WorldWideScience
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KINETICS PROFILES IN THE REACTION OF ABTS DERIVED RADICALS WITH SIMPLE PHENOLS AND POLYPHENOLS  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in english The kinetic profile associated to the reaction of phenols with 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) derived radicals is extremely dependent of the characteristics of the substrate. In particular, polyphenols present complex profiles that can be associated to successive react [...] ions of different reactive centers present in the target molecule. Also, changes in the secondary reactions of the produced radicals can lead to a partial recovery of the ABTS radical concentration at intermediate reaction times, as observed employing 1,4-dihydroxybenzene. Although the kinetic profiles of monophenols are considerably simpler, the stoichiometry of the process is unexpected. For example, the data obtained imply that four radicals are consumed by each p-tertbutylphenol molecule introduced into the system. This large stoichiometric coefficient is not compatible with a simple, phenol promoted, back reduction of the ABTS radical. These results, as well as the overshoot observed employing 1,4-dihydroxybencene, cast doubts on the use of ABTS based methodologies to quantitatively measure the capacity of a given compound to trap free radicals or the amount of free radical scavengers present in complex mixtures

CAROLA, HENRIQUEZ; CAROLINA, ALIAGA; EDUARDO, LISSI.

2004-03-01

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KINETICS PROFILES IN THE REACTION OF ABTS DERIVED RADICALS WITH SIMPLE PHENOLS AND POLYPHENOLS  

Directory of Open Access Journals (Sweden)

Full Text Available The kinetic profile associated to the reaction of phenols with 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS derived radicals is extremely dependent of the characteristics of the substrate. In particular, polyphenols present complex profiles that can be associated to successive reactions of different reactive centers present in the target molecule. Also, changes in the secondary reactions of the produced radicals can lead to a partial recovery of the ABTS radical concentration at intermediate reaction times, as observed employing 1,4-dihydroxybenzene. Although the kinetic profiles of monophenols are considerably simpler, the stoichiometry of the process is unexpected. For example, the data obtained imply that four radicals are consumed by each p-tertbutylphenol molecule introduced into the system. This large stoichiometric coefficient is not compatible with a simple, phenol promoted, back reduction of the ABTS radical. These results, as well as the overshoot observed employing 1,4-dihydroxybencene, cast doubts on the use of ABTS based methodologies to quantitatively measure the capacity of a given compound to trap free radicals or the amount of free radical scavengers present in complex mixtures

CAROLA HENRIQUEZ

2004-03-01

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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  

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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[Topo-optical demonstration of lineal arrangement of vicial OH radicals by means of aldehyde bisulfite toluidine blue (ABT) reaction].  

Science.gov (United States)

Topo-optical reaction with aldehyd-bisulfit-toluidinblue (ABT) suitable for the demonstration of lineal arrangement of vicinal OH-radicals is described. On the base of double refringement brought about by the orientated dye-binding, this reaction is suitable for the study of molecular arrangement of carbohydrate components of biological structures (glycoproteins, glycolipides and polysaccharides). Double refringement brought about by the reaction ABT optically is negative to the length of polysaccharide-chains. Practical use of the method is demonstrated on several biological structures. Findings show, that reaction ABT opens new possibilities for the study of ultrastructure of carbohydrate components of various tissue elements. PMID:1264101

Romháyi, G; Németh, A; György, D; Deák, G

1976-04-01

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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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Population Pharmacokinetics and Exposure-Uric Acid Analyses After Single and Multiple Doses of ABT-639, a Calcium Channel Blocker, in Healthy Volunteers.  

Science.gov (United States)

ABT-639 is a selective T-type calcium channel blocker with efficacy in a wide range of preclinical models of nociceptive and neuropathic pain. In the current first-in-human (FIH) study, the pharmacokinetics, tolerability, and safety of ABT-639 after single- (up to 170 mg) and multiple doses (up to 160 mg BID) were evaluated in healthy volunteers in a randomized, double-blinded, placebo-controlled manner. ABT-639 demonstrated acceptable safety and pharmacokinetic profiles in human. Results from assessment of the routine laboratory variables showed an unexpected statistically significant and clinically relevant decrease in blood uric acid with the increase in ABT-639 dose, which is possibly due to inhibition in URAT1 transporter. Pharmacokinetic/pharmacodynamic models were constructed to characterize the relationship between ABT-639 exposure and uric acid response. The final model was a mechanism-based indirect response pharmacodynamic model with the stimulation of uric acid elimination by ABT-639. The model estimated K in values in males and females were 10.2 and 7.13 ?mol/h, respectively. The model estimated K out was 0.033 1/h. ABT-639 concentration that can produce 50% stimulation in uric acid elimination was estimated to be 8,070 ng/mL. Based on the final model, further simulations were conducted to predict the effect of ABT-639 on uric acid in gout patients. The simulation results indicated that, if the urate-lowering response to ABT-639 in gout patients is similar to that in healthy subjects, ABT-639 BID doses of 140 mg or higher would be expected to provide clinically meaningful lowering of blood uric acid levels below the 380 ?mol/L solubility limit of monosodium urate. PMID:25567367

An, Guohua; Liu, Wei; Duan, W Rachel; Nothaft, Wolfram; Awni, Walid; Dutta, Sandeep

2015-03-01

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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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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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Thiazolidin-4-ones from 3-(Aminomethyl)pyridine, Arenealdehydes and Mercaptoacetic Acid: Synthesis and Radical Scavenger Activity  

Scientific Electronic Library Online (English)

Full Text Available The efficient synthesis of fifteen novel thiazolidin-4-ones from reaction of 3-(aminomethyl) pyridine (3-picolylamine), arenealdenhydes and mercaptoacetic acid was described. The desired compounds were obtained in moderated to good yields by two methodologies: conventional heating and ultrasound irr [...] adiation. The thiazolidin-4-ones were fully identified and characterized by nuclear magnetic resonance (NMR), gas chromatography coupled to mass spectrometry (GC?MS) and high resolution mass spectrometry (HRMS) techniques. Four compounds showed radical scavenger activity in the 2,2’-azinobis-3-ethyl-benzothiazoline-6-sulfonic acid (ABTS) assay.

Adriana M., Neves; Auri R., Duval; Gabriele A., Berwaldt; Daniela P., Gouvêa; Natália P., Flores; Pâmela G. da, Silva; Francieli M., Stefanello; Wilson, Cunico.

2015-02-01

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TOTAL PHENOLIC, CONDENSED TANNINS, ASCORBIC ACID CONTENTS AND FREE RADICAL SCAVENGING ACTIVITY IN SOME OF THE UNDERUTILIZED HORTICULTURAL CROPS FROM NORTH-WESTERN INDIAN HIMALAYAS  

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Full Text Available Mature fruits of F. roxburghii and F. daltoniana, areal bulbils of D. kumaunensis and roots of P. acinosa werecollected from Uttarakhand, India and were evaluated for their total phenolics, condensed tannins, ascorbic acid(Vita C and Free radical scavenging activities against DPPH•, ABTS•+ and Hydrogen peroxide (H2O2 freeradicals. Total phenolics varied between 9.24-16.92 mg TA/g, catechins between 1.31-5.03 mg/g, ascorbic acidbetween 35.80-63.69 mg/100g. Methanolic extracts of F. roxburghii showed maximum percent scavengingactivities on DPPH and ABTS radical while H2O2 scavenging activity was observed highest in D. kumaunensis.IC50 values for radical scavenging assays of methanolic extracts were calculated and found that in terms ofantioxidant activities, F. roxburghii showed maximum followed by D. kumaunensis and minimum was by P.acinosa. Multifactorial comparisons using principal component analysis (PCA was done and found that F.daltoniana possessed higher ascorbic acid content, while F. roxburghii possessed higher total phenolics, condensedtannin and free radical scavenging activities then others studied plant samples. Results of the finding providesevidence that the crude methanolic extract of the studied underutilized horticultural crops are valuable source ofnatural antioxidant, which can be applied in both healthy medicine and food industry.

J. C. BHATT

2013-01-01

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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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OH radical induced depolymerization of poly(methacrylic acid)  

International Nuclear Information System (INIS)

Hydroxyl radicals (generated pulse radiolytically in dilute N2O-saturated aqueous solutions) react with poly(methacrylic acid) producing two kinds of radicals. The primary radical is converted into a secondary one by H-abstraction (k=3.5x102 s-1) as monitored by changes in the UV spectrum. Subsequently, the secondary radicals undergo chain scission (k=1.8 s-1 at pH 7-9). This process has been followed both by spectrophotometry as well as by conductometry. In competition with the bimolecular decay of the radicals the ensuing end-chain radicals undergo efficient depolymerization resulting in the release of monomer. Since the lifetime of the radicals is much longer at high pH, where the polymer attains a rod-like conformation, depolymerization is most efficient in basic solution

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Acid and base catalysed oxidation of 3-substituted 4-hydroxy cinnamic acid by hydroxyl radical  

International Nuclear Information System (INIS)

Hydroxyl radical reactions of 3,4-dihydroxy cinnamic acid and 3-methoxy-4-hydroxy cinnamic acid were studied in the pH range 3-11. The initial reaction in these cases was formation of a radical adduct followed by elimination of water to yield the corresponding phenoxyl radical which was independently confirmed by one electron oxidation by azide radicals. The water elimination was found to be catalysed by both acid and base in case of 3,4-dihydroxy cinnamic acid, whereas it was only base catalysed in case of 3-methoxy-4-hydroxy cinnamic acid. (author)

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Arjunic acid, a strong free radical scavenger from Terminalia arjuna.  

Science.gov (United States)

This study was designed to investigate the antioxidant and free radical scavenging capacities of arjunic acid, an aglycone obtained from the fruit of medicine Terminalia Fruit. Liver microsomes, mitochondria, and red blood cells (RBCs) were prepared from Wistar rats. The antioxidant capacity was determined by the inhibitory effect on lipid peroxidation, hydrogen peroxide induced RBCs hemolysis, and RBCs autoxidative hemolysis. The free radical scavenging activity was tested by DPPH method and 2',7'-dichlorodihydrofluoresc in diacetate (DCFH(2)-DA) assay. Ascorbic acid was chosen as the positive controls. Results showed that arjunic acid was a strong antioxidant and a free radical scavenger, more potent than ascorbic acid, in microsomes lipid peroxidation, DPPH, hydrogen peroxide induced RBCs hemolysis, and (DCFH(2)-DA) assay (p 0.05). PMID:18306462

Sun, Fang-Yun; Chen, Xiu-Ping; Wang, Jin-Hua; Qin, Hai-Lin; Yang, Su-Rong; Du, Guan-Hua

2008-01-01

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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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Acid-catalyzed oxidative radical addition of ketones to olefins.  

Science.gov (United States)

Based on a mechanistic study, we have discovered a Brønsted acid catalyzed formation of ketone radicals. This is believed to proceed via thermally labile alkenyl peroxides formed in situ from ketones and hydroperoxides. The discovery could be utilized to develop a multicomponent radical addition of unactivated ketones and tert-butyl hydroperoxide to olefins. The resulting ?-peroxyketones are synthetically useful intermediates that can be further transformed into 1,4-diketones, homoaldol products, and alkyl ketones. A one-pot reaction yielding a pharmaceutically active pyrrole is also described. PMID:24777703

Schweitzer-Chaput, Bertrand; Demaerel, Joachim; Engler, Hauke; Klussmann, Martin

2014-08-11

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Radical scavenging and antioxidant activities of methanolic extracts from Hypericum species growing in Bulgaria  

OpenAIRE

Thirteen Hypericum species growing in Bulgaria were investigated for free radical-scavenging activity, antioxidant activity, total tannins and total flavonoids contents. Methanolic extracts from the Hypericum species were analyzed for radical scavenging and antioxidant activities using DPPH-, ABTS- free radicals, total antioxidant activity and inhibition of lipid peroxidation by ferric thiocyanate (FTC) method. Butylated hydroxytoluene and ascorbic acid were used as positive controls. Methano...

Zheleva-dimitrova, Dimitrina; Nedialkov, Paraskev; Kitanov, Gerassim

2010-01-01

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Heterogeneous Reaction of HO2 Radical with Dicarboxylic Acid Particles  

Science.gov (United States)

HOx(OH+ HO2) radical plays a central role in the tropospheric chemistry. Recently, the heterogeneous loss of HO2 by aerosol particles is a potentially important HOx sink in the troposphere suggested from observation study. However, there have been few studies for loss of HO2 by aerosols. In this study, we measured the HO2 uptake coefficients for four dicarboxylic acids (succinic acid, glutaric acid, adipic acid, and pimelic acid) aerosol particles under ambient conditions (760Torr and 296K) using an aerosol flow tube(AFT) coupled with a chemical conversion /laser-induced fluorescence(CC/LIF) technique. The CC/LIF technique enabled experiments to be performed at almost the same HO2 radical concentration as that in the atmosphere(-10^8 molecules/cm^3). In this system, the effect of the self-reaction of HO2 in the gas phase can be neglected. HO2 radicals were injected into the AFT through a vertically movable Pyrex tube. Injector position dependent profiles of LIF intensity were measured as a function of aerosol concentration at 30% and 70% of relative humilities (RH). Determined HO2 uptake coefficients by succinic acid, glutaric acid, adipic acid, and pimelic acid aerosol particles at 30% RH were 0.05 +/- 0.02, 0.07 +/- 0.03, 0.02 +/- 0.01, and 0.06 +/- 0.03, respectively, while the uptake coefficients by those particles at 70% RH were 0.13 +/- 0.05, 0.13 +/- 0.03, 0.06 +/- 0.01, and 0.11 +/- 0.03, respectively. These results suggest that compositions and relative humidity are significant to the HO2 uptake. We will discuss the potential HO2 loss processes.

Taketani, F.; Kanaya, Y.

2010-12-01

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Determination of peroxy radical-scavenging of lactic acid bacteria.  

Science.gov (United States)

Responses of lactic acid bacteria (LAB) to peroxy radicals generated via thermal (40 degrees C) decomposition of the diazocompound 2,2,-azo-bis (2-amidinopropane) dihydrochloride (ABAP), were studied. In general, LAB displayed survival curves with shoulders and tails indicative of 'multihit' killing by exposure to peroxy radicals. One strain, Lactococcus lactis subsp. lactis DIP15, producing a slope of 0.0105 in the kinetic analysis when exposed to 4 mM ABAP, exhibited a measurable antioxidant capacity. The other LAB failed to show any significant antioxidant capacity. The antioxidant capacity of strain DIP15 remained constant after cells have been heat-treated, suggesting that compounds bearing free radical scavenging capacity are rather stable. PMID:11252501

Stecchini, M L; Del Torre, M; Munari, M

2001-02-28

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Structure and recombination of radicals in amino acid crystals  

International Nuclear Information System (INIS)

Decay kinetics, of the free radicals produced in crystalline amino acids by x-irradiation, was studied in the temperature range 250 to 1850C. The decay data could not be fitted to a first order rate law. Second order plots indicated two distinct second order processes: the initial faster process and the major slightly slower process. The initial process was of short duration at higher temperatures and at all temperatures it was responsible for the decay of 25 to 30 percent of the initial number of radicals. A vacancy controlled bulk diffusion mechanism is proposed for the major process and the initial process is postulated to be a conformationally favoured bulk diffusion process. L-Arginine HCl monohydrate on x-irradiation at room temperature shows radicals that are stable (relatively) at room temperature but decay at temperatures above 400C. The decay at 750C is found to be zero order while the crystal dehydrates simultaneously. A hydrogen abstraction mechanism is proposed for the spin decay on the basis of the crystal structure and the radical structure. The radical structure was determined from the angular studies of the single crystals. (Diss. Abstr. Int., B)

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URIC ACID REACTION WITH DPPH RADICALS AT THE MICELLAR INTERFACE  

Scientific Electronic Library Online (English)

Full Text Available El ácido úrico es un importante antioxidante hidrosoluble. En este trabajo se muestra que es capaz de reaccionar con radicales liposolubles (difenilpicrilhidracil, DPPH) en la interface de soluciones micelares. La velocidad del proceso sigue el orden micelas cationicas > mezcla etanol:buffer > micel [...] as neutras micelas anionicas Estos resultados pueden racionalizarse en términos de la compartimentalización de ambos reactantes en diferentes microfases y del efecto que ejercen las interacciones electrostáticas sobre el acceso del anión urato a la interface micelar. Experimentos diseñados para evaluar una posible regeneración del radical derivado del alfa-tocoferol por el anión urate entregaron resultados negativos, indicando que este anión no es capaz de regenerar la vitamina E en este tipo de sistemas. Abstract in english Uric acid, a water soluble antioxidant, is able to react with micelle incorporated diphenylpicrylhydracyl radicals. This indicates that uric acid can react at the lipid/water interface. The rate of the process follows the order cationic micelles >buffer/etanol > neutral micelles anionic micelles The [...] se results can be explained in terms of the compartmentalization of the reactants in different environments and the effect of electrostatic interactions in modulating the access of the urate anion to the micellar interface. Experiments aimed to determine if urate is able to react with alpha-tocopheroxyl radicals regenerating a-tocopherol were uncesessful, indicating that urate is not able to delay vitamin E consumption in the presence of lipid - soluble free radicals

E., ABUIN; E., LISSI; P., ORTIZ; C., HENRIQUEZ.

2002-06-01

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Gas-phase infrared spectrum and acidity of the radical cation of 9-methylguanine.  

Science.gov (United States)

Oxidative damage to DNA yields guanine radical cations. Their gas-phase IR spectroscopic signature and acidity have been modelled by the radical cation of 9-methylguanine. Comparisons with quantum chemistry calculations suggest that radical cation formation produces the ground-state keto tautomer, which has an N-H acidity enhanced by ~470 kJ mol(-1). PMID:23852224

Feketeová, Linda; Khairallah, George N; Chan, Bun; Steinmetz, Vincent; Maître, Philippe; Radom, Leo; O'Hair, Richard A J

2013-08-25

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Oxidation of hydroxybenzoic acids by •OH radical produced radiolytically  

Science.gov (United States)

The yields of the dihydroxybenzoic acids produced in the radiolytic oxidation of aqueous solutions of the hydroxybenzoic acids were determined to provide information on the concerted effects of -OH and -COOH substituents on the electronic structures of aromatics. Because •OH radical is a strong electrophyl it adds preferentially at the electron rich sites of an aromatic ring. The distribution of hydroxylated products, therefore, gives a measure of the charge distribution in the aromatic. In these studies the hydroxylated cyclohexadienyl radicals initially produced were oxidized to the corresponding dihydroxybenzoic acids by ferricyanide present in the irradiated solution. Product analysis was by chromatographic and electrophoretic methods. It is shown that, as in the case of phenol, the hydroxyl substituent has a dominant ortho-para directing effect that is modified somewhat by the presence of a -COOH substituent. Substantial yields for attack of •OH at the carboxy substituted sites of 2- and 4-hydroxybenzoic acid are also reported. This observation demonstrates that addition of •OH at the ipso positions of carboxylated aromatics can be of considerable importance.

Albarran, Guadalupe; Esparza, Maribel; Mendoza, Edith

2015-02-01

26

Reaction of selenium dioxide free radicals with amino acids and enzymes  

International Nuclear Information System (INIS)

Pulse radiolysis of selenium dioxide in aqeuous solution has shown the presence of three selenite radicals in acid-base equilibrium within well defined pH ranges. The selenite radicals react selectively with amino acids, preferentially with the aromatic ones in the order tryptophan > tyrosine > histidine independently of the acid-base structure of the radical. Kinetic and spectroscopic data on the reaction of selenite radicals with some proteins and parallel inactivation studies generally reflect knowledge on the amino acid residues mainly involved in the radical attack. The investigations at different pH values on the reactivity of selenite radicals with amino acids and proteins and on the transient spectra of the reaction products exhibit different behaviour for the various acid-base structures of the selenite radicals, reflecting the influence of particular ionizable groups in the reacting molecules and the structure modifications at the level of proteins. (author)

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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

28

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

29

Radical and non-radical mechanisms for alkane oxidations by hydrogen peroxide-trifluoroacetic acid.  

Science.gov (United States)

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 (approximately 75 degrees 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. PMID:11430097

Camaioni, D M; Bays, J T; Shaw, W J; Linehan, J C; Birnbaum, J C

2001-02-01

30

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

31

Hydroxyl radical substitution in halogenated carbonyls: oxalic acid formation.  

Science.gov (United States)

An ab initio study of OH radical substitution reactions in halogenated carbonyls is conducted. Hydroxyl radical substitution into oxalyl dichloride [ClC(O)C(O)Cl] and oxalyl dibromide [BrC(O)C(O)Br], resulting in the formation of oxalic acid, is presented. Analogous substitution reactions in formyl chloride [ClCH(O)], acetyl chloride [ClC(O)CH(3)], formyl bromide [BrCH(O)], and acetyl bromide [BrC(O)CH(3)] are considered. Energetics of competing hydrogen abstraction reactions for all applicable species are computed for comparison. Geometry optimizations and frequency computations are performed using the second-order Møller-Plesset perturbation theory (MP2) and the 6-31G(d) basis set for all minimum species and transition states. Single point energy computations are performed using fourth-order Møller-Plesset perturbation theory (MP4) and coupled cluster theory [CCSD(T)]. Potential energy surfaces, including activation energies and enthalpies, are determined from the computations. These potential energy surfaces show that OH substitution into ClC(O)C(O)Cl and BrC(O)C(O)Br, resulting in the formation of oxalic acid and other minor products, is energetically favorable. Energetics of analogous reactions with ClCH(O), BrCH(O), ClC(O)CH(3), and BrC(O)CH(3) are also computed. PMID:20131850

Christiansen, Carrie J; Dalal, Shakeel S; Francisco, Joseph S; Mebel, Alexander M; Gaffney, Jeffrey S

2010-03-01

32

Radical intermediates and antioxidants: an ESR study of radicals formed on carnosic acid in the presence of oxidized lipids.  

Science.gov (United States)

Carnosic acid, an antioxidant extracted from rosemary, is shown to produce radicals when in contact with oxidized methyl oleate in the absence of air above 50 degrees C. Two radical species are formed: the first one, stable up to approximately 110 degrees C, is an hydroxy-phenoxy radical whose ESR spectrum was analyzed by studying its temperature dependence and its sensitivity to deuterium/proton exchange. The second species was observed above 110 degrees C, its ESR spectrum was identical to the spectrum obtained when carnosol, another antioxidant extracted from rosemary, was heated at the same temperature in the presence of oxidized lipid. This observation is probably due to the transformation of carnosic acid into carnosol; the analysis of the corresponding ESR spectrum suggests the formation of a keto phenoxy radical exhibiting a great delocalization of the unpaired electron. PMID:7827696

Geoffroy, M; Lambelet, P; Richert, P

1994-09-01

33

Computational Studies of Radicals Relevant to Nucleic Acid Damage  

Science.gov (United States)

Computational methods using ab initio and density functional theory have been employed to characterize transient intermediates of DNA and RNA damage. Hyperfine coupling constants and atomic spin densities have been obtained for adenine, guanine, cytosine, thymine, uracil, some of their derivatives, as well as nucleoside models, that were compared with experimental spectroscopic data from radiolysis. Ionization energies and redox potentials can be reliably calculated at high levels of theory and used to evaluate the energetics of charge and proton transfer reactions of nucleobase ions with solvent, amino acids, carbohydrates, and other molecules that are likely to participate in DNA damage. The structures, energetics, and kinetics of nucleobase and carbohydrate radical reactions have been addressed by computations and utilized to guide experiments and aid in experimental data interpretation.

Turecek, Frantisek

34

Reactions of linoleic acid peroxyl radicals with phenolic antioxidants: a pulse radiolysis study  

Energy Technology Data Exchange (ETDEWEB)

Linoleic acid peroxyl radicals (LOO) can be viewed as model intermediates occurring during lipid peroxidation processes. Formation and reactions of these species were investigated in aqueous alkaline solution using pulse radiolysis combined with kinetic spectroscopy. Irradiation of linoleic acid in N/sub 2/O/O/sub 2/-saturated solutions leads to a mixture of peroxyl radical isomers; reaction of 13-hydroperoxylinoleic acid (13-LOOH) with azide radicals in N/sub 2/O-saturated solution produces 13-LOO radicals specifically. These peroxyl radicals cannot be observed directly, but their reactions with kaempferol and quercetin, acting as radical-scavenging antioxidants, produced strongly absorbing aroxyl radicals (ArO). The same aroxyl radicals were generated by OH and N/sub 3/ with rate constants exceeding 10/sup 9/ dm/sup 3/ mol/sup -1/ s/sup -1/. Applying a reaction scheme that includes competing generation and decay reactions of both LOO and ArO radicals, individual rate constants were derived for LOO reactions with the phenols (> 10/sup 7/ dm/sup 3/ mol/sup -1/ s-./sup 1/), with aroxyl radicals to form covalent adducts (> 10/sup 8/ dm/sup 3/ mol/sup -1/ s/sup -1/), as well as for their bimilecular decay (3.0 x 10/sup 8/ dm/sup 3/ mol/sup -1/ s/sup -1/). These results demonstrate high reactivity of fatty acid peroxyl radicals and flavone antioxidants in aqueous solution.

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

1987-09-01

35

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

International Nuclear Information System (INIS)

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 CH2CHCOOH radical; and those in iminodiacetic acid hydrochloride and N-(2-hydroxyethyl) iminodiacetic acid powders to the HNCHCH2(CO OH)2 and HOCH2CH2NCHCH2(CO OH)2, respectively. The g-values of the radicals and the hyperfine structure constants of the free electron with the environmental protons and 14N 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)

36

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

37

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

38

ESR studies of radiation induced radical products from linoleic acid and linolenic acid and the radioprotective effect by ?-tocopherol  

International Nuclear Information System (INIS)

Primary radicals from the ?-radiolysis of air-saturated linoleic acid and linolenic acid at 77 K, and the subsequent secondary radicals appeared during the course of variable temperature elevation were investigated by ESR. The ESR spectrum from samples irradiated and observed at 77 K shows the presence of the radical anion doublet arise from the electron adducts of the carboxy groups and the poorly resolved broad singlet results from some carbon-centered radicals. Annealing to approximately 125 K which allows for molecular oxygen migration results in the formation of peroxyl radicals. At 247 K, the ESR spectrum is a multi-line pattern which is attributable to structure of the ?-carbon radical superimposed on the pentadienyl radicals. The ESR spectra from linoleic acid-?-tocopherol and linolenic acid-?-tocopherol binary systems irradiated at 77 K and recorded at 140 K or 215 K revealed the characteristic similarity to that from ?-tocopherol alone, no trace of ESR signal from either peroxyl or the composite pattern from superposition of pentadienyl radical and ?-carbon radicals can be found out. Therefore ?-tocopherol has exerted radioprotection effect on peroxidation of linoleic acid and linolenic acid

39

Antioxidant activity measured in different solvent fractions obtained from Mentha spicata Linn.: an analysis by ABTS*+ decolorization assay.  

Science.gov (United States)

Antioxidant compounds are abundantly available in plants and play an important role in scavenging free radicals, thus providing protection to humans against oxidative DNA damage. Mentha spicata Linn., commonly called spearmint, belongs to the family lamiaceae. It was selected in the present study because Mentha extracts have antioxidant properties due to the presence of eugenol, caffeic acid, rosmarinic acid and alpha-tocopherol. Four solvent fractions (hexane, chloroform, ethyl acetate and water) of ethanolic extract of dried leaves powder of M. spicata were analyzed for total antioxidant activity (TAA) and relative antioxidant activity (RAA) and compared with standard antioxidants such as Quercetin, beta-carotene, L-ascorbic acid and glutathione using ABTS*+ decolorization assay (ABTS/Potassium persulphate). The antioxidant activity was assumed to be from the total phenolic content of the ethanolic extract. Total phenolics are found to be highest in ethyl acetate fraction (54 mg/g) and least in hexane fraction (13 mg/g) and more or less similar in water and chloroform fractions (30-32 mg/g). TAA is found to be less in hexane and chloroform fractions (content of total phenolics present in them. PMID:16500887

Arumugam, Ponnan; Ramamurthy, Perumal; Santhiya, Sathiyavedu Thyagarajan; Ramesh, Arabandi

2006-01-01

40

A pulse radiolysis study of the OH radical induced autoxidation of methanesulfinic acid  

DEFF Research Database (Denmark)

Methanesulfinic acid, CH3SO2H, reacts with OH radicals at pH 7 forming CH3SO2 radicals with a rate constant k = (6.0 +/- 1.0) x 10(9) M(-1) s(-1). The CH3SO2 radical absorbs at 325 nm with an extinction coefficient of 900 +/- 100 M(-1) cm(-1) and disappears in a second order self-reaction with k = (1.0 +/- 0.2) x 10(9) M(-1) s(-1). This radical reacts with oxygen, k = (1.2 +/- 0.3) x 10(9) M(-1) s(-1), forming a peroxy radical which absorbs in the UV below 300 nm. The peroxy radical reacts in turn with methanesulfinic acid reforming the CH3SO2 radical whereby a chain oxidation of sulfinic acid takes place. During the course of the chain oxidation a peroxyacid, presumably methaneperoxymonosulfonic acid, is formed and accumulated. This acid absorbs in the UV and eventually decays by reaction with excess methanesulfinic acid k = 5 x 10(3) M(-1) s(-1). The final product of the chain autoxidation is methanesulfonic acid. The chain is very efficient and proceeds until either oxygen or methanesulfinic acid is exhausted. The mechanism is compared to the chain autoxidation of sulfite.

Sehested, K.; Holcman, J.

1996-01-01

41

A pulse radiolysis study of the OH radical induced autoxidation of methanesulfinic acid  

International Nuclear Information System (INIS)

Methanesulfinic acid, CH3SO2H, reacts with OH radicals at pH 7 forming CH3SO2 radicals with a rate constant k = (6.0 ± 1.0) x 109 M-1 s-1. The CH3SO2 radical absorbs at 325 nm with an extinction coefficient of 900 ± 100 M-1 cm-1 and disappears in a second order self-reaction with k (1.0 ± 0.2) x 109 M-1s-1. This radical reacts with oxygen, k = (1.2 ± 0.3) x 109 M-1 s-1, forming a peroxy radical which absorbs in the UV below 300 nm. The peroxy radical reactions in turn with methanesulfinic acid reforming the CH3SO2 radical whereby a chain oxidation of sulfinic acid takes place. During the course of the chain oxidation a peroxyacid, presumably methaneperoxymonosulfonic acid, is formed and accumulated. This acid absorbs in the UV and eventually decays by reaction with excess methanesulfinic acid k = 5 x 103 M-1 s-1. The final product of the chain autooxidation is methanesulfonic acid. The chain is very efficient and proceeds until either oxygen or methanesulfinic acid is exhausted. The mechanism is compared to the chain autooxidation of sulphite. (author)

42

Parabanic acid for monitoring of oxygen radical activity in the injured human brain.  

Science.gov (United States)

The authors used intracerebral microdialysis to harvest allantoin and parabanic acid, potential markers of in vivo oxygen radical activity, from the frontal lobe cortex of three patients in the neurointensive care unit after serious aneurysmal subarachnoid haemorrhage. Clinical events involving severe secondary ischaemia, ultimately leading to structural damage, were associated with a dramatic elevation of the microdialysate level of parabanic acid, whereas allantoin showed less robust changes. In one patient with an uneventful clinical course and without signs of secondary ischaemia parabanic acid levels remained low. The results support the involvement of highly reactive oxygen radical species in human cerebral ischaemia. Parabanic acid appears to be an important marker of free radical reactions in vivo and may be used to monitor free radical activity and to evaluate pharmacological therapy with radical scavengers. PMID:8541489

Hillered, L; Persson, L

1995-09-11

43

Test for antioxidant ability by scavenging long-lived mutagenic radicals in mammalian cells and by blood test with intentional radicals: an application of gallic acid  

OpenAIRE

Antioxidant ability of gallic acid (GA) are determined both by electron spin resonance measurement of long-lived radicals produced in gamma-ray irradiated Syrian golden hamster embryo cells with GA and by hemolysis measurement with GA when blood cells are submitted to radicals. Scavenging properties of GA are determined by the reaction rate constant with long-lived mutagenic radicals in the cells while the blood test allows to analyze the global effects of this compound: radical scavenger + m...

Kumagai, Jun; Kawaura, Tomoko; Miyazaki, Tetsuo; Prost, Michel; Prost, Emmanuelle; Watanabe, Masami; Quetin-leclercq, Joe?lle

2003-01-01

44

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)

45

Comparison of a novel extraction-based colorimetric (ABTS) method with membrane introduction mass spectrometry (MIMS): trichloramine dynamics in pool water.  

Science.gov (United States)

Trichloramine is a hazardous disinfection by-product, which is present in chlorinated swimming pools. Although it is primarily taken up by inhalation, the concentration in pool water is important to monitor pool water quality and to assess trichloramine mitigation strategies. To date, scarce data is available on trichloramine concentration in pool water due to the lack of a suitable and easily applicable analytical method. This study presents a novel low cost, colorimetric method which is easy to operate and suitable for on-site measurements of trichloramine concentrations ?0.05 ?M (?0.01 mg L(-1) as Cl2). The analytical method (termed "extraction-based ABTS method") consists of, (i) trichloramine stripping from pool water samples, (ii) passing it through a solid phase filter, composed of silica gel impregnated with sulfamic acid to eliminate interferences and (iii) trichloramine reaction with the indicator 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) to produce the coloured ABTS(•-) radical, which is measured at ? = 405 nm to determine the trichloramine concentration in the pool water sample. A comparison of the extraction-based ABTS method with membrane introduction mass spectrometry (MIMS) for 28 pool samples revealed a good correlation of the two methods. The trichloramine concentration in pool samples is correlated to HOCl, which is the most important factor for its formation. Other parameters such as combined chlorine and pH play a minor role while no correlation between trichloramine and the urea or the TOC concentration was observed. On-site measurements with MIMS in a wading pool over 6 days with a time resolution of 1 h confirmed that trichloramine concentrations strongly responded to changes in free chlorine concentrations. A diurnal measurement of trichloramine with a time resolution of 20 min revealed that trichloramine concentrations reacted quickly and sensitively to the bather load and that urea is probably not the main precursor for its formation. PMID:24769062

Soltermann, Fabian; Widler, Tobias; Canonica, Silvio; von Gunten, Urs

2014-07-01

46

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

47

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

48

Inhibitory activity of natural occurring antioxidants on Thiyl radical-induced trans-arachidonic acid formation.  

Science.gov (United States)

trans-Fatty acids in humans not only may be obtained exogenously from food intake but also could be generated endogenously in tissues. The endogenous generation of trans-fatty acids, especially in the cell membranes induced by radical stress, is an inevitable source for the living species. Thiyl radicals generated from thiols act as the catalyst for the cis-trans isomerization of fatty acids. Arachidonic acid (5c,8c,11c,14c-20:4) with only two of the four double bonds deriving from linoleic acid in the diet can be used to differentiate the exogenous or endogenous formation of double bonds. The aim of this study is to evaluate the effective compounds in preventing thiyl radical-induced trans-arachidonic acid formation during UV irradiation in vitro. The trans-arachidonic acids were found to be 75% after 30 min UV irradiation of all-cis-arachidonic acid. Myricetin, luteolin, and quercetin had the highest thiyl radical scavenging activities, whereas sesamol, gallic acid, and vitamins A, C, and E had the lowest. The structures of flavonoids with higher thiyl radical scavenging activities were a 3',4'-o-dihydroxyl group in the B ring and a 2,3-double bond combined with a 4-keto group in the C ring. These effective compounds found in the present work may be used as lead compounds for the potential inhibitors in the formation of trans-fatty acids in vivo. PMID:21291247

Hung, Wei-Lun; Ho, Chi-Tang; Hwang, Lucy Sun

2011-03-01

49

Oxidation of carboxylic acids regenerates hydroxyl radicals in the unpolluted and nighttime troposphere.  

Science.gov (United States)

The hydroxyl radical (OH) controls the removal of organic compounds from the troposphere. Atmospheric chemistry models significantly under-predict OH levels in unpolluted environments, implying that they are regenerated via some unknown mechanism(s). This work uses computational chemistry to demonstrate that the photochemical oxidation of alkyl carboxylic acids can efficiently regenerate the hydroxyl radical via unimolecular decomposition of alpha-carboxyalkylperoxy radicals. For acetic acid and propanoic acid the proposed mechanism is predicted to dominate in the unpolluted lower troposphere, and it may also operate to some extent in the mid to upper troposphere. Alkyl carboxylic acids are also predicted to act as a new source of nighttime OH throughout the planetary boundary layer, where OH levels are also under-predicted. The thermodynamic requirements for reactions of this class are discussed, and some candidate OH-reforming molecules particularly relevant to aromatic photooxidation are identified. Adopting a broader perspective, the alpha-carboxyalkyl radical precursors that react with O(2) to form the unstable alpha-carboxyalkylperoxy type radicals are also expected to form during combustion, in the interstellar medium, and from the gamma-irradiation of glycine and related amino acids, and the potential importance of this new chemistry in these environments is discussed. Master equation simulations suggest that alpha-carboxyalkyl + O(2) reactions provide a prompt OH source during the autoignition and combustion of biodiesel and other oxygenated biofuels, where carboxylic acids are formed as early stage oxidation products. Ketene combustion is also thought to proceed via these OH-reforming alpha-carboxyalkyl radicals. The in vivo formation of alpha-carboxyalkylperoxy radicals followed by oxidation to the highly reactive OH radical may induce oxidative stress in the human body, in a process initiated by gamma-rays. Finally, the reaction of ketenes with OH to form alpha-carboxyalkyl radicals, followed by addition of NH(2) or related species, is suggested as a new extraterrestrial pathway to amino acids. PMID:20533840

da Silva, Gabriel

2010-07-01

50

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

51

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

52

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

International Nuclear Information System (INIS)

Molecular orbital calculation and pulse radiolysis method are combined in the studies of interaction of caffeic acid with eaq-, (CH3)2(OH)CCH2., CO2.-, H., ·OH and N3. radicals. Reaction rate constants, UV-visible spectra of electron|·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)

53

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

Science.gov (United States)

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 aq- and ·OH tend to form adducts with caffeic acid, while N 3rad 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 caffeic ions, in good agreement with their experimental second-order decay rate constants (2 k=(1.1±0.2)×10 9, (6.0±0.4)×10 7 and (2.0±0.2)×10 7 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.

Li, Xifeng; Cai, Zhongli; Katsumura, Yosuke; Wu, Guozhong; Muroya, Yusa

2001-01-01

54

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)

55

Free radicals produced by the oxidation of gallic acid: An electron paramagnetic resonance study  

OpenAIRE

Abstract Background Gallic acid (3,4,5-trihydroxybenzoic acid) is found in a wide variety of plants; it is extensively used in tanning, ink dyes, as well as in the manufacturing of paper. The gallate moiety is a key component of many functional phytochemicals. In this work electron paramagnetic spectroscopy (EPR) was used to detect the free radicals generated by the air-oxidation of gallic acid. Results We found that gallic acid produces two different radicals as a function of pH. In the pH r...

Wagner Brett A; Pasanphan Wanvimol; Eslami Angelique C; Buettner Garry R

2010-01-01

56

Distribution of stable free radicals among amino acids of isolated soy proteins.  

Science.gov (United States)

Application of deuterium sulfide to powdered isolated soy proteins (ISP) was used to quench stable free radicals and produce a single deuterium label on amino acids where free radicals reside. The deuterium labels rendered increases of isotope ratio for the specific ions of radical-bearing amino acids. Isotope ratio measurements were achieved by gas chromatography/mass spectrometry (GC/MS) analyses after the amino acids were released by acidic hydrolysis and converted to volatile derivatives with propyl chloroformate. The isotope enrichment data showed the stable free radicals were located on Ala, Gly, Leu, Ile, Asx (Asp+Asn), Glx (Glu+Gln), and Trp but not on Val, Pro, Met, Phe, Lys, and His. Due to the low abundance of Ser, Thr, and Cys derivatives and the impossibility to accurately measure their isotope ratios, the radical bearing status for these amino acids remained undetermined even though their derivatives were positively identified from ISP hydrolysates. The relative isotope enrichment for radical-bearing amino acids Ala, Gly, Leu, Ile, Asx (Asp+Asn), Glx (Glu+Gln), and Trp were 8.67%, 2.96%, 2.90%, 3.94%, 6.03%, 3.91%, and 21.48%, respectively. Isotope ratio increase for Tyr was also observed but further investigation revealed such increase was mainly from nonspecific deuterium-hydrogen exchange not free radical quenching. The results obtained from the present study provide important information for a better understanding of the mechanisms of free radical formation and stabilization in "dry" ISP. PMID:21535530

Lei, Qingxin; Liebold, Christopher M; Boatright, William L; Shah Jahan, M

2010-09-01

57

Enhancement of carboxylic acid degradation with sulfate radical generated by persulfate activation.  

Science.gov (United States)

The aim of this work was to investigate the generation of sulfate radical for the removal of two carboxylic acids in aqueous solution: acetic and citric acids. From photochemical and radiolytic processes, kinetics of the degradation of these two carboxylic acids was studied as a function of the pH of the solution. It was shown that the maximum of acetic acid degradation occurred at pH 5. Above this pH, competitive reactions with the carbon mineralized inhibit the reaction of with the solute. In the case of citric acid, pH has only a little effect on the kinetic of citric acid degradation. The determination of mineralization yields shows several differences depending on carboxylic acids and pH. The degradation of both carboxylic acids was also studied in the radiolysis process whether with or without persulfate addition. A comparison of the processes of sulfate radical production is presented. PMID:20220244

Criquet, J; Nebout, P; Karpel Vel Leitner, N

2010-01-01

58

Radical para-benzoic acid derivatives: transmission of ferromagnetic interactions through hydrogen bonds at long distances.  

Science.gov (United States)

Investigation of the transmission of magnetic interactions through hydrogen bonds has been carried out for two different benzoic acid derivatives which bear either a tert-butyl nitroxide (NOA) or a poly(chloro)triphenylmethyl (PTMA) radical moiety. In the solid state, both radical acids formed dimer aggregates by the complementary association of two carboxylic groups though hydrogen bonding. This association ensured that atoms with most spin density are separated from one another by more than 15 A. Thus, no competing through-space magnetic exchange interactions are expected in these dimers and, hence, they provide good models to investigate whether noncovalent hydrogen bonds play a role in the long-range transmission of magnetic interactions. The nature of the magnetic exchange interaction and their strengths within similar dimer aggregates in solution was assessed by electron spin resonance (ESR) spectroscopy. In the case of radical NOA, low-temperature ESR experiments showed a weak ferromagnetic interaction between the two radicals in the dimer aggregates (which have the same geometry as in the solid state). In contrast, the corresponding solution ESR study performed with radical PTMA did not lead to any conclusive results, as aggregates were formed by noncovalent interactions other than hydrogen bonds. However, the bulkiness of the poly(chloro)triphenylmethyl radical prevented interdimer contacts in the solid state between regions of high spin density. Hence, solid-state measurements of the alpha phase of PTMA radical provided evidence of the intradimer interaction to confirm the transmission of a weak ferromagnetic interaction through the carboxylic acid bridges, as found for the NOA radical. Moreover, crystallization of the PTMA radical in presence of ethanol to form the beta phase of PTMA radical prevented the dimer formation; this resulted in the suppression of this interaction and provides further evidence of the magnetic exchange mechanism through noncovalent hydrogen bonds at long distances. PMID:12203290

Maspoch, Daniel; Catala, Laure; Gerbier, Philippe; Ruiz-Molina, Daniel; Vidal-Gancedo, José; Wurst, Klaus; Rovira, Concepció; Veciana, Jaume

2002-08-16

59

Facile csp(2)-csp(2) bond cleavage in oxalic Acid-derived radicals.  

Science.gov (United States)

Oxalate decarboxylase (OxDC) catalyzes the Mn-dependent conversion of the oxalate monoanion into CO2 and formate. Many questions remain about the catalytic mechanism of OxDC although it has been proposed that the reaction proceeds via substrate-based radical intermediates. Using coupled cluster theory combined with implicit solvation models we have examined the effects of radical formation on the structure and reactivity of oxalic acid-derived radicals in aqueous solution. Our results show that the calculated solution-phase free-energy barrier for C-C bond cleavage to form CO2 is decreased from 34.2 kcal/mol for oxalic acid to only 9.3 kcal/mol and a maximum of 3.5 kcal/mol for the cationic and neutral oxalic acid-derived radicals, respectively. These studies also show that the C-C ? bonding orbital of the radical cation contains only a single electron, giving rise to an elongated C-C bond distance of 1.7 Å; a similar lengthening of the C-C bond is not observed for the neutral radical. This study provides new chemical insights into the structure and stability of plausible intermediates in the catalytic mechanism of OxDC, and suggests that removal of an electron to form a radical (with or without the concomitant loss of a proton) may be a general strategy for cleaving the unreactive C-C bonds between adjacent sp(2)-hybridized carbon atoms. PMID:25702589

Molt, Robert W; Lecher, Alison M; Clark, Timothy; Bartlett, Rodney J; Richards, Nigel G J

2015-03-11

60

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

61

Reaction of thiyl radicals with alcohols, ethers and polyunsaturated fatty acids: A possible role of thiyl free radicals in thiol mutagenesis?  

International Nuclear Information System (INIS)

Possible reactions of thiyl free radicals in biological environment are reviewed. In particular hydrogen transfer processes from model C-H compounds like alcohols and ethers as well as from polyunsaturated fatty acids to thiyl radicals are described to proceed with reasonably high rate constants (103-104 and 106-107 M-1 s-1, respectively). Thiyl radicals have thus to be considered as potentially hazardous species especially with respect to DNA damage and lipid peroxidation. (orig.)

62

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)

63

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

Scientific Electronic Library Online (English)

Full Text Available 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

64

A clean and selective radical homocoupling employing carboxylic acids with titania photoredox catalysis.  

Science.gov (United States)

A titania photoredox catalysis protocol was developed for the homocoupling of C-centered radicals derived from carboxylic acids. Intermolecular reactions were generally efficient and selective, furnishing the desired dimers in good yields under mild neutral conditions. Selective cross-coupling with two acids proved unsuccessful. An intramolecular adaptation enabled macrocycles to be prepared, albeit in modest yields. PMID:25290736

Manley, David W; Walton, John C

2014-10-17

65

Peculiar stability of amino acids and peptides from a radical perspective.  

Science.gov (United States)

Photochemical reactions of free and N-acetyl alpha-amino acids with chlorine and deuterium labeled hydrogen peroxide have been used to determine both the relative rates of reaction of molecules of these classes and the relative reactivity of their different types of hydrogen toward abstraction by chlorine and oxygen centered radicals. The relative rates of reaction of these species range over more than 3 orders of magnitude; however, where data are available from more than one amino acid for a particular type of group at a specific position on the side chain, the values are remarkably similar. The predictive utility of these results has been demonstrated for the regioselective chlorination of tripeptides. More generally this analysis shows that the backbone and adjacent side chain positions of amino acids and peptides are peculiarly resistant to hydrogen atom transfer, and a similar pattern of reactivity has been noted from earlier studies of reactions of modified substrates catalyzed by isopenicillin-N-synthetase. Such resistance stands out in contrast to the common occurrence of free radical reactions of alpha-amino acids, peptides, and proteins and their importance in biology. Nevertheless, it provides a reason for the ability of amino acids and their derivatives to avoid degradation in Nature where they are constantly exposed to radicals, and it accounts, at least in part, for the anomalous ability of enzymes to catalyze free radical reactions without being broken down by the radical intermediates. PMID:19630427

Watts, Zachary I; Easton, Christopher J

2009-08-19

66

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

OpenAIRE

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 t...

Leifer Nicole; Wimmer Eckard; Mueller Steffen; Cohn Corey A; Greenbaum Steven; Strongin Daniel R; Aa, Schoonen Martin

2006-01-01

67

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

68

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

69

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.

70

Complexation of allyl radicals and hydrochloric Acid in helium nanodroplets.  

Science.gov (United States)

Infrared spectra of the allyl radical-HCl complex in superfluid helium nanodroplets have been recorded in the IR frequency range of 2750-3120 cm(-1). Six fundamental bands were observed, five of which have been assigned to the C-H stretch vibrations of the allyl radical. No additional CH bands were observed upon the binding of HCl. The band at 2800.3 cm(-1) can unambiguously be assigned to the bound HCl stretch, which is red-shifted by 106 cm(-1) compared to that of the free HCl. Stark spectra and pickup curves were recorded and support our assignment. In accompanying ab initio calculations, we found four equivalent minima and computed a two-dimensional potential energy surface for the HCl positioning on the allyl radical plane at the CCSD(T)/TZVPP level. Based on our findings, we conclude that the ground-state structure of the complex shows two energetically equivalent T-shaped minimum structures. Because of small barriers between the two minima, a delocalization of the HCl is anticipated. PMID:25597230

Leicht, Daniel; Habig, Daniel; Schwaab, Gerhard; Havenith, Martina

2015-02-12

71

Formation and properties of radicals in ?-irradiated molecular compounds of urea with dicarboxylic acids  

International Nuclear Information System (INIS)

Radiation chemical yields of paramagnetic centres and their nature have been studied as well as secondary reactions in channel inclusion compounds of urea with sebacic acid and in mixed crystals of urea with succinic acid. In inclusion compounds of urea with sebacic acid the yield exceeds additive at 77 K. In mixed crystals of urea with succinic acid the yield at 77 K is equal to additive. In mixed crystals at all temperatures quazistationary concentrations of radicals are lower than in pure succinic acid. In inclusion compounds quazistationary concentration of radicals are higher than in pure sebacic acid. It has been shown that in solid two-component systems, when the nature of the components is identical, the matrix structure exerts an essential influence on the radiolysis of the system

72

Test for antioxidant ability by scavenging long-lived mutagenic radicals in mammalian cells and by blood test with intentional radicals: an application of gallic acid  

Science.gov (United States)

Antioxidant ability of gallic acid (GA) are determined both by electron spin resonance measurement of long-lived radicals produced in ?-ray irradiated Syrian golden hamster embryo cells with GA and by hemolysis measurement with GA when blood cells are submitted to radicals. Scavenging properties of GA are determined by the reaction rate constant with long-lived mutagenic radicals in the cells while the blood test allows to analyze the global effects of this compound: radical scavenger+metal ion chelator+regeneration of intra- and extra-cellular antioxidant.

Kumagai, Jun; Kawaura, Tomoko; Miyazaki, Tetsuo; Prost, Michel; Prost, Emmanuelle; Watanabe, Masami; Quetin-Leclercq, Joëlle

2003-01-01

73

Test for antioxidant ability by scavenging long-lived mutagenic radicals in mammalian cells and by blood test with intentional radicals: an application of gallic acid  

International Nuclear Information System (INIS)

Antioxidant ability of gallic acid (GA) are determined both by electron spin resonance measurement of long-lived radicals produced in ?-ray irradiated Syrian golden hamster embryo cells with GA and by hemolysis measurement with GA when blood cells are submitted to radicals. Scavenging properties of GA are determined by the reaction rate constant with long-lived mutagenic radicals in the cells while the blood test allows to analyze the global effects of this compound: radical scavenger+metal ion chelator+regeneration of intra- and extra-cellular antioxidant

74

Test for antioxidant ability by scavenging long-lived mutagenic radicals in mammalian cells and by blood test with intentional radicals: an application of gallic acid  

Energy Technology Data Exchange (ETDEWEB)

Antioxidant ability of gallic acid (GA) are determined both by electron spin resonance measurement of long-lived radicals produced in {gamma}-ray irradiated Syrian golden hamster embryo cells with GA and by hemolysis measurement with GA when blood cells are submitted to radicals. Scavenging properties of GA are determined by the reaction rate constant with long-lived mutagenic radicals in the cells while the blood test allows to analyze the global effects of this compound: radical scavenger+metal ion chelator+regeneration of intra- and extra-cellular antioxidant.

Kumagai, Jun E-mail: kumagai@apchem.nagoya-u.ac.jp; Kawaura, Tomoko; Miyazaki, Tetsuo; Prost, Michel; Prost, Emmanuelle; Watanabe, Masami; Quetin-Leclercq, J.Joeelle

2003-01-01

75

Formation and reactivity of vinylperoxyl radicals in aqueous solutions  

Energy Technology Data Exchange (ETDEWEB)

Vinyl, carboxyvinyl and dicarboxyvinyl radicals were produced in irradiated aqueous solutions from acetylene and acetylenecarboxylic and acetylenedicarboxylic acid by addition of H atom to the triple bond or by reaction with e{sub aq}{sup -}, followed by protonation. Vinyl and phenylvinyl radicals were produced by reductive dehalogenation of vinyl bromide and {beta}-bromostyrene with e{sub aq}{sup -}. All these vinyl radicals react rapidly with oxygen to produce the corresponding vinylperoxyl radicals. Vinylperoxyl radicals exhibit optical absorptions in the UV ({lambda}{sub max} 250-290 nm) and in the visible range. The peaks in the visible range were at 440 nm for unsubstituted vinylperoxyl radical, between 480 and 520 nm for carboxylated vinylperoxyl, depending on pH and number of carboxyl groups, and at 540 and 690 nm for (2-phenylvinyl)peroxyl. These vinylperoxyl radicals oxidize organic reductants such as 2,2`azinobis(3-ethylbenzothiazoline-6-sulfonate ion) (ABTS), chlorpromazine, ascorbate, and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox C) with rate constants between 4 x 10{sup 5} and 2 x 10{sup 9} L mol{sup -1} s{sup -1}, depending on the radical and the reductant. Vinylperoxyl radicals are more reactive than similarly substituted alkylperoxyl. 20 refs., 5 figs., 1 tab.

Khaikin, G.I.; Neta, P. [National Inst. of Standards and Technology, Gaithersburg, MD (United States)

1995-03-30

76

ESR studies of barriers to ring inversion in cyclic monocarboxylic acid radicals  

Science.gov (United States)

Activation energies for ring inversion have been estimated for a number of cyclic monocarboxylic acid radicals, of structure (CH2)n??COOH (I) with n=3,4, and 5, using electron spin resonance (ESR) methods. These radicals were produced from the corresponding cyclic monocarboxylic acids, by ? irradiation (at 195 K) and subsequent annealing. The ESR spectra of these radicals vary with temperature. The variations are attributed to ring inversion of the cyclic group in these radicals. Computer simulations of the temperature dependent ESR spectra were employed using the solutions of modified Bloch equations for a two-jump process. From these simulations the rate of ring inversion (?) as well as the ESR parameters were estimated as a function of temperature (T). Arrhenius parameters found for the ring inversion in cyclohexane carboxylic acid radical (i.e., I with n=5) are Ea=4.0±0.3 kcal/mol and ln(1/?0) =29.0±0.7 (?0 in sec). The radical species with five-membered ring (n=4) was studied in a number of matrices: (i) sodium cyclopentane carboxylate, (ii) 12M LiCl(D2O), (iii) 8M NaOD, (iv) cycloleucine and (v) cyclopentane carboxylic acid. In the last two matrices, the five-membered ring was found to have twisted configuration yielding four nonequivalent ?-proton splittings. In the other matrices a symmetrical configuration was found revealing two pairs of equivalent splittings. The barrier (Ea) to ring inversion for this radical (n=4) varies only slightly (from 1 to 1.5 Kcal/mole) in different matrices.

Suryanarayana, D.; Sevilla, M. D.

1980-01-01

77

Concerted effects in the reaction of ·OH radicals with aromatics: radiolytic oxidation of salicylic acid  

International Nuclear Information System (INIS)

Liquid chromatographic and capillary electrophoretic studies have been used to resolve the products produced in the radiolytic oxidation of salicylic acid in aqueous solution. These studies have shown that, as in the case of phenol, ·OH radicals preferentially add to the positions ortho and para to the OH substituent. However, in contrast to its reaction with phenol, addition at the ortho position is favored over addition at the para position. Because ·OH radical is a strong electrophile this difference suggests that the electron population at the ortho position in the salicylate anion is enhanced as a result of the hydrogen bonding in salicylic acid

78

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

Science.gov (United States)

Radicals and radical ions formed on ?-radiolysis of aromatic carboxylic acids containing a thioether group in the polycrystalline state at 77 K and on subsequent warming over the temperature range of 95-293 K were identified using the electron spin resonance technique. In all carboxylic acids studied, monomeric sulfur radical cations (X-S rad + -Y-COOH) and radical anions formed by an addition of an electron to the carboxyl group (X-S-Y-COOH) rad - were detected at 95 K. On further warming over the 150-293 K range various S-centered radicals (XS rad ) 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.

Strzelczak, Graz?yna; Korzeniowska-Sobczuk, Anna; Bobrowski, Krzysztof

2005-02-01

79

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

Energy Technology Data Exchange (ETDEWEB)

Radicals and radical ions formed on {gamma}-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{sup +}-Y-COOH) and radical anions formed by an addition of an electron to the carboxyl group (X-S-Y-COOH){sup -} 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 {gamma}-radiation.

Strzelczak, Grazyna [Department of Radiation Chemistry and Technology, Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195 Warsaw (Poland); Korzeniowska-Sobczuk, Anna [Department of Radiation Chemistry and Technology, Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195 Warsaw (Poland); Bobrowski, Krzysztof [Department of Radiation Chemistry and Technology, Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195 Warsaw (Poland)]. E-mail: kris@orange.ichtj.waw.pl

2005-02-01

80

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

81

Interaction between fulvic acids of different origins and active oxygen radicals.  

Science.gov (United States)

Using the spin trapping technique, the interaction between fulvic acids (FAs) of different origins and the active oxygen radicals was studied. The active oxygen radicals under study included superoxide anion (O2.-) produced by xanthine oxidase (XOD) and stimulated polymorphonuclear leukocytes (PMN) of human being and hydroxyl radical (.OH) produced from Fenton's reaction. It has been found that the FAs from both Kaschin-Beck disease (KBD) region and non-KBD region can accelerate the production of .OH and scavenge O2.-. FA from peat can scavenge both O2.- and .OH. The results show that the behavior of KBD and non-KBD FAs differs clearly from peat FA. It has been concluded that the superoxidation damage of KBD induced by FA is mainly due to hydroxyl radical reaction initiated in biological system. PMID:8760456

Wang, C; Wang, Z; Peng, A; Hou, J; Xin, W

1996-06-01

82

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

83

Reactions of H atoms and OH radicals with ascorbic acid. A pulse radiolysis Fourier transform ESR study  

International Nuclear Information System (INIS)

Using pulse radiolysis, free radicals of ascorbic acid were generated by reactions of the primary radicals H and OH in acidic and basic aqueous solutions. The formation and the decay of several radicals of ascorbic acid were detected by time resolved Fourier transform electron spin resonance within a time interval of 100 ns to 1 ms. The rate constant of addition of H atoms to ascorbic acid (1.3 x 108 dm3 x mol-1 x s-1) was directly determined by the change of line width of the low field line of the H atom in the presence of ascorbic acid. The addition of OH radicals to ascorbic acid results in different radical structures, detected by highly resolved Fourier transform ESR spectra. (author)

84

Kinetics and Products of Heterogeneous Oxidation of Oleic acid, Linoleic acid and Linolenic acid in Aerosol Particles by Hydroxyl radicals  

Science.gov (United States)

A significant mass fraction of atmospheric aerosols is composed of a variety of oxidized organic compounds with varying functional groups that may affect the rate at which they chemically age. Here we study the heterogeneous reaction of OH radicals with different sub-micron, alkenoic acid particles: Oleic acid (OA), Linoleic acid (LA), and Linolenic acid (LNA), in the presence of H2O2 and O2. This research explores how OH addition reactions initiate chain reactions that rapidly transform the chemical composition of an organic particle. Particles are chemically aged in a photochemical flow tube reactor where they are exposed to OH radicals (~ 1011 molecule cm-3 s) that are produced by the photolysis of H2O2 at 254 nm. The aerosols are then sized and their composition analyzed via Atmospheric Pressure Chemical Ionization (APCI). Detailed kinetic measurements show that the reactive uptake coefficient is larger than 1, indicating the presence of secondary chemistry occurring in the condensed phase. Reactive uptake coefficient is found to scale linearly with the number of double bonds present in the molecule. In addition, the reactive uptake coefficient is found to depend sensitively upon the concentrations of O2 in the photochemical flow tube reactor, indicating that O2 plays a role in secondary chemistry. In the absence of O2 the reactive uptake coefficient increases to ~ 8, 5 and 3 for LNA, LA, and OA, respectively. The reactive uptake coefficient approaches values of 6, 4 and 2 for LNA, LA, and OA respectively when 18% of the total nitrogen flow is replaced with O2. Mechanistic pathways and products will also be presented herein.

Nah, T.; Leone, S. R.; Wilson, K. R.

2010-12-01

85

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

86

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

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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

87

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)

88

Free radicals produced during the oxidation of hydrazines by hypochlorous acid.  

Science.gov (United States)

Hypochlorous acid (HOCl) derived from activated neutrophils and monocytes has been implicated in the activation of hydrazine-containing drugs to toxic intermediates. However, reactive intermediates formed during the reaction between HOCl and these drugs have not been identified. We investigated the oxidation of the hydrazine derivatives isoniazid, iproniazid, and hydralazine by HOCl. The reaction between HOCl and all three hydrazines resulted in O2 consumption, indicating that free radicals were produced, but the rate and extent of O2 consumption were different for each hydrazine. Moreover, reduction of nitroblue tetrazolium (NBT) was observed only during the reaction between HOCl and isoniazid, suggesting that different radical species may be produced from HOCl reaction with each hydrazine. The oxidation of iproniazid by HOCl in the presence of the radical trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) resulted in the formation of a carbon-centered radical adduct. In contrast, the reaction between HOCl and hydralazine resulted in the formation of a nitrogen-centered DMPO radical adduct. The oxidation of isoniazid by HOCl resulted in the formation of two oxygen-centered radical adducts, DMPO-OOH and DMPO-OH. Myeloperoxidase-catalyzed oxidation of these hydrazines in the presence of Cl- and H2O2 produced radical species that were identical to those observed with HOCl. Thus, some of the toxic side effects of these drugs may be the result of the production of free-radical intermediates from reaction with neutrophil-derived oxidants, such as HOCl. The types of radicals produced and the consequences of generating these reactive species are discussed. PMID:8951237

Goodwin, D C; Aust, S D; Grover, T A

1996-12-01

89

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

90

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

91

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

92

Effect of water and ethanol radicals on the protein part of human hemoglobin. Pt. 2. Damage to amino acid residues  

International Nuclear Information System (INIS)

This work is devoted to the effect of interactions of water and ethanol radicals with human hemoglobin (Hb) amino acid residues. The OH radicals caused the greatest destruction of human hemoglobin amino acid residues. Among them the most sensitive to irradiation were cysteine tryptophan and histidine residues. (author). 11 refs, 2 tabs

93

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

94

Radical chromatography of spin adducts produced from ?-irradiated linoleic acid in nonaqueous solution  

International Nuclear Information System (INIS)

Spin adducts produced from ?-irradiated linoleic acid in an ethanol solution containing 2-methyl-2-nitrosopropane could be separated into nine fractions with high performance liquid chromatography. Distinct ESR spectra were observed from seven fractions and radical structures were identified for two major components. (author)

95

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

96

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

97

Radical scavenging capacity of Agrimonia eupatoria and Agrimonia procera.  

Science.gov (United States)

The antioxidant activity of Agrimonia eupatoria (Agrimony) and Agrimonia procera (Fragrant agrimony) extracts was assessed by measuring in DPPH radical scavenging and ABTS(+) radical decolourisation reaction systems. Radical scavenging capacity of agrimony extracts varied in a wide range (9.1-97.5% in DPPH reaction and 6.7-79.5% in ABTS reaction) depending on the polarity of the solvent used to obtain the extract. PMID:17215090

Venskutonis, P R; Skemaite, M; Ragazinskiene, O

2007-02-01

98

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

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Full Text Available Previous experiments have demonstrated that the aqueous OH radical oxidation of methylglyoxal produces low volatility products including pyruvate, 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 plays a central role in the aqueous oxidation of methylglyoxal and it is a ubiquitous product of gas phase photochemistry, making it a potential "aqueous" SOA precursor in its own right. However, the fate of acetic acid upon aqueous-phase oxidation is not well understood. In this research, acetic acid (20 ?M–10 mM was oxidized by OH radicals, and pyruvic acid and methylglyoxal experimental samples were analyzed using new analytical methods, in order to better understand the formation of SOA from acetic acid and methylglyoxal. Glyoxylic, glycolic, and oxalic acids formed from acetic acid and OH radicals. In contrast to the aqueous OH radical oxidation of methylglyoxal, the aqueous OH radical oxidation of acetic acid did not produce succinic acid and oligomers. This suggests that the methylgloxal-derived oligomers do not form through the acid catalyzed esterification pathway proposed previously. Using results from these 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.

Y. Tan

2012-01-01

99

Effect of tocopherol treatment on deterioration of edible oil quality (acid value, carbonyl value, free fatty acid and radical activity).  

Science.gov (United States)

In this study, waste edible oil was prepared by both heat and aeration treatment, and the increasing inhibitive effect of tocopherol treatment on the acid value (AV) and carbonyl value (CV) of the oil was investigated. The AV and CV of waste edible oil treated with tocopherol were 0.1-1.0% lower than those of the nontreated oil, indicating that tocopherol exerted a radical-scavenging activity. The concentration of tocopherol decreased with time, while that of the remaining 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals increased. These results suggest that the addition of tocopherol proved to be useful for preventing the deterioration of waste edible oil. PMID:24420062

Ogata, Fumihiko; Tanaka, Yuko; Kawasaki, Naohito

2014-01-01

100

Identification of products from oxidation of uric acid induced by hydroxyl radicals.  

Science.gov (United States)

The aim of the present study was to separate and characterise products formed by oxidation of uric acid by hydroxyl radicals with a view to probing for these products in vivo in clinical contexts. Aerated solutions of 200 microM uric acid, or its oxidation products, allantoin or parabanic acid, were exposed to gamma radiolysis, (52.0 Gy/min), as a source of HO. radicals, at pH 3.4 and 7.4. Aliquots were taken every 5 minutes for 20 minutes and oxidation products were separated by HPLC and analysed with a diode array detector. Identities of oxidation products were confirmed on the basis of similarity of retention times and absorbance spectra and peak purity parameters of known standards. Hydroperoxides were measured by tri-iodide formation in the 20 minute sample. Exposure of uric acid to such HO.fluxes produced a net loss of the parent compound with formation of a complex mixture of products with allantoin and parabanic acid being the predominant products at pH 3.4. The rate of uric acid degradation at physiological pH was slower and the distribution of oxidation products was different. A small but significant amount of uric acid hydroperoxide was detected at both pHs. A mechanism for uric acid oxidation under these conditions is presented. PMID:8397146

Hicks, M; Wong, L S; Day, R O

1993-01-01

101

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

102

Performance and penetration of laccase and ABTS inks on various printing substrates.  

Science.gov (United States)

Introduction of an enzyme and a colour-forming reagent into paper enables the development of an authenticity indicator. The purpose of this work was to study the performance of Trametes versicolor laccase, TvL, and ABTS, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) diammonium salt, in various printing substrates when printed with inkjet. The printing substrates included pre-coated mechanical paper additionally coated with PVA, silica and latex. The focus was on the bioanalytical performance and ink penetration. The setting of the printed TvL and ABTS ink was studied visually, with optical and confocal microscopy and with a so-called tape laminating technique. Technical properties of the printing substrates and effect of the surface chemistry were discussed and related to the bioanalytical properties. TvL activity persisted well during the printing. The best colour response was attained using the PVA-coated base paper. The film-forming ability of the PVA was found to be the main contributor to the colour reaction. The uniform, dense and non-porous PVA layer retains the ABTS and TVL molecules on top of the printing substrate. The high local ink concentration on the PVA coating layer combined with the absorptive paper substrate suggests that the PVA film acts as a filtering layer which retains TvL and ABTS molecules in the coating layer but allows most of the ink solvents to penetrate into the paper structure. TvL and ABTS molecules are also trapped in the PVA polymer network due to swelling effect of water. Electrostatic attractions between the PVA and ABTS and TvL molecules do not contribute to the colour reaction. PMID:22051108

Matilainen, Katriina; Hämäläinen, Tiina; Savolainen, Anne; Sipiläinen-Malm, Thea; Peltonen, Jouko; Erho, Tomi; Smolander, Maria

2012-02-01

103

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

104

Effect of oxygen-derived free radicals on arachidonic acid turnover in isolated perfused rat lung  

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Turnover of arachidonic acid in lung was studied by perfusing an isolated and ventilated rat lung in the presence of (/sup 14/C)-arachidonic acid for 30 min. Oxygen-derived free radicals were generated within the pulmonary circulation by the action of xanthine oxidase (XO) (0.1 ..mu../ml) on hypoxanthine (0.1 ..mu..mol/ml). Lung was also preperfused in the presence or absence of superoxide dismutase (SOD) (5 ..mu..g/ml) and catalase (5 ..mu..g/ml) prior to the addition of radiolabeled arachidonic acid and free radical generating system. After the perfusion was over, several biopsies were obtained and phospholipids were extracted and separated from one of the biopsies. Individual phospholipids were compared with known standards and counted for radioactivity. An appreciable amount of radioactivity was found in total phospholipids and in phosphatidyl choline and phosphatidyl inositol fractions in control lungs. Some radioactivity was also noticed in phosphatidyl ethanolamine fraction. The isotopic incorporation was significantly inhibited when lung was perfused in the presence of hypoxanthine and XO. The incorporation of (/sup 14/C)-radioactivity was restored to the control levels when lung was preperfused with SOD and catalase. These results suggest that oxygen radicals inhibit the arachidonic acid turnover in isolated and perfused rat lung.

Jones, R.; Otani, H.; Das, D.K.

1986-05-01

105

Effect of oxygen-derived free radicals on arachidonic acid turnover in isolated perfused rat lung  

International Nuclear Information System (INIS)

Turnover of arachidonic acid in lung was studied by perfusing an isolated and ventilated rat lung in the presence of (14C)-arachidonic acid for 30 min. Oxygen-derived free radicals were generated within the pulmonary circulation by the action of xanthine oxidase (XO) (0.1 ?/ml) on hypoxanthine (0.1 ?mol/ml). Lung was also preperfused in the presence or absence of superoxide dismutase (SOD) (5 ?g/ml) and catalase (5 ?g/ml) prior to the addition of radiolabeled arachidonic acid and free radical generating system. After the perfusion was over, several biopsies were obtained and phospholipids were extracted and separated from one of the biopsies. Individual phospholipids were compared with known standards and counted for radioactivity. An appreciable amount of radioactivity was found in total phospholipids and in phosphatidyl choline and phosphatidyl inositol fractions in control lungs. Some radioactivity was also noticed in phosphatidyl ethanolamine fraction. The isotopic incorporation was significantly inhibited when lung was perfused in the presence of hypoxanthine and XO. The incorporation of (14C)-radioactivity was restored to the control levels when lung was preperfused with SOD and catalase. These results suggest that oxygen radicals inhibit the arachidonic acid turnover in isolated and perfused rat lung

106

Free radicals produced by the oxidation of gallic acid: An electron paramagnetic resonance study  

Science.gov (United States)

Background Gallic acid (3,4,5-trihydroxybenzoic acid) is found in a wide variety of plants; it is extensively used in tanning, ink dyes, as well as in the manufacturing of paper. The gallate moiety is a key component of many functional phytochemicals. In this work electron paramagnetic spectroscopy (EPR) was used to detect the free radicals generated by the air-oxidation of gallic acid. Results We found that gallic acid produces two different radicals as a function of pH. In the pH range between 7-10, the spectrum of the gallate free radical is a doublet of triplets (aH = 1.00 G, aH = 0.23 G, aH = 0.28 G). This is consistent with three hydrogens providing hyperfine splitting. However, in a more alkaline environment, pH >10, the hyperfine splitting pattern transforms into a 1:2:1 pattern (aH (2) = 1.07 G). Using D2O as a solvent, we demonstrate that the third hydrogen (i.e. aH = 0.28 G) at lower pH is a slowly exchanging hydron, participating in hydrogen bonding with two oxygens in ortho position on the gallate ring. The pKa of this proton has been determined to be 10. Conclusions This simple and novel approach permitted the understanding of the prototropic equilibrium of the semiquinone radicals generated by gallic acid, a ubiquitous compound, allowing new insights into its oxidation and subsequent reactions. PMID:20687941

2010-01-01

107

Free radicals produced by the oxidation of gallic acid: An electron paramagnetic resonance study  

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Full Text Available Abstract Background Gallic acid (3,4,5-trihydroxybenzoic acid is found in a wide variety of plants; it is extensively used in tanning, ink dyes, as well as in the manufacturing of paper. The gallate moiety is a key component of many functional phytochemicals. In this work electron paramagnetic spectroscopy (EPR was used to detect the free radicals generated by the air-oxidation of gallic acid. Results We found that gallic acid produces two different radicals as a function of pH. In the pH range between 7-10, the spectrum of the gallate free radical is a doublet of triplets (aH = 1.00 G, aH = 0.23 G, aH = 0.28 G. This is consistent with three hydrogens providing hyperfine splitting. However, in a more alkaline environment, pH >10, the hyperfine splitting pattern transforms into a 1:2:1 pattern (aH (2 = 1.07 G. Using D2O as a solvent, we demonstrate that the third hydrogen (i.e. aH = 0.28 G at lower pH is a slowly exchanging hydron, participating in hydrogen bonding with two oxygens in ortho position on the gallate ring. The pKa of this proton has been determined to be 10. Conclusions This simple and novel approach permitted the understanding of the prototropic equilibrium of the semiquinone radicals generated by gallic acid, a ubiquitous compound, allowing new insights into its oxidation and subsequent reactions.

Wagner Brett A

2010-08-01

108

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

109

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.

110

Probucol scavenged 1,1-diphenyl-2-picrylhydrazyl radicals and inhibited formation of thiobarbituric acid reactive substances.  

Science.gov (United States)

Probucol is suggested to have antioxidant properties. The direct scavenging action of probucol on hydroxyl radicals, superoxide and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals were examined using electron spin resonance (ESR) spectrometry. Probucol scavenged DPPH radicals dose dependently but showed no effect on hydroxyl radicals and superoxide generated by Fenton reaction and by hypoxanthine-xanthine oxidase system, respectively. It inhibited the formation of thiobarbituric acid reactive substances (TBARS) in rat cortex homogenate induced by ascorbic acid and FeCl2 at low dose, but it increased TBARS formation at high doses. Probucol showed no effect on the carbon centered radicals. Iron injection into the rat cortex, which is an experimental model for traumatic epilepsy, increased TBARS level in the cortex, hippocampus, striatum and cerebellum, but pretreatment with probucol inhibited the increase in these brain parts except for the hippocampus. These results suggest that the antioxidant property of probucol is partly due to its free radical scavenging effect. PMID:8005515

Hiramatsu, M; Liu, J; Edamatsu, R; Ohba, S; Kadowaki, D; Mori, A

1994-02-01

111

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.

112

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

113

In vitro antioxidant and radical-scavenging capacities of Citrullus colocynthes (L) and Artemisia absinthium extracts using promethazine hydrochloride radical cation and contemporary assays.  

Science.gov (United States)

A new, quick and economical decolorization assay based upon the generation of a radical cation made from promethazine hydrochloride (PMZH) is described for screening of antioxidant activity of plants/herbal extracts. PMZH radical cations, produced through a reaction between PMZH and potassium persulfate (K(2)S(2)O(8)) in phosphoric acid medium, have maximum absorption at 515?nm in their first-order derivative spectrum. Theconcentrations of chromagen and K(2)S(2)O(8) were optimized (final concentration of PMZH and K?S?O? were 0.166?mM and 0.11?mM, respectively) for better stability and sensitivity of the radical cation produced. Agood linear correlation was found between the percentage inhibition and the increasing amounts of standard antioxidants, with correlation coefficients ranging from 0.989 to 0.999. The newly developed assay was employed to evaluate the antioxidant capacity of Citrullus colocynthes L. and Artemisia absinthium extracts. The proposed assay involved a more stable radical cation and required only 1 h for preparation of a working solution in comparison to the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation decolorizaion assay, which was reported to be less sensitive at low pH and almost 12-16 h were required for preparation of a working ABTS solution. Other assays employed to evaluate the antioxidant potential andradical-scavenging capacities of the extracts were the ferric-reducing antioxidant power, 2,2'-diphenyl-1-picrylhydrazyl radical scavenging, total phenolic contents assay, total flavonoid contents and metal-chelating activity assays, and the lipid peroxidation value in linoleic acid emulsion systems. The results indicate that boththe plants have potent free radical-scavenging activity and the ability to prevent lipid peroxidation and radical chain reactions. PMID:21954313

Asghar, M Nadeem; Khan, I Ullah; Bano, N

2011-10-01

114

Hydroxyl radical-induced reactions in polyadenylic acid as studied by pulse radiolysis. Pt.IV. Reactions of primary radicals with reductants  

International Nuclear Information System (INIS)

The absorption spectra of polyadenylic acid radicals in N2O saturated aqueous solutions in the absence of any scavengers and in a presence of cysteamine have been recorded after the completion of the following consecutive reactions: OH. addition, transformation of OH-adducts and intermolecular self repair between radical with open ring and amino radical being the products of later transformations. The scheme of competitive reactions with reductants (thiols) has been presented.The reactions of two OH-adducts with adenine (A) moiety of polyadenylic acid (poly A) at the positions C4 and C8 have not been observed within reductants concentrations up to 10 ?M cysteamine (CyA) and 80 ?M glutathione (GSH). From the competition studies with cationic thiols (cysteamine) as reductant and with selective scavenging of reducing radicals with oxygen two repair reactions have been observed; the first one (1.8· 108 M-1S-1) in miliseconds region of repair of the radical with open ring being the product of the transformation of A8OH adduct and the second one (4.2·106 M-1s-1) in seconds region for repair of the amino radical being the product of the transformation of A4OH adduct. However, with glutathione (anionic thiol) the protective effect was attributed only to OH. scavenging (author)

115

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

116

Radical scavenging ability of gallic acid toward OH and OOH radicals. Reaction mechanism and rate constants from the density functional theory.  

Science.gov (United States)

Gallic acid is a ubiquitous compound, widely distributed in the vegetal kingdom and frequently found in the human diet. In the present work, its primary antioxidant activity has been investigated using the density functional theory (DFT), and the quantum mechanics-based test for overall free radical scavenging activity (QM-ORSA) protocol. It was found that gallic acid is a better antioxidant than the reference compound, Trolox, regardless of the polarity of the environment. In addition, gallic acid is predicted to be among the best peroxyl radical scavengers identified so far in nonpolar (lipid) media. This compound is capable of scavenging hydroxyl radicals at diffusion-limited rates, and hydroperoxyl radicals with rate constants in the order of 10(5) M(-1) s(-1). The deprotonation of gallic acid, in aqueous solution, is predicted to increase the protective action of this compound against oxidative stress. Gallic acid was also identified as a versatile scavenger, capable of rapidly deactivating a wide variety of reactive oxygen species (ROS) and reactive nitrogen species (RNS) via electron transfer at physiological pH. PMID:25119432

Marino, Tiziana; Galano, Annia; Russo, Nino

2014-09-01

117

Polyphenolic acids from mint (the aerial of Mentha haplocalyx Briq.) with DPPH radical scavenging activity.  

Science.gov (United States)

Vegetables of mint (the aerial part of Mentha haplocalyx) contain a significant amount of polyphenols with many health benefits. The crude aqueous acetone extract exhibited high antioxidant activity (IC(50)= 45.67 mug/mL) in 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. The activity-guided separation of chlorophyll removal fraction on column chromatography afforded 8 polyphenolic acids, including a new compound, cis-salvianolic acid J (1), and 7 known compounds, salvianolic acid J (2), lithospermic acid (3), rosmarinic acid (4), lithospermic acid B (5), magnesium lithospermate B (6), sodium lithospermate B (7), and danshensu (8), respectively. Their structural elucidations of all the compounds were based on extensive spectroscopic methods, including HRESIMS and 2D NMR experiments (HSQC, HMBC, and ROESY) and by comparison with reference values. Compounds 2, 3, and 5 to 8 were isolated from Mentha genus for the 1st time. The DPPH radical scavenging activities of all the isolated compounds were evaluated. PMID:20546395

She, G-M; Xu, C; Liu, B; Shi, R-B

2010-05-01

118

Radiolytic study of the action of perhydroxyl radicals with ascorbic acid  

International Nuclear Information System (INIS)

This paper shows that the difficulties encountered up to now about the interpretation of the radiolysis of aerated ascorbic acid (AH2) solutions, were due to a low oxygen concentration. For oxygen-saturated solutions, the yield is about G(-AH2) = G/sub OH/ + G/sub H/ + G/sub eaq-/ according to the mechanism, and formic acid has no influence on it. For lower concentrations of oxygen, in the presence of air, the action of oxygen on AH radical being slow, the yield decreases because of competitive reactions. Formic acid accentuates the decrease. This hypothesis allows a quantitative interpretation of the experimental results which explains the influence of AH2 concentration (1) by the presence of an oxidation chain by O2, initiated by OH and HO2 radicals; this chain, however, is not important even at the highest concentrations, and (2) by a dilution effect allowing partial disproportionation of HO2 radicals; the kinetic calculation leads to the value of the rate constant of oxidation of AH2 by HO2: k8 = 3300 M-1 sec-1

119

Free radical mediated formation of 3-monochloropropanediol (3-MCPD) fatty acid diesters.  

Science.gov (United States)

The present study was conducted to test the hypothesis that a free radical was formed and mediated the formation of 3-monochloropropanediol (3-MCPD) fatty acid diesters, a group of food contaminants, from diacylglycerols at high temperature under a low-moisture condition for the first time. The presence of free radicals in a vegetable oil kept at 120 °C for 20 min was demonstrated using an electron spin resonance (ESR) spectroscopy examination with 5,5-dimethylpyrroline-N-oxide (DMPO) as the spin trap agent. ESR investigation also showed an association between thermal treatment degree and the concentration of free radicals. A Fourier transform infrared spectroscopy (FT-IR) analysis of sn-1,2-stearoylglycerol (DSG) at 25 and 120 °C suggested the possible involvement of an ester carbonyl group in forming 3-MCPD diesters. On the basis of these results, a novel free radical mediated chemical mechanism was proposed for 3-MCPD diester formation. Furthermore, a quadrupole-time of flight (Q-TOF) MS/MS investigation was performed and detected the DMPO adducts with the cyclic acyloxonium free radical (CAFR) and its product MS ions, proving the presence of CAFR. Furthermore, the free radical mechanism was validated by the formation of 3-MCPD diesters through reacting DSG with a number of organic and inorganic chlorine sources including chlorine gas at 120 and 240 °C. The findings of this study might lead to the improvement of oil and food processing conditions to reduce the level of 3-MCPD diesters in foods and enhance food safety. PMID:23425600

Zhang, Xiaowei; Gao, Boyan; Qin, Fang; Shi, Haiming; Jiang, Yuangrong; Xu, Xuebing; Yu, Liangli Lucy

2013-03-13

120

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)

121

Bim Upregulation by Histone Deacetylase Inhibitors Mediates Interactions with the Bcl-2 Antagonist ABT-737: Evidence for Distinct Roles for Bcl-2, Bcl-xL, and Mcl-1?  

OpenAIRE

The Bcl-2 antagonist ABT-737 kills transformed cells in association with displacement of Bim from Bcl-2. The histone deactetylase (HDAC) inhibitor suberoyl bis-hydroxamic acid (SBHA) was employed to determine whether and by what mechanism ABT-737 might interact with agents that upregulate Bim. Expression profiling of BH3-only proteins indicated that SBHA increased Bim, Puma, and Noxa expression, while SBHA concentrations that upregulated Bim significantly potentiated ABT-737 lethality. Concor...

Chen, Shuang; Dai, Yun; Pei, Xin-yan; Grant, Steven

2009-01-01

122

Stereocontrolled syntheses of kainoid amino acids from 7-azabicyclo[2.2.1]heptadienes using tandem radical addition-homoallylic radical rearrangement.  

OpenAIRE

[reaction; see text] N-Boc syn-7-(2-hydroxyethyl)-4-(alkyl or aryl)sulfonyl-2-azabicyclo[2.2.1]hept-5-enes serve as precursors in syntheses of the neuroexcitants 3-(carboxymethyl)pyrrolidine-2,4-dicarboxylic acid 43, alpha-kainic acid 12, alpha-isokainic acid 14, and alpha-dihydroallokainic acid 77. The key step in these syntheses is the intermolecular radical addition of 2-iodoethanol to a N-Boc 2-(alkyl or aryl)sulfonyl-7-azabicyclo[2.2.1]heptadiene 7 to induce nitrogen-directed homoallylic...

Hodgson, Dm; Hachisu, S.; Andrews, Md

2005-01-01

123

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

124

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...

125

Effect of hydrogen bonding in benzoic acid on free radical reactions in FBX system over prolonged periods  

International Nuclear Information System (INIS)

Benzoic acid increases the radiolytic oxidation of ferrous ions through a chain reaction. Benzoic acid increases the rate of thermal oxidation of ferrous ions by xylenol orange also. Benzoic acid itself without xylenol orange produces thermal oxidation of ferrous ions through a chain reaction. The thermally excited benzoic acid molecules form free radicals which initiate the chain which is later propagated by the chemically excited benzoic acid molecules. (author) 9 refs.; 1 fig

126

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, ABTS+ 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. PMID:24813273

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

2014-09-15

127

Oxidation of (carboxyalkyl)thiopropionic acid derivatives by hydroxyl radicals. Mechanisms and kinetics of competitive inter- and intramolecular formation of {sigma}- and {sigma}{sup *}-type sulfuranyl radicals  

Energy Technology Data Exchange (ETDEWEB)

The substituent effects on kinetics and yields of specific intermediates and products for the one-electron oxidation by hydroxyl radicals of various (carboxyalkyl)thiopropionic acid derivatives, 3-(methylthio)propionic acid (3-MTPA), 3,3{prime}-thiodipropionic acid (3,3{prime}-TDPA), 3-(carboxymethylthio)propionic acid (3-CMTPA), and 2-(carboxymethylthio)succinic acid (2-CMTPA) have been investigated employing pulse radiolysis on the nanosecond to microsecond time scale, and {gamma}-radiolysis. For each derivative, the initial step was a formation of a hydroxysulfuranyl radical proceeding with absolute rate constants of k{sub OH+3-MTPA} = 9.1 {times} 10{sup 9} M{sup {minus}1}s {sup {minus}1} and k{sub OH+3,3{prime}-TDPA} = 5.8 {times} 10{sup 9} M{sup {minus}1} s{sup {minus}1}. The subsequent formation of one-electron-oxidized intermediates such as dimeric sulfur-sulfur (S{hor_ellipsis}S)-three-electron-bonded and monomeric sulfur-carboxylate oxygen (S-O)-bonded sulfide radical cations strongly depended on pH, thioether concentration, and the availability of {alpha} or {beta}-positioned carboxylate functions. A spectral resolution procedure permitted the quantification of all transients present in solution at any time after the pulse.

Bobrowski, K. [Inst. of Nuclear Chemistry and Technology, Warsaw (Poland)]|[Univ. of Notre Dame, IN (United States). Radiation Lab.; Pogocki, D. [Inst. of Nuclear Chemistry and Technology, Warsaw (Poland); Schoeneich, C. [Univ. of Kansas, Lawrence, KS (United States). Dept. of Pharmaceutical Chemistry

1998-12-17

128

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

129

Reactions of thiyl radicals with phenothiazines and other antioxidants in aqueous solutions  

International Nuclear Information System (INIS)

Reaction rate constants of thiyl radicals with phenothiazines, promethazine (PMZ), chlorpromazine (CPZ), prochlorperazine (PPZ), trimeperazine tarterate (TPZ), and other antioxidants, e.g., ascorbic acid and 2.2-azinobis(3-ethyl benzthiazoline-6 sulphonate) (ABTS) have been estimated using pulse radiolysis technique. In general they are quite high (108-109 M-1 s-1). The k values for cysteine, cysteamine, mercaptoethanol, and mercaptopropionic acid with similar structures and molecular weights are more or less similar for PMZ, CPZ, and PPZ. Rate constants are lower in value for PenS, DTT, DTE and GuS radicals of phenothiazines showing that they are dependent upon the structure and the molecular weight of the compound. Rate constants are the same whether the thiyl radicals are generated from thiols or their corresponding disulphides. The k values for chlorine-containing phenothiazines, chlorpromazine, and prochlorperazine are higher than those of promothazine

130

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

Scientific Electronic Library Online (English)

Full Text Available 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

131

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

132

CHARACTERIZATION OF FATTY ACID PROFILE, POLYPHENOLIC CONTENT AND ANTIOXIDANT ACTIVITY OF COLD PRESSED AND REFINED EDIBLE OILS FROM MACEDONIA  

OpenAIRE

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 o...

Saša Mitrev; Sanja Kostadinovic-Velickovska

2013-01-01

133

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

134

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

135

The kinetics of the acid-base equilibrium of 4-carboxybenzophenone ketyl radical. A pulse radiolysis study  

Energy Technology Data Exchange (ETDEWEB)

Pulse radiolysis of nitrogen saturated aqueous solutions of 4-carboxybenzophenone below pH 8 has been used to generate the 4-carboxybenzophenone ketyl radical anion to allow the direct observation of the protonation of this radical in neutral and moderately acidic solutions. A transient absorption band with [lambda][sub max] 650 nm (assigned to the ketyl radical anion) was observed immediately after the pulse which was subsequently converted to an absorption band with [lambda][sub max] = 570 nm (assigned to the ketyl radical). The kinetics of this conversion was of pseudo-first-order with a rate constant linearly dependent on the H[sup +] concentration. These findings are interpreted in terms of a protonation of the ketyl radical anion by water and by protons. (author).

Bobrowski, Krzysztof; Marciniak, Bronislaw (Notre Dame Univ., IN (United States). Radiation Lab.)

1994-04-01

136

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

International Nuclear Information System (INIS)

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 ? rays from 60Co, 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 CH3CHOH and CH3CH(OH)CH3 to benzophenone; the temperature dependence of the transfer rate constant was studied

137

[Effects of ascorbic acid on the metabolic fate and the free radical formation of iproniazid].  

Science.gov (United States)

The effects of ascorbic acid (AA) on the metabolic fate of iproniazid (IPN) and on the free radical intermediates derived from IPN were investigated in rats. After oral administration of IPN with or without AA, the plasma concentration and the urinary excretion of IPN and its metabolites were determined by gas chromatography-mass spectrometry using stable isotope labeled compounds as internal standards. In the excretion of IPN and its metabolites except hydrazine (Hy), the differences between co-administration and single administration were not observed. The excretion of Hy, which is a known hepatotoxic metabolite, decreased clearly in the co-administration of IPN and AA. When IPN and AA were co-administered orally, the profiles of plasma levels of IPN and its metabolites were almost similar after the administration of IPN alone. Furthermore, no differences between i.v. co-administration and i.v. administration alone were observed. These results indicated that AA did not affect both absorption and metabolism of IPN. By the electron spin resonance (ESR) spectroscopy and spin-trapping technique, the ESR signals due to the alpha-(4-pyridyl 1-oxide)-N-tert-butylnitrone (4-POBN) adducts induced by isopropylhydrazine (IP-Hy) were two-fold higher than those by IPN in microsomal systems. The free radical formations of IPN and IP-Hy were significantly inhibited by AA in a dose dependent manner. The 4-POBN-trapped radical species generated from IPN and IP-Hy were presumed to be an isopropyl radical by the results of mass spectrometry.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1294718

Matsuki, Y; Hongu, Y; Noda, Y; Kiwada, H; Sakurai, H; Goromaru, T

1992-12-01

138

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

139

Detection of OH Radical in the Photodissociation of p-Aminobenzoic Acid at 266 nm  

Science.gov (United States)

Photodissociation of p-aminobenzoic acid at 266 nm was investigated by probing the nascent OH photoproduct employing the laser-induced fluorescence technique. It was found that the nascent OH radical was vibrationally cold and its rotational state distribution conformed to be a Boltzmann behavior, characterized by a rotational temperature of 1040 ± 110 K. The rotational energy of OH was determined to be 8.78 ± 0.84 kJ/mol. Between the two spin-orbit states of OH, 2?3/2 and 2?1/2, the former was found to be preferentially populated. The distribution of the ?(A?) state for the ?-doublet was dominant. Finally, a probable mechanism for the formation of OH produced from the photodissociation of p-aminobenzoic acid is discussed.

Zhou, Can-hua; Cheng, Shi-bo; Yin, Hong-ming; He, Guo-zhong

2009-12-01

140

ABT-089, but not ABT-107, ameliorates nicotine withdrawal-induced cognitive deficits in C57BL6/J mice.  

Science.gov (United States)

Nicotine withdrawal produces cognitive deficits that can predict relapse. Amelioration of these cognitive deficits emerges as a target in current smoking cessation therapies. In rodents, withdrawal from chronic nicotine disrupts contextual fear conditioning (CFC), whereas acute nicotine enhances this hippocampus-specific learning and memory. These modifications are mediated by ?2-subunit-containing (?2*) nicotinic acetylcholine receptors in the hippocampus. We aimed to test ABT-089, a partial agonist of ?4?2*, and ABT-107, an ?7 nicotinic acetylcholine receptor agonist, for amelioration of cognitive deficits induced by withdrawal from chronic nicotine in mice. Mice underwent chronic nicotine administration (12.6?mg/kg/day or saline for 12 days), followed by 24?h of withdrawal. At the end of withdrawal, mice received 0.3 or 0.6?mg/kg ABT-089 or 0.3?mg/kg ABT-107 (doses were determined through initial dose-response experiments and prior studies) and were trained and tested for CFC. Nicotine withdrawal produced deficits in CFC that were reversed by acute ABT-089, but not ABT-107. Cued conditioning was not affected. Taken together, our results suggest that modulation of hippocampal learning and memory using ABT-089 may be an effective component of novel therapeutic strategies for nicotine addiction. PMID:25426579

Yildirim, Emre; Connor, David A; Gould, Thomas J

2015-04-01

141

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

142

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

143

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.

144

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

145

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

Directory of Open Access Journals (Sweden)

Full Text Available 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.

Y. Tan

2011-06-01

146

Antioxidant activity and free radical scavenging reactions of gentisic acid: in-vitro and pulse radiolysis studies.  

Science.gov (United States)

Abstract Antioxidant activity of gentisic acid has been studied using fast chemical kinetics and two in vitro models, namely the isolated rat liver mitochondria (RLM) and the human erythrocytes. The presence of gentisic acid (GA) during irradiation significantly reduced the levels of gamma radiation induced damages to lipids and proteins in RLM. Further, GA imparted protection to the human erythrocytes against exposure to gamma radiation. Molecular mechanism of free radical scavenging reactions has been evaluated with the help of rate constants and transients obtained from gentisic acid using pulse radiolysis technique. GA efficiently scavenged hydroxyl radical (k = 1.1 × 10(10) dm(3)mol(-1)s(-1)) to produce reducing adduct radical (~76%) and oxidizing phenoxyl radical (~24%). GA has also scavenged organohaloperoxyl radical (k = 9.3 × 10(7) dm(3) mol(-1)s(-1)). Ascorbate has been found to repair phenoxyl radical of GA (k = 1.0 × 10(7) dm(3)mol(-1)s(-1)). Redox potential value of GA(•)/GA couple (0.774 V vs NHE) obtained by cyclic voltammetry is less than those of physiologically important oxidants, which supports the observed antioxidant capacity of GA. We, therefore, propose that the antioxidant and radioprotective properties of GA are exerted by its phenoxyl group. PMID:22023109

Joshi, Ravi; Gangabhagirathi, R; Venu, S; Adhikari, S; Mukherjee, T

2012-01-01

147

Studies on reactions of ?-hydroxyalkyl radicals derived from n-propanol and n-butanol with nicotinic acid: estimation of their reduction potential  

International Nuclear Information System (INIS)

Reactions of ?-hydroxyalkyl radicals derived from n-propanol and n-butanol with nicotinic acid were studied by pulse radiolysis techniques. In these reactions adducts of ?-hydroxyalkyl radicals and nicotinic acid are formed. Rate constant for these reactions were determined. These adducts were found to decay by uni-molecular pathway giving the pyridinyl radicals. From the earlier obtained linear plot of rate constants for adduct formation versus the reduction potentials of ?-hydroxyalkyl radicals of 2-propanol, ethanol and methanol, reduction potentials of ?-hydroxyalkyl radicals of n-propanol and n-butanol were estimated. (author)

148

Concerted effects in the reaction of {sup {center_dot}}OH radicals with aromatics: radiolytic oxidation of salicylic acid  

Energy Technology Data Exchange (ETDEWEB)

Liquid chromatographic and capillary electrophoretic studies have been used to resolve the products produced in the radiolytic oxidation of salicylic acid in aqueous solution. These studies have shown that, as in the case of phenol, {sup {center_dot}}OH radicals preferentially add to the positions ortho and para to the OH substituent. However, in contrast to its reaction with phenol, addition at the ortho position is favored over addition at the para position. Because {sup {center_dot}}OH radical is a strong electrophile this difference suggests that the electron population at the ortho position in the salicylate anion is enhanced as a result of the hydrogen bonding in salicylic acid.

Albarran, G. E-mail: albarran@nuclecu.unam.mx; Schuler, R.H

2003-06-01

149

Radical polymerization of N-vinylpyrrolidone in the presence of syndiotactic poly(methacrylic acid) templates  

International Nuclear Information System (INIS)

Radical polymerization of N-vinylpyrrolidone along poly(methacrylic acid) templates of high syndiotactic content was followed dilatometrically in dimethylformamide, which was used as solvent. The effects of template concentration, template molar mass, and temperature on polymerization rate and average molar mass of the formed polyvinylpyrrolidone (PVP) were examined. Template concentrations were varied around the critical concentration for homogeneous segmental distribution, C. Below this concentration, template coils can act as separate microreactors wherein growing PVP radicals exhibit maximum rate enhancement, i.e., relative rate upsilon/sub R/ = upsilon/sub R max/. In the free solution, blank polymerization occurs, i.e., upsilon/sub R/ = 1. Consequently, upsilon/sub R/ can be approximated by the equation ?/sub R/ = phi?/sub R/max/ + (1 - phi), where phi represents the volume fraction occupied by template coils. The slight increase in ?/sub R/ and PVP molar mass with the template chain length is supposed to be caused by the influence of translational diffusion on the termination step. Over the investigated temperature range of 50 to 700C, the activation energy and entropy were almost identical for blank and template polymerization. An expected decrease of ?E not equal to and ?S not equal to in template systems is supposed to be compensated by the effects of desolvation of the template macromolecules during the propagation stepopagation step

150

Polyphenolic Contents and Free Radical Scavenging Potential of Extracts from Leaves of Ocimum americanum L.  

Directory of Open Access Journals (Sweden)

Full Text Available This study assessed the polyphenolic contents and antioxidant activity of ethanol, butanol and ethyl acetate extracts of Ocimum americanum leaves using in vitro models. The ability of the extracts to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH?, 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid (ABTS?+, hydrogen peroxide (H2O2, Nitric Oxide (NO and hydroxyl radical (OH? was investigated. The inhibition of lipid oxidation, reducing power, total flavonoids, phenols and flavonols contents of the extracts were also determined using spectrophotometric methods. The result revealed highest concentration of polyphenolic compounds in the ethanol extract followed by n-butanol while ethyl acetate extract contained the least concentration. Free radical scavenging potentials of the extracts were found to be proportional to their respective polyphenolic contents. This study provides evidence that O. americanum leaves contain biologically active components with effective antioxidant activity and thus could be used for the management of radical related diseases.

A.J. Afolayan

2013-01-01

151

New easy method for obtaining approximate redox potentials of radicals, produced by 60Co-?-radiolysis, using heteropoly electrolytes of molybdenum and tungsten as electron acceptors. The redox potential of some alcohol and organic acid radicals  

International Nuclear Information System (INIS)

The reducing ability of short lived radicals can be studied by reacting them with electron acceptors whose redox potential is known. Heteropoly electrolytes of molybdenum and tungsten are used for this purpose. The reduction of these species proceeds in distinct reduction steps producing the corresponding heteropoly blues until the potential of the next reduction step is more negative than the potential of the radical. The apparent redox potentials of some alcohols and formic acid radicals have been determined. (U.S.)

152

Free radicals produced by ?irradiation of nitroalkanes in frozen glassy acidic solutions  

International Nuclear Information System (INIS)

The scavenging of paramagnetic species by nitroalkanes formed during the ? irradiation of aqueous 6.4 molar sulfuric acid glasses has been studied by using ESR. Nitroalkanes give rise to RNO2H radicals, the nitrogen hyperfine coupling of which has the values A sub(parallel)sup(N)=48 G and A sub(perpendicular)sup(N)=18 G with g sub(parallel)=2.0035 and g sub(perpendicular)=2.0075. The RNO2H yields for 0.5 molar solutions of nitromethane and 2-nitro-2-methyl-propanol are G asymptotically equals 4 and G asymptotically equals 3, respectively. G(SO4-+OHsup(.)) is roughly independent of the nitroalkane concentration. These results are interpreted as the scavenging of hydrogen atoms due to the energetic recombination of non-hydrated primary species (H2O+, OHsup(.), e-) according to an assumption of Hamill. (auth.)

153

One-component thioxanthone acetic acid derivative photoinitiator for free radical polymerization.  

Science.gov (United States)

Acetic acid-based thioxanthone (TXCH2 COOH) was synthesized and characterized and used as a photoinitiator for free radical photopolymerization of methyl methacrylate (MMA) in the absence and presence of a tertiary amine (MDEA) in different solvents. Different absorption properties were observed depending on the solvent. Fluorescence and phosphorescence experiments were also carried out successfully. The fluorescence quantum yield was found to be 0.09 and the phosphorescence lifetime was calculated as 138 ms at 77 K. The photoinitiator undergoes efficient intersystem crossing into the triplet state and the lowest triplet state possesses ?-?* configuration. Laser flash photolysis experiments show that transient absorption of TXCH2 COOH is similar to the parent thioxanthone and the triplet lifetime was calculated as 2.3 ?s at 630 nm. PMID:24372104

Esen, Duygu S; Temel, Gokhan; Balta, Demet K; Allonas, Xavier; Arsu, Nergis

2014-01-01

154

Lewis acid-water/alcohol complexes as hydrogen atom donors in radical reactions.  

Science.gov (United States)

Water or low molecular weight alcohols are, due to their availability, low price and low toxicity ideal reagents for organic synthesis. Recently, it was reported that, despite the very strong BDE of the O-H bond, they can be used as hydrogen atom donors in place of expensive and/or toxic group 14 metal hydrides when boron and titanium(III) Lewis acids are present. This finding represents a considerable innovation and uncovers a new perspective on the paradigm of hydrogen atom transfers to radicals. We discuss here the influence of complex formation and other association processes on the efficacy of the hydrogen transfer step. A delicate balance between activation by complex formation and deactivation by further hydrogen bonding is operative. PMID:23967699

Povie, Guillaume; Renaud, Philippe

2013-01-01

155

Hydrogen-atom abstraction from a model amino acid: dependence on the attacking radical.  

Science.gov (United States)

We have used computational chemistry to examine the reactivity of a model amino acid toward hydrogen abstraction by HO•, HOO•, and Br•. The trends in the calculated condensed-phase (acetic acid) free energy barriers are in accord with experimental relative reactivities. Our calculations suggest that HO• is likely to be the abstracting species for reactions with hydrogen peroxide. For HO• abstractions, the barriers decrease as the site of reaction becomes more remote from the electron-withdrawing ?-substituents, in accord with a diminishing polar deactivating effect. We find that the transition structures for ?- and ?-abstractions have additional hydrogen-bonding interactions, which lead to lower gas-phase vibrationless electronic barriers at these positions. Such favorable interactions become less important in a polar solvent such as acetic acid, and this leads to larger calculated barriers when the effect of solvation is taken into account. For Br• abstractions, the ?-barrier is the smallest while the ?-barrier is the largest, with the barrier gradually becoming smaller further along the side chain. We attribute the low barrier for the ?-abstraction in this case to the partial reflection of the thermodynamic effect of the captodatively stabilized ?-radical product in the more product-like transition structure, while the trend of decreasing barriers in the order ? > ? > ? ? ? is explained by the diminishing polar deactivating effect. More generally, the favorable influence of thermodynamic effects on the ?-abstraction barrier is found to be smaller when the transition structure for hydrogen abstraction is earlier. PMID:25072602

Amos, Ruth I J; Chan, Bun; Easton, Christopher J; Radom, Leo

2015-01-22

156

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

Directory of Open Access Journals (Sweden)

Full Text Available The radical-scavenging activities of two thiols, eight (thiobarbituric 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 phenolic antioxidants. Except for the potent inhibitor 5,5-dimethyl-2-thiobarbituric acid (3, the IP for thiobarbituric acid derivatives was about one tenth of that for phenolic antioxidants. The IP for 1,3,5-trimethyl-2-thiobarbituric acid (1 and 5-allyl-1, 3-dimethyl-2-thiobarbituric acid (7 was less than that of the control, possibly due to inhibition by a small amount of atmospheric oxygen in the DSC container. The ratio of the chain inhibition to that of chain propagation (CI/CP for the thiols and thiobarbituric acid compounds except for 1, 3 and 7 was about 10 times greater or greater than that for phenolic compounds. A kinetic chain length (KCL about 10% greater than that of the control was observed for 1, suggesting that 1 had chain transfer reactivity in the polymerization of MMA. The average molecular weight of polymers formed from thiobarbituric acid derivatives is discussed.

Seiichiro Fujisawa

2012-04-01

157

Reduced selective constraint in endosymbionts: elevation in radical amino acid replacements occurs genome-wide.  

Science.gov (United States)

As predicted by the nearly neutral model of evolution, numerous studies have shown that reduced N(e) accelerates the accumulation of slightly deleterious changes under genetic drift. While such studies have mostly focused on eukaryotes, bacteria also offer excellent models to explore the effects of N(e). Most notably, the genomes of host-dependent bacteria with small N(e) show signatures of genetic drift, including elevated K(a)/K(s). Here, I explore the utility of an alternative measure of selective constraint: the per-site rate of radical and conservative amino acid substitutions (D(r)/D(c)). I test the hypothesis that purifying selection against radical amino acid changes is less effective in two insect endosymbiont groups (Blochmannia of ants and Buchnera of aphids), compared to related gamma-Proteobacteria. Genome comparisons demonstrate a significant elevation in D(r)/D(c) in endosymbionts that affects the majority (66-79%) of shared orthologs examined. The elevation of D(r)/D(c) in endosymbionts affects all functional categories examined. Simulations indicate that D(r)/D(c) estimates are sensitive to codon frequencies and mutational parameters; however, estimation biases occur in the opposite direction as the patterns observed in genome comparisons, thereby making the inference of elevated D(r)/D(c) more conservative. Increased D(r)/D(c) and other signatures of genome degradation in endosymbionts are consistent with strong effects of genetic drift in their small populations, as well as linkage to selected sites in these asexual bacteria. While relaxed selection against radical substitutions may contribute, genome-wide processes such as genetic drift and linkage best explain the pervasive elevation in D(r)/D(c) across diverse functional categories that include basic cellular processes. Although the current study focuses on a few bacterial lineages, it suggests D(r)/D(c) is a useful gauge of selective constraint and may provide a valuable alternative to K(a)/K(s) when high sequence divergences preclude estimates of K(s). Broader application of D(r)/D(c) will benefit from approaches less prone to estimation biases. PMID:22194947

Wernegreen, Jennifer J

2011-01-01

158

Experimental and computational investigations of oxygen reactivity in a heme and tyrosyl radical-containing fatty acid ?-(di)oxygenase.  

Science.gov (United States)

Rice ?-(di)oxygenase mediates the regio- and stereospecific oxidation of fatty acids using a persistent catalytic tyrosyl radical. Experiments conducted in the physiological O(2) concentration range, where initial hydrogen atom abstraction from the fatty acid occurs in a kinetically reversible manner, are described. Our findings indicate that O(2)-trapping of an ?-carbon radical is likely to reversibly precede reduction of a 2-(R)-peroxyl radical intermediate in the first irreversible step. A mechanism of concerted proton-coupled electron transfer is proposed on the basis of natural abundance oxygen-18 kinetic isotope effects, deuterium kinetic isotope effects, and calculations at the density functional level of theory, which predict a polarized transition state in which electron transfer is advanced to a greater extent than proton transfer. The approach outlined should be useful for identifying mechanisms of concerted proton-coupled electron transfer in a variety of oxygen-utilizing enzymes. PMID:21790181

Huff, Gregory S; Doncheva, Irina S; Brinkley, David W; Angeles-Boza, Alfredo M; Mukherjee, Arnab; Cramer, Christopher J; Roth, Justine P

2011-08-30

159

Phytochemical Analysis and Free Radical Scavenging Activity of Medicinal Plants Gnidia glauca and Dioscorea bulbifera  

Science.gov (United States)

Gnidia glauca and Dioscorea bulbifera are traditional medicinal plants that can be considered as sources of natural antioxidants. Herein we report the phytochemical analysis and free radical scavenging activity of their sequential extracts. Phenolic and flavonoid content were determined. Scavenging activity was checked against pulse radiolysis generated ABTS•+ and OH radical, in addition to DPPH, superoxide and hydroxyl radicals by biochemical methods followed by principal component analysis. G. glauca leaf extracts were rich in phenolic and flavonoid content. Ethyl acetate extract of D. bulbifera bulbs and methanol extract of G. glauca stem exhibited excellent scavenging of pulse radiolysis generated ABTS•+ radical with a second order rate constant of 2.33×106 and 1.72×106, respectively. Similarly, methanol extract of G. glauca flower and ethyl acetate extract of D. bulbifera bulb with second order rate constants of 4.48×106 and 4.46×106 were found to be potent scavengers of pulse radiolysis generated OH radical. G. glauca leaf and stem showed excellent reducing activity and free radical scavenging activity. HPTLC fingerprinting, carried out in mobile phase, chloroform: toluene: ethanol (4: 4: 1, v/v) showed presence of florescent compound at 366 nm as well as UV active compound at 254 nm. GC-TOF-MS analysis revealed the predominance of diphenyl sulfone as major compound in G. glauca. Significant levels of n-hexadecanoic acid and octadecanoic acid were also present. Diosgenin (C27H42O3) and diosgenin (3á,25R) acetate were present as major phytoconstituents in the extracts of D. bulbifera. G. glauca and D. bulbifera contain significant amounts of phytochemicals with antioxidative properties that can be exploited as a potential source for herbal remedy for oxidative stress induced diseases. These results rationalize further investigation in the potential discovery of new natural bioactive principles from these two important medicinal plants. PMID:24367520

Ghosh, Sougata; Derle, Abhishek; Ahire, Mehul; More, Piyush; Jagtap, Soham; Phadatare, Suvarna D.; Patil, Ajay B.; Jabgunde, Amit M.; Sharma, Geeta K.; Shinde, Vaishali S.; Pardesi, Karishma; Dhavale, Dilip D.; Chopade, Balu A.

2013-01-01

160

Phytochemical analysis and free radical scavenging activity of medicinal plants Gnidia glauca and Dioscorea bulbifera.  

Science.gov (United States)

Gnidia glauca and Dioscorea bulbifera are traditional medicinal plants that can be considered as sources of natural antioxidants. Herein we report the phytochemical analysis and free radical scavenging activity of their sequential extracts. Phenolic and flavonoid content were determined. Scavenging activity was checked against pulse radiolysis generated ABTS(•+) and OH radical, in addition to DPPH, superoxide and hydroxyl radicals by biochemical methods followed by principal component analysis. G. glauca leaf extracts were rich in phenolic and flavonoid content. Ethyl acetate extract of D. bulbifera bulbs and methanol extract of G. glauca stem exhibited excellent scavenging of pulse radiolysis generated ABTS(•+) radical with a second order rate constant of 2.33 × 10(6) and 1.72 × 10(6), respectively. Similarly, methanol extract of G. glauca flower and ethyl acetate extract of D. bulbifera bulb with second order rate constants of 4.48 × 10(6) and 4.46 × 10(6) were found to be potent scavengers of pulse radiolysis generated OH radical. G. glauca leaf and stem showed excellent reducing activity and free radical scavenging activity. HPTLC fingerprinting, carried out in mobile phase, chloroform: toluene: ethanol (4: 4: 1, v/v) showed presence of florescent compound at 366 nm as well as UV active compound at 254 nm. GC-TOF-MS analysis revealed the predominance of diphenyl sulfone as major compound in G. glauca. Significant levels of n-hexadecanoic acid and octadecanoic acid were also present. Diosgenin (C??H??O?) and diosgenin (3á,25R) acetate were present as major phytoconstituents in the extracts of D. bulbifera. G. glauca and D. bulbifera contain significant amounts of phytochemicals with antioxidative properties that can be exploited as a potential source for herbal remedy for oxidative stress induced diseases. These results rationalize further investigation in the potential discovery of new natural bioactive principles from these two important medicinal plants. PMID:24367520

Ghosh, Sougata; Derle, Abhishek; Ahire, Mehul; More, Piyush; Jagtap, Soham; Phadatare, Suvarna D; Patil, Ajay B; Jabgunde, Amit M; Sharma, Geeta K; Shinde, Vaishali S; Pardesi, Karishma; Dhavale, Dilip D; Chopade, Balu A

2013-01-01

161

Hydroxyl radical-induced reactions in polyadenylic acid as studied by pulse radiolysis. Pt. 2. Reactions of primary radicals with oxidants  

International Nuclear Information System (INIS)

The rate constants for oxidation (oxygen, hydrogen peroxide) of two hydroxyl adducts with adenine moiety of polyadenylic acid (poly A) at the positions C4 and C8 have been measured and compared with those in some 9-substituted adenine derivatives. They are by one order of magnitude (with O2) or even two orders of magnitude (with H2O2) higher for an adduct formed at C8 in respect to that at C4. The strongly reducing hydroxyl adduct formed at C8 and the radical with open imidazole ring formed as the result of the unimolecular transformation of this adduct (part 1) can be selectively scavenged with oxygen. Thus the spectrum of deprotonated amino radical A(-H) formed as the result of the unimolecular transformation of C4 adduct could be obtained. This spectrum coincides quite well with the spectrum obtained in a similar way with H2O2 and with spectrum of deprotonated A(-H) radical obtained in the reaction with SO4-. (author). 21 refs, 3 figs, 1 tab

162

Dual role of the p38 MAPK/cPLA2 pathway in the regulation of platelet apoptosis induced by ABT-737 and strong platelet agonists  

Science.gov (United States)

p38 Mitogen-activated protein (MAP) kinase is involved in the apoptosis of nucleated cells. Although platelets are anucleated cells, apoptotic proteins have been shown to regulate platelet lifespan. However, the involvement of p38 MAP kinase in platelet apoptosis is not yet clearly defined. Therefore, we investigated the role of p38 MAP kinase in apoptosis induced by a mimetic of BH3-only proteins, ABT-737, and in apoptosis-like events induced by such strong platelet agonists as thrombin in combination with convulxin (Thr/Cvx), both of which result in p38 MAP kinase phosphorylation and activation. A p38 inhibitor (SB202190) inhibited the apoptotic events induced by ABT-737 but did not influence those induced by Thr/Cvx. The inhibitor also reduced the phosphorylation of cytosolic phospholipase A2 (cPLA2), an established p38 substrate, induced by ABT-737 or Thr/Cvx. ABT-737, but not Thr/Cvx, induced the caspase 3-dependent cleavage and inactivation of cPLA2. Thus, p38 MAPK promotes ABT-737-induced apoptosis by inhibiting the cPLA2/arachidonate pathway. We also show that arachidonic acid (AA) itself and in combination with Thr/Cvx or ABT-737 at low concentrations prevented apoptotic events, whereas at high concentrations it enhanced such events. Our data support the hypothesis that the p38 MAPK-triggered arachidonate pathway serves as a defense mechanism against apoptosis under physiological conditions. PMID:24263105

Rukoyatkina, N; Mindukshev, I; Walter, U; Gambaryan, S

2013-01-01

163

On the Origin of the Methyl Radical Loss from Deprotonated Ferulic and Isoferulic Acids: Electronic Excitation of a Transient Structure  

Science.gov (United States)

Formation of radical fragments from even-electron ions is an exception to the "even-electron rule". In this work, ferulic acid (FA) and isoferulic acid (IFA) were used as the model compounds to probe the fragmentation mechanisms and the isomeric effects on homolytic cleavage. Elimination of methyl radical and CO2 are the two competing reactions observed in the CID-MS of [FA - H]- and [IFA - H]-, of which losing methyl radical violates the "even-electron rule". The relative intensity of their product ions is significantly different, and thereby the two isomeric compounds can be differentiated by tandem MS. Theoretical calculations indicate that both the singlet-triplet gap and the excitation energy decrease in the transient structures, as the breaking C-O bond is lengthened. The methyl radical elimination has been rationalized as the intramolecular electronic excitation of a transient structure with an elongating C-O bond. The potential energy diagrams, completed by the addition of the energy barrier of the radical elimination, have provided a reasonable explanation of the different CID-MS behaviors of [FA - H]- and [IFA - H]-.

Zhang, Xiaoping; Li, Fei; Lv, Huiqing; Wu, Yanqing; Bian, Gaofeng; Jiang, Kezhi

2013-06-01

164

Feasibility investigation on deep ocean compact autonomous Raman spectrometer developed for in-situ detection of acid radical ions  

Science.gov (United States)

A newly developed Deep Ocean Compact Autonomous Raman Spectrometer (DOCARS) system is introduced and used for in-situ detection of acid radical ions in this paper. To evaluate the feasibility and capability of DOCARS for quantitative analysis of the acid radical ions in the deep ocean, extensive investigations have been carried out both in laboratory and sea trials during the development phase. In the laboratory investigations, Raman spectra of the prepared samples (acid radical ions solutions) were obtained, and analyzed using the method of internal standard normalization in data processing. The Raman signal of acid radical ions was normalized by that of water molecules. The calibration curve showed that the normalized Raman signal intensity of SO{4/2-}, NO{3/-}, and HCO{2/-} increases linearly as the concentration rises with correlation coefficient R 2 of 0.99, 0.99, and 0.98 respectively. The linear function obtained from the calibration curve was then used for the analysis of the spectra data acquired in the sea trial under a simulating chemical field in the deep-sea environment. It was found that the detected concentration of NO{3/-} according to the linear function can reflect the concentration changes of NO{3/-} after the sample was released, and the detection accuracy of the DOCARS system for SO{4/2-} is 8%. All the results showed that the DOCARS system has great potential in quantitative detection of acid radical ions under the deep-sea environment, while the sensitivity of the DOCARS system is expected to be improved.

Du, Zengfeng; Li, Ying; Chen, Jing; Guo, Jinjia; Zheng, Rong'er

2015-03-01

165

Continuous measurement of oxygen consumption by linoleic acid membranes exposed to free radicals generated by ?-radiation  

International Nuclear Information System (INIS)

Vesicles enclosed by membranes prepared from linoleic acid were exposed in the chamber of an oxygen electrode to free radicals generated by 60Co ?-rays. Oxidation was observed by oxygen consumption, conjugated diene formation, and tri-iodide assay for hydroperoxides. There was a dose-dependent lag period before onset of rapid peroxidation. Radiation chemical yields (G-values) ranged from 4.45 to 19.37 ?-mol J-1 for maximum rates of oxygen consumption and from 2.18 to 16.37 ?mol J-1 for maximum rates of hydroperoxide production when the radiation dose-rate was varied between 5.39 and 0.14 Gy min-1. The magnitude of these G-values and the linear relationship between yield of hydroperoxide and (dose-rate)1/2 were indicative of a chain mechanism for peroxidation operating in membranes. Lack of congruence between the amount of oxygen consumed and hydroperoxide formed suggested that the oxygen consumed in membrane oxidation led to the formation of oxidized derivatives of linoleic acid additional to the hydroperoxides. (author)

166

Uptake of Nitric Acid, Dinitrogen Pentoxide, Ozone and The Nitrate Radical On A Single Liquid Drop  

Science.gov (United States)

A novel technique for the investigation of uptake processes on gas-liquid interfaces will be presented. It allows the generation and analysis of single liquid drops inside a flow tube reactor. The in situ analysis of the drop is performed by broad band UV-VIS absorption spectroscopy. Using this set-up the uptake of nitric acid and dinitrogen pentoxide on pure water was measured by monitoring the occurrence of the nitrate band centered at a wavelength of 300 nm. The uptake of ozone on NaI solutions of various concentrations was followed by the formation of the triiodide ion which is a product of the oxidation of iodide by ozone. Using aqueous solutions of the dye Alizarin Red S, the uptake of the nitrate radical could be quantified. In order to extract information on fundamental parameters, e.g. the mass accommo- dation coefficients (= a) of the species, a computer model is applied. It solves the diffusion equation for the transport of gas phase species to the interface numerically. The result is a separation of the influence of this process on the rate of the overall uptake process. The mass accommodation coefficients a > 0.03, a = 0.011 and a > 0.02 were obtained for nitric acid, dinitrogen pentoxide and ozone, respectively.

Schütze, M.; Herrmann, H.

167

[Acidity and interaction with superoxide anion radical of echinochrome and its structural analogs].  

Science.gov (United States)

Weak acid properties, autoxidation and interaction of natural polyhydroxy1,4-naphthoquinones (PHNQ) with superoxide anion-radical (O2-.) were studied by methods of potentiometric titration, polarography, and UV- and visible spectrophotometry. Sea urchin pigments 3-acetyl-2,6,7-trihydroxynaphthazarin (spinochrome C), 2,3,6,7-trihydroxynaphthazarin (spinochrome D), 2,3,6,7-trihydroxynaphthazarin (spinochrome E), 6-ethyl-2,3,7-trihydroxynaphthazarin (echinochrome A), synthetic 2,3-dihydroxy-6,7-dimethylnaphthazarin and 6-ethyl-2,3,7-trimethoxynaphthazarin (trimethoxyechinochrome A) were tested. Determined dissociation constants (pKi) were in the range of pH 5.3-8.5 (40% ethanol solvent). PHNQ autoxidation observrd in basic pH were inhibited by superoxide dismutase. Xanthine and xanthine oxidase was applied for O2-. generation. Interaction with O2-. led to sufficient time-dependent changing in spectra of echinochrome A, spinochromes D and E. There was weak O2-. influence on spinochrome C spectrum and no changing in trimethoxyechinochrome A spectrum. The spectra, that were transforming during time of reaction, contained pronounced isobestic point. It means formation the single reaction product. We proposed formation of 1,2,3,4-tetraketones from 2,3,5,8-tetrahydroxy-1,4-naphthoquinones (echinochrome A, spinochromes D and E) due to O2-.-induced oxidation of their OH-groups in 2 and 3 positions. Reaction constants were determined by competition method using nitro blue tetrazolium (NBT). The reaction constants were about 10(4)-10(5) M-1s-1. They were decreased in the order: echinochrome A > spinochrome D > spinochrome C > NBT > trimethoxyechinochrome A. Thus, we concluded that some of the natural PGNQ, containing hydroxyl groups in 2nd and 3rd positions, could operate as powerful superoxide anion-radical scavengers. PMID:10378300

Lebedev, A V; Ivanova, M V; Krasnovid, N I; Kol'tsova, E A

1999-01-01

168

A Pulse Radiolysis Investigation of the Reactions of Tributyl Phosphate with the Radical Products of Aqueous Nitric Acid Irradiation  

Energy Technology Data Exchange (ETDEWEB)

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 the separation factors for 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 TBP and HDBP with the hydroxyl radical ((5.00 +/- 0.02) x 109, (4.40 +/- 0.10) x 109), hydrogen atom ((1.8 +/- 0.2) x 108, (1.1 +/- 0.1) x 108), nitrate radical ((4.3 +/- 0.7) x 106, (2.9 +/- 0.2) x 106) and nitrite radical (< 2 x 105, < 2 x 105) M-1 s-1 with TBP and HDBP, respectively. These data are used to discuss the mechanism of TBP radical-induced degradation.

Bruce J. Mincher; Stephen R. Mezyk; Leigh R. Martin

2008-07-01

169

A Pulse Radiolysis Investigation of the Reactions of Tributyl Phosphate with the Radical Products of Aqueous Nitric Acid Irradiation  

International Nuclear Information System (INIS)

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 the separation factors for 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 TBP and HDBP with the hydroxyl radical ((5.00 +/- 0.02) x 109, (4.40 +/- 0.10) x 109), hydrogen atom ((1.8 +/- 0.2) x 108, (1.1 +/- 0.1) x 108), nitrate radical ((4.3 +/- 0.7) x 106, (2.9 +/- 0.2) x 106) and nitrite radical (< 2 x 105, < 2 x 105) M-1 s-1 with TBP and HDBP, respectively. These data are used to discuss the mechanism of TBP radical-induced degradation

170

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

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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

171

Physicochemical insights on the free radical scavenging activity of sesamol: importance of the acid/base equilibrium.  

Science.gov (United States)

Reactions of sesamol with different free radicals, in lipid and aqueous media, have been studied at the M05-2X/6-311+G(d,p) level of theory in conjunction with the SMD continuum model. Different mechanisms of reaction have been considered as well as polar and nonpolar environments. According to the overall rate coefficients, sesamol is predicted to react significantly faster in aqueous solution than in nonpolar media. The polarity of the environment also changes the relative importance of the reaction mechanisms. The anionic form of sesamol was found to be particularly reactive toward peroxyl radicals by transferring one electron. This mechanism was found responsible for the exceptional peroxyl radical scavenging activity of sesamol in aqueous solution, which was found to be even better than carotenoids, 2-propenesulfenic acid, and glutathione under physiological conditions. The agreement between experimental and calculated data supports the presented results as well as the methodology used in this work. PMID:21967544

Galano, Annia; Alvarez-Idaboy, Juan Raúl; Francisco-Márquez, Misaela

2011-11-10

172

Phenolic Acid Content and Free Radical-Scavenging Activity of Two Differently Processed Carob Tree (Ceratonia siliqua L. Pod  

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Full Text Available The phenolic acids in free phenolic acid (FPHA, methanol-soluble phenolic ester (MSPE, and methanol-soluble phenolic glycoside (MSPG fractions of two carob products, natural carob-pod flour (CPF and commercial carob-pod flour (CCPF, were identified and quantified using high-performance liquid chromatography-mass spectrometry (HPLC-MS. Six phenolic acids were identified in the carob flours (gallic acid, protocatechuic acid, gentisic acid, syringic acid, p- coumaric acid, and sinapic acid. Gallic acid was the major phenolic acid; and its concentrations in CCPF were substantially higher than in CPF (135 - 166 and 85.2 - 91.3 mg/g dw, respectively. The concentrations of p-coumaric acid and sinapic acid were also higher in CCPF than in CPF. In contrast, the concentrations of protocatechuic acid and gentisic acid were generally lower in CCPF than in CPF, with the only exception being gentisic acid glycosides. Both carob-pod flours contained almost the same amount of sinapic acid and syringic acid. The total phenolic contents of the FPHA, MSPE, and MSPG fractions of CPF were found to be 44%, 38%, and 69% that of the respective fractions of CCPF. Correspondingly, the FPHA, MSPE, and MSPG fractions of CCPF had higher free radical-scavenging activity (28.4%, 33.1%, and 26.2%, respectively than the corresponding fractions of CPF (9.2%, 28.0%, and 9.2%, respectively. Notably, the FPHA and MSPG fractions of each sample had very similar scavenging activity while the MSPE fraction always had higher activity. The FPHA and MSPG fractions of CPF had the lowest activities.

Nesrin Colak

2013-05-01

173

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

174

Thiyl radical-induced cis-trans-isomerization of arachidonic acid inhibits prostaglandin metabolism  

International Nuclear Information System (INIS)

Complete text of publication follows. Thiyl radicals radiolytically generated from thiophenol in methanolic solution are known to isomerise double bonds of poly-unsaturated fatty acids (PUFA). ?-irradiating of such a system containing all-cis 5,8,11,14 eicosatetraenoic acid (arachidonic acid, AA) with low doses (0.1-0.8 kGy) results in a mixture of 8 to 32% mono-trans-isomers. Here we report about the influence of mono-trans-AA on the primary steps of AA-metabolism and prostaglandin synthesis, catalysed by cyclooxygenase (COX). In the cell-free model system the reaction of COX-1 with AA was analysed by controlling the oxygen level during the enzymatic reaction. As an example, a mixture of a low quantity of mono-trans-isomerized AA (10%) and 90% all-cis-isomer exhibits a marked reduced oxygen consumption by 45%. As further proofs - the yield of reactive oxygen species (ROS) generated by the COX-coupled peroxidase reaction was detected, - and the COX-1 activity in presence of different amounts of trans-AA was characterized using a photometric assay based on the oxidation of TMPD. All these methods indicated semiquantitatively a reduced activity of COX-1, depending on the trans-isomer yield. Therefore, an inhibition of COX-1 activity by only one trans-double-bond in AA could be concluded. Furthermore, in vitro cell-line experiments were performed analysing the influence of mono-trans-isomerized AA on the activity of the cell-own COX-2. Hence, VD3-differentiated and LPS-stimulated monocyte-like cells were incubated with mono-trans-AA and ROS-production was detected by the chemiluminescence measurements mentioned above. Compared to the reaction with all-cis-AA we found a considerable lowered formation of ROS. Likewise, we obtained a reduced PGE2-expression between 15 and 40% for cells treated with 8 to 29% trans-AA. The model as well as in vivo experiments demonstrate an inhibition effect of mono-trans-AA and give rise for postulating an enzyme blocking mechanism for COX-1 and COX-2 by trans-isomers

175

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 (degradation. PMID:18572898

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

2008-07-17

176

Free Radical Scavenging Activity of Kielmeyera variabilis (Clusiaceae  

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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

177

Potential Role of Stabilized Criegee Radicals in Sulfuric Acid Production in a High Biogenic VOC Environment.  

Science.gov (United States)

We present field observations made in June 2011 downwind of Dallas-Fort Worth, TX, and evaluate the role of stabilized Criegee radicals (sCIs) in gaseous sulfuric acid (H2SO4) production. Zero-dimensional model calculations show that sCI from biogenic volatile organic compounds composed the majority of the sCIs. The main uncertainty associated with an evaluation of H2SO4 production from the sCI reaction channel is the lack of experimentally determined reaction rates for sCIs formed from isoprene ozonolysis with SO2 along with systematic discrepancies in experimentally derived reaction rates between other sCIs and SO2 and water vapor. In general, the maximum of H2SO4 production from the sCI channel is found in the late afternoon as ozone increases toward the late afternoon. The sCI channel, however, contributes minor H2SO4 production compared with the conventional OH channel in the mid-day. Finally, the production and the loss rates of H2SO4 are compared. The application of the recommended mass accommodation coefficient causes significant overestimation of H2SO4 loss rates compared with H2SO4 production rates. However, the application of a lower experimental value for the mass accommodation coefficient provides good agreement between the loss and production rates of H2SO4. The results suggest that the recommended coefficient for the H2O surface may not be suitable for this relatively dry environment. PMID:25700170

Kim, Saewung; Guenther, Alex; Lefer, Barry; Flynn, James; Griffin, Robert; Rutter, Andrew P; Gong, Longwen; Cevik, Basak Karakurt

2015-03-17

178

In vitro radical scavenging activity of two Columbian Magnoliaceae  

Science.gov (United States)

The recent interest in the conservation of the tropical forest is due, at least in part, to the potential economic and health benefits that can be exploited from several plants. This report shows the in vitro antioxidant activity of some fractions isolated from leaves of two Columbian Magnoliaceae, Talauma hernandezii G. Lozano-C and Dugandiodendron yarumalense Lozano. The activity was determined using the radical monocation 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS·+) and the stable free radical 2-2-diphenyl-1-picrylhydrazyl (DPPH·), as part of general biological screening of these plants. The antioxidant capacity obtained from fractions was similar to those of ?-tocopherol, tert-butylated hydroxyanisole (BHA), and ascorbic acid. The most active scavenger extract was the fraction 7 (TAA = 48.6 mmol Trolox/kg extract and IC50 ? 0.01 kg extract/mmol DPPH); and the least active was the fraction 1 (TAA = 11.23 mmol Trolox/kg extract and IC50 = 0.21 kg extract/mmol DPPH) all of them isolated from D. yarumalense. These results suggest that these plants can be attractive as source of antioxidant compounds with the ability to reduce radicals like ATBS and DPPH.

Puertas M., Miguel A.; Mesa v., Ana M.; Sáez v., Jairo A.

2005-08-01

179

Modification of Cys-418 of pyruvate formate-lyase by methacrylic acid, based on its radical mechanism.  

Science.gov (United States)

The recently determined crystal structure of pyruvate formate-lyase (PFL) suggested a new view of the mechanism of this glycyl radical enzyme, namely that intermediary thiyl radicals of Cys-418 and Cys-419 participate in different ways [Becker, A. et al. (1999) Nat. Struct. Biol. 6, 969-975]. We report here a suicide reaction of PFL that occurs with the substrate-analog methacrylate with retention of the protein radical (K(I)=0.42 mM, k(i)=0.14 min(-1)). Using [1-(14)C]methacrylate (synthesized via acetone cyanhydrin), the reaction end-product was identified by peptide mapping and cocrystallization experiments as S-(2-carboxy-(2S)-propyl) substituted Cys-418. The stereoselectivity of the observed Michael addition reaction is compatible with a radical mechanism that involves Cys-418 thiyl as nucleophile and Cys-419 as H-atom donor, thus supporting the functional assignments of these catalytic amino acid residues derived from the protein structure. PMID:10648809

Plaga, W; Vielhaber, G; Wallach, J; Knappe, J

2000-01-21

180

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

181

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 includes the activity Based Training methodology (ABT for quality management system audit course according to ISO 19011 and ISO 9001. ABT focuses on delivering theoretical content linking directly theory and practice according to the industrial production path of an object. The testing of the theoretical and practical achievements has been done using Student Response System (SRS, by using individual voting systems

Liviu Moldovan

2011-11-01

182

Extraction and Bioactivity Analysis of Major Flavones Compounds from Scutellaria baicalensis Using In Vitro Assay and Online Screening HPLC-ABTS System.  

Science.gov (United States)

The extraction efficiency of a number of solvent compositions for the improvement of bioactive compounds yield from S. baicalensis has been investigated. Also, free radical scavengers in the glycoside baicalin (BG), wogonoside (WG), aglycon baicalein (B), and wogonin (W) compounds of S. baicalensis were screened, identified, and quantified using coupled offline ABTS and online screening HPLC-ABTS assay. Increasing ethanol content fractions resulted in decreased extract yield of bioactive compounds. In this case, the best yield of 37.01?mg/g in BG, WG, B, and W compounds was obtained by a dipping method with an extraction time of 4?h. In addition, the yield (43.05%) and IC50 (34.04??g/mL) determined through ABTS assay of the 60% aqueous ethanol extract were the most satisfactory of all solvent solutions tested. This result shows that an online screening HPLC-ABTS assay can be a powerful technique for the rapid characterization of bioactivity compounds in plant extracts. Moreover, their anti-inflammatory activities were evaluated via analyzed inhibitory effect on NO and inflammatory cytokine production. Furthermore, WG and W exhibited the strong inhibitory effects on inflammatory mediator production including NO, IL-6, and IL-1? in LPS-stimulated RAW 264.7 macrophages. PMID:25258697

Lee, Kwang Jin; Jung, Pil Mun; Oh, You-Chang; Song, Na-Young; Kim, Taesoo; Ma, Jin Yeul

2014-01-01

183

Photoelectron spectroscopy, gas phase acidity, and thermochemistry of tert-butyl hydroperoxide: Mechanisms for the rearrangement of peroxyl radicals  

International Nuclear Information System (INIS)

The 3.531 eV negative ion photoelectron spectra of the hydroperoxide ion and the tert-butylperoxide ion have been studied. We find HO2-+??351.1-nm?HO2+e- EA[HO2,X-2Adouble-prime]=1.089±0.006-eV, (CH3)3COO-+??351.1thinspnm?(CH3)3COO+e- EA[(CH3)3COO,X-2Adouble-prime]=1.196±0.011-eV. The photoelectron spectra show detachment to the ground state of the peroxyl radicals and to a low lying electronic state. The intercombination gaps are measured to be ?E(X-2Adouble-prime-A-2A')[HO2]=0.871±0.007-eV and ?E(X-2Adouble-prime - 2A')[(CH3)3COO]=0.967±0.011 eV. The gas phase acidity of (CH3)3COOH was measured in a tandem flowing afterglow-selected ion flow tube (FA-SIFT) to be ?acidG298=363.2±2.0-kcal-mol-1 and we find ?acidH298[(CH3)3COO - H]=370.9±2.0-kcal-mol-1. Use of ?acidH298[(CH3)3COO - H] and EA[(CH3)3COO] leads to the bond energies DH298[(CH3)3COO - H]=85±2-kcal-mol-1 and D0[(CH3[(CH3)3COO - H]=83±2-kcal-mol-1. The thermochemistry of the alkylperoxyl radicals, RO2, is reviewed. A mechanism for the rearrangement of chemically activated peroxyl radicals is proposed [RO2]X-2Adouble-prime?[RO2]*A-2A'?aldehydes/ke

184

[Antioxidant and prooxidant properties of the ascorbic acid, dihydroquercetine and mexidol in the radical reactions induced by the ionizing radiation and chemical reagents].  

Science.gov (United States)

Antioxidant and prooxidant properties of dihydroquercetine, mexidol and an ascorbic acid in reactions with participation of radicals OH* and O2(-)*, induced by gamma-irradiation, iron-catalyzed decomposition of hydrogen peroxide and oxidation of reduced NADH by phenazine metosulfate are investigafed. The efficiency of scavenging of radicals OH* estimated by the results of the analysis of deoxyribose degradation, and the efficiency of scavenging of superoxide anion-radicals O2(-)* is estimated by the results of the analysis of occurrence the reduced nitrotetrazolium blue. The concentrations of analyzed compounds, scavenging on 50% (C50%) formation of radicals OH* and O2(-)* are certain. It is shown, that an ascorbic acid, dihydroquercetine and mexidol decrease the generating of superoxide anion-radicals O2(-)* in the gamma-irradiated solutions of sodium format and at oxidation of reduced NADH by phenazine metosulfate scavanged of superoxide anion-radicals O2(-)*. In the gamma-irradiated saline solutions an ascorbic acid, dihydroquercetine and mexidol protected deoxyribose from oxidizing action of hydroxyl radicals OH*. However at presence Fe(3+), EDTA and hydrogen peroxide addition of an ascorbic acid (0.1 mmol/l) increased generating of hydroxyl radicals OH* and in 2.8 times raised the maintenance of products of deoxyribose oxidation, reacting with thiobarbituric acid. Prooxidant action of an ascorbic acid is observed as well in absence of hydrogen peroxide. Obtained data testify that in various modelling systems reagents, in particular ions of iron, and the formed active intermediate products render significant influence on scavenging efficiency of investigated compounds. PMID:20464967

Riabchenko, N I; Riabchenko, V I; Ivannik, B P; Dzikovskaia, L A; Sin'kova, R V; Grosheva, I P; Degtiareva, E S; Ivanova, T I

2010-01-01

185

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)

186

The interaction of OH radicals with aromatic alcohols, aldehydes, hydroperoxides and acids  

International Nuclear Information System (INIS)

The reactions of OH radicals generated by ?-radiation with oxygen containing derivatives of toluene and p-xylene were studied at room temperature in neutral aqueous solutions. The aim of the work was to clear the consecutivity of reactions in overall mechanism and to determine their rate constants. The rate constant of the interaction between OH radicals and the various substances were determined in competitive reactions by addition of various amounts of t-butanol or anisole to the solution and calculated by the usual way. (author)

187

Reactions of amino acids, peptides, and proteins with oxidized metabolites of tris(p-carboxyltetrathiaaryl)methyl radical EPR probes.  

Science.gov (United States)

Oxidation of the tris(p-carboxyltetrathiaaryl)methyl (TAM) EPR radical probe, TAMa(•), by rat liver microsomes (RLM) + NADPH, or horseradish peroxidase (HRP) + H2O2, or K2IrCl6, led to an intermediate cation, TAMa(+), which was treated with glutathione (GSH), with formation of an adduct, TAMa-SG(•), resulting from the substitution of a TAMa(•) carboxylate group with the SG group. L-?-Amino acids containing a strong nucleophilic residue (NuH), such as L-cysteine or L-histidine, also reacted with TAMa(+), with formation of radical adducts TAMa-Nu(•) in which a carboxylate group of TAMa(•) was replaced with Nu. Other less nucleophilic L-?-amino acids, such as L-arginine, L-serine, L-threonine, L-tyrosine, or L-aspartate, as well as the tetrapeptide H-(Gly)4-OH, reacted with TAMa(+) via their ?-NH2 group, with formation of an iminoquinone methide, IQMa, deriving from an oxidative decarboxylation and amination of TAMa(•). Upon reaction of TAMa(+) with L-proline and L-lysine, N-substituted iminoquinone methide adducts, IQMa-Pro and IQMa-Lys, were formed. Finally, preliminary results showed that oxidation of TAMa(•) in the presence of bovine serum albumin (BSA), led to the covalent binding of TAMa-derived metabolites to BSA. Oxidation of another frequently used TAM probe, TAMb(•) (Oxo63), in the presence of GSH, N-acetyl-cysteine methyl ester, or histidine also led to TAMb-Nu(•) adducts equivalent to the corresponding TAMa-Nu(•) adducts, suggesting that the oxidative metabolism of such TAM(•) probes could lead to protein covalent binding. Moreover, the above data describe an easy access to new TAM radical EPR probes coupled to amino acids, peptides or proteins that could be useful for addressing various biological targets. PMID:24564180

Decroos, Christophe; Boucher, Jean-Luc; Mansuy, Daniel; Xu-Li, Yun

2014-04-21

188

Reactions of OH-radicals with hydroxylated and methoxylated benzoic acids and cinnamic acids. Radiation-induced chemical changes in mushrooms  

International Nuclear Information System (INIS)

In the first part of this work the radiation induced chemical changes of methoxylated and hydroxylated benzoic acids and cinnamic acids were investigated. Methoxylated compounds were also used as model components for acid derivatives with no free-OH groups. The latter are essentials parts of vegetable foodstuff. A comparison of the radiolytic behaviour of single substituted methoxy- and hydroxybenzoic acids was given at first, data of literature was included. The priority of the investigation was the hydroxylation process induced by OH-radicals. The OH-adduct distribution is generally the same for the hydroxy- as well as for the methoxybenzoic acid isomers. This could be proved by oxidation of these OH-adducts with K3Fe(CN)6. In the presence of air 68-77 % of the hydroxybenzoic acids are converted into hydroxylation products, whereas with the methoxylated acids this reaction leads only to about 10%. An explanation gives the different decay pathways of the intermediate peroxylradical. The multiple methoxy- and hydroxybenzoic acids show three different reaction possibilities: hydroxylation, replacement of -OCH3 by -OH and -in case of the cinnamic acids-oxidative decomposition of the rest of the propenic acid under formation of the corresponding benzaldehydes. All these reactions can be expected when irradiating foodstuff, containing these acid compounds. The characteristic formation of these components and their linear dose/concentrationonents and their linear dose/concentration relationship make these substrates very promising for the use as markers for irradiation treatment of foodstuff. The second part of this work deals with the gamma-radiation induced chemical changes in mushrooms. The irradiated and non-irradiated samples were freeze-dried and purified from matrix components chromatographically on polyamid columns. In case of the phenolic compounds for 4-hydroxybenzoic acid and three unknown components linear dose/concentration relationships could be obtained. Two of these unknown compounds seem to be promising for a use as marker for irradiation treatment of mushrooms. (author)

189

Block-gradient copolymers of styrene and acrylic acid synthesized by nitroxide-mediated radical polymerization.  

Czech Academy of Sciences Publication Activity Database

Granada : European Polymer Federation, 2011. s. 513. ISBN 978-84-694-3124-5. [European Polymer Congress 2011, Congress of the Specialized Group of Polymers /12./. 26.06.2011-01.07.2011, Granada] Institutional research plan: CEZ:AV0Z40500505 Keywords : block-gradient copolymers * radical polymerization Subject RIV: CD - Macromolecular Chemistry

Borisova, O.; Billon, L.; Zaremski, M.; Grassl, B.; Bakaeva, Zulfiya; Lapp, A.; Št?pánek, Petr; Borisov, O.

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

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

192

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)

193

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

194

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

Science.gov (United States)

The reactions of OH radicals with 2-, 3-, 4-chlorobenzoic acids (ClBzA) and chlorobenzene (ClBz), k( rad OH+substrates)=(4.5-6.2)×10 9 dm 3 mol -1 s -1, have been studied by pulse radiolysis in N 2O 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, 2 k=(1-9)×10 8 dm 3 mol -1 s -1. In the presence of N 2O/O 2 the formation of peroxyl radicals was detectable for 2-, 4-ClBzA and ClBz, k(OH-adduct+O 2)=(2-4)×10 7 dm 3 mol -1 s -1, while this reaction for 3-ClBzA was too slow to be registered. In the presence of N 2O 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 ˜60% of rad OH 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; Solar, Sonja; Getoff, Nikola; Sehested, Knud; Holcman, Jerzy

2010-05-01

195

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

DEFF Research Database (Denmark)

The reactions of OH radicals with 2-, 3-, 4-chlorobenzoic acids (ClBzA) and chlorobenzene (ClBz), k(OH+substrates)=(4.5?6.2)×109 dm3 mol?1 s?1, have been studied by pulse radiolysis in N2O 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)×108 dm3 mol?1 s?1. In the presence of N2O/O2 the formation of peroxyl radicals was detectable for 2-, 4-ClBzA and ClBz, k(OH-adduct+O2)=(2?4)×107 dm3 mol?1 s?1, while this reaction for 3-ClBzA was too slow to be registered. In the presence of N2O 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 60% of OH 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; Solar, Sonja

2010-01-01

196

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

197

Chemical composition of the essential oil of Ligularia hodgsonii and free radical scavenging activity of the oil and crude extracts.  

Science.gov (United States)

The chemical composition of the essential oil from roots and rhizomes of Ligularia hodgsonii was analyzed by gas chromatography (GC) and GC-mass spectrometry (MS). Forty-seven components were identified, representing 77.0% of the total oil. The main constituents were l-(+)-ascorbic acid 2,6- dihexadecanoate (15.7%), selina-6-en-4-ol (8.4%) and 9,10-dimethyl-1,2,3,4,5,6,7,8-octahydroanthracene (6.6%). The free radical scavenging activities of the essential oil, aqueous extract, ethanolic extract, and crude polysaccharides of L. hodgsonii, as well as some of their major components, were investigated using DPPH and ABTS assays. The essential oil displayed a lower capacity to quench free radicals than the extracts; the ethanolic and aqueous extracts showed considerably higher antioxidant potential that deserves further study. PMID:25522549

Zhou, Zihao; Tang, Jun; Song, Xueping

2014-10-01

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

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

200

Comparison of the capacities of the perhydroxyl and the superoxide radicals to initiate chain oxidation of linoleic acid  

International Nuclear Information System (INIS)

Since data are accumulating that seem to dispute the role of O2- as a potent agent of biological damage, a study of the previously ignored conjugate acid, the perhydroxyl radical (HO2), a transient species always formed in the presence of O2- in H2O, was undertaken. The results of the systematic studies of the reaction rates of HO2/O2- with a number of biochemicals as a function of pH are tabulated. The data indicated that HO2 reacts faster than O2- with all of the compounds, and the reaction conditions are such that its presence is always assured. The reaction of HO2 with linoleic acid (a C18 unsaturated fatty acid with 2 double bonds) was studied in detail using HO2 formed from O2- generated by photolysis of oxygenated alkaline ethanol solutions in a special apparatus previously described. The present work does not answer the question whether the oxidation of linoleic acid and probably other polyunsaturated fatty acids by HO2 can lead to biological damage, but it can be assumed now that the most obvious sites for damage are the plasma and intracellular membranes

201

Apigenin sensitizes colon cancer cells to anti-tumor activity of ABT-263  

OpenAIRE

Apigenin is an edible plant-derived flavonoid that shows modest anti-tumor activities in vitro and in vivo. Apigenin treatment resulted in cell growth arrest and apoptosis in various types of tumors by modulating several signaling pathways. In the present study, we evaluated interactions between apigenin and ABT-263 in colon cancer cells. We observed a synergistic effect between apigenin and ABT-263 on apoptosis of colon cancer cells. ABT-263 alone induced limited cell death while upregulatin...

Shao, Huanjie; Jing, Kai; Mahmoud, Esraa; Huang, Haihong; Fang, Xianjun; Yu, Chunrong

2013-01-01

202

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

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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

203

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

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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

204

Bcl-2, Bcl-xL, and Bcl-w are not equivalent targets of ABT-737 and navitoclax (ABT-263) in lymphoid and leukemic cells  

OpenAIRE

The BH3-mimetic ABT-737 and an orally bioavailable compound of the same class, navitoclax (ABT-263), have shown promising antitumor efficacy in preclinical and early clinical studies. Although both drugs avidly bind Bcl-2, Bcl-xL, and Bcl-w in vitro, we find that Bcl-2 is the critical target in vivo, suggesting that patients with tumors overexpressing Bcl-2 will probably benefit. In human non-Hodgkin lymphomas, high expression of Bcl-2 but not Bcl-xL predicted sensitivity to ABT-263. Moreover...

Me?rino, Delphine; Khaw, Seong L.; Glaser, Stefan P.; Anderson, Daniel J.; Belmont, Lisa D.; Wong, Chihunt; Yue, Peng; Robati, Mikara; Phipson, Belinda; Fairlie, Walter D.; Lee, Erinna F.; Campbell, Kirsteen J.; Vandenberg, Cassandra J.; Cory, Suzanne; Roberts, Andrew W.

2012-01-01

205

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

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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

206

Decarbonylative radical coupling of ?-aminoacyl tellurides: single-step preparation of ?-amino and ?,?-diamino acids and rapid synthesis of gabapentin and manzacidin?A.  

Science.gov (United States)

A new radical-based coupling method has been developed for the single-step generation of various ?-amino acids and ?,?-diamino acids from ?-aminoacyl tellurides. Upon activation by Et3 B and O2 at ambient temperature, ?-aminoacyl tellurides were readily converted into ?-amino carbon radicals through facile decarbonylation, which then reacted intermolecularly with acrylates or glyoxylic oxime ethers. This mild and powerful method was effectively incorporated into expeditious synthetic routes to the pharmaceutical agent gabapentin and the natural product (-)-manzacidin?A. PMID:25504989

Nagatomo, Masanori; Nishiyama, Hayato; Fujino, Haruka; Inoue, Masayuki

2015-01-26

207

Vinblastine rapidly induces NOXA and acutely sensitizes primary chronic lymphocytic leukemia cells to ABT-737.  

Science.gov (United States)

Proteins of the BCL2 family provide a survival mechanism in many human malignancies, including chronic lymphocytic leukemia (CLL). The BCL2 inhibitor ABT-263 (navitoclax) is active in clinical trials for lymphoid malignancies, yet resistance is expected on the basis of preclinical models. We recently showed that vinblastine can dramatically sensitize several leukemia cell lines to ABT-737 (the experimental congener of ABT-263). The goal of these experiments was to determine the impact of vinblastine on ABT-737 sensitivity in CLL cells isolated from peripheral blood and to define the underlying mechanism. Freshly isolated CLL cells from 35 patients, as well as normal lymphocytes and platelets, were incubated with various microtubule-disrupting agents plus ABT-737 to assess sensitivity to the single agents and the combination. ABT-737 and vinblastine displayed a range of sensitivity as single agents, and vinblastine markedly sensitized all CLL samples to ABT-737 within six hours. Vinblastine potently induced the proapoptotic protein PMAIP1 (NOXA) in both time- and dose-dependent manner and this was required for the observed apoptosis. Combretastatin A4, which dissociates microtubules by binding to a different site, had the same effect, confirming that interaction of these agents with microtubules is the initial target. Similarly, vincristine and vinorelbine induced NOXA and enhanced CLL sensitivity to ABT-737. Furthermore, vinblastine plus ABT-737 overcame stroma-mediated resistance to ABT-737 alone. Apoptosis was induced with clinically achievable concentrations with no additional toxicity to normal lymphocytes or platelets. These results suggest that vinca alkaloids may improve the clinical efficacy of ABT-263 in patients with CLL. PMID:23723123

Bates, Darcy J P; Danilov, Alexey V; Lowrey, Christopher H; Eastman, Alan

2013-08-01

208

Simultaneous determination of ABT-888, a poly (ADP-ribose) polymerase inhibitor, and its metabolite in human plasma by liquid chromatography/tandem mass spectrometry.  

Science.gov (United States)

A reversed-phase liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) method was developed and validated for simultaneous determination of ABT-888 and its major metabolite (M8) in human plasma. Sample preparation involved a liquid-liquid extraction by the addition of 0.25 ml of plasma with 10 microl of 1 M NaOH and 1.0 ml ethyl acetate containing 50 ng/ml of the internal standard zileuton. The analytes were separated on a Waters XBridge C(18) column using a gradient mobile phase consisting of methanol/water containing 0.45% formic acid at the flow rate of 0.2 ml/min. The analytes were monitored by tandem mass spectrometry with electrospray positive ionization. Linear calibration curves were generated over the ABT-888 and M8 concentration ranges of 1-2000 ng/ml in human plasma. The lower limits of quantitation (LLOQ) were 1 ng/ml for both ABT-888 and M8 in human plasma. The accuracy and within- and between-day precisions were within the generally accepted criteria for bioanalytical method (<15%). This method was successfully employed to characterize the plasma concentration-time profile of ABT-888 after its oral administration in cancer patients. PMID:20005184

Wiegand, Richard; Wu, Jianmei; Sha, Xianyi; LoRusso, Patricia; Li, Jing

2010-02-01

209

Combination treatments with ABT-263 and an immunotoxin produce synergistic killing of ABT-263-resistant Small Cell Lung Cancer cell lines  

OpenAIRE

Synergistic killing was achieved when Small Cell Lung Cancer (SCLC) cell lines were incubated with ABT-263 and an immunotoxin directed to the transferrin receptor. SCLC lines are variably sensitive to the BH-3 only peptide mimetic, ABT-263. To determine their sensitivity to toxin-based reagents, we incubated four representative SCLC lines with a model Pseudomonas exotoxin-based immunotoxin directed to the transferrin receptor. Remarkably in 4-of-4 lines, there was little evidence of immunotox...

Mattoo, Abid R.; Fitzgerald, David

2012-01-01

210

Investigation into the reaction of OH radical with m-aminobenzoic acid in aqueous solution by the pulse radiolysis method  

International Nuclear Information System (INIS)

The reaction of OH radical with m-aminobenzoic acid (ABA) in aqueous solution is studied by the method of pulse radiolysis with optical registration of short lived particles. The rate constants of ABA reaction with esub(ag) and OH are determined. They are (5.6+-0.5)x109 and (9.5+-1.0)x109 l/molxs, respectively. The optical characteristics of OH-adducts of ABA (in neutral medium lambda = 370 nm and epsilonsub(max) (3.7+-0.5)x103 l/molxs) are measured. The kinetics of OH-adducts disappearence is studied. It is found that it disappears in processes of the first and second orders. The ammonia split-out is shown to be one of the processes of the first order. It is confirmed by NH3 presence among the products of ?-radiolysis of ABA aqueous solutions

211

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

212

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

213

Pulse radiolytic and product analysis studies of the reaction of hydroxyl radicals with cinnamic acid. The relative extent of addition to the ring and side chain  

Energy Technology Data Exchange (ETDEWEB)

Using pulse radiolysis with optical detection and high-pressure liquid chromatography (HPCL), it has been shown that reaction of OH radicals with cinnamic acid (CA in aqueous solutions leads to addition to both the ring and the olefinic group. The relative extent of the above two pathways was estimated as 3:7, respectively. Benzyl- and hydroxycyclohexadienyl-type radicals were observed with absorption maxima at 320 (310) and 370 (365) nm depending on the pH of the solution. In the pH region 4.9 to 5.7 the absorption at 305 to 315 nm decays during the first 5 ..mu..s after the pulse. The dependence of the rate constants and absorption spectra on pH suggests that this decay is due to an equilibration process between acid-base forms of benzyl-type radicals formed through OH addition to te olefinic group.

Bobrowski, K.; Raghavan, N.V.

1982-10-28

214

The ratio of oleic-to-stearic acid in the prostate predicts biochemical failure after radical prostatectomy for localized prostate cancer  

Science.gov (United States)

Our study examined lifestyle-related factors that may influence the prognosis of clinically localized prostate cancer, we evaluated the relative impact of obesity and prostatic fatty acid concentrations at diagnosis on risk of biochemical failure following radical prostatectomy. Height and weight w...

215

Degradation of Acid Orange 7 by electrochemically generated (*)OH radicals in acidic aqueous medium using a boron-doped diamond or platinum anode: a mechanistic study.  

Science.gov (United States)

A comparative study of the degradation of Acid Orange 7 (AO 7) aqueous solutions in acidic medium of pH 3.0 by electro-Fenton process using Pt or boron-doped diamond (BDD) anode was reported. The oxidative degradation of AO 7 by electrochemically generated hydroxyl radicals follows a pseudo-first order kinetic with a similar rate constant with BDD or Pt anode. The absolute rate constant of the AO 7 hydroxylation reaction was determined as (1.10+/-0.04)x10(10)M(-1)s(-1) by using the competition kinetic method. The comparative study of TOC measurements during electro-Fenton treatment showed a higher mineralization rate with BDD than Pt anode at the first hours of electrolysis because of the higher oxidizing power of this anode. The electro-Fenton degradation of AO 7 was followed by monitoring the formation and evolution of aromatic intermediates which are oxidized to aliphatic carboxylic acids before mineralization (transformation to CO(2) and inorganic ions, i.e. sulphate, nitrate and ammonium). The follow-up of the solution toxicity evolution shows the formation of intermediates more toxic than AO 7 and the connection between toxicity and aromaticity. A mineralization reaction pathway of AO 7 by electro-Fenton degradation involving all the intermediates identified was proposed. PMID:18760822

Hammami, Samiha; Bellakhal, Nizar; Oturan, Nihal; Oturan, Mehmet A; Dachraoui, Mohamed

2008-10-01

216

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)

217

Phytochemical Analysis and Free Radical Scavenging Activity of Medicinal Plants Gnidia glauca and Dioscorea bulbifera  

OpenAIRE

Gnidia glauca and Dioscorea bulbifera are traditional medicinal plants that can be considered as sources of natural antioxidants. Herein we report the phytochemical analysis and free radical scavenging activity of their sequential extracts. Phenolic and flavonoid content were determined. Scavenging activity was checked against pulse radiolysis generated ABTS•+ and OH radical, in addition to DPPH, superoxide and hydroxyl radicals by biochemical methods followed by principal component analysi...

Ghosh, Sougata; Derle, Abhishek; Ahire, Mehul; More, Piyush; Jagtap, Soham; Phadatare, Suvarna D.; Patil, Ajay B.; Jabgunde, Amit M.; Sharma, Geeta K.; Shinde, Vaishali S.; Pardesi, Karishma; Dhavale, Dilip D.; Chopade, Balu A.

2013-01-01

218

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  

OpenAIRE

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 spec...

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

2011-01-01

219

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

220

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

Directory of Open Access Journals (Sweden)

Full Text Available 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

2008-03-01

221

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

222

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

223

The BH3-mimetic ABT-737 effectively kills acute myeloid leukemia initiating cells  

Science.gov (United States)

The anti-apoptotic proteins Bcl-XL and Bcl-2 are abundantly expressed in hematopoietic stem cells and/or progenitor cells. Furthermore, leukemic cells expressing these proteins are enriched in minimal residual disease cell populations. This prompted us to test the BH3-mimetic compound ABT-737 for its ability to eradicate putative leukemic stem cells. ABT-737 demonstrated potent cytotoxic effects in all patient samples tested. The efficacy of ABT-737 against AML blasts and the primitive CD34+/CD38? population was equal and independent of sensitivity to cytarabine/daunorubicin. These results, together with previously reported synergistic effects of ABT-737 with chemotherapeutics make BH3-mimetics promising candidates for future AML treatment regimens. PMID:25379408

Baev, Denis V.; Krawczyk, Janusz; O?Dwyer, Michael; Szegezdi, Eva

2014-01-01

224

77 FR 68769 - Access to Confidential Business Information by Abt Associates, Inc.  

Science.gov (United States)

...of Cambridge, MA, to access information which has been submitted...be Confidential Business Information (CBI). DATES: Access to the confidential data...Abt's personnel were given access to information submitted to EPA under...

2012-11-16

225

Formation of the OOH(·) radical at steps of the boehmite surface and its inhibition by gallic acid: A theoretical study including DFT-based dynamics.  

Science.gov (United States)

The ability of boehmite surface to stabilize reactive oxygen species (ROS) was investigated with density functional theory (DFT) calculations. We provide evidence that the O2(·-)radical is stabilized at the AlOOH boehmite terrace defect-free surface, and that step favors the formation of the OOH(·) radical without activation energy required. These tendencies are confirmed when considering the explicit presence of water solvent. We propose that gallic acid (GA), a non-expensive, non-toxic, natural product and radical scavenger, may form a full layer on the (101) stepped boehmite surface. The quenching of O2- to OOH(·) reaction on the GA-functionalized boehmite surface is investigated. It is shown that gallic acid passivates the surface and that the formation of the OOH(·) radical is consequently inhibited. The interaction of the GA-functionalized boehmite surface with water mimicking the body fluid is also investigated by means of DFT-based molecular dynamics simulations at room temperature. Hydrogen bonds between the functionalized GA layer and the immediate interfacial water are characterized. PMID:23958223

Ribeiro, T; Motta, A; Marcus, P; Gaigeot, M-P; Lopez, X; Costa, D

2013-11-01

226

Growth of ABT-5 bacteria culture in whey supplemented with whey protein concentrate  

OpenAIRE

The objective of this research was to decrease the duration of whey fermentation and to analyze the impact of whey protein concentrates (WPC) addition on growth and activity as well as on survival of mixed ABT-5 culture bacteria (Lactobacillus acidophilus, Bifidobacterium spp. and Streptococcus thermophilus) during 28 days of fermented whey cold storage (5 °C). Whey fermentation was observed at 37 °C with and without 1.5 and 3 % WPC addition. Whey fermentation with mixed ABT-5 bacterial cul...

Bojan Matijevi?; Rajka Božani?; Ljubica Tratnik

2010-01-01

227

Combining Paclitaxel with ABT-263 Has a Synergistic Effect on Paclitaxel Resistant Prostate Cancer Cells  

Science.gov (United States)

We assessed the capability of paclitaxel, one of the taxanes, to induce death in two prostate cancer lines, LNCaP and PC3. Paclitaxel drove an apoptotic pathway in LNCaP, but not in PC3 cells, in response to G2/M arrest. An examination of the levels of anti-apoptotic proteins revealed that Bcl-xl was much higher in PC3 cells than in LNCaP cells and Bcl2 could be detected only in PC3 cells, not in LNCaP cells. Knocking down Bcl-xl enhanced paclitaxel-induced apoptosis in LNCaP cells, while we were unable to knock down Bcl-xl efficiently in PC3 cells. Significantly, a comparison of ABT-263, a specific inhibitor of Bcl2 and Bcl-xl, with ABT-199, a Bcl2 selective inhibitor, disclosed that only ABT-263, not ABT-199, could induce apoptosis in LNCaP and PC3 cells. The results indicate that Bcl-xl has a protective role against paclitaxel-induced apoptosis in LNCaP and PC3 cells, and its overexpression causes the paclitaxel resistance seen in PC3 cells. Interestingly, combined paclitaxel with ABT-263 to treat LNCaP and PC3 cells demonstrated synergistic apoptosis activation, indicating that ABT-263 could enhance paclitaxel-induced apoptosis in LNCaP cells and overcome Bcl-xl overexpression to trigger paclitaxel-induced apoptosis in PC3 cells. We also observed that the activation of apoptosis in LNCaP cells was more efficient than in PC3 cells in response to paclitaxel plus ABT-263 or to ABT-263 alone, suggesting that the apoptosis pathway in PC3 cells might have further differences from that in LNCaP cells even after Bcl-xl overexpression is accounted for. PMID:25811469

Wang, Chihuei; Huang, Shih-Bo; Yang, Min-Chi; Lin, Yi-Tsen; Chu, I-Hung; Shen, Ya-Ni; Chiu, Yueh-Ho; Hung, Shao-Hung; Kang, Lin; Hong, Yi-Ren; Chen, Chung-Hwan

2015-01-01

228

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

229

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

230

Radical scavenging and antioxidant activities of methanolic extracts from Hypericum species growing in Bulgaria  

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Full Text Available Thirteen Hypericum species growing in Bulgaria were investigated for free radical-scavenging activity, antioxidant activity, total tannins and total flavonoids contents. Methanolic extracts from the Hypericum species were analyzed for radical scavenging and antioxidant activities using DPPH-, ABTS- free radicals, total antioxidant activity and inhibition of lipid peroxidation by ferric thiocyanate (FTC method. Butylated hydroxytoluene and ascorbic acid were used as positive controls. Methanolic extracts from H. cerastoides, H. perforatum and H. maculatum demonstrate the highest antioxidant activities and are potential sources of natural antioxidant compounds. The quantification of tannins and flavanoids were determined in Hypericum species using Folin-Chiocalteu reagent and AlCl3, respectively. The amounts of the tannins ranged from 1.30 ± 0.01 mg/100 g dw in H. elegans to 8.67 ± 0.02 g/100 g dw in H. perforatum. The highest concentration of flavonoids was found in H. cerastoides (1.22 ± 0.02 g/100g dw, and the lowest amount was established in H. olympicum (0.20 ± 0.03 g/100g dw.

Zheleva-Dimitrova Dimitrina

2010-04-01

231

Radical scavenging and antioxidant activities of methanolic extracts from Hypericum species growing in Bulgaria.  

Science.gov (United States)

Thirteen Hypericum species growing in Bulgaria were investigated for free radical-scavenging activity, antioxidant activity, total tannins and total flavonoids contents. Methanolic extracts from the Hypericum species were analyzed for radical scavenging and antioxidant activities using DPPH-, ABTS- free radicals, total antioxidant activity and inhibition of lipid peroxidation by ferric thiocyanate (FTC) method. Butylated hydroxytoluene and ascorbic acid were used as positive controls. Methanolic extracts from H. cerastoides, H. perforatum and H. maculatum demonstrate the highest antioxidant activities and are potential sources of natural antioxidant compounds. The quantification of tannins and flavanoids were determined in Hypericum species using Folin-Chiocalteu reagent and AlCl3, respectively. The amounts of the tannins ranged from 1.30 +/- 0.01 mg/100 g dw in H. elegans to 8.67 +/- 0.02 g/100 g dw in H. perforatum. The highest concentration of flavonoids was found in H. cerastoides (1.22 +/- 0.02 g/100g dw), and the lowest amount was established in H. olympicum (0.20 +/- 0.03 g/100g dw). PMID:20668569

Zheleva-Dimitrova, Dimitrina; Nedialkov, Paraskev; Kitanov, Gerassim

2010-04-01

232

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

233

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

OpenAIRE

AbstractPoly(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 c...

Babu Kothandapani; Dhamodharan Raghavachari

2008-01-01

234

Free Radical Scavenging Profile and Myeloperoxidase Inhibition of Extracts from Antidiabetic Plants: Bauhinia forficata and Cissus sicyoides  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in english 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 radicáis and other reactive species faster than biological substrates do. The aim of the prese [...] nt 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 anión radical (0(2)•-) scavenging and myeloperoxidase (MPO) activity. In the ABTS assay for total antioxidant activity, B. forficata showed IC50 = 8.00±0.07 ?g/mL, while C. sicyoides showed IC50 = 13.0±0.2 ?g/mL. However, the extract of C. sicyoides had a stronger effect on 0(2)•- (IC50 = 60.0±2.3 ?g/mL) than the extract of B. forficata (IC50 = 90.0±4.4 ?g/ 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.

NAJEH M, KHALIL; MARIA T, PEPATO; IGUATEMY L, BRUNETTI.

235

Formation of 7-carboxyheptyl radical induced by singlet oxygen in the reaction mixture of oleic acid, riboflavin and ferrous ion under the UVA irradiation  

OpenAIRE

Identification of the radicals was performed for the standard reaction mixtures, which contained 4.3 mM oleic acid, 25 µM riboflavin, 1 mM FeSO4(NH4)2SO4, 10 mM cholic acid, 40 mM phosphate buffer (pH 7.4) and 0.1 M ?-(4-pyridyl-1-oxide)-N-tert-butylnitrone under the UVA irradiation (365 nm), using an electron spin resonance, an high performance liquid chromatography-electron spin resonance and an high performance liquid chromatography-electron spin resonance-mass spectrometry. The ...

Mori, Hiroko; Iwahashi, Hideo

2011-01-01

236

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 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

237

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

238

Lag-time measurement of antioxidant capacity using myoglobin and 2, 2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid): rationale, application, and limitation.  

Science.gov (United States)

The application of a simple lag-time assay for antioxidant capacity using myoglobin and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) or ABTS has been studied for its general application conditions. In the presence of an antioxidant, the ABTS(*+) radical-cation-forming chromogenic reaction, catalyzed by myoglobin and initiated by hydrogen peroxide (H(2)O(2)), has a lag period, and its duration is linearly correlated to the concentration of that antioxidant. The high linearity between the lag time and the antioxidant concentration remained unchanged regardless of the assay conditions. It was also found that the linearity was better for antioxidants at lower concentrations. The change of assay condition could significantly affect the relative antioxidant value of a chemical to the standard (ascorbic acid), although not to a large extent. Most of antioxidants investigated were found suitable to be assayed using this method. Some antioxidants, e.g., genistein, however, were not, probably due to their low reactivity toward ferrylmyoglobin or ABTS(*+). In conclusion, the lag-time assay is a reliable method for measuring the antioxidant capacity, provided caution is taken for antioxidants that mainly act through lowering the rate of the chromogenic reaction. PMID:10552907

Yu, T W; Ong, C N

1999-11-15

239

Physiology of free radicals  

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Full Text Available Free radicals imply that every atom, molecule, ion, group of atoms, or molecules with one or several non-paired electrons in outer orbital. Among these are: nitrogenoxide (NO•, superoxide-anion-radical (O2•-, hydroxyl radical (OH•, peroxyl radical (ROO•, alcoxyl radical (RO• and hydroperoxyl radical (HO2•. However, reactive oxygen species also include components without non-paired electrons in outer orbital (so-called reactive non-radical agents, such as: singlet oxygen (1O2, peroxynitrite (ONOO-, hydrogen-peroxide (H2O2, hypochloric acid (eg. HOCl and ozone (O3. High concentrations of free radicals lead to the development of oxidative stress which is a precondition for numerous pathological effects. However, low and moderate concentrations of these matter, which occur quite normally during cell metabolic activity, play multiple significant roles in many reactions. Some of these are: regulation of signal pathways within the cell and between cells, the role of chemoattractors and leukocyte activators, the role in phagocytosis, participation in maintaining, changes in the position and shape of the cell, assisting the cell during adaption and recovery from damage (e.g.caused by physical effort, the role in normal cell growth, programmed cell death (apoptosis and cell ageing, in the synthesis of essential biological compounds and energy production, as well as the contribution to the regulation of the vascular tone, actually, tissue vascularization.

Stevanovi? Jelka

2011-01-01

240

Antiradical activity of gallic acid included in lipid interphases.  

Science.gov (United States)

Polyphenols are well known as antioxidant agents and by their effects on the hydration layers of lipid interphases. Among them, gallic acid and its derivatives are able to decrease the dipole potential and to act in water as a strong antioxidant. In this work we have studied both effects on lipid interphases in monolayers and bilayers of dimyristoylphosphatidylcholine. The results show that gallic acid (GA) increases the negative surface charges of large unilamellar vesicles (LUVs) and decreases the dipole potential of the lipid interphase. As a result, positively charged radical species such as ABTS(+) are able to penetrate the membrane forming an association with GA. These results allow discussing the antiradical activity (ARA) of GA at the membrane phase which may be taking place in water spaces between the lipids. PMID:24998361

Salcedo, C L; Frías, M A; Cutro, A C; Nazareno, M A; Disalvo, E A

2014-10-01

241

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

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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

242

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 MS3 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 MS3 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.

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

2012-08-01

243

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

Energy Technology Data Exchange (ETDEWEB)

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 mm{sup 3}. 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.

Shelton, Joseph W., E-mail: jwshelt@emory.edu [Department of Radiation Oncology, Winship Cancer Institute, Emory University, Atlanta, Georgia (United States); Waxweiler, Timothy V.; Landry, Jerome; Gao, Huiying; Xu, Yanbo; Wang, Lanfang [Department of Radiation Oncology, Winship Cancer Institute, Emory University, Atlanta, Georgia (United States); El-Rayes, Bassel [Department of Hematology and Oncology, Winship Cancer Institute, Emory University, Atlanta, Georgia (United States); Shu, Hui-Kuo G. [Department of Radiation Oncology, Winship Cancer Institute, Emory University, Atlanta, Georgia (United States)

2013-07-01

244

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

245

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.

246

Determination of total antioxidant capacity of milk by CUPRAC and ABTS methods with separate characterisation of milk protein fractions.  

Science.gov (United States)

Most milk-applied antioxidant assays in literature are based on the isolation and quantification of individual antioxidative compounds, whereas total antioxidant capacity (TAC) gives a more holistic picture due to cooperative action of antioxidants. Recently, the cupric reducing antioxidant capacity (CUPRAC) method has been modified to measure the antioxidant capacities of thiol-containing proteins, where the classical ammonium acetate buffer - that may otherwise precipitate proteins- was replaced with concentrated urea buffer (able to expose embedded thiol groups of proteins to oxidative attack) adjusted to pH 7.0. Thus, antioxidant capacity of milk was investigated with two competing TAC assays, namely CUPRAC and ABTS (2,2'-azinobis(3-ethylbenzothiazoline-6-sulphonic acid))/persulphate, because only these assays were capable of evaluating protein contribution to the observed TAC value. As milk fat caused turbidity, experiments were carried out with skim milk or defatted milk samples. To determine TAC, modified CUPRAC method was applied to whole milk, separated and redissolved protein fractions, and the remaining liquid phase after necessary operations. Both TAC methods were investigated for their dilution sensitivity and antioxidant power assessment of separate milk fractions such as casein and whey. Proteins like ?-lactoglobulin and casein (but not simple thiols) exhibited enhanced CUPRAC reactivity with surfactant (SDS) addition. Addition of milk protein fractions to whole skim milk produced significant 'negative-biased' deviations (up to -26% relative standard error) from TAC absorbance additivity in the application of the ABTS method, as opposed to that of the CUPRAC method less affected by chemical deviations from Beer's law thereby producing much smaller deviations from additivity (i.e. the property of additivity is valid when the measured TAC of a mixture is equal to the sum of individual antioxidant capacities of its constituents). PMID:25731579

Çekiç, Sema Demirci; Demir, Asl?; Sözgen Ba?kan, Kevser; Tütem, Esma; Apak, Re?at

2015-05-01

247

Inhibition of radical reactions for an improved potassium tert-butoxide-promoted (11) C-methylation strategy for the synthesis of ?-(11) C-methyl amino acids.  

Science.gov (United States)

?-(11) C-Methyl amino acids are useful tools for biological imaging studies. However, a robust procedure for the labeling of amino acids has not yet been established. In this study, the (11) C-methylation of Schiff-base-activated ?-amino acid derivatives has been optimized for the radiosynthesis of various ?-(11) C-methyl amino acids. The benzophenone imine analog of methyl 2-amino butyrate was (11) C-methylated with [(11) C]methyl iodide following its initial deprotonation with potassium tert-butoxide (KOtBu). The use of an alternative base such as tetrabutylammonium fluoride, triethylamine, and 1,8-diazabicyclo[5.4.0]undec-7-ene did not result in the (11) C-methylated product. Furthermore, the KOtBu-promoted (11) C-methylation of the Schiff-base-activated amino acid analog was enhanced by the addition of 1,2,4,5-tetramethoxybenzene or 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and inhibited by the addition of 1,10-phenanthroline. These results suggest that inhibition of radical generation induced by KOtBu improves the ?-(11) C-methylation of the Schiff-base-activated amino acids. The addition of a mixture of KOtBu and TEMPO to a solution of Schiff-base-activated amino acid ester and [(11) C]methyl iodide provided optimal results, and the tert-butyl ester and benzophenone imine groups could be readily hydrolyzed to give the desired ?-(11) C-methyl amino acids with a high radiochemical conversion. This strategy could be readily applied to the synthesis of other ?-(11) C-methyl amino acids. PMID:25690316

Suzuki, Chie; Kato, Koichi; Tsuji, Atsushi B; Zhang, Ming-Rong; Arano, Yasushi; Saga, Tsuneo

2015-03-01

248

Negative-ion photoelectron spectroscopy, gas-phase acidity, and thermochemistry of the peroxyl radicals CH(3)OO and CH(3)CH(2)OO.  

Science.gov (United States)

Methyl, methyl-d(3), and ethyl hydroperoxide anions (CH(3)OO(-), CD(3)OO(-), and CH(3)CH(2)OO(-)) have been prepared by deprotonation of their respective hydroperoxides in a stream of helium buffer gas. Photodetachment with 364 nm (3.408 eV) radiation was used to measure the adiabatic electron affinities: EA[CH(3)OO, X(2)A' '] = 1.161 +/- 0.005 eV, EA[CD(3)OO, X(2)A' '] = 1.154 +/- 0.004 eV, and EA[CH(3)CH(2)OO, X(2)A' '] = 1.186 +/- 0.004 eV. The photoelectron spectra yield values for the term energies: Delta E(X(2)A' '-A (2)A')[CH(3)OO] = 0.914 +/- 0.005 eV, Delta E(X(2)A' '-A (2)A')[CD(3)OO] = 0.913 +/- 0.004 eV, and Delta E(X(2)A' '-A (2)A')[CH(3)CH(2)OO] = 0.938 +/- 0.004 eV. A localized RO-O stretching mode was observed near 1100 cm(-1) for the ground state of all three radicals, and low-frequency R-O-O bending modes are also reported. Proton-transfer kinetics of the hydroperoxides have been measured in a tandem flowing afterglow-selected ion flow tube (FA-SIFT) to determine the gas-phase acidity of the parent hydroperoxides: Delta(acid)G(298)(CH(3)OOH) = 367.6 +/- 0.7 kcal mol(-1), Delta(acid)G(298)(CD(3)OOH) = 367.9 +/- 0.9 kcal mol(-1), and Delta(acid)G(298)(CH(3)CH(2)OOH) = 363.9 +/- 2.0 kcal mol(-1). From these acidities we have derived the enthalpies of deprotonation: Delta(acid)H(298)(CH(3)OOH) = 374.6 +/- 1.0 kcal mol(-1), Delta(acid)H(298)(CD(3)OOH) = 374.9 +/- 1.1 kcal mol(-1), and Delta(acid)H(298)(CH(3)CH(2)OOH) = 371.0 +/- 2.2 kcal mol(-1). Use of the negative-ion acidity/EA cycle provides the ROO-H bond enthalpies: DH(298)(CH(3)OO-H) = 87.8 +/- 1.0 kcal mol(-1), DH(298)(CD(3)OO-H) = 87.9 +/- 1.1 kcal mol(-1), and DH(298)(CH(3)CH(2)OO-H) = 84.8 +/- 2.2 kcal mol(-1). We review the thermochemistry of the peroxyl radicals, CH(3)OO and CH(3)CH(2)OO. Using experimental bond enthalpies, DH(298)(ROO-H), and CBS/APNO ab initio electronic structure calculations for the energies of the corresponding hydroperoxides, we derive the heats of formation of the peroxyl radicals. The "electron affinity/acidity/CBS" cycle yields Delta(f)H(298)[CH(3)OO] = 4.8 +/- 1.2 kcal mol(-1) and Delta(f)H(298)[CH(3)CH(2)OO] = -6.8 +/- 2.3 kcal mol(-1). PMID:11572679

Blanksby, S J; Ramond, T M; Davico, G E; Nimlos, M R; Kato, S; Bierbaum, V M; Lineberger, W C; Ellison, G B; Okumura, M

2001-10-01

249

Influence of brewing method and acidity regulators on the antioxidant capacity of coffee brews.  

Science.gov (United States)

The antioxidant capacity of coffee brews prepared with different coffeemakers (filter, plunger, mocha, and espresso) was measured by colorimetric (total phenolic compounds and ABTS) and electron spin resonance (ESR) spectroscopy techniques (Fremy's salt and TEMPO). The mocha coffeemaker had the highest yield in coffee antioxidant extraction per gram of ground roasted coffee, but espresso coffee was richest in terms of antioxidant intake (per milliliter of coffee brew) followed by mocha, plunger, and filter. Both Folin-Ciocalteu (total phenolic compounds) and ABTS assays reacted with standard solutions of chlorogenic acids (CGA) and melanoidins (MO-Ala and MO-Gly). However, Fremy's salt was mainly scavenged by chlorogenic acids, whereas the stabilized radical TEMPO was effectively scavenged by melanoidins, but not by chlorogenic acids. Thus, ESR spectroscopy allows distinguishing between phenolic and nonphenolic antioxidants. Moreover, the addition of pH-regulator agents to coffee, such as sodium carbonate (75 ppm) and bicarbonate (75 ppm), to extend its shelf life, slightly increases the pH, modifying the antioxidant capacity in those coffee brews with the highest capacity (mocha and espresso). PMID:20141144

Pérez-Martínez, Mónica; Caemmerer, Bettina; De Peña, M Paz; Cid, Concepción; Kroh, Lothar W

2010-03-10

250

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

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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

251

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

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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

252

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.)

253

Quantitative Determination of ABT-925 in Human Plasma by On-Line SPE and LC-MS/MS: Validation and Sample Analysis in Phase II Studies  

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Full Text Available A fully automated 96-well On-Line Solid Phase Extraction (SPE followed by High Performance Liquid Chromatography (HPLC-Tandem Mass Spectrometric (MS/MS method for the determination of ABT-925 (2-{3-[4-(2-tert-Butyl-6-trifluoromethyl-pyrimidin-4-yl-piperazin-1-yl-propyl-sulfanyl}-3H-pyrimidin-4-one fumarate in human plasma was developed, validated and utilized in Phase II clinical studies. 50 µL of plasma sample was fortified with internal standard (IS, d8-ABT-925 and extracted on-line with Cohesive Turbo Flow Cyclone P HTLC column. The chromatographic separation was performed on Aquasil C18 (3 ?m 50 × 3 mm HPLC column with a mobile phase consisting of 50/50/0.1 (v/v/v ACN/H2O/formic acid. The mass spectrometric measurement was conducted under positive ion mode using multiple reaction monitoring (MRM of m/z 457.4 ? 329.4 for analyte and m/z 465.5 ? 337.5 for IS.The peak area ratio (analyte/IS was used to quantitate ABT-925. A dynamic range of 0.0102 ?g/mL to 5.24 ?g/mL was established after the validation. The validated method was then used for two Phase II studies. To demonstrate the method reproducibility, approximately 10% of the incurred samples from one study were repeated in singlet. The repeated values were compared to the initial values. All repeated values agreed within ±15% of the mean values.

Katty Wan

2010-05-01

254

Acquired resistance to ABT-737 in lymphoma cells that up-regulate MCL-1 and BFL-1  

OpenAIRE

ABT-737 is a small-molecule antagonist of BCL-2 currently under evaluation in clinical trials in the oral form of ABT-263. We anticipate that acquired resistance to this promising drug will inevitably arise. To study potential mechanisms of resistance to ABT-737, we derived resistant lines from initially sensitive OCI-Ly1 and SU-DHL-4 lymphoma cell lines via long-term exposure. Resistance was based in the mitochondria and not due to an inability of the drug to bind BCL-2. Resistant cells had ...

Yecies, Derek; Carlson, Nicole E.; Deng, Jing; Letai, Anthony

2010-01-01

255

Endogenous dopamine enhances the neurotoxicity of 3-nitropropionic acid in the striatum through the increase of mitochondrial respiratory inhibition and free radicals production.  

Science.gov (United States)

3-Nitropropionic acid (3-NP), an inhibitor of the mitochondrial enzyme succinate dehydrogenase, induces neuronal degeneration in the striatum. It is known that dopamine (DA) enhances this toxic effect. In this work, we study how the increase of DA influences the toxic effect of 3-NP on DAergic terminals, GABAergic neurons, astroglia and microglia in the striatum. We increased the content of DA through the inhibition of its uptake by nomifensine or the inhibition of its catabolism by deprenyl. We found that although nomifensine and deprenyl enhanced the DA overflow produced by 3-NP perfusion, they protected against the damage induced by 3-NP in the DAergic terminals and the GABAergic neurons in the striatum. Moreover, there was a decrease of apoptotic cells, astrogliosis and activation of microglia as index of damage. We also found that depletion of DA by reserpine and alpha-methyl-p-tyrosine produced a significant reduction of the inhibition of the respiratory rate and of the production of superoxide radical induced by 3-NP in synaptosomes from the striatum. All these results suggest that endogenous dopamine within the dopaminergic terminals of the striatum enhances the mitochondrial production of radical oxygen species along with the respiratory inhibition produced by 3-NP and thus increases the toxicity produced by 3-NP in the striatum. PMID:18093658

Villarán, Ruth F; Tomás-Camardiel, M; de Pablos, Rocío M; Santiago, Marti; Herrera, Antonio J; Navarro, Ana; Machado, Alberto; Cano, Josefina

2008-03-01

256

A pulse radiolysis study of the reactions of OH radical/O-with linoleic acid in the oxygen-free aqueous solution  

International Nuclear Information System (INIS)

Absorption spectra of products resulting from the reaction of OH radical and O- with linoleate in an aqueous solution have been measured. An OH radical adduct, absorbing at approx. 240 nm, as well as the allyl and the dienyl radical, were observed. The dienyl radical is formed by the reaction of linoleate with OH radical and O- radicals. The greater selectivity for the formation of dienyl radicals by O- as compared to OH radical is due to the formation of an OH radical adduct. The dependence of the absorption band of the adduct on linoleate concentration can be explained in terms of competition between reactions of OH radical with linoleate molecules in micelles and in solution. It is assumed that OH radicals neither form adducts nor dienyl radicals with micellized linoleate, but still react with these molecules, albeit in a different way. Since the rate constant for the reaction of OH radical with micellized linoleate is comparable to the rate constant for the OH radical addition reaction and much lower than the rate constant for dienyl production, the absorbance at 280 nm (dienyl) is less affected by the linoleate concentration increase than the absorbance at approx. 240 nm (OH adduct). (author)

257

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

258

Growth of ABT-5 bacteria culture in whey supplemented with whey protein concentrate  

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Full Text Available The objective of this research was to decrease the duration of whey fermentation and to analyze the impact of whey protein concentrates (WPC addition on growth and activity as well as on survival of mixed ABT-5 culture bacteria (Lactobacillus acidophilus, Bifidobacterium spp. and Streptococcus thermophilus during 28 days of fermented whey cold storage (5 °C. Whey fermentation was observed at 37 °C with and without 1.5 and 3 % WPC addition. Whey fermentation with mixed ABT-5 bacterial culture took about 6.5 hours, and WPC did not affect the fermentation dynamics, regardless of the added amount. The viable cell count of Lactobacillus acidophilus was higher in fermented whey with WPC (about 7.13 log CFU/mL compared to whey without WPC (about 6.63 log CFU/mL. WPC addition did not affect the growth of bacteria Bifidobacterium spp. and Streptococcus thermophilus nor the survival of ABT-5 culture bacteria in fermented whey during 28 days of cold storage (5 °C.

Bojan Matijevi?

2010-09-01

259

Thiyl radicals, reaction kinetics and redox chemistry  

OpenAIRE

In focusing on the free radical chemistry of thiyl radicals,two importantclasses are dealt with, namely, the amino acidalkylthiyl and the acylthiyl radicals, where pulse radiolysisand steady state ?-radiolysis are applied. Amino acid thiyl radicals (RS•), are important in manybiological systems,as intermediates in the repair reactions ofthiols towards targeted carbon-centeredradicals and ascatalytic centers in many enzymatic reactions. Initially,thereactions following one-electron oxidatio...

Zhao, Rong

1998-01-01

260

Decarboxylation by SO4- radicals  

International Nuclear Information System (INIS)

Decarboxylation by the reaction of SO4- radical with aliphatic and aromatic carboxylic acids has been examined. Most aliphatic acids undergo efficient decarboxylation by SO4- whereas their reactions with hydroxyl radical result in little decarboxylation. Aromatic acids decarboxylate to varying degrees depending on the other substituents. For example, benzoic and the phthalic acids undergo efficient decarboxylation, while o-toluic, p-hydroxybenzoic, and p-methoxybenzoic acid show only a small degree of decarboxylation. The findings support the conclusion that SO4- reacts by electron transfer oxidation while OH either adds or abstracts H. Decarboxylation by H2PO4 radicals was also examined in a few cases and found to be less efficient than that by SO4-

261

ABT-724 alleviated hyperactivity and spatial learning impairment in the spontaneously hypertensive rat model of attention-deficit/hyperactivity disorder.  

Science.gov (United States)

Dysfunction of dopamine D4 receptor (D4R) is linked to attention-deficit/hyperactivity disorder (ADHD) as well as ADHD associated cognitive impairment. Here, we tested the possible therapeutic benefit of the D4R-selective agonist ABT-724 in adolescent spontaneously hypertensive rats (SHRs). ABT-724-treated SHRs were administered ABT-724 (0.04mg/kg, 0.16mg/kg or 0.64mg/kg) from postnatal day (P) 28 to P32. Control SHRs and Sprague-Dawley (SD) rats were injected with saline. Then two cohorts of rats were tested in the open field and Làt maze that measured locomotion and non-selective attention (NSA), respectively. Another cohort of rats was subjected to water maze task for evaluation of spatial learning and memory. We found that control SHRs displayed hyperactivity as well as impaired NSA and spatial learning compared with normotensive SD rats. ABT-724 (0.16 and 0.64mg/kg) treatment alleviated hyperactivity and spatial learning impairment in SHRs. No dose of ABT-724 tested altered NSA in SHRs. Our results raise the possibility that ABT-724 may be used as a therapeutic intervention for ADHD patients during adolescence. PMID:25128216

Yin, Ping; Cao, Ai-Hua; Yu, Lin; Guo, Liang-Jing; Sun, Ruo-Peng; Lei, Ge-Fei

2014-09-19

262

ABT-263, a Bcl-2 inhibitor, enhances the susceptibility of lung adenocarcinoma cells treated with Src inhibitors to anoikis.  

Science.gov (United States)

The tyrosine kinase Src plays an important role in the development of anoikis resistance in lung adenocarcinomas. Several suspension lung adenocarcinoma cell lines, which express phosphorylated Src, undergo apoptosis, or anoikis, in the presence of Src kinase inhibitors. However, lung adenocarcinoma cell lines vary in their sensitivity to Src inhibitors. We hypothesized that the addition of ABT-263, a potent Bcl-2 inhibitor, should significantly enhance the degree of anoikis in lung adenocarcinoma cells treated with Src inhibitors. In this study, we treated four suspension lung adenocarcinoma cell lines with ABT-263, an Src inhibitor (bosutinib or PP1), or a combination of both. In LC-KJ and HCC827 cells, combined treatment with ABT-263 and an Src inhibitor effectively induced anoikis, and the extent of anoikis was significantly greater than that induced by each agent alone; the synergy between the two drugs was apparent. Although we did not observe a marked increase in anoikis in LC-KJ and HCC827 cells treated with ABT-263 alone, H1650 and H1975 cells treated with ABT-263 (1 ?M) upon detachment significantly underwent apoptosis, the levels of which were much greater than those observed upon attachment. However, the levels of anoikis induced by combination treatment were still greater than those by the individual agents in H1650 and H1975 cells. These findings provide a biological rationale to test combination therapy with ABT-263 and Src inhibitors in patients with lung adenocarcinoma. PMID:21206976

Sakuma, Yuji; Tsunezumi, Jun; Nakamura, Yoshiyasu; Yoshihara, Mitsuyo; Matsukuma, Shoichi; Koizume, Shiro; Miyagi, Yohei

2011-03-01

263

Comparative study of antioxidant properties and total phenolic content of 30 plant extracts of industrial interest using DPPH, ABTS, FRAP, SOD, and ORAC assays.  

Science.gov (United States)

Aqueous extracts of 30 plants were investigated for their antioxidant properties using DPPH and ABTS radical scavenging capacity assay, oxygen radical absorbance capacity (ORAC) assay, superoxide dismutase (SOD) assay, and ferric reducing antioxidant potential (FRAP) assay. Total phenolic content was also determined by the Folin-Ciocalteu method. Antioxidant properties and total phenolic content differed significantly among selected plants. It was found that oak (Quercus robur), pine (Pinus maritima), and cinnamon (Cinnamomum zeylanicum) aqueous extracts possessed the highest antioxidant capacities in most of the methods used, and thus could be potential rich sources of natural antioxidants. These extracts presented the highest phenolic content (300-400 mg GAE/g). Mate (Ilex paraguariensis) and clove (Eugenia caryophyllus clovis) aqueous extracts also showed strong antioxidant properties and a high phenolic content (about 200 mg GAE/g). A significant relationship between antioxidant capacity and total phenolic content was found, indicating that phenolic compounds are the major contributors to the antioxidant properties of these plants. PMID:19199445

Dudonné, Stéphanie; Vitrac, Xavier; Coutière, Philippe; Woillez, Marion; Mérillon, Jean-Michel

2009-03-11

264

Phenolic acid content and radical scavenging activity of extracts from medlar (Mespilus germanica L.) fruit at different stages of ripening.  

Czech Academy of Sciences Publication Activity Database

Ro?. 124, ?. 1 (2011), s. 271-277. ISSN 0308-8146 R&D Projects: GA AV ?R KAN200380801 Institutional research plan: CEZ:AV0Z50380511 Keywords : Phenolic acids * HPLC * Mass spectrometry * Fruit * Ripening Subject RIV: EF - Botanics Impact factor: 3.655, year: 2011

Grúz, Ji?í; Ayaz, F. A.; Torun, H.; Strnad, Miroslav

2011-01-01

265

ANTIOXIDANT CAPACITY AND AMINO ACID PROFILES OF EGG TOFU  

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Full Text Available Tofu contains high quality protein source and antioxidant which could reduce risk of cancer. This research aims to determine the effect of soymilk and egg ratios on the antioxidant capacity, daidzein and genistein content and amino acid profiles of egg tofu. Egg tofu was prepared using soymilk and fresh egg in ratios of 1:1, 2:1, 3:1 and 4:1. Glucono-Delta-Lactone (GDL was added in the egg tofu to act as a coagulating agent. Increased of soymilk at all ratios had significantly (p<0.05 increased in Ferric-Reducing Antioxidant Power (FRAP, daidzein and genistein content of egg tofu. Conversely, decreased in soymilk ratio had significantly (p<0.05 increased the radical scavenging activities of the 2,2-Azino-Bis 3-ethylbenzothiazoline-6-Sulfonic acid (ABTS and 2,2-Diphenyl-2-Picrylhydrazyl (DPPH in egg tofu. Increased of soymilk ratio up to 3:1 caused decreased in amino acid methionine (met and cystein (cys significantly (p<0.05. A significant (p<0.01 and a positive correlation was observed between Total Phenolic Content (TPC and FRAP (r = 0.93. However, there was a negative (p<0.01 correlation between TPC and DPPH (r = -0.83. The antioxidant capacity of egg tofu in DPPH assay showed a positive and significant (p<0.01 correlation with cysteine, methionine and tryptophan with r value of 0.92, 0.93 and 0.96 respectively. Higher content of egg in egg tofu had contributed to the increased of antioxidant capacity as indicated in DPPH assay and ABTS assay as well as amino acid methionine and cysteine.

Maizura Murad

2013-01-01

266

Development of a hydroxyl radical nanoprobe  

Science.gov (United States)

A hydroxyl radical nanoprobe has been developed by covalently attaching the dye, coumarin-3-carboxylic acid (CCA), to amine-functionalized polyacrylic acid (AFPAA) nanoparticles. These nanoparticles are referred to as PEBBLEs (Probes Encapsulated By Biologically Localized Embedding). This probe has been shown to be highly specific and sensitive. The formation of hydroxyl radical is monitored by an increase in fluorescence over time.

King, Matthew; Kopelman, Raoul

2002-06-01

267

Changes in optical density, amino acid composition, and fluorescence of papain inactivated by hydroxyl radicals and hydrogen peroxide  

International Nuclear Information System (INIS)

Chromatography of irradiated papain on an affinity column with the Gly-Gly-Tyr(Bzl)-Arg inhibitor peptide gave rise to three clearly resolved peaks. The first one was relatively small and contained completely inactive nonreparable enzyme, which appeared to have suffered a massive conformational change or loss of several binding sites. The second contained the inactive sulfenic acid derivative, which can be reactivated with cysteine. The third peak was composed of nonrepairable enzyme as well as some repairable enzyme and some fully active papain. Changes in absorbance and amino acid analysis established a significant loss of tyrosine residues, while tryptophan destruction appeared to be insignificant up to 10 krad. Fluorescence measurements indicated changes in the active-site region, which are probably largely due to the inactivating modification of the Cys-25 sulfhydryl group, for which evidence has already been reported

268

Radicals in ?-irradiated wool  

International Nuclear Information System (INIS)

Radicals were identified in wool fiber ?-irradiated at 77 K by EPR: products of reaction of an electron e and H atom with amino acid residues and a polypeptide chain, and their partial yields at 77 K and the reactivity scale of e with respect to the individual fragments of the protein molecule were determined: [RSSR]: [>C=Op.b.]:[NH3+-R]:[aromatic ring] = 4:3: > 1:1. 10 refs., 1 fig., 1 tab

269

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)

270

Some reactions of oxidizing radicals with enzymes in aqueous solution  

International Nuclear Information System (INIS)

A range of oxidizing radicals including some inorganic radical anions and the superoxide radical, can be generated by radiolysis of aqueous solutions. These radicals are more selective in their reactions with amino acids than the hydroxyl radical. Factors controlling the apparent reactivity of radical anions with proteins, such as free radical equilibria and ion-binding, are described. The superoxide radical inactivates papain by reaction with the cysteine residue. This reaction has been studied in solutions subjected to radiations of varying linear energy transfer. (Auth.)

271

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

272

Radical chemistry of iron carbonyls  

International Nuclear Information System (INIS)

It is shown that catalytic carbonylation of various compounds using iron carbonyl complexes is based on two types of reactions [redox disproportionation of iron carbonyl induced by Lewis bases and oxidative addition of Broensted and Lewis acids to (hydrido)carbonylferrate anions] comprising single-electron initiation steps and subsequent radical chain reactions. The role of iron carbonyl radical anions as catalysts for carbonylation processes with controlled reduction potential of the medium is noted. Characteristic features of the radical chemistry of iron and other transition metal carbonyls is analysed.

273

Activities of ABT-773 against Listeria monocytogenes and coryneform bacteria of clinical interest.  

Science.gov (United States)

The in vitro activities of ABT-773 were evaluated against 15 Listeria monocytogenes strains and 196 coryneform bacteria isolated from clinical samples. One hundred percent of the L. monocytogenes strains were inhibited by isolates tested were inhibited (MIC(50)s) and MIC(90)s for other organisms were 0.125 and 0.5 (Corynebacterium amycolatum), 1 and >32 (Corynebacterium jeikeium), 0.03 and >32 (Corynebacterium minutissimum), >32 and >32 (Corynebacterium pseudodiphtheriticum and Corynebacterium urealyticum), 0.125 and >32 (Corynebacterium striatum), and 0.03 and 0.5 (Rhodococcus equi), respectively. PMID:12654678

Conejo, María del Carmen; Martínez-Martínez, Luis; Pascual, Alvaro; Suárez, Ana Isabel; Perea, Evelio J

2003-04-01

274

Activation of dopamine D4 receptors by ABT-724 induces penile erection in rats  

OpenAIRE

Apomorphine, a nonselective dopamine receptor agonist, facilitates penile erection and is effective in patients suffering from erectile dysfunction. The specific dopamine receptor subtype(s) responsible for its erectogenic effect is not known. Here we report that the dopamine D4 receptor plays a role in the regulation of penile function. ABT-724 is a selective dopamine D4 receptor agonist that activates human dopamine D4 receptors with an EC50 of 12.4 nM and 61% efficacy, with no effect on do...

Brioni, Jorge D.; Moreland, Robert B.; Cowart, Marlon; Hsieh, Gin C.; Stewart, Andrew O.; Hedlund, Petter; Donnelly-roberts, Diana L.; Nakane, Masaki; Lynch, James J.; Kolasa, Teodozyi; Polakowski, James S.; Osinski, Mark A.; Marsh, Kennan; Andersson, Karl-erik; Sullivan, James P.

2004-01-01

275

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

276

?-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

277

A novel poly(ADP-ribose) polymerase inhibitor, ABT-888, radiosensitizes malignant human cell lines under hypoxia  

International Nuclear Information System (INIS)

The chemo- and radioresponse of tumor cells can be determined by genetic factors (e.g., those that modify cell cycle arrest, DNA damage repair or cell death) and microenvironmental factors, such as hypoxia. Poly(ADP-ribose) polymerase (PARP) is a nuclear enzyme that rapidly recognizes and binds to DNA breaks to facilitate DNA strand break repair. Pre-clinical data suggest that PARP inhibitors (PARPi) may potentiate the effects of radiotherapy and chemotherapy. However, it is unclear as to whether PARPi are effective against hypoxic cells. We therefore tested the role for a novel PARPi, ABT-888, as a radiosensitizing agent under hypoxic conditions. Using human prostate (DU-145, 22RV1) and non-small cell lung (H1299) cancer cell lines, we observed that ABT-888 inhibited both recombinant PARP activity and intracellular PARP activity (86% to 92% decrease in all 3 cells lines following 2.5 ?M treatment). ABT-888 was toxic to both oxic and hypoxic cells. When ABT-888 was combined with ionizing radiation (IR), clonogenic radiation survival was decreased by 40-50% under oxic conditions. Under acute hypoxia, ABT-888 radiosensitized malignant cells to a level similar to oxic radiosensitivity. To our knowledge, this is the first study to demonstrate that inhibition of PARP activity can sensitize hypoxic cancer cells and the combination of IR-PARPi has the potential to improve the therapeutic ratio of radiotherapy

278

Role of p38 MAPK in enhanced human cancer cells killing by the combination of aspirin and ABT-737.  

Science.gov (United States)

Regular use of aspirin after diagnosis is associated with longer survival among patients with mutated-PIK3CA colorectal cancer, but not among patients with wild-type PIK3CA cancer. In this study, we showed that clinically achievable concentrations of aspirin and ABT-737 in combination could induce a synergistic growth arrest in several human PIK3CA wild-type cancer cells. In addition, our results also demonstrated that long-term combination treatment with aspirin and ABT-737 could synergistically induce apoptosis both in A549 and H1299 cells. In the meanwhile, short-term aspirin plus ABT-737 combination treatment induced a greater autophagic response than did either drug alone and the combination-induced autophagy switched from a cytoprotective signal to a death-promoting signal. Furthermore, we showed that p38 acted as a switch between two different types of cell death (autophagy and apoptosis) induced by aspirin plus ABT-737. Moreover, the increased anti-cancer efficacy of aspirin combined with ABT-737 was further validated in a human lung cancer A549 xenograft model. We hope that this synergy may contribute to failure of aspirin cancer therapy and ultimately lead to efficacious regimens for cancer therapy. PMID:25388762

Zhang, Chong; Shi, Jing; Mao, Shi-ying; Xu, Ya-si; Zhang, Dan; Feng, Lin-yi; Zhang, Bo; Yan, You-you; Wang, Si-cong; Pan, Jian-ping; Yang, You-ping; Lin, Neng-ming

2015-02-01

279

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

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Full Text Available AbstractPoly(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

2008-01-01

280

E.s.r. study of spin-trapped radicals formed during the photolysis of aqueous solutions of acid amides and H2O2  

International Nuclear Information System (INIS)

Free radicals formed by the reactions of OH radicals with amides and their N-methylated derivatives in aqueous solutions have been studied. The OH radicals were produced by U.V.-photolysis of H2O2, and the short-lived amide radicals were converted to more stable nitroxide radicals by addition to a spin-trap, tert-nitrosobutane. The spin-trapped radicals were identified by e.s.r spectroscopy. For acetamide, chloracetamide, malonamide, succinamide and proprionamide, the observed radicals were formed by H-abstraction from the carbon atoms attached to the carbonyl group. The H atom attached to the carbonyl group was abstracted in formamide. For N-methyl acetamide, N,N-dimethyl acetamide and the corresponding formamide derivatives, H-abstraction occurred only from the N-methyl group. The non-equivalency of the amide protons was observed in the spin-trapped radicals for acetamide, formamide, malonamide, succinamide and proprionamide. The identification of the site of OH attack on N-methyl amides is helpful for the study of radical formation in peptides and proteins. (author)

281

Enzyme-bound pentadienyl and peroxyl radicals in purple lipoxygenase  

International Nuclear Information System (INIS)

Samples of purple lipoxygenase prepared by addition of either 13-hydroperoxy-9,11-octadecadienoic acid or linoleic acid and oxygen to ferric lipoxygenase contain pentadienyl and/or peroxyl radicals. The radicals are identified by the g values and hyperfine splitting parameters of natural abundance and isotopically enriched samples. The line shapes of their EPR spectra suggest the radicals are conformationally constrained when compared to spectra of the same radicals generated in frozen linoleic acid. Further, the EPR spectra are unusually difficult to saturate. All of this implies that these species are bound to the enzyme, possibly in proximity to the iron. Addition of natural abundance hydroperoxide under 17O-enriched O2 leads to the 17O-enriched peroxyl radical, while the opposite labeling results in the natural abundance peroxyl radical, demonstrating the exchange of oxygen. Both radicals are detected in samples of purple lipoxygenase prepared with either linoleic acid or hydroperoxide under air. Addition of the hydroperoxide in the absence of oxygen favors the pentadienyl radical. The authors propose that addition of either linoleic acid or hydroperoxide to ferric lipoxygenase leads to multiple mechanistically connected enzyme complexes, including those with (hydro)peroxide, peroxide, peroxyl radical, pentadienyl radical, and linoleic acid bound. This hypothesis is essentially identical with the proposed radical mechanism of oxygeth the proposed radical mechanism of oxygenation of polyunsaturated fatty acids by lipoxygenase

282

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

283

[Demonstration of bacteria and fungi in tissues by topo-optic aldehyde bisulfite toluidine blue (ABT) reaction].  

Science.gov (United States)

Reaction with aldehyd-bisulfit-toluidinblue (ABT)--as a selective topo-optical reaction for vicinal OH-and amino-OH groups, appears to be suitable for demonstration of bacteria in tissues. Cell membranes and capsules of bacteria and fungi contain large quantity of carbo-hydrates, therefore they show strong basophilic staining after ABT reaction. Double refringement brought about by orientated dye-binding seems to be the sign of the linear arrangement of polysaccharides composing cell membranes and capsules of bacteria. Practical importance of the reaction is shown on examples. Diagnostic advantages of it are also discussed. PMID:1264102

Fischer, J; Romhányi, G

1976-04-01

284

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

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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

285

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)

286

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

287

Radical America  

Science.gov (United States)

The journal Radical American began in 1967 and was started by the Alternative Education Project in Somerville, Massachusetts. Over their history, they have published a number of issues on a number of compelling topics, ranging from community development to feminism. As part of their Digital Initiatives Project, Brown University has digitized the first fourteen year print run of the journal up to the year 1980. Visitors here can browse the contents of the journal by author or by title. Some of these titles include pieces on American Leninism, Europe's migrant workers, and the "urban crisis" of the 1970s. Visitors can also browse the digitized volumes by clicking on an interactive page that contains the covers of the available issues. Overall, this is a fine resource for social historians and members of the public with a penchant for exploring some of the overlooked facets of contemporary American history.

288

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

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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

289

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

290

Assessment of ABT-263 activity across a cancer cell line collection leads to a potent combination therapy for small-cell lung cancer.  

Science.gov (United States)

BH3 mimetics such as ABT-263 induce apoptosis in a subset of cancer models. However, these drugs have shown limited clinical efficacy as single agents in small-cell lung cancer (SCLC) and other solid tumor malignancies, and rational combination strategies remain underexplored. To develop a novel therapeutic approach, we examined the efficacy of ABT-263 across >500 cancer cell lines, including 311 for which we had matched expression data for select genes. We found that high expression of the proapoptotic gene Bcl2-interacting mediator of cell death (BIM) predicts sensitivity to ABT-263. In particular, SCLC cell lines possessed greater BIM transcript levels than most other solid tumors and are among the most sensitive to ABT-263. However, a subset of relatively resistant SCLC cell lines has concomitant high expression of the antiapoptotic myeloid cell leukemia 1 (MCL-1). Whereas ABT-263 released BIM from complexes with BCL-2 and BCL-XL, high expression of MCL-1 sequestered BIM released from BCL-2 and BCL-XL, thereby abrogating apoptosis. We found that SCLCs were sensitized to ABT-263 via TORC1/2 inhibition, which led to reduced MCL-1 protein levels, thereby facilitating BIM-mediated apoptosis. AZD8055 and ABT-263 together induced marked apoptosis in vitro, as well as tumor regressions in multiple SCLC xenograft models. In a Tp53; Rb1 deletion genetically engineered mouse model of SCLC, the combination of ABT-263 and AZD8055 significantly repressed tumor growth and induced tumor regressions compared with either drug alone. Furthermore, in a SCLC patient-derived xenograft model that was resistant to ABT-263 alone, the addition of AZD8055 induced potent tumor regression. Therefore, addition of a TORC1/2 inhibitor offers a therapeutic strategy to markedly improve ABT-263 activity in SCLC. PMID:25737542

Faber, Anthony C; Farago, Anna F; Costa, Carlotta; Dastur, Anahita; Gomez-Caraballo, Maria; Robbins, Rebecca; Wagner, Bethany L; Rideout, William M; Jakubik, Charles T; Ham, Jungoh; Edelman, Elena J; Ebi, Hiromichi; Yeo, Alan T; Hata, Aaron N; Song, Youngchul; Patel, Neha U; March, Ryan J; Tam, Ah Ting; Milano, Randy J; Boisvert, Jessica L; Hicks, Mark A; Elmiligy, Sarah; Malstrom, Scott E; Rivera, Miguel N; Harada, Hisashi; Windle, Brad E; Ramaswamy, Sridhar; Benes, Cyril H; Jacks, Tyler; Engelman, Jeffrey A

2015-03-17

291

Reactivity and selectivity patterns in hydrogen atom transfer from amino Acid C-h bonds to the cumyloxyl radical: polar effects as a rationale for the preferential reaction at proline residues.  

Science.gov (United States)

Absolute rate constants for hydrogen atom transfer (HAT) from the C-H bonds of N-Boc-protected amino acids to the cumyloxyl radical (CumO(•)) were measured by laser flash photolysis. With glycine, alanine, valine, norvaline, and tert-leucine, HAT occurs from the ?-C-H bonds, and the stability of the ?-carbon radical product plays a negligible role. With leucine, HAT from the ?- and ?-C-H bonds was observed. The higher kH value measured for proline was explained in terms of polar effects, with HAT that predominantly occurs from the ?-C-H bonds, providing a rationale for the previous observation that proline residues represent favored HAT sites in the reactions of peptides and proteins with (•)OH. Preferential HAT from proline was also observed in the reactions of CumO(•) with the dipeptides N-BocProGlyOH and N-BocGlyGlyOH. The rate constants measured for CumO(•) were compared with the relative rates obtained previously for the corresponding reactions of different hydrogen-abstracting species. The behavior of CumO(•) falls between those observed for the highly reactive radicals Cl(•) and (•)OH and the significantly more stable Br(•). Taken together, these results provide a general framework for the description of the factors that govern reactivity and selectivity patterns in HAT reactions from amino acid C-H bonds. PMID:25774567

Salamone, Michela; Basili, Federica; Bietti, Massimo

2015-04-01

292

Ferulic acid in combination with PARP inhibitor sensitizes breast cancer cells as chemotherapeutic strategy.  

Science.gov (United States)

Homologous-recombination (HR)-dependent repair defective cells are hypersensitive to poly (ADP-ribose) polymerase (PARP) inhibitors. Combinations of defective HR pathway and PARP inhibitors have been an effective chemotherapeutic modality. We previously showed that knockdown of the WD40-repeat containing protein, Uaf1, causes an HR repair defect in mouse embryo fibroblast cells and therefore, increases sensitivity to PARP inhibitor, ABT-888. Similarly, here, we show that ferulic acid reduces HR repair, inhibits RAD 51 foci formation, and accumulates ?-H2AX in breast cancer cells. Moreover, ferulic acid, when combined with ABT-888, renders breast cancer cells become hypersensitive to ABT-888. Our study indicates that ferulic acid in combination with ABT-888 treatment may serve as an effective combination chemotherapeutic agent as a natural bioactive compound. PMID:25677620

Choi, Young Eun; Park, Eunmi

2015-03-13

293

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

294

Free Radical Scavenging Activity of Mussaenda glabra  

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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

295

Ignorance Radicalized  

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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

296

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

297

Homogeneous and heterogeneous methods for laccase-mediated functionalization of chitosan by tannic acid and quercetin.  

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Homogeneous and heterogeneous methods for functionalization of chitosan with quercetin or tannic acid using laccase from Trametes versicolor is presented, yielding a bio-based product with synergistic antioxidant and antimicrobial properties. HPLC-SEC analysis and cyclic voltammetry kinetic studies showed that laccase catalyzes the oxidation of quercetin to electrophilic o-quinones, which undergo to an oligomer/polymer-forming structures. On the other hand, tannic acid was converted into gallic acid, its dimers, partially gallic acid esterified glucose and glucose, when exposed to laccases. ATR-FTIR spectroscopy provided evidence that quercetin o-quinones undergo coupling reactions with amino groups of chitosan via Schiff-base and Michael addition mechanisms under heterogeneous method, while oxidized tannic acid cross-linked with chitosan by hydrogen and electrostatic interactions under both methods. All polyphenols functionalized chitosans showed greatly improved ABTS(+) cation radicals scavenging capacity, compared with the untreated chitosan, while antimicrobial activities significantly depended on the mode of functionalization and type of microorganism. PMID:24750872

Boži?, Mojca; Gorgieva, Selestina; Kokol, Vanja

2012-07-01

298

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

299

Reaction of the hydrated electron with amino acids, peptides, and proteins in aqueous solution. II. Formation of radicals and electron transfer reactions  

International Nuclear Information System (INIS)

The steps in the reaction of the hydrated electron with several simple peptides have been studied. The initial step is an attachment of the e-/sub aq/ to a carbonyl group in the peptide chain. This reaction can be followed by a further intermolecular electron migration (depending on the nature of the peptide), resulting in a deaminated radical. Thus the reaction of e-/sub aq/ with peptides yields two types of radicals: the carbonyl electron adduct and the deaminated radical. The absorption spectra of radicals produced from peptides of alanine and glycine were recorded and examined with respect to their pH, ionic strength and peptide concentration dependence. In agreement with previous results, at all concentrations, (greater than 90 percent) is shown to be the deamination result of the reaction of e-/sub aq/ with dipeptide having a protonated terminal amino group. However, different results were obtained with higher peptides (tri, tetra, etc.). Here the percentage of deamination, at low peptide concentration, decreased with increasing the number of peptide bonds [approximately 60 percent for 10-3 M (gly)3]. This yield could be increased by increasing the peptide concentration [approximately 95 percent for 10-1 M (gly)3]. These findings led to the suggestion that aqueous solutions of peptides at neutral pH exists at least as dimers formed by hydrogen bonds. It was further suggested that these onds. It was further suggested that these bonds allow the migration of the electron between the carbonyl groups of the peptides, resulting in a higher yield of the deaminated radical. (U.S.)

300

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

301

Chronic lymphocytic leukemia requires BCL2 to sequester prodeath BIM, explaining sensitivity to BCL2 antagonist ABT-737  

OpenAIRE

Antiapoptotic B cell leukemia/lymphoma 2 (BCL2) family proteins are expressed in many cancers, but the circumstances under which these proteins are necessary for tumor maintenance are poorly understood. We exploited a novel functional assay that uses BCL2 homology domain 3 (BH3) peptides to predict dependence on antiapoptotic proteins, a strategy we call BH3 profiling. BH3 profiling accurately predicts sensitivity to BCL2 antagonist ABT-737 in primary chronic lymphocytic leukemia (CLL) cells....

Del Gaizo Moore, Victoria; Brown, Jennifer R.; Certo, Michael; Love, Tara M.; Novina, Carl D.; Letai, Anthony

2007-01-01

302

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

303

Endogenous antioxidants and radical scavengers.  

Science.gov (United States)

All living organisms are constantly exposed to oxidant agents deriving from both endogenous and exogenous sources capable to modify biomolecules and induce damages. Free radicals generated by oxidative stress exert an important role in the development of tissue damage and aging. Reactive species (RS) derived from oxygen (ROS) and nitrogen (RNS) pertain to free radicals family and are constituted by various forms of activated oxygen or nitrogen. RS are continuosly produced during normal physiological events but can be removed by antioxidant defence mechanism: the imbalance between RS and antioxidant defence mechanism leads to modifications in cellular membrane or intracellular molecules. In this chapter only endogenous antioxidant molecules will be critically discussed, such as Glutathione, Alpha-lipoic acid, Coenzyme Q, Ferritin, Uric acid, Bilirubin, Metallothioneine, L-carnitine and Melatonin. PMID:21520703

Rizzo, Angela Maria; Berselli, Patrizia; Zava, Stefania; Montorfano, Gigliola; Negroni, Manuela; Corsetto, Paola; Berra, Bruno

2010-01-01

304

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

305

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

306

Potent and selective small-molecule MCL-1 inhibitors demonstrate on-target cancer cell killing activity as single agents and in combination with ABT-263 (navitoclax).  

Science.gov (United States)

The anti-apoptotic protein MCL-1 is a key regulator of cancer cell survival and a known resistance factor for small-molecule BCL-2 family inhibitors such as ABT-263 (navitoclax), making it an attractive therapeutic target. However, directly inhibiting this target requires the disruption of high-affinity protein-protein interactions, and therefore designing small molecules potent enough to inhibit MCL-1 in cells has proven extremely challenging. Here, we describe a series of indole-2-carboxylic acids, exemplified by the compound A-1210477, that bind to MCL-1 selectively and with sufficient affinity to disrupt MCL-1-BIM complexes in living cells. A-1210477 induces the hallmarks of intrinsic apoptosis and demonstrates single agent killing of multiple myeloma and non-small cell lung cancer cell lines demonstrated to be MCL-1 dependent by BH3 profiling or siRNA rescue experiments. As predicted, A-1210477 synergizes with the BCL-2/BCL-XL inhibitor navitoclax to kill a variety of cancer cell lines. This work represents the first description of small-molecule MCL-1 inhibitors with sufficient potency to induce clear on-target cellular activity. It also demonstrates the utility of these molecules as chemical tools for dissecting the basic biology of MCL-1 and the promise of small-molecule MCL-1 inhibitors as potential therapeutics for the treatment of cancer. PMID:25590800

Leverson, J D; Zhang, H; Chen, J; Tahir, S K; Phillips, D C; Xue, J; Nimmer, P; Jin, S; Smith, M; Xiao, Y; Kovar, P; Tanaka, A; Bruncko, M; Sheppard, G S; Wang, L; Gierke, S; Kategaya, L; Anderson, D J; Wong, C; Eastham-Anderson, J; Ludlam, M J C; Sampath, D; Fairbrother, W J; Wertz, I; Rosenberg, S H; Tse, C; Elmore, S W; Souers, A J

2015-01-01

307

Contribution of cytochrome P450 and UDT-glucuronosyltransferase to the metabolism of drugs containing carboxylic acid groups: risk assessment of acylglucuronides using human hepatocytes.  

Science.gov (United States)

1.?In order to evaluate the inhibition activity of 1-aminobenzotriazole (ABT) and (-)-borneol (borneol) against cytochrome P450 (CYP) and UDP-glucuronosyltransferase (UGT), the substrates of these metabolic enzymes were incubated with ABT and borneol in human hepatocytes. We found that 3?mM ABT and 300??M borneol were the most suitable experimental levels to specifically inhibit CYP and UGT. 2.?Montelukast, mefenamic acid, flufenamic acid, diclofenac, tienilic acid, gemfibrozil, ibufenac and repaglinide were markedly metabolized in human hepatocytes, and the metabolism of gemfibrozil, mefenamic acid and flufenamic acid was inhibited by borneol. With regard to repaglinide, montelukast, diclofenac and tienilic acid, metabolism was inhibited by ABT. Ibufenac was partly inhibited by both inhibitors. Zomepirac, tolmetin, ibuprofen, indomethacin and levofloxacin were moderately metabolized by human hepatocytes, and the metabolism of zomepirac, ibuprofen and indomethacin was equally inhibited by both ABT and borneol. The metabolism of tolmetin was strongly inhibited by ABT, and was also inhibited weakly by borneol. Residual drugs, telmisartan, valsartan, furosemide, naproxen and probenecid were scarcely metabolized. 3.?Although we attempted to predict the toxicological risks of drugs containing carboxylic groups from the combination chemical stability and CLint via UGT, the results indicated that this combination was not sufficient and that clinical daily dose is important. PMID:24575896

Jinno, Norimasa; Tagashira, Mizuka; Tsurui, Kazuyuki; Yamada, Shizuo

2014-08-01

308

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.

Sanja Kostadinovic-Velickovska

2013-06-01

309

Sunlight and free radicals  

Science.gov (United States)

Thomas Tidwell reflects on the overlooked -- but prescient -- proposal by the British chemists Arthur Downes and Thomas Blunt for photochemical free-radical formation, decades before Moses Gomberg launched the field of radical chemistry by preparing triphenylmethyl, the first stable organic radical.

Tidwell, Thomas

2013-08-01

310

Lesson 28: Radical Equations  

Science.gov (United States)

The lesson begins with an emphasis on isolating the radical expression in a radical equation and then highlights the importance of checking for extraneous solutions that may be generated when the equation is solved by applying even powers. Equations containing two radical expressions and then presented, followed by coverage of taking the nth root of a^n.

2011-01-01

311

Weak radical classes  

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Full Text Available We introduce the concept of weak radical classes and proceed to construct these classes. In section 2 we define strongly austere semimodules. Theorem 1 characterizes strongly autere semimodules with respect to modular maximal subtractive ideals. We present an example of a weak radical class that can be neither a semiradical class nor a radical class. In section 4 we show that the semiradical class over a certain restricted class of semirings is equivalent to the weak radical class. We also demonstrate the construction of a semiradical class over this class. Finally, we show in example 3 that a semiradical class need not to be a radical class.

Huda Mohammed J. Al-Thani

2004-12-01

312

The Thrombospondin-1 Mimetic ABT-510 Increases the Uptake and Effectiveness of Cisplatin and Paclitaxel in a Mouse Model of Epithelial Ovarian Cancer  

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Full Text Available Epithelial ovarian cancer (EOC comprises approximately 90% of ovarian cancers and arises from the surface epithelium. Typical treatment of EOC involves cytoreductive surgery combined with chemotherapy. More recent therapies have targeted the tumor vasculature using antiangiogenic compounds such as thrombospondin-1 (TSP-1. TSP-1 mimetic peptides such as ABT-510 have been created and have been in various clinical trials. We have previously shown that ABT-510 reduces abnormal vasculature associated with tumor tissue and increases the presence of mature blood vessels. It has been hypothesized that treatment with antiangiogenic compounds would allow increased delivery of cytotoxic agents and enhance treatment. In this study, we evaluated the potential role of ABT-510 and various chemotherapeutics (cisplatin and paclitaxel on tumor progression, angiogenesis, and the benefits of combinational treatments on tissue uptake and perfusion using an orthotopic syngeneic mouse model of EOC. Animals were treated with ABT-510 (100 mg/kg per day alone or in combination with cisplatin (2 mg/kg per 3 days or paclitaxel (10 mg/kg per 2 days at 60 days after tumor induction. Radiolabeled and fluorescently labeled paclitaxel demonstrated a significant increase in tumor uptake after ABT-510 treatment. Combined treatment with ABT-510 and cisplatin or paclitaxel resulted in a significant increase in tumor cell and tumor endothelial cell apoptosis and a resultant decrease in ovarian tumor size. Combined treatment also regressed secondary lesions and eliminated the presence of abdominal ascites. The results from this study show that through vessel normalization, ABT-510 increases uptake of chemotherapy drugs and can induce regression of advanced ovarian cancer.

Nicole E. Campbell

2010-03-01

313

Setting the stage for electron transfer: Molecular basis of ABTS-binding to four laccases from Trametes versicolor at variable pH and protein oxidation state  

DEFF Research Database (Denmark)

Laccases are multi-copper oxidases having exquisite oxidation power, high stability, and multiple industrial applications. Although Km varies ?1000-fold across laccases, the molecular basis of substrate binding is poorly understood. Furthermore, laccase isoenzymes vary substantially in stability and activity for unknown reasons, and are thus useful probes of stability-function trade-offs relevant to protein engineering. We report here the first systematic comparison of ABTS-binding to different proteins, i.e. the four isoforms of Trametes versicolor, using a combination of sequence clustering, density functional theory calculations, homology modeling, and multiple induced-fit docking protocols at variable pH-dependent protonation states and T1-copper oxidation state. Clustering analysis provided a systematic overview of laccases across Trametes and revealed distinct isoenzyme classes (A–J) with the four T. versicolor isoforms belonging to separate classes. The T1 oxidation state had minor effect on ABTS binding, whereas the protonation state of Asp206 was important, consistent with site-directed mutagenesis studies. The absence of active poses for the ?-isoform agrees with its large Km, whereas the ?-isoform with the smallest Km also had most active poses with protonated Asp206 corresponding to its pHopt?2. Protonated Asp can bind to ABTS to form strong, active conformations partially explaining the low pHopt of fungal laccases toward ABTS. We identified several laccase properties optimal for ABTS binding. Notably, very high (R2?0.99) correlation was observed between logKm (ABTS) and binding-pocket charge due to sites 157, 161, 269, 271, and 333, i.e. laccases optimal for ABTS turnover have positively charged anchor points in their pockets. Our work also demonstrates how activity-constraints can markedly improve docking to reduce inactive false positives.

Christensen, Niels Johan; Kepp, Kasper Planeta

2014-01-01

314

BMX Acts Downstream of PI3K to Promote Colorectal Cancer Cell Survival and Pathway Inhibition Sensitizes to the BH3 Mimetic ABT-737  

Directory of Open Access Journals (Sweden)

Full Text Available Evasion of apoptosis is a hallmark of cancer, and reversing this process by inhibition of survival signaling pathways is a potential therapeutic strategy. Phosphoinositide 3-kinase (PI3K signaling can promote cell survival and is upregulated in solid tumor types, including colorectal cancer (CRC, although these effects are context dependent. The role of PI3K in tumorigenesis combined with their amenability to specific inhibition makes them attractive drug targets. However, we observed that inhibition of PI3K in HCT116, DLD-1, and SW620 CRC cells did not induce apoptotic cell death. Moreover, these cells were relatively resistant to the Bcl-2 homology domain 3 (BH3 mimetic ABT-737, which directly targets the Bcl-2 family of apoptosis regulators. To test the hypothesis that PI3K inhibition lowers the apoptotic threshold without causing apoptosis per se, PI3K inhibitors were combined with ABT-737. PI3K inhibition enhanced ABT-737-induced apoptosis by 2.3- to 4.5-fold and reduced expression levels of MCL-1, the resistance biomarker for ABT-737. PI3K inhibition enhanced ABT-737-induced apoptosis a further 1.4- to 2.4-fold in CRC cells with small interfering RNA-depleted MCL-1, indicative of additional sensitizing mechanisms. The observation that ABT-737-induced apoptosis was unaffected by inhibition of PI3K downstream effectors AKT and mTOR, implicated a novel PI3K-dependant pathway. To elucidate this, an RNA interference (RNAi screen of potential downstream effectors of PI3K signaling was conducted, which demonstrated that knockdown of the TEC kinase BMX sensitized to ABT-737. This suggests that BMX is an antiapoptotic downstream effector of PI3K, independent of AKT.

Danielle S. Potter

2014-02-01

315

BMX acts downstream of PI3K to promote colorectal cancer cell survival and pathway inhibition sensitizes to the BH3 mimetic ABT-737.  

Science.gov (United States)

Evasion of apoptosis is a hallmark of cancer, and reversing this process by inhibition of survival signaling pathways is a potential therapeutic strategy. Phosphoinositide 3-kinase (PI3K) signaling can promote cell survival and is upregulated in solid tumor types, including colorectal cancer (CRC), although these effects are context dependent. The role of PI3K in tumorigenesis combined with their amenability to specific inhibition makes them attractive drug targets. However, we observed that inhibition of PI3K in HCT116, DLD-1, and SW620 CRC cells did not induce apoptotic cell death. Moreover, these cells were relatively resistant to the Bcl-2 homology domain 3 (BH3) mimetic ABT-737, which directly targets the Bcl-2 family of apoptosis regulators. To test the hypothesis that PI3K inhibition lowers the apoptotic threshold without causing apoptosis per se, PI3K inhibitors were combined with ABT-737. PI3K inhibition enhanced ABT-737-induced apoptosis by 2.3- to 4.5-fold and reduced expression levels of MCL-1, the resistance biomarker for ABT-737. PI3K inhibition enhanced ABT-737-induced apoptosis a further 1.4- to 2.4-fold in CRC cells with small interfering RNA-depleted MCL-1, indicative of additional sensitizing mechanisms. The observation that ABT-737-induced apoptosis was unaffected by inhibition of PI3K downstream effectors AKT and mTOR, implicated a novel PI3K-dependant pathway. To elucidate this, an RNA interference (RNAi) screen of potential downstream effectors of PI3K signaling was conducted, which demonstrated that knockdown of the TEC kinase BMX sensitized to ABT-737. This suggests that BMX is an antiapoptotic downstream effector of PI3K, independent of AKT. PMID:24709422

Potter, Danielle S; Kelly, Paul; Denneny, Olive; Juvin, Veronique; Stephens, Len R; Dive, Caroline; Morrow, Christopher J

2014-02-01

316

Grafting of gallic acid onto chitosan enhances antioxidant activities and alters rheological properties of the copolymer.  

Science.gov (United States)

A new, simple, and effective method to graft gallic acid (GA) onto chitosan (CS) in aqueous solution in the presence of carbodiimide and hydroxybenzotriazole was developed. The grafting amount of GA reached as much as 209.9 mg/g of copolymer, which appears as the highest one among the reported literature, and the grafting degree of GA to CS was adjustable with modulation of the mass ratio of GA to CS. The covalent insertion of GA onto the polymeric backbones was confirmed by UV-vis and (1)H NMR analyses. Grafting endowed the resulting copolymer GA-grafted-CS (GA-g-CS) with both the advantages of CS and GA. The antioxidant capacity of GA-g-CS was much higher than that of the plain CS examined by assays of DPPH, superoxide, and ABTS radicals scavenging activities, reducing power, chelating power, inhibition of lipid peroxidation, ferric reducing antioxidant potential, and ?-carotene-linoleic acid assays. Particularly, GA-g-CS showed significantly higher antioxidant activity than GA in ?-carotene-linoleic acid assay. Furthermore, the viscosity of GA-g-CS was significantly higher than that of CS. The present study developed a novel approach to synthesize GA-g-CS that could be a potential biomaterial in food industries. PMID:25198516

Xie, Minhao; Hu, Bing; Wang, Yan; Zeng, Xiaoxiong

2014-09-17

317

Effect of Dietary Supplementation of the Combination of Gallic and Linoleic Acid in Thigh Meat of Broilers  

Science.gov (United States)

This study was performed to investigate the combined effect of dietary supplementation of gallic and linoleic acid (GL) on the antioxidative effect and quality of thigh meat from broilers. Broilers received 3 dietary treatments: i) commercial finisher diet (control), ii) 0.5% GL (gallic:linoleic acid = 1 M:1 M), and iii) 1.0% GL during the 22 to 36 d. The pH value of broiler thigh meat was increased by GL supplementation. Water holding capacity of the thigh meat was enhanced by the 1.0% dietary GL supplementation. Antioxidative effect (total phenolic content, DPPH radical scavenging activity, ABTS+ reducing activity, reducing power, and TBARS value) in the thigh from the broilers improved significantly with 1.0% GL. Linoleic acid and docosahexaenoic acids were higher in the broilers fed both levels of dietary GL. However, volatile basic nitrogen content and microbiological quality was not shown to be different between control and treated group. Results indicate that 1.0% dietary supplementation of GL can improve the antioxidant activity of broiler thigh meat and may enhance the meat quality. PMID:25049528

Lee, Kyung Haeng; Jung, Samooel; Kim, Hyun Joo; Kim, Il Suk; Lee, Jun Heon; Jo, Cheorun

2012-01-01

318

Photoionization of Hot Radicals  

Science.gov (United States)

The combination of velocity map imaging and tunable vacuum ultraviolet light has been used to determine the internal energy dependence of a number of small hydrocarbon radical. In these experiments, radicals are produced by the photodissociation of a suitable halogen-containing precursor, and the resulting images allow the determination of the internal energy of the radical. Comparison of the halogen image, which reflects the true translational energy distribution, and the radical image, which is a convolution between the true distribution and the internal-energy-dependent relative photoionization cross section, allows the extraction of the internal energy dependence of the crtoss section. In larger radicals, intramolecular vibrational energy redistribution minimizes the effect of vibrational excitation of the radical. This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biological Sciences under contract No. W-31-109-Eng-38.

Pratt, Stephen; Fan, Haiyan

2006-05-01

319

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

320

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

321

Radical Scavenging and Antioxidant Potential of Nuts and Leaves Extracts of Semecarpus anacardium (L.  

Directory of Open Access Journals (Sweden)

Full Text Available In the present investigation, antioxidant activity of the crude extracts from nuts and leaves of S. anacardium was carried out. The antioxidant potential of various extracts (ethanol, acetone and aqueous of S. anacardium was determined by using DPPH assay, ABTS assay and metal chelating activity assay. Among the extracts the ethanol extract of nut showed significant scavenging activity (DPPH-88.73 ± 2.26; ABTS assay-81.65 ± 1.57 and metal chelating activity-72.37 ± 2.26 compared with antioxidant controls, ascorbic acid and BHA respectively. The findings of the present investigation suggest that the S. anacardium extracts can prove to be a potent source of biologically active compounds that can be further subjected to isolation of therapeutic antioxidant agents.

Nachiketa Barman

2013-07-01

322

Hydroxyl radical production by H2O2-mediated oxidation of Fe(II) complexed by Suwannee River fulvic acid under circumneutral freshwater conditions.  

Science.gov (United States)

The Fenton reaction, the oxidation of ferrous iron by hydrogen peroxide (H(2)O(2)), is typically assumed to be a source of hydroxyl radical (HO(•)) in natural systems, however, formation of HO(•) in this process is strongly dependent upon solution pH and the ligand environment, with HO(•) only formed when Fe(II) is organically complexed. In this study we examine the formation of HO(•) when Fe(II)-NOM complexes are oxidized by H(2)O(2) using phthalhydrazide as a probe for HO(•). We demonstrate that HO(•) formation can be quantitatively described using a kinetic model that assumes HO(•) formation occurs solely from the reaction of Fe(II)-NOM complexes with H(2)O(2), even though this reaction is sufficiently slow to play only a negligible role in the overall oxidation rate of total Fe(II). As such, NOM is seen to play a dual role in circumneutral natural systems in stabilizing Fe(II) toward oxidation by H(2)O(2) while enabling the formation of HO(•) through this oxidation process. PMID:23231429

Miller, Christopher J; Rose, Andrew L; Waite, T David

2013-01-15

323

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

324

Oxidation of SO2 by stabilized Criegee intermediate (sCI radicals as a crucial source for atmospheric sulfuric acid concentrations  

Directory of Open Access Journals (Sweden)

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

325

Oxidation of SO2 by stabilized Criegee Intermediate (sCI radicals as a crucial source for atmospheric sulphuric acid concentrations  

Directory of Open Access Journals (Sweden)

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

326

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

327

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

OpenAIRE

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 s...

Li, J. L.; Zhao, Y.; Hua, W.; He, S. Z.; Chen, Z. M.; Zhang, X.

2009-01-01

328

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

329

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

330

Phenolic content and radical scavenging properties of natural extracts for traditional care of domestic animals in Mediterranean areas  

OpenAIRE

Extracts of plants traditionally used for treatments on animals were tested for total phenolic, non tannic phenolic, condensed tannins and total flavonoid content. Antioxidant properties were determined using 2,2’-azinobis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) chemical assays following DMSO extraction. We also assessed the toxicity of extracts on cell viability and determined their ability to modulate the production of i...

Piluzza, Giovanna Antonia Maria; Musino, Lorena; Manunta, Maria; Bullitta, Simonetta Maria

2013-01-01

331

Free radicals in biology. Volume II  

International Nuclear Information System (INIS)

This volume continues the treatment of topics in free radical biology and free radical pathology from Volume I. In the first chapter, pyridinyl radicals, radicals which are models for those derived from NAD, are discussed. Pyridinyl radicals can be synthesized and isolated and directly studied in a number of chemical systems. The next chapter treats the role of glutathione in the cell. It is becoming even more apparent that this vital thiol controls a large number of important cellular functions. The GSH/GSSG balance has recently been implicated as a control for cellular development; this balance also may be important in relaying the effects of oxidants from one site to another in the body. The next chapter outlines the reactions of singlet oxygen; some of these involve free radicals and some do not. This reactive intermediate appears to be important both in photochemical smog and in cellular chemistry where singlet oxygen is produced by nonphotochemical processes. The production of free radicals from dry tissues, a controversial area with conflicting claims is reviewed. The next chapter outlines the current status of the studies of photochemical smog. The next two chapters treat specific reactive materials which are present in smog. The first discusses the chemistry of nitrogen oxides and ozone. The second chapter treats the chemistry of the peroxyacyl nitrites. These compounds, although present in only small concentration, are among the most toxic components of smogre among the most toxic components of smog. The last two chapters treat radiation damage to proteins and radiation protection and radical reactions produced by radiation in nucleic acids

332

Safety and Efficacy of ABT-089 in Pediatric Attention-Deficit/Hyperactivity Disorder: Results from Two Randomized Placebo-Controlled Clinical Trials  

Science.gov (United States)

Objective: To assess the safety and efficacy of ABT-089, a novel alpha[subscript 4]beta[subscript 2] neuronal nicotinic receptor partial agonist, vs. placebo in children with attention-deficit/hyperactivity disorder (ADHD). Method: Two multicenter, randomized, double-blind, placebo-controlled, parallel-group studies of children 6 through 12 years…

Wilens, Timothy E.; Gault, Laura M.; Childress, Ann; Kratochvil, Christopher J.; Bensman, Lindsey; Hall, Coleen M.; Olson, Evelyn; Robieson, Weining Z.; Garimella, Tushar S.; Abi-Saab, Walid M.; Apostol, George; Saltarelli, Mario D.

2011-01-01

333

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 con prostatectomia laparoscópica (pura o asistida por robot), pudiesen tener mayor riesgo de recurrencia de la enfermedad. Esta es una posición discutible, ya que el análisis, a pesar de ser extenso es limitado para establecer conclusiones finales en el tema. Es importante recordar que la PRL sigue siendo una intervención técnicamente difícil y debiera ser realizada en centros seleccionados con equipos experimentados. La prostatectomía laparoscópica asistida por Robot, facilita el procedimiento y en suma, pareciera mejorar los resultados oncológicos y funcionales. La PRL es hoy en día una alternativa válida a la prostatectomía retropúbica tradicional, con ciertas ventajas adicionales. Abstract in english Radical laparosocpic prostatectomy (RLP) is an attractive therapeutic modality for localized prostate cancer. The results obtained with this technique are similar to those obtained with open radical prostatectomy, which continues to be the gold standard for the treatment of prostate cancer. The surg [...] ical access for RLP can be extra-peritoneal or trans-peritoneal. The advantages of laparoscopy are lower bleeding rates, less need for transfusion and shorter recuperation time and hospital stay. The oncological results of RLP are similar, but in any case better, that those obtained with open retropubic radical prostatectomy. Recent reports raised the concern that laparoscopic prostatectomy could have higher rates of relapse of cancer. However this opinion is questionable. RLP is a difficult technique and should be performed by experienced teams. Robot assistance facilitates the procedure and could improve functional and oncological results. Therefore RLP is nowadays an alternative to traditional retropubic prostatectomy.

OCTAVIO A, CASTILLO C; IVAR, VIDAL-MORA; RAFAEL, SÁNCHEZ-SALAS.

2011-04-01

334

Radical chemistry of artemisinin  

International Nuclear Information System (INIS)

The review summarizes physicochemical characteristics of the natural sesquiterpene peroxide artemisinin. The kinetic schemes of transformations of artemisinin radicals under anaerobic conditions are presented and analyzed. The sequence of radical reactions of artemisinin in the presence of oxygen is considered in detail. Special emphasis is given to the intramolecular chain oxidation resulting in the transformation of artemisinin into polyatomic hydroperoxide. The kinetic characteristics of elementary reaction steps involving alkyl, alkoxyl, and peroxyl radicals generated from artemisinin are discussed. The results of testing of artemisinin and its derivatives for the antimalarial activity and the scheme of the biochemical synthesis of artemisinin in nature are considered.

335

Radical chemistry of artemisinin  

Energy Technology Data Exchange (ETDEWEB)

The review summarizes physicochemical characteristics of the natural sesquiterpene peroxide artemisinin. The kinetic schemes of transformations of artemisinin radicals under anaerobic conditions are presented and analyzed. The sequence of radical reactions of artemisinin in the presence of oxygen is considered in detail. Special emphasis is given to the intramolecular chain oxidation resulting in the transformation of artemisinin into polyatomic hydroperoxide. The kinetic characteristics of elementary reaction steps involving alkyl, alkoxyl, and peroxyl radicals generated from artemisinin are discussed. The results of testing of artemisinin and its derivatives for the antimalarial activity and the scheme of the biochemical synthesis of artemisinin in nature are considered.

Denisov, Evgenii T; Solodova, S L; Denisova, Taisa G [Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow Region (Russian Federation)

2010-12-29

336

Radical chemistry of artemisinin  

Science.gov (United States)

The review summarizes physicochemical characteristics of the natural sesquiterpene peroxide artemisinin. The kinetic schemes of transformations of artemisinin radicals under anaerobic conditions are presented and analyzed. The sequence of radical reactions of artemisinin in the presence of oxygen is considered in detail. Special emphasis is given to the intramolecular chain oxidation resulting in the transformation of artemisinin into polyatomic hydroperoxide. The kinetic characteristics of elementary reaction steps involving alkyl, alkoxyl, and peroxyl radicals generated from artemisinin are discussed. The results of testing of artemisinin and its derivatives for the antimalarial activity and the scheme of the biochemical synthesis of artemisinin in nature are considered.

Denisov, Evgenii T.; Solodova, S. L.; Denisova, Taisa G.

2010-12-01

337

The activity of a new 2-amino-1,3,4-thiadiazole derivative 4ClABT in cancer and normal cells  

Directory of Open Access Journals (Sweden)

Full Text Available The 2-amino-5-(2,4-dihydroxyphenyl-1,3,4-thiadiazole set are well known compounds with interesting in vitro and in vivo anti-cancer profiles. The aim of this study was an in vitro evaluation of the anti-cancer activity of a new synthesized aminothiadiazole derivative 2-(3-chlorophenyloamino-5-(2,4-dihydroxyphenyl- -1,3,4-thiadiazole 4ClABT. The effect on tumor cell proliferation, motility and morphology, DNA synthesis as well as the influence on normal cells was assessed. The antiproliferative activity of 4ClABT in tumor cells derived from peripheral cancers including breast carcinoma (T47D, colon carcinoma (HT-29, thyroid carcinoma (FTC-238, teratoma (P19, and T-cell leukemia (Jurkat E6.1, as well as cancers of the nervous system including rhabdomyosarcoma/medulloblastoma (TE671, brain astrocytoma (MOGGCCM and glioma (C6 was studied by means of MTT assay. DNA synthesis level was determined in BrdU ELISA test. Wound assay model was applied for tumor cell motility assessment. Morphological changes induced by 4ClABT in cancer and normal cells were analyzed in HE staining specimens. Moreover, the influence of 4ClABT on normal cells including skin fibroblasts (HSF, hepatocytes (Fao, astroglia and neurons was studied by means of LDH assay. The tested compound inhibited the proliferation of tumor cells in dose-dependent fashion. The anti-cancer effect was attributed to decreased DNA synthesis, prominent changes in tumor cell morphology as well as reduced cell motility. In antiproliferative concentrations, 4ClABT was not toxic to normal cells. Our study showed prominent anti-cancer effects of the tested aminothiadiazole derivative in the absence of toxicity in normal cells. The obtained results confirmed the promising anti-cancer profile of previously tested 2-(monohalogenphenylamino- -5-(2,4-dihydroxyphenyl-1,3,4-thiadiazole derivatives (ClABT — chlorophenyl derivative, FABT and 3FABT — fluorophenyl derivatives and 4BrABT — bromophenyl derivative. The molecular mechanisms and the in vivo activity of aminothiadiazole derivatives will be the subject of further studies. (Folia Histochemica et Cytobiologica 2011; Vol. 49, No. 3, pp. 436–444

Andrzej Niewiadomy

2011-10-01

338

A lipoxygenase from red alga Pyropia haitanensis, a unique enzyme catalyzing the free radical reactions of polyunsaturated fatty acids with triple ethylenic bonds.  

Science.gov (United States)

Lipoxygenases (LOXs) are key enzymes to regulate the production of hormones and defensive metabolites in plants, animals and algae. In this research, a full length LOX gene has been cloned and expressed from the red alga Pyropia haitanensis (Bangiales, Rhodophyta) gametophyte (PhLOX2). Subsequent phylogenetic analysis showed that such LOX enzymes are separated at the early stage of evolution, establishing an independent branch. The LOX activity was investigated at the optimal pH of 8.0. It appears that PhLOX2 is a multifunctional enzyme featuring both lipoxygenase and hydroperoxidase activities. Additionally, PhLOX2 exhibits remarkable substrate and position flexibility, and it can catalyze an array of chemical reactions involving various polyunsaturated fatty acids, ranging from C18 to C22. As a matter of fact, mono-hydroperoxy, di-hydroperoxy and hydroxyl products have been obtained from such transformations, and eicosapentaenoic acid seem to be the most preferred substrate. It was found that at least triple ethylenic bonds are required for PhLOX2 to function as a LOX, and the resulting hydroxy products should be originated from the PhLOX2 mediated reduction of mono-hydroperoxides, in which the hydrogen abstraction occurs on the carbon atom between the second and third double bond. Most of the di-hydroperoxides observed seem to be missing their mono-position precursors. The substrate and position flexibility, as well as the function versatility of PhLOXs represent the ancient enzymatic pathway for organisms to control intracellular oxylipins. PMID:25658744

Zhu, Zhujun; Qian, Feijian; Yang, Rui; Chen, Juanjuan; Luo, Qijun; Chen, Haimin; Yan, Xiaojun

2015-01-01

339

A Lipoxygenase from Red Alga Pyropia haitanensis, a Unique Enzyme Catalyzing the Free Radical Reactions of Polyunsaturated Fatty Acids with Triple Ethylenic Bonds  

Science.gov (United States)

Lipoxygenases (LOXs) are key enzymes to regulate the production of hormones and defensive metabolites in plants, animals and algae. In this research, a full length LOX gene has been cloned and expressed from the red alga Pyropia haitanensis (Bangiales, Rhodophyta) gametophyte (PhLOX2). Subsequent phylogenetic analysis showed that such LOX enzymes are separated at the early stage of evolution, establishing an independent branch. The LOX activity was investigated at the optimal pH of 8.0. It appears that PhLOX2 is a multifunctional enzyme featuring both lipoxygenase and hydroperoxidase activities. Additionally, PhLOX2 exhibits remarkable substrate and position flexibility, and it can catalyze an array of chemical reactions involving various polyunsaturated fatty acids, ranging from C18 to C22. As a matter of fact, mono-hydroperoxy, di-hydroperoxy and hydroxyl products have been obtained from such transformations, and eicosapentaenoic acid seem to be the most preferred substrate. It was found that at least triple ethylenic bonds are required for PhLOX2 to function as a LOX, and the resulting hydroxy products should be originated from the PhLOX2 mediated reduction of mono-hydroperoxides, in which the hydrogen abstraction occurs on the carbon atom between the second and third double bond. Most of the di-hydroperoxides observed seem to be missing their mono-position precursors. The substrate and position flexibility, as well as the function versatility of PhLOXs represent the ancient enzymatic pathway for organisms to control intracellular oxylipins. PMID:25658744

Zhu, Zhujun; Qian, Feijian; Yang, Rui; Chen, Juanjuan; Luo, Qijun; Chen, Haimin; Yan, Xiaojun

2015-01-01

340

Effect of substituents on different channels of ·OH radical reaction with substituted organic sulfides  

International Nuclear Information System (INIS)

Pulse radiolysis technique has been employed to study the nature of ·OH radical reaction in aqueous solutions of substituted organic sulfides. The transient absorption band at 345 nm observed on reaction of ·OH radicals in neutral aqueous solution of 3,3'-thiodipropionitrile is assigned to OH-adduct at sulfur. OH-adduct is observed to have high reactivity with oxygen (k=8.8x108 dm3 mol-1 s-1). The reaction of ·OH radicals in neutral aqueous solution of methyl propyl sulfide has shown the formation of sulfur-centered dimer radical cation with a small fraction (?10%) of?-(alkylthio)alkyl radicals. The reaction of ·OH radicals with thiodiglycolic acid showed an absorption band at 285 nm, which is assigned to ? -(alkylthio)alkyl radicals. The reaction of ·OH radicals with dimethyl 2,2'-thiodiethanoic acid has been assigned to OH-adduct at sulfur, whereas the transient absorption band at 390 observed with 3,3'-thiodipropionic acid is assigned to intra-molecular radical cation formed on p-orbital overlap of oxidized sulfur with oxygen. In acidic solutions, sulfur-centered dimer radical cation is the only transient species observed with substituted alkyl sulfides. The concentration of acid required to observe the formation of dimer radical cation is found to depend on the electron-withdrawing power of the substituted group. The reaction of ·OH radicals in n of ·OH radicals in neutral aqueous solution of substituted aryl sulfides has shown the formation of monomer radical cation and OH-adduct at benzene ring. Sulfur-centered dimer radical cations are not observed even in acidic conditions

341

Hydroxyl radicals in indoor environments  

Science.gov (United States)

Indoor hydroxyl radical concentrations were estimated using a new indoor air quality model which employs the SAPRC-99 atmospheric chemistry model to simulate indoor homogenous reactions. Model results indicate that typical indoor hydroxyl radical concentrations are lower than typical outdoor summertime urban hydroxyl radical levels of 5-10×10 6 molecules cm -3; however, indoor levels can be similar to or greater than typical nighttime outdoor hydroxyl radical levels of approximately 5×10 4 molecules cm -3. Effects of selected parameters on indoor hydroxyl radical concentrations are presented herein. Indoor hydroxyl radical concentrations are predicted to increase non-linearly with increasing outdoor ozone concentrations, indoor alkene emission rates, and air exchange rates. Indoor hydroxyl radical concentrations decrease with increasing outdoor nitric oxide concentrations. Indoor temperature and indoor light intensity have moderate impacts on indoor hydroxyl radical concentrations. Outdoor hydroxyl radical concentrations, outdoor nitrate (NO 3rad ) radical concentrations, outdoor hydroperoxy radical concentrations, and hydroxyl radical removal by indoor surfaces are predicted to have no appreciable impact on indoor hydroxyl radical concentrations. Production of hydroxyl radicals in indoor environments appears to be controlled primarily by reactions of alkenes with ozone, and nitric oxide with hydroperoxy radical. Estimated indoor hydroxyl radical levels may potentially affect indoor air quality. Two examples are presented in which reactions of d-limonene and ?-pinene with indoor hydroxyl radicals produce aldehydes, which may be of greater concern than the original compounds.

Sarwar, Golam; Corsi, Richard; Kimura, Yosuke; Allen, David; Weschler, Charles J.

342

Hydroxyl radicals in indoor environments  

Energy Technology Data Exchange (ETDEWEB)

Indoor hydroxyl radical concentrations were estimated using a new indoor air quality model which employs the SAPRC-99 atmospheric chemistry model to simulate indoor homogenous reactions. Model results indicate that typical indoor hydroxyl radical concentrations are lower than typical outdoor summertime urban hydroxyl radical levels of 5-10 x 10{sup 6} molecules cm{sup -3}; however, indoor levels can be similar to or greater than typical nighttime outdoor hydroxyl radical levels of approximately 5 x 10{sup 4} molecules cm{sup -3}. Effects of selected parameters on indoor hydroxyl radical concentrations are presented herein. Indoor hydroxyl radical concentrations are predicted to increase non-linearly with increasing outdoor ozone concentrations, indoor alkene emission rates, and air exchange rates. Indoor hydroxyl radical concentrations decrease with increasing outdoor nitric oxide concentrations. Indoor temperature and indoor light intensity have moderate impacts on indoor hydroxyl radical concentrations. Outdoor hydroxyl radical concentrations, outdoor nitrate (NO{sub 3}) radical concentrations, outdoor hydroperoxy radical concentrations, and hydroxyl radical removal by indoor surfaces are predicted to have no appreciable impact on indoor hydroxyl radical concentrations. Production of hydroxyl radicals in indoor environments appears to be controlled primarily by reactions of alkenes with ozone, and nitric oxide with hydroperoxy radical. Estimated indoor hydroxyl radical levels may potentially affect indoor air quality. Two examples are presented in which reactions of d-limonene and {alpha}-pinene with indoor hydroxyl radicals produce aldehydes, which may be of greater concern than the original compounds.(author)

Sarwar, G.; Corsi, R.; Kimura, Yosuke; Allen, D. [University of Texas, Austin, TX (United States). Center for Energy and Environmental Resources; Weschler, C.J. [Rutgers Univ., Piscataway, NJ (United States). Environmental and Occupational Health Sciences Inst.

2002-08-01

343

Poly (N-vinyl-2-pyrrolidone-co-acrylic acid): Comparing of Traditional Heating and Microwave-Assisted Free Radical Polymerization  

International Nuclear Information System (INIS)

In organic chemistry microwave irradiation has become a common heat source and the use of microwave irradiation is also increasingly studied for polymerization reactions. Polymers have been synthesized at long reaction times by classical thermal methods. In contrast, microwave-assisted polymer synthesis is a well-known and most useful method, which is requiring shorter reaction times. In this study, our aims are to compare THPS and MAPS methods between themselves, and investigate the effect of temperature in MAPS method at different parameters such as reaction times, weight average molecular weight (Mw), polydispersity index (PDI), hydrodynamic radius (Rh), intrinsic and Mark Houwink equation constant (a) of copolymers, viscosity Firstly we synthesized N-vinyl-2-pyrrolidone-acrylic acid copolymers (P(VP-co-AA)) both with traditional heating polymer synthesis (THPS) and microwave-assisted polymer synthesis (MAPS) method comparatively in this study. Secondly, to research temperature effect on MAPS method in addition to microwave irradiation power, polymer synthesis at 40 degree C, 50 degree C and 80 degree C were tried. For analyzing of copolymers Fourier Transform Infrared (FT-IR) spectroscopy and Gel Permeation Chromatography (GPC) system with four detectors were used. (author)

344

MCL-1 and BCL-xL-dependent resistance to the BCL-2 inhibitor ABT-199 can be overcome by preventing PI3K/AKT/mTOR activation in lymphoid malignancies.  

Science.gov (United States)

Overexpression of anti-apoptotic BCL-2 family members is a hallmark of many lymphoid malignancies, including chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma (NHL) that can be targeted with small molecule inhibitors. ABT-199 is a rationally designed BCL-2 homology (BH)-3 mimetic that specifically binds to BCL-2, but not to MCL-1 and BCL-xL. Although the thrombocytopenia that occurs with navitoclax treatment has not been a problem with ABT-199, clinical trials in CLL could benefit by lowering the ABT-199 concentration through targeting other survival pathways. In this study, we investigated the mechanisms of resistance that develops to ABT-199 therapy by generating ABT-199-resistant (ABT199-R) cell lines via chronic exposure of NHL cell lines to ABT-199. Acquired resistance resulted in substantial AKT activation and upregulation of MCL-1 and BCL-xL levels that sequestered BIM. ABT199-R cells exhibited increased MCL-1 stability and failed to activate BAX in response to ABT-199. The ABT-199 acquired and inherent resistant cells were sensitized to treatment with ABT-199 by inhibitors of the PI3K, AKT, and mTOR pathways, NVP-BEZ235 and GS-1101. NVP-BEZ235, a dual inhibitor of p-AKT and mTOR, reduced MCL-1 levels causing BIM release from MCL-1 and BCL-xL, thus leading to cell death by BAX activation. The PI3K? inhibitor GS-1101 (idelalisib) downregulated MCL-1 and sensitized ABT199-R cells through AKT-mediated BAX activation. A genetic approach, through siRNA-mediated down-regulation of AKT, MCL-1, and BCL-xL, significantly decreased cell survival, demonstrating the importance of these cell survival factors for ABT-199 resistance. Our findings suggest a novel mechanism that modulates the expression and activity of pro-survival proteins to confer treatment resistance that could be exploited by a rational combination therapeutic regimen that could be effective for treating lymphoid malignancies. PMID:25590803

Choudhary, G S; Al-Harbi, S; Mazumder, S; Hill, B T; Smith, M R; Bodo, J; Hsi, E D; Almasan, A

2015-01-01

345

Lipid radicals: Properties and detection by spin trapping  

International Nuclear Information System (INIS)

Unsaturated lipids are rapidly oxidized to toxic products such as lipid hydroperoxides, especially when transition metals such as iron or copper are present. In a Fenton-type reaction Fe2+ converts lipid hydroperoxides to the very short-lived lipid alkoxyl radicals. The reaction was started upon the addition of Fe2+ to an aqueous linoleic acid hydroperoxide (LOOH) emulsion and the spin trap in the absence of oxygen. Even when high concentrations of spin traps were added to the incubation mixture, only secondary radical adducts were detected, probably due to the rapid rearrangement of the primary alkoxyl radicals. With the commercially available nitroso spin trap MNP we observed a slightly immobilized ESR spectrum with only one hydrogen splitting, indicating the trapping of a methinyl fragment of a lipid radical. With DMPO or 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO) adducts were detected with carbon-centered lipid radical, with acyl radical, and with the hydroxyl radical. We also synthesized lipophilic derivatives of the spin trap DEPMPO in order to detect lipid radical species generated in the lipid phase. With all spin traps studied a lipid-derived carbon-centered radical was obtained in the anaerobic incubation system Fe2+/LOOH indicating the trapping of a lipid radical, possibly generated as a secondary reaction product of the primary lipid alkoxyl radical formed. Under aerobic conditions an SOD-insensitive oxygen-obic conditions an SOD-insensitive oxygen-centered radical adduct was formed with DEPMPO and its lipophilic derivatives. The observed ESR parameters were similar to those of alkoxyl radical adducts, which were independently synthesized in model experiments using Fe3+-catalyzed nucleophilic addition of methanol or t-butanol to the respective spin trap. (author)

346

Resveratrol products resulting by free radical attack  

International Nuclear Information System (INIS)

Trans-resveratrol (trans-3,4',5-trihydroxystilbene; RES), which is contained in red wine and many plants, is one of the most relevant and extensively investigated stilbenes with a broad spectrum of biological activities. Among other duties, RES has been reported to have anti-carcinogenetic activities, which could be attributed to its antioxidant properties. The degradation of RES was studied under various conditions. The products (aldehydes, carboxylic acids, etc.) generated from RES by the attack of free radicals were registered as a function of the radical concentration (absorbed radiation dose). Based on the obtained data it appears that the OH radicals are initiating the rather complicated process, which involves of the numerous consecutive reactions. A possible starting reaction mechanism is presented

347

Petroleum films exposed to sunlight produce hydroxyl radical.  

Science.gov (United States)

Sunlight exposed oil films on seawater or pure water produced substantial amounts of hydroxyl radical as a result of irradiation. Oil was collected from the surface of the Gulf of Mexico following the Deepwater Horizon spill and exposed to simulated sunlight in thin films over water. Photochemical production of hydroxyl radical was measured with benzoic acid as a selective chemical probe in the aqueous layer. Total hydroxyl radical formation was studied using high benzoic acid concentrations and varying exposure time. The total amount of hydroxyl radical produced in 24 h irradiations of thin oil films over Gulf of Mexico water and pure water were 3.7×10(-7) and 4.2×10(-7) moles respectively. Steady state concentrations of hydroxyl radical were measured using a competition kinetics approach. Hydroxyl radical concentrations of 1.2×10(-16) to 2.4×10(-16) M were observed for seawater and pure water under oil films. Titanium dioxide (TiO2) nanomaterials were added to the system in an effort to determine if the photocatalyst would enhance oil photodegradation. The addition of TiO2 nanoparticles dramatically changed the observed formation rate of hydroxyl radical in the systems with NP water at pH 3, showing increased formation rate in many cases. With photocatalyst, the steady state concentration of radical decreased, predominantly due to an increase in the hydroxyl radical scavenging rate with oxide present. This study illustrates that oil is a strong and important source of hydroxyl radical when exposed to sunlight. The fate of oil and other dissolved species following oil spills will be heavily dependent on the formation and fate of hydroxyl radical. PMID:24405967

Ray, Phoebe Z; Tarr, Matthew A

2014-05-01

348

The amorphous solid dispersion of the poorly soluble ABT-102 forms nano/microparticulate structures in aqueous medium: impact on solubility  

Directory of Open Access Journals (Sweden)

Full Text Available Kerstin J Frank,1,3 Ulrich Westedt,2 Karin M Rosenblatt,2 Peter Hölig,2 Jörg Rosenberg,2 Markus Mägerlein,2 Gert Fricker,3 Martin Brandl11Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Odense, Denmark; 2Abbott GmbH and Co. KG, Ludwigshafen, Germany; 3Department of Pharmaceutical Technology, University of Heidelberg, Heidelberg, GermanyAbstract: Amorphous solid dispersions (ASDs are a promising formulation approach for poorly soluble active pharmaceutical ingredients (APIs, because they ideally enhance both dissolution rate and solubility. However, the mechanism behind this is not understood in detail. In the present study, we investigated the supramolecular and the nano/microparticulate structures that emerge spontaneously upon dispersion of an ASD in aqueous medium and elucidated their influence on solubility. The ASD, prepared by hot melt extrusion, contained the poorly soluble ABT-102 (solubility in buffer, 0.05 µg/mL, a hydrophilic polymer, and three surfactants. The apparent solubility of ABT-102 from the ASD-formulation was enhanced up to 200 times in comparison to crystalline ABT-102. At the same time, the molecular solubility, as assessed by inverse equilibrium dialysis, was enhanced two times. Asymmetrical flow field-flow fractionation in combination with a multiangle light-scattering detector, an ultraviolet detector, and a refractometer enabled us to separate and identify the various supramolecular assemblies that were present in the aqueous dispersions of the API-free ASD (placebo and of binary/ternary blends of the ingredients. Thus, the supramolecular assemblies with a molar mass between 20,000 and 90,000 could be assigned to the polyvinylpyrrolidone/vinyl acetate 64, while two other kinds of assemblies were assigned to different surfactant assemblies (micelles. The amount of ABT-102 remaining associated with each of the assemblies upon fractionation was quantified offline with high-performance liquid chromatography–ultraviolet-visible. The polymeric and the micellar fraction contributed to the substantial increase in apparent solubility of ABT-102. Furthermore, a microparticulate fraction was isolated by centrifugation and analyzed by scanning electron microscopy, X-ray scattering, and infrared spectroscopy. The microparticles were found to be amorphous and to contain two of the surfactants besides ABT-102 as the main component. The amorphous microparticles are assumed to be the origin of the observed increase in molecular solubility ("true" supersaturation.Keywords: solid dispersion, AFlFFF, micelles, solubility, supersaturation

Frank KJ

2012-11-01

349

In vitro radical scavenging and cytotoxic activities of novel hybrid selenocarbamates.  

Science.gov (United States)

Novel selenocyanate and diselenide derivatives containing a carbamate moiety were synthesised and evaluated in vitro to determine their cytotoxic and radical scavenging properties. Cytotoxic activity was tested against a panel of human cell lines including CCRF-CEM (lymphoblastic leukaemia), HT-29 (colon carcinoma), HTB-54 (lung carcinoma), PC-3 (prostate carcinoma), MCF-7 (breast adenocarcinoma), 184B5 (non-malignant, mammary gland derived) and BEAS-2B (non-malignant, derived from bronchial epithelium). Most of the compounds displayed high antiproliferative activity with GI50 values below 10?M in MCF-7, CCRF-CEM and PC-3 cells. Radical scavenging properties of the new selenocompounds were confirmed testing their ability to scavenge DPPH and ABTS radicals. Based on the activity of selenium-based glutathione peroxidases (GPxs), compounds 1a, 2e and 2h were further screened for their capacity to reduce hydrogen peroxide under thiol presence. Results suggest that compound 1a mimics GPxs activity. Cytotoxic parameters, radical scavenging activity and ADME profile point to 1a as promising drug candidate. PMID:25792142

Romano, Beatriz; Plano, Daniel; Encío, Ignacio; Palop, Juan Antonio; Sanmartín, Carmen

2015-04-15

350

Pomegranate seed oil: Effect on 3-nitropropionic acid-induced neurotoxicity in PC12 cells and elucidation of unsaturated fatty acids composition.  

Science.gov (United States)

Background Seed oils are used as cosmetics or topical treatment for wounds, allergy, dandruff, and other purposes. Natural antioxidants from plants were recently reported to delay the onset or progress of various neurodegenerative conditions. Over one thousand cultivars of Punica granatum (Punicaceae) are known and some are traditionally used to treat various ailments. Aim The effect of pomegranate oil on 3-nitropropionic acid- (3-NP) induced cytotoxicity in rat pheochromocytoma (PC12) neuronal cells was analyzed in this study. Furthermore, the analysis of unsaturated fatty acid composition of the seed oil of pomegranate by gas chromatography-electron impact mass spectrometry (GC-MS) was done. Results GC-MS study showed the presence of 6,9-octadecadiynoic acid (C18:2(6,9)) as a major component (60%) as 4,4-dimethyloxazoline derivative. The total extractable oil with light petroleum ether by Soxhlet from the dry seed of P. granatum was 4-6%. The oil analyzed for 48.90 ±?1.50 mg gallic acid equivalents/g of oil, and demonstrated radical-scavenging-linked antioxidant activities in various in vitro assays like the DPPH (2,2-diphenyl-l-picrylhydrazyl, % IP = 35.2 ± 0.9%), ABTS (2,2'-azino-bis-3-ethylene benzothiozoline-6-sulfonic acid, % IP 2.2 ± 0.1%), and ?-carotene bleaching assay (% IP = 26 ± 3%), respectively, which could be due the possible role of one methylene interrupted diynoic acid system for its radical-scavenging/antioxidant properties of oil. The oil also reduced lipid peroxidation, suppressed reactive oxygen species, extracellular nitric oxide, lactate/pyruvate ratio, and lactase dehydrogenase generated by 3-NP- (100 mM) induced neurotoxicity in PC12 cells, and enhanced the levels of enzymatic and non-enzymatic antioxidants at 40 ?g of gallic acid equivalents. Conclusion The protective effect of pomegranate seed oil might be due to the ability of an oil to neutralize ROS or enhance the expression of antioxidant gene. PMID:25238165

Al-Sabahi, Bushra N; Fatope, Majek O; Essa, Musthafa Mohamed; Subash, Selvaraju; Al-Busafi, Saleh N; Al-Kusaibi, Fatma S N; Manivasagam, Thamilarasan

2014-09-19

351

Anesthesia for radical prostatectomy  

Directory of Open Access Journals (Sweden)

Full Text Available Radical prostatectomy is one of most common treatment options currently recommended for clinically localized prostate cancer. Evaluation of intraoperative and postoperative complications is important in evaluation of relative morbidity of this treatment option. Furthermore, investigation of complications of surgical treatment in correlation with not only surgical technique, but comorbidity, ASA stage and anesthetic technique enables improvements in complete perioperative treatment and decrease of incidence of complications resulting from the procedure. Improvement of anesthetic techniques and use of new anesthetic agents contributes to better outcome of surgical treatment. For radical surgery, combined epidural analgesia and general anesthesia reduces postoperative complications and mortality. Benefits can be conferred most likely by altered coagulation activation in surgery, increased blood flow, reduction of operative stress response. Modalities for reduction of intraoperative blood loss during radical prostatectomy are normovolemic haemodilution, preoperative donation of blood for autologus transfusion and use of erythropoietin for increasing red cell mass.

Hadži-?oki? J.

2005-01-01

352

Hydroxyl radical reactions and the radical scavenging activity of ?-carboline alkaloids.  

Science.gov (United States)

?-Carbolines are bioactive pyridoindole alkaloids occurring in foods, plants and the human body. Their activity as hydroxyl radical (OH) scavengers is reported here by using three different methods: deoxyribose degradation, hydroxylation of benzoate and hydroxylation of 2'-deoxyguanosine to give 8-hydroxy-2'-deoxyguanosine (8-OHdG) as assessed by RP-HPLC (MS). Fenton reactions (Fe(2+)/Fe(3+) plus H2O2) were used for OH generation, and the radical increased in the presence of ascorbic acid or 6-hydroxydopamine as pro-oxidants. ?-Carbolines were scavengers of OH in the three assays and in the presence of pro-oxidants. Tetrahydro-?-carboline-3-carboxylic acids were active against the hydroxylation of 2'-deoxyguanosine. ?-Carbolines reacted with hydroxyl radicals (OH) affording hydroxy-?-carbolines, whereas tetrahydro-?-carbolines gave oxidative and degradation products. On the basis of IC50 and reaction rates (k), ?-carbolines (norharman and harman), and tetrahydro-?-carbolines (tetrahydro-?-carboline, 1-methyltetrahydro-?-carboline and pinoline) were good OH radical scavengers and their activity was comparable to that of the indole, melatonin, which is an effective hydroxyl radical scavenger and antioxidant. PMID:25442601

Herraiz, Tomás; Galisteo, Juan

2015-04-01

353

Antioxidant activity of hyaluronic acid investigated by means of chemiluminescence of equine neutrophil bursts and electron paramagnetic resonance spectroscopy.  

Science.gov (United States)

Activated neutrophils (PMNs), the ROS/RNS released by PMNs and the derived inflammatory processes are involved in the pathogenesis and progression of human inflammatory airway diseases. Similar diseases are also present in horses which suffer from recurrent airway obstruction (RAO), exercise-induced pulmonary haemorrhage (EIPH) and inflammatory airway diseases (IAD). Hyaluronic acid (HA) plays numerous roles in modulating inflammatory processes. The aim of this study was to examine whether a preparation of HA (MW 900 000 Da) interferes with ROS/RNS during the course of equine PMN respiratory bursts, and to establish the lowest concentration at which it still has antioxidant activity by means of luminol-amplified chemiluminescence (LACL). Electron paramagnetic resonance (EPR) spectroscopy was also used to investigate the direct antiradical activity of HA. The hydroxyl radical was significantly scavenged in a concentration-dependent manner at HA concentrations ranging from 2.5 to 0.16 mg/mL. Superoxide anion, Tempol radical and the ABTS(•+) were significantly inhibited at concentrations ranging from 2.5 to 0.62 mg/mL. The LACL of stimulated equine neutrophils showed that HA induced a statistically significant concentration-effect reduction from 5 mg/mL to 1.25 mg/mL. These findings were confirmed also when l-Arg was added to investigate the inhibition of the resulting peroxynitrite anion. Our findings indicate that, in addition to the human use, HA can also be used to antagonize the oxidative stress generated by free radicals in horses peripheral blood mononuclear cells (PBMCs). In order to achieve therapeutic concentrations, a direct aerosol administration to horses with horse respiratory diseases can be considered, as this route of application is also recommended in human medicine. PMID:25066541

Braga, P C; Dal Sasso, M; Lattuada, N; Greco, V; Sibilia, V; Zucca, E; Stucchi, L; Ferro, E; Ferrucci, F

2015-02-01

354

Free radical scavenging abilities of polypeptide from Chlamys farreri  

Science.gov (United States)

We investigated the radical scavenging effect and antioxidation property of polypeptide extracted from Chlamys farreri (PCF) in vitro using chemiluminescence and electron spin resonance (ESR) methods. We examined the scavenging effects of PCF on superoxide anions (O{2/-}), hydroxyl radicals (OH·), peroxynitrite (ONOO-) and the inhibiting capacity of PCF on peroxidation of linoleic acid. Our experiment suggested that PCF could scavenge oxygen free radicals including superoxide anions (O{2/-}) (IC50=0.3 mg/ml), hydroxyl radicals (OH·) (IC50=0.2 ?g/ml) generated from the reaction systems and effectively inhibit the oxidative activity of ONOO- (IC50=0.2 mg/ml). At 1.25 mg/ml of PCF, the inhibition ratio on lipid peroxidation of linoleic acid was 43%. The scavenging effect of PCF on O{2/-}, OH· and ONOO- free radicals were stronger than those of vitamin C but less on lipid peroxidation of linoleic acid. Thus PCF could scavenge free radicals and inhibit the peroxidation of linoleic acid in vitro. It is an antioxidant from marine products and potential for industrial production in future.

Han, Zhiwu; Chu, Xiao; Liu, Chengjuan; Wang, Yuejun; Mi, Sun; Wang, Chunbo

2006-09-01

355

gamma-secretase inhibition promotes cell death, Noxa upregulation and sensitization to BH3 mimetic ABT-737 in human breast cancer cells.  

OpenAIRE

ABSTRACT: INTRODUCTION: Inappropriate Notch signalling, downstream of -secretase activity, is understood to have tumor-promoting function and to be associated with poor outcome in cancer, of the breast in particular. The molecular basis of anti-tumoral effects of its inhibitors, remain however poorly characterized. Moreover, the effects of their combination with the pro-apoptototic pharmacological inhibitor of Bcl2/BclxL, ABT-737, have never been evaluated. In this study, we thus specifically...

Se?veno, Ce?line; Loussouarn, Delphine; Bre?chet, Sophie; Campone, Mario; Juin, Philippe; Barille?-nion, Sophie

2012-01-01

356

Counter radicalization development assistance  

OpenAIRE

The paper reviews current research and practice and recommends strategies for development agencies working in the Arab and Muslim world. It builds on the basic assumption that the realization of the Millennium Development Goals will be vital to reduce support for terrorism in the long term. Within this overall framework, emphasis is placed on particular programs that could be specifically applied to counter radicalization.

Hippel, Karin

2006-01-01

357

ABT-737 and/or folate reverse the PDGF-induced alterations in the mitochondrial apoptotic pathway in low-grade glioma patients.  

Science.gov (United States)

Elevated activation of the platelet-derived growth factor (PDGF) pathway, apoptosis evasion phenotype, and global DNA hypomethylation are hallmarks frequently observed in cancers, such as in low-grade glioma (LGG). However, the orchestration of these malignant functions is not fully elucidated in LGG. Our study reveals that the co-presence of these hallmarks in the same LGG is frequent and confers poor prognosis in patients with LGG. Our data also indicate that the apoptosis evasion phenotype of these cells harboring a hypomethylation-induced activation of the PDGF pathway is associated with a hypomethylation of the bcl-xl and bcl-w genes and the phosphorylation and/or downregulation of three major pro-apoptotic BH3-only proteins: PUMA, Bad, and Bim. Consistent with this, we demonstrate that the use of folate, a DNA-methylating agent, promotes the reprogramming of the sensitivity of glioma cells to ABT-737/etoposide-induced apoptosis and reduces the dose of ABT-737 required to promote etoposide-induced apoptosis. This work supports the idea that the inclusion of folate and/or ABT-737 could be a promising adjuvant in the design of anti-glioma therapeutic protocols in clinical studies. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s13148-011-0035-5) contains supplementary material, which is available to authorized users. PMID:21949549

Debien, Emilie; Hervouet, Eric; Gautier, Fabien; Juin, Philippe; Vallette, Francois M; Cartron, Pierre-Francois

2011-08-01

358

Matrix isolation of free radicals from carbohydrates  

International Nuclear Information System (INIS)

Photolytically produced H radical-atoms in 6 mol dm-3 H2SO4/H2O glasses trapped at 77 K react upon annealing to 130 K with dissolved carbohydrates to form carbon-located free radicals by abstraction of carbon-bound protons. Analysis of electron spin resonance (e.s.r.) spectra at various annealing stages from ?- and ?-D-glucose together with 6,6-d2-D-glucose, 6-deoxy-D-glucose, 2-deoxy-D-glucose, glucose-1-phosphate, D-xylose, D-allose and D-mannosse indicates radical formation at all possible carbon sites with a strong preference for Cl and a somewhat enhanced contribution of C4 over the statistical expectation. The corresponding component spectra are analysed either by spectra isolation or simulation and their parameters are given. Intramolecular radical transformation at temperatures of 140-160 K is explained by acid-catalysed H2O-elimination. The findings are discussed in relation to the radiation-chemistry of aqueous glucose solutions. The authors thus show that the system of photolysed Fe2+ in acidic glasses at low temperatures containing 10 mmol dm-3 carbohydrate is suitable for studying H(D radical)-reactions by means of e.s.r. spectroscopy. Unlike previously used glasses containing carbohydrates, contributions of oxidation and reduction by direct effects or mixtures of direct and indirect effects and phase-effects due to incomplete glass formation are avoided. (author)glass formation are avoided. (author)

359

Tyrosyl Radicals in Dehaloperoxidase  

Science.gov (United States)

Dehaloperoxidase (DHP) from Amphitrite ornata, having been shown to catalyze the hydrogen peroxide-dependent oxidation of trihalophenols to dihaloquinones, is the first oxygen binding globin that possesses a biologically relevant peroxidase activity. The catalytically competent species in DHP appears to be Compound ES, a reactive intermediate that contains both a ferryl heme and a tyrosyl radical. By simulating the EPR spectra of DHP activated by H2O2, Thompson et al. (Thompson, M. K., Franzen, S., Ghiladi, R. A., Reeder, B. J., and Svistunenko, D. A. (2010) J. Am. Chem. Soc. 132, 17501–17510) proposed that two different radicals, depending on the pH, are formed, one located on either Tyr-34 or Tyr-28 and the other on Tyr-38. To provide additional support for these simulation-based assignments and to deduce the role(s) that tyrosyl radicals play in DHP, stopped-flow UV-visible and rapid-freeze-quench EPR spectroscopic methods were employed to study radical formation in DHP when three tyrosine residues, Tyr-28, Tyr-34, and Tyr-38, were replaced either individually or in combination with phenylalanines. The results indicate that radicals form on all three tyrosines in DHP. Evidence for the formation of DHP Compound I in several tyrosine mutants was obtained. Variants that formed Compound I showed an increase in the catalytic rate for substrate oxidation but also an increase in heme bleaching, suggesting that the tyrosines are necessary for protecting the enzyme from oxidizing itself. This protective role of tyrosines is likely an evolutionary adaptation allowing DHP to avoid self-inflicted damage in the oxidative environment. PMID:24100039

Dumarieh, Rania; D'Antonio, Jennifer; Deliz-Liang, Alexandria; Smirnova, Tatyana; Svistunenko, Dimitri A.; Ghiladi, Reza A.

2013-01-01

360

Impacts of an unknown daytime nitrous acid source on its daytime concentration and budget, as well as those of hydroxyl, hydroperoxyl, and organic peroxy radicals, in the coastal regions of China  

Science.gov (United States)

Many field experiments have found high nitrous acid (HONO) mixing ratios in both urban and rural areas during daytime, but these high daytime HONO mixing ratios cannot be explained well by gas-phase production, suggesting that an unknown daytime HONO source (Punknown) could exist. The formula Punknown ? 19.60 × NO2 × J(NO2) was obtained using observed data from 13 field experiments across the globe. The additional HONO sources (i.e. the Punknown, HONO emissions, and nighttime hydrolysis conversion of nitrogen dioxide (NO2) on aerosols) were coupled into the WRF-Chem model (Weather Research and Forecasting model coupled with Chemistry) to assess the Punknown impacts on the concentrations and budgets of HONO and peroxy (hydroxyl, hydroperoxyl, and organic peroxy) radicals (ROx) (= OH + HO2 + RO2) in the coastal regions of China. Results indicated that the additional HONO sources produced a significant improvement in HONO and OH simulations, particularly in the daytime. Elevated daytime-mean Punknown values were found in the coastal regions of China, with a maximum of 2.5 ppb h-1 in the Beijing-Tianjin-Hebei region. The Punknown produced a 60-250% increase of OH, HO2 and RO2 near the ground in the major cities of the coastal regions of China, and a 5-48% increase of OH, HO2 and RO2 in the daytime meridional-mean mixing ratios within 1000 m above the ground. When the additional HONO sources were included, the photolysis of HONO was dominated in the OH production rate in Beijing, Shanghai and Guangzhou before 10:00 LST with a maximum of 10.01 [7.26 due to the Punknown] ppb h-1 in Beijing, whereas the reaction of HO2 + NO (nitric oxide) was dominated after 10:00 LST with a maximum of 9.38 [7.23] ppb h-1 in Beijing. The whole ROx cycle was accelerated by the additional HONO sources, especially the Punknown. The OH production rate was enhanced by 0.67 [0.64] to 4.32 [3.86] ppb h-1 via the reaction of HO2 + NO, and by 0.85 [0.69] to 4.11 [3.61] ppb h-1 via the photolysis of HONO, and the OH loss rate was enhanced by 0.58 [0.55] to 2.03 [1.92] ppb h-1 via the reaction of OH + NO2 and by 0.31 [0.28] to 1.78 [1.64] ppb h-1 via the reaction of OH + CO (carbon monoxide) in Beijing, Shanghai and Guangzhou. Similarly, the additional HONO sources produced an increase of 0.31 [0.28] to 1.78 [1.64] ppb h-1 via the reaction of OH + CO and 0.10 [0.09] to 0.63 [0.59] ppb h-1 via the reaction of CH3O2 (methylperoxy radical) + NO in the HO2 production rate, and 0.67 [0.61] to 4.32 [4.27] ppb h-1 via the reaction of HO2 + NO in the HO2 loss rate in Beijing, Shanghai and Guangzhou. The above results suggest that the Punknown considerably enhanced the ROx concentrations and accelerated ROx cycles in the coastal regions of China, and could produce significant increases in concentrations of inorganic aerosols and secondary organic aerosols and further aggravate haze events in these regions.

Tang, Y.; An, J.; Wang, F.; Li, Y.; Qu, Y.; Chen, Y.; Lin, J.

2015-01-01

361

Impacts of an unknown daytime nitrous acid source on its daytime concentration and budget, as well as those of hydroxyl, hydroperoxyl, and organic peroxy radicals, in the coastal regions of China  

Directory of Open Access Journals (Sweden)

Full Text Available Many field experiments have found high nitrous acid (HONO mixing ratios in both urban and rural areas during daytime, but these high daytime HONO mixing ratios cannot be explained well by gas-phase production, suggesting that an unknown daytime HONO source (Punknown could exist. The formula Punknown ≈ 19.60 × NO2 × J(NO2 was obtained using observed data from 13 field experiments across the globe. The additional HONO sources (i.e. the Punknown, HONO emissions, and nighttime hydrolysis conversion of nitrogen dioxide (NO2 on aerosols were coupled into the WRF-Chem model (Weather Research and Forecasting model coupled with Chemistry to assess the Punknown impacts on the concentrations and budgets of HONO and peroxy (hydroxyl, hydroperoxyl, and organic peroxy radicals (ROx (= OH + HO2 + RO2 in the coastal regions of China. Results indicated that the additional HONO sources produced a significant improvement in HONO and OH simulations, particularly in the daytime. Elevated daytime-mean Punknown values were found in the coastal regions of China, with a maximum of 2.5 ppb h?1 in the Beijing–Tianjin–Hebei region. The Punknown produced a 60–250% increase of OH, HO2 and RO2 near the ground in the major cities of the coastal regions of China, and a 5–48% increase of OH, HO2 and RO2 in the daytime meridional-mean mixing ratios within 1000 m above the ground. When the additional HONO sources were included, the photolysis of HONO was dominated in the OH production rate in Beijing, Shanghai and Guangzhou before 10:00 LST with a maximum of 10.01 [7.26 due to the Punknown] ppb h?1 in Beijing, whereas the reaction of HO2 + NO (nitric oxide was dominated after 10:00 LST with a maximum of 9.38 [7.23] ppb h?1 in Beijing. The whole ROx cycle was accelerated by the additional HONO sources, especially the Punknown. The OH production rate was enhanced by 0.67 [0.64] to 4.32 [3.86] ppb h?1 via the reaction of HO2 + NO, and by 0.85 [0.69] to 4.11 [3.61] ppb h?1 via the photolysis of HONO, and the OH loss rate was enhanced by 0.58 [0.55] to 2.03 [1.92] ppb h?1 via the reaction of OH + NO2 and by 0.31 [0.28] to 1.78 [1.64] ppb h?1 via the reaction of OH + CO (carbon monoxide in Beijing, Shanghai and Guangzhou. Similarly, the additional HONO sources produced an increase of 0.31 [0.28] to 1.78 [1.64] ppb h?1 via the reaction of OH + CO and 0.10 [0.09] to 0.63 [0.59] ppb h?1 via the reaction of CH3O2 (methylperoxy radical + NO in the HO2 production rate, and 0.67 [0.61] to 4.32 [4.27] ppb h?1 via the reaction of HO2 + NO in the HO2 loss rate in Beijing, Shanghai and Guangzhou. The above results suggest that the Punknown considerably enhanced the ROx concentrations and accelerated ROx cycles in the coastal regions of China, and could produce significant increases in concentrations of inorganic aerosols and secondary organic aerosols and further aggravate haze events in these regions.

Y. Tang

2015-01-01

362

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 corresponding standards. Quantitative estimation of antioxidant phytochemicals, such as phenols, flavonoids and proanthocyanidins were also done in both species of Cleome. The results revealed that the phytochemicals content was greater in C. viscosa when compared to C. burmanni.

Lakshmi S. Pillai* and Bindu R. Nair

2013-02-01

363

Phenolic antioxidant scavenging of myosin radicals generated by hypervalent myoglobin.  

Science.gov (United States)

The scavenging activity of extracts of green tea (GTE), white grape (WGE), and rosemary (RE), all plant material with high phenolic content, and of the phenolic compounds 4-methylcatechol (4-MC), (+)-catechin, and carnosic acid toward long-lived myosin radicals generated by reaction with H2O2-activated myoglobin at room temperature (pH 7.5, I=1.0) was investigated by freeze-quench ESR spectroscopy. Myosin radicals were generated by incubating 16 ?M myosin, 800 ?M metmyoglobin, and 800 ?M H2O2 for 10 min, and the phenolic extracts were subsequently added (1% (w/w) phenolic compounds relative to myosin). GTE was able to scavenge myosin radicals and reduce the radical intensity by 65%. Furthermore, a low concentration of 4-MC (33 ?M) was found to increase the radical concentration when added to the myosin radicals, whereas a higher concentration of 4-MC and catechin (330 ?M) was found to scavenge myosin radicals and reduce the overall radical concentration by ?65%. PMID:23163579

Jongberg, Sisse; Lund, Marianne N; Østdal, Henrik; Skibsted, Leif H

2012-12-01

364

Toward Radicalizing Community Service Learning  

Science.gov (United States)

This article advocates a radicalized theoretical construction of community service learning. To accomplish this radicalization, I initially take up a discussion of traditional understandings of CSL rooted in pragmatic/progressive thought. I then suggest that this traditional structural foundation can be radicalized by incorporating Deborah…

Sheffield, Eric C.

2015-01-01

365

Atropisomerism of the Asn ? Radicals Revealed by Ramachandran Surface Topology  

DEFF Research Database (Denmark)

C radicals are typically trigonal planar and thus achiral, regardless of whether they originate from a chiral or an achiral C-atom (e.g., C-H + (•)OH ? C• + H2O). Oxidative stress could initiate radical formation in proteins when, for example, the H-atom is abstracted from the C?-carbon of an amino acid residue. Electronic structure calculations show that such a radical remains achiral when formed from the achiral Gly, or the chiral but small Ala residues. However, when longer side-chain containing proteogenic amino acid residues are studied (e.g., Asn), they provide radicals of axis chirality, which in turn leads to atropisomerism observed for the first time for peptides. The two enantiomeric extended backbone structures, •?L and •?D, interconvert via a pair of enantiotopic reaction paths, monitored on a 4D Ramachandran surface, with two distinct transition states of very different Gibbs-free energies: 37.4 and 67.7 kJ/mol, respectively. This discovery requires the reassessment of our understanding on radical formation and their conformational and stereochemical behavior. Furthermore, the atropisomerism of proteogenic amino acid residues should affect our understanding on radicals in biological systems and, thus, reframes the role of the D-residues as markers of molecular aging.

Gerlei, Klára Z.; Jákli, Imre

2013-01-01

366

In vitro free radical scavenging activity of platinum nanoparticles  

Science.gov (United States)

A polyacrylic acid (PAA)-protected platinum nanoparticle species (PAA-Pt) was prepared by alcohol reduction of hexachloroplatinate. The PAA-Pt nanoparticles were well dispersed and homogeneous in size with an average diameter of 2.0 ± 0.4 nm (n = 200). We used electron spin resonance to quantify the residual peroxyl radical (\\mathrm {AOO}^{\\bullet } ) generated from 2,2-azobis (2-aminopropane) dihydrochloride (AAPH) by thermal decomposition in the presence of O2 and a spectrophotometric method to quantify the residual 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. PAA-Pt scavenged these two radicals in a dose-dependent manner. Platinum was the functional component. PAA-Pt reduced the rate of oxygen consumption required for linoleic acid peroxidation initiated by \\mathrm {AOO}^{\\bullet } generated from AAPH, indicating inhibition of the propagation of linolate peroxidation. A thiobarbituric acid test also revealed dose-dependent inhibition of the linolate peroxidation by PAA-Pt. Fifty micromolar platinum, as PAA-Pt, completely quenched 250 µM DPPH radical for 5 min. Even when twice diluted in half, the PAA-Pt still quenched 100% of the 250 µM DPPH radical. The scavenging activity of PAA-Pt is durable. These observations suggest that PAA-Pt is an efficient scavenger of free radicals.

Watanabe, Aki; Kajita, Masashi; Kim, Juewon; Kanayama, Atsuhiro; Takahashi, Kyoko; Mashino, Tadahiko; Miyamoto, Yusei

2009-11-01

367

In vitro free radical scavenging activity of platinum nanoparticles  

Energy Technology Data Exchange (ETDEWEB)

A polyacrylic acid (PAA)-protected platinum nanoparticle species (PAA-Pt) was prepared by alcohol reduction of hexachloroplatinate. The PAA-Pt nanoparticles were well dispersed and homogeneous in size with an average diameter of 2.0 {+-} 0.4 nm (n = 200). We used electron spin resonance to quantify the residual peroxyl radical AOO. generated from 2,2-azobis (2-aminopropane) dihydrochloride (AAPH) by thermal decomposition in the presence of O{sub 2} and a spectrophotometric method to quantify the residual 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. PAA-Pt scavenged these two radicals in a dose-dependent manner. Platinum was the functional component. PAA-Pt reduced the rate of oxygen consumption required for linoleic acid peroxidation initiated by AOO. generated from AAPH, indicating inhibition of the propagation of linolate peroxidation. A thiobarbituric acid test also revealed dose-dependent inhibition of the linolate peroxidation by PAA-Pt. Fifty micromolar platinum, as PAA-Pt, completely quenched 250 {mu}M DPPH radical for 5 min. Even when twice diluted in half, the PAA-Pt still quenched 100% of the 250 {mu}M DPPH radical. The scavenging activity of PAA-Pt is durable. These observations suggest that PAA-Pt is an efficient scavenger of free radicals.

Watanabe, Aki; Kajita, Masashi; Kim, Juewon; Kanayama, Atsuhiro; Miyamoto, Yusei [Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Bioscience Building 402, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8562 (Japan); Takahashi, Kyoko; Mashino, Tadahiko, E-mail: yusei74@k.u-tokyo.ac.j [Department of Pharmaceutical Sciences, Faculty of Pharmacy, Keio University, 1-5-30 Shibakoen, Minato, Tokyo 105-8512 (Japan)

2009-11-11

368

Synthesis, molecular modeling and biological evaluation of novel 2-allyl amino 4-methyl sulfanyl butyric acid as ?-amylase and ?-glucosidase inhibitor  

Science.gov (United States)

In the present study 2-allyl amino 4-methyl sulfanyl butyric acid (AMSB) was synthesized in good yield. AMSB was characterized by Fourier transforms infrared spectroscopy (FTIR), Nuclear magnetic resonance (NMR) (1H and 13C) and Liquid chromatography mass spectrometry (LCMS). The radical scavenging activity and reducing power assay of AMSB was assessed using 1-1-diphenyl 2-picryl hydrazyl (DPPH), 2,2?-azino-bis (3-ethyl benzothiazoline-6-sulfonic acid) (ABTS) and ferric ion reducing antioxidant power assay (FRAP) and was found to be 44.1, 34.71 and 41.7 ?g/ml respectively. The compound showed effective inhibition against ?-amylase and ?-glucosidase. AMSB was identified to be a reversible mixed noncompetitive inhibitor of ?-amylase and ?-glucosidase. The molecular docking study was carried out to evaluate the specific groove binding properties and affords valuable information of AMSB binding mode in the active site of ?-glucosidase the study may lead to the which leads to the rational design of new class of antidiabetic drugs targeting ?-glucosidase based on AMSB in near future.

Balan, Kannan; Perumal, Perumal; Sundarabaalaji, Narayanan; Palvannan, Thayumanavan

2015-02-01

369

Free radicals formed under UV-irradiation on lipids of biological membranes  

International Nuclear Information System (INIS)

The formation of free radicals under UV irradiation in egg phosphatidylcholine, synthetic phosphatidylcholines and their analogs, as well as in model compounds was studied. Under UV irradiation of the saturated fatty acids, the -CH2CH2 radicals are accumulated on account of -CH2CH2-COOH bond breaking. The CH3, -OCH2, HCO radicals are formed in aminoalcohols on account of -OCH2-CH2N+ (CH3) and -CH2-N+ (CH3)3 bond breaking. It has been found that in natural and synthetic phospholipides the radicals are formed in the process of photochemical reactions in ester and amine groups. The mechanism of radical formation is discussed

370

Free radical scavenging action of baicalein.  

Science.gov (United States)

TJ-960 is a Japanese Kampo (traditional herbal) medicine used for the treatment of epilepsy. It's a crude drug, an extract of nine herbs, and consists of many known and unknown components. Among the known components of TJ-960, we found that 5,6,7-trihydroxy-2-phenyl-4H-1-benzopyran-4-one (baicalein) might be the most potent scavenger for radicals. In the present study, we examined in vitro the radical scavenging effect of baicalein in detail using electron spin resonance spectrometry. Furthermore, we examined in vivo its effect on the thiobarbituric acid-reactive substances (TBARS) levels and superoxide dismutase in the brain of rats with FeCl3-induced epilepsy and on hippocampal delayed neuronal death in gerbils with transient ischemia. In in vitro experiments, baicalein quenched in a dose-dependent manner 1,1-diphenyl-2-picrylhydrazyl, superoxide, and hydroxyl radicals. In the FeCl3-induced epileptic model, baicalein suppressed the increase in the TBARS level at the FeCl3-injected site. Baicalein also inhibited hippocampal neuronal death induced by 5 min of cerebral ischemia in gerbils. Hence the present study suggested that baicalein is one of the active components in TJ-960, which partially contributes to the antiepileptic and neuronal protective effects of TJ-960, and that the mechanism of its pharmacological action is based upon radical quenching and antioxidative effects. PMID:8215413

Hamada, H; Hiramatsu, M; Edamatsu, R; Mori, A

1993-10-01

371

Gangs, Terrorism, and Radicalization  

OpenAIRE

What can street gangs tell us about radicalization and extremist groups? At first glance, these two groups seem to push the boundaries of comparison. In this article, we examine the important similarities and differences across criminal, deviant, and extremist groups. Drawing from research on street gangs, this article explores issues such as levels of explanation,organizational structure, group process, and the increasingly important role of technology and the Internet in the context of radi...

Scott Decker; David Pyrooz

2011-01-01

372

Probability and radical behaviorism  

OpenAIRE

The concept of probability appears to be very important in the radical behaviorism of Skinner. Yet, it seems that this probability has not been accurately defined and is still ambiguous. I give a strict, relative frequency interpretation of probability and its applicability to the data from the science of behavior as supplied by cumulative records. Two examples of stochastic processes are given that may model the data from cumulative records that result under conditions of continuous reinforc...

Espinosa, James M.

1992-01-01

373

Women and radicalization  

OpenAIRE

The paper focuses on women and radicalization within the context of Muslim societies (majority, minority, and half Muslim) societies and groups, mainly in Asia and Africa. The basic argument advanced in this paper is that Islamic feminism with its gender-egalitarian discourse and practices has a major role to play in the empowerment of Muslim women—and of men and society as a whole—and should be brought to bear in devising policy, strategy, and tools.

Badran, Margot

2006-01-01

374

[Radical prostatectomy - pro robotic].  

Science.gov (United States)

Anatomical radical prostatectomy was introduced in the early 1980s by Walsh and Donker. Elucidation of key anatomical structures led to a significant reduction in the morbidity of this procedure. The strive to achieve similar oncological and functional results to this gold standard open procedure but with further reduction of morbidity through a minimally invasive access led to the establishment of laparoscopic prostatectomy. However, this procedure is complex and difficult and is associated with a long learning curve. The technical advantages of robotically assisted surgery coupled with the intuitive handling of the device led to increased precision and shortening of the learning curve. These main advantages, together with a massive internet presence and aggressive marketing, have resulted in a rapid dissemination of robotic radical prostatectomy and an increasing patient demand. However, superiority of robotic radical prostatectomy in comparison to the other surgical therapeutic options has not yet been proven on a scientific basis. Currently robotic-assisted surgery is an established technique and future technical improvements will certainly further define its role in urological surgery. In the end this technical innovation will have to be balanced against the very high purchase and running costs, which remain the main limitation of this technology. PMID:22526183

Gillitzer, R

2012-05-01

375

[Radical cystectomy - pro laparoscopic].  

Science.gov (United States)

Although the technical feasibility of laparoscopic radical cystectomy (LRC) has been proven and the procedure has been accepted in the EAU guidelines 2011 as a valid alternative, its actual position has to be determined. On the one hand the advantages of LRC (less blood loss, lower transfusion rates, shorter analgesia time) have been proven in retrospective studies; however, the technical difficulties of purely laparoscopic urinary diversion result in very long operating times and in cases of a laparoscopic-assisted creation of a neobladder, the question of the advantage of this approach remains doubtful. Despite case reports of port metastases and peritoneal carcinosis following laparoscopic and robot-assisted radical cystectomy, there is no difference in terms of oncological long-term data (up to 10 years) between laparoscopy and open surgery performed at centres of excellence. Evidently, the curative options for the patients do not depend on the type of surgery (open versus minimally invasive) but on the efficacy of adjuvant treatment strategies (polychemotherapy). Currently it is believed that LRC should be considered for patients with low risk of progression (pT1-2). The final position of laparoscopic radical cystectomy can only be evaluated in a multicentric randomized controlled trial. PMID:22532364

Rassweiler, J; Godin, K; Goezen, A S; Kusche, D; Chlosta, P; Gaboardi, F; Abbou, C C; van Velthoven, R

2012-05-01

376

Acid-base equilibria involved in secondary reactions following the 4-carboxybenzophenone sensitized photooxidation of methionylglycine in aqueous solution. Spectral and time resolution of the decaying (S...N){sup +} radical cation  

Energy Technology Data Exchange (ETDEWEB)

A radical cation with an intramolecular sulfur-nitrogen bond was formed in the photoinitiated transfer of an electron from the sulfur atom of the dipeptide Met-Gly to 4-carboxybenzophenone in its triplet state. The sulfur-nitrogen coupling involved two-center, three-electron bonds. The kinetics of the reactions of these radical cations, which were initiated by a laser flash, were followed over time. The principal method of implementing the spectral resolutions was accomplished through a multiple linear regression technique. This spectral analysis was repeated for numerous time windows during the lifetime of the transients` decays. The resulting concentrations of the transients were consistent with an independent factor analysis. It was found that the decay of the radical cations was multiexponential and that the decay varied with pH. A simplified reaction scheme was proposed whereby the absorbing radical cations can alternatively decay by an irreversible channel or react reversibly with OH{sup -}. Rate constants for the three elementary reactions of this scheme were determined from an analysis of the decay of the concentration of the radical cations. In addition, the equilibrium constant for the reversible reaction was determined by two separate procedures. 35 refs., 7 figs., 2 tabs.

Hug, G.L. [Univ. of Notre Dame, IN (United States); Marciniak, B. [Univ. of Notre Dame, IN (United States)]|[A. Mickiewicz Univ., Poznan (Poland); Bobrowski, K. [Univ. of Notre Dame, IN (United States)]|[Inst. of Biochemistry and Biophysics, Warsaw (Poland)]|[Inst. of Nuclear Chemistry and Technology, Warsaw (Poland)

1996-09-05

377

Cytotoxic and Radical Scavenging Nor-Dammarane Triterpenoids from Viburnum mongolicum  

Directory of Open Access Journals (Sweden)

Full Text Available The ethanol extract of the whole plants of Viburnum mongolicum afforded six new nor-dammarane triterpenoids: 3?,12?-dihydroxy-25,26,27-trinordammara-22-en -24,20-olide (1, 3?,12?-dihydroxy-24?-methoxy-25,26,27-trinordammara-20,24-epoxy (2, 3?-O-acetyl-12?-hydroxy-23,24,25,26,27-hexanordammarane-20-one (3, 12?-O- acetyl-15?-hydroxy-17?-methoxy-3-oxo-20,21,22-23,24,25,26,27-octanordammanrane (4, 12?-O-acetyl-15?,17?-dihydroxy-3-oxo-20,21,22-23,24,25,26,27-octanordammanrane (5, and 12?,15?-dihydroxy-3-oxo-17-en-20,21,22-23,24,25,26,27-octanordammanrane (6, together with two known nor-dammarane triterpenoids, 12?-hydroxy-3-oxo-24?-methoxy- 25,26,27-trinordammara-20,24-epoxy (7 and 3?,12?-dihydroxy-23,24,25,26,27- hexanordammarane-20-one (8. The structures of the isolated compounds were established based on 1D and 2D (1H-1H COSY, HMQC, and HMBC NMR spectroscopy, in addition to high resolution mass spectrometry. The isolated compounds were tested in vitro for cytotoxic potential against seven tumor cell lines and radical scavenging activities. Compounds 4–6 exhibited significant cytotoxic activities against all tested tumor cell lines and radical scavenging activities against ABTS·+ radicals comparable with the standard drug Trolox.

Wei Wang

2013-01-01

378

Antimutagenic and free radical scavenger effects of leaf extracts from Accacia salicina  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Three extracts were prepared from the leaves of Accacia salicina; ethyl acetate (EA, chloroform (Chl and petroleum ether (PE extracts and was designed to examine antimutagenic, antioxidant potenty and oxidative DNA damage protecting activity. Methods Antioxidant activity of A. salicina extracts was determined by the ability of each extract to protect against plasmid DNA strand scission induced by hydroxyl radicals. An assay for the ability of these extracts to prevent mutations induced by various oxidants in Salmonella typhimurium TA102 and TA 104 strains was conducted. In addition, nonenzymatic methods were employed to evaluate anti-oxidative effects of tested extracts. Results These extracts from leaf parts of A. salicina showed no mutagenicity either with or without the metabolic enzyme preparation (S9. The highest protections against methylmethanesulfonate induced mutagenicity were observed with all extracts and especially chloroform extract. This extract exhibited the highest inhibitiory level of the Ames response induced by the indirect mutagen 2- aminoanthracene. All extracts exhibited the highest ability to protect plasmid DNA against hydroxyl radicals induced DNA damages. The ethyl acetate (EA and chloroform (Chl extracts showed with high TEAC values radical of 0.95 and 0.81 mM respectively, against the ABTS.+. Conclusion The present study revealed the antimutagenic and antioxidant potenty of plant extract from Accacia salicina leaves.

Boubaker Jihed

2011-12-01

379

Vertically resolved measurements of nighttime radical reservoirs in Los Angeles and their contribution to the urban radical budget.  

Science.gov (United States)

Photolabile nighttime radical reservoirs, such as nitrous acid (HONO) and nitryl chloride (ClNO(2)), contribute to the oxidizing potential of the atmosphere, particularly in early morning. We present the first vertically resolved measurements of ClNO(2), together with vertically resolved measurements of HONO. These measurements were acquired during the California Nexus (CalNex) campaign in the Los Angeles basin in spring 2010. Average profiles of ClNO(2) exhibited no significant dependence on height within the boundary layer and residual layer, although individual vertical profiles did show variability. By contrast, nitrous acid was strongly enhanced near the ground surface with much smaller concentrations aloft. These observations are consistent with a ClNO(2) source from aerosol uptake of N(2)O(5) throughout the boundary layer and a HONO source from dry deposition of NO(2) to the ground surface and subsequent chemical conversion. At ground level, daytime radical formation calculated from nighttime-accumulated HONO and ClNO(2) was approximately equal. Incorporating the different vertical distributions by integrating through the boundary and residual layers demonstrated that nighttime-accumulated ClNO(2) produced nine times as many radicals as nighttime-accumulated HONO. A comprehensive radical budget at ground level demonstrated that nighttime radical reservoirs accounted for 8% of total radicals formed and that they were the dominant radical source between sunrise and 09:00 Pacific daylight time (PDT). These data show that vertical gradients of radical precursors should be taken into account in radical budgets, particularly with respect to HONO. PMID:23013316

Young, Cora J; Washenfelder, Rebecca A; Roberts, James M; Mielke, Levi H; Osthoff, Hans D; Tsai, Catalina; Pikelnaya, Olga; Stutz, Jochen; Veres, Patrick R; Cochran, Anthony K; VandenBoer, Trevor C; Flynn, James; Grossberg, Nicole; Haman, Christine L; Lefer, Barry; Stark, Harald; Graus, Martin; de Gouw, Joost; Gilman, Jessica B; Kuster, William C; Brown, Steven S

2012-10-16

380

ABT: American Ballet Theatre  

Science.gov (United States)

The American Ballet Theatre's homepage offers information about performances (past and present), Dancer Bios, and a Photo Gallery of black and white photographs of performances, staged poses, and behind-the-scenes shots.

381

ABT Ballet Dictionary  

Science.gov (United States)

How many times have you heard or used the terms "pirouette" or "pas de deux" without really knowing what they meant? A number of words related to ballet have made their way into common usage, although many people may not know what they really mean or what they would look like if performed by a trained dancer. The American Ballet Theatre has created this Online Ballet Dictionary of 170 terms with assistance from its own dancers who were asked to "show us how it is supposed to be done." The resulting site combines Quicktime movies of dancers demonstrating steps with terms drawn from the Technical Manual and Dictionary of Classical Ballet. While not every term is accompanied by a movie, each term includes a definition and pronunciation guide, as well as occasional cross references to other terms in the dictionary.