Cl. radicals with sub-micron palmitic acid (PA) particles was studied in an aerosol flow tube in the presence or in the absence of O2. Fine particles were generated by homogeneous condensation of PA vapors and introduced in the reactor where chlorine atoms are produced by photolysis of Cl2 using UV lamps surrounding the reactor. The effective reactive uptake coefficient (?) has been determined from the rate loss of PA measured by GC/MS analysis of reacted particles as a function of the chlorine exposure. In the absence of O2, ? = 14 ± 5 indicates efficient secondary chemistry involving Cl2. GC/MS analyses have shown the formation of monochlorinated and polychlorinated compounds in the oxidized particles. Although, the PA particles are solid, the complete mass can be consumed. In the presence of oxygen, the reaction is still dominated by secondary chemistry but the propagation chain length is smaller than in the absence of O2 which leads to an uptake coefficient ? = 3 ± 1. In the particulate phase, oxocarboxylic acids and dicarboxylic acids are identified by GC/MS. Formation of alcohols and monocarboxylic acids are also suspected. All these results show that solid organic particles could be efficiently oxidized by gas-phase radicals not only on their surface, but also in bulk by mechanisms which are still unclear. Furthermore the identified reaction products are explained by a chemical mechanism showing the pathway of the formation of more functionalized products. They help to understand the aging of primary tropospheric aerosol containing fatty acids.

Mendez, M.; Ciuraru, R.; Gosselin, S.; Batut, S.; Visez, N.; Petitprez, D.

2013-06-01

123

Reactivity of chlorine radical with submicron palmitic acid particles: kinetic measurements and products identification  

Directory of Open Access Journals (Sweden)

Full Text Available The heterogeneous reaction of Cl. radicals with sub-micron palmitic acid (PA particles was studied in an aerosol flow tube in the presence or in the absence of O2. Fine particles were generated by homogeneous condensation of PA vapors and introduced in the reactor where chlorine atoms are produced by photolysis of Cl2 using UV lamps surrounding the reactor. The effective reactive uptake coefficient (? has been determined from the rate loss of PA measured by GC/MS analysis of reacted particles as a function of the chlorine exposure. In the absence of O2, ? = 14 ± 5 indicates efficient secondary chemistry involving Cl2. GC/MS analyses have shown the formation of monochlorinated and polychlorinated compounds in the oxidized particles. Although, the PA particles are solid, the complete mass can be consumed. In the presence of oxygen, the reaction is still dominated by secondary chemistry but the propagation chain length is smaller than in the absence of O2 which leads to an uptake coefficient ? = 3 ± 1. In the particulate phase, oxocarboxylic acids and dicarboxylic acids are identified by GC/MS. Formation of alcohols and monocarboxylic acids are also suspected. All these results show that solid organic particles could be efficiently oxidized by gas-phase radicals not only on their surface, but also in bulk by mechanisms which are still unclear. Furthermore the identified reaction products are explained by a chemical mechanism showing the pathway of the formation of more functionalized products. They help to understand the aging of primary tropospheric aerosol containing fatty acids.

M. Mendez

2013-06-01

124

Electrospray ionization mass spectrometry applied to study the radical acetylation of amino acids, peptides and proteins  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Recentemente nosso grupo demostrou experimentalmente que a hipótese de produção de radical acetil em meio tamponado no sistema diacetil/peroxinitrito era possível. Diacetil é um flavorizante em alimentos, cigarros e bebidas. O peroxinitrito é encontrado na mitocôndria, e em certas condições como um [...] processo de infeção em humanos, a concentração aumenta significativamente. Em sistemas biológicos, radicais podem facilmente modificar a estrutura e atividade de ácidos nucleicos, proteínas e outras biomoléculas, causando significativo estres oxidativo. Baseado em dados de ressonância magnética e espectrometria de massas, este artigo apresenta os produtos que provam a produção do radical acetil e a formação de compostos estáveis devido à ligação covalente entre o acetil e os aminoácidos (produtos acetilados), e os adutos de peptídeos e proteínas. Estes materiais foram separados por eletroforese capilar e identificados por espectrometria de massas. O meio reacional consistiu da mistura de diacetil e peroxynitrito em uma relação de 1:2 e em 20 mmol L-1 de fosfato de sódio, no valor de pH 7,2. Estes experimentos também revelam a dupla acetilação da lisina, demonstrando a alta reatividade do composto com biomoléculas contendo grupos de nitrogênio, abundantemente encontradas em sistemas biológicos. A mudança estrutural de uma molécula acetilada é uma fonte de modificações pós-tradução com inúmeras consequências biológicas. Abstract in english Recently, our group proposed a process that generated acetyl radicals in a reaction medium buffered with a diacetyl/peroxynitrite system. Diacetyl is a flavoring agent in food, cigarettes and drinks. Peroxynitrite is found in mitochondria, and in certain conditions, such as an infection in humans, i [...] ts concentration is augmented significantly. In biological systems, radical compounds can easily modify the structure and activity of nucleic acids, proteins and other biomolecules, causing significant oxidative stress. Based on paramagnetic resonance and mass spectrometry data, this work discusses products that prove acetyl radicals are produced and are able to form stable covalent bonds with amino acid (acetylated products), peptide and protein adducts. These materials were separated and detected by capillary electrophoresis coupled with tandem mass spectrometry or offline mass spectrometry. The reaction medium contained a 1:2 mixture of diacetyl and peroxynitrite dissolved in 200 mmol L-1 of pH 7.2 sodium phosphate buffer. These experiments also reveal the double acetylation of lysine, demonstrating the high reactivity of these compounds when in contact with nitrogen-containing biomolecules readily found in biological systems. These structural changes might be an epigenetic source of post-translational protein modification.

Atecla N. L., Alves; Leticia D. L., Jedlicka; Júlio, Massari; Maria A., Juliano; Etelvino J. H., Bechara; Nilson A., Assunção.

1983-19-01

125

Oxidation of Amino Acids by Chlorpromazine Cation Radical and Co-Catalysis by Chlorpromazine  

Directory of Open Access Journals (Sweden)

Full Text Available The long-tem use of chlorpromazine (CPZ may cause severe side effects. This property of CPZ might be related to pro-oxidant effects of the chlorpromazine cation radical (CPZ·+, which can be easily generated by catalytic action of peroxidases, including the neutrophil myeloperoxidase (MPO and by methemoglobin. Aiming the comprehension of a putative physiological effect of CPZ·+ upon biomolecules, in this work we studied the reactivity of CPZ·+ with amino acids and the co-catalytic effect of CPZ during the oxidation of amino acids by horseradish peroxidase (HRP/H2O2 system. We also studied whether natural blood plasma components as ascorbic acid, uric acid and nitrite could inhibit the oxidative effect of CPZ·+. We found that tryptophan, tyrosine and cysteine were easily oxidized by pure CPZ·+. Other amino acids as methionine, glycine, phenylalanine, aspartic acid and lysine were unreactive. The decomposition of CPZ·+ was exacerbated by uric acid, ascorbic acid and nitrite, provoking inhibition in the amino acids oxidation. In experiments with HRP/H2O2, and using CPZ as a co-catalyst, a strong effect upon oxidation of tryptophan, tyrosine and cysteine was obtained. It was also found that tryptophan was more reactive than tyrosine with CPZ·+, a feature that could be related to the recently described favorable interaction between tryptophan and CPZ. The use of CPZ as a co-catalyst is discussed regarding its role in the efficient oxidation of tryptophan.

Manoel L. de Menezes

2012-01-01

126

Free radical scavenging activity of ethanolic extracts from herbs and spices commercialized in Brazil  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Extratos etanólicos de 23 ervas e condimentos desidratados comercializados no Brasil foram analisados quanto as suas propriedades antioxidantes utilizando os radicais 2,2'-difenil-?-picrilhidrazil (DPPH•) e ácido 2,2'-azino-bis(3-etilbenzotiazolina-6-sulfônico) (ABTS•+), Trolox foi usado como referê [...] ncia para ambos radicais. As curvas cinéticas seguiram o modelo cinético de primeira ordem, e a partir destas foram calculadas as constantes de velocidade de (k obs). Os extratos de sálvia e de alecrim apresentaram as maiores capacidades redutoras de radicais livres, enquanto o extrato de cebola praticamente não apresentou atividade e o colorífico, um dos condimentos mais consumidos no Brasil, apresentou baixa atividade de aprisionamento de radicaisABTS•+. Três situações distintas foram observadas em relação à capacidade de aprisionar radicais DPPH•: (1) extratos, como os de alecrim e de louro, que apresentaram as mesmas concentrações eficientes (EC50), porém, valores de TEAC e velocidade de ação (k obs) distintos ; (2) extratos, como os de alho e de manjericão, que apresentaram valores similares de EC50 e TEAC, com valores distintos de k obs e (3) extratos com a mesma velocidade de ação que diferiram totalmente na capacidade de aprisionamento de radicais livres, como de pimenta preta, segurelha, noz moscada, alecrim e sálvia. Considerações semelhantes podem ser feitas para os resultados de ABTS•+. Osdois métodos apresentaram boa correlação de TEAC, indicando que a reatividade dos compostos presentes nos extratos etanólicos foi similar. A atividade redutora de ABTS•+ para pimenta da Jamaica, manjericão, cardamomo, cebolinha, colorífico, cominho, dill, louro, manjerona, salsinha e estragão foi reportada pela primeira vez. Abstract in english Ethanolic extracts from 23 different dried herbs and spices commercialized in Brazil were investigated for their free radical scavenging properties using the stable free radicals 2,2'-diphenyl-?-picrylhydrazyl (DPPH•) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS•+), and Trolox a [...] s reference (TEAC) for both radicals. The kinetic curves for both radicals showed to follow the first order kinetics model and the decay rate constant (k obs) was calculated. For all the samples, the two methods showed a good linear TEAC correlation, indicating that the average reactivity of the compounds present in the ethanolic extracts was similar. Sage and rosemary extracts showed the highest free radical scavenging capacities, while onion showed negligible activity and colorifico, one of the most consumed spices in Brazil, showed low ABTS•+ scavenging activity. Three distinct situations were found for the extracts concerning the DPPH• scavenging capacities: (1) extracts, like rosemary and laurel, that presented the same efficient concentrations (EC50 ) but differed in the TEAC values and velocities of action (k obs), (2) extracts, such as garlic and basil, that showed similar EC50 and TEAC values, but different k obs values and (3) extracts that reacted at the same velocities but completely differed in the free radical scavenging capacities, like black pepper, savory, nutmeg, rosemary and sage. Similar considerations could be done for the ABTS•+ results. For the first time the ABTS•+ scavenging activity for allspice, basil, cardamom, chives, colorifico, cumin, dill, laurel, marjoram, parsley and tarragon was reported.

Lilian Regina Barros, Mariutti; Gisela Pizarro de Mattos, Barreto; Neura, Bragagnolo; Adriana Zerlotti, Mercadante.

1225-12-01

127

Free radical scavenging activity of ethanolic extracts from herbs and spices commercialized in Brazil  

Directory of Open Access Journals (Sweden)

Full Text Available Ethanolic extracts from 23 different dried herbs and spices commercialized in Brazil were investigated for their free radical scavenging properties using the stable free radicals 2,2'-diphenyl-?-picrylhydrazyl (DPPH• and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS•+, and Trolox as reference (TEAC for both radicals. The kinetic curves for both radicals showed to follow the first order kinetics model and the decay rate constant (k obs was calculated. For all the samples, the two methods showed a good linear TEAC correlation, indicating that the average reactivity of the compounds present in the ethanolic extracts was similar. Sage and rosemary extracts showed the highest free radical scavenging capacities, while onion showed negligible activity and colorifico, one of the most consumed spices in Brazil, showed low ABTS•+ scavenging activity. Three distinct situations were found for the extracts concerning the DPPH• scavenging capacities: (1 extracts, like rosemary and laurel, that presented the same efficient concentrations (EC50 but differed in the TEAC values and velocities of action (k obs, (2 extracts, such as garlic and basil, that showed similar EC50 and TEAC values, but different k obs values and (3 extracts that reacted at the same velocities but completely differed in the free radical scavenging capacities, like black pepper, savory, nutmeg, rosemary and sage. Similar considerations could be done for the ABTS•+ results. For the first time the ABTS•+ scavenging activity for allspice, basil, cardamom, chives, colorifico, cumin, dill, laurel, marjoram, parsley and tarragon was reported.Extratos etanólicos de 23 ervas e condimentos desidratados comercializados no Brasil foram analisados quanto as suas propriedades antioxidantes utilizando os radicais 2,2'-difenil-?-picrilhidrazil (DPPH• e ácido 2,2'-azino-bis(3-etilbenzotiazolina-6-sulfônico (ABTS•+, Trolox foi usado como referência para ambos radicais. As curvas cinéticas seguiram o modelo cinético de primeira ordem, e a partir destas foram calculadas as constantes de velocidade de (k obs. Os extratos de sálvia e de alecrim apresentaram as maiores capacidades redutoras de radicais livres, enquanto o extrato de cebola praticamente não apresentou atividade e o colorífico, um dos condimentos mais consumidos no Brasil, apresentou baixa atividade de aprisionamento de radicaisABTS•+. Três situações distintas foram observadas em relação à capacidade de aprisionar radicais DPPH•: (1 extratos, como os de alecrim e de louro, que apresentaram as mesmas concentrações eficientes (EC50, porém, valores de TEAC e velocidade de ação (k obs distintos ; (2 extratos, como os de alho e de manjericão, que apresentaram valores similares de EC50 e TEAC, com valores distintos de k obs e (3 extratos com a mesma velocidade de ação que diferiram totalmente na capacidade de aprisionamento de radicais livres, como de pimenta preta, segurelha, noz moscada, alecrim e sálvia. Considerações semelhantes podem ser feitas para os resultados de ABTS•+. Osdois métodos apresentaram boa correlação de TEAC, indicando que a reatividade dos compostos presentes nos extratos etanólicos foi similar. A atividade redutora de ABTS•+ para pimenta da Jamaica, manjericão, cardamomo, cebolinha, colorífico, cominho, dill, louro, manjerona, salsinha e estragão foi reportada pela primeira vez.

Lilian Regina Barros Mariutti

2008-12-01

128

Radical-Scavenging Activity of Thiols, Thiobarbituric Acid Derivatives and Phenolic Antioxidants Determined Using the Induction Period Method for Radical Polymerization of Methyl Methacrylate  

OpenAIRE

The radical-scavenging activities of two thiols, eight (thio)barbituric acid derivatives and six chain-breaking phenolic antioxidants were investigated using the induction period method for polymerization of methyl methacrylate (MMA) initiated by thermal decomposition of 2,2’-azobisisobutyronitrile (AIBN) and monitored by differential scanning calorimetry (DSC). The induction period (IP) for the thiols 2-mercaptoethanol (ME) and 2-mercapto-1-methylimidazole (MMI) was about half that for phe...

Seiichiro Fujisawa; Yoshinori Kadoma

2012-01-01

129

Radical scavenging and amino acid profiling of wedge clam, Donax cuneatus (Linnaeus) protein hydrolysates.  

Science.gov (United States)

Body, foot and viscera of Donax cuneatus (Linnaeus) were hydrolyzed using commercial proteases (pepsin, trypsin and papain) and tested for their antioxidant activity by DPPH scavenging ability and reducing power assays. In comparison between all the hydrolysates, papain viscera (28.513?±?0.165 & 0.186?±?0.008) and foot (33.567?±?0.132 & 0.166?±?0.013) hydrolysates showed highest DPPH and reducing power ability respectively. The active hydrolysates were purified with DEAE- cellulose followed by Sephadex G-25 columns connected to FPLC. Further, the isolated active fractions were loaded onto HPLC for their amino acid profiling and found with the presence of potential amino acids viz., histidine, cysteine, alanine etc. These results suggest that the isolated antioxidant peptide from viscera and foot hydrolysate of D. cuneatus can be used in treating human diseases where free radicals and oxidative damage are involved. PMID:25477664

Nazeer, R A; Saranya, M A V; Naqash, Shabeena Yousuf

2014-12-01

130

Lipoxygenase-mediated pro-radical effect of melatonin via stimulation of arachidonic acid metabolism  

International Nuclear Information System (INIS)

We have shown that melatonin immediately and transiently stimulates intracellular free radical production on a set of leukocytes, possibly as a consequence of calmodulin binding. We show here that melatonin-induced ROS are produced by lipoxygenase (LOX), since they are prevented by a set of LOX inhibitors, and are accompanied by increase of the 5-LOX product 5-HETE. LOX activation is accompanied by strong liberation of AA; inhibition of Ca2+-independent, but not Ca2+-dependent, phospholipase A2 (PLA2), prevents both melatonin-induced arachidonic acid and ROS production, whereas LOX inhibition only prevents ROS, indicating that PLA2 is upstream with respect to LOX, as occurs in many signaling pathways. Chlorpromazine, an inhibitor of melatonin-calmodulin interaction, inhibits both ROS and arachidonic acid production, thus possibly placing calmodulin at the origin of a melatonin-induced pro-radical pathway. Interestingly, it is known that Ca2+-independent PLA2 binds to calmodulin: our results are compatible with PLA2 being liberated by melatonin from a steady-state calmodulin sequestration, thus initiating an arachidonate signal transduction. These results delineate a novel molecular pathway through which melatonin may participate to the inflammatory response.

131

Electron spin resonance studies of barriers to hindered rotation in acetic acid, acetamide, and peptide radicals  

International Nuclear Information System (INIS)

Activation energies for methyl group rotation in the radicals of type H3C-C2O) as well as in 8 M NaOD glasses have produced the acetic acid anion, the acetate dianion, and the acetamide anion. ESR spectra of these have revealed a doublet (ca. 32G) at 90 K reversibly interconverting to a 1:3:3:1 quartet, of ca. 15-G hyperfine splitting, at higher temperatures (170 K). This interconversion has been attributed to the hindered internal rotation of the methyl group about the H3C-C< bond. The ESR spectra are analyzed using modified Bloch equations for the three-jump process. The mean lifetime (tau) at each temperature (T) has been estimated by a comparison of experimental and simulated ESR spectra. The activation energy (E/sub a/) for the sixfold barrier to the rotation is found to be 5.0 +- 0.5 kcal/mol in the acetate dianion and is about 3.0 kcal/mol for the acetate and acetamide as well as N-acetylamino acids. ESR spectra characteristic of the tunneling methyl group were observed at low temperature (20 K< T<100K) for the radicals produced in ?-irradiated polycrystalline samples of glycyl-L-alanine and L-alanyl-L-alanine. 3 figures, 1 table

132

Quassinoid support studies: fused carbocycle synthesis from benzoic acid derivatives via 5-hexynyl and 6-heptynyl radical cyclizations.  

Science.gov (United States)

Eight bromoalkynes were prepared from substituted benzoic acids and treated with n-Bu3SnH to provide trans-fused perhydroindans or cis- and trans-fused perhydronaphthalenes. Atom-transfer reactions that accompany the free radical reactions resulted in several tandem radical cyclizations with formation of up to three carbon-carbon bonds in a single reaction. The relationship between these reactions and an approach to the quassinoid family of natural products is also described. PMID:16986954

Cwynar, Valerie; Donahue, Matthew G; Hart, David J; Yang, Dexi

2006-09-28

133

A Perspective on Free Radical Autoxidation: The Physical Organic Chemistry of Polyunsaturated Fatty Acid and Sterol Peroxidation  

OpenAIRE

This Perspective describes advances from the author’s laboratory on the free radical reactions of organic compounds with molecular oxygen. Polyunsaturated fatty acids (PUFAs) and sterols are particularly prone to undergo radical chain oxidation and evidence suggests that this process, known as lipid peroxidation, occurs in vivo under a variety of conditions that are the result of an oxidative stress. Cyclic peroxides, hydroperoxides, and epoxy-alcohols are major products formed from peroxid...

Porter, Ned A.

2013-01-01

134

The Comparative Ability of Antioxidant Activity of Piper crocatum in Inhibiting Fatty Acid Oxidation and Free Radical Scavenging  

OpenAIRE

The excessive number of free radicals in human body could increase lipid peroxides and causes a variety of degenerative diseases. Piper crocatum is a plant containing natural chemicals that may have an antioxidant ability to inhibit fatty acid oxidation and reduce free radicals, however, there is no published scientific reports up to now. Therefore, the objective of this research is to study the ability of ethanol extract of P. crocatum as an antioxidant. The leaves of P. crocatum (25 g) were...

MUHAMMAD ALFARABI; MARIA BINTANG; SURYANI; MEGA SAFITHRI

2010-01-01

135

Interaction of aromatic alcohols, aldehydes and acids with ?-hydroxyl-containing carbon-centered radicals: A steady state radiolysis study  

Science.gov (United States)

Benzaldehyde and its derivatives efficaciously oxidize in aqueous solutions ?-hydroxyl-containing carbon-centered radicals (?-HCR) of various structures, suppressing thereby the radical recombination and fragmentation reactions. The compounds containing cinnamic moieties are capable of adding ?-hydroxyethyl radicals (?-HER) to the carbon-carbon double bonds conjugated with the aromatic system to form molecular products identifiable by mass spectrometry. On radiolysis of aqueous ethanol solutions, reduction of ?-HER by aromatic alcohols and acids has been shown to proceed via formation of their adducts with hydrated electron species.

Samovich, S. N.; Brinkevich, S. D.; Shadyro, O. I.

2013-01-01

136

Repeated dosing of ABT-102, a potent and selective TRPV1 antagonist, enhances TRPV1-mediated analgesic activity in rodents, but attenuates antagonist-induced hyperthermia.  

Science.gov (United States)

Transient receptor potential vanilloid type 1 (TRPV1) is a ligand-gated ion channel that functions as an integrator of multiple pain stimuli including heat, acid, capsaicin and a variety of putative endogenous lipid ligands. TRPV1 antagonists have been shown to decrease inflammatory pain in animal models and to produce limited hyperthermia at analgesic doses. Here, we report that ABT-102, which is a potent and selective TRPV1 antagonist, is effective in blocking nociception in rodent models of inflammatory, post-operative, osteoarthritic, and bone cancer pain. ABT-102 decreased both spontaneous pain behaviors and those evoked by thermal and mechanical stimuli in these models. Moreover, we have found that repeated administration of ABT-102 for 5-12 days increased its analgesic activity in models of post-operative, osteoarthritic, and bone cancer pain without an associated accumulation of ABT-102 concentration in plasma or brain. Similar effects were also observed with a structurally distinct TRPV1 antagonist, A-993610. Although a single dose of ABT-102 produced a self-limiting increase in core body temperature that remained in the normal range, the hyperthermic effects of ABT-102 effectively tolerated following twice-daily dosing for 2 days. Therefore, the present data demonstrate that, following repeated administration, the analgesic activity of TRPV1 receptor antagonists is enhanced, while the associated hyperthermic effects are attenuated. The analgesic efficacy of ABT-102 supports its advancement into clinical studies. PMID:19135797

Honore, Prisca; Chandran, Prasant; Hernandez, Gricelda; Gauvin, Donna M; Mikusa, Joseph P; Zhong, Chengmin; Joshi, Shailen K; Ghilardi, Joseph R; Sevcik, Molly A; Fryer, Ryan M; Segreti, Jason A; Banfor, Patricia N; Marsh, Kennan; Neelands, Torben; Bayburt, Erol; Daanen, Jerome F; Gomtsyan, Arthur; Lee, Chih-Hung; Kort, Michael E; Reilly, Regina M; Surowy, Carol S; Kym, Philip R; Mantyh, Patrick W; Sullivan, James P; Jarvis, Michael F; Faltynek, Connie R

2009-03-01

137

A perspective on free radical autoxidation: the physical organic chemistry of polyunsaturated fatty acid and sterol peroxidation.  

Science.gov (United States)

This Perspective describes advances from the author's laboratory on the free radical reactions of organic compounds with molecular oxygen. Polyunsaturated fatty acids (PUFAs) and sterols are particularly prone to undergo radical chain oxidation, and evidence suggests that this process, known as lipid peroxidation, occurs in vivo under a variety of conditions that are the result of an oxidative stress. Cyclic peroxides, hydroperoxides, and epoxy alcohols are major products formed from peroxidation, and the basic mechanisms of product formation are now reasonably well understood. These mechanisms include reversible addition of oxygen to carbon radicals, rearrangement and cyclization of allyl and pentadienyl peroxyl radicals, and homolytic substitution of carbon radicals on the peroxide bond. A physical organic approach to the problem of free radicals in biology and medicine is highlighted in this Perspective with stereochemical, kinetic, and extrathermodynamic probes applied to the study of mechanism. A radical clock permits the determination of free radical propagation rate constants, and 7-dehydrocholesterol, the immediate biosynthetic precursor of cholesterol, is found by this clock to be one of the most oxidizable lipids known. The consequences of the extreme reactivity of 7-dehydrocholesterol on human health is the focus of a current research theme in the author's laboratory. PMID:23445181

Porter, Ned A

2013-04-19

138

Mechanisms leading to oligomers and SOA through aqueous photooxidation: insights from OH radical oxidation of acetic acid  

Science.gov (United States)

Previous experiments have demonstrated that the aqueous OH radical oxidation of methylglyoxal produces low volatility products including oxalate and oligomers. These products are found predominantly in the particle phase in the atmosphere, suggesting that methylglyoxal is a precursor of secondary organic aerosol (SOA). Acetic acid is an important intermediate in aqueous methylglyoxal oxidation and a ubiquitous product of gas phase photochemistry, making it a potential "aqueous" SOA precursor in its own right. Altieri et al. (2008) proposed that acetic acid was the precursor of oligoesters observed in methylglyoxal oxidation. However, the fate of acetic acid upon aqueous-phase oxidation is not well understood. In this research, acetic acid at concentrations relevant to atmospheric waters (20 ?M-10 mM) was oxidized by OH radical. Products were analyzed by ion chromatography (IC), electrospray ionization mass spectrometry (ESI-MS), and IC-ESI-MS. The formation of glyoxylic, glycolic, and oxalic acids were observed. In contrast to methylglyoxal oxidation, succinic acid and oligomers were not detected. Using results from these and methylglyoxal + OH radical experiments, radical mechanisms responsible for oligomer formation from methylglyoxal oxidation in clouds and wet aerosols are proposed. The importance of acetic acid/acetate as an SOA precursor is also discussed. We hypothesize that this and similar chemistry is central to the daytime formation of oligomers in wet aerosols.

Tan, Y.; Lim, Y. B.; Altieri, K. E.; Seitzinger, S. P.; Turpin, B. J.

2011-06-01

139

Intraoperative use of tranexamic acid to reduce transfusion rate in patients undergoing radical retropubic prostatectomy: double blind, randomised, placebo controlled trial  

OpenAIRE

Objectives To determine the efficacy of intraoperative treatment with low dose tranexamic acid in reducing the rate of perioperative transfusions in patients undergoing radical retropubic prostatectomy.

Crescenti, Antonella; Borghi, Giovanni; Bignami, Elena; Bertarelli, Gaia; Landoni, Giovanni; Casiraghi, Giuseppina Maria; Briganti, Alberto; Montorsi, Francesco; Rigatti, Patrizio; Zangrillo, Alberto

2011-01-01

140

Fundamental model assays on chemical damages to ribonucleic acids in aqueous solution caused by oxygen radicals  

International Nuclear Information System (INIS)

A partial decomposition of RNA molecules in Saccharomyces cerevisiae is caused by photochemically produced superoxide anion radical (O2.-). Hydroxyl radicals (OH.) lead to complete destruction of RNA. Such radicals as originating from peroxidase-hydrogen peroxide reaction cause a partial decomposition of RNA molecules. All RNA species are damaged to the same extent by radicals. Damages due to oxygen radicals can be prevented or reduced by strong radical captors (dimethyl sulfoxide, 1,4-diazabicyclo-(2,2,2)-octane or superoxide dismutase). All these reactions proceed in aqueous solution. Correlations with the use of radicals in radiotherapy are discussed. (orig.)

141

Atmospheric chemistry of perfluorinated carboxylic acids: Reaction with OH radicals and atmospheric lifetimes  

DEFF Research Database (Denmark)

Relative rate techniques were used to study the kinetics of the reactions of OH radicals with a homologous series of perfluorinated acids, F(CF2)(n)COOH (n = 1, 2, 3, 4), in 700 Torr of air at 296 +/- 2 K. For n > 1, the length of the F(CF2)(n) group had no discernible impact on the reactivity of the molecule. For n = 1, k(OH + F(CF2)(n)COOH) = (9.35 +/- 2.08) x 10(-14) cm(3) molecule(-1) s(-1). For n = 2-4, k(OH + F(CF2)(n)COOH) = (1.69 +/- 0.22) x 10(-13) cm(3) molecule(-1) s(-1). Dimerization constants for 2F(CF2)(n)COOH = (F(CF2)(n)COOH)(2) were determined to be 0.32 +/- 0.03 Torr(-1), 0.30 +/- 0.03 Torr(-1), 0.41 +/- 0.04 Torr(-1), and 0.46 +/- 0.05 Torr(-1) for n = 1, 2, 3. 4, respectively. Atmospheric lifetimes of F(CF2)(n)COOH with respect to reaction with OH radicals are estimated to be approximately 230 days for n = 1 and 130 days for n > 1. Reaction with OH radicals is a minor atmospheric fate of F(CF2)(n)COOH. The major atmospheric removal mechanism for F(CF2)(n)COOH is believed to be wet and dry deposition which probably occurs on a time scale of the order of 10 days.

Hurley, MD; Andersen, Mads Peter Sulbæk

2004-01-01

142

Brønsted Acid Co-catalysts in Photocatalytic Radical Addition of ?-Amino C–H Bonds Across Michael Acceptors  

Science.gov (United States)

In marked contrast to the variety of strategies available for oxidation and nucleophilic functionalization of methylene groups adjacent to amines, relatively few approaches for modification of this position with electrophilic reaction partners have been reported. In the course of an investigation of the reactions of photogenerated ?-amino radicals with electrophiles, we made the surprising observation that the efficiency of radical photoredox functionalization of N-aryl tetrahydroisoquinolines is dramatically increased in the presence of a Brønsted acid co-catalyst. Optimized conditions provide high yields and efficient conversion to radical addition products for a range of structurally modified tetrahydroisoquinolines and enones using convenient household light sources and commercially available Ru(bpy)3Cl2 as a photocatalyst. Our investigations into the origins of this unexpected additive effect have demonstrated that the carbon–carbon bond-forming step is accelerated by TFA and is a rare example of Brønsted acid catalysis in radical addition reactions. Moreover, a significant conclusion arising from these studies is the finding that product formation is dominated by radical chain processes and not by photocatalyst turnover. Together, these findings have important implications for the future design and mechanistic evaluation of photocatalytic radical processses. PMID:23537318

Espelt, Laura Ruiz; Wiensch, Eric M.; Yoon, Tehshik P.

2013-01-01

143

Free radical reaction pathway, thermohemistry of peracetic acid homolysis and its application for phenol degradation: spectroscopic sti=udy and quantum chemistry calculations  

OpenAIRE

The homolysis of peracetic acid (PAA) as a relevant source of free radicals (e.g., •OH) was studied in detail. Radicals formed as a result of chain radical reactions were detected with electron spin resonance and nuclear magnetic resonance spin trapping techniques and subsequently identified by means of the simulation-based fitting approach. The reaction mechanism, where a hydroxyl radical was a primary product of O?O bond rupture of PAA, was established with a complete assessment of rele...

Rokhina, E. V.; Makarova, K.; Golovina, E. A.; As, H.; Virkutyte, J.

2010-01-01

144

Radical kinetics and dosimetric features of gamma-irradiated disodium ethylenediaminetetraacetic acid  

Energy Technology Data Exchange (ETDEWEB)

Dosimetric potential and kinetic features of disodium ethylenediaminetetraacetic acid (NaEDTA) were explored through a detail electron spin resonance (ESR) study performed at various temperatures on samples irradiated at various radiation doses. Irradiated NaEDTA was observed to exhibit an unresolved ESR spectrum consisting of many intense and weak resonance lines spread over a magnetic field range of about 7 mT and centered at g=2.00275. Findings derived from applied microwave power, long term storage investigation, and high and low temperature studies indicate that two radicals were formed after the irradiations. The spectroscopic parameters of these radicals were determined through spectrum simulation calculations. The dosimetric potential of NaEDTA was also investigated and it was concluded that NaEDTA does not present the characteristics of a good dosimetric material, but that ESR spectroscopy could be used in the discrimination of irradiated NaEDTA from the unirradiated one even long after irradiation. Activation energies of the involved species were also determined using the data derived from annealing studies performed at high temperatures.

Tuner, H., E-mail: htuner@hacettepe.edu.t [Department of Physics, Faculty of Science, Balikesir University, Cagis, 10145 Balikesir (Turkey)

2011-06-15

145

Caffeic Acid Inhibits the Formation of 7-Carboxyheptyl Radicals from Oleic Acid under Flavin Mononucleotide Photosensitization by Scavenging Singlet Oxygen and Quenching the Excited State of Flavin Mononucleotide  

Directory of Open Access Journals (Sweden)

Full Text Available We examined the effects of caffeic acid (CA and related compounds on 7-carboxyheptyl radical formation. This analysis was performed using a standard D2O reaction mixture containing 4.3 mM oleic acid, 25 ?M flavin mononucleotide (FMN, 160 mM phosphate buffer (pH 7.4, 10 mM cholic acid, 100 mM ?-(4-pyridyl-1-oxide-N-tert-butylnitrone, and 1 mM Fe(SO42(NH42 during irradiation with 7.8 J/cm2 at 436 nm. 7-Carboxyheptyl radical formation was inhibited by CA, catechol, gallic acid, chlorogenic acid, ferulic acid, noradrenalin, 2-hydroxybenzoic acid, 3-hydroxybenzoic acid, and 4-hydroxybenzoic acid. Quinic acid, benzoic acid, and p-anisic acid had no effect on radical formation. These results suggest that a phenol moiety is essential for these inhibitory effects. The fluorescence intensity of FMN decreased by 69% ± 2% after CA addition, suggesting that CA quenches the singlet excited state of FMN. When 1 mM CA was added to a standard reaction mixture containing 25 ?M FMN, 140 mM phosphate buffer (pH 7.4, and 10 mM 4-oxo-2,2,6,6-tetramethylpiperidine, the electron spin resonance signal of 4-oxo-2,2,6,6-tetramethylpiperidinooxy disappeared. This finding suggests that singlet oxygen was scavenged completely by CA. Therefore, CA appears to inhibit 7-carboxyheptyl radical formation by scavenging singlet oxygen and quenching the excited state of FMN.

Marie Asano

2014-08-01

146

Caffeic acid inhibits the formation of 7-carboxyheptyl radicals from oleic acid under flavin mononucleotide photosensitization by scavenging singlet oxygen and quenching the excited state of flavin mononucleotide.  

Science.gov (United States)

We examined the effects of caffeic acid (CA) and related compounds on 7-carboxyheptyl radical formation. This analysis was performed using a standard D2O reaction mixture containing 4.3 mM oleic acid, 25 ?M flavin mononucleotide (FMN), 160 mM phosphate buffer (pH 7.4), 10 mM cholic acid, 100 mM ?-(4-pyridyl-1-oxide)-N-tert-butylnitrone, and 1 mM Fe(SO4)2(NH4)2 during irradiation with 7.8 J/cm2 at 436 nm. 7-Carboxyheptyl radical formation was inhibited by CA, catechol, gallic acid, chlorogenic acid, ferulic acid, noradrenalin, 2-hydroxybenzoic acid, 3-hydroxybenzoic acid, and 4-hydroxybenzoic acid. Quinic acid, benzoic acid, and p-anisic acid had no effect on radical formation. These results suggest that a phenol moiety is essential for these inhibitory effects. The fluorescence intensity of FMN decreased by 69%±2% after CA addition, suggesting that CA quenches the singlet excited state of FMN. When 1 mM CA was added to a standard reaction mixture containing 25 ?M FMN, 140 mM phosphate buffer (pH 7.4), and 10 mM 4-oxo-2,2,6,6-tetramethylpiperidine, the electron spin resonance signal of 4-oxo-2,2,6,6-tetramethylpiperidinooxy disappeared. This finding suggests that singlet oxygen was scavenged completely by CA. Therefore, CA appears to inhibit 7-carboxyheptyl radical formation by scavenging singlet oxygen and quenching the excited state of FMN. PMID:25153866

Asano, Marie; Iwahashi, Hideo

2014-01-01

147

Synergistic interaction between the probucol phenoxyl radical and ascorbic acid in inhibiting the oxidation of low density lipoprotein.  

Science.gov (United States)

Chain-breaking antioxidants such as butylated hydroxytoluene, alpha-tocopherol, and probucol have been shown to decrease markedly the oxidative modification of low density lipoprotein (LDL). Their mechanism of action appears to involve scavenging of LDL-lipid peroxyl radicals. The purpose of this study was to investigate the occurrence of radical reactions produced during oxidation of LDL and LDL-containing probucol initiated by lipoxygenase or copper. In addition, we have investigated the possibility of a synergistic interaction between ascorbate and probucol in inhibiting the oxidation of LDL. Incubation of LDL-containing probucol and lipoxygenase produced a composite electron spin resonance (ESR) spectrum due to the endogenous alpha-tocopheroxyl radical and probucol-derived phenoxyl radical. The spectral assignment was further verified by chemical oxidation of alpha-tocopherol and probucol. In the presence of ascorbic acid, these radicals in the LDL particle were reduced to their parent compounds with concomitant formation of the ascorbate radical. In both the peroxidation of linoleic acid and the copper-initiated peroxidation of LDL, the antioxidant activity of probucol was significantly increased by low (3-6 microM) concentrations of ascorbate. The probucol-dependent inhibition of LDL oxidation was enhanced in the presence of ascorbic acid. We conclude that the reaction between the phenoxyl radical of probucol and ascorbate results in a synergistic enhancement of the antioxidant capacity of these two compounds and speculate that such reactions could play a role in maintaining the antioxidant status of LDL during oxidative stress in vivo. PMID:1313022

Kalyanaraman, B; Darley-Usmar, V M; Wood, J; Joseph, J; Parthasarathy, S

1992-04-01

148

Sodium nitrite and ascorbic acid: a metal-free combination that controls the free-radical polymerization of tert-butyl methacrylate in water  

OpenAIRE

A mixture of sodium nitrite and ascorbic acid is able to control the radical polymerization of tert-butyl methacrylate (tBMA) in water at 80°C. Indeed, sodium nitrite is reduced by the ascorbic acid, and the nitric oxide (NO) which is formed in situ is nothing but a promoter of nitroxyl radicals. The radical polymerization of tBMA is thus basically controlled by a nitroxide-mediated process.

Detrembleur, Christophe; Mouithys-mickalad, Ange; Teyssie?, Philippe; Je?ro?me, Robert

2002-01-01

149

Reaction of hypochlorite with amino acids and peptides : EPR evidence for rapid rearrangement and fragmentation of nitrogen-centred radicals  

International Nuclear Information System (INIS)

Various amino acid side chains have been shown to be particularly susceptible to attack and modification by hypochlorite (HOCl). It is known that tyrosine is readily chlorinated by HOCl to give 3-chlorotyrosine and this product has been employed as a marker of HOCl-mediated damage to proteins. Cysteine and methionine react rapidly with HOCl to give oxy acids and cystine (from cysteine) and sulphoxides (from methionine). Lysine and amino acids which lack the above functional groups also react with HOCl via the free amino group which results in the generation of unstable chloramine intermediates; subsequent decomposition of these species gives NH3, CO2 and aldehydes. While the products of reaction of HOCl with amino acids and peptides are reasonably well characterised, the mechanism(s) by which these products arise is less well understood. Electron paramagnetic resonance (EPR) spectroscopy with spin trapping and UV/visible spectroscopy has been employed to examine the reaction of HOCl with amino acids and some small peptides. Reaction of HOCl with N-acetyl amino acids or small peptides gives radicals predominantly at ?-carbon sites via reaction at N-terminal free amino groups or amide (peptide) bonds. It is proposed that these carbon-centred radicals are produced as a result of the rearrangement of initial nitrogen-centred radicals formed on cleavage of the N-CI bond of the chloramine/chloramide species by a 1,2-shift reactiona 1,2-shift reaction

150

Molecular Dynamics Simulations of Arachidonic Acid-Derived Pentadienyl Radical Intermediate Complexes with COX-1 and COX-2  

Science.gov (United States)

The two cyclooxygenase enzymes, COX-1 and COX-2, are responsible for the committed step in prostaglandin biosynthesis, and are the targets of the non-steroidal anti-inflammatory drugs aspirin, ibuprofen and the COX-2 selective inhibitors, Celebrex™, Vioxx™ and Bextra™. The enzymes are remarkable in that they catalyze two dioxygenations and two cyclizations of the native substrate, arachidonic acid, with near absolute regio- and stereoselectivity. Several theories have been advanced to explain the nature of enzymatic control over this series of reactions, including suggestions of steric shielding and oxygen channeling. As proposed here, selective radical trapping and spin localization in the substrate-derived pentadienyl radical intermediate can also be envisioned. Herein we describe the results of explicit, 10 ns molecular dynamics simulations of both COX-1 and COX-2 with the substrate-derived pentadienyl radical intermediate bound in the active site. The enzymes’ influence on the conformation of the pentadienyl radical was investigated, along with the accessible space above and below the radical plane, and the width of several channels to the active site that could function as access routes for molecular oxygen. Additional simulations demonstrated the extent of molecular oxygen mobility within the active site. The results suggest that spin localization is unlikely to play a role in enzymatic control of this reaction. Instead, a combination of oxygen channeling, steric shielding and selective radical trapping appears to be responsible. This work adds a dynamic perspective to the strong foundation of static structural data available for these enzymes. PMID:16519515

Furse, Kristina E.; Pratt, Derek A.; Schneider, Claus; Brash, Alan R.; Porter, Ned A.; Lybrand, Terry P.

2008-01-01

151

Bovine rod rhodopsin. 1. Bleaching by luminescence in vitro by recombination of radicals from polyunsaturated fatty acids.  

Science.gov (United States)

Rod outer segments of photoreceptors are characterized by rhodopsin, a membrane protein surrounded by phospholipids containing a very high concentration of polyunsaturated fatty acids. These fatty acids can propagate free radicals, initiated by peroxidation, whose recombination is eventually associated with light emission as chemiluminescence. The results reported here indicate that this effect produces an isomerization of the retinal (bleaching effect) of the rhodopsin, similar to that induced by light in normal vision. In vitro experiments on detergent-suspended rod outer segments (RdOS) from bovine eyes, using an enzymatic source of radicals, xanthine/xanthine oxidase, were carried out. The results indicate that the proposed mechanism is likely, because they can show the bleaching of rhodopsin in RdOS, owing to its extraordinary sensitivity. Thus this mechanism is, also, a possible explanation for anomalous visual effects such as light flashes (phosphene-like) perceived by humans. The functionality of the rhodopsin in the RdOS was first tested by visible light. Rhodopsin reactivation after bleaching was obtained by adding cis-retinal to the suspension, demonstrating the reversibility of the bleaching process. A special experimental system was developed to observe the bleaching from luminescence by radical recombination, avoiding physical contact between the rod outer segment suspension and the radicals to prevent radical-induced damage and modifications of the delicate structure of the rod outer segment. PMID:22634396

Narici, L; Paci, M; Brunetti, V; Rinaldi, A; Sannita, W G; De Martino, A

2012-08-01

152

The formation and reaction of methyl radicals produced by direct photolysis of aqueous solutions of N-acetyl substituted aliphatic amino acids at 77 K  

International Nuclear Information System (INIS)

Photolysis of amino acids, peptides and their derivatives leads to the formation of free radicals in these substances. The electron-spin-resonance spectra obtained directly after irradiation at 77 K were not very well resolved. They were recognizable as the superposition of the spectra of different types of photoproduced radicals. CH3 radicals are formed by U.V. irradiation if methyl groups are present in the molecule. These radicals were easily detectable because of their four line spectrum. The formation of methyl radicals and their reaction with undamaged molecules of N-acetyl-substituted amino acids have been investigated. The number of CH3 radicals present after a 30 min U.V. irradiation was higher if preceding U.V. irradiations and heat treatments were performed. The overall concentration of radicals was reduced only partially during this heat-treatment, while the CH3 radicals decayed completely. Other experiments showed that the rate of and the yield of CH3 radicals by U.V. irradiation increased with the dose of a preceding ?-irradiation. The results suggest that there are substances present which are responsible for the higher production rate of methyl radicals after a preceding treatment. It is assumed that radicals are precursors of the fast-formed CH3 radicals. (author)

153

A multiple free-radical scavenging (MULTIS) study on the antioxidant capacity of a neuroprotective drug, edaravone as compared with uric acid, glutathione, and trolox.  

Science.gov (United States)

Edaravone (3-methyl-1-phenyl-2-pyrazoline-5-one) is a neuroprotective drug that has been used for brain ischemia injury treatment. Because its activity is speculated to be due to free radical scavenging activity, we carried out a quantitative determination of edaravone's free radical scavenging activity against multiple free radical species. Electron spin resonance (ESR) spin trapping-based multiple free-radical scavenging (MULTIS) method was employed, where target free radicals were hydroxyl radical, superoxide anion, alkoxyl radical, alkylperoxyl radical, methyl radical, and singlet oxygen. Edaravone showed relatively high scavenging abilities against hydroxyl radical (scavenging rate constant k=2.98×10(11) M(-1) s(-1)), singlet oxygen (k=2.75×10(7) M(-1) s(-1)), and methyl radical (k=3.00×10(7) M(-1) s(-1)). Overall, edaravone's scavenging activity against multiple free radical species is as robust as other known potent antioxidant such as uric acid, glutathione, and trolox. A radar chart illustration of the MULTIS activity relative to uric acid, glutathione, and trolox indicates that edaravone has a high and balanced antioxidant activity with low specificity. PMID:24507926

Kamogawa, Erisa; Sueishi, Yoshimi

2014-03-01

154

Short term ethanol alters free radical defense and membrane fatty acid composition in micropigs  

Energy Technology Data Exchange (ETDEWEB)

The authors have suggested that ethanol (Et) metabolism may evoke a protective response by the hepatic cell including changes in free radical defense and membrane fatty acid composition resulting in less peroxidizable membranes. To test this, micropigs were fed diets containing 40% of kcals as either Et or corn starch (C) and 30% of kcals as corn oil. Liver histology was similar in both groups in biopsies taken after 1 mo of treatment. However, liver CuZn superoxide dismutase (CuZnSOD) and glutathione peroxidase activities in Et pigs were 75% of C values, while glutathione reductase and MnSOD activities were 150% of C values. Glutathione levels were higher in Et pigs than in controls. Et pigs had lower TBARS production than C pigs. The peroxidizability index (PI) was calculated from the % of mono-, di-, tri-, penta- and hexaenoic fatty acids and used as an index of substrate availability for lipid peroxidation. Consistent with lower TBARS, PIs in mitochondrial and microsomal fractions were lower in Et pigs than in C pigs. These data show that after short exposure to Et a number of enzymatic and nonenzymatic responses occur in the liver prior to the appearance of histopathology. Whether these changes are part of a compensatory response to Et metabolism or if they contribute to the pathology associated with Et intake needs to be determined.

Zidenberg-Cherr, S.; Olin, K.L.; Villanueva, J.; Tang, A.; Phinney, S.D.; Halsted, C.H.; Keen, C.L. (Univ. of California, Davis (United States))

1991-03-15

155

Photo- and radio-induced radical oxidation of the purine and pyrimidine bases of nucleic acids  

International Nuclear Information System (INIS)

Our current knowledge of the hydroxyl radical-mediated oxidations of the base moiety of the four main DNA 2'-deoxyribonucleosides, in aerated aqueous solutions, is reviewed. Included are kinetic and mechanistic aspects of transient radicals and structural features of the diamagnetic decomposition products. Another major topic addressed in this survey involves the chemical reactions of the purine and pyrimidine radical cations of the above DNA model compounds. These radicals are the main reactive intermediates of the direct effect of ionizing radiation and photosensitized reactions involving type I processes. Emphasis is placed on the similarities between the formation of oxidizing radicals via hydroxyl radical addition to the base moieties and chemical reactions of the radical cations (hydration and/or deprotonation). A survey of the main base lesions which have been characterized within isolated and cellular DNAs under conditions of oxidative stress, including exposure to ionizing radiation and various radiomimetic agents, is also presented. 97 refs

156

A pulse radiolysis investigation of the reactions of tributyl phosphate with the radical products of aqueous nitric acid irradiation.  

Science.gov (United States)

Tributyl phosphate (TBP) is the most common organic compound used in liquid-liquid separations for the recovery of uranium, neptunium, and plutonium from acidic nuclear fuel dissolutions. The goal of these processes is to extract the actinides while leaving fission products in the acidic, aqueous phase. However, the radiolytic degradation of TBP has been shown to reduce separation factors of the actinides from fission products and to impede the back-extraction of the actinides during stripping. As most previous investigations of the radiation chemistry of TBP have focused on steady state radiolysis and stable product identification, with dibutylphosphoric acid (HDBP) invariably being the major product, here we have determined room temperature rate constants for the reactions of TBP and HDBP with the hydroxyl radical [(5.00 +/- 0.05) x 10(9), (4.40 +/- 0.13) x 10(9) M(-1) s(-1)], hydrogen atom [(1.8 +/-0.2) x 10(8), (1.1 +/- 0.1) x 10(8) M(-1) s(-1)], nitrate radical [(4.3 +/- 0.7) x 10(6), (2.9 +/- 0.2) x 10(6) M(-1) s(-1)], and nitrite radical (<2 x 10 (5), <2 x 10(5) M(-1) s(-1)), respectively. These data are used to discuss the mechanism of TBP radical-induced degradation. PMID:18572898

Mincher, Bruce J; Mezyk, Stephen P; Martin, Leigh R

2008-07-17

157

Effects of gamma-ray-induced free radicals on the metal content and amino acid composition of human metallothionein-1  

International Nuclear Information System (INIS)

Metallothioneins (MTs), a low-mass class of metalloproteins, are characterized by a high thiolate sulphur and metal content. MTs are involved in metal homeostasis and heavy metal detoxification, and are efficient scavengers of free radicals. This article describes zinc release from human MT-1 and modification of its amino acid composition when subjected to free radicals generated during gamma ray radiolysis. The effect of gamma ray radiolysis of untreated and metal-depleted human MT-1 was tested under multiple aerobic and anaerobic conditions at increasing irradiation doses. Under all conditions, a rapid increase of serine in the early stages of irradiation was observed. Irradiation for longer times led to cysteic acid formation, except under argon atmosphere. Several other amino acid concentrations gradually decreased. Formation of limited amounts of hydroxyproline, hydroxylysine and ornithine as well as some less common derivatives such as cystathionine occurred as side-effects. (author)

158

Radical scavenging and antimicrobial activity of essential oil and extracts of Echinophora sibthorpiana Guss. from Macedonia  

Directory of Open Access Journals (Sweden)

Full Text Available This study was undertaken to determine the antioxidant and antimicrobial effect of essential oil and extracts of Echinophora sibthorpiana Guss. (fam. Apiaceae collected in Macedonia. The chemical composition of E. sibthorpiana essential oil was characterized by the presence of methyl eugenol (60.40%, p-cymene (11.18% and ?-phellandrene (10.23%. The free radical scavenging activity of extracts and essential oil was evaluated by DPPH and ABTS assays. The aqueous extract of aerial parts exhibited the strongest scavenging activity (IC50=1.67 mg/ml; results of the ABTS test showed that the most effective was the ethanol extract of aerial parts (1.11 mg vit. C/g. The essential oil showed stronger antioxidant activity compared to hydroxyanisole, ascorbic acid and quercetin that were used in the DPPH and ABTS tests, respectively. The total phenolic and flavonoid concentrations in the extracts ranged between 38.65-60.72 mg GA/g, and 3.15-19.00 mg Qu/g, respectively. The antimicrobial properties of the extracts and essential oil were investigated using a micro-well dilution technique against human pathogenic strains. The results were comparable with the effects of the positive controls, streptomycin and fluconazole. These findings indicate that E. sibthorpiana extracts and oil can be used in preventive treatments and as an alternative for synthetic preservatives. [Projekat Ministarstva nauke Republike Srbije, br. 173029 i br. 173021

Mileski Ksenija

2014-01-01

159

Dimers in ?-pinene secondary organic aerosol: effect of hydroxyl radical, ozone, relative humidity and aerosol acidity  

Science.gov (United States)

The formation of secondary organic aerosol (SOA) from both ozonolysis and hydroxyl radical (OH)-initiated oxidation of ?-pinene under conditions of high nitric oxide (NO) concentrations with varying relative humidity (RH) and aerosol acidity was investigated in the University of North Carolina dual outdoor smog chamber facility. SOA formation from ozonolysis of ?-pinene was enhanced relative to that from OH-initiated oxidation in the presence of initially high-NO conditions. However, no effect of RH on SOA mass was evident. Ozone (O3)-initiated oxidation of ?-pinene in the presence of ammonium sulfate (AS) seed coated with organic aerosol from OH-initiated oxidation of ?-pinene showed reduced nucleation compared to ozonolysis in the presence of pure AS seed aerosol. The chemical composition of ?-pinene SOA was investigated by ultra-performance liquid chromatography/electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-Q-TOFMS), with a focus on the formation of carboxylic acids and high-molecular weight dimers. A total of eight carboxylic acids and four dimers were identified, constituting between 8 and 12% of the total ?-pinene SOA mass. OH-initiated oxidation of ?-pinene in the presence of nitrogen oxides (NOx) resulted in the formation of highly oxidized carboxylic acids, such as 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA) and diaterpenylic acid acetate (DTAA). The formation of dimers was observed only in SOA produced from the ozonolysis of ?-pinene in the absence of NOx, with increased concentrations by a factor of two at higher RH (50-90%) relative to lower RH (30-50%). The increased formation of dimers correlates with an observed increase in new particle formation at higher RH due to nucleation. Increased aerosol acidity was found to have a negligible effect on the formation of the dimers. SOA mass yield did not influence the chemical composition of SOA formed from ?-pinene ozonolysis with respect to carboxylic acids and dimers. The results support the formation of the high-molecular weight dimers through gas-phase reactions of the stabilized Criegee Intermediate (sCI) formed from the ozonolysis of ?-pinene. The high molecular weight and polar nature of dimers formed in the gas phase may explain increased particle number concentration as a result of homogenous nucleation. Since three of these dimers (i.e. pinyl-diaterpenyl dimer (MW 358), pinyl-diaterebyl dimer (MW 344) and pinonyl-pinyl dimer (MW 368)) have been observed in both laboratory-generated and ambient fine organic aerosol samples, we conclude that the dimers observed in this study can be used as tracers for the O3-initiated oxidation of ?-pinene, and are therefore indicative of enhanced anthropogenic activities, and that the high molecular weight and low volatility dimers result in homogenous nucleation under laboratory conditions, increasing the particle number concentration.

Kristensen, K.; Cui, T.; Zhang, H.; Gold, A.; Glasius, M.; Surratt, J. D.

2014-04-01

160

The Comparative Ability of Antioxidant Activity of Piper crocatum in Inhibiting Fatty Acid Oxidation and Free Radical Scavenging  

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Full Text Available The excessive number of free radicals in human body could increase lipid peroxides and causes a variety of degenerative diseases. Piper crocatum is a plant containing natural chemicals that may have an antioxidant ability to inhibit fatty acid oxidation and reduce free radicals, however, there is no published scientific reports up to now. Therefore, the objective of this research is to study the ability of ethanol extract of P. crocatum as an antioxidant. The leaves of P. crocatum (25 g were extracted with 100 ml of 70% ethanol. Antioxidant activity was measured by thiobarbituric acid method and compared with 2,2-diphenil-1-picryl hydrazyl method with ?-tocopherol as the standard antioxidant. The results showed that the extract of 200 ppm inhibited fatty acids oxidation by 80.40% and IC50 for free radical scavenging was 85.82 ppm. There was no significant different (? = 0.05 inhibition of unsaturated fatty acids oxidation between the sample and ?-tocopherol at 200 ppm. This study suggested that the leaves extract of P. crocatum has a potential natural antioxidant.

MUHAMMAD ALFARABI

2010-12-01

161

Structure and spectral studies of the BEDO-TTF radical cation salt with isocyanuric acid anion  

International Nuclear Information System (INIS)

A new radical cation salt based on bis(ethylenedioxy)tetrathiafulvalene (BEDO-TTF) and the isocyanuric acid anion (C3H2N3O3)- was synthesized and characterized by X-ray and spectral analysis. The unit cell of (BEDO-TTF)2(C3H2N3O3) is triclinic, space group P1-bar , a=3.974(1)A, b=5.429(2)A, c=18.720(7)A, ?=86.26(3)o, ?=84.65(3)o, ?=81.13(3)o. The crystal structure is layered one and the donor packing is ?-type. IR and Raman spectra of single crystals and UV-Vis-NIR absorption spectra of the sample dispersed in KBr pellet were analyzed. The normal mode vibrations and the intramolecular excitations of the neutral BEDO-TTF molecule, BEDO-TTF+ cation and (C3H2N3O3)- anion were calculated using the density functional theory. On the base of these calculations an assignment of the vibrational and electronic features in the experimental spectra was proposed. Moreover, analyzing the normal modes related to the C=C vibrations it was found that the average charge on the donor molecule is equal +0.5e

162

Caffeic acid inhibits the formation of 1-hydroxyethyl radical in the reaction mixture of rat liver microsomes with ethanol partly through its metal chelating activity  

Science.gov (United States)

Effect of caffeic acid on the formation of 1-hydroxyethyl radicals via the microsomal ethanol-oxidizing system pathway was examined. The electron spin resonance spin trapping showed that 1-hydroxyethyl radicals form in the control reaction mixture which contained 0.17 M ethanol, 1 mg protein/ml rat river microsomes, 0.1 M ?-(4-pyridyl-1-oxide)-N-tert-butylnitrone, 5 mM nicotinamide adenine dinucleotide phosphate and 30 mM phosphate buffer (pH 7.4). When the electron spin resonance spectra of the control reaction mixtures with caffeic acid were measured, caffeic acid inhibited the formation of 1-hydroxyethyl radicals in a concentration dependent manner. Gallic acid, dopamine, l-dopa, chlorogenic acid and catechin also inhibited the formation of 1-hydroxyethyl radicals. Above results indicated that the catechol moiety is essential to the inhibitory effect. Caffeic acid seems to chelate of iron ion at the catechol moiety. Indeed, the inhibitory effect by caffeic acid was greatly diminished in the presence of desferrioxamine, a potent iron chelator which removes iron ion in the Fe (III)-caffeic acid complex. Since Fe (III)-desferrioxamine complex is active for the 1-hydroxyethyl radicals formation, caffeic acid inhibits the formation of 1-hydroxyethyl radicals in the reaction mixture partly through its metal chelating activity. PMID:21562637

Ikeda, Hideyuki; Kimura, Yuka; Masaki, Miho; Iwahashi, Hideo

2011-01-01

163

Ultrafast photodissociation studies of acetyl cyanide and acetic acid and unimolecular decomposition rates of the acetyl radical products  

Science.gov (United States)

Unimolecular decomposition rates for acetyl radical following the photodissociation of acetyl cyanide and acetic acid near 193 nm have been studied using ultrafast mass-resolved photoionization spectroscopy. In both cases, the parent decays with an instrumentally limited lifetime, while the acetyl radical behaves in a manner consistent with an RRKM mechanism, in contrast to our previous results on acetone. It is necessary to convolute the population distribution with the microcanonical RRKM rates in order to achieve this agreement. We have also undertaken an ab initio study of the excited states of acetyl cyanide to clarify the assignments of these states. The state excited at 193 nm arises from a ???* transition with a calculated transition velocity dipole moment oriented at an angle of 57° with respect to the C-C?N bond, resulting in an anisotropy parameter of -0.22. This is in reasonable agreement with the previous data of North et al. [J. Phys. Chem. A 101, 9224 (1997)]. The apparent RRKM behavior of the acetyl radical formed by the photodissociation of acetic acid and acetyl cyanide indicates that acetyl radical produced by the photodissociation of acetone at 193 nm may exhibit "extrinsic non-RRKM" effects, i.e., dynamic bottlenecks or mode specific effects.

Owrutsky, J. C.; Baronavski, A. P.

1999-10-01

164

[Long-lived radicals of amino acids induced by X-ray-radiation are the source of hydrogen peroxide in aqueous medium].  

Science.gov (United States)

The formation of long-lived radicals in the solutions of casein and its hydrolysate with an equimolar mixture of amino acids was compared by measuring the X-ray-induced chemiluminescence. It was shown that free amino acids constituting the protein produce long-lived radicals. It was demonstrated that some amino acids (Leu, Ile, Val, Ser, Trp, Met, Pro, Arg, Gly, Phe) emit light of visible spectrum over a long period of time after the irradiation, which indicates the generation of long-lived radicals of these amino acids. The half-life times of these radicals are several hours. Dissolving irradiated dry amino acids capable of luminescing over a long time gives rise to the formation of hydrogen peroxide in aqueous medium. PMID:20968068

Gudkov, S V; Garmash, S A; Karp, O E; Smirnova, V S; Chernikov, A V; Bruskov, V I

2010-01-01

165

AVALIAÇÃO DA ATIVIDADE ANTIOXIDANTE DE DIFERENTES CERVEJAS APLICANDO OS MÉTODOS ABTS E DPPH  

Directory of Open Access Journals (Sweden)

Full Text Available

Os compostos fenólicos são substâncias presentes naturalmente nos vegetais que podem atuar como antioxidantes. Na cerveja desempenham um papel importante nas características sensoriais (cor, aroma e sabor e nutricionais da cerveja. O objetivo deste trabalho foi determinar o conteúdo de compostos fenólicos totais e flavonóis em diversos tipos de cervejas comercializada no Brasil, assim como determinar a capacidade antioxidante in vitro realizada por dois métodos, o radical ABTS•+ (ácido 2,2'-azino-bis (3-etilbenzotiazolin 6-sulfônico e o radical DPPH• (2,2-Difenil-1-picrilhidrazilo. Para determinar os polifenóis totais foi utilizado o método de Folin-Ciocalteau e o método DMACA para os flavanóis. Os resultados mostraram que o conteúdo de compostos fenólicos nas cervejas analisadas variou de 249,73 ± 8,44 a 808,58 ± 7,42 mg/L. A cerveja escura de trigo, apresentou os maiores valores de polifenóis totais, seguida das cervejas escura de cevada, da clara de trigo e das cervejas clara de cevada. Foram encontrados resultados significativos para atividade antioxidante aplicando o método ABTS, valores de 911,79 ± 2,21 a 3857,66 ± 6,07 Mol TEAC/L dependendo do tipo de cerveja e pelo método DPPH, de 2840,12 ± 1,09 a 4290,77± 6,19 Mol TEAC/L. O conteúdo de flavanóis (equivalente a mg catequina/L de amostra., variaram em média de 1,93 ± 0,07 mg/L a 2,79 ± 0,08 mg/L para as cervejas claras e de 2,14 ± 0,04 mg/L a 5,09 ± 0,08 mg/L para as cervejas escuras.

G. L. FREITAS

2009-01-01

166

Tests for mutagencity of free radicals formed in irradiated sugars and amino acids  

International Nuclear Information System (INIS)

Radicals formed in gamma-irradiated crystals of galactose and glycine were found, upon dissolution, to cause mutagenesis of Salmonella typhimurium strains TA-98 and TA-100. Although the reproducibility of the results has not been adequately determined, they suggest the possibility of developing a test to measure the mutagenic-carcinogenic potential of radiation-induced free radicals with a microbial system

167

Pulse radiolysis studies of short-lived species in solid amino acids as precursors of radicals detected by ESR  

International Nuclear Information System (INIS)

The aim of the study was to bring closer solid state radiation chemistry and ESR spectroscopy by looking for precursors of free radicals which give ESR signals. It has been performed using time-resolved spectrophotometry (pulse radiolysis of the solid state) and diffuse reflection spectrophotometry. Alanine has been especially considered as the most investigated amino acid, important for radiation dosimetry. Absorption of the transient (? maximum at 460 nm) is identified as the species during deamination. The stable absorption spectrum with the ? maximum at 345 nm is due to the same radical as the one detected by ESR. Other amino acids: valine, threonine, glutamine and arginine show similar behaviour: microsecond spectrum of the intermediate appears always at longer wavelengths. The transient spectrum changes into stable absorption in UV of a lower wavelength. Along with the optical spectrum, the ESR spectrum appears, of similar stability. Also, other features indicate that the same radical is responsible for both the electronic and ESR spectrum. Some amino acids, like methionine give intensive transient absorption in the microsecond range but no ESR signal, after completion of consecutive fast reactions. In that case any optical absorption is due to the stable product of radiolysis, i.e. compounds with paired electrons only. (author)

168

Spectroscopic studies on the antioxidant activity of p-coumaric acid  

Science.gov (United States)

p-coumaric acid (4-hydroxycinnamic acid), a phenolic acid, is a hydroxyl derivative of cinnamic acid. It decreases low density lipoprotein (LDL) peroxidation and reduces the risk of stomach cancer. In vitro radical scavenging and antioxidant capacity of p-coumaric acid were clarified using different analytical methodologies such as total antioxidant activity determination by ferric thiocyanate, hydrogen peroxide scavenging, 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH) scavenging, 2,2?-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging activity and superoxide anion radical scavenging, ferrous ions (Fe2+) chelating activity and ferric ions (Fe3+) reducing ability. p-Coumaric acid inhibited 71.2% lipid peroxidation of a linoleic acid emulsion at 45 ?g/mL concentration. On the other hand, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), ?-tocopherol and ascorbic acid displayed 66.8%, 69.8%, 64.5% and 59.7% inhibition on the peroxidation of linoleic acid emulsion at the same concentration, respectively. In addition, p-coumaric acid had an effective DPPHrad scavenging, ABTSrad + scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe3+) reducing power and ferrous ions (Fe2+) chelating activities. Also, those various antioxidant activities were compared to BHA, BHT, ?-tocopherol and ascorbic acid as references antioxidant compounds. These results suggested that p-coumaric acid can be used in the pharmacological and food industry because of these properties.

Kiliç, Ismail; Ye?ilo?lu, Ye?im

2013-11-01

169

Formation of radical cations and zwitterions versus demethoxylation in the reaction of OH with a series of methoxylated benzenes and benzoic acids  

International Nuclear Information System (INIS)

Using spectrophotometric and conductometric pulse radiolysis, in situ e.s.r. and product analysis techniques, the reaction of OH radicals with mono-, di- and tri-methoxylated benzenes and benzoic acids has been further studied in aqueous solution. It is found that, in addition to radical cations or zwitterions, phenoxyl radicals and methanol are formed. With the methoxylated benzenes the yield of phenoxyl radical is the same as the yield of methanol, and the sum of the yields of radical cation and of phenoxyl radical (or methanol) is approximately 100% of G(OH). The ratio of the yield of radical cation to the yield of phenoxyl radical depends on the number and on the positions of the methoxyl groups relative to each other. The yields of phenoxyl radical are low when the methoxyl groups are meta to one another, whereas the yields are high for substrates with methoxyl groups in an ortho or para relation. A similar dependence on substrate structure of the distribution of products, i.e., radical zwitterions, phenoxyl radicals and methanol, is found for methoxylated benzoic acids. The results are quantitatively interpreted in terms of electrophilic addition of OH to the aromatic ring, the positions of attachment being governed by the orthopara directing effect of the electron-donating methoxyl groups. H-abstraction from the methyl groups is negligible. The radical cations or zwitterions are derived from OH adducts formed by addition of OH to ring positions not occupied by n of OH to ring positions not occupied by methoxyl groups, whereas the phenoxyl radicals are produced by elimination of methanol (k approximately 4 x 104 s-1 at pH 7) from OH adducts formed by attachment of OH to ring carbons carrying methoxyl groups. (author)

170

Enantioselective radical addition reactions to the C=N bond utilizing chiral quaternary ammonium salts of hypophosphorous acid in aqueous media.  

Science.gov (United States)

An enantioselective addition of alkyl radicals to glyoxylate oxime ether mediated by Cinchona alkaloid derived chiral ammonium salts of hypophosphorous acid, QP and QDP, has been developed. PMID:17146522

Cho, Dae Hyan; Jang, Doo Ok

2006-12-28

171

In Vitro and In Vivo Antiviral Activity and Resistance Profile of the Hepatitis C Virus NS3/4A Protease Inhibitor ABT-450.  

Science.gov (United States)

The development of direct-acting antiviral agents is a promising therapeutic advance in the treatment of hepatitis C virus (HCV) infection. However, rapid emergence of drug resistance can limit efficacy and lead to cross-resistance among members of the same drug class. ABT-450 is an efficacious inhibitor of HCV NS3/4A protease, with 50% effective concentration values of 1.0, 0.21, 5.3, 19, 0.09, and 0.69 nM against stable HCV replicons with NS3 protease from genotypes 1a, 1b, 2a, 3a, 4a, and 6a, respectively. In vitro, the most common amino acid variants selected by ABT-450 in genotype 1 were located in NS3 at positions 155, 156, and 168, with the D168Y variant conferring the highest level of resistance to ABT-450 in both genotype 1a and 1b replicons (219- and 337-fold, respectively). In a 3-day monotherapy study with HCV genotype 1-infected patients, ABT-450 was coadministered with ritonavir, a cytochrome P450 3A4 inhibitor shown previously to markedly increase peak, trough, and overall drug exposures of ABT-450. A mean maximum HCV RNA decline of 4.02 log10 was observed at the end of the 3-day dosing period across all doses. The most common variants selected in these patients were R155K and D168V in genotype 1a and D168V in genotype 1b. However, selection of resistant variants was significantly reduced at the highest ABT-450 dose compared to lower doses. These findings were informative for the subsequent evaluation of ABT-450 in combination with additional drug classes in clinical trials in HCV-infected patients. (Study M11-602 is registered at ClinicalTrials.gov under registration no. NCT01074008.). PMID:25451053

Pilot-Matias, Tami; Tripathi, Rakesh; Cohen, Daniel; Gaultier, Isabelle; Dekhtyar, Tatyana; Lu, Liangjun; Reisch, Thomas; Irvin, Michelle; Hopkins, Todd; Pithawalla, Ron; Middleton, Timothy; Ng, Teresa; McDaniel, Keith; Or, Yat Sun; Menon, Rajeev; Kempf, Dale; Molla, Akhteruzzaman; Collins, Christine

2015-02-01

172

Free Radical Scavenging Activity of Kielmeyera variabilis (Clusiaceae  

Directory of Open Access Journals (Sweden)

Full Text Available As part of our ongoing research on antioxidant agents from Brazilian flora, we screened the free radical scavenging activity of two extracts and eight fractions of Kielmeyera variabilis (Clusiaceae using DPPH· (2,2-diphenyl-1-picrylhydrazyl-hydrate and ABTS·+ [2,2'-azinobis(3-ethylenebenzothiazoline-6-sulfonic acid] colorimetric assays. The ethyl acetate and n-butanol fractions of the leaves of K. variabilis displayed the strongest activity (IC50 of 3.5 ± 0.3 and 4.4 ± 0.2 ?g mL?1 for DPPH· and 6.6 ± 0.4 and 3.1 ± 0.1 ?g mL?1 for ABTS·+, respectively. Chromatographic fractionation of the most potent fractions led to identification of three flavonols with previously described antioxidant activity, quercitrin (1, quercetin-3-O-b-glucoside (3, and quercetin-3-O-b-galactoside (4, and of one biflavone, podocarpusflavone A (2. This is the first time that the presence of these flavonoids in Kielmeyera variabilis has been reported.

Dulce Helena Siqueira Silva

2013-02-01

173

Caracterização físico-química de polpas de frutos da Amazônia e sua correlação com a atividade anti-radical livre Physical and chemical characterization of fruit pulps from Amazonia and their correlation to free radical scavenger activity  

Directory of Open Access Journals (Sweden)

Full Text Available Características físico-químicas (cor, pH, acidez total titulável, sólidos solúveis totais, conteúdo de lipídios e umidade e níveis de compostos bioativos (ácido ascórbico, fenólicos totais foram determinados em quinze amostras de polpas de frutos procedentes da região Amazônica (abiu, acerola, açaí, araçá-boi, bacaba, bacuri, buriti, cajá, cajarana, caju, cupuaçu, graviola, murici, noni e tamarindo. A atividade de radicais livres foi avaliada pelo método de ABTS. Algumas polpas apresentaram alta potencialidade antioxidante, associada com a atividade antirradicais livres obtida e os conteúdos dos componentes bioativos como compostos fenólicos e ácido ascórbico, destacando-se acerola e acaí. O conteúdo total de compostos fenólicos foi correlacionado à capacidade antioxidante das polpas.Physical and chemical characteristics (color, pH, titratable acidity, total soluble solids, lipid content, moisture and levels of bioactive compounds (ascorbic acid, total phenolics were determined in fifteen samples of fruit pulps from Amazonia (abiu, acerola, açaí, araça-boi, bacaba, bacuri, buriti, cajá, cajarana, caju, cupuaçu, graviola, murici, noni e tamarindo. The free radical scavenger activity was evaluated by the ABTS assay. Some pulps presented high antioxidant potential, associated with the free radical scavenger activity measured and the content of bioactive components, such as phenolic compounds and ascorbic acid, especialy in acerola and açaí. The total phenolic content was correlated to antioxidant capacity of pulps.

Gisele André Baptista Canuto

2010-12-01

174

Caracterização físico-química de polpas de frutos da Amazônia e sua correlação com a atividade anti-radical livre / Physical and chemical characterization of fruit pulps from Amazonia and their correlation to free radical scavenger activity  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Características físico-químicas (cor, pH, acidez total titulável, sólidos solúveis totais, conteúdo de lipídios e umidade) e níveis de compostos bioativos (ácido ascórbico, fenólicos totais) foram determinados em quinze amostras de polpas de frutos procedentes da região Amazônica (abiu, acerola, aça [...] í, araçá-boi, bacaba, bacuri, buriti, cajá, cajarana, caju, cupuaçu, graviola, murici, noni e tamarindo). A atividade de radicais livres foi avaliada pelo método de ABTS. Algumas polpas apresentaram alta potencialidade antioxidante, associada com a atividade antirradicais livres obtida e os conteúdos dos componentes bioativos como compostos fenólicos e ácido ascórbico, destacando-se acerola e acaí. O conteúdo total de compostos fenólicos foi correlacionado à capacidade antioxidante das polpas. Abstract in english Physical and chemical characteristics (color, pH, titratable acidity, total soluble solids, lipid content, moisture) and levels of bioactive compounds (ascorbic acid, total phenolics) were determined in fifteen samples of fruit pulps from Amazonia (abiu, acerola, açaí, araça-boi, bacaba, bacuri, bur [...] iti, cajá, cajarana, caju, cupuaçu, graviola, murici, noni e tamarindo). The free radical scavenger activity was evaluated by the ABTS assay. Some pulps presented high antioxidant potential, associated with the free radical scavenger activity measured and the content of bioactive components, such as phenolic compounds and ascorbic acid, especialy in acerola and açaí. The total phenolic content was correlated to antioxidant capacity of pulps.

Gisele André Baptista, Canuto; Ana Augusta Odorissi, Xavier; Leandro Camargo, Neves; Marta de Toledo, Benassi.

1196-12-01

175

Turning on ribonucleotide reductase by light-initiated amino acid radical generation  

OpenAIRE

Ribonucleotide reductases (RNRs) catalyze the conversion of nucleotides to deoxynucleotides in all organisms, providing the monomeric precursors required for DNA replication and repair. The class I RNRs are composed of two subunits; the R1 subunit contains the active site for nucleotide reduction and allosteric effector binding sites, whereas the R2 subunit houses the essential diirontyrosyl (Y·) radical cofactor. A major unresolved issue is the mechanism by which the tyrosyl radical on R2 (...

Chang, Michelle C. Y.; Yee, Cyril S.; Stubbe, Joanne; Nocera, Daniel G.

2004-01-01

176

ESR study of the radicals in X-irradiated L-alpha-amino-n-butyric acid HCl containing 1.5% L-cysteine HCl  

International Nuclear Information System (INIS)

After X-irradiation at room temperature, the radicals in L-alpha-amino-n-butyric acid HCl are CH3CH2CHCOOH. The beta- and alpha-hyperfine constants are typical of those found in amino acid radicals. On annealing at temperatures near 100 degrees C this carbon-centered radical in samples containing 1.5% cysteine converts to a perthiyl radical, RCH2S(1)S(2). The g-values for the perithiyl radical are 2.0024, 2.0257, and 2.0557. When the field is in the minimum g-value direction, the hyperfine splittings are 50 G for 33S(2) and 32 G for 33S(1)

177

ESR identification of ?-irradiated redoxon and determination of ESR parameters of radicals produced in irradiated ascorbic acid  

International Nuclear Information System (INIS)

In the present work, electron spin resonance (ESR) identification of irradiated redoxon and its potential use as a normal and/or accidental dosimetric material were investigated in details. The ground redoxon samples exhibited a single weak resonance line of peak-to-peak width ?Hpp = 0.9 mT appearing at g = 2.0057. ?-Radiation produced many resonance lines beside four different intense lines (denoted as I1, I2, I3 and I4) of different spectral features in the studied dose range of 2.5-25 kGy. Experimental dose-response curves associated with I1, I2, I3 and I4 resonance lines were found to follow an exponential function. From stability and kinetic studies at room and above room temperatures it was concluded that radicals contributing to I3 and I4 resonance lines were more stable than the radical species contributing to I1 and I2 resonance lines. Simulation calculations based on the room temperature ESR intensity data of an ascorbic acid (active ingredient of redoxon) sample irradiated at 10 kGy was performed to determine the structure and spectral parameters of the radiation-induced radical species involved in the formation of experimental ESR spectrum of ascorbic acid. The contributions of these species to the ESR spectrum of irradiated redoxon were discussed

178

Absolute rate constants of alkoxyl radical reactions in aqueous solution. [Tert-butyl hydroperoxide  

Energy Technology Data Exchange (ETDEWEB)

The pulse radiolysis technique was used to generate the alkoxyl radical derived from tert-butyl hydroperoxide (/sup t/BuOOH) in aqueous solution. The reactions of this radical with 2,2'-azinobis(3-ethyl-6-benzothiazolinesulfonate) (ABTS) and promethazine were monitored by kinetic spectroscopy. The unimolecular decay rate constant of the tert-butoxyl radical (/sup t/BuO) was determined to be 1.4 x 10/sup 6/ s/sup -1/. On the basis of this value, the rate constants for /sup t/BuO attack on quercetin, crocin, crocetin, ascorbate, isoascorbate, trolox c, glutathione, thymidine, adenosine, guanosine, and unsaturated fatty acids were determined. In addition, the reaction of /sup t/BuO with the polyunsaturated fatty acids (PUFA) was observed by directly monitoring the formation of the fatty acid pentadienyl radicals. Interestingly, the attack of /sup t/BuO on PUFA was found to be faster by about one order of magnitude as compared to the same reaction in a nonpolar solvent.

Erben-Russ, M.; Michel, C.; Bors, W.; Saran, M.

1987-04-23

179

Chemical Constituents with Free-Radical-Scavenging Activities from the Stem of Microcos paniculata  

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Full Text Available The free-radical-scavenging activities of various solvent extracts of Microcos paniculata were evaluated through in vitro model systems, such as 1,1-diphenyl-2-picrylhydrazyl (DPPH, 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonate (ABTS and Co (II EDTA-induced luminol chemiluminescence by flow injection. In all three of these systems the ethyl acetate (EtOAc extract showed the highest free-radical-scavenging activity compared with the other three (n-BuOH, water and petroleum ether extracts. Free-radical-scavenging assay-guided chromatographic separation of the EtOAc extract, using a normal-phase and reverse-phase silica gel column chromatography yielded five compounds: a new triterpene named methyl 3b-O-p-hydroxy-E-cinnamoyloxy-2a,23-dihydroxyolean-12-en-28-oate (1, whose spectral data are presented for the first time, together with four known compounds, epicatechin (2, 3-trans-feruloyl maslinic acid (3, maslinic acid (4 and sucrose (5. All of the compounds were isolated from Microcos paniculata for the first time. The compounds were identified by spectroscopic methods. Among them, compound 2 displayed significant free-radical-scavenging activity which is similar to that of standard antioxidant ascorbic acid (VC and therefore may be a promising natural antioxidant.

Yu Chen

2010-08-01

180

E.S.R. of spin-trapped radicals in gamma-irradiated polycrystalline nucleic acid constituents and their halogenated derivatives  

International Nuclear Information System (INIS)

Free radicals in ?-irradiated polycrystalline nucleic acid constituents and their 5-halogenated derivatives have been studied by e.s.r. and spin-trapping. After ?-irradiation at room temperature, the polycrystalline samples were dissolved in aqueous solutions of t-nitrosobutane (tNB) in the absence or presence of oxygen. For many of the nucleic acid constituents two types of radicals, -C(5)RH-C(6)H- and -C(5)R-C(6)H2-, formed by H-addition to the double bond [-C(5)R = C(6)H-] of the base, were observed, where R is -CH3 or -H. In addition, radicals formed on the sugar moiety were found for some nucleosides. When oxygen was present in the tNB solution, the relative stability of trapped radicals was changed, and thus the presence of more than one radical species could be established. For halogenated bases, the radical produced by H-abstraction from N(1) was observed, and an additional radical species formed by H-addition to the C(6) position was found for 5-fluorouracil. For halogenated nucleosides, the same spectrum was observed in all compounds except the 5-fluoroderivatives, and was assigned to the radicals produced on the sugar moiety. For 5-fluorodeoxyuridine and 5-fluorouridine, the radical formed by H-addition to the C(6) position of the base was observed. In general, the present results are in good agreement with those of previous single crystal studies, but in the case of halogenated compounds other than the 5-fluoroderivatives, it was no than the 5-fluoroderivatives, it was not possible to spin-trap the ?-halo radicals which were the most prominent radicals formed from ?-irradiation of single crystals at room temperature. (author)

181

Formation of methane sulfinic acid in the gas-phase OH-radical initiated oxidation of dimethyl sulfoxide.  

Science.gov (United States)

Dimethyl sulfoxide (CH3S(O)CH3: DMSO) is an important product of dimethyl sulfide (CH3SCH3: DMS) photooxidation. The mechanism of the OH-radical initiated oxidation of DMSO is still highly uncertain and a major aim of recent studies has been to establish if methane sulfinic acid (CH3S(O)OH: MSIA) is a major reaction product In the present work the products of the OH-radical gas-phase oxidation of dimethyl sulfoxide have been investigated in the absence and presence of NOx All experiments were performed in a 1,080 L reaction chamber in 1,000 mbar synthetic air at 284 +/- 2 K using long-path FT-IR spectroscopy and ion chromatography to monitor and quantify reactants and reaction products. Formation of methane sulfinic acid in high yield (80-99%) was observed in both in the absence and presence of NOx, and the results support that it is the major primary reaction product Other products observed included dimethyl sulfone (CH3S(O)2CH3: DMSO2), sulfur dioxide (SO2), methane sulfonic acid (CH3S(O)2OH: MSA), and methane sulfonyl peroxynitrate (CH3S(O)2OONO2: MSPN). The formation behavior of these products is in line with their source being mainly secondary production via oxidation of a primary product, i.e. MSIA. PMID:12523433

Arsene, Cecilia; Barnes, Ian; Becker, Karl H; Schneider, William F; Wallington, Timothy T; Mihalopoulos, Nikolaos; Patroescu-Klotz, Iulia V

2002-12-01

182

Acid-catalyzed disproportionation of oxoiron(IV) porphyrins to give oxoiron(IV) porphyrin radical cations  

OpenAIRE

Disproportionation of oxoiron(IV) porphyrin (Compound II) to oxoiron(IV) porphyrin radical cation (Compound I) was studied in three P450 model systems with different electronic structures. Direct conversion of Compound II to Compound I has been observed for 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin (TDCPP) in acid-catalyzed reactions in a mixed solvent of acetonitrile and water (1:1, v/v) containing excess m-CPBA oxidant, with a second-order rate constant of (1.3 ± 0.2) × 102 M?1 s...

Pan, Zhengzheng; Newcomb, Martin

2011-01-01

183

Effect of MN (III) tetrakis (4-benzoic acid) porphyrin by photodynamically generated free radicals on SODs keratinocytes.  

Science.gov (United States)

Superoxide, a reactive form of oxygen, can be produced in vivo either in normal and under pathophysiologic conditions or by photosensitizing chemicals, as during photodynamic treatment. Photodynamic therapies (PDT), widely adopted in Dermatology and Oncology, are known to generate reactive oxygen species (ROS) and may contribute to structural alterations and oxidatively generated modifications of cellular antioxidants. We hypothesized that over-production of free radicals would decrease the enzymatic activities of endogenous cellular antioxidants. To test this hypothesis, keratinocytes were treated with the photosensitizer Photofrin plus visible light to produce free radicals and CuZnSOD and MnSOD activities were measured. Photodynamic treatment of keratinocytes increases malonylaldehyde production, nitrotyrosine staining and superoxide production. The enzymatic activities of CuZnSOD and MnSOD were significantly decreased after Photofrin plus visible light treatment. Our results suggest that the main cellular antioxidant system can be inactivated by photodynamically generated ROS. Pretreatment of keratinocytes with free radicals scavenger such as Mn (III) tetrakis (4-benzoic acid) porphyrin (MnTBAP) was able to restore the endogenous antioxidant system activities, inhibiting the MDA formation, nitrotyrosine staining and superoxide formation. Antioxidant therapy could therefore be a useful tool in protecting healthy epidermal cells against common side effects induced by antitumor targeted therapies. PMID:24152829

Nistico, S; Ventrice, D; Dagostino, C; Lauro, F; Ilari, S; Gliozzi, M; Colica, C; Musolino, V; Carresi, C; Strongoli, M C; Vecchio, I; Rizzo, M; Mollace, V; Muscoli, C

2013-01-01

184

Generation of counter ion radical (Br2(•-)) and its reactions in water-in-oil (CTAB or CPB)/n-butanol/cyclohexane/water) microemulsion.  

Science.gov (United States)

Herein we report the generation of counterion radicals and their reactions in quaternary water-in-oil microemulsion. Hydrated electrons in the microemulsion CTAB/H(2)O/n-butanol/cyclohexane have a remarkably short half-life (?1 ?s) and lower yield as compared to that in the pure water system. Electrons are solvated in two regions: one is the water core and other the interface; however, the electrons in the water core have a shorter half-life than those in the interface. The decay of the solvated electrons in the interface is found to be water content dependent and it has been interpreted in terms of increased interfacial fluidity with the increase in water content of the microemulsion. Interestingly another species, dibromide radical anion (Br(2)(•-)) in CTAB and CPB microemulsions have been observed after the electron beam irradiation. Assuming that the extinction coefficient of the radicals is the same as that in the aqueous solution, the yields of the radicals per 100 eV are 0.29 and 0.48 for the Br(2)(•-) radical in CTAB and CPB containing microemulsions (W(0) = 40), respectively, under N(2)O saturated conditions. Further, we intended to study electron transfer reactions, which occur at and through the interface. The reaction of the Br(2)(•-) radical anion with ABTS [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] has been studied to generate the ABTS radical in the water core, and further, its reaction has been investigated with the water-insoluble molecule vitamin E (tocopherol) and water-soluble vitamin C (ascorbic acid). In the present study, we were able to show that, even for molecules which are completely insoluble in water, ABTS scavenging assay is possible by pulse radiolysis technique. Furthermore, these results show that it is possible to follow the reaction of the hydrated inorganic radical with solutes dissolved in the organic phase in a microemulsion without use of a phase transfer catalyst. PMID:21815623

Guleria, Apurav; Singh, Ajay K; Sarkar, Sisir K; Mukherjee, Tulsi; Adhikari, Soumyakanti

2011-09-15

185

Atmospheric aqueous phase radical chemistry of the isoprene oxidation products methacrolein, methyl vinyl ketone, methacrylic acid and acrylic acid--kinetics and product studies.  

Science.gov (United States)

Kinetic and mechanistic studies were conducted on the isoprene oxidation products methacrolein, methyl vinyl ketone, methacrylic and acrylic acid reacting with hydroxyl and nitrate radicals and sulfate radical anions in aqueous solution by use of the laser flash photolysis technique and a reversed-rate method for kinetics. High-performance liquid chromatography/mass spectrometry was applied for product analysis. The kinetic investigations show the highest reactivity of the hydroxyl radical followed by sulfate and nitrate radicals. For methacrolein and methyl vinyl ketone the following rate constants have been determined at 298 K: k(OH+methacrolein) = (9.4 ± 0.7) × 10(9) M(-1) s(-1), k(OH+methyl?vinyl?ketone) = (7.3 ± 0.5) × 10(9) M(-1) s(-1), k(NO3+methacrolein) = (4.0 ± 1.0) × 10(7) M(-1) s(-1), k(NO3+methyl?vinyl?ketone) = (9.7 ± 3.4) × 10(6) M(-1) s(-1), k(SO4(-)+methacrolein) = (9.9 ± 4.9) × 10(7) M(-1) s(-1) and k(SO4(-)+methyl?vinyl?ketone) = (1.0 ± 0.2) × 10(8) M(-1) s(-1). Temperature and pH dependencies of the reactions of OH, NO3 and SO4(-) with methacrolein, methyl vinyl ketone, methacrylic and acrylic acid as well as Arrhenius parameters have been obtained and discussed. Product studies were performed on the OH radical induced oxidation of methacrolein and methyl vinyl ketone. In the reaction of methacrolein + OH methylglyoxal and hydroxyacetone were identified as first oxidation products with yields of 0.099 and 0.162. Methylglyoxal was primarily produced in the oxidation of methyl vinyl ketone with a yield of 0.052. For both precursor compounds the formation of glycolaldehyde was observed for the first time with yields of 0.051 and 0.111 in the oxidation of methacrolein and methyl vinyl ketone, respectively. Furthermore, highly functionalised C4 compounds were determined from the oxidation of both precursor compounds, but for the first time for methyl vinyl ketone. Reaction schemes were developed based on known peroxyl radical reaction mechanisms. The aqueous phase conversion of the first generation isoprene oxidation products can potentially contribute to tropospheric aqueous phase budgets of important carbonyl and dicarbonyl components which are expected to be conducive to the formation of aqSOA. PMID:24569503

Schöne, Luisa; Schindelka, Janine; Szeremeta, Edyta; Schaefer, Thomas; Hoffmann, Dirk; Rudzinski, Krzysztof J; Szmigielski, Rafal; Herrmann, Hartmut

2014-04-01

186

Radical Hysterectomy  

Science.gov (United States)

... for cancer on sexual function Radical hysterectomy Radical cystectomy Abdominoperineal resection Surgery for cancer of the vulva ( ... for cancer on sexual function Next Topic Radical cystectomy Radical hysterectomy Radical hysterectomy is an operation done ...

187

Mechanism of benzophenone ketyl radical formation in acid alcohols studied by pulse-radiolysis and rigid-matrix techniques. [Gamma rays  

Energy Technology Data Exchange (ETDEWEB)

The mechanism of the benzophenone ketyl radical formation in acid methanol, ethanol, and 2-propanol was studied by using pulse-radiolysis and rigid-matrix techniques. When a 0.1 M ethanol solution of benzophenone containing hydrogen chloride (1.2 M) was irradiated at 77 K by ..gamma.. rays from /sup 60/Co, the absorption spectrum of the trapped intermediates was ascribed solely to benzophenone ketyl radicals. The pulse-radiolysis study of the solution at 100 K revealed that the ketyl radicals are produced by protonation of presolvated benzophenone anion radicals. At 153 K, the ketyl radicals were observed to be produced also by hydrogen-atom transfer from CH/sub 3/CHOH and CH/sub 3/CH(OH)CH/sub 3/ to benzophenone; the temperature dependence of the transfer rate constant was studied.

Hoshino, M. (Inst. of Physical and Chemical Research, Saitama, Japan); Arai, S.; Imamura, M.; Ikehara, K.; Hama, Y.

1980-10-02

188

In-vitro free radical scavenging activity of biosynthesized gold and silver nanoparticles using Prunus armeniaca (apricot) fruit extract  

Energy Technology Data Exchange (ETDEWEB)

In-vitro free radical scavenging activity of biosynthesized gold (Au-NPs) and silver (Ag-NPs) nanoparticles was investigated in the present study. Natural precursor Prunus armeniaca (apricot) fruit extract was used as a reducing agent for the nanoparticle synthesis. The free radical scavenging activity of the nanoparticles were observed by modified 1,1 Prime -diphynyl-2-picrylhydrazyl, DPPH and 2,2 Prime -azinobis (3-ethylbenzothiazoline-6-sulfonic acid), ABTS assay. The synthesized nanoparticles were characterized by UV-Visible spectroscopy, dynamic light scattering, transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectroscopy, and fourier transform infrared spectroscopy (FTIR). Appearance of optical absorption peak at 537 nm (2.20 keV) and 435 nm (3 keV) within 0.08 and 0.5 h of reaction time was confirmed the presence of metallic Au and Ag nanoclusters, respectively. Nearly spherical nanoparticles with majority of particle below 20 nm (TEM) for both Au-NPs and Ag-NPs were synthesized. XRD pattern confirmed the existence of pure nanocrystalline Au-NPs while few additional peaks in the vicinity of fcc silver-speculated crystallization of metalloproteins of fruit extract on the surface of the Ag-NPs and vice versa. FTIR spectra was supported the role of amino acids of protein/enzymes of fruit extract for synthesis and stabilization of nanoparticles. Dose-dependent scavenging activity was observed for Au-NPs and Ag-NPs in both DPPH and ABTS in-vitro assay. 50 % scavenging activity for DPPH were 11.27 and 16.18 mg and for ABTS 3.40 and 7.12 mg with Au-NPs and Ag-NPs, respectively.

Dauthal, Preeti; Mukhopadhyay, Mausumi, E-mail: mausumi_mukhopadhyay@yahoo.com [S.V. National Institute of Technology, Department of Chemical Engineering (India)

2013-01-15

189

In-vitro free radical scavenging activity of biosynthesized gold and silver nanoparticles using Prunus armeniaca (apricot) fruit extract  

International Nuclear Information System (INIS)

In-vitro free radical scavenging activity of biosynthesized gold (Au-NPs) and silver (Ag-NPs) nanoparticles was investigated in the present study. Natural precursor Prunus armeniaca (apricot) fruit extract was used as a reducing agent for the nanoparticle synthesis. The free radical scavenging activity of the nanoparticles were observed by modified 1,1?-diphynyl-2-picrylhydrazyl, DPPH and 2,2?-azinobis (3-ethylbenzothiazoline-6-sulfonic acid), ABTS assay. The synthesized nanoparticles were characterized by UV–Visible spectroscopy, dynamic light scattering, transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectroscopy, and fourier transform infrared spectroscopy (FTIR). Appearance of optical absorption peak at 537 nm (2.20 keV) and 435 nm (3 keV) within 0.08 and 0.5 h of reaction time was confirmed the presence of metallic Au and Ag nanoclusters, respectively. Nearly spherical nanoparticles with majority of particle below 20 nm (TEM) for both Au-NPs and Ag-NPs were synthesized. XRD pattern confirmed the existence of pure nanocrystalline Au-NPs while few additional peaks in the vicinity of fcc silver-speculated crystallization of metalloproteins of fruit extract on the surface of the Ag-NPs and vice versa. FTIR spectra was supported the role of amino acids of protein/enzymes of fruit extract for synthesis and stabilization of nanoparticles. Dose-dependent scavenging activity was observed for Au-NPs and Ag-NPs in both DPPH and ABTSNPs and Ag-NPs in both DPPH and ABTS in-vitro assay. 50 % scavenging activity for DPPH were 11.27 and 16.18 mg and for ABTS 3.40 and 7.12 mg with Au-NPs and Ag-NPs, respectively.

190

Spectroscopic studies on the antioxidant activity of ellagic acid  

Science.gov (United States)

Ellagic acid (EA, C14H6O8) is a natural dietary polyphenol whose benefits in a variety of diseases shown in epidemiological and experimental studies involve anti-inflammation, anti-proliferation, anti-angiogenesis, anticarcinogenesis and anti-oxidation properties. In vitro radical scavenging and antioxidant capacity of EA were clarified using different analytical methodologies such as total antioxidant activity determination by ferric thiocyanate, hydrogen peroxide scavenging, 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH) scavenging, 2,2?-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity and superoxide anion radical scavenging, ferrous ions (Fe2+) chelating activity and ferric ions (Fe3+) reducing ability. EA inhibited 71.2% lipid peroxidation of a linoleic acid emulsion at 45 ?g/mL concentration. On the other hand, butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), ?-tocopherol and ascorbic acid displayed 69.8%, 66.8%, 64.5% and 59.7% inhibition on the peroxidation of linoleic acid emulsion at the same concentration, respectively. In addition, EA had an effective DPPH• scavenging, ABTSrad + scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (Fe3+) reducing power and ferrous ions (Fe2+) chelating activities. Also, those various antioxidant activities were compared to BHA, BHT, ?-tocopherol and ascorbic acid as references antioxidant compounds. These results suggested that EA can be used in the pharmacological, food industry and medicine because of these properties.

Kilic, Ismail; Ye?ilo?lu, Ye?im; Bayrak, Yüksel

2014-09-01

191

A mechanism for NaCl inhibition of Reactive Blue 19 decolorization and ABTS oxidation by laccase.  

Science.gov (United States)

Laccases produced by white rot fungi have been extensively evaluated for their potential to decolorize textile wastewaters which contain salts like sodium chloride and sodium sulfate. The effect of sodium chloride and sodium sulfate on Trametes versicolor laccase during the decolorization of an anthraquinone dye (Reactive Blue 19) and the oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) were evaluated by steady-state kinetic analysis. The results showed that, while sodium sulfate did not affect laccase activity, sodium chloride inhibited both ABTS oxidation and dye decolorization. However, the type of inhibition was substrate-dependent: it was hyperbolic, noncompetitive with ABTS and parabolic, noncompetitive with Reactive Blue 19. Furthermore, the results suggested that two chlorides may bind to laccase in the presence of the dye unlike recent inhibition models which suggest that there is only one inhibition site. This investigation is the first to provide evidence for and to propose a two-site model of laccase inhibition, providing new insight into NaCl inhibition of laccase. The proposed model is also useful to predict decolorization rates in the presence of sodium chloride and to determine operating conditions that will minimize inhibition. PMID:23129183

Champagne, P-P; Nesheim, M E; Ramsay, J A

2013-07-01

192

Reactivity of OH radicals with chlorobenzoic acids-A pulse radiolysis and steady-state radiolysis study  

Energy Technology Data Exchange (ETDEWEB)

The reactions of OH radicals with 2-, 3-, 4-chlorobenzoic acids (ClBzA) and chlorobenzene (ClBz), k({sup c}entre dotOH+substrates)=(4.5-6.2)x10{sup 9} dm{sup 3} mol{sup -1} s{sup -1}, have been studied by pulse radiolysis in N{sub 2}O saturated solutions. The absorption maxima of the OH-adducts were in the range of 320-340 nm. Their decay was according to a second-order reaction, 2k=(1-9)x10{sup 8} dm{sup 3} mol{sup -1} s{sup -1}. In the presence of N{sub 2}O/O{sub 2} the formation of peroxyl radicals was detectable for 2-, 4-ClBzA and ClBz, k(OH-adduct+O{sub 2})=(2-4)x10{sup 7} dm{sup 3} mol{sup -1} s{sup -1}, while this reaction for 3-ClBzA was too slow to be registered. In the presence of N{sub 2}O the degradation rates induced by gamma radiation were very similar for all chlorobenzoic acids, yet the chloride formation was distinctly higher for 3-ClBzA. In the presence of oxygen the initial degradation of 2-and 4-ClBzA equaled the OH-radical concentration, whereas in case of 3-ClBzA only approx60% of {sup c}entre dotOH led to degradation. The order for the efficiency of dehalogenation was 4->2->3-ClBzA. Several primary radiolytic products could be detected by HPLC. To evaluate the toxicity of final products a bacterial bioluminescence test was carried out.

Zona, Robert [University of Vienna, Department of Nutritional Sciences, Section Radiation Biology, UZAII, Althanstrasse 14, A-1090 Vienna (Austria); Solar, Sonja, E-mail: sonja.solar@univie.ac.a [University of Vienna, Department of Nutritional Sciences, Section Radiation Biology, UZAII, Althanstrasse 14, A-1090 Vienna (Austria); Getoff, Nikola [University of Vienna, Department of Nutritional Sciences, Section Radiation Biology, UZAII, Althanstrasse 14, A-1090 Vienna (Austria); Sehested, Knud; Holcman, Jerzy [RISO National Laboratory Environmental Science and Technology Department, DK-4000, Roskilde (Denmark)

2010-05-15

193

ESR identification of {gamma}-irradiated redoxon and determination of ESR parameters of radicals produced in irradiated ascorbic acid  

Energy Technology Data Exchange (ETDEWEB)

In the present work, electron spin resonance (ESR) identification of irradiated redoxon and its potential use as a normal and/or accidental dosimetric material were investigated in details. The ground redoxon samples exhibited a single weak resonance line of peak-to-peak width {delta}H{sub pp} = 0.9 mT appearing at g = 2.0057. {gamma}-Radiation produced many resonance lines beside four different intense lines (denoted as I{sub 1}, I{sub 2}, I{sub 3} and I{sub 4}) of different spectral features in the studied dose range of 2.5-25 kGy. Experimental dose-response curves associated with I{sub 1}, I{sub 2}, I{sub 3} and I{sub 4} resonance lines were found to follow an exponential function. From stability and kinetic studies at room and above room temperatures it was concluded that radicals contributing to I{sub 3} and I{sub 4} resonance lines were more stable than the radical species contributing to I{sub 1} and I{sub 2} resonance lines. Simulation calculations based on the room temperature ESR intensity data of an ascorbic acid (active ingredient of redoxon) sample irradiated at 10 kGy was performed to determine the structure and spectral parameters of the radiation-induced radical species involved in the formation of experimental ESR spectrum of ascorbic acid. The contributions of these species to the ESR spectrum of irradiated redoxon were discussed.

Polat, Mustafa [Physics Engineering Department, Hacettepe University, Beytepe, 06800 Ankara (Turkey)]. E-mail: polat@hacettepe.edu.tr; Korkmaz, Mustafa [Physics Engineering Department, Hacettepe University, Beytepe, 06800 Ankara (Turkey)

2005-04-11

194

Tropospheric chemistry of natural hydrocarbons, aldehydes, and peroxy radicals: Their connections to sulfuric acid production and climate effects  

International Nuclear Information System (INIS)

Recent work has shown that natural hydrocarbon emissions can significantly affect the levels of urban and regional tropospheric ozone. We report on the reactivities of these biogenic trace gases, particularly isoprene, focusing on their importance in the production of aldehydes and peroxy radicals, leading to increased levels of hydrogen over regional forests. Hydrogen peroxide can lead to the wet oxidation of sulfur dioxide to acidic sulfate in aerosols, fogs, and clouds. In turn, acidic sulfate can act to as a light scattering aerosol and a source of cloud condensation nuclei (CCN), potentially leading to global cooling. Aerosol sulfate and other dissolved organic and inorganic compounds can also play important roles as a greenhouse species in the lower troposphere

195

Acid-catalyzed disproportionation of oxoiron(IV) porphyrins to give oxoiron(IV) porphyrin radical cations.  

Science.gov (United States)

Disproportionation of oxoiron(IV) porphyrin (Compound II) to oxoiron(IV) porphyrin radical cation (Compound I) was studied in three P450 model systems with different electronic structures. Direct conversion of Compound II to Compound I has been observed for 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrin (TDCPP) in acid-catalyzed reactions in a mixed solvent of acetonitrile and water (1:1, v/v) containing excess m-CPBA oxidant, with a second-order rate constant of (1.3 ± 0.2) × 10(2) M(-1) s(-1). The acid-catalyzed disproportionation heavily depends on the electron demand of the substituted aryl groups on the porphyrin macrocycle. The disproportionation equilibrium constants show drastic change for the three porphyrin systems. PMID:21572532

Pan, Zhengzheng; Newcomb, Martin

2011-06-01

196

Synthesis of Hydrogel Based on Nata De Coco and Acrylic Acid as Co-Monomer Using Free Radical Polymerization Method  

International Nuclear Information System (INIS)

Nata de Coco or known as bacterial cellulose is produced by Acetobacter xylinum where it is more stable than plant cellulose. Moreover, it also provides outstanding advantages to be developed as an environmental responsive hydrogels. In this study the bacterial cellulose-g-acrylic acid hydrogel was synthesized by using a free radical polymerization method. Ammonium persulfate (APS) was used to initiate the reaction, while N,N'-methylene bis acrylamide has been used as the crosslinking agent. In order to test the hydrogel respond, swelling tests were made at different pH. Furthermore, ATR-FTIR analysis was used to determine the interactions between bacterial cellulose and acrylic acid. Finally, the determination of glass transition (Tg) was made by using DSC. (author)

197

Synthesis and Biological Evaluation of New 1,3-Thiazolidine-4-one Derivatives of 2-(4-Isobutylphenyl)propionic Acid  

OpenAIRE

New thiazolidine-4-one derivatives of 2-(4-isobutylphenyl)propionic acid (ibuprofen) have been synthesized as potential anti-inflammatory drugs. The structure of the new compounds was proved using spectral methods (FR-IR, 1H-NMR, 13C-NMR, MS). The in vitro antioxidant potential of the synthesized compounds was evaluated according to the total antioxidant activity, the DPPH and ABTS radical scavenging assays. Reactive oxygen species (ROS) and free radicals are considered to be involved in many...

Ioana Mirela Vasincu; Maria Apotrosoaei; Andreea-Teodora Panzariu; Frédéric Buron; Sylvain Routier; Lenuta Profire

2014-01-01

198

Reaction pathway of the degradation of the p-hydroxybenzoic acid by sulfate radical generated by ionizing radiations  

Science.gov (United States)

The degradation of p-hydroxybenzoic acid (HBA) in aqueous solutions by ionizing radiation was studied. The phenolic pollutant was easily removed by the electron beam irradiation, as more than 80% of the initial 100 ?M introduced was degraded for a dose of 600 Gy. It was shown that the addition of persulfate, producing the sulfate radical as additional reactive species, induced a change in the reaction pathway. LC-MS analyses were performed in order to identify the different by-products formed. In the absence of persulfate, the main by-product formed was 3,4-dihydroxybenzoic acid, while in presence of persulfate, 1,4-benzoquinone was detected and the hydroxylated by-products were not present. A reaction pathway of HBA degradation by hydroxyl and sulfate radicals was proposed from the identification of the chemical structure of the different by-products detected. The influences of pH and dissolved oxygen were also studied. A high decline of HBA degradation was observed at pH 11 compared to pH 4.5, this decrease was minimized in the presence of persulfate. The dissolved oxygen concentration was found to be a limiting parameter of HBA degradation, however an excess of dissolved oxygen in solution did not improve the degradation to a large extent.

Criquet, Justine; Leitner, Nathalie Karpel Vel

2015-01-01

199

Kinetics of electron-transfer reactions of hydroquinones and ascorbic acid with 1-phenyl-3-pyrazolidone radicals  

Energy Technology Data Exchange (ETDEWEB)

The kinetics of oxidation of four hydroquinones and ascorbic acid by 1-phenyl-3-pyrazolidone radicals have been examined in aqueous solution from pH 6.5 to 9.5. For the hydroquinones, the kinetics are markedly autocatalytic unless sulfite is present in the solutions. The autocatalysis is apparently due to accumulation of a significant quantity of semiquinone formed via reproportionation of the quinone product with unreacted hydroquinone. If present in sufficient concentration, sulfite eliminates autocatalysis by scavenging quinone, and the kinetics are first-order in each reactant. The kinetic results suggest that the electron transfer from hydroquinone to the radical to form semiquinone is rate-limiting. In the case of ascorbic acid, autocatalysis is not observed, and the kinetics are first-order in oxidant and reductant. The kinetic dependence on pH permits the resolution of bimolecular rate constants for oxidation of the fully ionized and the singly protonated reductants. The correlation of these rate constants with thermodynamic driving force is in agreement with the Marcus theory.

Youngblood, M.P.

1989-03-01

200

Oxidation of Amino Acids by Chlorpromazine Cation Radical and Co-Catalysis by Chlorpromazine  

OpenAIRE

The long-tem use of chlorpromazine (CPZ) may cause severe side effects. This property of CPZ might be related to pro-oxidant effects of the chlorpromazine cation radical (CPZ·+), which can be easily generated by catalytic action of peroxidases, including the neutrophil myeloperoxidase (MPO) and by methemoglobin. Aiming the comprehension of a putative physiological effect of CPZ·+ upon biomolecules, in this work we studied the reactivity of CPZ&l...

Menezes, Manoel L.; Graciani, Fernanda S.; Quaggio, Giovana B.; Ximenes, Valdecir F.

2012-01-01

201

The ABT methodology employment for VET of quality auditors  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents some achievements of the project entitled “Disseminating Open and Innovative Tools and Services for Vocational Education and Training in Quality Assurance” (acronym Do-IT financed by European Commission. The recent developments and results obtained during pilot testing of new pedagogical models and services, in Do-IT project, targeting engineering education in Romania are presented. This include the activity Based Training methodology (ABT for quality management system audit course according to ISO 19011 and ISO 9001 and evaluation of theoretical achievements with Student Response System (SRS.

Liviu Moldovan

2011-12-01

202

[Formation of hydrogen peroxide and hydroxyl radicals in aqueous solutions of L-amino acids by the action of X-rays and heat].  

Science.gov (United States)

The action of 1 mM solutions of L-amino acids in 5 mM phosphate buffer, pH 7.4, on the production of hydrogen peroxide and hydroxyl radicals under the action of X-rays and heating has been studied. Hydrogen peroxide was estimated by the method of enhanced luminescence in a system luminol-paraiodophenol-peroxidase and hydroxyl radicals were determined by using the fluorescence probe coumarin-3-carboxylic acid. It was shown that amino acids can be divided by their influence on H202 formation into three groups: those that reduce the yield of H202, that do not influence it, and that increase it. A similar action of amino acids was observed upon heating, but the composition of the groups was different. All amino acids lowered the formation of hydroxyl radicals under the action of X-rays, and the most effective among them were Cys > His > Phe = Met = Trp > Tyr. Met, His and Phe lowered the amount of hydroxyl radicals by heating, Ser raised it, whereas Tyr and Pro did not change it. Thus, amino acids differently influence the formation of reactive oxygen species by the action of X-rays and heat, and some of amino acids reveal themselves as effective natural antioxidants. PMID:18488494

Shtarkman, I N; Gudkov, S V; Chernikov, A V; Bruskov, V I

2008-01-01

203

Abts cation scavenging activity and total phenolic content of three moss species  

Directory of Open Access Journals (Sweden)

Full Text Available A limited number of mosses have ever been studied in regard to antioxidant activity; with only few belonging to the European species. As part of our on-going screening of bryophytes as natural antioxidant resources, a relevant biological activity investigation was conducted on the three moss species, namely Brachythecium rutabulum (Hedw. Schimp. (Brachytheciaceae, Calliergonella cuspidata (Hedw. Loeske (Hypnaceae and Hypnum mammillatum (Brid. Loeske (Hypnaceae, collected in Germany. The antioxidant activity of corresponding lyophilised aqueous extracts (teas was evaluated on the basis of their ABTS [2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid] cation scavenging activities. The total phenolic contents were determined as well. This study led to the detection of a moderate total phenolic content of the moss B. rutabulum, indicating for the first time its potential in searching for novel antioxidant agents.

Bogdanovi?-Pristov Jelena

2012-01-01

204

Antioxidant activity and free radical scavenging capacity of phenolic extracts from Helicteres isora L. and Ceiba pentandra L.  

Science.gov (United States)

In the present study, antioxidant activities of the phenolic extracts from H. isora fruits and C. pentandra seeds were investigated by employing established in vitro systems, which included reducing power, OH(?), DPPH(?), ABTS(?+), linoleic acid emulsion, metal chelation and antihemolytic activity. The extracts of C. pentandra contained relatively higher levels of total phenolics and flavonoids than those of H. isora. All the extracts showed dose dependent reducing power activity and moreover, they were well correlated with the total phenolic substances. A similar dose dependant trend has also been observed for hydroxyl radical scavenging activity and DPPH(?) radical scavenging activity. Further, addition of 250 ?g of extracts to the reaction mixture produced 41.3-54.6% peroxidation inhibiting activity during 60 h of incubation. The potential of multiple antioxidant activity of samples can be further evidenced by inhibition of reactive oxygen mediated erythrocyte cell lysis and metal ion chelating activity. PMID:24425970

Loganayaki, Nataraj; Siddhuraju, Perumal; Manian, Sellamuthu

2013-08-01

205

Biological Activities of Hominis Placenta Herbal Acupuncture prepared by Hydrochloric Acid Hydrolysis  

Directory of Open Access Journals (Sweden)

Full Text Available Reactive Oxygen Species(ROS are continuously produced at a high rate as a by-product of aerobic metabolism. Since tissue damage by free radical increases with age, the reactive oxygen species(ROS such as hydrogen peroxide(H2O2, nitric oxide(NO. Several lines of evidence provided that ROS appears to cause to develop aging-related various diseases such as cancer, arthritis, cardiovascular disease. In this study, we have conducted to investigate the biological activities of Hominis Placenta Herbal Acupuncture by measuring total polyphenol content, DPPH radical scavenging, ABTS radical scavenging, Superoxide dismutase(SOD-like activity, Nitrite scavenging ability in vitro. The total polyphenol contents of Hominis Placenta Herbal Acupuncture was 24.6?/?. Elctron donation ability on DPPH was 49.4%. The 2,2'-azinobis-3-ehtlbezothiazoline-6-sulfonic acid radical decolorization (ABTS was 50.01%, similar to the DPPH free radical scavenging. The superoxide dismutase (SOD-like activities of hominis placenta herbal acupuncture was 50.876%. The nitrite scavenging abilities at pH 1.5, pH 3.0, pH 6.0 were 52.8%, 29.4%, 15.4%, respectively; these abilities decreased as pH increased. We conclude that Hominis Placenta Herbal Acupuncture may be useful as potential sources of antioxidant.

Geun-young Seo

2010-06-01

206

Peroxyacetic acid in urban and rural atmosphere: concentration, feedback on PAN-NOx cycle and implication on radical chemistry  

Directory of Open Access Journals (Sweden)

Full Text Available Peroxyacetic acid (PAA is one of the most important atmospheric organic peroxides, which have received increasing attention for their potential contribution to the oxidation capacity of the troposphere and the formation of secondary aerosols. We report here, for the first time, a series of data for atmospheric PAA concentrations at urban and rural sites, from five field campaigns carried out in China in summer 2006, 2007 and 2008. For these five measurements, daytime mean (08:00–20:00 LT PAA concentrations on sunlit days were 21.4–148.0 pptv with a maximum level of ~1 ppbv. The various meteorological and chemical parameters influencing PAA concentrations were examined using Principal Factor Analysis. This statistical analysis shows that the local photochemical production was the major source of PAA, and its concentration increased with increasing temperature, solar radiation and ozone but decreased with increasing NOx (NO and NO2, CO, SO2, and relative humidity. Based on the dataset, several issues are highlighted in this study: (i Because PAA is a product from the photochemical oxidation of some specific volatile organic compounds (VOCs that lead to acetyl peroxy radicals, the importance of various VOCs with respect to the PAA formation is therefore ranked using the incremental reactivity method. (ii The contribution of PAN thermal degradation to PAA formation under conditions of different NOx concentrations is estimated based on the chemical kinetics analysis. The result shows that PAN seems to play an important role in the formation of PAA when the NO/NO2 concentration ratio was less than 0.2 and PAA would correspondingly have feedback on the PAN-NOx cycle. (iii PAA and other peroxides, such as methyl hydroperoxide (MHP and H2O2, usually exhibited a similar asymmetric shape typically shifted to the afternoon. However, under some conditions, H2O2 diurnal cycle was out of phase with MHP and PAA. The combination of linear regression and kinetics analysis indicate that the formation and removal processes of H2O2 may be different from those of MHP and PAA. (iv Considering that PAA is the reservior of free radicals, its fate is expected to have an effect on the free radical budget in the atmosphere. A box model based on the CBM-IV mechanism has been performed to access its influence on the radical budget. We suggest that the detailed information on PAA in the atmosphere is of importance to better understand the free radical chemistry.

J. L. Li

2010-01-01

207

Peroxyacetic acid in urban and rural atmosphere: concentration, feedback on PAN-NOx cycle and implication on radical chemistry  

Directory of Open Access Journals (Sweden)

Full Text Available Peroxyacetic Acid (PAA is one of important atmospheric organic peroxides, which have received increasing attention for their potential contribution to the oxidation capacity of the troposphere and the formation of secondary aerosols. We report here that, for the first time, a series of data for atmospheric PAA concentrations at urban and rural sites, from five field campaigns carried out in China in summer 2006, 2007 and 2008. For these five measurements, daytime mean PAA concentrations on sunlit days were 0.02–0.14 ppbv with a maximum level of ~1 ppbv. The various meteorological and chemical parameters influencing PAA concentrations were examined using the Principal Factor Analysis. This statistical analysis shows that the local photochemical production was the major source of PAA, and its concentration increased with increasing temperature, solar radiation and ozone but decreased with increasing NOx (NO and NO2, CO, SO2, and relative humidity. Based on the dataset, several issues are highlighted in this study: (i because PAA is a product from the photochemical oxidation of some specific volatile organic compounds (VOCs that lead to acetyl peroxy radicals, the importance of various VOCs with respect to the PAA formation is therefore ranked using the incremental reactivity method. (ii The contribution of PAN thermal degradation to PAA formation under conditions of different NOx concentrations is estimated based on the chemical kinetics analysis. The result shows that PAN seems to play an important role in the formation of PAA when the NO/NO2 concentration ratio was less than 0.2 and PAA would correspondingly have feedback on the PAN-NOx cycle. (iii PAA and other peroxides, such as methyl hydroperoxide (MHP and H2O2, usually exhibited a similar asymmetric shape typically shifted to the afternoon. However, at a high SO2 level, H2O2 showed a profile different from those of MHP and PAA. The combination of linear regression and chemical kinetics analysis reveals that a possible unknown pathway results in the significant removal of H2O2 and the extent of H2O2 undergoing this pathway needs a further study. (iv Considering that PAA is the reservior of free radicals, its fate is expected to have an effect on the free radical budget in the atmosphere. A box model based on the CBM-IV mechanism has been performed to access its influence on the radical budget. We suggest that the detailed information on PAA in the atmosphere is of importance to better understand the free radical chemistry.

J. L. Li

2009-10-01

208

Sofosbuvir and ABT-450: Terminator of hepatitis C virus?  

Directory of Open Access Journals (Sweden)

Full Text Available Combination therapy with peginterferon (pegIFN-? and ribavirin (RBV has been the standard of care (SOC for chronic hepatitis C. Unfortunately, not all patients can achieve a sustained virologic response (SVR with this regimen. SVR rates are approximately 80% in patients with hepatitis C virus (HCV genotype 2, 3, 5 and 6 and 40%-50% in patients with genotype 1 and 4. Therefore, strategies to improve SVR rates have been an important issue for clinical physicians. Several direct acting antiviral agents (DAAs have significantly higher SVR rates when combined with pegIFN-? and RBV than pegIFN-? and RBV alone. Treatments containing DAAs have several advantages over the previous SOC, including higher specificity and efficacy, shorter treatment durations, fewer side effects, and oral administration. Based on these advantages, treatment with pegIFN-? and RBV plus telaprevir or boceprevir has become the current SOC for patients with genotype 1 HCV infection. However, many patients are either not eligible for therapy or decline treatment due to coexisting relative or absolute contraindications as well as an inability to tolerate the hematological side effects and adverse events caused by the new SOC. These factors have contributed to the advent of pegIFN-?-free regimens. The newest therapeutic regimens containing sofosbuvir and ABT-450 have shown promising results. In this review, we summarize the development of anti-HCV agents and the clinical efficacy of sofosbuvir and ABT-450-based therapies as well as the potential for future HCV studies.

Qing-Lei Zeng

2013-01-01

209

Evaluation of free-radical quenching properties of standard Ayurvedic formulation Vayasthapana Rasayana  

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Full Text Available Abstract Background Cellular damage induced by free-radicals like Reactive Oxygen and Nitrogen Species (ROS and RNS has been implicated in several disorders and diseases, including ageing. Hence naturally occurring anti-oxidant rich-herbs play a vital role in combating these conditions. The present study was carried out to investigate the in vitro free-radical quenching capacity of a known Ayurvedic poly-herbal formulation called Vayasthapana Rasayana. Methods Methanol extracts of Vayasthapana Rasayana formulation (VRF were studied for in vitro total antioxidant activity along with phenolic content and reducing power. In vitro assays like DPPH, FRAP, ABTS scavenging to evaluate radical quenching potential were performed. Results The formulation has shown 94% at 0.1 mg/ml DPPH free-radical scavenging activity as against 84% at 0.1 mg/ml for standard ascorbic acid (IC50 value 5.51 ?g/ml for VRF and 39 ?g/ml for standard. It has a significant higher ferric reducing potential also (OD 0.87 at 700 nm & 0.21 at 0.1 mg/ml for VRF and standard, respectively. The total phenolic content (gallic acid equivalent of the VRF is 8.3 mg per g of dry mass. Total antioxidant capacity of the formulation, estimated by FRAP was 1150 ± 5 ?M Fe(II/g dry mass. ABTS radical scavenging activity of VRF was 69.55 ± 0.21% at 100 ?g/ml concentration with a IC50 value of 69.87 ?g/ml as against 9% and 95% by ascorbic acid and Trolox (at 70.452 ?g/ml and 0.250 ?g/ml concentrations, respectively. Conclusion In Indian traditional Ayurvedic system, use of VRF is in regular practice for mainly combating age-related disorders and diseases as many of the components of the Rasayana are known for their free-radical scavenging activity. This study has validated the potential use of VRF as an anti-oxidant to fight age-related problems.

Bhujbal Akshay

2011-05-01

210

Carcinogen-induced, free radical-mediated reduction in microsomal membrane fluidity: reversal by indole-3-propionic acid.  

Science.gov (United States)

Chromium (Cr) is a well established carcinogen, with Cr(III) accounting for much of the intracellular oxidative damage that this transition metal induces. Indole-3-propionic acid (IPA), a melatonin-related molecule, is a reported antioxidant and free radical scavenger. Concentration (1, 10, 100, 500, or 1000 microM) and time (15, 30, 45, 60, or 90 min)-dependent effects of Cr(III) in the presence of H2O2 (0.5 mM), as well as the protective effect of IPA on Cr(III)-induced alterations in membrane fluidity (the inverse of membrane rigidity), as an index of membrane damage, were estimated by fluorescence spectroscopy. Cr(III), in a concentration- and a time-dependent manner, decreased membrane fluidity, with marked effects at a concentration of 500 microM and 60 min of incubation. IPA (5, 3, or 1 mM) prevented the Cr(III)-induced decrease in membrane fluidity. It is concluded that the carcinogen Cr(III), in the presence of H202, generates free radicals, which decrease membrane fluidity in rat microsomal membranes. Membrane alterations are pharmacologically prevented by the antioxidant IPA. PMID:11460928

Karbownik, M; Garcia, J J; Lewi?ski, A; Reiter, R J

2001-02-01

211

Free radical scavenging profile and myeloperoxidase inhibition of extracts from antidiabetic plants: Bauhinia forficata and Cissus sicyoides.  

Science.gov (United States)

There is abundant evidence that reactive oxygen species are implicated in several physiological and pathological processes. To protect biological targets from oxidative damage, antioxidants must react with radicals and other reactive species faster than biological substrates do. The aim of the present study was to determine the in vitro antioxidant activity of aqueous extracts from leaves of Bauhinia forficata Link (Fabaceae-Caesalpinioideae) and Cissus sicyoides L. (Vitaceae) (two medicinal plants used popularly in the control of diabetes mellitus), using several different assay systems, namely, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) decolorization, superoxide anion radical (O2(.-)) scavenging and myeloperoxidase (MPO) activity. In the ABTS assay for total antioxidant activity, B. forficata showed IC50 = 8.00+/-0.07 microg/mL, while C. sicyoides showed IC50 = 13.0+/-0.2 microg/mL. However, the extract of C. sicyoides had a stronger effect on O2(.-) (IC50 = 60.0+/-2.3 microg/mL) than the extract of B. forficata (IC50 = 90.0+/-4.4 microg/mL). B. forficata also had a stronger inhibitory effect on MPO activity, as measured by guaiacol oxidation, than C. sicyoides. These results indicate that aqueous extracts of leaves of B. forficata and C. sicyoides are a potential source of natural antioxidants and may be helpful in the prevention of diabetic complications associated with oxidative stress. PMID:18949134

Khalil, Najeh M; Pepato, Maria T; Brunetti, Iguatemy L

2008-01-01

212

Phospholipid furan fatty acids and ubiquinone-8: lipid biomarkers that may protect dehalococcoides strains from free radicals.  

Science.gov (United States)

Dehalococcoides species have a highly restricted lifestyle and are only known to derive energy from reductive dehalogenation reactions. The lipid fraction of two Dehalococcoides isolates, strains BAV1 and FL2, and a tetrachloroethene-to-ethene-dechlorinating Dehalococcoides-containing consortium were analyzed for neutral lipids and phospholipid fatty acids. Unusual phospholipid modifications, including the replacement of unsaturated fatty acids with furan fatty acids, were detected in both Dehalococcoides isolates and the mixed culture. The following three furan fatty acids are reported as present in bacterial phospholipids for the first time: 9-(5-pentyl-2-furyl)-nonanoate (Fu18:2omega6), 9-(5-butyl-2-furyl)-nonanoate (Fu17:2omega5), and 8-(5-pentyl-2-furyl)-octanoate (Fu17:2omega6). The neutral lipids of the Dehalococcoides cultures contained unusually large amounts of benzoquinones (i.e., ubiquinones [UQ]), which is unusual for anaerobes. In particular, the UQ-8 content of Dehalococcoides was 5- to 20-fold greater than that generated in aerobically grown Escherichia coli cultures relative to the phospholipid fatty acid content. Naphthoquinone isoprenologues (MK), which are often found in anaerobically grown bacteria and archaea, were also detected. Dehalococcoides shows a difference in isoprenologue pattern between UQ-8 and MK-5 that is atypical of other bacteria capable of producing both quinone types. The difference in UQ-8 and MK-5 isoprenologue patterns strongly suggests a special function for UQ in Dehalococcoides, and Dehalococcoides may utilize structural modifications in its lipid armamentarium to protect against free radicals that are generated in the process of reductive dechlorination. PMID:16332831

White, David C; Geyer, Roland; Peacock, Aaron D; Hedrick, David B; Koenigsberg, Stephen S; Sung, Youlboong; He, Jianzhong; Löffler, Frank E

2005-12-01

213

Matrix isolation of free radicals from 5-halouracils. 3. Electron spin resonance of base oxidation in aqueous acidic glasses  

International Nuclear Information System (INIS)

Electron spin resonance spectroscopy (ESR) of X-irradiated aqueous acidic glasses (5.3 M H2SO4, 7.2 to 14.7 M H3PO4) was used to study the base ? cations of the nucleic acid constituents uracil (U), thymine (T), and the range of 5-halogen-substituted uracils (FU, ClU, BU, IU) as well as their nucleoside derivatives and to follow their secondary reactions. High solute concentrations (> 50 mM) and the presence of electron scavengers (100 to 200 mM Na2S2O8 or H2O2) were found to favor the cation formation and stabilization and to suppress the formation and stabilization and to suppress the formation of other solute radicals. The generation of the base cations is shown to result from transfer of a (possibly) excited solvent hole to the pyrimidine base during X irradiation at 770K and from attack of the trapped solvent hole (SO4-. or HPO4-.) after thermal activation at elevated temperatures (145 to 1650K). The fate of the base cations is either deprotonation at N1 as in most of the free bases or addition of OH- to carbon C6 in the nucleosides where the deoxyribose moiety prevents the deprotonation. This hydroxylation is suppressed in a water-deficient system (e.g., 14.7 M H3PO4) but very efficient in 5.3 M H2SO4. The structures of both the primary and secoe structures of both the primary and secondary radicals are confirmed in most cases by a complete simulation of the experimental ESR powder spectra. The ESR parameters obtained display a strong influence of the 5 substituent, e.g., the halogens, on the spin density distribution in the radicals. Characteristic for ? orbital ranging from 8% in FU to 40% in IU. Moreover, the amount of water in the environment exerts a considerable influence on the halogen spin densities in the charged cation

214

Measurements of the Temperature Dependence of the Rate Constant of the Reaction of Hydroxyl Radical and Acetic Acid and its Deuterated Isotopomers Between Temperatures 263-373K  

Science.gov (United States)

Acetic acid is ubiquitous in the earth's atmosphere where it has a global source strength of ~ 75 Tg yr-1 from secondary photochemical reactions and ~ 48 Tg yr-1 from direct emissions due to biomass burning. It contributes significantly to the acidity of natural waters and plays an important role in determining OH and HO2 radical budgets and ultimately affecting the oxidative capacity of troposphere. Acetic acid is removed from the atmosphere primarily by wet and dry deposition and by reaction with hydroxyl (OH) radical. However, current atmospheric chemistry models are not able to accurately reproduce acetic acid concentrations suggesting a gap in our understanding of its sources and sinks. We present low pressure (~ 5 Torr) measurements of the rate constant of the reaction of acetic acid with OH in the temperature range of 263-373K, using the discharge flow techniques coupled with resonance fluorescence detection of OH radicals. Our measured value of the rate constant of (7.37 ± 0.34) × 10-13cm3molecule-1s-1 at 298K is in good agreement with previous studies. At low pressure, the reaction displays a negative temperature dependence consistent with previous studies conducted at higher pressures. A primary kinetic isotope effect was observed while comparing the rate constants for reaction of OH with CD3COOH (acetic acid-d3) and CD3COOD (acetic acid-d4) confirming that the dominant reaction mechanism is H-abstraction from the carboxylic group.

Vimal, D.; Stevens, P. S.

2005-12-01

215

Effect of amino acids on X-ray-induced hydrogen peroxide and hydroxyl radical formation in water and 8-oxoguanine in DNA.  

Science.gov (United States)

Generation of hydrogen peroxide and hydroxyl radicals in L-amino acid solutions in phosphate buffer, pH 7.4, under X-ray irradiation was determined by enhanced chemiluminescence in the luminol-p-iodophenol-peroxidase system and using the fluorescent probe coumarin-3-carboxylic acid, respectively. Amino acids are divided into three groups according to their effect on the hydrogen peroxide formation under irradiation: those decreasing yield of H2O2, having no effect, and increasing its yield. All studied amino acids at 1 mM concentration decrease the yield of hydroxyl radicals in solution under X-ray irradiation. However, the highest effect is observed in the order: Cys > His > Phe = Met = Trp > Tyr. At Cys, Tyr, and His concentrations close to physiological, the yield of hydroxyl radicals decreases significantly. Immunoenzyme analysis using monoclonal antibodies to 8-oxoguanine (8-oxo-7,8-dihydroguanine) was applied to study the effect of amino acids with the most pronounced antioxidant properties (Cys, Met, Tyr, Trp, Phe, His, Lys, Arg, Pro) on 8-oxoguanine formation in vitro under X-ray irradiation. It is shown that amino acids decrease the content of 8-oxoguanine in DNA. These amino acids within DNA-binding proteins may protect intracellular DNA against oxidative damage caused by formation of reactive oxygen species in conditions of moderate oxidative stress. PMID:18457578

Shtarkman, I N; Gudkov, S V; Chernikov, A V; Bruskov, V I

2008-04-01

216

40 CFR 1054.730 - What ABT reports must I send to EPA?  

Science.gov (United States)

...2010-07-01 false What ABT reports must I send to EPA? 1054.730 Section 1054.730 Protection of Environment ENVIRONMENTAL...Averaging, Banking, and Trading for Certification § 1054.730 What ABT reports must I send to...

2010-07-01

217

Oxygen uptake and involvement of superoxide radicals upon photolysis of ketones in air-saturated aqueous alcohol, formate, amine or ascorbic acid solutions.  

Science.gov (United States)

The photolysis of acetophenone, benzophenone, 4-carboxybenzophenone and benzil was studied in air-saturated aqueous solution in the presence of alcohols. The overall reaction is an oxidation of 2-propanol to acetone. The quantum yield of oxygen uptake (Phi(-O(2))) increases with increasing 2-propanol concentration up to 0.9. The photoreaction can also be initiated by quenching of the ketone triplet state by ascorbic acid, formate or an amine e.g. triethylamine. Subsequent reactions of the involved radicals with oxygen yield the superoxide radical and eventually hydrogen peroxide. For the ketones in the presence of 3-30 mM ascorbic acid or triethylamine Phi(-O(2)) = 0.3-0.9. The specific properties of ketones, including 4-methoxyacetophenone and 2-acetonaphthone, the radicals involved and the pH and concentration dependences of Phi(-O(2)) are discussed. PMID:16506866

Görner, Helmut

2006-01-01

218

Rate constants for the reactions of halogenated organic radicals  

International Nuclear Information System (INIS)

Absolute rate constants have been measured by means of pulse radiolysis for the reactions of various halogenated aliphatic compounds (ethane derivatives, including the anaesthetics halothane, enflurane, isoflurane and methoxyflurane) with hydrated electrons and OH anion radicals, the reactions of halogenated carbon-centred radicals, derived thereby, with molecular oxygen, and the reactions of halogenated peroxyl radicals with various antioxidants (ascorbate, chlorpromazine promethazine, propyl gallate, ABTS) in aqueous solutions. All oxygen addition reactions occur essentially diffusion-controlled. This finding is correlated with the stereoelectronic properties of the primary carbon-centred radicals. The oxidative power of the halogenated peroxyl radicals reflects the inductive-l effect of the halogens and accordingly increases with the degree of halogen substitution, with fluorine substituents being particularly effective. The peroxyl radicals derived from freon 113, namely CClF2CClFOO radical and CCl2FCF2OO radical, have been identified as the best oxidants among these species. (author)

219

Bioactive compounds from several tropical fruits and correlation by multivariate analysis to free radical scavenger activity  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese O alto consumo de frutas tem sido associado à baixa incidência de doenças crônico-degenerativas, provavelmente devido à presença de compostos bioativos, como os antioxidantes, nestes alimentos. Os teores de compostos bioativos -ácido ascórbico, fenólicos totais, flavonóides e carotenóides totais - f [...] oram determinados em polpas obtidas a partir de 18 frutas tropicais adquiridas no Brasil. A atividade anti-radical livre foi avaliada pelo método ABTS. As frutas que apresentaram maior teor de compostos bioativos foram buriti, cajá-manga, canistel, murici, physalis, piquia e tucumã. Considerando a composição dos compostos bioativos analisados e as atividades anti-radical livre, as frutas foram divididas em 5 grupos, segundo Análise Hierárquica de Agrupamentos. Aplicando a Análise de Componentes Principais, a atividade anti-radical livre mostrou alta correlação com compostos fenólicos totais (r = 0,99) e flavonóides (r = 0,86); porém, a correlação encontrada foi muito pequena para ácido ascórbico (r = 0,02) e carotenóides totais (r = 0,08). Abstract in english High ingestion of fruits has been associated with low incidence of chronic-degenerative diseases, probably due to the presence of bioactive compounds in these foods, such as antioxidants. The levels of bioactive compounds - ascorbic acid, total phenolics, flavonoids and carotenoids - were determined [...] in 18 pulps obtained from tropical fruits acquired in Brazil. The free radical scavenger activity was evaluated by the ABTS assay. The fruits that showed higher levels of bioactive compounds were buriti, otaheite apple, egg-fruit, golden spoon, physalis, piquia and star nut palm. Considering the composition of bioactive compounds and free radical scavenger capacities the fruits were divided into five groups, according to Hierarchical Cluster Analysis. Applying Principal Component Analysis, free radical scavenger showed high correlation with total phenolic compounds (r = 0.99) and flavonoids (r = 0.86); however, the correlation was found to be very poor with ascorbic acid (r = 0.02) and with total carotenoids levels (r = 0.08).

Gisela P.M., Barreto; Marta T., Benassi; Adriana Z., Mercadante.

1856-18-01

220

Prostatic Fatty Acids and Cancer Recurrence Following Radical Prostatectomy for Early-Stage Prostate Cancer  

Science.gov (United States)

Objective: Results from some observational studies suggest that diet and energy balance influence the clinical course of early-stage prostate cancer. To evaluate possible mechanisms, we prospectively examined the relation between prostatic concentrations of fatty acids at diagnosis and cancer recurr...

221

Molecular dynamics simulations of arachidonic acid-derived pentadienyl radical intermediate complexes with COX-1 and COX-2: insights into oxygenation regio- and stereoselectivity.  

Science.gov (United States)

The two cyclooxygenase enzymes, COX-1 and COX-2, are responsible for the committed step in prostaglandin biosynthesis and are the targets of the nonsteroidal antiinflammatory drugs aspirin and ibuprofen and the COX-2 selective inhibitors, Celebrex, Vioxx, and Bextra. The enzymes are remarkable in that they catalyze two dioxygenations and two cyclizations of the native substrate, arachidonic acid, with near absolute regio- and stereoselectivity. Several theories have been advanced to explain the nature of enzymatic control over this series of reactions, including suggestions of steric shielding and oxygen channeling. As proposed here, selective radical trapping and spin localization in the substrate-derived pentadienyl radical intermediate can also be envisioned. Herein we describe the results of explicit, 10 ns molecular dynamics simulations of both COX-1 and COX-2 with the substrate-derived pentadienyl radical intermediate bound in the active site. The enzymes' influence on the conformation of the pentadienyl radical was investigated, along with the accessible space above and below the radical plane and the width of several channels to the active site that could function as access routes for molecular oxygen. Additional simulations demonstrated the extent of molecular oxygen mobility within the active site. The results suggest that spin localization is unlikely to play a role in enzymatic control of this reaction. Instead, a combination of oxygen channeling, steric shielding, and selective radical trapping appears to be responsible. This work adds a dynamic perspective to the strong foundation of static structural data available for these enzymes. PMID:16519515

Furse, Kristina E; Pratt, Derek A; Schneider, Claus; Brash, Alan R; Porter, Ned A; Lybrand, Terry P

2006-03-14

222

A computational study on Lewis acid-catalyzed diastereoselective acyclic radical allylation reactions with unusual selectivity dependence on temperature and epimer precursor.  

Science.gov (United States)

In stereoselective radical reactions, it is accepted that the configuration of the radical precursor has no impact on the levels of stereoinduction, as a prochiral radical intermediate is planar, with two identical faces, independently of its origin. However, Sibi and Rheault (J. Am. Chem. Soc. 2000, 122, 8873-8879) remarkably obtained different selectivities in the trapping of radicals originated from two epimeric bromides, catalyzed by chelating Lewis acids. The selectivity rationalization was made on the basis of different conformational properties of each epimer. However, in this paper we show that the two epimers have similar conformational properties, which implies that the literature proposal is unable to explain the experimental results. We propose an alternative mechanism, in which the final selectivity is dependent on different reaction rates for radical formation from each epimer. By introducing a different perspective of the reaction mechanism, our model also allows the rationalization of different chemical yields obtained from each epimer, a result not rationalized by the previous model. Adaptation to other radical systems, under different reaction conditions, is also possible. PMID:25375894

Georgieva, Miglena K; Santos, A Gil

2014-12-01

223

Syntheses, structural characterization, and DPPH radical scavenging activity of cocrystals of caffeine with 1- and 2-naphthoxyacetic acids  

Science.gov (United States)

Caffeine:1-naphthoxyacetic acid [(caf)(1-naa)] and caffeine:2-naphthoxyacetic acid [(caf)(2-naa)] cocrystals have been synthesized and single crystals were grown by slow evaporation technique. The structures of the grown crystals were elucidated using single crystal X-ray diffraction analysis. Both the cocrystals belong to the monoclinic crystallographic system with space group P21/c, Z = 4, and ? = ? = 90°, whereas ? = 111.4244(18)° for [(caf)(1-naa)] and ? = 109.281(6)° for [(caf)(2-naa)]. The crystal packing is predominantly stabilized by hydrogen bonding and ?-? stacking interactions. The presence of unionized -COOH functional group in both the cocrystals was identified by FTIR spectral analysis. Thermal behavior and stability of both the cocrystals were studied by TGA/DTA analyses. Solvent-free formation of these cocrystals was confirmed by powder X-ray diffraction analyses. The theoretical energy of cocrystals showed that the formers have higher energy than cocrystals 1 and 2. DPPH radical scavenging activity of cocrystals 1 and 2 is slightly greater than the formers.

Suresh Kumar, G. S.; Seethalakshmi, P. G.; Sumathi, D.; Bhuvanesh, N.; Kumaresan, S.

2013-03-01

224

The structure and properties of free radicals: An electron spin resonance study of radiation damage to nucleic acid and protein components and to some sulfur-substituted derivitives  

International Nuclear Information System (INIS)

When cellular systems are exposed to ionizing radiation the long-term effects may range from minor disturbances to such dramatic changes as mutations and cell death. The processes leading to these macroscopical injuries are primarily confined at the molecular level. In all models aimed at a description of the action of radiation at the molecular level the formation of free radicals (which are species containing unpaired electrons) is a central concept. The technique of ESR spectroscopy is uniquely suited to study free radicals, as it is based on resonance absorption of energy by unpaired electrons in a magnetic field. ESR spectroscopy makes it possible to detect free radicals and, in some cases, to identify them. In order to study free radicals by ESR it is necessary to build up a sufficient number of unpaired spins in the sample (approximately 1011 or more, depending on the shape of the resonance). This may be different techniques have been used to trap the induced radicals or to attain a sufficient steady state concentration level. A procedure which seems to contain a large amount of information is to irradiate at low temperatures, and, by subsequent heat-treatment of the sample to study the reactions and fate of the induced radicals. In this thesis single crystal studies of aromatic amino acids and pyrimidine derivitives together with some substituted purine derivitives are presented, and the results are discussed in relation to the present knowledge about radical formation in these classes of compounds. Single crystal studies of some sulfur-containing aromatic compounds have been presented with the purpose of shedding light on the electronic structure of sulfur-centred radicals. (JIW)

225

DEGRADATION OF ACRYLIC ACID-GRAFTED CELLULOSE IN AQUEOUS MEDIUM WITH RADICAL INITIATORS  

OpenAIRE

The chemical modification of cellulose by grafting reaction with Acrylic Acid (AA) considering different reaction factors was investigated. Natural polymers such as Santa Fe Cellulose, Microcrystalline Cellulose (Avicell) and Secondary Pulp were studied as substrates. pH effect; Ce (IV), Mn(VII) and Fenton as initiators; time and temperature polymerization were investigated. Grafting reachs a maximum, 90 % graft, at pH 7. A medium to weak C=0 band at 1715 cm"¹ for carboxylic group in FTIR sp...

AÍDA NEIRA; MIGUEL TARRAGA; ROSA CATALAN

2008-01-01

226

Living radical polymerization induced by radiation in the presence of dithiobenzoic acid  

International Nuclear Information System (INIS)

Polymerization of styrene (St) and n-butyl methacrylate (BMA) was induced by 60Co ? ray radiation in the presence of dithiobenzoic acid. The structure, molecular weight and polydispersity of the polymers were characterized by 1H NMR and GPC. The results exhibit characters of the living polymerization: narrow molecular weight polydispersity, molecular weight linearly increasing with conversion, and the living end group being retained in the polymeric products. Polymerization mechanism was also discussed

227

Effect of UV-C irradiation and low temperature storage on bioactive compounds, antioxidant enzymes and radical scavenging activity of papaya fruit.  

Science.gov (United States)

Mature green 'Maradol' papaya fruits were exposed to ultraviolet (UV)-C irradiation (1.48 kJ·m(-2)) and stored at 5 or 14 °C. Changes in total phenols, total flavonoids, enzymatic activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), as well as the scavenging activity against 2,2-diphenyl-1picrylhydrazyl (DPPH) and 3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radicals were investigated in peel and flesh tissues at 0, 5, 10 and 15 days of storage. UV-C irradiation increased significantly (P irradiation effect on radical scavenging of papaya peel could be attributed to increased flavonoid content. Papaya antioxidant system was activated by UV-C and cold storage by increasing phenolic content and antioxidant enzymatic activities as a defense response against oxidative-stress. PMID:25477649

Rivera-Pastrana, Dulce M; Gardea, Alfonso A; Yahia, Elhadi M; Martínez-Téllez, Miguel A; González-Aguilar, Gustavo A

2014-12-01

228

Measurements of the Hydroxyl Radical and Sulfuric Acid from the NOAA P3 during ITCT 2002  

Science.gov (United States)

A new chemical ionization mass spectrometer (CIMS) for measurement of OH and sulfuric acid was deployed on the ITCT 2002 mission. The wingpod mounted CIMS instrument weighed less than 600 lbs and used a total of less than 1 kW of 400 Hz power. Data was obtained on all of the science flights out of Monterey, CA. In general, very low OH number densities were observed on the flights that focused on high altitude transport of Asian pollution. On many occasions air parcels were intercepted containing enhanced levels of CO, NOy, and particulates. However, the OH levels in these air masses were very low and near the detection limit of the instrument of ~2e5 molec. cm-3. This result is consistent with the observed low dew points (TDsulfuric acid number densities were also usually very low (sulfuric acid strongly correlated with CO were observed in a few plumes of Asian origin. The P3 aircraft was also used to study the effects of ship emissions and pollutant transport into and out of West Coast metropolitan areas. Data from a good example of this type of experiment on May 8, 2002 will be presented. The first part of the flight was used to investigate ship emissions in the marine boundary layer and the last half explored San Francisco, Oakland and the Central Valley. During the ship plume study high levels of sulfuric acid (> 2e7 molec. cm-3) were observed that corresponded to transects of ship emission plumes. These sharp spikes were overlaid on a broad background of relatively high levels (> 5e6 molec. cm-3) of sulfuric acid in the marine boundary layer. This background level is much higher than in other portions of the marine boundary layer sampled on this mission and is approximately equal to the background levels in San Francisco or Los Angeles. These data along with elevated ozone, particulate sulfate and NOy values indicate that ship emissions are significantly perturbing the atmospheric chemistry of large portions of the marine boundary layer.

Huey, G.; Tanner, D.; Nowak, J.; Neuman, A.; Ryerson, T.; Nicks, D.; Brock, C.; Jakoubek, R.; Sullivan, A.; Orsini, D.; Holloway, J.; Dunlea, E.; Trainer, M.; Hubler, G.; Parrish, D.; Fehsenfeld, F.

2002-12-01

229

A combination study of spin-trapping, LC/ESR and LC/MS on carbon-centred radicals formed from lipoxygenase-catalysed peroxidation of eicosapentaenoic acid  

OpenAIRE

Increased evidence from animal and in vitro cellular research indicates that the metabolism of eicosapentaenoic acid (EPA) can inhibit carcinogenesis in many cancers. Free radical-mediated peroxidation is one of many possible mechanisms to which EPA’s anti-cancer activity has been attributed. However, no direct evidence has been obtained for the formation of any EPA-derived radicals. In this study, a combination of LC/ESR and LC/MS was used with ?-[4-pyridyl 1-oxide]-N-tert-butyl nitrone t...

Shan, Zhen; Yu, Qingfeng; Purwaha, Preeti; Guo, Bin; Qian, Steven Y.

2009-01-01

230

Low field CIDNP of amino acids and proteins: characterization of transient radicals and NMR sensitivity enhancement  

OpenAIRE

A new method for measuring and exploiting the magnetic field dependence of chemically induced dynamic nuclear polarization (CIDNP) is described. A solution of an amino acid or protein together with a flavin photosensitizer is irradiated with laser light at a position in the bore of a superconducting NMR magnet where the field is between 0.1 T and 7.0 T. The polarized sample is then transferred by rapid injection into an NMR tube at the centre of the magnet (at 9.4 T), where the spectrum is re...

Lyon, Ce; Lopez, Jj; Cho, Bm; Hore, Pj

2002-01-01

231

Free radical derivatives formed from cyclooxygenase-catalyzed dihomo-?-linolenic acid peroxidation can attenuate colon cancer cell growth and enhance 5-fluorouracil?s cytotoxicity  

Directory of Open Access Journals (Sweden)

Full Text Available Dihomo-?-linolenic acid (DGLA and its downstream fatty acid arachidonic acid (AA are both nutritionally important ?–6 polyunsaturated fatty acids (?–6s. Evidence shows that, via COX-mediated peroxidation, DGLA and its metabolites (1-series prostaglandins are associated with anti-tumor activity, while AA and its metabolites (2-series prostaglandins could be tightly implicated in various cancer diseases. However, it still remains a mystery why DGLA and AA possess contrasting bioactivities. Our previous studies showed that DGLA could go through an exclusive C-8 oxygenation pathway during COX-catalyzed lipid peroxidation in addition to a C-15 oxygenation pathway shared by both DGLA and AA, and that the exclusive C-8 oxygenation could lead to the production of distinct DGLA?s free radical derivatives that may be correlated with DGLA?s anti-proliferation activity. In the present work, we further investigate the anti-cancer effect of DGLA?s free radical derivatives and their associated molecular mechanisms. Our study shows that the exclusive DGLA?s free radical derivatives from C-8 oxygenation lead to cell growth inhibition, cell cycle arrest and apoptosis in the human colon cancer cell line HCA-7 colony 29, probably by up-regulating the cancer suppressor p53 and the cell cycle inhibitor p27. In addition, these exclusive radical derivatives were also able to enhance the efficacy of 5-Fluorouracil (5-FU, a widely used chemo-drug for colon cancer. For the first time, we show how DGLA?s radical pathway and metabolites are associated with DGLA?s anti-cancer activities and able to sensitize colon cancer cells to chemo-drugs such as 5-FU. Our findings could be used to guide future development of a combined chemotherapy and dietary care strategy for colon cancer treatment.

Yi Xu

2014-01-01

232

In vitro evaluation of ABT-719, a novel DNA gyrase inhibitor.  

OpenAIRE

ABT-719 (A-86719.1) is the first compound of a new class of novel DNA gyrase inhibitors, the 2-pyridones, with potent antibacterial activity against gram-positive, gram-negative, and anaerobic organisms. ABT-719 was more active than ciprofloxacin, sparfloxacin, and clinafloxacin against gram-positive bacteria. ABT-719 was particularly active against Staphylococcus aureus (MIC at which 90% of the isolates were inhibited [MIC90] = 0.015 micrograms/ml) and Streptococcus pneumoniae (MIC90 = 0.03 ...

Flamm, R. K.; Vojtko, C.; Chu, D. T.; Li, Q.; Beyer, J.; Hensey, D.; Ramer, N.; Clement, J. J.; Tanaka, S. K.

1995-01-01

233

DEGRADATION OF ACRYLIC ACID-GRAFTED CELLULOSE IN AQUEOUS MEDIUM WITH RADICAL INITIATORS  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in english The chemical modification of cellulose by grafting reaction with Acrylic Acid (AA) considering different reaction factors was investigated. Natural polymers such as Santa Fe Cellulose, Microcrystalline Cellulose (Avicell) and Secondary Pulp were studied as substrates. pH effect; Ce (IV), Mn(VII) and [...] Fenton as initiators; time and temperature polymerization were investigated. Grafting reachs a maximum, 90 % graft, at pH 7. A medium to weak C=0 band at 1715 cm"¹ for carboxylic group in FTIR spectroscopy is presented. Santa Fe and Avicel cellulose grafted whith AA at 17 hours are degraded. Secondary pulp with Fenton at 50-60 and 70 °C at 17 hours are degraded too. The degradation of polymers at long reaction times at 17 hours and 70°C were analized by FTIR spectroscopy and electronic microscopy analysis (SEM).

AÍDA, NEIRA; MIGUEL, TARRAGA; ROSA, CATALAN.

1399-14-01

234

Dimer esters in ?-pinene secondary organic aerosol: effect of hydroxyl radical, ozone, relative humidity and aerosol acidity  

Science.gov (United States)

The formation of secondary organic aerosol (SOA) from both ozonolysis and hydroxyl radical (OH)-initiated oxidation of ?-pinene under conditions of high nitric oxide (NO) concentrations with varying relative humidity (RH) and aerosol acidity was investigated in the University of North Carolina dual outdoor smog chamber facility. SOA formation from ozonolysis of ?-pinene was enhanced relative to that from OH-initiated oxidation in the presence of initially high NO conditions. However, no effect of RH on SOA mass was evident. Ozone (O3)-initiated oxidation of ?-pinene in the presence of ammonium sulfate (AS) seed coated with organic aerosol from OH-initiated oxidation of ?-pinene showed reduced nucleation compared to ozonolysis in the presence of pure AS seed aerosol. The chemical composition of ?-pinene SOA was investigated by ultra-performance liquid chromatography/electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (UPLC/ESI-HR-Q-TOFMS), with a focus on the formation of carboxylic acids and high-molecular weight dimer esters. A total of eight carboxylic acids and four dimer esters were identified, constituting between 8 and 12% of the total ?-pinene SOA mass. OH-initiated oxidation of ?-pinene in the presence of nitrogen oxides (NOx) resulted in the formation of highly oxidized carboxylic acids, such as 3-methyl-1,2,3-butanetricarboxylic acid (MBTCA) and diaterpenylic acid acetate (DTAA). The formation of dimer esters was observed only in SOA produced from the ozonolysis of ?-pinene in the absence of NOx, with increased concentrations by a~factor of two at higher RH (50-90%) relative to lower RH (30-50%). The increased formation of dimer esters correlates with an observed increase in new particle formation at higher RH due to nucleation. Increased aerosol acidity was found to have a negligible effect on the formation of the dimer esters. SOA mass yield did not influence the chemical composition of SOA formed from ?-pinene ozonolysis with respect to carboxylic acids and dimer esters. The results support the formation of the high-molecular weight dimer esters through gas-phase reactions of the stabilized Criegee Intermediate (sCI) formed from the ozonolysis of ?-pinene. The high molecular weight and polar nature of dimer esters formed in the gas-phase may explain increased particle number concentration as a~result of homogenous nucleation. Since three of these dimer esters (i.e., pinyl-diaterpenyl ester (MW 358), pinyl-diaterebyl ester (MW 344) and pinonyl-pinyl ester (MW 368)) have been observed in both laboratory-generated and ambient fine organic aerosol samples, we conclude that the dimer esters observed in this study can be used as tracers for the O3-initiated oxidation of ?-pinene, and are therefore indicative of enhanced anthropogenic activities, and that the high molecular weight and low volatility esters result in homogenous nucleation under laboratory conditions, increasing the particle number concentration.

Kristensen, K.; Cui, T.; Zhang, H.; Gold, A.; Glasius, M.; Surratt, J. D.

2013-12-01

235

Inhibition of oxygen radical formation by methylene blue, aspirin, or alpha-lipoic acid, prevents bacterial-lipopolysaccharide-induced fever.  

Science.gov (United States)

Phagocytic cells contain NADPH oxidase that they use for host defense by catalyzing the production of superoxide. Bacterial lipopolysaccharide (LPS) has been found to stimulate NADPH oxidase in mobile and sessile macrophages and microglia. It also evokes fever in homeothermic animals and men, a reaction mediated by central nervous system (CNS) activities. The purpose of the present study was to determine whether reactive oxygen species are involved in LPS-induced fever. In rabbits we found that plasma hydroperoxide levels increased and catalase activity decreased 15 min after LPS injection and that fever started with a similar latency, while plasma levels of tumor necrosis factor-alpha (TNFalpha) increased 30 min after the injection. Treating rabbits with methylene blue or aspirin did not affect TNFalpha secretion but prevented the LPS-induced rise of hydroperoxides and the inactivation of catalase, abolishing fever. Incubation of human blood with nitroblue tetrazolium and LPS increased the number of formazan-positive neutrophils from 10 +/- 5 to 52 +/- 9%. Adding LPS to blood preincubated with either methylene blue, alpha-lipoic acid, or aspirin respectively decreased the number of formazan-positive neutrophils to 0.9 +/- 0.8, 0.8 +/- 0.9, or 2.0 +/- 0.9%, disclosing the antioxidant capacity of these drugs. Systemic application of 80 mg/kg alpha-lipoic acid elicited heat-loss reactions within 15 min and decreased core temperature by 2.2 +/- 0.3 degrees C within 2 h. Alpha-lipoic acid applied 45 min after LPS induced antipyresis within 15 min, and this antipyresis was associated with a decrease of elevated hydroperoxide levels and restoration of catalase activity. Our results show that fever is prevented when the production of reactive oxygen species is blocked and that an elevated body temperature returns to normal when oxygen radical production decreases. Estimation of plasma dihydrolipoic acid (DHLA) levels following injection of 80 mg/kg alpha-lipoic acid in afebrile and febrile rabbits revealed that this acid is converted into DHLA, which in afebrile rabbits increased the plasma DHLA concentration from 2.22 +/- 0.26 microg/ml to peak values of 8.60 +/- 2.28 microg/ml DHLA within 30 min and which in febrile rabbits increased it from 0.84 +/- 0.22 microg/ml to peak values of 3.90 +/- 0.94 microg/ml within 15 min. Methylene blue, aspirin, and alpha-lipoic acid, which all cross the blood-brain barrier, seem to act not only on peripheral tissues but also on the CNS. Brain structures that have been shown to sense oxidative stress are vicinal thiol groups attached to the NMDA subtype of glutamate receptor. Their reduction by thiol-reducing drugs like dithiothreitol or DHLA has been found to increase glutamate-mediated neuronal excitability, while the opposite effect has been observed after their oxidation. Because we found that systemic application of alpha-lipoic acid in the afebrile state elicits hypothermia and in the febrile state is antipyretic, we think this type of NMDA receptor is involved in thermoregulation and that oxidation of its thiol groups induces fever. It appears that temperature homeostasis can be maintained only if the redox homeostasis of the brain is guaranteed. PMID:12841635

Riedel, Walter; Lang, Uwe; Oetjen, Ulrich; Schlapp, Ulrike; Shibata, Masaaki

2003-05-01

236

Melt Free-Radical Grafting of Maleic Anhydride onto Biodegradable Poly(lactic acid by Using Styrene as A Comonomer  

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Full Text Available Maleic anhydride (MA was grafted onto poly(lactic acid (PLA in the presence of styrene (St by using a free-radical grafting methodology. The grafting degree (Dg of MA was increased from 0.65 wt % to 1.1 wt % with the St/MA ratio up to 2/1, where the grafting efficiency (Eg of MA was 27%. However, both Dg and Eg were decreased with further increasing of the St/MA ratio to 4/1. The Dg of MA increased with MA concentration and showed a maximum at 180 °C in the temperature range of 165 °C–190 °C. The grafting mechanisms of MA in the presence of St are analyzed based on titration, thermogravimetric analysis and infrared results, i.e., MA is grafted onto PLA chains via single monomers and a charge-transfer-complex (CTC at St/MA ratios of ? 1/1, while dominantly via St-co-MA oligomers at St/MA ratios of around 2/1. Copolymerization rather than grafting of St and MA occurs at St/MA ratios of around 4/1. The thermal stability of PLA was compromised to a certain extent by the grafting of MA, resulting in reductions in the decomposition temperature (Td-5% and molecular weight of the PLA. In addition, the crystallization and melting temperatures of the PLA were slightly reduced after the grafting.

Piming Ma

2014-05-01

237

Radical Scavenging Capacity and Antioxidant Activity of the Vitamin E Extracted from Palm Fatty Acid Distillate by Sequential Cooling Hexane  

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Full Text Available The radical scavenging capacity and antioxidant activity of the vitamin E extracted from palm fatty acid distillate by the sequential cooling hexane were compared to those of the synthetic antioxidants including butylated hydroxyanisole (BHA, 2,6-di-tert-butyl-4-methylphenol (BHT, pyrogallol (PG, tert-butylhydroquinone (TBHQ and commercial Alpha-tocopherol. The extracted vitamin E contained 2,509.57, 9.24, 157.85, 6.70, 1,779.92, 3.97, 2,376.38, 818.80 and 7,662.45 ppm of Alpha-, Beta-, Gamma-, Delta-tocopherol and Alpha-, Beta-, Gamma-, Delta-tocotrienol, and total vitamin E, respectively. The maximum 2,2-diphenyl-1-picrylhydrazyl (DPPH scavenging capacity of 20 ppm extracted vitamin E was 89%. The antioxidant activity determined by the methods of reducing power and ferric thiocyanate indicated that the 2.5 ppm extracted vitamin E could inhibit the oxidation of linoleic acid emulsion for more than 80% within 1 day. The superoxide scavenging activity of the extracted vitamin E was greater than those of the BHT, commercial Alpha-tocopherol, and PG, respectively. The antioxidant activity of the extracted vitamin E was 91% which was similar to those of the BHT and synthetic Alpha-tocopherol. The total-vitamin E remained 73% after heating at 190°C for 3 h. The tocopherol derivatives were more heat-stable than the tocotrienol derivatives while Gamma-tocopherol was the most heat-stable derivative. The concentration of total-vitamin E stored at 30°C for 120 days remained about 87% while the concentrations of vitamin E derivatives reduced by 2-20%.

Ronnakorn Sroynak

2013-03-01

238

Forgotten radicals in biology.  

Science.gov (United States)

Redox reactions play key roles in intra- and inter-cellular signaling, and in adaptative processes of tissues towards stress. Among the major free radicals with essential functions in cells are reactive oxygen species (ROS) including superoxide anion (O2 (•-)), hydroxyl radical ((•)OH) and reactive nitrogen species (RNS) such as nitric oxide ((•)NO). In this article, we review the forgotten and new radicals with potential relevance to cardiovascular pathophysiology. Approximately 0.3% of O2 (•-) present in cytosol exists in its protonated form: hydroperoxyl radical (HO2 (•)). Water (H2O) can be split into two free radicals: (•)OH and hydrogen radical (H(•)). Several free radicals, including thiyl radicals (RS(•)) and nitrogen dioxide (NO2 (•)) are known to isomerize double bonds. In the omega-6 series of poly-unsaturated fatty acids (PUFAs), cis-trans isomerization of ?-linolenate and arachidonate catalyzed by RS(•) has been investigated. Evidence is emerging that hydrogen disulphide (H2S) is a signaling molecule in vivo which can be a source of free radicals. The Cu-Zn superoxide dismutase (SOD) enzyme can oxidize the ionized form of H2S to hydro-sulphide radical: HS(•). Recent studies suggest that H2S plays an important function in cardiovascular functions. Carbonate radical, which can be formed when (•)OH reacts with carbonate or bicarbonate ions, is also involved in the activity of Cu-Zn-SOD. Recently, it has been reported that carbonate anion were potentially relevant oxidants of nucleic acids in physiological environments. In conclusion, there is solid evidence supporting the formation of many free radicals by cells leading which may play an important role in their homeostasis. PMID:23675099

Luc, Rochette; Vergely, Catherine

2008-12-01

239

Measurement of the diene conjugated form of linoleic acid in plasma by high performance liquid chromatography: a questionable non-invasive assay of free radical activity?  

Science.gov (United States)

It has been previously reported that the main diene-conjugated fatty acid in human plasma is a non-oxygen containing linoleic acid isomer (PL-9, 11-LA'). It has also been proposed that this isomer can be used as a specific marker of free radical-mediated lipid peroxidation in humans. Here we report that the in vitro induction of lipid peroxidation in human and rat blood with either UV irradiation or phenylhydrazine failed to increase the plasma levels of this isomer. The induction of lipid peroxidation in vivo in rats pretreated with either phenylhydrazine or bromotrichloromethane also failed to increase the plasma levels of this isomer. These findings demonstrate that PL-9, 11-LA' cannot be used as an in vivo marker of free radical-mediated lipid peroxidation in rats and casts doubts on its validity as a specific marker in humans. PMID:4075442

Thompson, S; Smith, M T

1985-11-01

240

In Vitro Activities of ABT-773 and Other Antimicrobials against Human Mycoplasmas  

OpenAIRE

The in vitro susceptibilities of 103 Mycoplasma pneumoniae isolates, 14 Mycoplasma hominis isolates, 12 Mycoplasma fermentans isolates, and 24 Ureaplasma species to ABT-773, an investigational ketolide, and seven other agents were determined. For M. pneumoniae, the ABT-773 MIC at which 90% of isolates are inhibited (MIC90; ?0.001 ?g/ml) was comparable to those of azithromycin, clarithromycin, and erythromycin and at least 128-fold lower than those of levofloxacin, gatifloxacin, moxifloxaci...

Waites, Ken B.; Crabb, Donna M.; Duffy, Lynn B.

2003-01-01

241

Antioxidative effects of curcumin and its analogues against the free-radical-induced peroxidation of linoleic acid in micelles.  

Science.gov (United States)

Curcumin (1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione, 1) is a yellow ingredient isolated from turmeric (curcumin longa). Many health benefits have been claimed for curcumin, and these have generally been ascribed to its radical-trapping antioxidant properties. In order to find more active antioxidants with 1 as the lead compound, we synthesized curcumin analogues, i.e., 1,7-bis(3,4-dihydroxyphenyl)-1,6-heptadiene-3,5-dione (2), 1-(3,4-dihydroxyphenyl)-7-(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione (3), 1-(4-hydroxy-3-methoxyphenyl)-7-(4-hydroxyphenyl)-1,6-heptadiene-3,5-dione (4), 1,7-bis (4-hydroxyphenyl)-1,6-heptadiene-3,5-dione (5), 1,7-bis(3,4-dimethoxyphenyl)-1,6-heptadiene-3,5-dione (6), 1,7-bis(4-methoxyphenyl)-1,6-heptadiene-3,5-dione (7), and 1,7-diphenyl-1,6-heptadiene-3,5-dione (8). Antioxidative effects of curcumin and these analogues against the peroxidation of linoleic acid were studied in sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) micelles. The peroxidation was initiated thermally by a water-soluble initiator 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH), and reaction kinetics were monitored by the formation of linoleic acid hydroperoxides. Kinetic analysis of the antioxidation process demonstrates that these compounds, except 6, 7 and 8, are effective antioxidants in micelles by H-atom abstraction from the phenolic groups. Compounds 2 and 3, which bear ortho-diphenoxyl functionality, possess significantly higher antioxidant activity than curcumin and other analogues, and the 4-hydroxy-3-methoxyphenyl group also plays an important role in the antioxidative activity. In addition, the synergistic antioxidant effect of these compounds with alpha-tocopherol (vitamin E) in micelles was also studied by following the formation of linoleic acid hydroperoxides and the consumption of alpha-tocopherol. It was found that these compounds could not synergistically interact with alpha-tocopherol in micelles. PMID:19173279

Dai, Fang; Chen, Wei-Feng; Zhou, Bo; Yang, Li; Liu, Zhong-Li

2009-09-01

242

Effects of Various Cooking Methods on Content, Oxygen Radical Absorbance Capacity, and Bioaccessibility of Caffeoylquinic Acids in Ligularia fischeri (Ledeb.) Turcz, Gom-Chi  

OpenAIRE

We hypothesized that cooking methods generally applied to Gom-chi preparation such as blanching, pan frying, and microwaving could change content, oxygen radical absorbance capacity (ORAC), and bioaccessibility of caffeoylquinic acids (CQAs). Mono-, di-, and tri-CQAs were identified and quantified by using an ultra-performance liquid chromatograph-photodiode array detector. In vitro biomimick system was performed for assessing the bioaccessibility of CQAs. The free r...

Yu-Ra Son; Soon-Mi Shim

2014-01-01

243

Silver-Mediated Radical Cyclization of Alkynoates and ?-Keto Acids Leading to Coumarins via Cascade Double C-C Bond Formation.  

Science.gov (United States)

A novel and convenient silver-mediated radical cyclization method for the synthesis of coumarin derivatives via the direct difunctionalization of alkynoates with ?-keto acids through double C-C bond formation under mild conditions has been developed. This new method is highly efficient and practical, and the starting materials are readily prepared. The present method should provide a useful strategy for the construction of coumarin motifs. PMID:25562802

Yan, Kelu; Yang, Daoshan; Wei, Wei; Wang, Fen; Shuai, Yuanyuan; Li, Qiannan; Wang, Hua

2015-02-01

244

Radical scavenging potential of phenolics from Bryophyllum pinnatum (LAM.) OKEN.  

Science.gov (United States)

Optimization of the extraction process of phenolics from Bryophyllum pinnatum was carried out using response-surface methodology (RSM). The effect of different variables such as ratio of solvents, plant material/solvent ratio, extraction time, and temperature were investigated. An optimal phenolics yield of 7.952 mg/g gallic acid equivalence (GAE) was achieved at reduced levels of methanol/water ratio (1:1, v/v). During optimization, the product yield was enhanced by ?2-fold at reduced extraction solvent (methanol/water) up to 37%. Validation of the RSM model for extraction of total phenolic content (TPC) was confirmed by high-performance liquid chromatography (HPLC) analysis. The obtained experimental values were in good agreement with the predicted values, thereby indicating the appropriateness of the model generated. Phenolic extracts from B. pinnatum were further examined by 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), and 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) methods for determining the radical scavenging activities. EC(50) values of B. pinnatum extracts (BPEs) obtained by these methods were in accordance with the amount of phenolics present in the extract. Significant correlation was found between total phenolic content and antioxidant activities (p < 0.05). PMID:21660869

Gupta, Suneel; Banerjee, Rintu

2011-01-01

245

Pulse radiolysis and cyclic voltammetry studies of redox properties of phenothiazine radicals  

Energy Technology Data Exchange (ETDEWEB)

One-electron transfer equilibria between seven phenothiazines were characterized by pulse radiolysis, producing radical-cations via oxidation by Br{sub 2} {sup .-} or (SCN){sub 2} {sup .-} radicals. The reduction potentials of the phenothiazine radicals were determined by cyclic voltammetry. As an independent check, the redox equilibrium between one phenothiazine and the redox indicator ABTS was investigated. The data establish phenothiazines as useful indicators for radical redox properties. However, there are potential problems of aggregation, additional reactions with Br{sup -}/Br{sub 2} {sup .-} and reactivity of the radicals towards buffers or other nucleophiles.

Madej, Edyta [Gray Cancer Institute, PO Box 100, Mount Vernon Hospital, Northwood, Middlesex HA6 2JR (United Kingdom)]. E-mail: madej@gci.ac.uk; Wardman, Peter [Gray Cancer Institute, PO Box 100, Mount Vernon Hospital, Northwood, Middlesex HA6 2JR (United Kingdom)

2006-09-15

246

Kinetics of formation and reactions of thiyl radicals in aqueous solution  

Energy Technology Data Exchange (ETDEWEB)

Very few kinetic data are available that describe reactions of sulfur-centered radicals, despite their importance in biological systems. Thiyl radicals may be produced by generating carbon-centered radicals using visible laser flash photolysis and taking advantage of the repair reaction. Thiyl radicals are difficult to detect directly and require the use of a kinetic probe such as ABTS{sup 2{minus}} or TMPD. Kinetic studies of these reactions as well as reactions of ethanethiyl radicals with hexaaqua complexes of chromium(II), vanadium(II), and iron(II) are described.

Huston, P.; Espenson, J.H.; Bakac, A. (Iowa State Univ., Ames (United States))

1992-03-04

247

Anti-inflammatory, cyclooxygenase (COX)-2, COX-1 inhibitory, and free radical scavenging effects of Rumex nepalensis.  

Science.gov (United States)

Evaluation of the topical anti-inflammatory activity of chloroform and ethyl acetate extracts of RUMEX NEPALENSIS roots in a TPA-induced acute inflammation mouse model demonstrated a significant reduction in ear edema. The extracts were further tested on purified enzymes for COX-1 and COX-2 inhibition to elucidate their mechanism of action, and a strong inhibition was observed. Six anthraquinones and two naphthalene derivatives were isolated from the ethyl acetate extract. Among the isolated compounds, emodin was found to be a potent inhibitor with slight selectivity towards COX-2, and nepodin exhibited selectivity towards COX-1. Emodin, endocrocin, and nepodin also exhibited significant topical anti-inflammatory activity in mice. Interestingly, nepodin showed better radical scavenging activity than trolox and ascorbic acid against DPPH and ABTS radicals. The strong radical scavenging activity of chloroform and ethyl acetate extracts could be explained by the presence of nepodin as well as by the high phenolic content of the ethyl acetate extract. Thus, the anti-inflammatory effect of R. NEPALENSIS roots was assumed to be mediated through COX inhibition by anthraquinones and naphthalene derivatives and through the radical scavenging activities of naphthalene derivatives. PMID:20379952

Gautam, Raju; Karkhile, Kailas V; Bhutani, Kamlesh K; Jachak, Sanjay M

2010-10-01

248

Free Radical Scavenging Activity and Reducing Capacity of Five Southern Thai Indigenous Vegetable Extracts  

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Full Text Available The phenolic compounds of five southern Thai indigenous vegetables including Mon-pu (Glochidion wallichianum Muell Arg, Cha-plu (Piper sarmentosum Roxb., white popinac (Leucaena leucocephala de Wit., djenkol tree (Archidendrom jiringa I. C. Nielsen. and stink bean (Parkia speciosa Hassk. were extracted using different solvents (50 % acetone, 80 % methanol and distilled water at a ratio of sample to extracting medium of 1:25 (w/v. The extracts were analyzed for total phenolic content using the Folin-Ciocalteu procedure, free radical scavenging capacity by using 2’,2’-azinobis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS and 1,1-diphenyl-2-picrylhydrazyl (DPPH methods, and reducing capacity by using a ferric reducing antioxidant power (FRAP assay. The acetone extracts of all plants possessed the highest total phenolic content followed by the methanolic and distilled water extracts, respectively. The highest total phenolic content was found in the acetone extracts of Mon-pu and white popinac (p < 0.05. The acetone extracts of all plants showed higher free radical scavenging capacity and reducing capacity than those of their methanolic and water extracts counterparts, respectively (p < 0.05. Among all plants tested, the extracts of Mon-pu extracted with all extracting media exhibited the highest free radical scavenging and reducing abilities (p < 0.05. The present study suggested that the acetone extract of Mon-pu was a potential source of natural antioxidants.

Worawan PANPIPAT

2010-01-01

249

Protective effect of aqueous extract from Spirulina platensis against cell death induced by free radicals  

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Full Text Available Abstract Background Spirulina is a commercial alga well known to contain various antioxidants, especially phycocyanin. Apart from being sold as a nutraceutical, Spirulina is incorporated as a functional ingredient in food products and beverages. Most of the previous reports on antioxidant activity of Spirulina were based on chemical rather than cell-based assays. The primary objective of this study was to assess the antioxidant activity of aqueous extract from Spirulina based on its protective effect against cell death induced by free radicals. Methods The antioxidant activity of the cold water extract from food-grade Spirulina platensis was assessed using both chemical and cell-based assays. In the cell-based assay, mouse fibroblast cells (3T3 cells were incubated for 1 h in medium containing aqueous extract of Spirulina or vitamin C (positive control at 25, 125 and 250 ?g/mL before the addition of 50 ?M 1,1-diphenyl-2-picrylhydrazyl (DPPH or 3-ethylbenzothiazoline-6-sulfonic acid (ABTS. The cells were incubated for another 24 h before being assessed for cell death due to apoptosis using the Cell Death Detection ELISA Kit. Spectrophotometric assays based on DPPH and ABTS were also used to assess the antioxidant activity of the extract compared to vitamin C and vitamin E (positive controls. Results Spirulina extract did not cause cytotoxic effect on 3T3 cells within the range of concentrations tested (0 - 250 ?g/mL. The extract reduced significantly (p Conclusions The results showed that aqueous extract of Spirulina has a protective effect against apoptotic cell death due to free radicals. The potential application of incorporating Spirulina into food products and beverages to enhance their antioxidant capacity is worth exploring.

Radhakrishnan Ammu

2010-09-01

250

Reactivity of hypotaurine and cysteine sulfinic acid toward carbonate radical anion and nitrogen dioxide as explored by the peroxidase activity of Cu,Zn superoxide dismutase and by pulse radiolysis.  

Science.gov (United States)

Hypotaurine and cysteine sulfinic acid are known to be readily oxidized to the respective sulfonates, taurine and cysteic acid, by several oxidative agents that may be present in biological systems. In this work, the relevance of both the carbonate anion and nitrogen dioxide radicals in the oxidation of hypotaurine and cysteine sulfinic acid has been explored by the peroxidase activity of Cu,Zn superoxide dismutase (SOD) and by pulse radiolysis. The extent of sulfinate oxidation induced by the system SOD/H2O2 in the presence of bicarbonate (CO3(•-) generation), or nitrite ((•)NO2 generation) has been evaluated. Hypotaurine is efficiently oxidized by the carbonate radical anion generated by the peroxidase activity of Cu,Zn SOD. Pulse radiolysis studies have shown that the carbonate radical anion reacts with hypotaurine more rapidly (k = 1.1 × 10(9) M(-1)s(-1)) than nitrogen dioxide (k = 1.6 × 10(7) M(-1)s(-1)). Regarding cysteine sulfinic acid, it is less reactive with the carbonate radical anion (k = 5.5 × 10(7) M(-1)s(-1)) than hypotaurine. It has also been observed that the one-electron transfer oxidation of both sulfinates by the radicals is accompanied by the generation of transient sulfonyl radicals (RSO2(•)). Considering that the carbonate radical anion could be formed in vivo at high level from bicarbonate, this radical can be included in the oxidants capable of performing the last metabolic step of taurine biosynthesis. Moreover, the protective effect exerted by hypotaurine and cysteine sulfinate on the carbonate radical anion-mediated tyrosine dimerization indicates that both sulfinates have scavenging activity towards the carbonate radical anion. However, the formation of transient reactive intermediates during sulfinate oxidation by carbonate anion and nitrogen dioxide radical may at the same time promote oxidative reactions. PMID:25156684

Baseggio Conrado, A; D'Angelantonio, M; Torreggiani, A; Pecci, L; Fontana, M

2014-11-01

251

Modeling nitrous acid and its impact on ozone and hydroxyl radical during the Texas Air Quality Study 2006  

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Full Text Available Nitrous acid (HONO mixing ratios for the Houston metropolitan area were simulated with the Community Multiscale Air Quality (CMAQ Model for an episode during the Texas Air Quality Study (TexAQS II in August/September 2006 and compared to in-situ MC/IC (mist-chamber/ion chromatograph and long path DOAS (Differential Optical Absorption Spectroscopy measurements at three different altitude ranges. Several HONO sources were accounted for in simulations, such as gas phase formation, direct emissions, nitrogen dioxide (NO2 hydrolysis, photo-induced formation from excited NO2 and photo-induced conversion of NO2 into HONO on surfaces covered with organic materials. Compared to the gas-phase HONO formation there was about a tenfold increase in HONO mixing ratios when additional HONO sources were taken into account, which improved the correlation between modeled and measured values. Concentrations of HONO simulated with only gas phase chemistry did not change with altitude, while measured HONO concentrations decrease with height. A trend of decreasing HONO concentration with altitude was well captured with CMAQ predicted concentrations when heterogeneous chemistry and photolytic sources of HONO were taken into account. Heterogeneous HONO production mainly accelerated morning ozone formation, albeit slightly. Also HONO formation from excited NO2 only slightly affected HONO and ozone (O3 concentrations. Photo-induced conversion of NO2 into HONO on surfaces covered with organic materials turned out to be a strong source of daytime HONO. Since HONO immediately photo-dissociates during daytime its ambient mixing ratios were only marginally altered (up to 0.5 ppbv, but significant increase in the hydroxyl radical (OH and ozone concentration was obtained. In contrast to heterogeneous HONO formation that mainly accelerated morning ozone formation, inclusion of photo-induced surface chemistry influenced ozone throughout the day.

B. H. Czader

2012-08-01

252

Modeling nitrous acid and its impact on ozone and hydroxyl radical during the Texas Air Quality Study 2006  

Directory of Open Access Journals (Sweden)

Full Text Available Nitrous acid (HONO mixing ratios for the Houston metropolitan area were simulated with the Community Multiscale Air Quality (CMAQ model for an episode during the Texas Air Quality Study (TexAQS II in August/September 2006 and compared to in-situ MC/IC (mist-chamber/ion chromatograph and long path DOAS (Differential Optical Absorption Spectroscopy measurements at three different altitudes. Several HONO sources were accounted for in simulations, such as gas phase formation, direct emissions, nitrogen dioxide (NO2* hydrolysis, photo-induced formation from excited NO2* and photo-induced conversion of NO2 into HONO on surfaces covered with organic materials. Compared to the gas-phase HONO formation there was about a tenfold increase in HONO mixing ratios when additional HONO sources were taken into account, which improved the correlation between modeled and measured values. Concentrations of HONO simulated with only gas phase chemistry did not change with altitude, while measured HONO concentrations decrease with height. A trend of decreasing HONO concentration with altitude was well captured with CMAQ predicted concentrations when heterogeneous chemistry and photolytic sources of HONO were taken into account. Heterogeneous HONO production mainly accelerated morning ozone formation, albeit slightly. Also HONO formation from excited NO2 only slightly affected HONO and ozone (O3 concentrations. Photo-induced conversion of NO2 into HONO on surfaces covered with organic materials turned out to be a strong source of daytime HONO. Since HONO immediately photo-dissociates during daytime its ambient mixing ratios were only marginally altered (up to 0.5 ppbv, but significant increase in the hydroxyl radical (OH and ozone concentration was obtained. In contrast to heterogeneous HONO formation that mainly accelerated morning ozone formation, inclusion of photo-induced surface chemistry influenced ozone throughout the day.

B. H. Czader

2012-02-01

253

Radical-generating coordination complexes as tools for rapid and effective fragmentation and fluorescent labeling of nucleic acids for microchip hybridization.  

Energy Technology Data Exchange (ETDEWEB)

DNA microchip technology is a rapid, high-throughput method for nucleic acid hybridization reactions. This technology requires random fragmentation and fluorescent labeling of target nucleic acids prior to hybridization. Radical-generating coordination complexes, such as 1,10-phenanthroline-Cu(II) (OP-Cu) and Fe(II)-EDTA (Fe-EDTA), have been commonly used as sequence nonspecific 'chemical nucleases' to introduce single-strand breaks in nucleic acids. Here we describe a new method based on these radical-generating complexes for random fragmentation and labeling of both single- and double-stranded forms of RNA and DNA. Nucleic acids labeled with the OP-Cu and the Fe-EDTA protocols revealed high hybridization specificity in hybridization with DNA microchips containing oligonucleotide probes selected for identification of 16S rRNA sequences of the Bacillus group microorganisms.We also demonstrated cDNA- and cRNA-labeling and fragmentation with this method. Both the OP-Cu and Fe-EDTA fragmentation and labeling procedures are quick and inexpensive compared to other commonly used methods. A column-based version of the described method does not require centrifugation and therefore is promising for the automation of sample preparations in DNA microchip technology as well as in other nucleic acid hybridization studies.

Kelly, J. J.; Chernov, B. K.; Tovstanovsky, I.; Mirzabekov, A. D.; Bavykin, S. G.; Biochip Technology Center; Northwestern Univ.; Engelhardt Inst. of Molecular Biology

2002-12-15

254

Liquid Chromatographic Determination of NSC 737664 (ABT-888: an Inhibitor of Poly(ADP-ribose) Polymerase (PARP)) in Plasma and Urine in a Phase 0 Clinical Trial  

OpenAIRE

A gradient reversed-phase high performance liquid chromatographic method was developed for determining NSC 737664 (2-[(2R)-2-methylpyrrolidin-2-yl]-1H-benzimidazole-4-carboxamide; ABT-888) in human plasma and urine. Chromatographic separation used a mobile phase composed of 0.1% formic acid in water and 0.1% formic acid in acetonitrile, and a C18 column (150 mm × 4.6 mm, 5µ). Quantitation was performed using UV detection at 300 nm. Chromatographic peak identity was confirmed using positive-...

Phillips, Lawrence R.; Hill, Kimberly D.; Majerova, Eva

2009-01-01

255

Curative effect of Terminalia chebula extract on acetic acid-induced experimental colitis: role of antioxidants, free radicals and acute inflammatory marker.  

Science.gov (United States)

The present study has evaluated the healing effects of extract of dried fruit pulp of Terminalia chebula (TCE) on acetic acid (AA)-induced colitis in rats. TCE (600 mg/kg) showed healing effects against AA-induced colonic damage score and weight when administered orally daily for 14 days. TCE was further studied for its effects on various physical (mucus/blood in stool and stool frequency, food and water intake and body weight changes), histology, antibacterial activity and free radicals (NO and LPO), antioxidants (SOD, CAT and GSH) and myeloperoxidase in colonic tissue. Intra-colonic AA administration increased colonic mucosal damage and inflammation, mucus/bloody diarrhoea, stool frequency, but decreased body weight which were reversed by TCE and sulfasalazine (SS, positive control) treatments. TCE showed antibacterial activity and both TCE and SS enhanced the antioxidants, but decreased free radicals and myeloperoxidase activities affected in acetic acid-induced colitis. TCE indicated the presence of active principles with proven antioxidants, anti-inflammatory, immunomodulatory, and free radical scavenging and healing properties. Thus, TCE seemed to be safe and effective in healing experimental colitis. PMID:22956243

Gautam, M K; Goel, Shalini; Ghatule, R R; Singh, A; Nath, G; Goel, R K

2013-10-01

256

Antioxidant activity of phenolic acids and their metabolites: synthesis and antioxidant properties of the sulfate derivatives of ferulic and caffeic acids and of the acyl glucuronide of ferulic acid.  

Science.gov (United States)

The main metabolites of caffeic and ferulic acids (ferulic acid-4'-O-sulfate, caffeic acid-4'-O-sulfate, and caffeic acid-3'-O-sulfate), the most representative phenolic acids in fruits and vegetables, and the acyl glucuronide of ferulic acid were synthesized, purified, and tested for their antioxidant activity in comparison with those of their parent compounds and other related phenolics. Both the ferric reducing antioxidant power (FRAP) assay and the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging method were used. Ferulic acid-4'-O-sulfate and ferulic acid-4'-O-glucuronide exhibited very low antioxidant activity, while the monosulfate derivatives of caffeic acid were 4-fold less efficient as the antioxidant than caffeic acid. The acyl glucuronide of ferulic acid showed strong antioxidant action. The antioxidant activity of caffeic acid-3'-O-glucuronide and caffeic acid-4'-O-glucuronide was also studied. Our results demonstrate that some of the products of phenolic acid metabolism still retain strong antioxidant properties. Moreover, we first demonstrate the ex vivo synthesis of the acyl glucuronide of ferulic acid by mouse liver microsomes, in addition to the phenyl glucuronide. PMID:23157164

Piazzon, A; Vrhovsek, U; Masuero, D; Mattivi, F; Mandoj, F; Nardini, M

2012-12-19

257

Second-generation DBFOX ligands for the synthesis of beta-substituted alpha-amino acids via enantioselective radical conjugate additions.  

Science.gov (United States)

A set of second-generation DBFOX ligands possessing extended aryl or benzyl-type groups was synthesized. The requisite amino alcohols were either commercially available (DBFOX/Bn) or constructed via Sharpless asymmetric aminohydroxylation (DBFOX/Nap, DBFOX/ t-BuPh, DBFOX/Pip) or phase-transfer-catalyzed asymmetric alkylation (DBFOX/MeNap). Complexes of the ligands with Mg(NTf2)2 were evaluated as promoters of enantioselective radical conjugate additions to alpha,beta-unsaturated alpha-nitro amides and esters. Reactions employing the DBFOX/Nap ligand exhibited improved enantioselectivity relative to previously published additions mediated by DBFOX/Ph. However, the relatively modest increase in diastereomeric ratio suggests that our substrate-Lewis acid binding model, which was formulated based on results from DBFOX/Ph-promoted radical conjugate additions, is in need of revision. PMID:18947256

Banerjee, Biplab; Capps, Steven G; Kang, Junghoon; Robinson, Joshua W; Castle, Steven L

2008-11-21

258

In Vitro Activities of a New Ketolide, ABT-773, against Multidrug-Resistant Gram-Positive Cocci  

OpenAIRE

The in vitro activities of ABT-773 were evaluated against 324 strains of gram-positive bacteria, including multidrug-resistant Staphylococcus spp. and Enterococcus spp. ABT-773 had lower MIC ranges, MICs at which 50% of isolates are inhibited (MIC50s), and MIC90s than erythromycin or clindamycin for almost all isolates tested. The MICs of ABT-773 were also lower than those of quinupristin-dalfopristin (Q-D) for methicillin-susceptible Staphylococcus aureus, Rhodococcus spp., and Streptococcus...

Singh, Kavindra V.; Malathum, Kumthorn; Murray, Barbara E.

2001-01-01

259

Immobilization of caffeic acid on a polypropylene film: synthesis and antioxidant properties.  

Science.gov (United States)

The immobilization of caffeic acid (CA) on a polypropylene (PP) film was successfully performed through the covalent binding of the caffeoyl chloride on a modified polymeric surface of PP films grafted with hydroxyethyl methacrylate as monomer (PP-g-HEMA). The different reaction steps were monitored by FT-IR spectroscopy. The synthesized films were characterized by Folin-Ciocalteu method by measuring the available phenolic groups as caffeic acid equivalents linked to the surface. The antioxidant efficiency of the modified polymers was evaluated by typical spectrophometric methods, such as the bleaching of radicals DPPH(•) and ABTS(•+), and the inhibition of the enzymatically induced coupled oxidation of linoleic acid and betacarotene. The available phenolic groups on the modified film presented a good correlation with the antiradical activity toward DPPH(•). Moreover, the polymer synthesized in this work showed a good protective activity against ascorbic acid oxidation in real samples of orange juice. PMID:20666455

Arrua, Dario; Strumia, Miriam Cristina; Nazareno, Mónica Azucena

2010-08-25

260

Effect of metal ions on the reactions of the cumyloxyl radical with hydrogen atom donors. Fine control on hydrogen abstraction reactivity determined by Lewis acid-base interactions.  

Science.gov (United States)

A time-resolved kinetic study on the effect of metal ions (M(n+)) on hydrogen abstraction reactions from C-H donor substrates by the cumyloxyl radical (CumO(•)) was carried out in acetonitrile. Metal salt addition was observed to increase the CumO(•) ?-scission rate constant in the order Li(+) > Mg(2+) > Na(+). These effects were explained in terms of the stabilization of the ?-scission transition state determined by Lewis acid-base interactions between M(n+) and the radical. When hydrogen abstraction from 1,4-cyclohexadiene was studied in the presence of LiClO(4) and Mg(ClO(4))(2), a slight increase in rate constant (k(H)) was observed indicating that interaction between M(n+) and CumO(•) can also influence, although to a limited extent, the hydrogen abstraction reactivity of alkoxyl radicals. With Lewis basic C-H donors such as THF and tertiary amines, a decrease in k(H) with increasing Lewis acidity of M(n+) was observed (k(H)(MeCN) > k(H)(Li(+)) > k(H)(Mg(2+))). This behavior was explained in terms of the stronger Lewis acid-base interaction of M(n+) with the substrate as compared to the radical. This interaction reduces the degree of overlap between the ?-C-H ?* orbital and a heteroatom lone-pair, increasing the C-H BDE and destabilizing the carbon centered radical formed after abstraction. With tertiary amines, a >2-order of magnitude decrease in k(H) was measured after Mg(ClO(4))(2) addition up to a 1.5:1 amine/Mg(ClO(4))(2) ratio. At higher amine concentrations, very similar k(H) values were measured with and without Mg(ClO(4))(2). These results clearly show that with strong Lewis basic substrates variations in the nature and concentration of M(n+) can dramatically influence k(H), allowing for a fine control of the substrate hydrogen atom donor ability, thus providing a convenient method for C-H deactivation. The implications and generality of these findings are discussed. PMID:23215017

Salamone, Michela; Mangiacapra, Livia; DiLabio, Gino A; Bietti, Massimo

2013-01-01

261

Impact of Lactic Acid on Cell Proliferation and Free Radical Induced Cell Death in Monolayer Cultures of Neural Precursor Cells  

OpenAIRE

Biomaterials prepared from polyesters of lactic acid and glycolic acid, or a mixture of the two, degrade in the presence of water into the naturally occurring metabolites, lactic acid and glycolic acid. While the lactic acid degradation product that is released from biomaterials is well-tolerated by the body, lactic acid can influence the metabolic function of cells; it can serve as an energy substrate for cells, and has been shown to have antioxidant properties. Neural precursor cells, a cel...

Lampe, Kyle J.; Namba, Rachael M.; Silverman, Tyler R.; Bjugstad, Kimberly B.; Mahoney, Melissa J.

2009-01-01

262

In Vitro Antioxidant Activities, Free Radical Scavenging Capacity, and Tyrosinase Inhibitory of Flavonoid Compounds and Ferulic Acid from Spiranthes sinensis (Pers. Ames  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, ultrasound-assisted extraction (UAE and other methods of extracting flavonoid compounds and ferulic acid (FA from S. sinensis were investigated. Five different extraction methods, including water extraction (W, water extraction using UAE (W+U, 75% ethanol extraction (E, 75% ethanol extraction using UAE (E+U, and supercritical CO2 extraction (SFE were applied in the extraction of bioactive compounds (flavonoids and ferulic acid in order to compare their efficiency. The highest yield of flavonoids (4.28 mg/g and ferulic acid (4.13 mg/g content was detected in the E+U extract. Furthermore, S. sinensis extracts obtained by E+U show high antioxidant activity, and IC50 values of 0.47 mg/mL for DPPH radicals and 0.205 mg/mL for metal chelating activity. The total antioxidant assay shows superoxide radical scavenging capacity and in vitro mushroom tyrosinase inhibition in a dose-dependent manner, suggesting that E+U can be used for extraction of bioactive compounds from S. sinensis.

Chung Pin Liang

2014-04-01

263

In vitro antioxidant activities, free radical scavenging capacity, and tyrosinase inhibitory of flavonoid compounds and ferulic acid from Spiranthes sinensis (Pers.) Ames.  

Science.gov (United States)

In this study, ultrasound-assisted extraction (UAE) and other methods of extracting flavonoid compounds and ferulic acid (FA) from S. sinensis were investigated. Five different extraction methods, including water extraction (W), water extraction using UAE (W+U), 75% ethanol extraction (E), 75% ethanol extraction using UAE (E+U), and supercritical CO2 extraction (SFE) were applied in the extraction of bioactive compounds (flavonoids and ferulic acid) in order to compare their efficiency. The highest yield of flavonoids (4.28 mg/g) and ferulic acid (4.13 mg/g) content was detected in the E+U extract. Furthermore, S. sinensis extracts obtained by E+U show high antioxidant activity, and IC50 values of 0.47 mg/mL for DPPH radicals and 0.205 mg/mL for metal chelating activity. The total antioxidant assay shows superoxide radical scavenging capacity and in vitro mushroom tyrosinase inhibition in a dose-dependent manner, suggesting that E+U can be used for extraction of bioactive compounds from S. sinensis. PMID:24739930

Liang, Chung Pin; Chang, Chia Hao; Liang, Chien Cheng; Hung, Kuei Yu; Hsieh, Chang Wei

2014-01-01

264

Chlorogenic acid, an antioxidant principle from the aerial parts ofArtemisia iwayomogi that acts on 1,1-diphenyl-2-picrylhydrazyl radical.  

Science.gov (United States)

The antioxidant activity ofArtemisia iwayomogi was determined by measuring the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical The methanol extract ofA. iwayomogi showed strong antioxidant activity, and thus fractionated with several solvents. The antioxidant activity potential of the individual fraction was in the order of ethyl acetate>n-butanol>water>chloroform>n-hexane fraction. The ethyl acetate andn-butanol soluble fractions exhibiting strong antioxidant activity were further purified by repeated silica gel and Sephadex LH-20 column chromatography. Antioxidant chlorogenic acid was isolated as one of the active principles from then-butanol fraction, together with the inactive components, 1-octacosanol, scopoletin, scopolin, apigenin 7,4'-di-O-methylether luteolin 6,3'-di-O-methylether (jaceosidin), apigenin 7-methylether (genkwanin), 2,4-dihydroxy-6-methoxyacetophenone 4-O-beta-D-glucopyranoside and quebrachitol. The antioxidant activity of chlorogenic acid was comparable to that of L-ascorbic acid, which is a well known antioxidant. PMID:18975193

Kim, S S; Lee, C K; Kang, S S; Jung, H A; Choi, J S

1997-04-01

265

Cascade dissociations of peptide cation-radicals. Part 1. Scope and effects of amino acid residues in penta-, nona-, and decapeptides.  

Science.gov (United States)

Amino acid residue-specific backbone and side-chain dissociations of peptide z ions in MS(3) spectra were elucidated for over 40 pentapeptides with arginine C-terminated sequences of the AAXAR and AAHXR type, nonapeptides of the AAHAAXX"AR and AAHAXAX"AR type, and AAHAAXX"AAR decapeptides. Peptide z(n) ions containing amino acid residues with readily transferrable benzylic or tertiary ?-hydrogen atoms (Phe, Tyr, His, Trp, Val) underwent facile backbone cleavages to form dominant z(n-2) or z(n-3) ions. These backbone cleavages are thought to be triggered by a side-chain ?-hydrogen atom transfer to the z ion C(?) radical site followed by homolytic dissociation of the adjacent C(?)-CO bond, forming x(n-2) cation-radicals that spontaneously dissociate by loss of HNCO. Amino acid residues that do not have readily transferrable ?-hydrogen atoms (Gly, Ala) do not undergo the z(n) ? z(n-2) dissociations. The backbone cleavages compete with side-chain dissociations in z ions containing Asp and Asn residues. Side-chain dissociations are thought to be triggered by ?-hydrogen atom transfers that activate the C(?)-C(?) or C(?)-heteroatom bonds for dissociations that dominate the MS(3) spectra of z ions from peptides containing Leu, Cys, Lys, Met, Ser, Arg, Glu, and Gln residues. The Lys, Arg, Gln, and Glu residues also participate in ?-hydrogen atom transfers that trigger other side-chain dissociations. PMID:22669761

Chung, Thomas W; Hui, Renjie; Ledvina, Aaron; Coon, Joshua J; Ture?ek, Frantisek

2012-08-01

266

Antioxidant capacity and DNA-interaction studies of zinc complexes with a non-steroidal anti-inflammatory drug, mefenamic acid.  

Science.gov (United States)

Zinc(II) complexes of a non-steroidal anti-inflammatory drug, mefenamic acid(=Hmef) in the absence or presence of the nitrogen donor heterocyclic ligands 2,2'-bipyridine(=bipy), 2,2'-bipyridylamine(=bipyam), 2,2'-dipyridylketone oxime(=Hpko) or 1,10-phenanthroline(=phen) have been synthesized and characterized. The crystal structures of [Zn(mef-O,O')2(bipy)], 2, [Zn(mef-O)2(Hpko-N,N')2]·EtOH, 4 and [Zn(mef-O)(mef-O,O')(phen)(H2O)], 5, have been determined by X-ray crystallography showing distinct binding modes of mefenamato carboxylato group, bidentate in 2, monodentate in 4 or both in 5. Interaction studies of the complexes with calf-thymus DNA (CT DNA) have shown that complexes can bind to CT DNA with [Zn(mef-O)2(Hpko)2] exhibiting the highest binding constant to CT DNA (Kb = 1.93(±0.04) × 10(7) M(-1)). The complexes can bind to CT DNA via intercalation as concluded by DNA solution viscosity measurements. Competitive studies with ethidium bromide (EB) have shown that the complexes can displace the DNA-bound EB. The complexes exhibit good binding affinity to serum albumin proteins with [Zn(mef-O)2(H2O)4], 1 exhibiting the highest quenching ability (kq = 1.46 × 10(15) M(-1) s(-1) for human and 5.55 × 10(15) M(-1) s(-1) for bovine serum albumin). All compounds have been tested for their antioxidant and free radical scavenging activity as well as for their in vitro inhibitory activity against soybean lipoxygenase. The scavenging activity is low to moderate against 1,1-diphenyl-picrylhydrazyl (DPPH) radicals and high against hydroxyl and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(+·)) radicals, with [Zn(mef-O)2(H2O)4], 1 (ABTS%, 0.1 mM: 94.75(±1.06)%; (·)OH%, 0.1mM: 96.69(±0.27)%; LOX: IC50 = 27.34(±0.90) ?M) exhibiting the highest scavenging activity of the ABTS radical cation among the complexes. Additionally, the complexes exhibit higher scavenging and LOX inhibitory activity than free mefenamic acid (ABTS%, 0.1 mM: 66.32(±0.38)%; (·)OH%, 0.1 mM: 92.51(±0.44)%; LOX: IC50 = 48.52(±0.88) ?M). PMID:23948577

Tarushi, Alketa; Karaflou, Zoi; Kljun, Jakob; Turel, Iztok; Psomas, George; Papadopoulos, Athanasios N; Kessissoglou, Dimitris P

2013-11-01

267

Role of oxygen radicals and arachidonic acid metabolites in the reverse passive Arthus reaction and carrageenin paw oedema in the rat.  

OpenAIRE

1. The role of arachidonic acid metabolites and oxygen radicals in carrageenin-induced rat paw oedema and dermal reverse passive Arthus reaction (RPA) have been investigated. 2. Indomethacin (10 mg kg-1, p.o.) inhibited carrageenin paw oedema when administered 30 min before, but not 2 h after carrageenin. BWB70C (10 mg kg-1, p.o.), a selective inhibitor of 5-lipoxygenase, had no effect whether administered before or after carrageenin. Administration of both indomethacin and BWB70C had no grea...

Boughton-smith, N. K.; Deakin, A. M.; Follenfant, R. L.; Whittle, B. J.; Garland, L. G.

1993-01-01

268

Effect of a new synthetic ascorbic acid derivative as a free radical scavenger on the development of acute pancreatitis in mice.  

OpenAIRE

The therapeutic effects of CV 3611, a new synthetic free radical scavenger prepared from an ascorbic acid derivative, on choline deficient, ethionine enriched (CDE) diet induced acute pancreatitis in mice were evaluated and compared with those of superoxide dismutase. Time/course studies after subcutaneous injection of CV 3611 in normal mice showed a peak plasma concentration of mean (SEM) 0.54 (0.09) micrograms/ml at one hour, with a gradual decrease over the next 10 hours, while a peak conc...

Nonaka, A.; Manabe, T.; Tobe, T.

1991-01-01

269

Free radical damage to deoxyribose by anthracycline, aureolic acid and aminoquinone antitumour antibiotics. An essential requirement for iron, semiquinones and hydrogen peroxide.  

Science.gov (United States)

Anthracycline, aureolic acid and aminoquinone antitumour antibiotics damage deoxyribose in cell-free systems when reduced in air by the enzyme ferredoxin reductase. Damage to deoxyribose is inhibited by the iron chelator desferrioxamine, the copper-containing protein caeruloplasmin and catalase but not by superoxide dismutase. Scavengers of the hydroxyl radical such as formate, butan-1-ol, ethanol and benzoate do not offer much protection, whereas mannitol and thiourea do. These findings point to a site-specific Fenton reaction in which the drug semiquinones reduce complexed iron and dioxygen leading to the formation of hydrogen peroxide and a ferrous complex. PMID:2998399

Gutteridge, J M; Quinlan, G J

1985-12-01

270

Synthesis of steroidal quinones and hydroquinones from bile acids by Barton radical decarboxylation and benzoquinone addition. Studies on their cytotoxic and antifungal activities.  

Science.gov (United States)

Twelve new hydroquinones and quinones (4a-c to 7a-c) derived from free or peracetylated bile acids were prepared by a Barton decarboxylation reaction, with subsequent trapping of the resulting free radical by benzoquinone. All new compounds were completely characterized by 2D NMR techniques and screened for antifungal and cytotoxic activity. One of the new hydroquinones (7b) showed promising results against the human pancreatic ductal carcinoma cell line PANC1, with similar cytotoxic activity as the commercial chemotherapy drug doxorubicin. PMID:22001555

Siless, Gastón E; Knott, María E; Derita, Marcos G; Zacchino, Susana A; Puricelli, Lydia; Palermo, Jorge A

2012-01-01

271

OH-radical induced degradation of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and 4-chloro-2-methylphenoxyacetic acid (MCPA): A pulse radiolysis and gamma-radiolysis study  

International Nuclear Information System (INIS)

The reactions of ·OH, H· and eaq? with 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and 4-chloro-2-methylphenoxyacetic acid (MCPA) were studied by pulse radiolysis. The site of ·OH-radicals addition to the aromatic ring of 2,4,5-T was found to be—C1: ?18%, C2/C4/C5: total ?28% and C3/C6: total ?41%. The overall rate constants with OH-radicals were k(·OH+2,4,5-T)=6.4 (±0.5)×109 mol dm?3 s?1 and k(·OH+MCPA)=8.5 (±0.8)×109 mol dm?3 s?1. The radiation induced decomposition of the pesticides, chloride- and product formation (phenolic compounds, aliphatic acids) was studied by gamma radiolysis as a function of dose. A mechanism for acetate formation is discussed. The presence of oxygen during irradiation affected the decomposition rate only indiscernibly, however, chloride elimination, ring fragmentation (formation of aliphatic acids), TOC- and toxicity reduction were strongly enhanced. For complete removal of 500 ?mol dm?3 herbicides a dose of ?4 kGy was required. Using air saturation during irradiation a reduction of 37–40% of the TOC was observable at 5 kGy, detoxification (luminescence inhibition <20%) was achieved with 10 kGy. - Highlights: ? Degradation of phenoxyacetic acid herbicides by ionizing radiation. ? Primary pattern of OH-radical addition to the aromatic ring of 2,4,5-T.5-T. ? Strong influence of oxygen concentration on chloride elimination, formation of phenolic intermediates and aliphatic acids. ? Detoxification of 500 ?mol herbicide solutions is obtained with 10 kGy.

272

In Vitro and In Vivo Enhancement of Chemoradiation Using the Oral PARP Inhibitor ABT-888 in Colorectal Cancer Cells  

International Nuclear Information System (INIS)

Purpose: Poly(ADP-ribose) polymerase plays a critical role in the recognition and repair of DNA single-strand breaks and double-strand breaks (DSBs). ABT-888 is an orally available inhibitor of this enzyme. This study seeks to evaluate the use of ABT-888 combined with chemotherapy and radiation therapy (RT) in colorectal carcinoma models. Methods and Materials: RT clonogenic assays were performed on HCT116 and HT29 cells treated with 5-fluorouracil, irinotecan, or oxaliplatin with or without ABT. The surviving fraction at 2 Gy and dose-modifying factor at 10% survival were analyzed. Synergism was assessed by isobologram analysis for combination therapies. ?H2AX and neutral comet assays were performed to assess the effect of therapy on DSB formation/repair. In vivo assessments were made by use of HCT116 cells in a xenograft mouse model. Tumor growth delay was measured at a volume of 500 mm3. Results: Both lines were radiosensitized by ABT alone, and ABT further increased chemotherapy dose-modifying factors to the 1.6 to 1.8 range. All combinations were synergistic (combination indices <0.9). ABT treatment significantly increased DSB after RT (?H2AX, 69% vs 43%; P=.017) and delayed repair. We found tumor growth delays of 7.22 days for RT; 11.90 days for RT and ABT; 13.5 days for oxaliplatin, RT, and ABT; 14.17 days for 5-fluorouracil, RT, and ABT; and 23.81 days for irinotecan, RT, and ABT. Conclusion: ABT-888 radiosensitizes at similar or higher levels compared with classic chemotherapies and acts synergistically with these chemotherapies to enhance RT effects. In vivo confirmation of these results indicates a potential role for combining its use with existing chemoradiation regimens

273

Dosimetric Applications of Electronic Paramagnetic Resonance Measurements of Free Radicals Formed in Amino Acids: Construction of a Tissue-Equivalent Dosimeter Based on Alanine  

International Nuclear Information System (INIS)

In the case of amino acids rupture of the molecules due to the action of radiation is found to produce free radicals. The number of these radicals can be measured by means of an electronic paramagnetic resonance spectrometer and this number is proportional to the dose absorbed. Alanine has been used for this purpose since it possesses this property over a wide dose range (from 10 to 5 x 106 rads). The present paper covers essentially the following points: (a) Pre-irradiation effect in non-irradiated alanine: this dose limits the minimum measurable dose to approximately 10 rads. The origin of this dose and means of re- ducing it have been studied; (b) Energy response of the alanine: by virtue of the close similarity of its composition to that of tissue, this dosimeter has a good energy response for gamma radiations; the loss of efficiency at low energies can be corrected by the addition of a higher Z material (Ba or Ca); (c) Response to neutrons: with neutrons the radical yield is lower than in the case of gamma radiation, although this yield can be increased by adding a hydrogenated substance (paraffin); (d) Construction of a dosimeter in pellet form: the addition of paraffin improves the response to neutrons and enables moulded pellets of the mixture to be produced. These are easier to use than alanine in powder form and the dosimeters can be produced in any desired form. (author)

274

Radical scavenging activities of niacin-related compounds.  

Science.gov (United States)

We investigated whether niacin-related compounds had radical-scavenging activity by electron spin resonance methods. Many compounds, but not trigonelline, had radical-scavenging activity against hydroxyl radicals. However, for the nitric oxide radical and 1,1-diphenyl-2-picrylhydrazyl radical, only nicotinic acid hydrazide and isonicotinic acid hydrazide had scavenging activities. These results suggest that the moiety of hydrazide might have an important role in scavenging abilities of various radicals. PMID:12005062

Ogata, Shin; Takeuchi, Masayo; Teradaira, Shin; Yamamoto, Naokuni; Iwata, Keiko; Okumura, Katsuzumi; Taguchi, Hiroshi

2002-03-01

275

Studies on the syntheses, structural characterization, antimicrobial-, and DPPH radical scavenging activity of the cocrystals caffeine:cinnamic acid and caffeine:eosin dihydrate  

Science.gov (United States)

Two organic cocrystals namely, caffeine:cinnamic acid [(caf)(ca)] (1) and caffeine:eosin dihydrate [(caf)(eos)]·2H2O (2) were synthesized and studied by FT-IR, TGA/DTA, and single crystal XRD. The crystal system of cocrystal 1 is triclinic with space group P-1 and Z = 2 and that of cocrystal 2 is monoclinic with space group P21/C and Z = 4. An imidazole-carboxylic acid synthon is observed in the cocrystal 1. The intermolecular hydrogen bond, O-H⋯N and ?-? interactions play a major role in stabilizing 1 whereas the intermolecular hydrogen bonds, O-H⋯O, O-H⋯N, and intramolecular hydrogen bond, O-H⋯Br; along with ?-? interactions together play a vital role in stabilizing the structure of 2. The antimicrobial- and DPPH radical scavenging activities of both the cocrystals were studied.

Suresh Kumar, G. S.; Seethalakshmi, P. G.; Bhuvanesh, N.; Kumaresan, S.

2013-10-01

276

Estudio comparativo sobre la capacidad de atrapamiento del catiónradical ABTS+. Por los aceites esenciales de especies aromáticas con alto contenido de trans-ANETOL Y ESTRAGOL  

Directory of Open Access Journals (Sweden)

Full Text Available Se determinó la composición química de aceites esenciales (AEs y extractos de seis especies aromáticas con alto contenido de trans-anetol y estragol (estragón de invierno, estragón, anís estrellado, anisillo, hinojo y sígueme morado, obtenidos por hidrodestilación asistida por radiación de microondas (MWHD y destilación-extracción simultánea con solvente (SDE. La separación e identificación de los compuestos se realizó por GC-MS en columna apolar DB-5MS, comparando sus espectros de masas con los de las bases de datos ADAMS, NIST02 y Wiley138 e índices de retención de kovàts. Para todos los AEs se evaluó su capacidad del atrapamiento del catión-radical ABTS+. (ácido 2,2? -azino-bis -(3-etiltiazolina-bencenosulfónico-6.

Amner Mu\\u00F1oz

2007-01-01

277

Enzyme inhibitory and radical scavenging effects of some antidiabetic plants of Turkey  

Science.gov (United States)

Objective(s): Ethnopharmacological field surveys demonstrated that many plants, such as Gentiana olivieri, Helichrysum graveolens, Helichrysum plicatum ssp. plicatum, Juniperus oxycedrus ssp. oxycedrus, Juniperus communis var. saxatilis, Viscum album (ssp. album, ssp. austriacum), are used as traditional medicine for diabetes in different regions of Anatolia. The present study was designed to evaluate the in vitro antidiabetic effects of some selected plants, tested in animal models recently. Materials and Methods: ?-glucosidase and ?-amylase enzyme inhibitory effects of the plant extracts were investigated and Acarbose was used as a reference drug. Additionally, radical scavenging capacities were determined using 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) ABTS radical cation scavenging assay and total phenolic content of the extracts were evaluated using Folin Ciocalteu method. Results: H. graveolens ethanol extract exhibited the highest inhibitory activity (55.7 % ± 2.2) on ?-amylase enzyme. Additionally, J. oxycedrus hydro-alcoholic leaf extract had potent ?-amylase inhibitory effect, while the hydro-alcoholic extract of J. communis fruit showed the highest ?-glucosidase inhibitory activity (IC50: 4.4 ?g/ml). Conclusion: Results indicated that, antidiabetic effect of hydro-alcoholic extracts of H. graveolens capitulums, J. communis fruit and J. oxycedrus leaf might arise from inhibition of digestive enzymes. PMID:25140204

Orhan, Nilüfer; Hoçbaç, Sanem; Orhan, Didem Deliorman; Asian, Mustafa; Ergun, Fatma

2014-01-01

278

ABT-737, Synergistically Enhances Daunorubicin-Mediated Apoptosis in Acute Myeloid Leukemia Cell Lines  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: Intensive chemotherapy with daunorubicin (DNR is associated with serious side effects in acute myeloid leukemia (AML patients. In this study the effect of small-molecule BH3-mimetic, ABT-737, on the sensitivity of HL60 and U937 AML cell lines was investigated. Methods: The cytotoxic effects of DNR and ABT-737, alone or in combination were assessed using MTT assay and combination index analysis. The effects of treatments on the cell proliferation was determined by trypan blue assay. ELISA cell death assay was used for measurement of apoptosis. Results: IC50 values of DNR and ABT-737 were 2.52 and 0.59 ?M for HL-60 cells line and 1.31 and 0.80 ?M for U937 cell line at 24 h, respectively. Surprisingly, combination treatment significantly lowered the IC50 values in a synergic manner in both cell lines. Moreover, treatment with a mixture of two agents had more growth inhibition effect relative to the monotherapy. Results of apoptosis assay showed that the cytotoxic effects are related to the enhancement of apoptosis. Conclusion: Our study suggests that ABT-737 synergistically enhances the cytotoxic effect of DNR in AML cell lines and therefore may be useful to overcome chemoresistance of leukemia patients.

Hassan Dariushnejad

2014-03-01

279

Fluorinated amphiphilic amino acid derivatives as antioxidant carriers: a new class of protective agents.  

Science.gov (United States)

The use of classical antioxidants is limited by their low bioavailabilities, and therefore, high doses are usually required to display significant protective activity. In a recent article (J. Med. Chem. 2003, 46, 5230) we showed that the ability of the alpha-phenyl-N-tert-butylnitrone (PBN) to restore the viability of ATPase-deficient human skin fibroblasts was greatly enhanced by grafting it on a fluorinated amphiphilic carrier. With the aim of extending this concept to other antioxidants, we present here the design, the synthesis, and the physicochemical measurements of a new series of fluorinated amphiphilic antioxidant derivatives. The hydroxyl radical scavenging activity and the radical reducing potency of these newly designed compounds were respectively demonstrated in an ABTS competition and an ABTS(*+) reduction assay. We also showed that the protective effects of amphiphilic antioxidants derived from PBN, Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid) or lipoic acid (5-[1,2]-dithiolan-3-ylpentanoic acid) in primary cortical mixed cell cultures exposed to oxidotoxins are greatly improved compared to their parent compounds in the following rank-order: (1) PBN, (2) Trolox, and (3) lipoic acid. In contrast, the protective activity of indole-3-propionic acid was slightly decreased by grafting it on the amphiphilic carrier. Similar observations were made in in vivo experiments using aquatic invertebrate microorganisms, called rotifers, which were exposed to lethal concentrations of nonselective (H(2)O(2)) and mitochondria-selective (doxorubicin) oxidotoxins. The conclusion of these studies is that fluorinated amphiphilic PBN, Trolox, and lipoic acid derivatives exhibit very potent protective activities in in vitro and in vivo experiments. The findings demonstrated herein therefore strongly suggest that the amphiphilic character enhances the bioavailability of the antioxidants and allows for a selective targeting of mitochondria. PMID:16640342

Ortial, Stéphanie; Durand, Grégory; Poeggeler, Burkhard; Polidori, Ange; Pappolla, Miguel A; Böker, Jutta; Hardeland, Rüdiger; Pucci, Bernard

2006-05-01

280

Free Radical Scavenging and Antibacterial Activity of Crude Extracts from Selected Plants of Medicinal Value Used in Zululand  

Directory of Open Access Journals (Sweden)

Full Text Available Ledebouria revoluta, Berkheya setifera and Carissa bispinosa are some of the medicinal plants used in South African traditional medicine. An investigation to evaluate antimicrobial, anti-inflammatory and free radical scavenging activities of the root crude extracts and fractions from the three plants was carried out. Reduction by 2, 2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS.+ and 2, 2-di (4-tert-octylphenyl-1-picrylhydrazyl (DPPH. radicals were used to assess antioxidant capacities by change in absorbance in a UV-VIS spectrophotometer. Anti-inflammatory activity of the plant extracts against 15-soybean derived lipoxygenase (15-LOX enzyme was evaluated as increase in absorbance at 234 nm after addition of soya bean derived 15-LOX, using linoleic acid (134 µM as substrate. Anti-microbial activities were determined by assessing the plant samples’Minimum Inhibitory Concentrations (MICs by a micro dilution method. Carissa bispinosa and Berkheya setifera have shown good to moderate antimicrobial activity. Ledebouria revoluta displayed good activities (20 µg/mL for both acetone and methanol fractions against E. coli and good-moderate activity (160-320 µg/mL against the rest of the bacterial strains used. Anti-fungal activity for Ledebouria revoluta methanol fraction (20 µg/mL is high against Candida albicans. Percentage inhibition of 15-soybean lipoxygenase enzyme by the crude extracts at concentration of 25 µg/mL was for Berkheya setifera, 80%, Carissa bispinosa, 65% and Ledebouria revoluta, 40%.

E. Muleya

2014-01-01

281

Identification and quantification of phytochemical composition and anti-inflammatory and radical scavenging properties of methanolic extracts of Chinese propolis.  

Science.gov (United States)

Fifteen propolis samples collected from different regions of China were investigated and compared for their phytochemical composition and anti-inflammatory and radical scavenging properties. Eleven compounds including caffeic, p-coumaric, ferulic, isoferulic, and 3,4-dimethylcaffeic acids, pinobanksin, chrysin, pinocembrin, galangin, pinobanksin 3-acetate, and caffeic acid phenylethyl ester were quantified for the 15 propolis samples using a UHPLC method, whereas 38 compounds were identified by UPLC/Q-TOF-MS. The 15 propolis samples significantly differed in their total phenolic and total flavonoid contents, as well as their phytochemical profiles. The methanol extracts of propolis also showed significant anti-inflammatory effects in LPS-stimulated RAW 264.7 mouse macrophage cells at 10 ?g propolis extract/mL concentration. Additionally, the propolis samples differed in their DPPH, ABTS cation, hydroxyl, and peroxide radical scavenging capacities and ferric reducing abilities. The results from this study may be used to improve the commercial production and consumption of Chinese propolis products. PMID:23176258

Shi, Haiming; Yang, Haisha; Zhang, Xiaowei; Yu, Liangli Lucy

2012-12-19

282

Phospholipid Furan Fatty Acids and Ubiquinone-8: Lipid Biomarkers That May Protect Dehalococcoides Strains from Free Radicals  

OpenAIRE

Dehalococcoides species have a highly restricted lifestyle and are only known to derive energy from reductive dehalogenation reactions. The lipid fraction of two Dehalococcoides isolates, strains BAV1 and FL2, and a tetrachloroethene-to-ethene-dechlorinating Dehalococcoides-containing consortium were analyzed for neutral lipids and phospholipid fatty acids. Unusual phospholipid modifications, including the replacement of unsaturated fatty acids with furan fatty acids, were detected in both De...

White, David C.; Geyer, Roland; Peacock, Aaron D.; Hedrick, David B.; Koenigsberg, Stephen S.; Sung, Youlboong; He, Jianzhong; Lo?ffler, Frank E.

2005-01-01

283

ESR single-crystal study of OH radicals in X-irradiated salts of tartaric acid at 26 K  

International Nuclear Information System (INIS)

OH radicals originating from water of crystallization have been identified in X-irradiated single crystals of NaK-tartrate tetrahydrate and K2-tartrate hemihydrate. The principal values of the g tensor are (1.9918, 2.0057, 2.1047) and (1.9915, 2.0131, 2.1299), and of the hyperfine tensors (-23.4, -43.1, 8.3) G and (-29.2, -40.8, 4.8) G, for NaK- and K2-tartrate Relative signs of elements of the hyperfine tensors were determined. (orig.)

284

ESR single-crystal study of OH radicals in X-irradiated salts of tartaric acid at 26 K  

Energy Technology Data Exchange (ETDEWEB)

OH radicals originating from water of crystallization have been identified in X-irradiated single crystals of NaK-tartrate tetrahydrate and K/sub 2/-tartrate hemihydrate. The principal values of the g tensor are (1.9918, 2.0057, 2.1047) and (1.9915, 2.0131, 2.1299), and of the hyperfine tensors (-23.4, -43.1, 8.3) G and (-29.2, -40.8, 4.8) G, for NaK- and K/sub 2/-tartrate Relative signs of elements of the hyperfine tensors were determined.

Samskog, P.O.; Lund, A. (Naturvetenskapliga Forskningslab., Studsvik (Sweden))

1982-03-05

285

ESR single-crystal study of oh radicals in X-irradiated salts of tartaric acid at 26 K  

Science.gov (United States)

OH radicals originating from water of crystallization have been identifed in X-irradiated single crystals of NaK-tartrate tetrahydrate and K 2-tartrate hemihydrate. The principal values of the g tensor are (1.9918.2.0057.2.1047) and (1.9915. 2.0131, 2.1299), and of the hyperfine tensors (-23.4, -43.1, 8.3) G and (-29.2, -40.8.4.8) G, for NaK- and K 2-tartrate Relative signs of elements of the hyperfine tensors were determined.

Samskog, P.-O.; Lund, A.

1982-03-01

286

Effect of methyl mercury induced free radical stress on nucleic acids and protein: Implications on cognitive and motor functions  

OpenAIRE

Mercury pollution and acute neurotoxicity of mercury is well known. The recent reports suggest the adverse effect of low dose mercury, though the available literature is still silent on its mechanism. This study was therefore undertaken to probe the effect of low dose methyl mercury induced heavy metal toxicity on free radical stress and its impact on behaviour of male albino rats. Male albino rats were exposed to 1 mg/kg body wt of methylmercury chloride for seven days, on day 8 they were te...

Zahir, Farhana; Rizvi, Shameem J.; Haq, Soghra K.; Khan, Rizwan H.

2006-01-01

287

Radical frustrated Lewis pairs.  

Science.gov (United States)

While a growing body of literature describes FLP adducts of diamagnetic unsaturated substrates such as alkenes, alkynes and heterocumulenes such as carbon dioxide, capture of the diatomic radical nitric oxide (NO) by intramolecular phosphane/borane FLPs gives a new family of radical frustrated Lewis pair adducts. Capture of NO results in heterocycles with new P-N and B-N bonds featuring a spin density Umpolung of NO to give FLP-NO species that possess significant O-centered radical reactivity. Use of these radical FLP-NO species in C-H functionalization chemistry via H-atom abstraction / radical recombination sequences as well as deployment in nitroxide mediated polymerization of alkenes indicates a rich and diverse chemistry for FLP-NO species. An alternative, complementary strategy to generate radical FLPs involves the use of transition metal centers with unpaired electrons as the Lewis acid component of an FLP in conjunction with a tethered but hindered Lewis base. PMID:23468284

Warren, Timothy H; Erker, Gerhard

2013-01-01

288

Evaluation of in vitro antioxidant activity and free radical scavenging potential of variety of Tagetes erecta L. flowers growing in Bulgaria  

Directory of Open Access Journals (Sweden)

Full Text Available Summary. Marigold (Tagetes erecta L. is well known for its antimicrobial, antiseptic, wound and ulcer healing, antiinflammatory, antioxidant and antiviral properties, and it has a long history of being used as an herbal remedy. T. erecta L. produces a variety of substances that possess pharmacological effects and antioxidant activity. The present study was therefore aimed to analyze the antioxidant activity of extracts and fractions of T. erecta L. flowers, cultivated in Bulgaria. Radical scavenging potential was determined using two different in vitro assays. 1, 1-diphenyl-2-picrylhydrazyl (DPPH and 2, 2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS radicals. The ethyl acetate fraction of T. erecta L. ethanol extract was found to be the most effective in both assays, DPPH (IC50 4.3±0.4 ?g/ml and ABTS (0.8±0.2 TEAC. The greatest total phenolic content was detected in EtOAc fraction from EtOH extract (517.8 mg/g GAE. It was obtained high quantity of ascorbate and ascorbate/dehydroascorbate ratio more than 1. The quantity of glutathione reduced is low and glutathione reduced/glutathione oxidized ratio was lower than 1. A correlation between radical scavenging capacities of samples with total phenolic compound content was observed. The present study revealed that the EtOAc fraction effectively show the best ability to scavenge the free radicals. Industrial relevance. Herbal medicines have gained increasing attention worldwide for the treatment of chronic diseases because of their effectiveness and small side effects as compared to synthetic drugs.Recently, an attention has been directed toward the antioxidant phytochemicals which have proved as protective against cardiovascular diseases and cancer, associated with overproduction of reactive oxygen species. The present investigations focus has been to discover plant extracts and fractions from T. erecta useful to prevent chronic degenerative diseases, especially those mediated by free radicals damages. The great antioxidant activity indicates the potential of the extracts as a source of natural antioxidants or nutraceuticals with possible application to reduce oxidative stress with consequent health benefits. Keywords. Tagetes erecta L.; in vitro antioxidant activity; free radical scavenging potential; phenols; flavonoids; ascorbate, glutathione.

Yuliana Markovska

2012-08-01

289

Comparative In Vitro Susceptibilities and Bactericidal Activities of Investigational Fluoroquinolone ABT-492 and Other Antimicrobial Agents against Human Mycoplasmas and Ureaplasmas  

OpenAIRE

We determined in vitro susceptibilities for ABT-492 and other antimicrobials against Mycoplasma pneumoniae, Mycoplasma fermentans, Mycoplasma hominis, and Ureaplasma species. ABT-492 MICs were ?1 ?g/ml, and the agent was bactericidal against selected isolates of M. pneumoniae and M. hominis. ABT-492 has potential for treatment of infections due to these microorganisms.

Waites, Ken B.; Crabb, Donna M.; Duffy, Lynn B.

2003-01-01

290

Understanding sensitivity to BH3 mimetics: ABT-737 as a case study to foresee the complexities of personalized medicine  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract BH3 mimetics such as ABT-737 and navitoclax bind to the BCL-2 family of proteins and induce apoptosis through the intrinsic apoptosis pathway. There is considerable variability in the sensitivity of different cells to these drugs. Understanding the molecular basis of this variability will help to determine which patients will benefit from these drugs. Furthermore, this understanding aids in the design of rational strategies to increase the sensitivity of cells which are otherwise resistant to BH3 mimetics. We discuss how the expression of BCL-2 family proteins regulates the sensitivity to ABT-737. One of these, MCL-1, has been widely described as contributing to resistance to ABT-737 which might suggest a poor response in patients with cancers that express levels of MCL-1. In some cases, resistance to ABT-737 conferred by MCL-1 is overcome by the expression of pro-apoptotic proteins that bind to apoptosis inhibitors such as MCL-1. However, the distribution of the pro-apoptotic proteins amongst the various apoptosis inhibitors also influences sensitivity to ABT-737. Furthermore, the expression of both pro- and anti-apoptotic proteins can change dynamically in response to exposure to ABT-737. Thus, there is significant complexity associated with predicting response to ABT-737. This provides a paradigm for the multiplicity of intricate factors that determine drug sensitivity which must be considered for the full implementation of personalized medicine.

Stamelos Vasileios A

2012-08-01

291

Radical Evil  

OpenAIRE

There is an aporia in Kant’s analysis of evil: he defines radical evilas an invisible disposition of the will, but he also demands an inferential connection between visible evil actions and this invisible disposition. This inference,however, undermines the radical invisibility of radical evil according to Kant’s own definition of the latter. Noting how this invisibility of moral worth is a distinctive feature of Kant’s approach to the moral problem, the paper then asks why, in the Groun...

Carlos Manrique.

2007-01-01

292

A peripherally acting, selective T-type calcium channel blocker, ABT-639, effectively reduces nociceptive and neuropathic pain in rats.  

Science.gov (United States)

Activation of T-type Ca²? channels contributes to nociceptive signaling by facilitating action potential bursting and modulation of membrane potentials during periods of neuronal hyperexcitability. The role of T-type Ca²? channels in chronic pain is supported by gene knockdown studies showing that decreased Ca(v)3.2 channel expression results in the loss of low voltage-activated (LVA) currents in dorsal root ganglion (DRG) neurons and attenuation of neuropathic pain in the chronic constriction injury (CCI) model. ABT-639 is a novel, peripherally acting, selective T-type Ca²? channel blocker. ABT-639 blocks recombinant human T-type (Ca(v)3.2) Ca²? channels in a voltage-dependent fashion (IC?? = 2 ?M) and attenuates LVA currents in rat DRG neurons (IC?? = 8 ?M). ABT-639 was significantly less active at other Ca²? channels (e.g. Ca(v)1.2 and Ca(v)2.2) (IC?? > 30 ?M). ABT-639 has high oral bioavailability (%F = 73), low protein binding (88.9%) and a low brain:plasma ratio (0.05:1) in rodents. Following oral administration ABT-639 produced dose-dependent antinociception in a rat model of knee joint pain (ED?? = 2 mg/kg, p.o.). ABT-639 (10-100 mg/kg, p.o.) also increased tactile allodynia thresholds in multiple models of neuropathic pain (e.g. spinal nerve ligation, CCI, and vincristine-induced, and capsaicin secondary hypersensitivity). ABT-639 did not attenuate hyperalgesia in inflammatory pain models induced by complete Freund's adjuvant or carrageenan. At higher doses (e.g. 100-300 mg/kg) ABT-639 did not significantly alter hemodynamic or psychomotor function. The antinociceptive profile of ABT-639 provides novel insights into the role of peripheral T-type (Ca(v)3.2) channels in chronic pain states. PMID:24726441

Jarvis, Michael F; Scott, Victoria E; McGaraughty, Steve; Chu, Katharine L; Xu, Jun; Niforatos, Wende; Milicic, Ivan; Joshi, Shailen; Zhang, Qingwei; Xia, Zhiren

2014-06-15

293

Impact of nitrous acid photolysis on the total hydroxyl radical budget during the Limitation of Oxidant Production/Pianura Padana Produzione di Ozono study in Milan  

Science.gov (United States)

The photolysis of nitrous acid (HONO) in the early morning hours is believed to be a significant source of hydroxyl radicals (OH), the most important daytime oxidizing species. Although the importance of this mechanism has been recognized for many years, no accurate experimental quantification is available. Here we present measurements of HONO, NO2, SO2, O3 and HCHO by Differential Optical Absorption Spectroscopy (DOAS) during the Limitation of Oxidant Production/Pianura Padana Produzione di Ozono (LOOP/PIPAPO) study in May-June 1998 in Milan, Italy. The concentration of NO and J(NO2)/J(HONO) were simultaneously monitored by in situ monitors. The photolysis frequencies of HCHO and O3 were determined with a radiative transfer model. High nocturnal HONO mixing ratios of up to 4.4 ppb were regularly observed. Elevated daytime HONO levels during cloudy periods show that the formation of HONO proceeds after sunrise and therefore also represents a source of hydroxyl radicals throughout the day. Averaged over 24 hours, HCHO photolysis is the most important source of OH in Milan, followed by either ozone or HONO photolysis. Our observations indicate that on certain days the OH production from HONO can be even more important than that from ozone photolysis. The diurnal variation of the different OH formation mechanisms shows that HONO photolysis is by far the most important source in the early hours of the morning, and can be as large as and even surpass the total OH production at noon.

Alicke, B.; Platt, U.; Stutz, J.

2002-11-01

294

Reaction of sulphate radical anion (SO{sub 4}{sup {center_dot}}{sup -}) with cyanuric acid. A potential reaction for its degradation?  

Energy Technology Data Exchange (ETDEWEB)

A novel reaction between sulfate radical anion (SO{sub 4}{sup {center_dot}}{sup -}) and cyanuric acid (CA), a non-degradable end product of the oxidative degradation of the triazine based herbicide, atrazine, is presented using laser flash photolysis and steady state radiolysis techniques at pH 5. A second order rate constant of 1.9x10{sup 7} dm{sup 3} mol{sup -1} s{sup -1} has been determined and the transient intermediate ({lambda}{sub max}=330 nm) is assigned to a radical cation of CA (CA{sup {center_dot}}{sup +}). The degradation profile indicated that about 76% of CA have been decomposed after an absorbed {gamma}-radiation dose of 18 kGy. It is therefore proposed that the reaction of SO{sub 4}{sup {center_dot}}{sup -} could be utilised for the degradation of CA in aqueous medium which is normally stable to any Advanced Oxidation Processes. (author)

Manoj, P.; Varghese, R.; Manoj, V.M.; Aravindakumar, C.T. [Mahatma Gandhi University, School of Chemical Sciences, Kottayam (India)

2002-01-01

295

Peripheral and central nervous system inhibition of 11?-hydroxysteroid dehydrogenase type 1 in man by the novel inhibitor ABT-384  

OpenAIRE

ABT-384 is a potent, selective inhibitor of 11-beta-hydroxysteroid dehydrogenase type 1 (HSD-1). One milligram of ABT-384 daily fully inhibited hepatic HSD-1. Establishing the dose that fully inhibits central nervous system (CNS) HSD-1 would enable definitive clinical studies in potential CNS indications. [9,11,12,12-2H4] cortisol (D4 cortisol), a stable labeled tracer, was used to characterize HSD-1 inhibition by ABT-384. D4 cortisol and its products were measured in the plasma and cerebrosp...

Katz, D. A.; Liu, W.; Locke, C.; Jacobson, P.; Barnes, D. M.; Basu, R.; An, G.; Rieser, M. J.; Daszkowski, D.; Groves, F.; Heneghan, G.; Shah, A.; Gevorkyan, H.; Jhee, S. S.; Ereshefsky, L.

2013-01-01

296

A Novel Alkali Extractable Polysaccharide from Plantago asiatic L. Seeds and Its Radical-Scavenging and Bile Acid-Binding Activities.  

Science.gov (United States)

A new acidic polysaccharide (PLP) was isolated and characterized from Plantago asiatic L. seeds by hot alkali extraction and chromatographic purification using DEAE cellulose and Sephacryl S-400 columns. PLP has a molecular weight of 1.15 × 10(6) Da, and a monosaccharide composition of xylose (Xyl), arabinose (Ara), glucuronic acid (GlcA), and galactose (Gal) in a molar ratio of 18.8:7.2:6.1:1. The results of methylation analysis, FT-IR, and 1D and 2D NMR indicated that PLP was a highly branched heteroxylan of ?-1,4-linked Xylp backbone with three ?-GlcAp-(1?3)-Araf attached to the O-3 position and one ?-T-linked-GlcAp and one ?-Araf-(1?5)-Araf attached to the O-2 position every eight monosaccharide residues. PLP exhibited scavenging abilities against hydroxyl, peroxyl anion, and DPPH radicals in vitro and showed significant binding capacities against cholic and chenodeoxycholic acids, suggesting its possible cholesterol-lowering activity. The results demonstrated the potential use of PLP in functional foods and nutraceuticals. PMID:25536026

Gong, Lu; Zhang, Hua; Niu, Yuge; Chen, Lei; Liu, Jie; Alaxi, Sierkemideke; Shang, Pingping; Yu, Wenjuan; Yu, Liangli Lucy

2015-01-21

297

Antigenotoxic and free radical scavenging activities of extracts from Moricandia arvensis.  

Science.gov (United States)

This study evaluates genotoxic and antigenotoxic effects of extracts from leaves of Moricandia arvensis, which are used in traditional cooking and medicines. Extracts showed no genotoxicity when tested with the SOS Chromotest using E. coli PQ37 and PQ35 strains, except for the total oligomers flavonoids enriched extract. Petroleum ether and methanol extracts are the most active in reducing nitrofurantoin genotoxicity, whereas methanol and total oligomers flavonoids enriched extracts showed the most important inhibitory effect of H2O2 genotoxicity. In addition, these two extracts showed important free radical scavenging activity toward the DPPH. radical, whereas the chloroform extract exhibited the highest value of TEAC against ABTS+. radical. PMID:17934925

Skandrani, I; Sghaier, M Ben; Neffati, A; Boubaker, J; Bouhlel, I; Kilani, S; Mahmoud, A; Ghedira, K; Chekir-Ghedira, L

2007-01-01

298

Free-Radical Scavenging Properties and Reducing Power of Grape Cane Extracts from 11 Selected Grape Cultivars Widely Grown in China  

Directory of Open Access Journals (Sweden)

Full Text Available Total phenolic contents (TPC, total flavonoid contents (TFC, related antioxidative and antiradical capabilities of grape cane extracts from 11 varieties (five V. vinifera cultivars and six Chinese wild grapes widely grown in China were evaluated. Antioxidant properties were determined as DPPH and ABTS radical-scavenging abilities, superoxide anion and hydroxyl radical and hydrogen peroxide scavenging assays, as well as reducing power. Phenolic profiles of the extracts were characterized by using high-performance liquid chromatography (HPLC techniques. All extracts exhibited strong antioxidant and effective free radical inhibition activities (EC50 values, which generally correlated negatively with TPC (r = ?0.804 to ?0.918 and TFC (r = ?0.749 to ?0.888. In comparison with gallic acid, Trolox and tert-butylhydroquinone (positive controls, most grape cane extracts showed more efficient scavenging effects toward different reactive oxygen species. HPLC analysis revealed the presence of (+-catechin, (?-epicatechin, and trans-resveratrol as major phenolic components in the extracts. These results suggest that grape cane extracts may serve as a potential source of natural antioxidant for food and pharmaceutical application.

Ang Zhang

2011-12-01

299

Ethanol-induced changes in hepatic free radical defense mechanisms and fatty-acid composition in the miniature pig.  

Science.gov (United States)

In the miniature pig, ethanol consumption has been reported to induce alterations in hepatic antioxidant defense capacity, which could result in increased risk of peroxidative damage. However, ethanol may also induce changes in membrane fatty acid composition, which could reduce the risk of peroxidative damage. This study examined lipid peroxidation, antioxidant defense and fatty acid composition in livers from miniature pigs fed ethanol in diets containing 12% of their calories as fat for 20 mo. After 12 and 20 mo of feeding, ethanol-fed pigs had higher hepatic manganese-superoxide dismutase activity, lower hepatic copper concentrations and low hepatic copper-zinc-superoxide dismutase and glutathione peroxidase activities compared with controls. Lipid peroxidation as assessed by thiobarbituric acid reacting substance assay was lower in liver homogenate and mitochondrial and microsomal fractions from ethanol-fed pigs than in controls. The percentage contribution of highly unsaturated fatty acids to total fatty acids in liver homogenates (after 12 mo of feeding) and microsome fractions (after 20 mo of feeding) was lower in the ethanol-fed pigs than in the controls, resulting in a lower peroxidizability index. Ethanol-fed pigs had minimal or no hepatic damage as assessed by histological methods. We suggest that the relative resistance of microsomes to lipid peroxidation is due to the lower peroxidizability index in the ethanol-fed pigs and may account in part for the absence of significant histopathological findings after 20 mo of ethanol feeding. PMID:2050333

Zidenberg-Cherr, S; Olin, K L; Villanueva, J; Tang, A; Phinney, S D; Halsted, C H; Keen, C L

1991-06-01

300

Phase I Study of PARP Inhibitor ABT-888 in Combination with Topotecan in Adults with Refractory Solid Tumors and Lymphomas  

OpenAIRE

A phase I trial of ABT-888 (veliparib), a poly(ADP-ribose) polymerase (PARP inhibitor), in combination with topotecan, a topoisomerase I–targeted agent, was performed to determine maximum tolerated dose (MTD), safety, pharmacokinetics, and pharmacodynamics of the combination in patients with refractory solid tumors and lymphomas. Varying schedules and doses of intravenous topotecan in combination with ABT-888 (10 mg) administered orally twice a day (BID) were evaluated. Plasma and urine pha...

Kummar, Shivaani; Chen, Alice; Ji, Jiuping; Zhang, Yiping; Reid, Joel M.; Ames, Matthew; Jia, Lee; Weil, Marcie; Speranza, Giovanna; Murgo, Anthony J.; Kinders, Robert; Wang, Lihua; Parchment, Ralph E.; Carter, John; Stotler, Howard

2011-01-01

301

The Effect of Methyl, Hydroxyl, and Ketone Functional Groups on the Heterogeneous Oxidation of Succinic Acid Aerosol by OH Radicals  

Science.gov (United States)

The heterogeneous oxidation of atmospheric organic aerosols can influence their effects on climate, human health, and visibility. During oxidation, functionalization occurs when an oxygenated functional group is added to a molecule, leaving the carbon skeleton intact. Fragmentation involves carbon-carbon bond cleavage and produces two products with smaller carbon numbers than the parent compound. To gain better insights into how the molecular structure of more oxygenated organic compounds affects heterogeneous reactivity, succinic acid aerosols are photo-oxidized in an aerosol flow tube reactor, and the reaction products are analyzed using Direct Analysis in Real Time Mass Spectrometry for online chemical analysis. The effect of various functional groups (CH3, OH, C=O) along the carbon backbone on the heterogeneous reaction mechanisms are also investigated using model compounds. For this series of compounds, the formation of more oxygenated products through functionalization can be explained by well-known condensation-phase reactions such as Russell and Bennett and Summers. The number of fragmentation products is found to increase with the presence of OH and CH3 groups. This can be attributed to the increased number of tertiary carbons, enhancing the fragmentation after multiple oxidation steps. Smaller dicaids (oxalic acid and malonic acid) can be formed through the fragmentation processes in the heterogeneous oxidation of succinic acid. The effect of molecular structure on reaction kinetics, volatilization, and the relative importance of functionalization and fragmentation pathways will be discussed.

Chan, M.; Zhang, H.; Wilson, K. R.

2013-12-01

302

Radical scavenging and cytochrome P450 3A4 inhibitory activity of bergaptol and geranylcoumarin from grapefruit.  

Science.gov (United States)

Grapefruit juice has been shown to increase the oral bioavailability of several clinically important drugs by inhibiting first pass metabolism. Several compounds in grapefruit juice have shown different biological activities. Unique among them are furocoumarins with potent inhibitory activity against cytochrome P450 enzymes. In the present study, two bioactive compounds were isolated from grapefruit juice and grapefruit peel oil. The purity of the isolated compounds has been analyzed by HPLC. Structures of the compounds were elucidated by extensive NMR and mass spectral studies and identified as bergaptol and geranylcoumarin. The isolated compounds were tested for their radical scavenging activity using 2,2'-azobis (3-ethylbenz-thiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazil (DPPH) methods at different concentrations. Bergaptol showed very good radical scavenging activity at all the tested concentrations. Furthermore, these compounds were evaluated for their inhibitory activity against CYP3A4 enzyme. Bergaptol and geranylcoumarin were found to be potent inhibitors of debenzylation activity of CYP3A4 enzyme with an IC(50) value of 24.92 and 42.93 microM, respectively. PMID:17400460

Girennavar, Basavaraj; Jayaprakasha, G K; Jadegoud, Y; Nagana Gowda, G A; Patil, Bhimanagouda S

2007-06-01

303

The PARP inhibitor, ABT-888 potentiates temozolomide: correlation with drug levels and reduction in PARP activity in vivo.  

Science.gov (United States)

ABT-888 is a potent, orally bioavailable PARP-1/2 inhibitor shown to potentiate DNA damaging agents. The ability to potentiate temozolomide (TMZ) and develop a biological marker for PARP inhibition was evaluated in vivo. Doses/schedules that achieve TMZ potentiation in the B16F10 syngeneic melanoma model were utilized to develop an ELISA to detect a pharmacodynamic marker, ADP ribose polymers (pADPr), after ABT 888 treatment. ABT-888 enhanced TMZ antitumor activity, in a dose-proportional manner with no observed toxicity (44-75% tumor growth inhibition vs. TMZ monotherapy), but did not show single agent activity. Extended ABT-888 dosing schedules showed no advantage compared to simultaneous TMZ administration. Efficacy correlated with plasma/tumor drug concentrations. Intratumor drug levels correlated with a dose-proportional/time-dependent reduction in pADPr. Potentiation of TMZ activity by ABT-888 correlated with drug levels and inhibition of PARP activity in vivo. ABT-888 is in Phase 1 trials using a validated ELISA based on the assay developed here to assess pharmacological effect. PMID:19035287

Palma, Joann P; Rodriguez, Luis E; Bontcheva-Diaz, Velitchka D; Bouska, Jennifer J; Bukofzer, Gail; Colon-Lopez, Milagros; Guan, Ran; Jarvis, Kenneth; Johnson, Eric F; Klinghofer, Vered; Liu, Xuesong; Olson, Amanda; Saltarelli, Mary J; Shi, Yan; Stavropoulos, Jason A; Zhu, Gui-Dong; Penning, Thomas D; Luo, Yan; Giranda, Vincent L; Rosenberg, Saul H; Frost, David J; Donawho, Cherrie K

2008-01-01

304

Solvent effects on the antioxidant capacity of lipophilic and hydrophilic antioxidants measured by CUPRAC, ABTS/persulphate and FRAP methods.  

Science.gov (United States)

Antioxidants are health beneficial compounds that can protect cells and macromolecules (e.g., fats, lipids, proteins, and DNA) from the damage of reactive oxygen species (ROS). Solvent effect is a crucial parameter on the chemical behaviour of antioxidant compounds but there has been limited information regarding its role on antioxidant capacity and its assays. Therefore, the present study was undertaken to investigate the total antioxidant capacity (TAC) of some certain lipophilic and hydrophilic antioxidants, measured in different solvent media such as ethanol (EtOH) (100%), methanol (MeOH) (100%), methanol/water (4:1, v/v), methanol/water (1:1, v/v), dichloromethane (DCM)/EtOH (9:1, v/v). The cupric reducing antioxidant capacity (CUPRAC) values of selected antioxidants were experimentally reported in this work as trolox equivalent antioxidant capacity (TEAC), and compared to those found by reference TAC assays, i.e., 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)/persulphate (ABTS/persulphate) and ferric reducing antioxidant power (FRAP) methods. The TAC values of synthetic mixtures of antioxidants were experimentally measured as trolox equivalents and compared to those theoretically found by making use of the principle of additivity of absorbances assuming no chemical interaction between the mixture constituents. Possible synergistic (e.g., BHT and BHA in DCM/EtOH) or antagonistic behaviours of these synthetic mixtures were investigated in relation to solvent selection. PMID:20441899

Celik, Saliha Esin; Ozyürek, Mustafa; Güçlü, Kubilay; Apak, Re?at

2010-06-15

305

Effects of Various Cooking Methods on Content, Oxygen Radical Absorbance Capacity, and Bioaccessibility of Caffeoylquinic Acids in Ligularia fischeri (Ledeb. Turcz, Gom-Chi  

Directory of Open Access Journals (Sweden)

Full Text Available We hypothesized that cooking methods generally applied to Gom-chi preparation such as blanching, pan frying, and microwaving could change content, oxygen radical absorbance capacity (ORAC, and bioaccessibility of caffeoylquinic acids (CQAs. Mono-, di-, and tri-CQAs were identified and quantified by using an ultra-performance liquid chromatograph-photodiode array detector. In vitro biomimick system was performed for assessing the bioaccessibility of CQAs. The free radical scavenging capacity was measured by ORAC assay, expressed as trolox equivalents (TE. The amount of 5-CQA, 4-CQA, 3-CQA, and 3,4-di-CQA were 136.72, 2144.44, 16.81, and 421.93 ?g, respectively, in g of fresh Gom-chi. The highest amount of CQAs and TE was observed in microwaving for 3 min and pan frying for 3 min, respectively. The ranking of total CQAs were found in the order of microwaving 3 min (239.96 ?g/g > microwaving for 2 min (206.11 ?g/g > blanching for 3 min (191.94 ?g/g > blanching for 5 min (180.32 ?g/g > pan for frying 5 min (161.20 ?g/g > pan frying for 3 min (115.83 ?g/g. The bioaccessibility of total CQAs were 16.42, 17.64, 14.39, 13.29, and 12.43 (% in fresh, blanching for 3 min, blanching for 5 min, pan frying for 3 min, and pan frying for 5 min, respectively. Among the cooking methods, blanching for 3 min had the highest amount of CQAs after digestion. Our results suggest that blanching 3 min could be a suggested optimal cooking method for Gom-chi to improve CQAs absorption.

Yu-Ra Son

2014-07-01

306

Free radical scavenging reactions of hydroxybenzyl alcohols: a comparative study  

International Nuclear Information System (INIS)

Comparative studies on free radical scavenging by isomers of hydroxybenzyl alcohols were carried out. Hydroxyl radicals react with hydroxybenzyl alcohols giving adducts which in turn decay to phenoxyl radicals. Phenoxyl radicals were found to react with ascorbic acid efficiently. Inhibition of rat liver oxidative damage, such as lipid peroxidation, protein oxidation and MnSOD activity by HBAs have been investigated. (author)

307

Dosimetry in the megarad range by means of ESR-spectroscopy on free radicals of amino acids  

International Nuclear Information System (INIS)

Starting from the difficulties in determining doses in the range from 10 krd to 1 Mrd using conventional measuring techniques which are based on optical signals, a non-optical dosimetry technique is described using the paramagnetic absorption of irradiated organic materials whose approximate tissue equivalence allows widely energy independent dose determinations. On the example of the amino acid alanine, dosimetrical details are given and practical experiences with this technique are reported, such as dose-effect relationship, sensitivity scattering within a larger collection of detectors and signal loss with storage time. (author)

308

The wheat cytochrome oxidase subunit II gene has an intron insert and three radical amino acid changes relative to maize  

OpenAIRE

We have determined the sequence of the wheat mitochondrial gene for cytochrome oxidase subunit II (COII) and find that its derived protein sequence differs from that of maize at only three amino acid positions. Unexpectedly, all three replacements are non-conservative ones. The wheat COII gene has a highly-conserved intron at the same position as in maize, but the wheat intron is 1.5 times longer because of an insert relative to its maize counterpart. Hybridization analysis of mitochondrial D...

Bonen, Linda; Boer, Poppo H.; Gray, Michael W.

1984-01-01

309

RADICAL SCAVENGING POTENTIAL OF CLEOME VISCOSA L. AND CLEOME BURMANNI W. & A. (CLEOMACEAE)  

OpenAIRE

The present study evaluates the reactive oxygen species (ROS) scavenging and in vitro antioxidant activities of two species of Cleome, C. viscosa and C. burmanni. The antioxidant potential of the methanol extracts of species of Cleome was tested using different assays such as FRAP, DPPH, ABTS, hydroxyl, superoxide, nitric oxide, and hydrogen peroxide. The extracts gave positive results for all the assays and the radical scavenging ability was detected to be comparable to those of the correspo...

Nair, Lakshmi S. Pillai And Bindu R.

2013-01-01

310

Phase I study of PARP inhibitor ABT-888 in combination with topotecan in adults with refractory solid tumors and lymphomas.  

Science.gov (United States)

A phase I trial of ABT-888 (veliparib), a PARP inhibitor, in combination with topotecan, a topoisomerase I-targeted agent, was carried out to determine maximum tolerated dose (MTD), safety, pharmacokinetics, and pharmacodynamics of the combination in patients with refractory solid tumors and lymphomas. Varying schedules and doses of intravenous topotecan in combination with ABT-888 (10 mg) administered orally twice a day (BID) were evaluated. Plasma and urine pharmacokinetics were assessed and levels of poly(ADP-ribose) (PAR) and the DNA damage marker ?H2AX were measured in tumor and peripheral blood mononuclear cells (PBMC). Twenty-four patients were enrolled. Significant myelosuppression limited the ability to coadminister ABT-888 with standard doses of topotecan, necessitating dose reductions. Preclinical studies using athymic mice carrying human tumor xenografts also informed schedule changes. The MTD was established as topotecan 0.6 mg/m²/d and ABT-888 10 mg BID on days one to five of 21-day cycles. Topotecan did not alter the pharmacokinetics of ABT-888. A more than 75% reduction in PAR levels was observed in 3 paired tumor biopsy samples; a greater than 50% reduction was observed in PBMCs from 19 of 23 patients with measurable levels. Increases in ?H2AX response in circulating tumor cells (CTC) and PBMCs were observed in patients receiving ABT-888 with topotecan. We show a mechanistic interaction of a PARP inhibitor, ABT-888, with a topoisomerase I inhibitor, topotecan, in PBMCs, tumor, and CTCs. Results of this trial reveal that PARP inhibition can modulate the capacity to repair topoisomerase I-mediated DNA damage in the clinic. PMID:21795476

Kummar, Shivaani; Chen, Alice; Ji, Jiuping; Zhang, Yiping; Reid, Joel M; Ames, Matthew; Jia, Lee; Weil, Marcie; Speranza, Giovanna; Murgo, Anthony J; Kinders, Robert; Wang, Lihua; Parchment, Ralph E; Carter, John; Stotler, Howard; Rubinstein, Larry; Hollingshead, Melinda; Melillo, Giovanni; Pommier, Yves; Bonner, William; Tomaszewski, Joseph E; Doroshow, James H

2011-09-01

311

Exploiting the Synergy between Carboplatin and ABT-737 in the Treatment of Ovarian Carcinomas  

Science.gov (United States)

Platinum drug-resistance in ovarian cancers mediated by anti-apoptotic proteins such as Bcl-xL is a major factor contributing to the chemotherapeutic resistance of recurrent disease. Consequently, concurrent inhibition of Bcl-xL in combination with chemotherapy may improve treatment outcomes for patients. Here, we develop a mathematical model to investigate the potential of combination therapy with ABT-737, a small molecule inhibitor of Bcl-xL, and carboplatin, a platinum-based drug, on a simulated tumor xenograft. The model is calibrated against in vivo experimental data, wherein xenografts established in mice were treated with ABT-737 and/or carboplatin on a fixed periodic schedule. The validated model is used to predict the minimum drug load that will achieve a predetermined level of tumor growth inhibition, thereby maximizing the synergy between the two drugs. Our simulations suggest that the infusion-duration of each carboplatin dose is a critical parameter, with an 8-hour infusion of carboplatin given weekly combined with a daily bolus dose of ABT-737 predicted to minimize residual disease. The potential of combination therapy to prevent or delay the onset of carboplatin-resistance is also investigated. When resistance is acquired as a result of aberrant DNA-damage repair in cells treated with carboplatin, drug delivery schedules that induce tumor remission with even low doses of combination therapy can be identified. Intrinsic resistance due to pre-existing cohorts of resistant cells precludes tumor regression, but dosing strategies that extend disease-free survival periods can still be identified. These results highlight the potential of our model to accelerate the development of novel therapeutics such as BH3 mimetics. PMID:24400068

Jain, Harsh Vardhan; Richardson, Alan; Meyer-Hermann, Michael; Byrne, Helen M.

2014-01-01

312

3H-labeling of prokinetic motilide ABT-229 for biodistribution and metabolism studies  

International Nuclear Information System (INIS)

The prokinetic drug candidate, ABT-229, has been successfully [3H]-labeled in the macrolactone ring. This was accomplished with [3H]-NaBH4 reduction of the 11-ketone analog in a four step synthetic sequence beginning with the drug candidate. The 3H-labeled drug was obtained with specific activity of 9.0 Ci/mmol and radiochemical purity > 99%. This constitutes the first methodology for 3H-labeling of the macrolactone in an erythromycin derivative. (author)

313

Cupric ion reducing antioxidant capacity assay for antioxidants in human serum and for hydroxyl radical scavengers.  

Science.gov (United States)

Tests measuring the combined antioxidant effect of the nonenzymatic defenses in biological fluids may be useful in providing an index of the organism's capability to counteract reactive species known as pro-oxidants, resist oxidative damage, and combat oxidative stress-related diseases. The selected chromogenic redox reagent for the assay of human serum should be easily accessible, stable, selective, and respond to all types of biologically important antioxidants such as ascorbic acid, alpha-tocopherol, beta-carotene, reduced glutathione (GSH), uric acid, and bilirubin, regardless of chemical type or hydrophilicity. Our recently developed cupric reducing antioxidant capacity (CUPRAC) spectrophotometric method for a number of polyphenols and flavonoids using the copper(II)-neocuproine reagent in ammonium acetate buffer is now applied to a complete series of plasma antioxidants for the assay of total antioxidant capacity of serum, and the resulting absorbance at 450 nm is recorded either directly (e.g., for ascorbic acid, alpha-tocopherol, and glutathione) or after incubation at 50 degrees C for 20 min (e.g., for uric acid, bilirubin, and albumin), quantitation being made by means of a calibration curve. The lipophilic antioxidants, alpha-tocopherol and beta-carotene, are assayed in dichloromethane. Lipophilic antioxidants of serum are extracted with n-hexane from an ethanolic solution of serum subjected to centrifugation. Hydrophilic antioxidants of serum are assayed in the centrifugate after perchloric acid precipitation of proteins. The CUPRAC molar absorptivities, linear ranges, and TEAC (trolox equivalent antioxidant capacity) coefficients of the serum antioxidants are established, and the results are evaluated in comparison with the findings of the ABTS/TEAC reference method. The intra- and inter-assay coefficients of variation (CVs) are 0.7 and 1.5%, respectively, for serum. The CUPRAC assay proved to be efficient for glutathione and thiol-type antioxidants, for which the FRAP (ferric reducing antioxidant potency) test is basically nonresponsive. The additivity of absorbances of all the tested antioxidants confirmed that antioxidants in the CUPRAC test do not chemically interact among each other so as to cause an intensification or quenching of the theoretically expected absorbance, and that a total antioxidant capacity (TAC) assay of serum is possible. As a distinct advantage over other electron-transfer based assays (e.g., Folin, FRAP, ABTS, DPPH), CUPRAC is superior in regard to its realistic pH close to the physiological pH, favorable redox potential, accessibility and stability of reagents, and applicability to lipophilic antioxidants as well as hydrophilic ones. The CUPRAC procedure can also assay hydroxyl radicals, being the most reactive oxygen species (ROS). As a more convenient, efficient, and less costly alternative to HPLC/electrochemical detection techniques and to the nonspecific, low-yield TBARS test, we use p-aminobenzoate, 2,4- and 3,5-dimethoxybenzoate probes for detecting hydroxyl radicals generated from an equivalent mixture of [Fe(II)+EDTA] with hydrogen peroxide. The produced hydroxyl radicals attack both the probe and the water-soluble antioxidants in 37 degrees C-incubated solutions for 2 h. The CUPRAC absorbance of the ethylacetate extract due to the reduction of Cu(II)-neocuproine reagent by the hydroxylated probe decreases in the presence of (.)OH scavengers, the difference being proportional to the scavenging ability of the tested compound. The developed method is less lengthy, more specific, and of a higher yield than the classical TBARS assay. PMID:20072920

Apak, Re?at; Güçlü, Kubilay; Ozyürek, Mustafa; Bekta?o?lu, Burcu; Bener, Mustafa

2010-01-01

314

?-scission of ?-thioalkyl radicals. Time-resolved ESR detection in the pulse radiolysis of ?-(alkylthio)-substituted acetamide, acetic acid, and acetone  

International Nuclear Information System (INIS)

Full text: The pulse radiolysis of aqueous solutions of ?-(methylthio)acetamide CH3SCH2C(O)NH2, yields significant quantities of acetamide radicals, CH2C(O)NH2. The acetamide radicals were identified by time-resolved electron spin resonance (TRESR), and yields of the acetamide radicals were estimated at pH 1 and pH 7. The yields of the acetamide radicals roughly track the yields of hydrogen atoms from the radiolysis of water at both pH values. At low pH, where hydrated electrons are converted in large yield to hydrogen atoms, the yield of the acetamide radicals in proportionally higher than the yield at neutral pH. Although this correspondence, between the H-atom and acetamide yields, is evidence that the H-atoms could be main precursors of the acetamide radicals, molecular orbital calculations throw doubt on this as the main reaction pathway. At pH 1, the most plausible mechanism for formation of acetamide radicals is by hydroxyl radical attack at the sulfur atom, forming hydroxysulfuranyl radicals which decay by elimination of water; the resulting sulfur radical cations, in turn, decay via deprotonation forming CH2-S-CH2C(O)NH2 which decays via ?-scission. In similar experiments, CH2COOH radicals were identified by TRESR in the pulse radiolysis of low pH aqueous solutions of CH3SCH2COOH. A third example of ?-scission is given where CH22-C(O)CH3 radicals are observed following the pulse radiolysis of CH3CH2SCH2C(O)CH3

315

Hydrogen atom transfer from 1,n-alkanediamines to the cumyloxyl radical. Modulating C-H deactivation through acid-base interactions and solvent effects.  

Science.gov (United States)

A time-resolved kinetic study on the effect of trifluoroacetic acid (TFA) on the hydrogen atom transfer (HAT) reactions from 1,n-alkanediamines (R2N(CH2)nNR2, R = H, CH3; n = 1-4), piperazine, and 1,4-dimethylpiperazine to the cumyloxyl radical (CumO(•)), has been carried out in MeCN and DMSO. Very strong deactivation of the ?-C-H bonds has been observed following nitrogen protonation and the results obtained have been explained in terms of substrate basicity, of the distance between the two basic centers and of the solvent hydrogen bond acceptor ability. At [substrate] ? 1/2 [TFA] the substrates exist in the doubly protonated form HR2N(+)(CH2)nN(+)R2H, and no reaction with CumO(•) is observed. At 1/2 [TFA] [TFA], HAT occurs from the ?-C-H bonds of R2N(CH2)nNR2, and the mesured kH values are very close to those obtained in the absence of TFA. Comparison between MeCN and DMSO clearly shows that in the monoprotonated diamines R2N(CH2)nN(+)R2H remote C-H deactivation can be modulated through solvent hydrogen bonding. PMID:24869917

Milan, Michela; Salamone, Michela; Bietti, Massimo

2014-06-20

316

Grafting of Poly(methyl methacrylate) Brushes from Magnetite Nanoparticles Using a Phosphonic Acid Based Initiator by Ambient Temperature Atom Transfer Radical Polymerization (ATATRP)  

Science.gov (United States)

Poly(methyl methacrylate) in the brush form is grown from the surface of magnetite nanoparticles by ambient temperature atom transfer radical polymerization (ATATRP) using a phosphonic acid based initiator. The surface initiator was prepared by the reaction of ethylene glycol with 2-bromoisobutyrl bromide, followed by the reaction with phosphorus oxychloride and hydrolysis. This initiator is anchored to magnetite nanoparticles via physisorption. The ATATRP of methyl methacrylate was carried out in the presence of CuBr/PMDETA complex, without a sacrificial initiator, and the grafting density is found to be as high as 0.90 molecules/nm2. The organic inorganic hybrid material thus prepared shows exceptional stability in organic solvents unlike unfunctionalized magnetite nanoparticles which tend to flocculate. The polymer brushes of various number average molecular weights were prepared and the molecular weight was determined using size exclusion chromatography, after degrafting the polymer from the magnetite core. Thermogravimetric analysis, X-ray photoelectron spectra and diffused reflection FT-IR were used to confirm the grafting reaction.

Babu, Kothandapani; Dhamodharan, Raghavachari

2008-03-01

317

Lysosomal release of cathepsins causes ischemic damage in the rat hippocampal slice and depends on NMDA-mediated calcium influx, arachidonic acid metabolism, and free radical production.  

Science.gov (United States)

NMDA-mediated calcium entry and reactive oxygen species (ROS) production are well-recognized perpetrators of ischemic neuronal damage. The current studies show that these events lead to the release of the protein hydrolase, cathepsin B, from lysosomes 2 h following 5-min oxygen-glucose deprivation in the rat hippocampal slice. This release reflects a lysosomal membrane permeabilization (LMP) and was measured as the appearance of diffuse immunolabeled cathepsin B in the cytosol of CA1 pyramidal neurons. Necrotic neuronal damage begins after the release of cathepsins and is prevented by inhibitors of either cathepsin B or D indicating that the release of cathepsins is an important mediator of severe damage. There was an increase in superoxide levels, measured by dihydroethidium fluorescence, at the same time as LMP and reducing ROS levels with antioxidants, Trolox or N-tert-butyl-alpha-phenyl nitrone, blocked LMP. Both LMP and ROS production were blocked by an NMDA channel blocker (MK-801) and by inhibitors of mitogen-activated protein kinase kinase (U0126), calcium-dependent/independent phospholipases A2 (methyl arachidonyl fluorophosphonate) but not calcium-independent phospholipases A2 (bromoenol lactone) and cyclooxygenase-2 (NS398). A cell-permeant specific inhibitor of calpain (PD150606) prevented LMP, but not ROS production. It is concluded that LMP results in part from calcium-initiated and extracellular signal-regulated kinase-initiated arachidonic acid metabolism, which produces free radicals; it also requires the action of calpain. PMID:18363826

Windelborn, James A; Lipton, Peter

2008-07-01

318

Free-Radical Scavenging Properties and Reducing Power of Grape Cane Extracts from 11 Selected Grape Cultivars Widely Grown in China  

OpenAIRE

Total phenolic contents (TPC), total flavonoid contents (TFC), related antioxidative and antiradical capabilities of grape cane extracts from 11 varieties (five V. vinifera cultivars and six Chinese wild grapes) widely grown in China were evaluated. Antioxidant properties were determined as DPPH and ABTS radical-scavenging abilities, superoxide anion and hydroxyl radical and hydrogen peroxide scavenging assays, as well as reducing power. Phenolic profiles of the extracts were characterized by...

Ang Zhang; Yulin Fang; Hua Wang; Hua Li; Zhenwen Zhang

2011-01-01

319

MEK Inhibition Enhances ABT-737-Induced Leukemia Cell Apoptosis via Prevention of ERK activated MCL-1 induction and Modulation of MCL-1/BIM Complex  

OpenAIRE

Recently, strategies for AML therapy have been developed that target anti-apoptotic BCL2 family members using BH3 mimetic drugs such as ABT-737. Though effective against BCL2 and BCL-XL, ABT-737 poorly inhibits MCL-1. Here we report that, unexpectedly, ABT-737 induces activation of ERK and induction of MCL-1 in AML cells. MEK inhibitors such as PD0325901 and CI-1040 have been used successfully to suppress MCL-1. We report that PD0325901 blocked ABT-737 –induced MCL-1 expression and when com...

Konopleva, M.; Milella, M.; Ruvolo, P.; Watts, Jc; Ricciardi, MR; Korchin, B.; Teresa, Mcqueen; Bornmann, William; Tsao, T.; Bergamo, P.; Mak, Dh; Chen, W.; Mccubrey, J.; Tafuri, A.; Andreeff, M.

2012-01-01

320

MEK Inhibition Enhances ABT-737-Induced Leukemia Cell Apoptosis via Prevention of ERK activated MCL-1 induction and Modulation of MCL-1/BIM Complex  

Science.gov (United States)

Recently, strategies for AML therapy have been developed that target anti-apoptotic BCL2 family members using BH3 mimetic drugs such as ABT-737. Though effective against BCL2 and BCL-XL, ABT-737 poorly inhibits MCL-1. Here we report that, unexpectedly, ABT-737 induces activation of ERK and induction of MCL-1 in AML cells. MEK inhibitors such as PD0325901 and CI-1040 have been used successfully to suppress MCL-1. We report that PD0325901 blocked ABT-737 –induced MCL-1 expression and when combined with ABT-737 resulted in potent synergistic killing of AML derived cell lines, primary AML blast and CD34+38?123+ progenitor/stem cells. Finally, we tested the combination of ABT-737 and CI-1040 in a murine xenograft model using MOLM-13 human leukemia cells. While control and CI-1040 treated mice exhibited progressive leukemia growth, ABT-737 and, to a significantly greater extent, ABT-737 + CI-1040 exerted major anti-leukemia activity. Collectively, results demonstrate unexpected anti-apoptotic interaction between the BCL2 family-targeted BH3 mimetic ABT-737 and MAPK signaling in AML cells: the BH3 mimetic is not only restrained in its activity by MCL-1, but also induces it’s expression. However, concomitant inhibition by BH3 mimetics and MEK inhibitors could abrogate this effect and may be developed into a novel and effective therapeutic strategy for patients with AML. PMID:22064351

Konopleva, M; Milella, M; Ruvolo, P; Watts, JC; Ricciardi, MR; Korchin, B; Teresa, McQueen; Bornmann, William; Tsao, T; Bergamo, P; Mak, DH; Chen, W; McCubrey, J; Tafuri, A; Andreeff, M

2013-01-01

321

Improved production of poly-?-glutamic acid by Bacillus subtilis D7 isolated from Doenjang, a Korean traditional fermented food, and its antioxidant activity.  

Science.gov (United States)

The objectives of this study was to improve poly-?-glutamic acid (?-PGA) production by Bacillus subtilis D7 isolated from a Korean traditional fermented food and to assess its antioxidant activity for applications in the cosmetics and pharmaceutical industries. Strain D7 produced ?-PGA in the absence of L-glutamic acid, indicating L-glutamic acid-independent production. However, the addition of L-glutamic acid increased ?-PGA production. Several tricarboxylic acid cycle intermediates and amino acids could serve as the metabolic precursors for ?-PGA production, and the addition of pyruvic acid and D-glutamic acid to culture medium improved the yield of ?-PGA markedly. The maximum yield of ?-PGA obtained was 24.93?±?0.64 g/l in improved medium, which was about 5.4-fold higher than the yield obtained in basal medium. ?-PGA was found to have 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (46.8?±?1.5 %), hydroxyl radical scavenging activity (52.0?±?1.8 %), 2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonate (ABTS) radical scavenging activity (42.1?±?1.8 %), nitric oxide scavenging activity (35.1?±?1.3 %), reducing power (0.304?±?0.008), and metal chelating activity (91.3?±?3.5 %). These results indicate that ?-PGA has a potential use in the food, cosmetics, and biomedical industries for the development of novel products with radical scavenging activity. As far as we are aware, this is the first report to describe the antioxidant activityof ?-PGA produced by bacteria. PMID:24733532

Lee, Na-Ri; Lee, Sang-Mee; Cho, Kwang-Sik; Jeong, Seong-Yun; Hwang, Dae-Youn; Kim, Dong-Seob; Hong, Chang-Oh; Son, Hong-Joo

2014-06-01

322

Antioxidant activity of a catechol derived from abietic acid.  

Science.gov (United States)

The demand for novel effective antioxidant-based drugs has led to the synthesis and evaluation of the antioxidant potential in several molecules derived from natural compounds. In this work the in vitro antioxidant activity of an abietic acid-derived catechol (methyl 11,12-dihydroxyabietate-8,11,13-trien-18-oate, MDTO) was evaluated. This substance, possessing important biological properties, is similar to carnosic acid, a natural antioxidant from rosemary or sage leaves. Aiming to understand the antioxidant activity of MDTO, the energetics of its O-H bond, using time-resolved photoacoustic calorimetry (TR-PAC), was investigated. On energetic grounds it is predicted that MDTO is a good free radical scavenger, although its activity is lower than that of quercetin, a very effective antioxidant, which was used for comparison. In agreement with these predictions, the DPPH(*) and ABTS(*+) radical scavenging activities are lower than those of quercetin. In addition, MDTO also reacts with HOCl, a powerful proinflammatory oxidant produced by activated neutrophils, and protects liposomes against iron-ascorbate-induced oxidation. The discussion of these results foresees potential applications of MDTO as an antioxidant. PMID:16417289

Justino, Gonçalo C; Correia, Catarina F; Mira, Lurdes; Borges Dos Santos, Rui M; Martinho Simões, José A; Silva, Ana M; Santos, Célia; Gigante, Bárbara

2006-01-25

323

Fatty Acid and Essential Oil Compositions of Trifolium angustifolium var. angustifolium with Antioxidant, Anticholinesterase and Antimicrobial Activities.  

Science.gov (United States)

This study represents the first report on the chemical composition and biological activity of Trifolium angustifolium var. angustifolium. The major components of the essential oil were identified as hexatriacontene (23.0%), arachidic acid (15.5%) and ?-selinene (10.0%). The main constituents of the fatty acid obtained from the petroleum ether extract were identified as palmitic acid (29.8%), linoleic acid (18.6%) and oleic acid (10.5%). In particular, the water extract exhibited higher activity than ?-tocopherol and BHT, which were used as standards in the ABTS cation radical scavenging assay and indicated higher inhibitory effect against acetylcholinesterase enzyme than the reference compound, galanthamine but exhibited weak activity in ?-carotene bleaching, DPPH-free radical scavenging, and cupric-reducing antioxidant capacity assays. The petroleum ether extract exhibited higher activity than ?-tocopherol which was used as standard in the ?-carotene bleaching method at concentration 100 ?g/mL. The acetone extract exhibited higher activity than ?-tocopherol which was used as standard cupric reducing antioxidant capacity (CUPRAC) method at 100 ?g/mL concentration. The acetone and methanol extracts were active on all microorganisms tested with a small zone diameter indicating weak activity. PMID:25561929

Erta?, Abdulselam; Bo?a, Mehmet; Ha?imi, Nesrin; Y?lmaz, Mustafa Abdullah

2015-01-01

324

Fatty Acid and Essential Oil Compositions of Trifolium angustifolium var. angustifolium with Antioxidant, Anticholinesterase and Antimicrobial Activities  

Science.gov (United States)

This study represents the first report on the chemical composition and biological activity of Trifolium angustifolium var. angustifolium. The major components of the essential oil were identified as hexatriacontene (23.0%), arachidic acid (15.5%) and ?-selinene (10.0%). The main constituents of the fatty acid obtained from the petroleum ether extract were identified as palmitic acid (29.8%), linoleic acid (18.6%) and oleic acid (10.5%). In particular, the water extract exhibited higher activity than ?-tocopherol and BHT, which were used as standards in the ABTS cation radical scavenging assay and indicated higher inhibitory effect against acetylcholinesterase enzyme than the reference compound, galanthamine but exhibited weak activity in ?-carotene bleaching, DPPH-free radical scavenging, and cupric-reducing antioxidant capacity assays. The petroleum ether extract exhibited higher activity than ?-tocopherol which was used as standard in the ?-carotene bleaching method at concentration 100 ?g/mL. The acetone extract exhibited higher activity than ?-tocopherol which was used as standard cupric reducing antioxidant capacity (CUPRAC) method at 100 ?g/mL concentration. The acetone and methanol extracts were active on all microorganisms tested with a small zone diameter indicating weak activity. PMID:25561929

Erta?, Abdulselam; Bo?a, Mehmet; Ha?imi, Nesrin; Y?lmaz, Mustafa Abdullah

2015-01-01

325

Synthesis and Biological Evaluation of New 1,3-Thiazolidine-4-one Derivatives of 2-(4-Isobutylphenylpropionic Acid  

Directory of Open Access Journals (Sweden)

Full Text Available New thiazolidine-4-one derivatives of 2-(4-isobutylphenylpropionic acid (ibuprofen have been synthesized as potential anti-inflammatory drugs. The structure of the new compounds was proved using spectral methods (FR-IR, 1H-NMR, 13C-NMR, MS. The in vitro antioxidant potential of the synthesized compounds was evaluated according to the total antioxidant activity, the DPPH and ABTS radical scavenging assays. Reactive oxygen species (ROS and free radicals are considered to be involved in many pathological events like diabetes mellitus, neurodegenerative diseases, cancer, infections and more recently, in inflammation. It is known that overproduction of free radicals may initiate and amplify the inflammatory process via upregulation of genes involved in the production of proinflammatory cytokines and adhesion molecules. The chemical modulation of acyl hydrazones of ibuprofen 3a–l through cyclization to the corresponding thiazolidine-4-ones 4a–n led to increased antioxidant potential, as all thiazolidine-4-ones were more active than their parent acyl hydrazones and also ibuprofen. The most active compounds are the thiazolidine-4-ones 4e, m, which showed the highest DPPH radical scavenging ability, their activity being comparable with vitamin E.

Ioana Mirela Vasincu

2014-09-01

326

Formation of semiquinone radical anion and free radical scavenging reactions of plumbagin. A pulse radiolysis study  

International Nuclear Information System (INIS)

Kinetics and mechanism of scavenging of reducing free radicals by plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone) are studied using pulse radiolysis technique. It scavenged superoxide radical, hydroxyethyl radical and hydrated electron with bimolecular rate constants of 8.9 × 107, 2.3 × 109 and 1.6 × 1010 M-1 s-1, respectively in aqueous-alcohol medium. Plumbagin also scavenged linoleic acid peroxyl radical and tyrosyl radical with bimolecular rate constants of 1.0 × 108 and 7.0 × 106 M-1 s-1, respectively. Further, redox properties of plumbagin and its transients are studied using standard redox couples and cyclic voltammetry. (author)

327

Free radical scavenging activity of Lafoensia pacari.  

Science.gov (United States)

The methanolic extract of the stem bark of Lafoensia pacari (Lythraceae) showed free radical scavenging activity in the diphenyl picryl hydrazyl radical (DPPH) decoloration assay and inhibited the enzyme xanthine oxidase 'in vitro'. Bioassay-guided isolation led to ellagic acid (EA) as the main active compound of Brazilian and Paraguayan collections of the plant. PMID:10967469

Solon, S; Lopes, L; Teixeira de Sousa, P; Schmeda-Hirschmann, G

2000-09-01

328

Targeting CDK9 by wogonin and related natural flavones potentiates the anti-cancer efficacy of the Bcl-2 family inhibitor ABT-263.  

Science.gov (United States)

Tumor initiation, progression and resistance to therapies are tightly associated with over-expression of anti-apoptotic proteins Bcl-2, Bcl-x(L), Bcl-w and Mcl-1. ABT-263 (Navitoclax), an orally bio-available small-molecule mimetic of the Bcl-2 homology domain 3, inhibits Bcl-2, Bcl-x(L), and Bcl-w and has shown anti-cancer effects mainly on lymphomas and lymphocytic leukemia. Despite promising results obtained from the clinical trials, the use of ABT-263 in patients is dose-limited due to causing thrombocytopenia via inhibition of Bcl-x(L) in platelets. ABT-199 specifically inhibits Bcl-2; however, its use is limited to tumors over-expressing only Bcl-2. Besides, many tumors resist treatment due to high levels of Mcl-1 expression or develop resistance via up-regulation of Mcl-1 during long-term exposure. These obstacles highlight the demand to improve the ABT-263-based therapy. In this study, we show that anti-cancer flavones, e.g., wogonin, baicalein, apigenin, chrysin and luteolin enhance ABT-263-induced apoptosis in different cancer cell lines and in primary AML and ALL cells by down-regulation of Mcl-1 expression. Importantly, wogonin does not enhance the toxicity of ABT-263 to proliferating normal T cells and thrombocytes. Wogonin also potentiates the lethality of ABT-263 in cancer cells which have acquired resistance to ABT-263. Furthermore, we show that combination of wogonin with ABT-263 promotes in vivo tumor regression in a human T-cell leukemia xenograft mouse model. Our study demonstrates that wogonin (and related flavones) reduce the effective dose of ABT-263 thereby possibly decreasing the risk of adverse side effects. PMID:24895203

Polier, Gernot; Giaisi, Marco; Köhler, Rebecca; Müller, Wolfgang W; Lutz, Christoph; Buss, Eike C; Krammer, Peter H; Li-Weber, Min

2015-02-01

329

Mathematical evaluation of the amino acid and polyphenol content and antioxidant activities of fruits from different apricot cultivars.  

Science.gov (United States)

Functional foods are of interest because of their significant effects on human health, which can be connected with the presence of some biologically important compounds. In this study, we carried out complex analysis of 239 apricot cultivars (Prunus armeniaca L.) cultivated in Lednice (climatic area T4), South Moravia, Czech Republic. Almost all previously published studies have focused only on analysis of certain parameters. However, we focused on detection both primary and secondary metabolites in a selection of apricot cultivars with respect to their biological activity. The contents of thirteen biogenic alpha-L-amino acids (arginine, asparagine, isoleucine, lysine, serine, threonine, valine, leucine, phenylalanine, tryptophan, tyrosine, proline and alanine) were determined using ion exchange chromatography with UV-Vis spectrometry detection. Profile of polyphenols, measured as content of ten polyphenols with significant antioxidant properties (gallic acid, procatechinic acid, p-aminobenzoic acid, chlorogenic acid, caffeic acid, vanillin, p-coumaric acid, rutin, ferrulic acid and quercetrin), was determined by high performance liquid chromatography with spectrometric/electrochemical detection. Moreover, content of total phenolics was determined spectrophotometrically using the Folin-Ciocalteu method. Antioxidant activity was determined using five independent spectrophotometric methods: DPPH assay, DMPD method, ABTS method, FRAP and Free Radicals methods. Considering the complexity of the obtained data, they were processed and correlated using bioinformatics techniques (cluster analysis, principal component analysis). The studied apricot cultivars were clustered according to their common biochemical properties, which has not been done before. The observed similarities and differences were discussed. PMID:21886093

Sochor, Jiri; Skutkova, Helena; Babula, Petr; Zitka, Ondrej; Cernei, Natalia; Rop, Otakar; Krska, Boris; Adam, Vojtech; Provazník, Ivo; Kizek, Rene

2011-01-01

330

Mathematical Evaluation of the Amino Acid and Polyphenol Content and Antioxidant Activities of Fruits from Different Apricot Cultivars  

Directory of Open Access Journals (Sweden)

Full Text Available Functional foods are of interest because of their significant effects on human health, which can be connected with the presence of some biologically important compounds. In this study, we carried out complex analysis of 239 apricot cultivars (Prunus armeniaca L. cultivated in Lednice (climatic area T4, South Moravia, Czech Republic. Almost all previously published studies have focused only on analysis of certain parameters. However, we focused on detection both primary and secondary metabolites in a selection of apricot cultivars with respect to their biological activity. The contents of thirteen biogenic alpha-L-amino acids (arginine, asparagine, isoleucine, lysine, serine, threonine, valine, leucine, phenylalanine, tryptophan, tyrosine, proline and alanine were determined using ion exchange chromatography with UV-Vis spectrometry detection. Profile of polyphenols, measured as content of ten polyphenols with significant antioxidant properties (gallic acid, procatechinic acid, p-aminobenzoic acid, chlorogenic acid, caffeic acid, vanillin, p-coumaric acid, rutin, ferrulic acid and quercetrin, was determined by high performance liquid chromatography with spectrometric/electrochemical detection. Moreover, content of total phenolics was determined spectrophotometrically using the Folin-Ciocalteu method. Antioxidant activity was determined using five independent spectrophotometric methods: DPPH assay, DMPD method, ABTS method, FRAP and Free Radicals methods. Considering the complexity of the obtained data, they were processed and correlated using bioinformatics techniques (cluster analysis, principal component analysis. The studied apricot cultivars were clustered according to their common biochemical properties, which has not been done before. The observed similarities and differences were discussed.

Rene Kizek

2011-09-01

331

The ?7 nicotinic receptor agonist ABT-107 protects against nigrostriatal damage in rats with unilateral 6-hydroxydopamine lesions.  

Science.gov (United States)

The finding that smoking is inversely correlated with Parkinson's disease and that nicotine attenuates nigrostriatal damage in Parkinsonian animals supports the idea that nicotine may be neuroprotective. Nicotine is thought to exert this effect by acting at nicotinic receptors (nAChRs), including the ?7 subtype. The objective of this study was twofold: first, to test the protective potential of ABT-107, an agonist with high selectivity for ?7 nAChRs; and second, to investigate its cellular mechanism of action. Rats were implanted with minipumps containing ABT-107 (0.25mg/kg/d). In addition, we tested the effect of nicotine (1mg/kg/d) as a positive control, and also DMXB (2mg/kg/d) which acts primarily with ?7 but also ?4?2* nAChRs. Two weeks after minipump placement, the rats were lesioned by unilateral administration of 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle. Lesioning alone decreased contralateral forelimb use and adjusted stepping, two measures of Parkinsonism. ABT-107 and nicotine treatment significantly improved these behaviors at all weeks tested, with variable improvement with DMXB. We next investigated the cellular mechanism involved. The striatal dopamine transporter (DAT), a marker of dopaminergic integrity, was reduced ~70% with lesioning. ABT-107 or nicotine treatment significantly increased DAT levels in lesioned striatum; these drugs did not alter DAT levels in intact striatum. ABT-107 and nicotine also significantly improved basal dopamine release from lesioned striatum, as well as nicotine-stimulated dopamine release mediated via ?4?2* and ?6?2* nAChRs. These data suggest that ?7 nAChR agonists may improve motor behaviors associated with nigrostriatal damage by enhancing striatal dopaminergic function. PMID:25261754

Bordia, Tanuja; McGregor, Matthew; Papke, Roger L; Decker, Michael W; McIntosh, J Michael; Quik, Maryka

2015-01-01

332

Ignorance Radicalized  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this paper is twofold. I criticize Michael Devitt's linguistic---as opposed to Chomsky's psychological---conception of linguistics on the one hand, and I modify his related view on linguistic intuitions on the other. I argue that Devitt's argument for the linguistic conception is in conflict with one of the main theses of that very conception, according to which linguistics should be about physical sentence tokens of a given language rather than about the psychologically real competence of native speakers. The basis of this conflict is that Devitt's view on language, as I will show, inherits too much from the criticized Chomskian view. This is also the basis of Devitt's strange claim that it is the linguist, and not the ordinary speaker, whose linguistic intuition should have an evidential role in linguistics. I will argue for the opposite by sketching a view on language that is more appropriate to the linguistic conception. That is, in criticizing Devitt, I am not defending the Chomskian approach. My aim is to radicalize Devitt's claims.

Gergo Somodi

2009-12-01

333

Free Radical Scavenging Activity of Mussaenda glabra  

Directory of Open Access Journals (Sweden)

Full Text Available The flowers of Mussaenda glabra occurring in white and pink have been evaluated for their anti oxidant property. The white (MGW and the pink (MGP varieties showed considerable NO scavenging activity. The IC50 values were found to be 92.79 and 122.45 ?g mL-1, respectively. MGW inhibited lipid peroxidation to a greater extent when compared to MGP. MGW showed 50% inhibition at the concentration of 112.4 ?g mL-1 while MGP at 53.42 ?g mL-1. The reducing power was found in a dose dependent manner. The pink variety showed greater reducing power when compared to white variety. Both the extracts showed hydroxyl radical and ABTS radical scavenging property. The total phenolic content was 17.5 and 8.3 mg g-1 in MGP and MGW, respectively. The HPTLC fingerprinting showed peaks due to flavonoids. The results show that both are having considerable anti oxidant property. The abundance of this flower throughout the year can be used for evaluating its medicinal value.

K.S. Vidyalakshmi

2006-01-01

334

Detection of Aryl Radicals in Hydrodediazoniations.  

Science.gov (United States)

Iodoacetic acid, an effective aryl radical trapping agent, was employed to investigate the reactive intermediates in several hydrodediazoniations. Isolation of an aryl iodide constitutes a positive result in the test for aryl radicals. Equally as important is the lower yield of the reduction product when the trap diverts radicals from their usual reaction path. Hydrodediazoniations performed in MeOH, EtOH, i-PrOH, benzyl alcohol, THF, tetramethylurea, formamide, and hypophosphorous acid all involve aryl radical intermediates. Ferrocene was found to be an effective initiator in most of these reactions; through its action as an electron donor, it serves to shorten reaction times and to improve yields of hydrodediazoniation products. All hydrodediazoniations examined, whether initiated or not, involve radical intermediates. PMID:11671965

Wassmundt, Frederick W.; Kiesman, William F.

1997-11-28

335

EPR parameters of amino acid radicals in P. eryngii versatile peroxidase and its W164Y variant computed at the QM/MM level.  

Science.gov (United States)

Quantum mechanics/molecular mechanics (QM/MM) methods, employing density functional theory (DFT), have been used to compute the electron paramagnetic resonance (EPR) parameters of tryptophan and tyrosyl radical intermediates involved in the catalytic cycle of Pleurotus eryngii versatile peroxidase (VP) and its W164Y variant, respectively. These radicals have been previously experimentally detected and characterized both in the two-electron and one-electron activated forms of the enzymes. In this work, the well-studied W164 radical in VP has been chosen for calibration purposes because its spectroscopic properties have been extensively studied by multifrequency EPR and ENDOR spectroscopies. Using a B3LYP/CHARMM procedure, appropriately accounting for electrostatic, such as hydrogen bonding, and steric environmental interactions, a good agreement between the calculated and measured EPR parameters for both radicals has been achieved; g-tensors, hyperfine coupling constants (hfcc) and Mulliken spin densities have been correlated to changes in geometries, hydrogen bond networks and electrostatic environment, with the aim of understanding the influence of the protein surroundings on EPR properties. In addition, the present calculations demonstrate, for VP, the formation of a neutral tryptophan radical, hydrogen bonded to the nearby E243, via a stepwise electron and proton transfer with earlier involvement of a short-lived tryptophan cationic species. Instead, for W164Y, the QM/MM dynamics simulation shows that the tyrosine oxidation proceeds via a concerted electron and proton transfer and is accompanied by a significant reorganization of residues and water molecules surrounding the tyrosyl radical. PMID:21301713

Bernini, Caterina; Pogni, Rebecca; Ruiz-Dueñas, Francisco J; Martínez, Angel T; Basosi, Riccardo; Sinicropi, Adalgisa

2011-03-21

336

Investigation of the reactions of stable nitroxyl radical Pt. 2  

International Nuclear Information System (INIS)

The study of the reactions of the stable nitroxyl radical 2,2,5,5-tetramethyl-4-phenyl-3-imidazoline-3-oxyd-1-oxyl (I) with OH, HO2 and O2- radicals formed by ?-irradiation of aqueous solutions in acidic, neutral and alkaline media is described. It was found, that (I) reacts with OH radicals in two different ways: by saturation of the free valency of nitroxyl radical, and by attacking the benzene ring of the radical molecule without affecting the free valency. Furthermore it is shown that (I) does not react with HO2 and O2- peroxy-radicals. (author)

337

Combined treatment with ABT-737 and VX-680 induces apoptosis in Bcl-2- and c-FLIP-overexpressing breast carcinoma cells.  

Science.gov (United States)

ABT-737, a BH3-mimetic small-molecule inhibitor, binds with very high affinity to Bcl-2, Bcl-xL and Bcl-w, and inhibits their activity. Aurora kinase is one of the serine/threonine kinase family members and is a vital and critical regulator of mitosis and meiosis. In the present study, we investigated the effects and mechanisms of a combined treatment of ABT-737 and VX-680 (Aurora kinase inhibitor) in human breast cancer MDA-MB?435S cells. ABT-737 plus VX-680 induced caspase-dependent apoptosis in the human breast cancer cells. Combined treatment with ABT-737 and VX-680 led to the downregulation of Bcl-2 expression at the transcriptional level and the downregulation of c-FLIP and Mcl-1 expression at the post-transcriptional level. Overexpression of Bcl-2 or c-FLIP could not block the induction of apoptosis caused by the combined treatment with ABT-737 and VX-680. However, overexpression of Mcl-1 partially inhibited the induction of apoptosis. In contrast, the combined treatment with ABT-737 and VX680 had no effect on the apoptosis in normal cells. Taken together, our study demonstrated that combined treatment with ABT-737 and VX-680 induced apoptosis in anti?apoptotic protein (Bcl-2 or c-FLIP)-overexpressing cells. PMID:25592064

Choi, Jung Eun; Woo, Seon Min; Min, Kyoung-Jin; Kang, Su Hwan; Lee, Soo Jung; Kwon, Taeg Kyu

2015-03-01

338

MEK inhibition enhances ABT-737-induced leukemia cell apoptosis via prevention of ERK-activated MCL-1 induction and modulation of MCL-1/BIM complex.  

Science.gov (United States)

Recently, strategies for acute myeloid leukemia (AML) therapy have been developed that target anti-apoptotic BCL2 family members using BH3-mimetic drugs such as ABT-737. Though effective against BCL2 and BCL-X(L), ABT-737 poorly inhibits MCL-1. Here we report that, unexpectedly, ABT-737 induces activation of the extracellular receptor activated kinase and induction of MCL-1 in AML cells. MEK inhibitors such as PD0325901 and CI-1040 have been used successfully to suppress MCL-1. We report that PD0325901 blocked ABT-737-induced MCL-1 expression, and when combined with ABT-737 resulted in potent synergistic killing of AML-derived cell lines, primary AML blast and CD34+38-123+ progenitor/stem cells. Finally, we tested the combination of ABT-737 and CI-1040 in a murine xenograft model using MOLM-13 human leukemia cells.Whereas control mice and CI-1040-treated mice exhibited progressive leukemia growth, ABT-737, and to a significantly greater extent, ABT-737+CI-1040 exerted major anti-leukemia activity. Collectively, results demonstrated unexpected anti-apoptotic interaction between the BCL2 family-targeted BH3-mimetic ABT-737 and mitogen-activated protein kinase signaling in AML cells: the BH3 mimetic is not only restrained in its activity by MCL-1, but also induces its expression. However, concomitant inhibition by BH3 mimetics and MEK inhibitors could abrogate this effect and may be developed into a novel and effective therapeutic strategy for patients with AML. PMID:22064351

Konopleva, M; Milella, M; Ruvolo, P; Watts, J C; Ricciardi, M R; Korchin, B; McQueen, T; Bornmann, W; Tsao, T; Bergamo, P; Mak, D H; Chen, W; McCubrey, J; Tafuri, A; Andreeff, M

2012-04-01

339

Antioxidant activities and radical scavenging activities of flavonoids studied by the electrochemical methods and ESR technique based on the novel paramagnetic properties of poly(aniline-co-5-aminosalicylic acid)  

International Nuclear Information System (INIS)

Graphical abstract: ESR spectra of the PAASA/RGO/graphite electrodes: (1) in the buffer solution consisting of 0.20 M phosphate and methanol (80: 20, v/v), (2) in the buffer solutions containing 150 ?M of (+)-catechin. -- Abstract: Four kinds of flavonoid, viz. flavanone naringenin, Flavone apigenin, flavonol kaempferol, and flavanol (+)-catechin, are used to investigate their antioxidant and radical scavenging activitis in the water-methanol solution of pH 6.3, using the electrochemical methods and electron spin resonance (ESR) technique. Poly(aniline-co-5-aminosalicylic acid) (PAASA) is first used as a radical source that was polymerized on a reduced graphene oxide (RGO)/glassy carbon (GC) disk or on the RGO/graphite fiber electrode. The assessment of the antioxidant activities is performed using both cyclic voltammetry and the open circuit potential measurement. On the basis of results from both electrochemical mathods, the order of the antioxidant actitvities of flavonoids is as follows: (+)-catechin > kaempferol > apigenin > naringenin However, the difference in the antioxidant activities between naringenin and apigenin is very small. On the basis of the ESR signal intensities of PAASA, the order of the radical scavenging activities of flavonoids is in good agreement with that of the above antioxdant activities.Three oxidation peaks on the cyclic voltammograms of (+)-catechin are first detected, which gives us a deep insight into the oxidation mechanism of (+)-catechin

340

In Vitro Activity of ABT-773 against Legionella pneumophila, Its Pharmacokinetics in Guinea Pigs, and Its Use to Treat Guinea Pigs with L. pneumophila Pneumonia  

OpenAIRE

The activity of ABT-773 was studied against extracellular and intracellular Legionella pneumophila and for the treatment of guinea pigs with L. pneumophila pneumonia. The ABT-773 MIC at which 50% of isolates are inhibited (MIC50) for 20 different Legionella sp. strains was 0.016 ?g/ml, whereas the MIC50s of clarithromycin and erythromycin were 0.032 and 0.125 ?g/ml, respectively. ABT-773 (1 ?g/ml) was bactericidal for two L. pneumophila strains grown in guinea pig alveolar macrophages. In ...

Edelstein, Paul H.; Higa, F.; Edelstein, Martha A. C.

2001-01-01

341

ABT-737 Induces Bim Expression via JNK Signaling Pathway and Its Effect on the Radiation Sensitivity of HeLa Cells  

OpenAIRE

ABT-737 is a BH3 mimetic small molecule inhibitor that can effectively inhibit the activity of antiapoptotic Bcl-2 family proteins including Bcl2, Bcl-xL and Bcl-w, and further enhances the effect of apoptosis by activating the proapoptotic proteins (t-Bid, Bad, Bim). In this study, we demonstrate that ABT-737 improved the radiation sensitivity of cervical cancer HeLa cells and thereby provoked cell apoptosis. Our results show that ABT-737 inhibited HeLa cell proliferation and activated JNK a...

Wang, Huan; Yang, Yue-bo; Shen, Hui-min; Gu, Jian; Li, Tian; Li, Xiao-mao

2012-01-01

342

In vitro reduction of coplanar PCB congeners by ABTS oxidases from the culture of Trametes versicolor  

Energy Technology Data Exchange (ETDEWEB)

In recent years, the environmental contamination by the harmful polluted chemicals becomes more serious. Among them, especially, the dioxins such as coplanar PCBs (Co-PCBs) and PCDDs are hard to be decomposed due to their stability and hydrophobic nature, leading to the world-wide contamination. To clean up the polluted environment, bioremediation using a microorganism is expected to solve the environmental pollution problem because of cost-effective alternative to the more established engineering method. There are some reports on the biodegradation of dioxins using various organisms, in which basidiomycetes, so-called white-rot fungi, have been extensively studied in the process of lignin degradation. As a result unique extracellular oxidative lignindegrading enzymes, such as lignin peroxidase, manganese-dependent peroxidase and laccase were supposed to be responsible for degrading dioxins. Overall many studies on biodegradation of dioxins or other chlorinated aromatic hydrocarbons have focused on using white-rot fungi; however, few reports referred to the metabolism of these environmental pollutants in the in vitro reaction by use of lignin-degrading enzymes produced by white-rot fungi. In this study, we reported the reduction of levels of Co-PCBs in the in vitro incubation with the fractions which had the oxidase activity toward 2, 2'-azinobis (3-ethylbenzothiazoline-6-sulfonate) (ABTS) in the culture fluid of white-rot fungus, Trametes versicolor.

Sonoki, S. [High-Tech Research Center, Azabu Univ., Kanagawa (Japan); Sue, T.; Hisamatsu, S. [Graduate School of Environmental Health, Azabu Univ., Kanagawa (Japan); Nagasaka, H. [Inst. of Environmental Ecology, Shin-Nippon Meteorological and Oceanographical Consultant Co., Ltd., Shizuoka (Japan)

2004-09-15

343

Free-radical chemistry of thiourea in aqueous solution, induced by OH radical, H atom, ?-hydroxyalkyl radicals, photoexcited maleimide, and the solvated electron  

International Nuclear Information System (INIS)

Hydroxyl radicals react with thiourea (and its tetramethyl derivative) yielding dimeric radical cations which are characterized by strong absorptions at 400 nm (450 nm). An analysis of the kinetics of the buildup of these absorptions gives evidence for the intermediacy of OH-adducts and the monomeric radical cations. The dimeric radical cations are also generated in the reactions of triplet-excited maleimide with those thioureas. Moreover, in acidic solutions even reducing radicals such as the H atom and ?-hydroxy alkyl radicals give rise to these intermediates in full yields, albeit displaying different kinetics. Potential mechanistic implications are discussed. The dimeric thiourea radical cations are strong oxidants and readily oxidize the anions of phenol and 2'-deoxyguanosine. The solvated electron gives rise to an intermediate which is rapidly protonated by water (pKa > 11). Quantum mechanical calculations support the assignment of the 400 nm (450 nm) absorption to the respective dimeric thiourea radical cation. (author)

344

Nanoencapsulation of ABT-737 and camptothecin enhances their clinical potential through synergistic antitumor effects and reduction of systemic toxicity.  

Science.gov (United States)

The simultaneous delivery of multiple cancer drugs in combination therapies to achieve optimal therapeutic effects in patients can be challenging. This study investigated whether co-encapsulation of the BH3-mimetic ABT-737 and the topoisomerase I inhibitor camptothecin (CPT) in PEGylated polymeric nanoparticles (NPs) was a viable strategy for overcoming their clinical limitations and to deliver both compounds at optimal ratios. We found that thrombocytopenia induced by exposure to ABT-737 was diminished through its encapsulation in NPs. Similarly, CPT-associated leukopenia and gastrointestinal toxicity were reduced compared with the administration of free CPT. In addition to the reduction of dose-limiting side effects, the co-encapsulation of both anticancer compounds in a single NP produced synergistic induction of apoptosis in both in vitro and in vivo colorectal cancer models. This strategy may widen the therapeutic window of these and other drugs and may enhance the clinical efficacy of synergistic drug combinations. PMID:25299779

Schmid, D; Jarvis, G E; Fay, F; Small, D M; Greene, M K; Majkut, J; Spence, S; McLaughlin, K M; McCloskey, K D; Johnston, P G; Kissenpfennig, A; Longley, D B; Scott, C J

2014-01-01

345

Oral and cutaneous thermosensory profile of selective TRPV1 inhibition by ABT-102 in a randomized healthy volunteer trial  

DEFF Research Database (Denmark)

The capsaicin receptor (TRPV1) antagonist ABT-102 demonstrates efficacy in multiple preclinical pain models. However, evolving clinical data for this compound class suggest potentially profound drug-induced thermosensory impairment. Safety and tolerability of ABT-102 were assessed in a multiple-dose, double-blind, placebo-controlled, randomized healthy volunteer trial. Thirty-six participants were randomized in a 2:1 ratio to ABT-102:placebo in 3 dose groups (1mg, 2mg, and 4mg twice a day) and confined to an inpatient research unit for a 7-day treatment period and 3 follow-up days. Outcome measures included: oral and cutaneous cold detection, warm detection (WDT), and heat pain thresholds (HPT); oral perceived heat intensity (oral liquid test); time to hand withdrawal (water bath test); and cutaneous pain intensity (long thermal stimulus). Significant dose-dependent (placebo- and baseline-adjusted) increases in HPT and reduced painfulness of suprathreshold heat were present from days 1-7. For ABT-102 4mg twice a day, model-based mean differences from placebo (95% confidence interval) were as follows: oral HPT, day 1=2.5°C (0.6-4.4), day 5=4.4°C (2.5-6.3); cutaneous HPT, day 2=3.3°C (1.4-5.3), day 5=5.3°C (3.3-7.2); oral WDT, day 1=2.6°C (0.5-4.7), day 5=2.7°C (0.6-4.9); cutaneous WDT, day 2=1.3 (0.0-2.6), day 5=1.6 (0.3-2.8) (all P

Rowbotham, Michael C; Nothaft, Wolfram

2011-01-01

346

Identification of Small Inhibitory Molecules Targeting the Bfl-1 Anti-Apoptotic Protein That Alleviates Resistance to ABT-737.  

Science.gov (United States)

One approach currently being developed in anticancer drug discovery is to search for small compounds capable of occupying and blocking the hydrophobic pocket of anti-apoptotic Bcl-2 family members necessary for interacting with pro-apoptotic proteins. Such an approach led to the discovery of several compounds, such as ABT-737 (which interacts with Bcl-2, Bcl-xl, and Bcl-w) or the latest one, ABT-199, that selectively targets Bcl-2 protein. The efficacy of those compounds is, however, limited by the expression of two other anti-apoptotic Bcl-2 members, Mcl-1 and Bfl-1. Based on the role of Bfl-1 in cancer, especially in chemoresistance associated with its overexpression in B-cell malignancies, we searched for modulators of protein-protein interaction through a high-throughput screening of a designed chemical library with relaxed drug-like properties to identify small molecules targeting Bfl-1 anti-apoptotic protein. We found two compounds that display electrophilic functions, interact with Bfl-1, inhibit Bfl-1 protective activity, and promote cell death of malignant B cells. Of particular interest, we observed a synergistic effect of those compounds with ABT-737 in Bfl-1 overexpressing lymphoma cell lines. Our results provide the basis for the development of Bfl-1 specific antagonists for antitumor therapies. PMID:24809353

Mathieu, Anne-Laure; Sperandio, Olivier; Pottiez, Virginie; Balzarin, Sophie; Herlédan, Adrien; Elkaïm, Judith O; Fogeron, Marie-Laure; Piveteau, Catherine; Dassonneville, Sandrine; Deprez, Benoit; Villoutreix, Bruno O; Bonnefoy, Nathalie; Leroux, Florence

2014-05-01

347

Pulse radiolysis and e.s.r. evidence for the formation of an alkene radical cation in aqueous solution  

International Nuclear Information System (INIS)

Direct pulse radiolysis evidence, complemented by e.s.r. experiments, establishes that the radical cation Me2C+-radical CMe2 is formed by acid-catalysed elimination of OH-from radical CMe2CMe2OH; the radical cation deprotonates to give radical CH2CMe=CMe2 with k 3.9 x 105 S-1. (author)

348

Emergence of oxyl radicals as selective oxidants.  

Science.gov (United States)

Hydroxyl radicals (HO*) are derived in Fenton reaction with ferrous salt and H2O2 in acid medium, and at neutral pH, metal-oxyl radicals (M-O*) predominate. Evidence is accumulating that M-O* radicals are also active in oxidation reactions, in addition to metal-oxo (M=O) now shown in many publications. Reactivity of these radicals gives selective oxidized products useful in cellular activities, in contrast to purported indiscriminate cell damage by hydroxyl radicals. Reactions with vanadium compounds, such as diperoxovanadate, peroxo-bridged mixed valency divanadate, vanadium-oxyl radical, tetravalent vanadyl and decavanadate illustrates selective gain in oxidative capacity of oxo- and oxyl- species. Occurrence of ESR signals typical of hydroxyl radicals is demonstrated in cell homogenates and tissue perfusates treated with spin trap agents. It is known for a long time lipid peroxides are formed in tissue microsomal systems exclusively in presence of salts of iron, among many metals tested. Oxygen and a reducing agent, ascorbate (non-enzymic) or NADPH (enzymic) are required to produce 'ferryl', the chelated Fe=O active form (possibly Fe-O* and Fe-O-O-Fe ?) for the crucial step of H-atom abstraction. Yet literature is replete with unsupported affirmations that hydroxyl radicals initiate lipid peroxidation, an unexplained fixation of mindset. The best-known *OH generator, a mixture of ferrous salt and H2O2, does not promote lipid peroxidation, nor do the many hydroxyl radical quenching agents stop it. The availability of oxo and oxyl-radical forms with transition metals, and also with non metals, P, S, N and V, calls for expansion of vision beyond superoxide and hydroxyl radicals and explore functions of multiple oxygen radicals for their biological relevance. PMID:23259316

Ramasarma, T

2012-10-01

349

Investigation of the role of protonation of benzophenone and its derivatives in acidic aqueous solutions using time-resolved resonance Raman spectroscopy: how are ketyl radicals formed in aqueous solutions?  

Science.gov (United States)

The formation mechanism of ketyl radicals and several other selective photoreactions of benzophenone and its derivatives are initiated by the protonation of their triplet state and have been investigated using nanosecond time-resolved resonance Raman spectroscopy (ns-TR(3)) in solutions of varying conditions. Evidence is found that the ketyl radical is generated by the combined action of a ketone protonation and a subsequent electron transfer based on the results from previous studies on the photochemistry and photophysics of benzophenone and the ns-TR(3) results reported here for benzophenone, 1,4-dibenzoylbenzene, 3-(hydroxymethyl)benzophenone, and ketoprofen in neutral and acidic solution. In order to better understand the role of the protonated ketone, results are summarized for some selective photochemical reactions of benzophenone and its derivatives induced by protonation in acidic solutions. For the parent benzophenone, the protonation of the ketone leads to the photohydration reactions at the ortho- and meta-positions of the benzene ring in acidic aqueous solutions. For 3-(hydroxymethyl)benzophenone, the protonation promotes an interesting photoredox reaction to become very efficient and the predominant reaction in a pH = 2 aqueous solution. While for ketoprofen, the protonation can initiate a solvent-mediated excited-state intramolecular proton transfer (ESIPT) from the carboxyl group to the carbonyl group that then leads to a decarboxylation reaction in a pH = 0 acidic aqueous solution. We briefly discuss the key role of the protonation of the ketone in the photochemistry of these aromatic ketones. PMID:25141023

Li, Ming-De; Huang, Jinqing; Liu, Mingyue; Li, Songbo; Ma, Jiani; Phillips, David Lee

2015-02-12

350

Effect of Bucillamine on Free-Radical-Mediated Degradation of High-Molar-Mass Hyaluronan Induced in vitro by Ascorbic Acid and Cu(II) Ions  

OpenAIRE

The bucillamine effect on free-radical-mediated degradation of high-molar-mass hyaluronan (HA) has been elucidated. As HA fragmentation is expected to decrease its dynamic viscosity, rotational viscometry was applied to follow the oxidative HA degradation. Non-isothermal chemiluminometry, thermogravimetry, differential scanning calorimetry, and size-exclusion chromatography (SEC) were applied to characterize resulting HA fragments. Although bucillamine completely inhibited the HA viscosity de...

Mária Ba?asová; Katarína Valachová; Jozef Rychlý; Ivica Janigová; Katarína Csomorová; Raniero Mendichi; Danica Mislovi?ová; Ivo Juránek; Ladislav Šoltés

2014-01-01

351

Identification of predictive factors of response to the BH3-mimetic molecule ABT-737: An ex vivo experiment in human serous ovarian carcinoma.  

Science.gov (United States)

Ovarian cancers are addicted to Bcl-xL and Mcl-1, antiapoptotic members of the Bcl-2 family. Bcl-xL can be inhibited by the BH3-mimetic ABT-737. In vitro, ABT-737 can induce apoptosis of cancer cells, and its activity is potentiated by Mcl-1 inactivation. Herein, we assessed the sensitivity of human ovarian tumor nodes to ABT-737 when combined with carboplatin, which can indirectly inhibit Mcl-1. Fresh samples from 25 patients with high-grade serous ovarian cancer (HGSOC) who were chemo-naïve and had undergone surgery were prospectively exposed ex vivo to ABT-737?±?carboplatin. The treatment effect was studied on sliced tumor nodes by assessment of cleaved-caspase 3 immunostaining. We also studied the association between baseline Bcl-2 family protein expression (via immunohistochemistry) and the response of nodes to treatment. ABT-737 induced apoptosis as a single agent but its efficacy was not improved by the addition of carboplatin. Bim was frequently expressed (20/25) and its absence or low expression was associated with the absence of response to ABT-737, p value?=?0.019 by Fisher's test and sensitivity?=?93%, (95% confidence interval, 66-100). Moreover, we observed that in tumors in which Bim was expressed, a low expression of phospho-Erk1/2 or Mcl-1 improved the proportion of responses. This pilot study showed that ABT-737 has promise as monotherapy for HGSOC in a specific subgroup of tumors. Bim, Mcl-1, and phospho-Erk1/2 appeared to be relevant biomarkers that could be used for the selection of patients in the design of clinical trials using Navitoclax (an orally available compound related to ABT-737). PMID:25066666

Lheureux, Stéphanie; N'Diaye, Monique; Blanc-Fournier, Cécile; Dugué, Audrey Emmanuelle; Clarisse, Bénédicte; Dutoit, Soizic; Giffard, Florence; Abeilard, Edwige; Briand, Mélanie; Labiche, Alexandre; Grellard, Jean-Michel; Crouet, Hubert; Martin, Sandrine; Joly, Florence; Poulain, Laurent

2015-03-01

352

ABT-737 reverses the acquired radioresistance of breast cancer cells by targeting Bcl-2 and Bcl-xL  

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Full Text Available Abstract Background Acquired radioresistance of cancer cells remains a fundamental barrier to attaining the maximal efficacy of radiotherapy for the treatment of breast cancer. Anti-apoptotic proteins, such as Bcl-2 and Bcl-xL, play an important role in the radioresistance of cancer cells. In the present study, we aimed to determine if ABT-737, a BH3-only mimic, could reverse the acquired radioresistance of the breast cancer cell line MDA-MB-231R by targeting Bcl-2 and Bcl-xL. Methods The radiosensitivity of MDA-MB-231 and MDA-MB-231R cells was compared using colony formation assays. Reverse-transcription PCR and western blot were performed to detect the expression of Bcl-2 and Bcl-xL in the cancer cell lines. Annexin V flow cytometric analysis and caspase-3 colorimetric assay were used to evaluate apoptosis of the cancer cells. Cell viability was measured using the Cell Counting Kit-8. The animals used in this study were 4 to 6-week-old athymic female BALB/c nu/nu mice. Results The MDA-MB-231R cells were more radioresistant than the MDA-MB-231 cells, and Bcl-2 and Bcl-xL were overexpressed in the MDA-MB-231R cells. While ABT-737 was able to restore the radiosensitivity of the MDA-MB-231R cells in vitro and in vivo experiment, it was not able to enhance the radiosensitivity of the MDA-MB-231 cells. In addition, ABT-737 increased radiation-induced apoptosis in the MDA-MB-231R cells. Bcl-2 and Bcl-xL were down regulated in the MDA-MB-231R cells following treatment with ABT-737. Conclusions Targeting of the anti-apoptotic proteins Bcl-2 and Bcl-xL with ABT-737 may reverse the acquired radioresistance of MDA-MB-231R cells in vitro and in vivo. These findings suggest an attractive strategy for overcoming the acquired radioresistance of breast cancer cells.

Li Ji-Yu

2012-12-01

353

Chemotherapeutic drugs sensitize human renal cell carcinoma cells to ABT-737 by a mechanism involving the Noxa-dependent inactivation of Mcl-1 or A1  

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Full Text Available Abstract Background Human renal cell carcinoma (RCC is very resistant to chemotherapy. ABT-737 is a novel inhibitor of anti-apoptotic proteins of the Bcl-2 family that has shown promise in various preclinical tumour models. Results We here report a strong over-additive pro-apoptotic effect of ABT-737 and etoposide, vinblastine or paclitaxel but not 5-fluorouracil in cell lines from human RCC. ABT-737 showed very little activity as a single agent but killed RCC cells potently when anti-apoptotic Mcl-1 or, unexpectedly, A1 was targeted by RNAi. This potent augmentation required endogenous Noxa protein since RNAi directed against Noxa but not against Bim or Puma reduced apoptosis induction by the combination of ABT-737 and etoposide or vinblastine. At the level of mitochondria, etoposide-treatment had a similar sensitizing activity and allowed for ABT-737-induced release of cytochrome c. Conclusions Chemotherapeutic drugs can overcome protection afforded by Mcl-1 and A1 through endogenous Noxa protein in RCC cells, and the combination of such drugs with ABT-737 may be a promising strategy in RCC. Strikingly, A1 emerged in RCC cell lines as a protein of similar importance as the well-established Mcl-1 in protection against apoptosis in these cells.

Zantl Niko

2010-06-01

354

Contemporary Radical Prostatectomy  

OpenAIRE

Purpose. Patients diagnosed with clinically localized prostate cancer have more surgical treatment options than in the past. This paper focuses on the procedures' oncological or functional outcomes and perioperative morbidities of radical retropubic prostatectomy, radical perineal prostatectomy, and robotic-assisted laparoscopic radical prostatectomy. Materials and Methods. A MEDLINE/PubMed search of the literature on radical prostatectomy and other new management options was performed. Resul...

Leon Sun; Qiang Fu; Moul, Judd W.

2011-01-01

355

Inhibition of Lipid Oxidation by MRP Antioxidant in Enriched Cooked Beef Patties with Polyunsaturated Fatty Acids  

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Full Text Available The addition of n3 polyunsaturated fatty acids to foods is an emerging area of commercial and academic interest. However, the incorporation of n3 polyunsaturated fatty acids into food systems is potentially problematic due to their propensity to oxidize easily. The antioxidant capacity of MRP has mostly been studied in vitro, in fresh chicken, mutton and pork, and in precooked ground pork and beef patties and sausages. The aim of this study is to evaluate the antioxidant properties as well as the antioxidant effect of a preformed Maillard Reaction Product (MRP from sarcoplasmic proteins/malondialdehyde, known for its antioxidant effect on water/oil emulsion and on lipid oxidation of beef patties when the level of n3 PUFA is improved. The MRP presented a high reducing power, a low phenolic compound content (9.2 mg gallic acid equivalent/g and 798.3 mg quercetin equivalent/g, and a minor DPPH and ABTS+ radicals scavenging activity (34 % and 23,5 %, respectively. All concentrations of MRP assayed inhibited hydroperoxide formation and thiobarbituric acid reactive substances (TBARS production during refrigerated storage of enriched meat patties. The 3% concentration was the most efficient and exerted an 83 % and 85 % inhibition of peroxidation measured as peroxide value and TBARS, respectively.

Carina Lorena Fernandez

2012-05-01

356

Chemical modification of lysozyme, glucose 6-phosphate dehydrogenase, and bovine eye lens proteins induced by peroxyl radicals: role of oxidizable amino acid residues.  

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Chemical and structural alterations to lysozyme (LYSO), glucose 6-phosphate dehydrogenase (G6PD), and bovine eye lens proteins (BLP) promoted by peroxyl radicals generated by the thermal decomposition of 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH) under aerobic conditions were investigated. SDS-PAGE analysis of the AAPH-treated proteins revealed the occurrence of protein aggregation, cross-linking, and fragmentation; BLP, which are naturally organized in globular assemblies, were the most affected proteins. Transmission electron microscopy (TEM) analysis of BLP shows the formation of complex protein aggregates after treatment with AAPH. These structural modifications were accompanied by the formation of protein carbonyl groups and protein hydroperoxides. The yield of carbonyls was lower than that for protein hydroperoxide generation and was unrelated to protein fragmentation. The oxidized proteins were also characterized by significant oxidation of Met, Trp, and Tyr (but not other) residues, and low levels of dityrosine. As the dityrosine yield is too low to account for the observed cross-linking, we propose that aggregation is associated with tryptophan oxidation and Trp-derived cross-links. It is also proposed that Trp oxidation products play a fundamental role in nonrandom fragmentation and carbonyl group formation particularly for LYSO and G6PD. These data point to a complex mechanism of peroxyl-radical mediated modification of proteins with monomeric (LYSO), dimeric (G6PD), and multimeric (BLP) structural organization, which not only results in oxidation of protein side chains but also gives rise to radical-mediated protein cross-links and fragmentation, with Trp species being critical intermediates. PMID:23252580

Arenas, Andrea; López-Alarcón, Camilo; Kogan, Marcelo; Lissi, Eduardo; Davies, Michael J; Silva, Eduardo

2013-01-18

357

Discrepancies between the rate constants for the reactions of hydroxyl radicals with ferrocenyl-substituted carboxylic acids determined by direct measurement and by competition with thiocyanate-ion  

International Nuclear Information System (INIS)

The rate constants for the reaction of OH radical with 3-ferrocenyl-propanoate and 2-ferrocenyl-ethanoate have been determined using competition with thiocyanate ion. However, the corrections involved in these determinations were large, ranging up to 38.5%, and we have, therefore, considered it necessary to attempt the direct measurement of these rate constants by pulse radiolysis. In this communication we report these direct measurements of the rate constants for these reactions and compare the values so obtained with those determined by competition with thiocyanate ion. We also report similar measurements for the reaction of OH with ferrocenylformate. (author)

358

Reactions of melatonin with radicals in deoxygenated aqueous solution  

International Nuclear Information System (INIS)

Reactions of melatonin (N-acetyl-5-methoxytryptamine) with radiolytically generated radicals were studied. Reaction of melatonin with OH radicals is diffusion-controlled (k=1.2 x 1010 dm3 mol-1 x s-1), the main (but not the only one) intermediate being the indolyl-type radical, while the rate constant for the reaction with hydrated electrons is k=4.3 x 108 dm3 x mol-1 x s-1. Melatonin is capable of scavenging tert-butanol radicals, while its reactivity towards polymer radicals of poly(acrylic acid) and poly(vinyl pyrrolidone) is very low. (author)

359

CHARACTERIZATION OF FATTY ACID PROFILE, POLYPHENOLIC CONTENT AND ANTIOXIDANT ACTIVITY OF COLD PRESSED AND REFINED EDIBLE OILS FROM MACEDONIA  

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Full Text Available Fatty acid profile, polyphenolic content and resulting antioxidant activity of the most consumed edible oils on Macedonian market were studied. The levels of total polyphenolics were estimated spectrophotometically by extraction with 60 % aqueous methanol using Folin-Ciocalteau reagent. A common method for determination of the antioxidant activity of edible oils is the 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid radical cation (ABTS•+ method. This method was used for testing the oils (six cold pressed oils from olive, sunflower, pumpkin, rapeseed, flaxseed and four commercial refined sunflower oils available on Macedonian market. The levels of total polyphenolic of cold pressed oils were in the range from 1.82 to 34.21 mg per 10 g of oil and corresponding antioxidant activity from 0.01 to 4.12 expressed as mmol Trolox per liter of oil. Furthermore, GC-MS analyses were performed for determination of fatty acid profile of the oils. The percentage of 9, 12 linoleinic acid was predominant in comparison with other fatty acids in examined oils.

Saša Mitrev

2013-06-01

360

Structural and medium effects on the reactions of the cumyloxyl radical with intramolecular hydrogen bonded phenols. The interplay between hydrogen-bonding and acid-base interactions on the hydrogen atom transfer reactivity and selectivity.  

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A time-resolved kinetic study on the reactions of the cumyloxyl radical (CumO(•)) with intramolecularly hydrogen bonded 2-(1-piperidinylmethyl)phenol (1) and 4-methoxy-2-(1-piperidinylmethyl)phenol (2) and with 4-methoxy-3-(1-piperidinylmethyl)phenol (3) has been carried out. In acetonitrile, intramolecular hydrogen bonding protects the phenolic O-H of 1 and 2 from attack by CumO(•) and hydrogen atom transfer (HAT) exclusively occurs from the C-H bonds that are ? to the piperidine nitrogen (?-C-H bonds). With 3 HAT from both the phenolic O-H and the ?-C-H bonds is observed. In the presence of TFA or Mg(ClO4)2, protonation or Mg(2+) complexation of the piperidine nitrogen removes the intramolecular hydrogen bond in 1 and 2 and strongly deactivates the ?-C-H bonds of the three substrates. Under these conditions, HAT to CumO(•) exclusively occurs from the phenolic O-H group of 1-3. These results clearly show that in these systems the interplay between intramolecular hydrogen bonding and Brønsted and Lewis acid-base interactions can drastically influence both the HAT reactivity and selectivity. The possible implications of these findings are discussed in the framework of the important role played by tyrosyl radicals in biological systems. PMID:24892501

Salamone, Michela; Amorati, Riccardo; Menichetti, Stefano; Viglianisi, Caterina; Bietti, Massimo

2014-07-01

361

Characterization of pH-responsive hydrogels of poly(itaconic acid-g-ethylene glycol) prepared by UV-initiated free radical polymerization as biomaterials for oral delivery of bioactive agents.  

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Effective oral delivery of proteins is impeded by steep pH gradients and proteolytic enzymes in the gastrointestinal tract, as well as low absorption of the proteins into the bloodstream because of their size, charge, or solubility. In this work, pH-responsive complexation hydrogels of poly(itaconic acid) (PIA) with poly(ethylene glycol) (PEG) grafts were synthesized for applications in oral drug delivery. These hydrogels were expected to be in collapsed configuration at low pH because of hydrogen bonding between PIA carboxyl groups and PEG, and to swell with increasing pH because of charge repulsion between deprotonated carboxylic acid groups. Hydrogels were prepared by UV-initiated free radical polymerization using tetraethylene glycol as the crosslinking agent and Irgacure 2959 as the initiator. The effect of monomer ratios, crosslinking ratio, and solvent amount on the properties of the hydrogels were investigated. The composition of the hydrogels was confirmed by Fourier transform infrared spectroscopy. Equilibrium swelling studies in the pH range of 1.2-7 revealed that the extent of swelling increased with increasing pH up to a pH of about 6, when no further carboxylic acid deprotonation occurred. Studies in Caco-2 colorectal carcinoma cells confirmed the cytocompatibility of these materials at concentrations of up to 5 mg/mL. PMID:19536838

Betancourt, Tania; Pardo, Juan; Soo, Ken; Peppas, Nicholas A

2010-04-01

362

Effect of Bucillamine on Free-Radical-Mediated Degradation of High-Molar-Mass Hyaluronan Induced in vitro by Ascorbic Acid and Cu(II Ions  

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Full Text Available The bucillamine effect on free-radical-mediated degradation of high-molar-mass hyaluronan (HA has been elucidated. As HA fragmentation is expected to decrease its dynamic viscosity, rotational viscometry was applied to follow the oxidative HA degradation. Non-isothermal chemiluminometry, thermogravimetry, differential scanning calorimetry, and size-exclusion chromatography (SEC were applied to characterize resulting HA fragments. Although bucillamine completely inhibited the HA viscosity decrease caused by oxidative system, indicating HA protection from degradation, SEC analysis suggested that some other mechanisms leading to the bucillamine transformations without the decay of the viscosity may come into a play as well. Nonetheless, the link between the reduction of chemiluminescence intensity and disappearance of the differential scanning calorimetry exotherm at 270 °C for fragmented HAs indicates a particular role of the bucillamine in preventing the decrease of HA viscosity.

Mária Ba?asová

2014-10-01

363

Cascade Dissociations of Peptide Cation-Radicals. Part 1. Scope and Effects of Amino Acid Residues in Penta-, Nona- and Decapeptides  

OpenAIRE

Amino acid residue-specific backbone and side-chain dissociations of peptide z ions in MS3 spectra were elucidated for over 40 pentapeptides with arginine C-terminated sequences of the AAXAR and AAHXR type, nonapeptides of the AAHAAXYAR and AAHAXAYAR type, and AAHAAXYAAR decapeptides. Peptide zn ions containing amino acid residues with readily transferrable benzylic or tertiary ?-hydrogen atoms (Phe, Tyr, His, Trp, Val) underwent facile backbone cleavages to form dominant zn-2 or zn-3 ions. ...

Chung, Thomas W.; Hui, Renjie; Ledvina, Aaron; Coon, Joshua J.; Turecek, Frantisek

2012-01-01

364

Preparation and study of dialkyl nitroxide radicals  

International Nuclear Information System (INIS)

These radicals are obtained by oxidation of N-hydroxy-imides with lead tetracetate or p-nitro-perbenzoic acid. These imides are prepared by heating dicarboxylic acids anhydrides with benzyloxy-amine followed by catalytic hydrogenation of N-benzyloxy-imides so obtained. Two series of radicals have mainly been studied, the first concerning five-membered cyclic imides, the second six-membered cyclic imides, these molecules having methyls substituents or no on the carbon ring. N. M. R. spectra of some O-benzyl-imides have been analysed. These different results have made it possible to study the conformation and stereochemistry of these imides. (author)

365

Reactions of alkoxy radicals in aqueous solutions  

International Nuclear Information System (INIS)

The kinetic and mechanistic properties of alkoxy radicals in organic solvents are briefly reviewed. Owing to the scarcity of such data in aqueous solutions and since reactions at the membrane/water interface may be also biologically important, we have studied the reactivity of these radicals in water and the results of our investigations are reported. Alkoxy radicals were generated by photolytic or radiolytic cleavage of peroxide precursors (tert-butyl hydroperoxide and di-tert-butyl peroxide as well as hydroperoxides of polyunsaturated fatty acids). A quantitative correlation between the structure of various substances, in particular, phenolic antioxidants, and their activity in inhibiting the alkoxy radical-induced bleaching of the water-soluble carotenoid crocin will be discussed. Rate constants for intermolecular reactions of t-BuO. radicals were determined by pulse radiolysis. The diffusion-controlled reaction with the catechol antioxidant nordihydroguaiaretic acid demonstrates an effective competition with the very rapid intra molecular ?-fragmentation in water. The results aupport the view that a considerable amount of alkoxy radicals interact with substrates before they can rearrange intramolecularly

366

Reactions of alkoxy radicals in aqueous solutions  

Energy Technology Data Exchange (ETDEWEB)

The kinetic and mechanistic properties of alkoxy radicals in organic solvents are briefly reviewed. Owing to the scarcity of such data in aqueous solutions and since reactions at the membrane/water interface may be also biologically important, we have studied the reactivity of these radicals in water and the results of our investigations are reported. Alkoxy radicals were generated by photolytic or radiolytic cleavage of peroxide precursors (tert-butyl hydroperoxide and di-tert-butyl peroxide as well as hydroperoxides of polyunsaturated fatty acids). A quantitative correlation between the structure of various substances, in particular, phenolic antioxidants, and their activity in inhibiting the alkoxy radical-induced bleaching of the water-soluble carotenoid crocin will be discussed. Rate constants for intermolecular reactions of t-BuO. radicals were determined by pulse radiolysis. The diffusion-controlled reaction with the catechol antioxidant nordihydroguaiaretic acid demonstrates an effective competition with the very rapid intra molecular ..beta..-fragmentation in water. The results aupport the view that a considerable amount of alkoxy radicals interact with substrates before they can rearrange intramolecularly.

Bors, W.; Tait, D.; Michel, C.; Saran, M.; Erben-Russ, M. (Gesellschaft fuer Strahlen- und Umweltforschung m.b.H. Muenchen, Neuherberg (Germany, F.R.). Abt. fuer Strahlenbiologie)

1984-01-01

367

Reactivity of neonicotinoid insecticides with carbonate radicals.  

Science.gov (United States)

The reaction of three chloronicotinoid insecticides, namely Imidacloprid (IMD), Thiacloprid (THIA) and Acetamiprid (ACT), with carbonate radicals (CO·??) was investigated. The second order rate constants (4 ± 1) × 10?, (2.8 ± 0.5) × 10?, and (1.5 ± 1) × 10? M?¹ s?¹ were determined for IMD, THIA and ACT, respectively. The absorption spectra of the organic intermediates formed after CO·?? attack to IMD is in line with those reported for ?-aminoalkyl radicals. A reaction mechanism involving an initial charge transfer from the amidine nitrogen of the insecticides to CO·?? is proposed and further supported by the identified reaction products. The pyridine moiety of the insecticides remains unaffected until nicotinic acid is formed. CO·?? radical reactivity towards IMD, ACT, and THIA is low compared to that of HO• radicals, excited triplet states, and ¹O?, and is therefore little effective in depleting neonicotinoid insecticides. PMID:22542132

Dell'Arciprete, María Laura; Soler, Juán M; Santos-Juanes, Lucas; Arques, Antonio; Mártire, Daniel O; Furlong, Jorge P; Gonzalez, Mónica C

2012-07-01

368

Phenyl Radical-Induced Damage to Dipeptides  

Science.gov (United States)

Laser-induced acoustic desorption (LIAD) incorporated with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR) has been utilized to investigate phenyl radical-induced damage to dipeptides in the gas phase. Based on the product branching ratios measured for the reactions of two different positively-charged phenyl radicals with seventeen different dipeptides, the overall order of susceptibility to attack of the different sites in the dipeptides was determined to be: heteroaromatic side chain ? S atom in SCH3 group > H atom in SH group > H atom in CH group > aromatic side chain > S atom in SH group > NH2 in side chain > N-terminal NH2 > COOH in side chain ? C-terminal COOH. The amino acid sequence also influences the selectivity of these reactions. As expected, the ability of a phenyl radical to damage dipeptides increases as the electrophilicity of the phenyl radical increases. PMID:19772324

Li, Sen; Fu, Mingkun; Habicht, Steven C.; Pates, George O.; Nash, John J.; Kenttämaa, Hilkka I.

2009-01-01

369

Forgotten Radicals in Biology  

OpenAIRE

Redox reactions play key roles in intra- and inter-cellular signaling, and in adaptative processes of tissues towards stress. Among the major free radicals with essential functions in cells are reactive oxygen species (ROS) including superoxide anion (O2•-), hydroxyl radical (•OH) and reactive nitrogen species (RNS) such as nitric oxide (•NO). In this article, we review the forgotten and new radicals with potential relevance to cardiovascular pathophysiology. Approximately 0.3% of O2•...

Luc, Rochette; Vergely, Catherine

2008-01-01

370

Radicals from the reaction of photochemically generated a hydroxyalkyl radicals with some imidazoles: an in situ ESR study  

Energy Technology Data Exchange (ETDEWEB)

ESR spectra of short-lived radicals made by photolysis at room temperature of acidic alcoholic solutions of imidazole, 1-methylimidazole, and 4(5)-methylimidazole containing acetone or hydrogen peroxide have been studied. The ESR spectra are attributed to ..pi..-radicals formed by the addition of photochemically produced ..cap alpha..-hydroxyalkyl radicals on the C-2 position of the imidazolium cations. The hyperfine coupling constants are compared with values obtained from Hueckel and INDO MO calculations.

Dohrmann, J.K.; Krohn, H.

1979-02-01

371

Oxidation of SO2 by stabilized Criegee Intermediate (sCI radicals as a crucial source for atmospheric sulphuric acid concentrations  

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Full Text Available The effect of increased reaction rates of stabilised Criegee Intermediates (sCI with SO2 to produce sulphuric acid is investigated using data from two different locations, SMEAR II, Hyytiälä, Finland and Hohenpeissenberg, Germany. Results from MALTE, a zero dimensional model, show that using previous values for the rate coefficients of sCI + SO2, the model underestimates gas phase H2SO4 by up to a factor of two when compared to measurements. Using the rate coefficients recently calculated by Mauldin et al. (2012 increases sulphuric acid by 30–40%. Increasing the rate coefficient for formaldehyde oxide (CH2OO with SO2 by a factor of ten further increases the H2SO4 yield by 16%. Taken together, these increases lead to the conclusion that, depending on their concentrations, the reaction of stabilized Criegee intermediates with SO2 could contribute as much as 50% to atmospheric sulphuric acid gas phase concentrations at ground level. Using the SMEAR II data, results from SOSA, a one-dimensional model, show that contribution from sCI reactions to sulphuric acid production is most important in the canopy where the concentration of organic compounds are the highest, but can have significant effects on sulphuric acid concentrations up to 100 m. The recent findings that the reaction of sCI + SO2 is much faster than previously thought together with these results show that the inclusion of this new oxidation mechanism is crucial in regional, as well as, global models.

L. Mauldin

2012-10-01

372

Oxidation of SO2 by stabilized Criegee intermediate (sCI radicals as a crucial source for atmospheric sulfuric acid concentrations  

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Full Text Available The effect of increased reaction rates of stabilized Criegee intermediates (sCIs with SO2 to produce sulfuric acid is investigated using data from two different locations, SMEAR II, Hyytiälä, Finland, and Hohenpeissenberg, Germany. Results from MALTE, a zero-dimensional model, show that using previous values for the rate coefficients of sCI + SO2, the model underestimates gas phase H2SO4 by up to a factor of two when compared to measurements. Using the rate coefficients recently calculated by Mauldin et al. (2012 increases sulfuric acid by 30–40%. Increasing the rate coefficient for formaldehyde oxide (CH2OO with SO2 according to the values recommended by Welz et al. (2012 increases the H2SO4 yield by 3–6%. Taken together, these increases lead to the conclusion that, depending on their concentrations, the reaction of stabilized Criegee intermediates with SO2 could contribute as much as 33–46% to atmospheric sulfuric acid gas phase concentrations at ground level. Using the SMEAR II data, results from SOSA, a one-dimensional model, show that the contribution from sCI reactions to sulfuric acid production is most important in the canopy, where the concentrations of organic compounds are the highest, but can have significant effects on sulfuric acid concentrations up to 100 m. The recent findings that the reaction of sCI + SO2 is much faster than previously thought together with these results show that the inclusion of this new oxidation mechanism could be crucial in regional as well as global models.

M. Boy

2013-04-01

373

Radiation damage to histone H2A by the primary aqueous radicals  

International Nuclear Information System (INIS)

Histone H2A has been examined for radiation-induced changes in structure and in amino acid composition. The effects of the individual radical intermediates--the hydroxyl radical, solvated electron, and superoxide radical--have been determined by irradiating in dilute aqueous solution under controlled environmental conditions. Amino acid analysis of irradiated histone H2A shows a selective attack on a few residues; only the aromatic residues, phenylalanine and tyrosine, and the heterocyclic residue, histidine, are significantly decreased. A significant increase in aspartic acid is also observed. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis shows that the hydroxyl radical is the effective radical for promoting changes in protein structure

374

DFT study of the effect of solvent on the H-atom transfer involved in the scavenging of the free radicals (·)HO2 and (·)O2(-) by caffeic acid phenethyl ester and some of its derivatives.  

Science.gov (United States)

H-atom transfer from caffeic acid phenethyl ester (CAPE), MBC (3-methyl-2-butenyl caffeate), BC (benzoic caffeate), P3HC (phenethyl-3-hydroxycinnamate), and P4HC (phenethyl-4-hydroxycinnamate) to the selected free radicals (·)HO2 and (·)O2(-) was studied. Such a transfer can proceed in three different ways: concerted proton-coupled electron transfer (CPCET), electron transfer followed by proton transfer (ET-PT), and proton transfer followed by electron transfer (PT-ET). The latter pathway is sometimes competitive with SPLET (sequential proton loss electron transfer) in polar media. Analyzing the thermodynamic descriptors of the reactions of CAPE and its derivatives with co-reactive species-in particular, the free energies of reactions, the activation barrier to the CPCET mechanism, and their rate constants-appears to be the most realistic method of investigating the H-atom transfers of interest. These analyses were performed via DFT calculations, which agree well with the data acquired from experimental studies (IC50) and from CBS calculations. The CPCM solvation model was used throughout the work, while the SMD model-employed as a reference-was used only for CAPE. The main conclusion drawn from the analysis was that SPLET is the mechanism that governs the reaction of phenolic acids with (·)HO2, while PT-ET governs the reaction of phenols with (·)O2(-). In kinetic investigations of the CPCET process, the rate constant decreases as the solvent polarity increases, so the reaction velocity slows down. PMID:25388279

Holtomo, Olivier; Nsangou, Mama; Fifen, Jean Jules; Motapon, Ousmanou

2014-11-01

375

Bcl2L12 with a BH3-like domain in regulating apoptosis and TMZ-induced autophagy: A prospective combination of ABT-737 and TMZ for treating glioma.  

Science.gov (United States)

Bcl2L12 as a new member of the Bcl2 family, which contains a BH2 domain and shares a lower amino acid similarity with other Bcl2 family proteins. Bcl2L12 is reported to be involved in apoptosis regulation, but this role remains controversial in different cancer type. Temozolomide (TMZ) is currently used to intervene glioma multiforme (GBM), but an acquired chemotherapeutic resistance maybe occurred due to undesired autophagy. Previous studies uncovered that Bcl2L12 may interact with Bcl-xL and may harbor a BH3-like domain. Therefore, we investigated whether this BH3-like domain is responsible for the Bcl2L12 anti-apoptotic property. Moreover, we tested whether ABT-737, a BH3 mimetic agent, can be combined with TMZ to treat GBM. We aligned Bcl2L12 with Bcl2 family members, compared interacting pattern of BH3 domain and their protein 3D structure. We identified that Bcl2L12 interacts with Bcl-xL and Bcl2 in yeast two-hybrid system. Bcl2L12192-220 was a minimal region for Bcl2L12-Bcl-xL interaction. Five-point mutations with respect to hydrophobic and charge residues were generated to test whether they are the key residue of BH3-like domain. Our data showed that both h1 (L213) and h2 residue (L217) are essential for Bcl2L12 interacting with Bcl2 family proteins. Ectopically expressed h1 or h2 mutant in U87MG cell line resulted in reactivation of cleaved-PARP, caspase-3 and cytochrome c releasing compared to Bcl2L12 wt group. Implementing ABT-737 combined with TMZ provided a superior effect on apoptosis induction in Bcl2L12 wt group, which effectively reactivated apoptotic markers. Altogether, our findings indicated that Bcl2L12 retains a BH3-like domain, which is important for the Bcl2L12 anti-apoptotic property and TMZ-induced autophagy. Our results basically support the idea of using ABT-737 to counteract the anti-apoptotic role of Bcl2L12 and sensitize drug response of the GBM cells to TMZ. PMID:25586056

Yang, Ming-Chang; Loh, Joon-Khim; Li, Yi-Yang; Huang, Wen-Sheng; Chou, Chia-Hua; Cheng, Jiin-Tsuey; Wang, Yeng-Tseng; Lieu, Ann-Shung; Howng, Shen-Long; Hong, Yi-Ren; Chou, An-Kuo

2015-03-01

376

Influence of protonation on the stability of disulfide radicals  

International Nuclear Information System (INIS)

The ease of disulfide bond cleavage in peptide and proteins is evaluated by an experimental method (one-electron reduction by COO.- radicals and measurement of the chain length) and two theoretical approaches based on quantum chemistry and topology. All results agree to show acid-catalysis of this bond opening. The disulfide bond in the radical state is weakened by protonation. (author)

377

Crotylations of alpha-carbonyl radicals with crotylstannane.  

Science.gov (United States)

Electrophilic radicals undergo crotylation with crotylstannane with moderate to good efficiency. The reaction provides the syn isomer as the major product. The present methodology is complementary to Claisen protocols for the synthesis of gamma,delta-unsaturated carboxylic acid derivatives. Details of the new radical methodology are presented. [reaction: see text] PMID:12323037

Sibi, Mukund P; Miyabe, Hideto

2002-10-01

378

Tin-free enantioselective radical reactions using silanes.  

Science.gov (United States)

Readily available hexyl silane is an excellent choice as a H-atom donor and a chain carrier in Lewis acid mediated enantioselective radical reactions. Conjugate radical additions to alpha,beta-unsaturated imides at room temperature proceed in good yields and excellent enantioselectivities. PMID:18986157

Sibi, Mukund P; Yang, Yong-Hua; Lee, Sunggi

2008-12-01

379

Cistectomía radical robótica / Robotic radical cystectomy  

Scientific Electronic Library Online (English)

Full Text Available SciELO Spain | Language: Spanish Abstract in spanish Objetivos: En la última década hemos visto un tremendo crecimiento en la implantacion y desarrollo de los robots quirúrgicos. Popularizados por la prostatectomía radical, las técnicas robóticas están siendo, en la actualidad, muy aplicadas en la cistectomía radical. Trataremos aquí de revisar el des [...] arrollo y estado actual de la cistectomía radical robótica (CRR) en la práctica contemporánea de la urología. Métodos: Se ha revisado toda la literatura publicada, entre 1995 y 2007, en la base de datos de la Biblioteca Nacional de Medicina (MEDLINE) utilizando las palabras clave: robótica, asistido por robot, laparoscópica y cistectomía. Desde el primer trabajo en 2003, se han encontrado 9 originales publicados. Se valoraron con respecto a la técnica, ventajas y desventajas perioperatorias y resultados oncológicos. Describimos asimismo nuestra experiencia inicial, aún no publicada. Resultados: En este momento todos los artículos publicados sobre la CRR se basan en un número pequeño de pacientes con seguimientos a corto plazo. No obstante, demuestran la viabilidad de la CRR con resultados perioperatorios esperanzadores. Comparada con la cistectomía radical abierta (CRA), la CRR parece estar asociada con menor pérdida de sangre, estancia hospitalaria y necesidades analgésicas. Estas ventajas se encuentran asimismo en la cistectomía radical laparoscópica (CRL) y son una función del abordaje mínimamente invasivo. El tiempo quirúrgico es mayor, de forma considerable cuando el tiempo intestinal se realiza de manera intracorpórea. Conclusiones: La cistectomía radical robótica está en evolución. La viabilidad técnica ha sido demostrada. Los resultados perioperatorios iniciales son prometedores. Los resultados oncológicos esperan identificar el papel de la misma en el manejo del cáncer de vejiga. Se necesitan ensayos prospectivos y aleatorizados comparando la CRA con la CRR y la CRL. Abstract in english Objectives: The last decade has seen tremendous growth of surgical robotics. Popularized for radical prostatectomy, robotic techniques are now increasingly being applied to radical cystectomy. Herein, we review the development and current status of robotic radical cystectomy (RRC) in contemporary ur [...] ological practice. Methods: Between 1995 and 2007 published literature was reviewed using the National Library of Medicine database and the following key words: robotic, robot-assisted, laparoscopic and cystectomy. Since the first report in 2003, nine published original reports were identified. These were evaluated with regards to the technique, advantages and disadvantages, perioperative and oncological outcomes. Our initial experience, as yet unpublished, is also described. Results: At this writing, all published papers on RRC are based on small number of patients with short-term follow-up. Nevertheless, they have demonstrated the technical feasibility of RRC with encouraging perioperative outcomes. Compared to open radical cystectomy (ORC), RRC appears to be associated with decreased blood loss, hospital stay and analgesic requirement. These advantages are also found with laparoscopic radical cystectomy (LRC) and are a function of the minimally invasive approach. The operating time is longer, markedly so when the bowel work is performed intracorporeally. Conclusions: RRC is in evolution. Technical feasibility has been demonstrated. Initial perioperative outcomes are encouraging. Oncological outcomes are awaited to identify the role of RRC in the management of bladder cancer. Multi-center prospective randomized trials comparing ORC with RRC and LRC are necessary.

Burak, Turna; Monish, Aron; Georges-Pascal, Haber; Inderbir S., Gill; Jihad H., Kaouk.

2007-05-01

380

Myeloperoxidase inhibitory and radical scavenging activities of flavones from Pterogyne nitens.  

Science.gov (United States)

Two new flavone glucosides, nitensosides A and B (1, 2), together with four known compounds, sorbifolin (3), sorbifolin 6-O-beta-glucopyranoside (4), pedalitin (5), and pedalitin 6-O-beta-glucopyranoside (6) were isolated from Pterogyne nitens. Their structures were elucidated from 1D and 2D NMR analysis, as well as by high resolution mass spectrometry. All the isolated flavones were evaluated for their myeloperoxidase (MPO) inhibitory activity. The most active compound, pedalitin, exhibited IC50 value of 3.75 nM on MPO. Additionally, the radical-scavenging capacity of flavones 1-6 was evaluated towards ABTS and DPPH radicals and compared to standard compounds quercetin and Trolox. PMID:18451567

Fernandes, Daniara Cristina; Regasini, Luis Octávio; Vellosa, José Carlos Rebuglio; Pauletti, Patrícia Mendonça; Castro-Gamboa, Ian; Bolzani, Vanderlan Silva; Oliveira, Olga Maria Mascarenhas; Silva, Dulce Helena Siqueira

2008-05-01

381

Radical reactions in aqueous disulphide-thiol systems  

International Nuclear Information System (INIS)

Absolute rate constants have been measured for the reaction of (CH3SSCH3)cation radical and sulphur centred radical cations of lipoic acid, lip (SS)cation radical, with various thiols including penicillamine, cysteamine and cysteine. Under pulse radiolysis conditions no reaction was observed between the disulphide radical cations and the neutral thiols, RSH, i.e. k7 M-1 s-1. Rate constants in the order of 109 M-1 s-1, i.e. close to the diffusion controlled limit, were, however, found for the corresponding reactions with the thiolates, RS-. In systems containing lipoate and cysteamine the lip(SS)cation radical induced oxidation of CyaS- proceeds via CyaSradical, (CyaS...SCya)- and lip(S...S)- as intermediates, i.e. results in a cysteamine mediated conversion of an oxidizing lip(SS) radical cation to a reducing lip((S...S) radical anion along the reaction route. In other cases the reaction of disulphide radical cations with thiolate anions was found to proceed via an optically absorbing transient (lambdasub(max)approx.=380nm) which is suggested to be an adduct radical. The mechanism of the (RSSR)cation radical induced oxidation of thiolate appears to depend on the stability of the 3-electron bonded disulphide radical anion. (author)

382

Photocatalytic Reductive Cyclizations of Enones: Divergent Reactivity of Photogenerated Radical and Radical Anion Intermediates  

OpenAIRE

Photocatalytic reactions of enones using metal polypyridyl complexes proceed by very different reaction manifolds in the presence of either Lewis or Brønsted acid additives. Previous work from our lab demonstrated that photocatalytic [2+2] cycloadditions of enones required the presence of a Lewis acidic co-catalyst, presumably to activate the enone and stabilize the key radical anion intermediate. On the other hand, Brønsted acid activators alter this reactivity and instead promote reductiv...

Du, Juana; Espelt, Laura Ruiz; Guzei, Ilia A.; Yoon, Tehshik P.

2011-01-01

383

Cistectomía Radical Laparoscópica / Radical laparoscopic cystectomy  

Scientific Electronic Library Online (English)

Full Text Available SciELO Spain | Language: Spanish Abstract in spanish La cistectomía radical laparoscópica está siendo introducida en la mayoría de los grupos que tienen demostrada experiencia en cirugía laparoscópica y sobre todo en aquellos que han superado la curva de aprendizaje en prostatectomía radical laparoscópica. Se considera aún una técnica de alta compleji [...] dad, que no está aún al alcance de la mayoría de los Servicios de Urología. Revisamos en este trabajo la técnica quirúrgica así como la literatura al respecto, haciendo hincapié en sus indicaciones, ventajas y morbilidad más habitual. Abstract in english Radical laparoscopic cystectomy is being adopted by most groups with proven experience in laparoscopic surgery, especially by those who have already completed the learning curves in radical laparoscopic prostatectomy. It is still considered a highly complex technique, which has not yet been mastered [...] in many Urology Units. In this article, we review the surgical technique and available literature on this approach, with special emphasis on its indications, advantages and most frequent morbidity.

O., Castillo; R., Cabello Benavente; G., Briones Mardones; C., Hernández Fernández.

2006-05-01

384

Short communication: Viability of culture organisms in honey-enriched acidophilus-bifidus-thermophilus (ABT)-type fermented camel milk.  

Science.gov (United States)

The aim of this research was to monitor the survival during refrigerated storage of Lactobacillus acidophilus LA-5 (A), Bifidobacterium animalis ssp. lactis BB-12 (B), and Streptococcus thermophilus CHCC 742/2130 (T) in cultured dairy foods made from camel and, for comparison, cow milks supplemented with black locust (Robinia pseudoacacia L.) honey and fermented by an acidophilus-bifidus-thermophilus (ABT)-type culture. Two liters of dromedary camel milk and 2 L of cow milk were heated to 90 °C and held for 10 min, then cooled to 40 °C. One half of both types of milk was fortified with black locust honey at the rate of 5.0% (wt/vol), whereas the other half was devoid of honey and served as a control. The camel and cow milks with and without honey were subsequently inoculated with ABT-5 culture and were fermented at 37 °C until a pH value of 4.6 was reached. Thereafter, the probiotic fermented milks were cooled to 15 °C in ice water and were each separated into 18 fractions that were transferred in sterile, tightly capped centrifuge tubes. After 24 h of cooling at 8 °C (d 0), the samples were stored at refrigeration temperature (4 °C). Three tubes of all 4 products (i.e., fermented camel and cow milks with and without honey) were taken at each sampling time (i.e., following 0, 7, 14, 21, 28, and 35 d of storage), and the counts of characteristic microorganisms and those of certain spoilage microbes (yeasts, molds, coliforms, Escherichia coli) were enumerated. The entire experimental program was repeated twice. The results showed that addition of black locust honey at 5% to heat-treated camel and cow milks did not influence the growth and survival of starter streptococci during production and subsequent refrigerated storage of fermented ABT milks. In contrast, honey improved retention of viability of B. animalis ssp. lactis BB-12 in the camel milk-based product during storage at 4 °C up to 5 wk. No spoilage organisms were detected in any of the samples tested in this study. In conclusion, supplementation of cultured dairy foods, especially those made from camel milk, with honey is recommended because honey is a healthy natural sweetener with a variety of beneficial microbiological, nutritional, and sensory properties. PMID:25151879

Varga, L; Süle, J; Nagy, P

2014-11-01

385

Antioxidant Capacity and Radical Scavenging Effect of Polyphenol Rich Mallotus philippenensis Fruit Extract on Human Erythrocytes: An In Vitro Study.  

Science.gov (United States)

Mallotus philippinensis is an important source of molecules with strong antioxidant activity widely used medicinal plant. Previous studies have highlighted their anticestodal, antibacterial, wound healing activities, and so forth. So, present investigation was designed to evaluate the total antioxidant activity and radical scavenging effect of 50% ethanol fruit glandular hair extract (MPE) and its role on Human Erythrocytes. MPE was tested for phytochemical test followed by its HPLC analysis. Standard antioxidant assays like DPPH, ABTS, hydroxyl, superoxide radical, nitric oxide, and lipid peroxidation assay were determined along with total phenolic and flavonoids content. Results showed that MPE contains the presence of various phytochemicals, with high total phenolic and flavonoid content. HPLC analysis showed the presence of rottlerin, a polyphenolic compound in a very rich quantity. MPE exhibits significant strong scavenging activity on DPPH and ABTS assay. Reducing power showed dose dependent increase in concentration absorption compared to standard, Quercetin. Superoxide, hydroxyl radical, lipid peroxidation, nitric oxide assay showed a comparable scavenging activity compared to its standard. Our finding further provides evidence that Mallotus fruit extract is a potential natural source of antioxidants which have a protective role on human Erythrocytes exhibiting minimum hemolytic activity and this justified its uses in folklore medicines. PMID:25525615

Gangwar, Mayank; Gautam, Manish Kumar; Sharma, Amit Kumar; Tripathi, Yamini B; Goel, R K; Nath, Gopal

2014-01-01

386

Evaluation of new thiadiazoles and benzothiazoles as potential radioprotectors: free radical scavenging activity in vitro and theoretical studies (QSAR, DFT).  

Science.gov (United States)

Thiol and aminothiol compounds are among the most efficient chemical radioprotectors. To increase their efficiency, we synthesized two new classes of thiol and aminothiol compounds derived from benzothiazole (T1, T2, AM1, AM2) and thiadiazole (T3, T4, AM3) structures. We examined them for their ability to scavenge free radicals (DPPH*, ABTS(*+), *OH). Thiol derivatives with a thiadiazole structure are the most active compounds scavenging DPPH* and ABTS(*+) free radicals, with an IC(50) of 0.053+/-0.006 and 0.023+/-0.002 mM, respectively, for the derivative T3. Moreover, compounds T1, T2, and T3 at 60 microM gave 83% protection against 2-deoxyribose degradation by *OH. The ability of these compounds to protect DNA against *OH produced by a Fenton reaction and gamma-irradiation (15 Gy)-induced strand breaks was also evaluated on pBR322 plasmid DNA. In both tests thiol derivatives were the most efficient compounds. Derivatives T2 and T3 totally inhibit DNA strand breaks at the concentration of 50 microM. The protection afforded by these derivatives was comparatively higher than that of the radioprotectors WR-2721 and WR-1065. Our data indicate that these two compounds are free radical scavengers and potential antioxidant agents. Finally, DFT and QSAR studies were performed to support the experimental observations. PMID:19439222

Prouillac, Caroline; Vicendo, Patricia; Garrigues, Jean-Christophe; Poteau, Romuald; Rima, Ghassoub

2009-04-15

387

Antioxidant Capacity and Radical Scavenging Effect of Polyphenol Rich Mallotus philippenensis Fruit Extract on Human Erythrocytes: An In Vitro Study  

Science.gov (United States)

Mallotus philippinensis is an important source of molecules with strong antioxidant activity widely used medicinal plant. Previous studies have highlighted their anticestodal, antibacterial, wound healing activities, and so forth. So, present investigation was designed to evaluate the total antioxidant activity and radical scavenging effect of 50% ethanol fruit glandular hair extract (MPE) and its role on Human Erythrocytes. MPE was tested for phytochemical test followed by its HPLC analysis. Standard antioxidant assays like DPPH, ABTS, hydroxyl, superoxide radical, nitric oxide, and lipid peroxidation assay were determined along with total phenolic and flavonoids content. Results showed that MPE contains the presence of various phytochemicals, with high total phenolic and flavonoid content. HPLC analysis showed the presence of rottlerin, a polyphenolic compound in a very rich quantity. MPE exhibits significant strong scavenging activity on DPPH and ABTS assay. Reducing power showed dose dependent increase in concentration absorption compared to standard, Quercetin. Superoxide, hydroxyl radical, lipid peroxidation, nitric oxide assay showed a comparable scavenging activity compared to its standard. Our finding further provides evidence that Mallotus fruit extract is a potential natural source of antioxidants which have a protective role on human Erythrocytes exhibiting minimum hemolytic activity and this justified its uses in folklore medicines. PMID:25525615

Gautam, Manish Kumar; Sharma, Amit Kumar; Tripathi, Yamini B.; Goel, R. K.; Nath, Gopal

2014-01-01

388

Aliphatic peptidyl hydroperoxides as a source of secondary oxidation in hydroxyl radical protein footprinting  

OpenAIRE

Hydroxyl radical footprinting is a technique for studying protein structure and binding that entails oxidizing a protein system of interest with diffusing hydroxyl radicals, and then measuring the amount of oxidation of each amino acid. One important issue in hydroxyl radical footprinting is limiting amino acid oxidation by secondary oxidants to prevent uncontrolled oxidation which can cause amino acids to appear more solvent accessible than they really are. Previous work suggested that hydro...

Saladino, Jessica; Liu, Mian; Live, David; Sharp, Joshua S.

2009-01-01

389

Radical transfer between proteins: role of tyrosine, tryptophan and protein peroxyl radicals  

International Nuclear Information System (INIS)

Reaction of the Fe(III) forms of the heme proteins myoglobin (Mb) and horseradish peroxidase (HRP) with H2O2 gives rise to high-oxidation-state heme-derived species which can be described as a Fe(IV)-oxo porphyrin radical-cation ('Compound 1'). In the case of Mb, the Fe(IV)-oxo porphyrin radical-cation undergoes rapid electron transfer with the surrounding protein to give protein (globin)-derived radicals and an Fe(lV)-oxo species ('Compound 2'). The globin-derived radicals have been shown to be located at two (or more) sites: Tyr-103 or Trp-14, with the latter radical known to react with oxygen to give a Trp-derived peroxyl radical (Mb-Trp-OO*). With HRP, the Fe(lV)-oxo porphyrin radical-cation carries out two successive one-electron oxidation reactions at the exposed heme edge to give firstly 'Compound 2' [the Fe(lV)oxo species] and then the resting Fe(III) state of the enzyme. n this study we have investigated whether the Trp-14 peroxyl radical from Mb and the Compound 1 and 2 species from HRP (in the absence and presence of free Tyr) can oxidise amino acids, peptides and proteins. Such reactions constitute intermolecular protein-to-protein radical transfer reactions and hence protein chain-oxidation. We have also examined whether these oxidants react with antioxidants. Reaction of these heme-protein derived oxidants with amino acids, proteins and antioxidants has been carried out at room temperature for defined periods of time before freeze-qor defined periods of time before freeze-quenching to 77K to halt reaction. The radical species present in the reaction system at the time of freezing were subsequently examined by EPR spectroscopy at 77K. Three free amino acids, Tyr, Trp and Cys (with Cys the least efficient) have been shown to react rapidly with Mb-Trp-OO*, as evidenced by the loss of the characteristic EPR features of Mb-Trp-OO* on inclusion of increasing concentrations of the amino acids. All other amino acids are much less reactive. Evidence has also been obtained for (inefficient) hydrogen atom abstraction from ?-carbon sites on peptides; this may give rise to backbone cleavage in the presence of oxygen

390

Radical transfer between proteins: role of tyrosine, tryptophan and protein peroxyl radicals  

Energy Technology Data Exchange (ETDEWEB)

Reaction of the Fe(III) forms of the heme proteins myoglobin (Mb) and horseradish peroxidase (HRP) with H{sub 2}O{sub 2} gives rise to high-oxidation-state heme-derived species which can be described as a Fe(IV)-oxo porphyrin radical-cation (`Compound 1`). In the case of Mb, the Fe(IV)-oxo porphyrin radical-cation undergoes rapid electron transfer with the surrounding protein to give protein (globin)-derived radicals and an Fe(lV)-oxo species (`Compound 2`). The globin-derived radicals have been shown to be located at two (or more) sites: Tyr-103 or Trp-14, with the latter radical known to react with oxygen to give a Trp-derived peroxyl radical (Mb-Trp-OO*). With HRP, the Fe(lV)-oxo porphyrin radical-cation carries out two successive one-electron oxidation reactions at the exposed heme edge to give firstly `Compound 2` [the Fe(lV)oxo species] and then the resting Fe(III) state of the enzyme. n this study we have investigated whether the Trp-14 peroxyl radical from Mb and the Compound 1 and 2 species from HRP (in the absence and presence of free Tyr) can oxidise amino acids, peptides and proteins. Such reactions constitute intermolecular protein-to-protein radical transfer reactions and hence protein chain-oxidation. We have also examined whether these oxidants react with antioxidants. Reaction of these heme-protein derived oxidants with amino acids, proteins and antioxidants has been carried out at room temperature for defined periods of time before freeze-quenching to 77K to halt reaction. The radical species present in the reaction system at the time of freezing were subsequently examined by EPR spectroscopy at 77K. Three free amino acids, Tyr, Trp and Cys (with Cys the least efficient) have been shown to react rapidly with Mb-Trp-OO*, as evidenced by the loss of the characteristic EPR features of Mb-Trp-OO* on inclusion of increasing concentrations of the amino acids. All other amino acids are much less reactive. Evidence has also been obtained for (inefficient) hydrogen atom abstraction from {alpha}-carbon sites on peptides; this may give rise to backbone cleavage in the presence of oxygen

Irwin, J.A.; Ostdal, H.; Davies, M.J. [The Heart Research Institute, Camperdown, NSW (Australia)

1998-12-31

391

Synthesis of [14C]ABT-418, a cholinergic channel activator labeled at two sites on the isoxazole ring  

International Nuclear Information System (INIS)

[14C]ABT-418, (S)-3-[14C]methyl-5-[N-methyl-2-pyrrolidinyl] [4-14C]isoxazole hydrochloride, was labeled in two positions at maximum specific activity. Starting with 100 mCi of sodium [2-14C]acetate, 14.6 mCi at 105 mCi/mmol was obtained in 8 steps including the formation of [1,3-14C]acetone in the pyrolysis of barium [2-14C]acetate. The key step was the formation of the dianion of [1,3-14C]acetone oxime and its condensation with L-proline methyl ester. (author)

392

Prostatectomia radical laparoscópica / Radical laparoscopic prostatectomy  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: Spanish Abstract in spanish La Prostatectomia radical laparoscópica (PRL) se ha convertido en una técnica atractiva para el tratamiento quirúrgico del cáncer de próstata localizado. Si bien, los resultados actuales son inicialmente comparables a la prostatectomia radical abierta, es importante mencionar que la tendencia quirúr [...] gica en cáncer de próstata, se ha modificado a pesar de que no hay estudios que confirmen la superioridad del método endoscópico y hoy, el estándar dorado sigue siendo la prostatectomia radical abierta. Dos rutas de acceso quirúrgico pueden ser utilizadas para la realización de PRL, la vía extraperitoneal y la transperitoneal. Un menor sangrado y menor tasa de transfusión, así como, tiempo de hospitalización y recuperación más cortos, son ventajas incuestionables para los procedimientos laparoscópicos. Los resultados oncológicos y funcionales de la prostatectomia laparoscópica son hoy en día comparables, pero en ningún caso mejores que la técnica retropúbica abierta estándar. Recientemente, Hu y colaboradores, en base a una revisión de cerca de 3.000 pacientes tratados en los Estados Unidos, plantean la posibilidad de que los pacientes tratados