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

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

C ROJO

2009-01-01

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

Scientific Electronic Library Online (English)

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

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

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Comprehensive two-dimensional liquid chromatography coupled to the ABTS radical scavenging assay: a powerful method for the analysis of phenolic antioxidants.  

Science.gov (United States)

The on-line combination of comprehensive two-dimensional liquid chromatography (LC?×?LC) with the 2,2'-azino-bis(3-ethylbenzothiazoline)-6 sulphonic acid (ABTS) radical scavenging assay was investigated as a powerful method to determine the free radical scavenging activities of individual phenolics in natural products. The combination of hydrophilic interaction chromatography (HILIC) separation according to polarity and reversed-phase liquid chromatography (RP-LC) separation according to hydrophobicity is shown to provide much higher resolving power than one-dimensional separations, which, combined with on-line ABTS detection, allows the detailed characterisation of antioxidants in complex samples. Careful optimisation of the ABTS reaction conditions was required to maintain the chromatographic separation in the antioxidant detection process. Both on-line and off-line HILIC?×?RP-LC-ABTS methods were developed, with the former offering higher throughput and the latter higher resolution. Even for the fast analyses used in the second dimension of on-line HILIC?×?RP-LC, good performance for the ABTS assay was obtained. The combination of LC?×?LC separation with an on-line radical scavenging assay increases the likelihood of identifying individual radical scavenging species compared to conventional LC-ABTS assays. The applicability of the approach was demonstrated for cocoa, red grape seed and green tea phenolics. PMID:24817360

Kalili, Kathithileni M; De Smet, Seppe; van Hoeylandt, Tim; Lynen, Frédéric; de Villiers, André

2014-07-01

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

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

Ivona Jasprica

2007-05-01

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Histamine H3 receptor antagonism by ABT-239 attenuates kainic acid induced excitotoxicity in mice.  

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The multifaceted pathogenesis of temporal lobe epilepsy (TLE) offers a number of adjunctive therapeutic prospects. One such therapeutic strategy could be targeting H3 receptor (H3R) by selective H3R antagonists which are perceived to have antiepileptic and neuroprotective potential. Kainic acid (KA) induced seizure, a reliable model of TLE, triggers epileptogenic events resulting from initial neuronal death and ensuing recurring seizures. The present study aimed to determine whether pre-treatment with ABT-239, a novel H3R antagonist, and its combinations with sodium valproate (SVP) and TDZD-8 (glycogen synthase kinase-3? (GSK3?) inhibitor) can prevent the excitotoxic events in mice exposed to KA (10 mg/kg i.p.). ABT-239 (1 and 3 mg/kg i.p.) significantly attenuated KA-mediated behavioural and excitotoxic anomalies and restored altered expression of Bax, cleaved caspase-3, phospho-Akt (Ser473) and cAMP response element binding protein (CREB). Surprisingly, restoration of Bcl2 and phospho-GSK3? (Ser9) by ABT-239 did not reach the level of statistical significance. Co-administration of ABT-239 (1 and 3 mg/kg) with a sub-effective dose of SVP (150 mg/kg i.p.) yielded improved efficacy than when given alone. Similarly, low and high dose combinations of ABT-239 (1 and 3 mg/kg) with TDZD-8 (5 and 10 mg/kg i.p.) produced greater neuroprotection than any other treatment group. Our findings suggests a neuroprotective potential of ABT-239 and its combinations with SVP and TDZD-8 against KA-induced neurotoxicity, possibly mediated through in part each by modulating Akt/GSK3? and CREB pathways. The use of H3R antagonists as adjuvant in the treatment of human TLE might find potential utility, and can be pursued further. PMID:24952295

Bhowmik, Malay; Saini, Neeru; Vohora, Divya

2014-09-18

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Methylseleninic acid potentiates multiple types of cancer cells to ABT-737-induced apoptosis by targeting Mcl-1 and Bad  

DEFF Research Database (Denmark)

ABT-737, a novel small molecule inhibitor of Bcl-2 family proteins, holds great promise to complement current cancer therapies. However many types of solid cancer cells are resistant to ABT-737. One practical approach to improve its therapeutic efficacy is to combine with the agents that can overcome such resistance to restore the sensitivity. In the present study, a second-generation selenium compound methylseleninic acid (MSeA) synergistically sensitized MDA-MB-231 human breast cancer cells, HT-29 human colon cancer cells and DU145 human prostate cancer cells to apoptosis induction by ABT-737, as evidenced by greater than additive enhancement of Annexin V/FITC positive (apoptotic) cells and activation of multiple caspases and PARP cleavage. Mechanistic investigation demonstrated that MSeA significantly decreased basal Mcl-1 expression and ABT-737-induced Mcl-1 expression. Knocking down of Mcl-1 with RNAi approach supported the functional significance of this molecular target. More importantly, we identifiedinactivation of Bad by phosphorylation on ser-136 and ser-112 as a novel mechanism involved in ABT-737 resistance, which can be overcome by combining with MSeA. In addition, we found that expression of Bax was required for the efficient execution of synergistic sensitization. Our findings, for the first time, provide a strong mechanistic rationale for developing MSeA as a novel sensitizing agent of ABT-737.

Yin, Shutao; Dong, Yinhui

2012-01-01

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

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

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

2006-04-01

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Antioxidative properties of cardoon (Cynara cardunculus L.) infusion against superoxide radical, hydroxyl radical, and hypochlorous acid.  

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Polyphenols are able to act as antioxidants by virtue of their hydrogen-donating and metal-chelating capacities. Cardoon (Cynara cardunculus L.) is a species containing considerable amounts of polyphenolic compounds, namely flavonoids and phenolic acids. This study examined the antioxidant activity of cardoon lyophilized infusion against superoxide radical, hydroxyl radical, and hypochlorous acid. Superoxide radical was generated either in an enzymatic system or nonenzymatically, and the scavenging ability was assessed by the inhibition of superoxide radical-induced reduction of nitroblue tetrazolium. Hydroxyl radical was generated by the Fe3+-EDTA/ascorbate Fenton system, and scavenging capacity was estimated by evaluating the inhibition of hydroxyl radical-induced deoxyribose degradation into thiobarbituric acid-reactive substances. Inhibition of hypochlorous acid-induced 5-thio-2-nitrobenzoic acid oxidation to 5,5'-dithiobis(2-nitrobenzoic acid) was used in order to test the hypochlorous acid scavenging activity. PMID:12166995

Valentão, Patrícia; Fernandes, Eduarda; Carvalho, Félix; Andrade, Paula B; Seabra, Rosa M; Bastos, M Lourdes

2002-08-14

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Radicals from the oxidation of acetic acid-2-hydroxyethylester  

International Nuclear Information System (INIS)

The ESR-spectra of free radicals formed by the reaction of OH radicals, tert.-butoxyl radicals and acetone triplets with acetic acid-2-hydroxy ethylester have been studied in different solvents. The three radicals expected from H-atom abstraction have been identified. Further the hyperfine splittings of four adducts are presented which are produced in secondary reactions. These radicals are formed by the addition of ?-oxoalkyl and of tert.-butoxyl radicals to enol intermediates. The OH splittings of these radicals have been resolved. The couplings are solvent dependent and pass through the value zero at certain temperatures. The unusually small ?-couplings, the well resolved epsilon-splittings, and the selective line broadenings are interpreted in terms of polarisation of the radical and a barrier for internal rotation. From the line broadening a barrier of >= 2.4 kcal mol-1 was obtained. Furthermore the polarisation of the radical might favour its heterolytic dissociation in polar solvents. (orig.)

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

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

TOPOLSKA Dominika

2014-02-01

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El ABTS•+ agente oxidante de diversos compuestos químicos y su mecanismo de reciclado entre la lacasa y el sustrato / The ABTS•+ an oxidant agent of different chemical compounds and its recycling process between laccase susbtrate  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish La lacasa comercial obtenida de Myceliophtera termophila y expresada sobre Aspergillus oryzae se empleó para producir un cation radical estable y muy activo del mediador químico ABTS (ácido 2,2'-azino-bis-(3-etillbenzotiazolin-6-sulfonico) con el fin de probar la factibilidad de emplearlo como un in [...] termediario para la oxidación de una variedad de compuestos aromáticos en ausencia de la enzima. Se demostró que el catión radical ABTS•+ por si mismo oxidó al azul índigo, ácido tánico, ácido gálico, azul brillante G, azul de Coomassie, naranja 7 y p-cresol. La reacción de oxidación reveló cambios importantes en sus espectros de absorción en la región del espectro visible. Se demostró también que la oxidación de estos compuestos por la mezcla de lacasa y ABTS se puede efectuar de forma cíclica, de tal forma que la velocidad de reacción fue 94 veces mayor para el índigo, 17 veces mayor para el azul brillante G, 34 veces mayor para el naranja 7 y 5 veces mayor para el p-cresol, comparado con usar el mediador o la lacasa en forma individual. Estos resultados muestran la factibilidad de un esquema de reciclado para la oxidación final de una variedad de compuestos orgánicos en los cuales la enzima no este directamente en contacto con el mismo y que se efectúe a través del mediador ABTS•+. Abstract in english The commercial enzyme laccase cloned from Myceliophtera termophila and expressed in Aspergillus oryzae was used to produce an active, stable and oxidized form of the chemical mediator ABTS (2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid)) in order to test the feasibility of using the monoca [...] tion ABTS•+ as a recyclable intermediate for the oxidation of a variety of aromatic chemicals in the absence of the enzyme. It was shown that ABTS•+, by itself, oxidized, indigo blue, tannic and galic acids, brilliant blue G, Coomassie blue, orange 7 and p-cresol. Oxidation was assessed by important changes in their visible absorption spectra. It was also shown that oxidation of these compounds by a mixture of ABTS and laccase can be done in a cyclic manner, such a way the oxidation rate was 94 times higher for indigo, 17 times for brilliant blue G, 34 times for orange 7 and 5 times higher for p-cresol compared with using the mediator or the laccase alone. Those results show the feasibility of a recycling scheme for the final oxidation of a wide variety of aromatic compounds in which the enzyme is not directly in contact with the compound but through the intermediate ABTS•+.

M, Solís-Oba; E, Bárzana; M, García-Garibay; G, Viniegra-González.

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El ABTS•+ agente oxidante de diversos compuestos químicos y su mecanismo de reciclado entre la lacasa y el sustrato / The ABTS•+ an oxidant agent of different chemical compounds and its recycling process between laccase susbtrate  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish La lacasa comercial obtenida de Myceliophtera termophila y expresada sobre Aspergillus oryzae se empleó para producir un cation radical estable y muy activo del mediador químico ABTS (ácido 2,2'-azino-bis-(3-etillbenzotiazolin-6-sulfonico) con el fin de probar la factibilidad de emplearlo como un in [...] termediario para la oxidación de una variedad de compuestos aromáticos en ausencia de la enzima. Se demostró que el catión radical ABTS•+ por si mismo oxidó al azul índigo, ácido tánico, ácido gálico, azul brillante G, azul de Coomassie, naranja 7 y p-cresol. La reacción de oxidación reveló cambios importantes en sus espectros de absorción en la región del espectro visible. Se demostró también que la oxidación de estos compuestos por la mezcla de lacasa y ABTS se puede efectuar de forma cíclica, de tal forma que la velocidad de reacción fue 94 veces mayor para el índigo, 17 veces mayor para el azul brillante G, 34 veces mayor para el naranja 7 y 5 veces mayor para el p-cresol, comparado con usar el mediador o la lacasa en forma individual. Estos resultados muestran la factibilidad de un esquema de reciclado para la oxidación final de una variedad de compuestos orgánicos en los cuales la enzima no este directamente en contacto con el mismo y que se efectúe a través del mediador ABTS•+. Abstract in english The commercial enzyme laccase cloned from Myceliophtera termophila and expressed in Aspergillus oryzae was used to produce an active, stable and oxidized form of the chemical mediator ABTS (2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid)) in order to test the feasibility of using the monoca [...] tion ABTS•+ as a recyclable intermediate for the oxidation of a variety of aromatic chemicals in the absence of the enzyme. It was shown that ABTS•+, by itself, oxidized, indigo blue, tannic and galic acids, brilliant blue G, Coomassie blue, orange 7 and p-cresol. Oxidation was assessed by important changes in their visible absorption spectra. It was also shown that oxidation of these compounds by a mixture of ABTS and laccase can be done in a cyclic manner, such a way the oxidation rate was 94 times higher for indigo, 17 times for brilliant blue G, 34 times for orange 7 and 5 times higher for p-cresol compared with using the mediator or the laccase alone. Those results show the feasibility of a recycling scheme for the final oxidation of a wide variety of aromatic compounds in which the enzyme is not directly in contact with the compound but through the intermediate ABTS•+.

M, Solís-Oba; E, Bárzana; M, García-Garibay; G, Viniegra-González.

2007-12-01

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Structural Insights into 2,2'-Azino-Bis(3-Ethylbenzothiazoline-6-Sulfonic Acid) (ABTS)-Mediated Degradation of Reactive Blue 21 by Engineered Cyathus bulleri Laccase and Characterization of Degradation Products.  

Science.gov (United States)

Advanced oxidation processes are currently used for the treatment of different reactive dyes which involve use of toxic catalysts. Peroxidases are reported to be effective on such dyes and require hydrogen peroxide and/or metal ions. Cyathus bulleri laccase, expressed in Pichia pastoris, catalyzes efficient degradation (78 to 85%) of reactive azo dyes (reactive black 5, reactive orange 16, and reactive red 198) in the presence of synthetic mediator ABTS [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)]. This laccase was engineered to degrade effectively reactive blue 21 (RB21), a phthalocyanine dye reported to be decolorized only by peroxidases. The 816-bp segment (toward the C terminus) of the lcc gene was subjected to random mutagenesis and enzyme variants (Lcc35, Lcc61, and Lcc62) were selected based on increased ABTS oxidizing ability. Around 78 to 95% decolorization of RB21 was observed with the ABTS-supplemented Lcc variants in 30 min. Analysis of the degradation products by mass spectrometry indicated the formation of several low-molecular-weight compounds. Mapping the mutations on the modeled structure implicated residues both near and far from the T1 Cu site that affected the catalytic efficiency of the mutant enzymes on ABTS and, in turn, the rate of oxidation of RB21. Several inactive clones were also mapped. The importance of geometry as well as electronic changes on the reactivity of laccases was indicated. PMID:25261507

Kenzom, T; Srivastava, P; Mishra, S

2014-12-15

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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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Repair of amino acid radicals by a vitamin E analogue.  

Science.gov (United States)

Free radicals derived from one-electron oxidation of the amino acids tryptophan, tyrosine, methionine and histidine have been found to be rapidly (k = 10(7) -10(9) dm3 mol-1 s-1) and efficiently repaired by Trolox C, a vitamin E analogue. The reactions form a relatively stable phenoxyl radical of Trolox C (lambda max = 440 nm; epsilon = 5.4 X 10(3) mol dm-3 cm-1). The radical cation of tryptophan is more rapidly repaired than the neutral tryptophan radical. Repair of tryptophanyl radicals in the enzyme lysozyme has also been observed. The results suggest that a function of alpha-tocopherol in membranes may be the repair of radicals of integral membrane proteins. PMID:6704121

Bisby, R H; Ahmed, S; Cundall, R B

1984-02-29

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Amino acid peroxyl radicals. Formation and reaction with ascorbate  

International Nuclear Information System (INIS)

p> M-1s-1. The peroxyl radicals of all amino acids studied here were reduced by oxidizing ascorbate to the ascorbyl radical. The reaction was followed at 360 nm, where ascorbyl radical has an absorption coefficient of 3300 M-1cm-1, and the derived rate constants were all close to 107 M-1s-1. However, the spontaneous decay of peroxyl radicals is also fast and competes with the reaction with ascorbate. It is to be stressed that reaction of AAOO· and ascorbate gives rise to hydroperoxides (AAOOH) that are also reactive molecules. Our study suggests that reaction with protein radicals may be responsible for the ascorbate loss reported in organisms exposed to oxidative stress.

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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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Oxidation of DMSO and methanesulfinic acid by the hydroxyl radical.  

Science.gov (United States)

The quantitation of methanesulfinic acid, the reaction product of dimethylsulfoxide oxidation by the hydroxyl radical, has been reported as a useful tool for the detection of this radical. The present report describes two HPLC methods for determination of methanesulfinate. The first is based on the reversed phase separation and detection of the derivative formed between methanesulfinate and the diazonium salt fast garnet GBC. The second is based on anion exchange HPLC using conductivity detection. In incubations containing xanthine plus xanthine oxidase, the formation of the hydroxyl radical was demonstrated by trapping with DMSO and detection of methanesulfinate. Formation of the sulfinate from DMSO did not occur in the presence of catalase or with the omission of xanthine oxidase. In the absence of xanthine oxidase, methanesulfinate added as an internal standard could be completely recovered. In the presence of of xanthine oxidase, however, the recovery of added methanesulfinate was less than 40%. Using the Fenton reaction to generate these radicals, both methanesulfinate and methanesulfonate were formed in the presence DMSO. In incubations with methanesulfinate, hydroxyl radical generation led to stoichiometric loss of methansulfinate and production of methanesulfonate. Methanesulfinate was only slowly oxidized to methanesulfonate in incubations containing hydrogen peroxide in the absence of iron. The data illustrate that the product of DMSO oxidation by the hydroxyl radical, methanesulfinate, is further oxidized by this radical to methanesulfonate. Determination of methanesulfinate formation from DMSO underestimates the production of the hydroxyl radical. PMID:7744311

Scaduto, R C

1995-02-01

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An efficient synthesis of the taxane-derived anticancer agent ABT-271.  

Science.gov (United States)

ABT-271, 1, has been identified as a promising anticancer agent. ABT-271 is a novel taxane possessing a C9-(R)-hydroxyl group as opposed to a C9-ketone which is present in Taxol and Taxotere. To further evaluate ABT-271 as a potential anticancer agent, an efficient synthesis was developed which allows the large scale synthesis of ABT-271. Ketalization of the 7,9-diol of 9-DHAB-III, 2, allows selective removal of the C13-acetate with phenyllithium. The resulting C13-hydroxyl group is then acylated using LiHMDS and beta-lactam 22 to give ABT-271 in protected form. The protecting groups were removed first by acidic hydrolysis followed by basic hydrolysis to provide ABT-271. Application of this synthetic sequence provided over 600 g of ABT-271, 1. PMID:11348114

DeMattei, J A; Leanna, M R; Li, W; Nichols, P J; Rasmussen, M W; Morton, H E

2001-05-18

20

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.)

 
 
 
 
21

Uric acid as radical scavenger and antioxidant in the heart.  

Science.gov (United States)

Uric acid (UA) is released from the heart of many species, including man, and its site of formation has been shown to be the microvascular endothelium. Since UA reacts with oxygen radicals in vitro, experiments were conducted on guinea pig hearts perfused with Krebs-Henseleit buffer (KHB) to evaluate whether the formation of UA could afford protection from damage by radicals and oxidants. The following results were obtained: (1) Upon addition of the hydroxyl radical scavenger DMSO to the perfusate, the coronary rate of release of endogenous uric acid was increased relative to the precursor purines. (2) UA was degraded during passage through the coronary system and also in KHB in vitro after addition of substances generating hydroxyl radicals or hypochlorite. Superoxide (O2-) radicals did not seem to react directly with UA, though UA concentration-dependently quenched the chemiluminescence generated from luminol in the presence of O2- and OH radicals. (3) Coronary dilation by acetylcholine (Ach) and sub-microM concentrations of adenosine, induced by both via endothelial mechanisms, was attenuated after prolonged inhibition of endothelial UA formation by allopurinol. Furthermore, the effect of Ach but not of adenosine proved acutely sensitive to methylene blue and O2-, substances known to inactivate EDRF. This finding suggests involvement of EDRF in Ach-mediated, but not in adenosine-induced dilatation of the intact coronary system. Exogenously applied UA prevented the impairment of vascular responses to Ach and adenosine caused by allopurinol, and to Ach upon generation of O2-. (4) Hearts performed more pressure-volume work and exhibited greater functional stability when perfused with KHB supplemented with UA in a physiological concentration.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2556684

Becker, B F; Reinholz, N; Ozçelik, T; Leipert, B; Gerlach, E

1989-11-01

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URIC ACID REACTION WITH DPPH RADICALS AT THE MICELLAR INTERFACE  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in spanish 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

23

Radical products of radiolysis of polycrystalline salts of dialkylphosphoric acids and trimethylphosphate crystallosolvate  

International Nuclear Information System (INIS)

Radiolysis radical products of uranyl and calcium salts of dimethyl- and dibutylphosphoric acids, and trimethylphosphate crystallosolvate are investigated by the EPR method. The free radical five basic types are stabilized at radiolysis of dialkylphosphoric acid polycrystalline salts at 77 K: alkylphosphate, phosphoranyl, alkyl, phosphonyl and, presumably, oxycentered ones. Alkylphosphate radicals - the precursors of radiolysis acid products of trialylphosphates and dialkylphosphoric acid salts - are formed by the reaction between cation-radical and organic phosphate molecule. The most stable form of alkylphosphate radical in the long-chain alkylphosphates is the radical with unpaired spin localization in ?-position to the ester group

24

Unexpectedly high indoor hydroxyl radical concentrations associated with nitrous acid.  

Science.gov (United States)

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

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

2013-08-13

25

Identification of radical scavengers in sweet grass (Hierochloe odorata).  

Science.gov (United States)

Extracts from aerial parts of sweet grass (Hierochloe odorata) were active DPPH free radical scavengers. The active compounds were detected in extract fractions using HPLC with on-line radical scavenging detection. After multistep fractionation of the extract, two new natural products possessing radical scavenging activity were isolated, and their structures were elucidated by NMR and MS. They were identified as 5,8-dihydroxybenzopyranone and 5-hydroxy-8-O-beta-D-glucopyranosyl-benzopyranone. Activities of the compounds isolated were tested by DPPH and ABTS free radical scavenging assays, and compared with the known natural antioxidant rosmarinic acid and Trolox. PMID:11982419

Pukalskas, Audrius; van Beek, Teris A; Venskutonis, Rimantas P; Linssen, Jozef P H; van Veldhuizen, Albertus; de Groot, Aede

2002-05-01

26

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

27

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

International Nuclear Information System (INIS)

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 N2O/O2-saturated solutions leads to a mixture of peroxyl radical isomers; reaction of 13-hydroperoxylinoleic acid (13-LOOH) with azide radicals in N2O-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 N3 with rate constants exceeding 109 dm3 mol-1 s-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 (> 107 dm3 mol-1 s-?1), with aroxyl radicals to form covalent adducts (> 108 dm3 mol-1 s-1), as well as for their bimilecular decay (3.0 x 108 dm3 mol-1 s-1). These results demonstrate high reactivity of fatty acid peroxyl radicals and flavone antioxidants in aqueous solution. flavone antioxidants in aqueous solution. (author)

28

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

29

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)

30

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

31

Radical quenching by rosmarinic acid from Lavandula vera MM cell culture.  

Science.gov (United States)

This study was conducted to evaluate the radical scavenging capacities of extracts and preparations from a Lavandula vera MM plant cell culture with different rosmarinic acid content and to compare them with pure rosmarinic and caffeic acids as well. The methods, which were used are superoxide anion and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radicals scavenging assays. Results showed that extracts and preparations from Lavandula vera MM possess strong radical scavengers, as the best both radical scavengers appeared to be the fractions with enriched rosmarinic acid content, obtained after ethylacetate fractioning (47.7% inhibition of superoxide radicals and 14.2 microM 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid equivalents, respectively). These data reveal the possibilities for application of these preparations as antioxidants. PMID:16989310

Kovacheva, Elena; Georgiev, Milen; Pashova, Svetlana; Angelova, Maria; Ilieva, Mladenka

2006-01-01

32

Phenylpropanoid acid esters from Korean propolis and their antioxidant activities.  

Science.gov (United States)

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

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

2014-08-01

33

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

34

Evaluation of the Antiradical Properties of Phenolic Acids  

Science.gov (United States)

Antioxidant capacity (AOC) against peroxyl radical and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) radical cation was measured for a series of p-hydroxybenzoic (HB) and p-hydroxycinnamic (HC) acids at different pH. Quantum-chemical computation was performed using Gaussian 3.0 software package to calculate the geometry and energy parameters of the same compounds. Significant correlations were revealed between AOC and a number of calculated parameters. The most significant AOC descriptors for the studied compounds against peroxyl radical were found to be HOMO energy, rigidity (?) and Mulliken charge on the carbon atom in m-position to the phenolic hydroxyl. The most significant descriptor of the antioxidant properties against the ABTS radical cation at pH 7.40 is electron transfer enthalpy from the phenolate ion. The mechanism of AOC realization has been proposed for HB and HC acids against both radicals. PMID:25229820

Koroleva, Olga; Torkova, Anna; Nikolaev, Ilya; Khrameeva, Ekaterina; Fedorova, Tatyana; Tsentalovich, Mikhail; Amarowicz, Ryszard

2014-01-01

35

Evaluation of the Antiradical Properties of Phenolic Acids  

Directory of Open Access Journals (Sweden)

Full Text Available Antioxidant capacity (AOC against peroxyl radical and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid diammonium salt (ABTS radical cation was measured for a series of p-hydroxybenzoic (HB and p-hydroxycinnamic (HC acids at different pH. Quantum-chemical computation was performed using Gaussian 3.0 software package to calculate the geometry and energy parameters of the same compounds. Significant correlations were revealed between AOC and a number of calculated parameters. The most significant AOC descriptors for the studied compounds against peroxyl radical were found to be HOMO energy, rigidity (? and Mulliken charge on the carbon atom in m-position to the phenolic hydroxyl. The most significant descriptor of the antioxidant properties against the ABTS radical cation at ?? 7.40 is electron transfer enthalpy from the phenolate ion. The mechanism of AOC realization has been proposed for HB and HC acids against both radicals.

Olga Koroleva

2014-09-01

36

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

International Nuclear Information System (INIS)

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

37

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

International Nuclear Information System (INIS)

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

38

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

Energy Technology Data Exchange (ETDEWEB)

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

Miyagawa, I.; Swann J.T. Jr.

1986-02-15

39

Decarboxylative C-H arylation of benzoic acids under radical conditions.  

Science.gov (United States)

A decarboxylative radical cyclization reaction has been developed for the synthesis of fluorenones. The reaction uses Ag(I)/K2S2O8 to oxidatively decarboxylate an aroylbenzoic acid to an aryl radical, which undergoes cyclization to afford fluorenone products in good yield. PMID:22571756

Seo, Sangwon; Slater, Mark; Greaney, Michael F

2012-05-18

40

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

 
 
 
 
41

Electrochemical examination of the ascorbic acid radical anion in non-aqueous electrolytes  

International Nuclear Information System (INIS)

A quasi-reversible redox reaction involving ascorbic acid was observed in non-aqueous electrolytes at conductive diamond electrode. The chemical reversibility of these reactions is consistent with ascorbic acid being reduced to the ascorbic acid radical anion in a one-electron process, with subsequent reoxidation to ascorbic acid. This is the first report on the electrochemical production of the ascorbic acid radical anion in non-aqueous electrolytes. Ascorbyl 6-stearate and 4-hydroxy 2(5H)-furanone, which have somewhat similar structures as ascorbic acid, also showed one-electron transfer reduction reaction producing radicals with a single negative charge, suggesting that these compounds follow the same electrochemical behavior as ascorbic acid. The double bond and hydroxyl substituent on the five-membered ring are shown to be necessary for the stabilization of the radical anions. It was confirmed by the calculation of the total energy using molecular orbital methods that resonance structures involving the double-bond and hydroxyl group provide significant stabilization of the radical anions. Electrochemical preparation may be a useful method for the detailed study of radicals, their molecular structure and reactivity

42

Electrochemical examination of the ascorbic acid radical anion in non-aqueous electrolytes  

Energy Technology Data Exchange (ETDEWEB)

A quasi-reversible redox reaction involving ascorbic acid was observed in non-aqueous electrolytes at conductive diamond electrode. The chemical reversibility of these reactions is consistent with ascorbic acid being reduced to the ascorbic acid radical anion in a one-electron process, with subsequent reoxidation to ascorbic acid. This is the first report on the electrochemical production of the ascorbic acid radical anion in non-aqueous electrolytes. Ascorbyl 6-stearate and 4-hydroxy 2(5H)-furanone, which have somewhat similar structures as ascorbic acid, also showed one-electron transfer reduction reaction producing radicals with a single negative charge, suggesting that these compounds follow the same electrochemical behavior as ascorbic acid. The double bond and hydroxyl substituent on the five-membered ring are shown to be necessary for the stabilization of the radical anions. It was confirmed by the calculation of the total energy using molecular orbital methods that resonance structures involving the double-bond and hydroxyl group provide significant stabilization of the radical anions. Electrochemical preparation may be a useful method for the detailed study of radicals, their molecular structure and reactivity.

Yoshimura, M.; Honda, K.; Kondo, T.; Rao, T.N.; Tryk, D.A.; Fujishima, A

2002-10-15

43

Radical-induced Cis-Trans isomerization of fatty acids: a theoretical study.  

Science.gov (United States)

Trans fatty acids (TFAs) create deleterious effects; thus their existence in humans is a great health concern. TFAs can be obtained through diet, or they can be formed endogenously by radical-induced cis to trans isomerization. The mechanism of isomerization of fatty acid catalyzed by radicals including nitrogen dioxide (NO2(•)), thiyl (RS(•)), and peroxide (ROO(•)) radicals were investigated using density functional theory. With linoleic acid, a fatty acid consisting of two homoconjugated C?C bonds, we found that the radical addition mechanism is more favorable than the hydrogen abstraction mechanism. For all investigated radicals, the isomerization catalyzed by RS(•) radical involves the smallest reaction barrier. We found that NO2(•) reactions through the N-terminus are more favorable than reactions through the O-terminus. The reaction barriers for NO2(•) catalyzed isomerizations were found to be lowered to a larger extent in polar solvent. ?-carotene and lycopene were shown to protect fatty acids from isomerization by intercepting the isomerization-causing radicals. PMID:24911614

Tzeng, Yu-Zan; Hu, Ching-Han

2014-06-26

44

Cell fatty acid composition affects free radical formation during lipid peroxidation.  

Science.gov (United States)

Lipid-derived free radicals generated from intact human U937 monocytes exposed to iron-induced oxidative stress were detected by electron paramagnetic resonance (EPR) with the spin trap alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN). Lipid radical formation was enhanced when the cells were enriched with n-3 or n-6 polyunsaturated fatty acids. Computer simulation indicated that at least two POBN spin adducts were formed, having spectral characteristics consistent with carbon-centered radicals (aN = 15.9 G and aH = 2.6 G; aN = 15.1 G and aH = 2.8 G). These alkyl radicals are probably formed by beta-scission of alkoxyl radicals. POBN spin adduct formation correlated with ethane generation. Addition of ascorbate to the assay medium greatly increased the radical signal intensity. Although radical generation was cell dependent and POBN spin adducts were observed in cell homogenates, the adducts formed by the intact cells were detected only in the extracellular medium. These findings indicate that the extent of lipid radical formation in response to oxidative stress can be influenced by changes in the polyunsaturated fatty acid composition of the cell lipids and suggest the possibility that carbon-centered lipi radicals may interact with extracellular structures. PMID:8048478

North, J A; Spector, A A; Buettner, G R

1994-07-01

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.

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

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

49

Free radical production in the esophago-gastro-duodenal mucosa in response to acid and bile.  

Science.gov (United States)

Several studies have demonstrated the role of free radicals in causing esophagus-gastro-duodenal mucosal injury. The present study has been designed to investigate: whether acid, bile salts and a combination of bile + acid could determine the production of O2-derived free radicals by oesophageal, gastric and duodenal mucosa; which agent is capable of producing more free radicals and if O2-derived free radicals production depends on the duration of contact with acid, bile salts and their combination. Wistar rats' gastro-intestinal mucosa were perfused with bile, acid and a combination of bile + acid at pH4 and pH2 for 1 hour and 2 hours. Free radical production (FRP) was assessed by chemoluminescence. After 1 hour, the increase in FRP in comparison with control reached statistical significance (P free radicals than the stomach at all pH values. However, this difference reached statistical significance at pH1 and 2 only. In comparison to control, FRP was increased by bile (pH7) infusion after 1 and 2 hours. There was increased FRP in all segments after the infusion of bile at pH2 and 4 in comparison to control. Infusion of bile at pH2 stimulates more FRP than infusion of bile at pH4 in all segments. This increased FRP reaches statistical significance in the esophagus after 2 hours of infusion, in the stomach after 1 and 2 hours of infusion, but in the duodenum it does not reach statistical significance. Acid, bile and bile + acid at pH2 and 4 can cause free radical production in esophageal, gastric and duodenal mucosa. Their role in producing free radicals is different according to the segment and the chemical composition of the solution. PMID:16643178

Boni, L; Benevento, A; Shimi, S M; Cuschieri, A

2006-01-01

50

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

51

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

International Nuclear Information System (INIS)

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

52

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

53

Reactions of halogenated organic peroxyl radicals with various purine derivatives and ascorbic acid in quaternary microemulsion  

International Nuclear Information System (INIS)

Absolute rate constants for the one electron oxidation of guanine, xanthine, hypoxanthine, uric acid and ascorbic acid in quaternary microemulsion have been determined using the technique of pulse radiolysis. The rate constants for the radical CBr3O2. are slightly higher than those for CCl3O2. (author)

54

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

International Nuclear Information System (INIS)

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

55

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

56

Oxidation of polyunsaturated fatty acids and lipids through thiyl and sulfonyl radicals: reaction kinetics, and influence of oxygen and structure of thiyl radicals.  

Science.gov (United States)

Thiyl free radicals have been shown to react with polyunsaturated fatty acids via abstraction of bisallylic hydrogen, forming pentadienyl radicals, and via addition to the double bonds. In the absence of oxygen, the latter pathway leads to regeneration of thiyl radicals through beta-elimination or "repair" of the adduct radicals by thiols. In the presence of oxygen, fixation of thiyl-induced damage occurs through reaction of O2 with the pentadienyl radical (yielding conjugated dienyl peroxyl radicals) and also with the thiyl-to-double bond adduct radical. A quantitative reaction scheme evaluated from these data considers abstraction, addition, rearrangement, and repair reactions, and the evaluation of rate constants for the individual steps. Absolute rate constants have been measured, in particular, for reactions of thiyl free radicals from glutathione, cysteine, homocysteine, N-acetylcysteine, cysteine ethyl ester, penicillamine, captopril, mercaptoethanol, and dithiothreitol with polyunsaturated fatty acids (PUFAs) ranging from 18:2 to 22:6, and the lipids trilinolein and trilinolenin. The rate constants for hydrogen abstraction were found to be typically of the order of 10(7) mol-1 dm3 s-1 and to increase with increasing lipophilicity of the attacking thiyl radical. Thioperoxyl radicals, RSOO., were found to be rather unreactive toward PUFAs, in contrast to the isomer sulfonyl radicals, RSO2., which not only abstract hydrogen from the bisallylic methylene groups of the PUFAs (although only at relatively small yield) but also readily add to the PUFA double bonds (major pathway). Specific information was obtained on the optical properties of the thiyl radical derived from the ACE inhibitor captopril, CpS. (lambda max = 340 nm, epsilon = 460 +/- 50 mol-1 dm3 cm-1), and its conjugate disulfide radical anion (CpS:.SCp) (lambda max = 420 nm). PMID:1731611

Schöneich, C; Dillinger, U; von Bruchhausen, F; Asmus, K D

1992-02-01

57

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

58

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

59

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.

60

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

International Nuclear Information System (INIS)

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

 
 
 
 
61

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

62

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

63

Formation of radical zwitterions from methoxylated benzoic acids. 2. OH adducts as precursors  

International Nuclear Information System (INIS)

Using spectrophotometric and conductometric pulse radiolysis and in situ electron spin resonance techniques it was found that OH adducts, formed from mono-, di-, and trimethoxylated benzoic acids by attachment of OH to nonsubstituted ring positions, react with H+ (k = 108 - 109 M-1 s-1) to yield radical zwitterions via elimination of H2O from the protonated OH adduct. With OH adducts from 2,4- and 2,6-dimethoxybenzoic acid and 2,4,5- and 2,4,6-trimethoxybenzoic acid radical zwitterions are additionally produced by a pH independent process involving elimination of OH- (k approximately equal to 4 x 104 s-1). The radical zwitterions react with H adducts with rate constants of (8 to 40) x 108 M-1 s-1

64

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

Scientific Electronic Library Online (English)

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

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

2008-03-01

65

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

Scientific Electronic Library Online (English)

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

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

66

On the e.s.r. determination of radical yields in X-irradiated amino acids  

International Nuclear Information System (INIS)

Studies of the temperature dependence of the areas under the e.s.r. absorption spectra of X-ray-induced free radicals in amino acids at various power levels and of power saturation at different temperatures are reported. They indicate that power saturation is responsible for the anomalous Curie-Weiss behaviour previously reported. The consequences of power saturation to the e.s.r. determination of radical yields are discussed. The effect of impurity e.s.r. signals in amino acids on quantitative e.s.r. determinations is also discussed. (author)

67

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

Science.gov (United States)

Thiyl radicals isomerize the olefinic bonds of natural all- cis-polyunsaturated fatty acids into their trans-state. Using low doses of gamma-irradiation we partially converted arachidonic acid (AA) by thiyl radical attack into its mono- trans-forms. The enzyme-driven prostaglandin metabolism was studied in these samples in liquid model as well as in in vivo conditions with four different detection methods. A dramatic inhibition of the metabolism explained by blocking of the cyclooxygenase by trans-isomers has been found.

Kratzsch, S.; Drössler, K.; Sprinz, H.; Brede, Ortwin

2003-06-01

68

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

Energy Technology Data Exchange (ETDEWEB)

Thiyl radicals isomerize the olefinic bonds of natural all-cis-polyunsaturated fatty acids into their trans-state. Using low doses of gamma-irradiation we partially converted arachidonic acid (AA) by thiyl radical attack into its mono-trans-forms. The enzyme-driven prostaglandin metabolism was studied in these samples in liquid model as well as in in vivo conditions with four different detection methods. A dramatic inhibition of the metabolism explained by blocking of the cyclooxygenase by trans-isomers has been found.

Kratzsch, S.; Droessler, K.; Sprinz, H.; Brede, Ortwin E-mail: brede@mpgag.uni-leipzig.de

2003-06-01

69

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

Directory of Open Access Journals (Sweden)

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

70

Reactivity of glycyl-amino acids toward hydroxyl radical in neutral aqueous solutions  

International Nuclear Information System (INIS)

Rate constants for reactions of hydroxyl radicals with several glycyl-amino acids were determined by a competition method using p-nitrosodimethylailine as a reference compound. For glycyl-aliphatic amino acids, the enhancement of reactivity was observed as compared with the corresponding free amino acids. The reactivity was explained qualitatively in terms of partial reactivities assigned to each C-H bond of the dipeptides. For glycyl-aromatic amino acids, the rate constants were found to be almost equal to those of the corresponding free amino acids. The reactivity of a protein toward hydroxyl radical was well understood by summation of the rate constants, corrected by steric factors, of amino acid residues located on surface of the protein. The enhanced reactivity of the aliphatic peptides was interpreted in terms of the difference in interaction energy between NH2- and NH3+-forms of an aliphatic amino acid, which was calculated for the system including glycine and hydroxyl radical according to CNDO/2 method. (auth.)

71

Spectral and kinetic characteristics of the ?-propionic acid methyl ester radical in cyclohexane and water  

International Nuclear Information System (INIS)

The ?-propionic acid methyl ester radical was produced in dissociative electron capture reaction of 2-chloropropionic acid methyl ester. The absorption maxima of the radical are at 310 and 300 nm in cyclohexane and water with extinction coefficients of 440±50 and 400±50 mol-1 dm3 cm-1. The second order decay rate parameter in water is (2.3±0.5)x109 mol-1 dm3 s-1. The peroxy radicals have the characteristics: ?max=265-270 nm, ?max=700-900 mol-1 dm3 cm-1 and 2k = (7±2) x 108 mol-1 dm3 s-1. (author) 6 refs.; 4 figs.; 1 tab

72

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

73

Reactivity of the hydrated electron and the hydroxyl radical with boric acid in aqueous solutions  

Science.gov (United States)

The reactivity of the hydrated electron and the hydroxyl radical with boric acid has been investigated by steady-state and pulse radiolytic techniques. No evidence was found for appreciable reactivity with hydroxyl radicals by either method and an upper limit of 5 × 10 4 dm 3 mol -1 s -1 is estimated for the reaction rate constant. Steady-state irradiations gave no evidence for reactivity with the hydrated electron, but pulse-radiolysis experiments showed the hydrated electron decay rate to be linearly dependent on boric acid concentration but independent of pH. Although superficially suggesting a reaction with boric acid it seems more likely that the enhanced decay is due to an impurity in the boric acid (probably nitrate) and an upper limit of 5 × 10 3 dm 3 mol -1 s -1 is estimated for k(e -aq + H 3BO 3).

Buxton, G. V.; Sellers, R. M.

74

Reactivity of the hydrated electron and the hydroxyl radical with boric acid in aqueous solutions  

International Nuclear Information System (INIS)

The reactivity of the hydrated electron and the hydroxyl radical with boric acid has been investigated by steady-state and pulse radiolytic techniques. No evidence was found for appreciable reactivity with hydroxyl radicals by either method and an upper limit of 5 x 104 dm3 mol-1 s-1 is estimated for the reaction rate constant. Steady-state irradiations gave no evidence for reactivity with the hydrated electron, but pulse-radiolysis experiments showed the hydrated electron decay rate to be linearly dependent on boric acid concentration but independent of pH. Although superficially suggesting a reaction with boric acid it seems more likely that the enhanced decay is due to an impurity in the boric acid (probably nitrate) and an upper limit of 5 x 103 dm3 mol-1 s-1 is estimated for k(e-sub(aq) + H3B03). (author)

75

Kinetics of free radical decay reactions in lactic acid homo and copolymers irradiated to sterilization dose  

International Nuclear Information System (INIS)

The kinetics of free radical decay reactions of poly(L-Lactic acid), poly(DL-Lactic acid) and random copolymer of lactic and glycolic acid have been investigated for decays taking place in air and in vacuum. The change in ESR lines of ?-irradiated polymers have been followed over a long time period. The decay has been found to follow neither simple first-order nor second-order kinetics. Various kinetic approaches including composite first or second-order mechanisms and diffusion-controlled first or second-order equations were determined to be also unsatisfactory. The decay of radicals in bulk irradiated lactic acid homo and copolymers was found to be best described when the second-order non-classical equation with time dependent rate constant approach was used. (Author)

76

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

77

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)

78

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

79

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

80

Synthesis, characterization and radical scavenging activity of aromatic amine conjugates of 5-aminosalicylic acid  

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Full Text Available 5-Aminosalicylic acid is an anti-inflammatory drug used in the treatment of inflammatory bowel diseases including ulcerative colitis and Crohn’s disease. Due to its rapid and extensive absorption in the upper gastro-intestinal tract, substantial amount of 5-aminosalicylic acid is already lost before reaching the site of action, i.e. the colon. In order to prevent this loss of drug, carrier linked prodrug approach has been used and azo prodrugs have been synthesized with a purpose of colon targeting. The present research describes the synthesis and characterization of azo prodrugs of 5-aminosalicylic acid with aromatic amines. The synthesized prodrugs were tested for antioxidant activity using DPPH (2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity. All the synthesized compounds were found to possess mild to moderate radical scavenging activity. DOI: http://dx.doi.org/10.4314/bcse.v28i3.17

K. Harveer,

2014-09-01

 
 
 
 
81

Hypochlorous acid as a precursor of free radicals in living systems.  

Science.gov (United States)

Hypochlorous acid (HOCl) is produced in the human body by the family of mammalian heme peroxidases, mainly by myeloperoxidase, which is secreted by neutrophils and monocytes at sites of inflammation. This review discusses the reactions that occur between HOCl and the major classes of biologically important molecules (amino acids, proteins, nucleotides, nucleic acids, carbohydrates, lipids, and inorganic substances) to form free radicals. The generation of such free radical intermediates by HOCl and other reactive halogen species is accompanied by the development of halogenative stress, which causes a number of socially important diseases, such as cardiovascular, neurodegenerative, infectious, and other diseases usually associated with inflammatory response and characterized by the appearance of biomarkers of myeloperoxidase and halogenative stress. Investigations aimed at elucidating the mechanisms regulating the activity of enzyme systems that are responsible for the production of reactive halogen species are a crucial step in opening possibilities for control of the development of the body's inflammatory response. PMID:24490735

Panasenko, O M; Gorudko, I V; Sokolov, A V

2013-12-01

82

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

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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.

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

2012-01-01

83

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

84

The reaction of sulfenic acids with peroxyl radicals: insights into the radical-trapping antioxidant activity of plant-derived thiosulfinates.  

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Sulfenic acids play a prominent role in biology as key participants in cellular signaling relating to redox homeostasis, in the formation of protein-disulfide linkages, and as the central players in the fascinating organosulfur chemistry of the Allium species (e.g., garlic). Despite their relevance, direct measurements of their reaction kinetics have proven difficult owing to their high reactivity. Herein, we describe the results of hydrocarbon autoxidations inhibited by the persistent 9-triptycenesulfenic acid, which yields a second order rate constant of 3.0×10(6) ?M(-1) ?s(-1) for its reaction with peroxyl radicals in PhCl at 30?°C. This rate constant drops 19-fold in CH(3)CN, and is subject to a significant primary deuterium kinetic isotope effect, k(H)/k(D) = 6.1, supporting a formal H-atom transfer (HAT) mechanism. Analogous autoxidations inhibited by the Allium-derived (S)-benzyl phenylmethanethiosulfinate and a corresponding deuterium-labeled derivative unequivocally demonstrate the role of sulfenic acids in the radical-trapping antioxidant activity of thiosulfinates, through the rate-determining Cope elimination of phenylmethanesulfenic acid (k(H)/k(D) ? 4.5) and its subsequent formal HAT reaction with peroxyl radicals (k(H)/k(D) ? 3.5). The rate constant that we derived from these experiments for the reaction of phenylmethanesulfenic acid with peroxyl radicals was 2.8×10(7) ?M(-1) ?s(-1); a value 10-fold larger than that we measured for the reaction of 9-triptycenesulfenic acid with peroxyl radicals. We propose that whereas phenylmethanesulfenic acid can adopt the optimal syn geometry for a 5-centre proton-coupled electron-transfer reaction with a peroxyl radical, the 9-triptycenesulfenic is too sterically hindered, and undergoes the reaction instead through the less-energetically favorable anti geometry, which is reminiscent of a conventional HAT. PMID:22473818

Amorati, Riccardo; Lynett, Philip T; Valgimigli, Luca; Pratt, Derek A

2012-05-14

85

Synthesis of the C-13 side chain precursors of the 9-dihydrotaxane analogue ABT-271.  

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N-Boc-L-Leucinol was converted to two C-13 side chain precursors of the 9-dihydrotaxane analogue ABT-271. The trans-oxazolidine acid 4 and the cis-Boc-lactam 2b were prepared in 44% and 40% overall yield, respectively, and with excellent (>98%) stereochemical purity. PMID:11073661

Leanna, M R; DeMattei, J A; Li, W; Nichols, P J; Rasmussen, M; Morton, H E

2000-11-16

86

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

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

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

2000-03-01

87

Radical scavenging capacity of Agrimonia eupatoria and Agrimonia procera.  

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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

88

Adsorption of a carboxylic acid-functionalized aminoxyl radical onto SiO?.  

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Silicon wafers both without and with silicon(IV) oxide surface coverage were covered with benzene solutions of stable organic radical 3-(N-tert-butyl-N-aminoxyl)benzoic acid (mNBA). X-ray photoelectron spectroscopy supported the presence of the radical on both surface-cleaned (oxide-reduced) and oxide-covered surfaces. Optical waveguide spectroscopy showed that the radical retained its structure while adsorbed to the surface of the wafers, without noticeable decomposition. AFM and MFM imaging showed that the radical formed blocky particles with a change in rms roughness from 0.3 nm premodification to 1.7 nm postmodification on the surface-cleaned silicon. Similar experiments using oxide-coated silicon showed that the radical adsorbed to form much smoother layers, with a small change in rms roughness from 0.2 to 0.3 nm. Contact angle measurements of water on the premodified and postmodified samples showed a large, hydrophobic change in the silicon oxide surface but only a modest change in the surface-cleaned silicon surface. Samples of mNBA adsorbed onto silica gel showed strong electron-spin resonance signals from the aminoxyl spin, even years after production. The results demonstrate the prospects for treating and coating oxide-covered silicon wafers and silicon oxide-coated particles with a paramagnetically active organic substrate, without major chemical modification of the pretreatment surface; the resulting organic spin sites can be stable for years. PMID:24684264

Murata, Hidenori; Baskett, Martha; Nishide, Hiroyuki; Lahti, Paul M

2014-04-15

89

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

90

The reaction of sulfite anion radical (S03sup(.-)) with polyunsaturated fatty acids  

International Nuclear Information System (INIS)

Using the pulse radiolysis technique, S03sup(.-) was produced in aqueous solution by the reaction of S032-with either sup(.)OH or the (pseudo-) halide radicals N3sup(.),Br2sup(.-), and (SCN)2sup(.-); for the latter reactions rate constants were measured. The reaction of S03sup(.-) with linoleic, linolenic, and arachidonic acids was monitored using the strong absorption of the pentadienyl radical, one possible primary reaction product. In micellar systems no detectable reaction took place, however, monomeric fatty acids were observed to react with S03sup(.-). Lower limits of the rate constants for S03sup(.-) attack derived from the data are 1 x 105, 8 x 105, and 1.3 x 106 (dm3 mol-1 s-1) for linoleate, linolenate, and arachidonate, respectively. (author)

91

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

Science.gov (United States)

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

Schittl, H.; Quint, R. M.; Getoff, N.

2007-10-01

92

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

International Nuclear Information System (INIS)

The radiolysis of aqueous vitamin B5 (pantothenic acid) has been investigated under various experimental conditions. The highest vitamin degradation (G=3.22) was observed in solutions saturated with N2O, where 90% OH radicals are operating. As final products, the following were established: aldehydes, carboxylic acids and ammonia. Their yield strongly depends on the presence/absence of air as well as on N2O (used to convert eaq - into OH) and was determined as a function of absorbed radiation dose. HPLC-analysis showed that in all media, a main product is formed, having the highest yield in aerated solutions. Based on the chemical analysis, it appears that the OH radicals are most involved in the degradation process. A precise sequence of the reaction steps could not be given presently, because of the implication of many simultaneous reactions

93

PHENOLIC ACIDS AND FREE RADICAL SCAVENGING ACTIVITY OF ALCHEMILLA JUMRUKCZALICA PAWL  

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

M. Nikolova et al.

2012-03-01

94

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

95

Cellobiose hydrolysis and decomposition by electrochemical generation of acid and hydroxyl radicals.  

Science.gov (United States)

This paper addresses the hydrolysis of cellobiose to glucose and its further decomposition with electrochemically generated acid (H(+)) on a platinum electrode, and with electrochemically generated hydroxyl radicals (OH(·)) on boron-doped diamond (BDD). The results are compared with the hydrolysis promoted by conventional acid (H(2)SO(4)) and OH(·) (from Fenton's reaction) and supported by product analysis by using online HPLC (for soluble products) and online electrochemical mass spectrometry (for CO(2)). Cellobiose hydrolysis follows a first-order reaction, which obeys Arrhenius' law over the temperature range from 25-80 °C with different activation energies for the acid- and radical-promoted reaction, that is, approximately 118±8 and 55±1 kJ mol(-1), respectively. The high local acidity with electrochemically generated H(+) on the Pt electrode increases the rate of glucose formation, however, the active electrode (PtO(x)) interacts with glucose and decomposes it further to smaller organic acids. In addition, O(2) formed during the oxygen evolution reaction (OER) lowers the selectivity of glucose by forming side-products. OH(·) generated on a BDD electrode first hydrolyzes the cellobiose to glucose, but rapidly attacks the aldehyde on glucose, which is further decomposed to smaller aldoses and finally formaldehyde, which is subsequently oxidized electrochemically to formic acid. PMID:22907780

Kwon, Youngkook; Kleijn, Steven E F; Schouten, Klaas Jan P; Koper, Marc T M

2012-10-01

96

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

97

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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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

98

Roles of phosphate and an enoyl radical in ferritin iron mobilization by 5-aminolevulinic acid.  

Science.gov (United States)

5-Aminolevulinic acid (ALA), a heme precursor that accumulates in acute intermittent porphyria (AIP) and lead poisoning, undergoes enolization and subsequent iron-catalyzed oxidation at neutral pH. Iron is released from horse spleen ferritin (HoSF) by both ALA-generated O(2)(.-) and enoyl radical (ALA(z.rad)), which amplifies the chain of ALA oxidation (autocatalysis). Iron chelators such as EDTA, ATP, but not citrate, and phosphate accelerate this process and ALA-promoted iron release from HoSF is faster in horse spleen isoferritins containing larger amounts of phosphate in the core. ALA (+0.377 V versus standard hydrogen electrode) is less effective in releasing iron from ferritin than are thioglycollic acid, 6-hydroxydopamine, and N,N,N', N'-tetramethyl-p-phenylenediamine. During electrochemical one electron oxidation of ALA in a nitrogen atmosphere, spin trapping experiments with 3,5-dibromo-4-nitrosobenzenesulfonic acid demonstrated the formation of a spin adduct characterized by a six line signal, indicating a secondary carbon-centered radical and attributed to a resonant ALA&z.rad; radical. Iron is also released in such anaerobic electrochemical oxidations of ALA in the presence of ferritin, suggesting that, in addition to O(2)(*-), ALA&z.rad; can promote iron mobilization from ferritin. Hence, ALA&z.rad; may amplify the metal-catalyzed oxidation of ALA, damaging ALA-accumulating cells and possibly contributing to the symptoms of porphyria. PMID:11118817

Rocha, M E; Ferreira, A M; Bechara, E J

2000-12-15

99

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

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

Dorota Martysiak-?urowska

2012-03-01

100

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

 
 
 
 
101

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

102

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

103

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

International Nuclear Information System (INIS)

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

104

Conversion of a positive resist into a negative resist by induced radical reactions in solid methylmethacrylate/methacrylic acid copolymers  

International Nuclear Information System (INIS)

A study is presented of the lifetime of radicals produced by irradiation of solid methymethacrylate/methacrylic acid copolymers with ?-rays and electron beams. Radical lifetime was investigated as a function of temperature by means of electron-spinresonance spectroscopy and radiothermoluminescence. In the presence of triallylphosphate the investigated polymers are converted into negative resist materials of high radiation sensitivity. (author)

105

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)

106

Reactivity and Selectivity of Charged Phenyl Radicals Toward Amino Acids in a Fourier-Transform Ion Cyclotron Resonance (FT-ICR) Mass Spectrometer  

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The reactivity of ten charged phenyl radicals toward several amino acids was examined in the gas phase in a dual-cell Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometer. All radicals abstract a hydrogen atom from the amino acids, as expected. The most electrophilic radicals (with a greater calculated vertical electron affinity (EA) at the radical site) also react with these amino acids via NH2 abstraction (a nonradical nucleophilic addition-elimination reaction). Both the ra...

Pates, George O.; Guler, Leonard; Nash, John J.; Kentta?maa, Hilkka I.

2011-01-01

107

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...

108

Radicals in the Reaction between Peroxynitrite and Uric Acid Identified by Electron Spin Resonance Spectroscopy and Liquid Chromatography Mass Spectrometry  

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Peroxynitrite is a reactive oxidant produced in vivo in response to oxidative and other stress by the diffusion-limited reaction of nitric oxide and superoxide. This contribution is focused on the identification of free radical intermediates of uric acid formed during its reaction with peroxynitrite. The experimental approach included the ESR spin trapping of the radical generated from the reaction between uric acid and peroxynitrite at pH 7.4 and mass spectrometry studies of the trapped radi...

Imaram, Witcha; Gersch, Christine; Kim, Kyung Mee; Johnson, Richard J.; Henderson, George N.; Angerhofer, Alexander

2010-01-01

109

Enhancing decomposition rate of perfluorooctanoic acid by carbonate radical assisted sonochemical treatment.  

Science.gov (United States)

Perfluorooctanoic acid (PFOA) is a recalcitrant organic pollutant in wastewater because of its wide range of applications. Technologies for PFOA treatment have recently been developed. In this study, PFOA decomposition by sonochemical treatment was investigated to determine the effects of NaHCO3 concentrations, N2 saturation, and pH on decomposition rates and defluorination efficiencies. The results showed that PFOA decomposition by ultrasound treatment only (150 W, 40 kHz), with or without saturated N2, was PFOA decomposition and defluorination efficiencies of PFOA, however, greatly increased with the addition of carbonate radical reagents. PFOA was completely decomposed after 4h of sonochemical treatment with a carbonate radical oxidant and saturated N2. Without saturated N2, PFOA was also decomposed to a high (98.81%) degree. The highest PFOA decomposition and defluorination efficiencies occurred in N2 saturated solution containing an initial NaHCO3 concentration of 30 mM. Sonodecomposition of PFOA with CO3(-) radical was most favorable in a slightly alkaline environment (pH=8.65). There isn't any shorter-chain perfluorinated carboxylic acids detected except fluorine ions in final reaction solution. PMID:24751291

Phan Thi, Lan-Anh; Do, Huu-Tuan; Lo, Shang-Lien

2014-09-01

110

Reaction of single-standard DNA with hydroxyl radical generated by iron(II)-ethylenediaminetetraacetic acid  

International Nuclear Information System (INIS)

This study demonstrates that the reaction of Fe(II)-EDTA and hydrogen peroxide with the single-stranded nucleic acids d(pT)70 and a 29-base sequence containing a mixture of bases results in substantial damage which is not directly detected by gel electrophoresis. Cleavage of the DNA sugar backbone is enhanced significantly after the samples are incubated at 90 degree C in the presence of piperidine. The latter reaction is used in traditional Maxam-Gilbert DNA sequencing to detect base damage, and the current results are consistent with reaction of the hydroxyl radical with the bases in single-stranded DNA (although reaction with sugar may also produce adducts that are uncleaved but labile to cleavage by piperidine). We the authors propose that hydroxyl radicals may react preferentially with the nucleic acid bases in ssDNA and that reaction of the sugars in dsDNA is dominant because the bases are sequestered within the double helix. These results have implications both for the study of single-stranded DNA binding protein binding sites and for the interpretation of experiments using the hydroxyl radical to probe DNA structure or to footprint double-stranded DNA binding protein binding sites

111

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

International Nuclear Information System (INIS)

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

112

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

Science.gov (United States)

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

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

2011-07-01

113

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

Science.gov (United States)

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

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

2013-06-01

114

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

Science.gov (United States)

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

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

2013-12-01

115

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.

116

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

117

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

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

Manoel L. de Menezes

2012-01-01

118

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

119

Design and synthesis of coumarin-3-acylamino derivatives to scavenge radicals and to protect DNA.  

Science.gov (United States)

In this study, a series of coumarin-3-acylamino derivatives containing phenethylamine moiety or tyramine moiety were synthesized and their antioxidant activities were evaluated by Cu(2+)/glutathione(GSH)-, ?OH- and 2,2'-azobis(2-amidinopropane hydrochloride)(AAPH)-induced oxidation of DNA. It was found that both hydroxyl and ortho-methoxy groups at A ring, hydroxyl group at B ring and peptide bond can enhance the abilities of coumarin-3-acylamino derivatives to protect DNA against ?OH- and AAPH-induced oxidation. Moreover, these coumarin-3-acylamino derivatives were employed to scavenge 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS(+?)). We found that tyramine moiety, hydroxyl and ortho-methoxy are the key groups to enhance the activities of antioxidants to quench ABTS(+?). Therefore, tyramine linked with coumarin-3-carboxyl acid which containing hydroxyl and ortho-methoxy exhibited powerful antioxidant abilities. PMID:25011038

Yang, Yang; Liu, Qing-Wen; Shi, Ye; Song, Zhi-Guang; Jin, Ying-Hua; Liu, Zai-Qun

2014-09-12

120

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

 
 
 
 
121

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.

122

Linoleic acid hydroperoxide reacts with hypochlorous acid, generating peroxyl radical intermediates and singlet molecular oxygen  

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The reaction of hypochlorous acid (HOCl) with hydrogen peroxide is known to generate stoichiometric amounts of singlet molecular oxygen [O2 (1?g)]. This study shows that HOCl can also react with linoleic acid hydroperoxide (LAOOH), generating O2 (1?g) with a yield of 13 ± 2% at physiological pH. Characteristic light emission at 1,270 nm, corresponding to O2 (1?g) monomolecular decay, was observed when HOCl was reacted with LAOOH or with liposomes containing phosphatidylcholine hydroperoxi...

Miyamoto, Sayuri; Martinez, Glaucia R.; Rettori, Daniel; Augusto, Ohara; Medeiros, Marisa H. G.; Di Mascio, Paolo

2006-01-01

123

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

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

Lilian Regina Barros Mariutti

2008-12-01

124

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

Scientific Electronic Library Online (English)

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

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

1225-12-01

125

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

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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

126

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

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

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

2011-06-01

127

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

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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

128

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

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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

129

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

International Nuclear Information System (INIS)

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

130

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

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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...

Saša Mitrev; Sanja Kostadinovic-Velickovska

2013-01-01

131

Hydrogen peroxide and hydroxyl radical formation by methylene blue in the presence of ascorbic acid  

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Using ESR we have demonstrated the formation of the ascorbate free radical from sodium ascorbate, methylene blue and light. In oxygen uptake experiments we have observed the production of hydrogen peroxide while spin trapping experiments have revealed the iron catalyzed production of the hydroxyl free radical in this system. The presence of this highly reactive radical suggests that it could be the radical that initiates free radical damage in this photodynamic system. (orig.)

132

Redox chemistry of selenenic acids and the insight it brings on transition state geometry in the reactions of peroxyl radicals.  

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The redox chemistry of selenenic acids has been explored for the first time using a persistent selenenic acid, 9-triptyceneselenenic acid (RSeOH), and the results have been compared with those we recently obtained with its lighter chalcogen analogue, 9-triptycenesulfenic acid (RSOH). Specifically, the selenenyl radical was characterized by EPR spectroscopy and equilibrated with a phenoxyl radical of known stability in order to determine the O-H bond dissociation enthalpy of RSeOH (80.9 ± 0.8 kcal/mol): ca. 9 kcal/mol stronger than in RSOH. Kinetic measurements of the reactions of RSeOH with peroxyl radicals demonstrate that it readily undergoes H-atom transfer reactions (e.g., k = 1.7 × 10(5) M(-1) s(-1) in PhCl), which are subject to kinetic solvent effects and kinetic isotope effects similar to RSOH and other good H-atom donors. Interestingly, the rate constants for these reactions are only 18- and 5-fold smaller than those measured for RSOH in PhCl and CH3CN, respectively, despite being 9 kcal/mol less exothermic for RSeOH. IR spectroscopic studies demonstrate that RSeOH is less H-bond acidic than RSOH, accounting for these solvent effects and enabling estimates of the pKas in RSeOH and RSOH of ca. 15 and 10, respectively. Calculations suggest that the TS structures for these reactions have significant charge transfer between the chalcogen atom and the internal oxygen atom of the peroxyl radical, which is nominally better for the more polarizable selenenic acid. The higher than expected reactivity of RSeOH toward peroxyl radicals is the strongest experimental evidence to date for charge transfer/secondary orbital interactions in the reactions of peroxyl radicals with good H-atom donors. PMID:24383573

Zielinski, Zosia; Presseau, Nathalie; Amorati, Riccardo; Valgimigli, Luca; Pratt, Derek A

2014-01-29

133

Administration of the nicotinic acetylcholine receptor agonists ABT-089 and ABT-107 attenuates the reinstatement of nicotine-seeking behavior in rats.  

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Current smoking cessation pharmacotherapies have modest efficacy, and most smokers relapse within the first few days after a quit attempt. Nicotine withdrawal-induced craving and cognitive impairments predict smoking relapse during abstinence and suggest that cognitive-enhancing drugs may prevent relapse. ABT-089 and ABT-107 are subtype-selective nAChR agonists that improve cognitive performance in laboratory animals. However, there are no studies examining the effects of ABT-089 and ABT-107 on nicotine self-administration and the reinstatement of nicotine-seeking behavior, an animal model of relapse in human smokers. The goal of the present study was to determine the effects of the ?4?2*/?6?2* nAChR agonist ABT-089 and the ?7 nAChR agonist ABT-107 on nicotine taking and seeking in rats. The effects of acute ABT-089 and ABT-107 pretreatment on nicotine self-administration and reinstatement were tested in male Sprague Dawley rats. Parallel studies of ABT-089 and ABT-107 on sucrose self-administration and reinstatement were tested in separate groups of rats to determine if the effects of these drug treatments generalized to other reinforced behaviors. Nicotine and sucrose self-administration behaviors were not altered following acute administration of ABT-089 (0, 0.12, 1.2 and 12.0mg/kg) or ABT-107 (0, 0.03 and 0.3mg/kg). In contrast, both ABT-089 and ABT-107 pretreatment dose-dependently attenuated nicotine reinstatement. These effects were reinforcer-specific as no effects of ABT-089 or ABT-107 pretreatment on sucrose seeking were noted. Taken together, these findings suggest that ABT-089 and ABT-107 do not affect nicotine consumption, but may reduce the likelihood that a smoking lapse will lead to relapse. PMID:25128791

Lee, Alycia M; Arreola, Adrian C; Kimmey, Blake A; Schmidt, Heath D

2014-11-01

134

Mechanism of the OH radical scavenging activity of nordihydroguaiaretic acid: a combined theoretical and experimental study.  

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The antioxidant nordihydroguaiaretic acid (NDGA) is a plant phenolic lignan originally isolated from the creosote bush (Larrea tridentata). It has been shown that NDGA scavenges efficiently hydroxyl radicals ((*)OH). In the present paper the mechanism by which NDGA scavenges (*)OH is addressed performing a combined experimental and theoretical investigation. We found that NDGA protects, in a concentration-dependent way, bovine serum albumin and DNA from the damage induced by (*)OH generated by the Fenton reaction. In addition, the NDGA + (*)OH reaction is predicted to be diffusion-controlled. The first step of this reaction is proposed to occur mainly by a sequential electron proton transfer from NDGA to (*)OH generating a neutral radical of NDGA, which after a second oxidation step gives a diradical that after a cascade sequential complex reaction produces a cyclic compound. This cyclic product is predicted to have a UV-vis spectrum very similar to that of NDGA, making its identification by this technique very difficult. The electrochemical studies performed in water support the formation of a cyclic compound (C2) as the main product of the reaction. It is concluded that NDGA can scavenge at least two (*)OH. PMID:20415502

Galano, Annia; Macías-Ruvalcaba, Norma A; Medina Campos, Omar Noel; Pedraza-Chaverri, José

2010-05-20

135

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

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

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

2013-01-01

136

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)

137

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

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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

138

A pulse radiolysis study of the dynamics of ascorbic acid free radicals within a liposomal environment.  

Science.gov (United States)

The dynamics of free-radical species in a model cellular system are examined by measuring the formation and decay of ascorbate radicals within a liposome with pulse radiolysis techniques. Upon pulse radiolysis of an N2O-saturated aqueous solution containing ascorbate-loaded liposome vesicles, ascorbate radicals are formed by the reaction of OH(·) radicals with ascorbate in unilamellar vesicles exclusively, irrespective of the presence of vesicle lipids. The radicals are found to decay rapidly compared with the decay kinetics in an aqueous solution. The distinct radical reaction kinetics in the vesicles and in bulk solution are characterized, and the kinetic data are analyzed. PMID:25056365

Kobayashi, Kazuo; Seike, Yumiko; Saeki, Akinori; Kozawa, Takahiro; Takeuchi, Fusako; Tsubaki, Motonari

2014-10-01

139

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

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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

140

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  

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

Marie Asano

2014-08-01

 
 
 
 
141

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

Science.gov (United States)

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

Asano, Marie; Iwahashi, Hideo

2014-01-01

142

Absolute rate constants of alkoxyl radical reactions in aqueous solution  

International Nuclear Information System (INIS)

The pulse radiolysis technique was used to generate the alkoxyl radical derived from tert-butyl hydroperoxide (/sup t/BuOOH) in aqueous solution. The reactions of this radical with 2,2'-azinobis(3-ethyl-6-benzothiazolinesulfonate) (ABTS) and promethazine were monitored by kinetic spectroscopy. The unimolecular decay rate constant of the tert-butoxyl radical (/sup t/BuO) was determined to be 1.4 x 106 s-1. On the basis of this value, the rate constants for /sup t/BuO attack on quercetin, crocin, crocetin, ascorbate, isoascorbate, trolox c, glutathione, thymidine, adenosine, guanosine, and unsaturated fatty acids were determined. In addition, the reaction of /sup t/BuO with the polyunsaturated fatty acids (PUFA) was observed by directly monitoring the formation of the fatty acid pentadienyl radicals. Interestingly, the attack of /sup t/BuO on PUFA was found to be faster by about one order of magnitude as compared to the same reaction in a nonpolar solvent

143

Synthesis of Ortho Acid Ester-Type 1,3-Dioxolanofullerenes: Radical Reaction of [60]Fullerene with Halocarboxylic Acids Promoted by Lead(IV) Acetate.  

Science.gov (United States)

A lead(IV) acetate-promoted radical reaction of [60]fullerene with halocarboxylic acids has been exploited to synthesize rare ortho acid ester-type 1,3-dioxolanofullerenes, the hydroxyl group of which can be further transformed to an ester or ether group. Intriguingly, an ortho acid ester-type 1,3-dioxolanofullerene can also be converted to a 1,4-dioxanonofullerene in the presence of a base or manipulated to another ortho acid ester-type 1,3-dioxolanofullerene by reaction with a stronger halocarboxylic acid. Moreover, two possible reaction pathways leading to the observed products are also proposed. PMID:25360886

You, Xun; Li, Fa-Bao; Wang, Guan-Wu

2014-11-21

144

Free radical mediated grafting of chitosan with caffeic and ferulic acids: structures and antioxidant activity.  

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In this study, two water soluble chitosan derivatives were synthesized by grafting caffeic acid (CA) and ferulic acid (FA) onto chitosan via a free radical mediated method. The structural characterization, antioxidant activity in vitro and in vivo of chitosan derivatives were determined. Results showed that the UV-vis absorption peaks of chitosan derivatives shifted toward longer wavelengths. FT-IR spectroscopy exhibited the typical phenolic characteristics within 1450-1600 cm(-1). (1)H NMR spectroscopy showed new peaks of phenyl protons at 6.2-7.6 ppm. (13)C NMR spectroscopy showed additional peaks between 110 and 150 ppm assigned to the C=C of phenolic groups. These results all confirmed the successful grafting of CA and FA onto chitosan backbones. The chitosan derivatives had decreased thermal stability and crystallinity as compared to chitosan. In vitro assays showed that the antioxidant activity decreased in the order of CA-g-chitosan>FA-g-chitosan>chitosan. Moreover, administration of the chitosan derivatives could significantly increase antioxidant enzymes activities and decrease malondialdehyde levels in both serums and livers of d-galactose induced aging mice. Our results indicated the potential of CA-g-chitosan and FA-g-chitosan in the development of novel antioxidant agents. PMID:24444883

Liu, Jun; Wen, Xiao-yuan; Lu, Jian-feng; Kan, Juan; Jin, Chang-hai

2014-04-01

145

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)

146

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

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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

147

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

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

Hawkins, C.L.; Davies, M.J. [Heart Research Institute, Camperdown, Sydney (Australia)

1998-12-31

148

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

International Nuclear Information System (INIS)

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

149

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

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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

150

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

International Nuclear Information System (INIS)

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

151

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

152

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

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

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

2014-04-01

153

Iron-generated hydroxyl radicals kill retinal cells in vivo: effect of ferulic acid.  

Science.gov (United States)

Siderosis bulbi is vision threatening. An investigation into its mechanisms and management is crucial. Experimental siderosis was established by intravitreous administration of an iron particle (chronic) or FeSO(4) (acute). After siderosis, there was a significant dose-responsive reduction in eletroretinogram (a/b-wave) amplitude, and an increase in OH level, greater when caused by 24 mM FeSO(4) than that by 8 mM FeSO(4). Furthermore, the FeSO(4)-induced oxidative stress was significantly blunted by 100 microM ferulic acid (FA). Siderosis also resulted in an excessive glutamate release, increased [Ca(++)](i), and enhanced superoxide dismutase immunoreactivity. The latter finding was consistent with the Western blot result. Obvious disorganization including loss of photoreceptor outer segments and cholinergic amacrines together with a wide-spreading ferric distribution across the retina was present, which were related to the eletro-retinographic and pathologic dysfunctions. Furthermore, b-wave reduction and amacrine damage were respectively, significantly, dose-dependently, and clearly ameliorated by FA. Thus, siderosis stimulates oxidative stress, and possibly, subsequent excitotoxicity, and calcium influx, which explains why the retina is impaired electro-physiologically and pathologically. Importantly, FA protects iron toxicity perhaps by acting as a free radical scavenger. This provides an approach to the study and treatment of the iron-related disorders such as retained intraocular iron and Alzheimer disease. PMID:18684804

Chao, H M; Chen, Y H; Liu, J H; Lee, S M; Lee, F L; Chang, Y; Yeh, P H; Pan, W H T; Chi, C W; Liu, T Y; Lui, W Y; Ho, L T; Kuo, C D; Lin, D E; Chan, C C; Yang, D M; Lin, A M Y; Chao, F P

2008-04-01

154

Characterization of a cross-linked protein-nucleic acid substrate radical in the reaction catalyzed by RlmN.  

Science.gov (United States)

RlmN and Cfr are methyltransferases/methylsynthases that belong to the radical S-adenosylmethionine superfamily of enzymes. RlmN catalyzes C2 methylation of adenosine 2503 (A2503) of 23S rRNA, while Cfr catalyzes C8 methylation of the exact same nucleotide, and will subsequently catalyze C2 methylation if the site is unmethylated. A key feature of the unusual mechanisms of catalysis proposed for these enzymes is the attack of a methylene radical, derived from a methylcysteine residue, onto the carbon center undergoing methylation to generate a paramagnetic protein-nucleic acid cross-linked species. This species has been thoroughly characterized during Cfr-dependent C8 methylation, but does not accumulate to detectible levels in RlmN-dependent C2 methylation. Herein, we show that inactive C118S/A variants of RlmN accumulate a substrate-derived paramagnetic species. Characterization of this species by electron paramagnetic resonance spectroscopy in concert with strategic isotopic labeling shows that the radical is delocalized throughout the adenine ring of A2503, although predominant spin density is on N1 and N3. Moreover, (13)C hyperfine interactions between the radical and the methylene carbon of the formerly [methyl-(13)C]Cys355 residue show that the radical species exists in a covalent cross-link between the protein and the nucleic acid substrate. X-ray structures of RlmN C118A show that, in the presence of SAM, the substitution does not alter the active site structure compared to that of the wild-type enzyme. Together, these findings have new mechanistic implications for the role(s) of C118 and its counterpart in Cfr (C105) in catalysis, and suggest involvement of the residue in resolution of the cross-linked species via a radical mediated process. PMID:24806349

Silakov, Alexey; Grove, Tyler L; Radle, Matthew I; Bauerle, Matthew R; Green, Michael T; Rosenzweig, Amy C; Boal, Amie K; Booker, Squire J

2014-06-11

155

Nitroarachidonic acid prevents NADPH oxidase assembly and superoxide radical production in activated macrophages.  

Science.gov (United States)

Nitration of arachidonic acid (AA) to nitroarachidonic acid (AANO2) leads to anti-inflammatory intracellular activities during macrophage activation. However, less is known about the capacity of AANO2 to regulate the production of reactive oxygen species under proinflammatory conditions. One of the immediate responses upon macrophage activation involves the production of superoxide radical (O2(•-)) due to the NADPH-dependent univalent reduction of oxygen to O2(•-) by the phagocytic NADPH oxidase isoform (NOX2), the activity of NOX2 being the main source of O2(•-) in monocytes/macrophages. Because the NOX2 and AA pathways are connected, we propose that AANO2 can modulate macrophage activation by inhibiting O2(•-) formation by NOX2. When macrophages were activated in the presence of AANO2, a significant inhibition of NOX2 activity was observed as evaluated by cytochrome c reduction, luminol chemiluminescence, Amplex red fluorescence, and flow cytometry; this process also occurs under physiological mimic conditions within the phagosomes. AANO2 decreased O2(•-) production in a dose- (IC50=4.1±1.8 ?M AANO2) and time-dependent manner. The observed inhibition was not due to a decreased phosphorylation of the cytosolic subunits (e.g., p40(phox) and p47(phox)), as analyzed by immunoprecipitation and Western blot. However, a reduction in the migration to the membrane of p47(phox) was obtained, suggesting that the protective actions involve the prevention of the correct assembly of the active enzyme in the membrane. Finally, the observed in vitro effects were confirmed in an in vivo inflammatory model, in which subcutaneous injection of AANO2 was able to decrease NOX2 activity in macrophages from thioglycolate-treated mice. PMID:23318789

González-Perilli, Lucía; Álvarez, María Noel; Prolo, Carolina; Radi, Rafael; Rubbo, Homero; Trostchansky, Andrés

2013-05-01

156

Pulse radiolysis study of aqueous nitric acid solutions. Formation mechanism, yield, and reactivity of NO3 radical  

International Nuclear Information System (INIS)

A pulse radiolysis study of aqueous nitric acid and nitrate solutions has been carried out. The formation kinetics of NO3 radical was followed with nanosecond time resolution. Two formation processes of NO3 in nitric acid solutions were directly demonstrated: a fast one completed during the electron pulse and a slow one occurring in a microsecond time range. In nitrate solutions, only the fast formation process was observed. The slow formation process in nitric acid solutions was confirmed to be the reaction of OH radicals with undissociated nitric acid molecules, OH + HNO3 ? H2O + NO3, with a rate constant of (1.4 ± 0.1) x 108 M-1 s-1. The fast formation process is most probably the direct action of radiation on nitrate anion or nitric acid: NO3- (gamma radiation) ? e- + NO3 or HNO3 (gamma radiation) ? HNO3+ + e- ? NO3 + H+ + e-. The molar absorption coefficient of NO3 was evaluated as 1,300 ± 100 M-1 cm-1 at 640 nm. On the basis of this result, G values of NO3 were evaluated in nitric acid, lithium nitrate, and sodium nitrate solutions. The main decay reaction of NO3 was proposed to be NO3 + NO2 ? N2O5 in nitric acid solutions and its rate constant was evaluated as (1.7 ± 0.3) x 109 M-1 s-1. Rate constants of reactions of NO3 with radiolytic products and some other compounds were obtained

157

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

Directory of Open Access Journals (Sweden)

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

158

E.S.R. of spin-trapped radicals in aqueous solutions of 5-halo derivatives of nucleic acid constituents: reactions of hydrated electrons, hydroxyl radicals and U.V. photolysis  

International Nuclear Information System (INIS)

In order to obtain information concerning the mechanism of radio- and photosensitization due to 5-halogen substituted nucleic acid constituents, the free radicals produced in iodo-, bromo-, chloro- and fluoro-derivatives of uracil, uridine and deoxyuridine by reaction with hydrated electrons and with hydroxyl radicals and by direct U.V. photolysis have been studied by e.s.r. and spin-trapping. t-Nitrosobutane was used as the spin-trap. From 5-halogenated bases (except 5-fluorouracil) U.V. photolysis and reactions with hydrated electrons produced the uracilyl radical which was subsequently spin-trapped. When hydroxyl radical reactions were studied, the free radical at the N(1) position of the base was identified. From 5-fluorouracil U.V. photolysis generated the ?-halo radical at the C(5) position of the base. For 5-halogenated ribonucleosides and deoxyribonucleosides, free radicals located on the sugar moiety were observed for reactions with hydrated electrons, hydroxyl radicals and for U.V. photolysis. The implications of these results for understanding the mechanism of radio- and photosensitization by 5-halogenated nucleic acids are discussed. (author)

159

ENDOR evidence for inhomogeneous radical distribution in irradiated succinic acid: Sign and intensity of the signal  

International Nuclear Information System (INIS)

It was found that the ENDOR signal from a weakly interacting radical was negative while that from a relatively strongly interacting radical was positive; in crystals with very low doses, intensity of a strong negative ENDOR line was comparable with that of the original ESR line

160

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

 
 
 
 
161

Polymerization of guaiacol and a phenolic beta-O-4-substructure by Trametes hirsuta laccase in the presence of ABTS.  

Science.gov (United States)

The reaction of the monomeric lignin model compound guaiacol and the beta-O-4-type dimer erol (1-(4-hydroxy-3-methoxyphenyl)-2(2-methoxyphenoxy)-propane-1,3-diol with laccase from Trametes hirsuta was studied in the presence of the mediator ABTS (2,2'-azino-di[3ethylbenzothiazoline-6-sulfonic acid]). The product mixtures were analyzed by means of aqueous-phase size exclusion chromatography (SEC) with 50 mM NaOH as eluent. Interestingly, in the laccase-catalyzed reaction with both substrates, the mediator not only functioned as an electron carrier but underwent coupling reactions with the substrate to give polymeric coupling products. The molecular weight of these copolymeric products was significantly higher than the molecular weight of products obtained without ABTS. After ultrafiltration, 33% and 21% of the initially applied ABTS could be found in the polymeric product fraction for the substrates guaiacol and erol, respectively, on the basis of nitrogen analysis. When ABTS was added to substrates after full laccase-catalyzed polymerization, the reaction proceeded toward higher molecular weights. PMID:14524712

Rittstieg, Klaus; Suurnäkki, Anna; Suortti, Tapani; Kruus, Kristiina; Guebitz, Georg M; Buchert, Johanna

2003-01-01

162

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

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Full Text Available

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

G. L. FREITAS

2009-01-01

163

78 FR 29367 - Access to Confidential Business Information by ABT Associates, Incorporated; Perry Johnson...  

Science.gov (United States)

...Business Information by ABT Associates, Incorporated; Perry Johnson Registrars, Inc.; SGS North America, Inc.; SAI Global...Incorporated (ABT) and six (6) auditing organizations: Perry Johnson Registrars, Inc.; SGS North America, Inc.; SAI...

2013-05-20

164

E.s.r. of spin-trapped radicals in aqueous solutions of deuterated amino acids and alcohols  

International Nuclear Information System (INIS)

Selectively deuterated compounds can be utilized in spin-trapping to obtain conclusive evidence for the structures of the trapped radicals. Radicals formed from DL-alanine-2-d1, DL-alanine-3,3,3-d3, DL-alanine-d4, glycine-d5, isopropyl-2-d1 alcohol, isopropyl-d7 alcohol and t-butyl-d9 alcohol were studied. The hydrogen abstraction, deamination and decarboxylation radicals generated from deuterated alanines were investigated by spin-trapping using t-nitrosobutane. Since nitroxides of the type XYZC-CH2-N(O)-tBu which contain an asymmetric centre next to the CH2 group exhibit unequal ?-proton splittings and temperature-dependent line width alternations, the effects of temperature on the e.s.r. spectra were studied. By these methods the structures of the trapped radicals were verified and the hyperfine coupling constants could be assigned without ambiguity. In ?-irradiated polycrystalline amino acids, the observed deuterium exchange can be conveniently surveyed by dissolution in aqueous solutions containing t-nitrosobutane. (author)

165

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

166

Free radical scavenging activity of Kielmeyera variabilis (Clusiaceae).  

Science.gov (United States)

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 (IC?? 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-?-glucoside (3), and quercetin-3-O-?-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. PMID:23429348

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

2013-01-01

167

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

168

Spectroscopic studies on the antioxidant activity of p-coumaric acid  

Science.gov (United States)

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

Kiliç, Ismail; Ye?ilo?lu, Ye?im

2013-11-01

169

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

Scientific Electronic Library Online (English)

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

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

1196-12-01

170

Amino Acid Changes in Disease-Associated Variants Differ Radically from Variants Observed in the 1000 Genomes Project Dataset  

Science.gov (United States)

The 1000 Genomes Project data provides a natural background dataset for amino acid germline mutations in humans. Since the direction of mutation is known, the amino acid exchange matrix generated from the observed nucleotide variants is asymmetric and the mutabilities of the different amino acids are very different. These differences predominantly reflect preferences for nucleotide mutations in the DNA (especially the high mutation rate of the CpG dinucleotide, which makes arginine mutability very much higher than other amino acids) rather than selection imposed by protein structure constraints, although there is evidence for the latter as well. The variants occur predominantly on the surface of proteins (82%), with a slight preference for sites which are more exposed and less well conserved than random. Mutations to functional residues occur about half as often as expected by chance. The disease-associated amino acid variant distributions in OMIM are radically different from those expected on the basis of the 1000 Genomes dataset. The disease-associated variants preferentially occur in more conserved sites, compared to 1000 Genomes mutations. Many of the amino acid exchange profiles appear to exhibit an anti-correlation, with common exchanges in one dataset being rare in the other. Disease-associated variants exhibit more extreme differences in amino acid size and hydrophobicity. More modelling of the mutational processes at the nucleotide level is needed, but these observations should contribute to an improved prediction of the effects of specific variants in humans. PMID:24348229

de Beer, Tjaart A. P.; Laskowski, Roman A.; Parks, Sarah L.; Sipos, Botond; Goldman, Nick; Thornton, Janet M.

2013-01-01

171

?-Alkynyl lipid surrogates for polyunsaturated fatty acids: free radical and enzymatic oxidations.  

Science.gov (United States)

Lipid and lipid metabolite profiling are important parameters in understanding the pathogenesis of many diseases. Alkynylated polyunsaturated fatty acids are potentially useful probes for tracking the fate of fatty acid metabolites. The nonenzymatic and enzymatic oxidations of ?-alkynyl linoleic acid and ?-alkynyl arachidonic acid were compared to that of linoleic and arachidonic acid. There was no detectable difference in the primary products of nonenzymatic oxidation, which comprised cis,trans-hydroxy fatty acids. Similar hydroxy fatty acid products were formed when ?-alkynyl linoleic acid and ?-alkynyl arachidonic acid were reacted with lipoxygenase enzymes that introduce oxygen at different positions in the carbon chains. The rates of oxidation of ?-alkynylated fatty acids were reduced compared to those of the natural fatty acids. Cyclooxygenase-1 and -2 did not oxidize alkynyl linoleic but efficiently oxidized alkynyl arachidonic acid. The products were identified as alkynyl 11-hydroxy-eicosatetraenoic acid, alkynyl 11-hydroxy-8,9-epoxy-eicosatrienoic acid, and alkynyl prostaglandins. This deviation from the metabolic profile of arachidonic acid may limit the utility of alkynyl arachidonic acid in the tracking of cyclooxygenase-based lipid oxidation. The formation of alkynyl 11-hydroxy-8,9-epoxy-eicosatrienoic acid compared to alkynyl prostaglandins suggests that the ?-alkyne group causes a conformational change in the fatty acid bound to the enzyme, which reduces the efficiency of cyclization of dioxalanyl intermediates to endoperoxide intermediates. Overall, ?-alkynyl linoleic acid and ?-alkynyl arachidonic acid appear to be metabolically competent surrogates for tracking the fate of polyunsaturated fatty acids when looking at models involving autoxidation and oxidation by lipoxygenases. PMID:25034362

Beavers, William N; Serwa, Remigiusz; Shimozu, Yuki; Tallman, Keri A; Vaught, Melissa; Dalvie, Esha D; Marnett, Lawrence J; Porter, Ned A

2014-08-13

172

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.

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

2014-01-01

173

Comparative studies of enhanced iron-mediated production of hydroxyl radical by glutathione, cysteine, ascorbic acid, and selected catechols.  

Science.gov (United States)

A sensitive electrochemical detection system was employed together with a specific salicylate hydroxylation assay to comparatively assess the effects of various substances on the iron-mediated generation of the hydroxyl radical (.OH). Hydroxyl radical production was found to be enhanced significantly by reduced glutathione, cysteine, ascorbic acid, and selected catechols, but not by mannitol, melatonin or tyramine. The data showed that over the range of concentrations examined, the augmented effects were linearly proportional to the amount of added reductant for a given amount of iron in the system. The pro-oxidant activity of thiols and ascorbate reduced and recycled iron providing both hydrogen peroxide (H2O2) and catalytic ferrous ions for augmented .OH production by the Fenton reaction. The enhanced production of .OH by catechols resulted from their oxidation either by molecular oxygen or ferric ions, with the accompanying formation of semiquinones, superoxide anion and H2O2. These data caution against therapeutic applications of thiols and ascorbate for ameliorating oxy-radical-induced tissue damage in environments where free redox-active metal ions may be present to function both as foci for site-specific peroxidative activity, and as catalysts to promote the pro-oxidant properties of certain endogenous reductants, thereby elevating rather than diminishing .OH levels. PMID:9305802

Nappi, A J; Vass, E

1997-08-29

174

The Effect of Nitrate as a Radical Scavenger for the Removal of Humic Acid from Aqueous Solutions by Electron Beam Irradiation  

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Introduction: Humic acids have adverse effects on the water quality, then should be removed from water resources. The aim of this study was to evaluate the effect of nitrate as a radical scavenger for removal of humic acid from aqueous solutions by electron beam irradiation. Materials and Methods: In this study, after preparation of stock humic acid solution in alkaline condition, different concentrations of humic acid (10, 25 and 50 mg/l) were prepared. Different concentrations of nitrate (2...

Mohammad Taghi Ghaneian; Mohammad Hassan Ehrampoush; Tahereh Jasemizad; Monireh Kheirkha; Reza Amraei; Fatemeh Sahlabadi

2013-01-01

175

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1987-04-23

176

Neuroprotective and free radical scavenging activities of phenolic compounds from Hovenia dulcis.  

Science.gov (United States)

The EtOAc-soluble fraction from a methanolic extract of Hovenia dulcis Thunb. exhibited neuroprotective activity against glutamate-induced neurotoxicity in mouse hippocampal HT22 cells. The neuroprotective activity-guided isolation resulted in 8 phenolic compounds (1-8), such as vanillic acid (1), ferulic acid (2), 3,5-dihydroxystilbene (3), (+)-aromadendrin (4), methyl vanillate (5), (-)-catechin (6), 2,3,4-trihydrobenzoic acid (7), and (+)-afzelechin (8). Among these, compounds 6 and 8 had a neuroprotective effect on the glutamate-induced neurotoxicity in HT22 cells. Furthermore, compound 6 had a DPPH free radical scavenging effect with an IC50 value of 57.7 microM, and a superoxide anion radical scavenging effect with an IC50 value of 8.0 microM. Both compounds 6 and 8 had ABTS cation radical scavenging effects with IC50 values of 7.8 microM and 23.7 microM, respectively. These results suggest that compounds 6 and 8 could be neuroprotectants owing to their free radical scavenging activities. PMID:16114495

Li, Gao; Min, Byung-Sun; Zheng, Changji; Lee, Joongku; Oh, Sei-Ryang; Ahn, Kyung-Seop; Lee, Hyeong-Kyu

2005-07-01

177

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

178

Products of the radical initiated oxidation of model solid and liquid organic acid particles in simulated "clean" and "polluted" environments.  

Science.gov (United States)

Using a flow tube reactor coupled to a chemical ionization mass spectrometer, the Cl-initiated oxidation of solid and supercooled liquid organic acid particles were investigated at 293 K. In creating aerosols of species which are able to be supercooled or solid at room temperature, it is possible to distinguish the effect of phase on particle reactivity and product formation. In a clean atmosphere, where there are negligible concentrations of NOx, the primary fate of peroxy radicals (formed from H-abstraction by Cl and OH radicals in the presence of O2) are their reactions to form ketone and alcohol products. These products are then able to undergo further oxidation to form multiply oxidized products. The formation of low-molecular weight volatile species may also be important in the oxidative aging of organic aerosols, however neither the mechanism of their formation nor their formation yields are well understood. We have shown that, for equivalent Cl exposures, more multiply-oxidized species as well as more low-molecular-weight species were created from the oxidation of solid particles than from liquid particles. The findings from these studies suggest that slower diffusion of the oxidation products in solid particles confines them to the surface where they continue to react with Cl radicals producing more-highly- functionalized products which may decompose more readily. By introducing nitric oxide to the flow tube reaction system, we show that in a polluted atmosphere, where NOx is present in significant concentrations, organic nitrate formation may become important on the surface of solid particles but not liquid particles as the RO2 are confined to the surface of solid particles (causing a enhanced localized concentration of RO2) where they may then react with ambient nitric oxide through the reaction RO2 + NO ? RO2NO* ? RONO2. These experiments of these model systems indicate that particle phase could be important in determining how organic aerosols evolve chemically through radical-initiated oxidation in the atmosphere.

Renbaum, L. H.; Smith, G. D.

2009-05-01

179

Radical-Scavenging Compounds from Olive Tree (Olea europaea L.) Wood.  

Science.gov (United States)

The purpose of this study was to complete knowledge on the chemical composition and radical-scavenging activity of olive tree wood. Two new monoterpene glycosides, (-)-oleuropeic acid 6'-O-?-d-glucopyranosyl ester (6a) and (-)-perillic acid 1'-O-?-d-primeverosyl ester (8), together with the known compounds (-)-oleuropeic acid (1), (-)-olivil (2), the aldehydic form of oleuropein aglycone (3), (+)-1-hydroxypinoresinol 1-O-?-d-glucopyranoside (4), (-)-oleuropeic acid 1'-O-?-d-glucopyranosyl ester (5), (-)-oleuropeic acid 6'-O-?-d-glucopyranosyl ester (6b), and (-)-olivil 4-O-?-d-glucopyranoside (7) were isolated from an ethyl acetate extract. The radical scavengers found (2-4 and 7) were detected and isolated with the help of the online HPLC-DAD-DPPH/ABTS technique. Compounds 2-4 and 7 displayed a higher antioxidative effect against the free radical DPPH than the reference BHT and lower than hydroxytyrosol, whereas compounds 1, 5, 6a, 6b, and 8 showed no activity. PMID:24328093

Pérez-Bonilla, Mercedes; Salido, Sofía; van Beek, Teris A; Altarejos, Joaquín

2014-01-01

180

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2012-01-01

 
 
 
 
181

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 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

182

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2005-04-11

183

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-05-15

184

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.

Sehested, Knud; Holcman, Jerzy

2010-01-01

185

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)

186

Antioxidant and radical scavenging activities of chamazulene.  

Science.gov (United States)

Essential oils (EOs) of chamomile contain several bioactive compounds, including monoterpenes, sesquiterpenes, triterpenes and fatty acids. Hydrodistillation of chamomile EO induces the formation of chamazulene, a bioactive compound. Chamazulene was isolated from the EO by column chromatography. The total antioxidant capacity confirmed a higher antioxidant activity of chamazulene (IC50 = 6.4 ?g mL(- 1)) than of ascorbic acid (IC50 = 12.8 ?g mL(- 1)), ?-tocopherol (IC50 = 20.5 ?g mL(- 1)) and of butylated hydroxytoluene (BHT) (IC50 = 30.8 ?g mL(- 1)). Chamazulene was unable to react with DPPH?. However, when chamazulene was assayed with ABTS?, a strong and significantly (P < 0.05) higher free radical scavenging activity was observed (IC50 = 3.7 ?g mL(- 1)), with respect to BHT (IC50 = 6.2 ?g mL(- 1)) and ?-tocopherol (IC50 = 11.5 ?g mL(- 1)). The results of this work show that chamazulene is an important factor for the antioxidant power of chamomile oil. PMID:24980540

Capuzzo, Andrea; Occhipinti, Andrea; Maffei, Massimo E

2014-12-01

187

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

188

Antioxidant and anti-inflammatory activities of methanol extracts of Tremella fuciformis and its major phenolic acids.  

Science.gov (United States)

Methanol extract subfractions of the edible white jelly mushroom (Tremella fuciformis), were assessed for the following antioxidant properties: ABTS(+) radical scavenging activity, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, and inhibitory activity of human low-density lipoprotein (LDL) oxidation. Among the subfractions tested, the chloroform subfraction exhibited the strongest antioxidant activity, with the highest total phenolic content (66.31 ?g CAE/mg extract) and flavonoids content (5.12 ?g QE/mg extract). The ABTS(+) radical scavenging activity of the chloroform subfraction was 7.89 ?mol trolox/mg extract, which was the highest among all subfractions. This subfraction also showed the highest DPPH radical scavenging activity and inhibitory activity of LDL oxidation. In addition, the chloroform subfraction demonstrated anti-inflammatory activity through inhibition of nitric oxide production and inducible nitric oxide synthase expression in RAW 264.7 cells. Major phenolic acids from the mushroom extract were identified as 4-hydroxybenzoic acid (323 mg/kg dry weight of mushroom), gentisic acid (174 mg/kg dry weight of mushroom), and 4-coumaric acid (30 mg/kg dry weight of mushroom). PMID:24547933

Li, Hua; Lee, Hee-Seok; Kim, Su-Hwan; Moon, BoKyung; Lee, Chan

2014-04-01

189

Oxidation by a reagent H2O2-vanadium complex-pyrazine-2-carboxylic acid. 3. Evidence for hydroxyl radical formation  

International Nuclear Information System (INIS)

Evidence for the formation of hydroxyl radicals and their participation in the hydrocarbon oxidation by a reagent H2O2-vanadium complex-pyrazine-2-carboxylic acid has been obtained by two different routes: by the application of spin trapping and kinetically by the competitive oxidation of a mixture benzene-aliphatic alcohol. The suggestion has been made that the hydroxyl radicals generate in the reaction of vanadium complex (Bu4N)VO3 with hydrogen peroxide. 22 refs.; 1 fig

190

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-01-15

191

Radical-mediated degradation mechanisms of tribomo- and other trihalogenated acetic acids in oxygen-free solutions as studied by radiation chemistry methods  

International Nuclear Information System (INIS)

.CBr2CO2- and .CCl2CO2- radicals, generated upon one electron reduction of tribromo-and trichloro-acetic acids and .CF2CO2- radicals produced from difluoroacetic acid by reaction with .OH, exhibit optical absorptions in the UV with ?max at 290 nm (? = 2580 dm3 mol-1 cm-1), 330 nm (? 3000 dm3 mol-1 cm-1) and 310 nm (? ? 660 dm3 mol-1 cm-1), respectively. Mechanistically, the present report focuses on the free-radical-induced degradation of tribomoacetic acid. Absolute rate constants have been determined for the reactions of CBr3CO2- with eaq-, H., CO2.-, .CH2OH, CH3.CHOH, (CH3)2) .COH and .CH3 radicals to be ? = 1.8 x 1010, 1.5 x 1010, 2.8 x 109, 1.6 x 109, 2.3 x 109, 3.0 x 109 and 3.0 x 107 dm3 mol-1 s-1, respectively. The major fate of .CBr2CO2- is self-termination to yield tetrabromosuccinic acid which, however, is unstable and thermally decomposes to HBr, CO2 and tribomoacrylic acid. Dibromofumaric acid, dibromomaleic acid and carbon monoxide were found as minor secondary products, formation of which is explained by a small yield of reductive decomposition of the transient tetrabromosuccinic acid. A complete and mechanistically satisfying material balance is provided for several systems in which CBr3CO2- has been degraded via a variety of radicals under various conditions. .OH Radicals do not react directly with CBr3CO2-. They have been shown, however, to contribute indirectly to the degradation of this acid via their reaction with reductively liberated bromide ions. The Br. atoms formed in this process are considered to abstract a bromine atom from CBr3CO2- or oxidize the carboxyl function in a one-electron transfer process. The formation of free Br. atoms has been recognized by pulse radiolysis through their conjugate dimer radical anions Br2.-. With respect to the other trihalogenated acids it is noteworthy that CCl3CO2- is efficiently reduced by CO2.- radicals and that CF3- exhibits a high stability toward ?-irradiation and practically resists any reductive attack. (author)

192

Radical Scavenging Activity of the Essential Oil of Silver Fir (Abies alba)  

Science.gov (United States)

The essential oil of silver fir (Abies alba) is known to help respiratory system and have easing and soothing effect for muscle. In the present study, we investigated the chemical composition, cytotoxicity and its biological activities of silver fir (Abies alba) essential oil. The composition of the oil was analyzed by GC-MS and bornyl acetate (30.31%), camphene (19.81%), 3-carene (13.85%), tricyclene (12.90%), dl-limonene (7.50%), ?-pinene (2.87%), caryophyllene (2.18%), ?-phellandrene (2.13%), borneol (1.74%), bicyclo[2.2.1]hept-2-ene,2,3-dimethyl (1.64%) and ?-terpinene (1.24%) were the major components in the oil. The results tested by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay indicated that the oil showed no cytotoxic effect, at concentrations of 1 and 5%, for as long as 24 and 3 h, respectively. The antiradical capacity was evaluated by measuring the scavenging activity of the essential oil on the 2,20-diphenylpicrylhydrazyl (DPPH) and 2,2'-azino-bis 3-ethyl benzothiazoline-6-sulfonic acid (ABTS) radicals. The oil was able to reduce the both radicals dose-dependently, and the concentration required for 50% reduction (RC50) against DPPH radicals (2.7 ± 0.63%) was lower than ABTS radicals (8.5 ± 0.27%). The antibacterial activity of the oil was also evaluated using disc diffusion method against Staphylococcus aureus, Streptococcus mutans, Listeria monocytogenes, Acinetobacter baumannii, Escherichia coli, and Vibrio parahaemolyticcus. The oil exhibited no antibacterial activity against all the bacterial strains tested except S. aureus of mild activity. PMID:19430614

Yang, Seun-Ah; Jeon, Sang-Kyung; Lee, Eun-Jung; Im, Nam-Kyung; Jhee, Kwang-Hwan; Lee, Sam-Pin; Lee, In-Seon

2009-01-01

193

Superoxide- and 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activities of soyasaponin beta g related to gallic acid.  

Science.gov (United States)

Soyasaponin beta p g at 1 mm had 8% scavenging activity for O2-, and 25 microM beta g scavenged 20.9% for the DPPH radical (IC50: 63.8 microM). In the soyasaponin beta g-gallic acid system, synerigistic effects were observed at a low level of gallic acid concentration. The spin density distribution calculated by the MNDO/AM1 method showed unpaired electron localization on the carbons at C-4 and C-6, and on the ketone group at C-4 of the DDMP moiety. Furthermore, for soyasaponin beta g, the MNDO/AM1 method gave an ionization potential of 8.38 eV, electron affinity of 1.16 eV and Mulliken electronegativity of 4.77 eV. Based on this evidence, the synergistic antiradical effects of the soyasaponin beta g-gallic acid system are assumed to involve two-electron reduction from gallic acid. PMID:11758904

Yoshiki, Y; Kahara, T; Okubo, K; Sakabe, T; Yamasaki, T

2001-10-01

194

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

195

Population Analyses of Efficacy and Safety of ABT-594 in Subjects with Diabetic Peripheral Neuropathic Pain  

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ABT-594, a neuronal nicotinic acetylcholine receptor ligand, is 30- to 100-fold more potent than morphine in animal models of nociceptive and neuropathic pain. Efficacy and safety of ABT-594 in subjects with painful diabetic polyneuropathy was evaluated in a phase 2 study. The objective of this work was to use a nonlinear mixed effects model-based approach for characterizing the relationship between dose and response (efficacy and safety) of ABT-594. Subjects (N?=?266) were randomized int...

Dutta, Sandeep; Hosmane, Balakrishna S.; Awni, Walid M.

2012-01-01

196

[Therapeutic evaluation of the polylactic acid gel (PLA-G) used for preventing skin flap adhesion in modified radical mastectomy].  

Science.gov (United States)

The present preliminary study was to observe the feasibility of the use of polylactic acid gel (PLA-G) in modified radical mastectomy and the ability of the PLA-G in the prevention of flap adhesion after operation. Sixty-eight patients were diagnosed with breast cancer, and received modified radical mastectomy from Jan. 2004 to Dec. 2006. The patients were divided randomly into a treatment group and a control group (with 34 cases each). The PLA-G was used under the surface of the auxiliary operative wound in the treatment group, and nothing was used in the control group. The wound healing, the wound complication, the amount of drainage solution, the indwelling time of the drainage tube and the auxiliary skin adhesion were evaluated after operation in both groups. There were no statistical difference on wound healing between the first intension (29:27) and the second intention (5:7), and the wound dehiscence after taking the stitches out (0:0) between the two intensions, the hematoma (0:1) and the effusion of the wound (5:6), and the flap necrosis (1:2) between two groups. There were also no statistical difference on the amount of drainage solution per day (6 +/- 3) and indwelling time of the drainage tube (6 +/- 4) after operation between the two groups (P > 0.5). After the operation, the case load with no flap adhesion in the treatment group was significant higher compared with the control group (22:8). The case load with complete acquired skin flap adhesion in the treatment group was visibly lower than in the control group (3:19), which proved that there was a significant statistical difference between the two groups (P < 0.05). This study suggested that the using of PLA-G in the breast cancer modified radical mastectomy could prevent skin flap adhesion without any harmful effects in the wound healing. PMID:24645611

Chen, Guojing; Liu, Tao

2013-12-01

197

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

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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

198

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

199

Surgery: a radical approach to severe hydrofluoric acid burns. A case report.  

Science.gov (United States)

Generally, chemical burns of the skin, both acid and caustic, are best treated initially by irrigating with copious amounts of water. Subsequently the burn is managed as one would treat a thermal burn. An exception may exist when skin burn is caused by hydrofluoric acid (HF), especially in its anhydrous form. HF is a commonly used catalyst in the petrochemical industry. The following report concerns a life-threatening burn from anhydrous HF. PMID:3230434

Buckingham, F M

1988-11-01

200

Identification of essential amino-acid residues in Azotobacter vinelandii isocitrate dehydrogenase by radical anions and H atoms  

International Nuclear Information System (INIS)

Pure TPN+-specific isocitrate dehydrogenase from Azotobacter vinelandii was irradiated with H atoms generated in a ?-irradiated solution at pH 6.5. A G(-activity) = 0.12 +- 0.01 was found. At the same time no corresponding loss in free sulfhydryls was observed. These results confirmed the essentiality of methionine for the enzymatic activity as known from previous studies. Irradiation with the radical anions, (CNS)2- and Br2- generated in ?-irradiated solutions at pH 6.5, strongly inactivated isocitrate dehydrogenase with yields of G(-activity) of 2.1 and 3.9, respectively. Part of the inactivating effect, however, is due to oxidation of sulfhydryl groups. These results lead to the conclusion that tryptophan is an essential amino-acid residue to isocitrate dehydrogenase from A. vinelandii. The presence of tryptophan in the enzyme was demonstrated by pulse radiolysis

 
 
 
 
201

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

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

Bhujbal Akshay

2011-05-01

202

Copper-catalyzed atom transfer radical addition (ATRA) and cyclization (ATRC) reactions in the presence of environmentally benign ascorbic acid as a reducing agent.  

Science.gov (United States)

In recent years, copper-catalyzed atom transfer radical addition (ATRA) has emerged as a viable organic procedure for the formation of carbon-carbon bonds starting from alkyl halides and alkenes. Studies have primarily focused on the use of free-radical initiators to regenerate the copper(I) complex or activator in situ. Although these initiators led to a significant decrease in the amount of metal catalyst, they were much less effective for highly active alkenes that readily undergo free-radical polymerization. In this study, the non-radical reducing agent ascorbic acid (commonly known as Vitamin C) was effectively employed resulting in TONs as high as 15,200 in the homogenous ATRA of polyhalogenated compounds to ?-olefins, and enabling selective monoadduct formation for highly active alkenes such as acrylonitrile (TONs as high as 11,800). As low as 7-20 mol% of ascorbic acid relative to substrate was sufficient for all ATRA and ATRC reactions examined. Further, product isolations for all selected syntheses were quite facile and nearly quantitative, requiring only simple liquid-liquid extraction techniques. Reactions in the presence of ascorbic acid were also examined kinetically via (1)H NMR and UV/Vis spectroscopy. A half order rate dependence on reducing agent concentration was observed, but the first order kinetic plots became nonlinear as the concentration of ascorbic acid was increased. Finally, the use of ascorbic acid circumvented otherwise necessary purging techniques, successfully furthering the utility of these reactions in organic synthesis. PMID:20981391

Taylor, Matthew J W; Eckenhoff, William T; Pintauer, Tomislav

2010-12-21

203

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

Science.gov (United States)

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

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

2008-01-01

204

Non-extractable procyanidins and lignin are important factors in the bile acid binding and radical scavenging properties of cell wall material in some fruits.  

Science.gov (United States)

The cell wall components and the food functions of alcohol-insoluble solids (AIS) of Chinese quince, quince, hawthorn, apple, pear and blueberry fruits were analyzed. Chinese quince contained characteristically high contents of cellulose, lignin, and non-extractable procyanidins (NEPCs). On the other hand, the quince AIS contained the highest proportion of NEPCs, the highest mean degree of polymerization (mDP), the strongest radical scavenging activity, and strong bile acid binding activity. In fruit AIS, the lignin and NEPC contents both showed positive correlations with the bile acid binding and radical scavenging activities. The value for mDP × NEPC content was a good index for the radical scavenging activity. The results suggest that highly polymerized NEPCs and lignin are important factors of cell wall components of fruits to having a high functionality, and Chinese quince and quince are interesting fruits from this view point. PMID:21243435

Hamauzu, Yasunori; Mizuno, Yukari

2011-03-01

205

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  

International Nuclear Information System (INIS)

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 ?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

206

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

Science.gov (United States)

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

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

2013-03-01

207

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

208

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

209

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2002-01-01

210

The action of peroxyl radicals, powerful deleterious reagents, explains why neither cholesterol nor saturated Fatty acids cause atherogenesis and age-related diseases.  

Science.gov (United States)

Cells respond to alterations in their membrane structure by activating hydrolytic enzymes. Thus, polyunsaturated fatty acids (PUFAs) are liberated. Free PUFAs react with molecular oxygen to give lipid hydroperoxide molecules (LOOHs). In case of severe cell injury, this physiological reaction switches to the generation of lipid peroxide radicals (LOO(.) ). These radicals can attack nearly all biomolecules such as lipids, carbohydrates, proteins, nucleic acids and enzymes, impairing their biological functions. Identical cell responses are triggered by manipulation of food, for example, heating/grilling and particularly homogenization, representing cell injury. Cholesterol as well as diets rich in saturated fat have been postulated to accelerate the risk of atherosclerosis while food rich in unsaturated fatty acids has been claimed to lower this risk. However, the fact is that LOO(.) radicals generated from PUFAs can oxidize cholesterol to toxic cholesterol oxides, simulating a reduction in cholesterol level. In this review it is shown how active LOO(.) radicals interact with biomolecules at a speed transcending usual molecule-molecule reactions by several orders of magnitude. Here, it is explained how functional groups are fundamentally transformed by an attack of LOO(.) with an obliteration of essential biomolecules leading to pathological conditions. A serious reconsideration of the health and diet guidelines is required. PMID:25318456

Spiteller, Gerhard; Afzal, Mohammad

2014-11-10

211

The effect of thermal and ultrasonic treatment on amino acid composition, radical scavenging and reducing potential of hydrolysates obtained from simulated gastrointestinal digestion of cowpea proteins.  

Science.gov (United States)

The effect of thermal and ultrasonic treatment of cowpea proteins (CP) on amino acid composition, radical scavenging and reducing potential of hydrolysates (CPH) obtained from in vitro simulated gastrointestinal digestion of CP was evaluated. Hydrolysis of native and treated CP with gastrointestinal pepsin and pancreatin yielded CPH that displayed antioxidant activities based on oxygen radical scavenging capacity (ORAC), ferric reducing antioxidant power (FRAP) and superoxide radical scavenging activity (SRSA). CPH derived from the treated CP yielded higher ORAC values than CPH from untreated proteins. However, lower significant FRAP and SRSA values were observed for these samples compared to untreated CPH (p?acid analysis indicated that CP processing decreased total sulphur-containing amino acids in the hydrolysates, particularly cysteine. The amount of cysteine appeared to be positively related to FRAP and SRSA values of CPH samples, but not ORAC. The results indicated that thermal and ultrasonic processing of CP can reduce the radical scavenging and reducing potential of the enzymatic hydrolysates possibly due to the decreased amounts of cysteine. Since the hydrolysates were generated with gastrointestinal enzymes, it is possible that the resulting compounds are produced to exert some health functions during normal consumption of cowpea. PMID:23354934

Quansah, Joycelyn K; Udenigwe, Chibuike C; Saalia, Firibu K; Yada, Rickey Y

2013-03-01

212

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

213

Self-catalyzed syntheses, structural characterization, DPPH radical scavenging-, cytotoxicity-, and DFT studies of phenoxyaliphatic acids of 1,8-dioxo-octahydroxanthene derivatives  

Science.gov (United States)

One-pot, in-water syntheses of phenoxyaliphatic acids of 1,8-dioxo-octahydroxanthene derived from dimedone and formylphenoxyaliphatic acids are reported. Geometries of compounds 2b, 2c, and 5a have been examined crystallographically. The synthesized compounds showed better DPPH radical scavenging activity and cytotoxicity against A431 cancer cell line. The molecular properties of all synthesized xanthenes have been investigated using single crystal XRD and DFT method. Self-catalyzed Bronsted-Lowry acid catalytic behavior was also investigated by both experimental and theoretical methods.

Suresh Kumar, G. S.; Antony Muthu Prabhu, A.; Seethalashmi, P. G.; Bhuvanesh, N.; Kumaresan, S.

2014-02-01

214

Chemistry of free radical-induced damage of deoxyribonucleic acid model compounds  

International Nuclear Information System (INIS)

The main objective of this investigation was to identify the principal lesions produced by ionizing radiation and autoxidation processes in DNA model compounds. Synthetic deoxynuclei acid oligomers were subjected to ionizing radiation in aqueous solutions. The damage products of d(ApT) irradiated under N2O saturation were isolated by reverse phase high performance liquid chromatography in different solvent systems. The major components of the HPLC profile were studied mainly by proton Nuclear Magnetic Resonance spectroscopy. The product profile was dramatically altered when mediators such as oxygen were present. One product, identified as a N-formamido derivative of d(ApT), formed due to the breakdown of the thymine base, was predominant. The presence of radiation protectors markedly altered the products obtained from d(ApT). Two stereoisomers of dihydrothymine derivatives were identified. d(ApT) irradiated in the solid state generated direct damage products which were isolated by HPLC and identified by NMR spectroscopy. A comparative study of the degradation of d(ApT) produced by ionizing radiation and by chemical degradation by autoxidizing agents was carried out. The result showed that the autoxidizing agents produced the same profile of damaged products as ionizing radiation with oxygen present

215

ABT-378, a highly potent inhibitor of the human immunodeficiency virus protease.  

Science.gov (United States)

The valine at position 82 (Val 82) in the active site of the human immunodeficiency virus (HIV) protease mutates in response to therapy with the protease inhibitor ritonavir. By using the X-ray crystal structure of the complex of HIV protease and ritonavir, the potent protease inhibitor ABT-378, which has a diminished interaction with Val 82, was designed. ABT-378 potently inhibited wild-type and mutant HIV protease (Ki = 1.3 to 3.6 pM), blocked the replication of laboratory and clinical strains of HIV type 1 (50% effective concentration [EC50], 0.006 to 0.017 microM), and maintained high potency against mutant HIV selected by ritonavir in vivo (EC50, 50-fold after 8 h. In healthy human volunteers, coadministration of a single 400-mg dose of ABT-378 with 50 mg of ritonavir enhanced the area under the concentration curve of ABT-378 in plasma by 77-fold over that observed after dosing with ABT-378 alone, and mean concentrations of ABT-378 exceeded the EC50 for >24 h. These results demonstrate the potential utility of ABT-378 as a therapeutic intervention against AIDS. PMID:9835517

Sham, H L; Kempf, D J; Molla, A; Marsh, K C; Kumar, G N; Chen, C M; Kati, W; Stewart, K; Lal, R; Hsu, A; Betebenner, D; Korneyeva, M; Vasavanonda, S; McDonald, E; Saldivar, A; Wideburg, N; Chen, X; Niu, P; Park, C; Jayanti, V; Grabowski, B; Granneman, G R; Sun, E; Japour, A J; Leonard, J M; Plattner, J J; Norbeck, D W

1998-12-01

216

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

Science.gov (United States)

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

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

2013-12-01

217

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

Directory of Open Access Journals (Sweden)

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

218

Salivary thiocyanate/nitrite inhibits hydroxylation of 2-hydroxybenzoic acid induced by hydrogen peroxide/Fe(II) systems under acidic conditions: possibility of thiocyanate/nitrite-dependent scavenging of hydroxyl radical in the stomach.  

Science.gov (United States)

Formation of OH radicals in the stomach is possible by Fenton-type reactions, as gastric juice contains ascorbic acid (AA), iron ions and H2O2. An objective of the present study is to elucidate the effects of salivary SCN- and NO2- on the hydroxylation of salicylic acid which was induced by H2O2/Fe(II) and AA/H2O2/Fe(II) systems. Thiocyanate ion inhibited the hydroxylation of salicylic acid by the above systems in acidic buffer solutions and in acidified saliva. The inhibition by SCN- was deduced to be due to SCN- -dependent scavenging of OH radicals. Nitrite ion could enhance the SCN- -dependent inhibition of the hydroxylation induced by AA/H2O2/Fe(II) systems. The enhancement was suggested to be due to scavenging of OH radicals by NO which was formed by the reactions among AA, HNO2 and SCN- contained in the reaction mixture. The concentrations of SCN- and NO2-, which were effective for the inhibition, were in ranges of their normal salivary concentrations. These results suggest that salivary SCN- can cooperate with NO2- to protect stomach from OH radicals formed by AA/H2O2/Fe(II) systems under acidic conditions. PMID:15535976

Takahama, Umeo; Oniki, Takayuki

2004-11-18

219

EPR study of the astaxanthin n-octanoic acid monoester and diester radicals on silica-alumina.  

Science.gov (United States)

The radical intermediates of the n-octanoic monoester and n-octanoic diester of astaxanthin were detected by pulsed EPR measurements carried out on the UV-produced radicals on silica-alumina artificial matrix and characterized by density functional theory (DFT) calculations. Previous Mims ENDOR for astaxanthin detected the radical cation and neutral radicals formed by proton loss from the C3 (or C3') position and from the methyl groups. Deprotonation of the astaxanthin neutral radical formed at the C3 (or C3') position resulted in a radical anion. DFT calculations for astaxanthin showed that the lowest energy neutral radical forms by proton loss at the C3 (or C3') position of the terminal ring followed by proton loss at the methyl groups of the polyene chain. Contrary to astaxanthin where proton loss can occur at either end of the symmetrical radical, for the diester of astaxanthin, this loss is prevented at the cyclohexene ends and is favored for its methyl groups. The monoester of astaxanthin, however, allows formation of the neutral radical at C3' and prevents its formation at the opposite end where the ester group is attached. At the terminal ring without the ester group attached, migration of proton from hydroxyl group to carbonyl group facilitates resonance stabilization, similarly to already published results for astaxanthin. However, cw EPR shows no evidence of a monoester radical anion formed. This study suggests the different radicals of astaxanthin and its esters that would form in a preferred environment, either hydrophobic or hydrophilic, depending on their structure. PMID:23039790

Focsan, A Ligia; Bowman, Michael K; Shamshina, Julia; Krzyaniak, Matthew D; Magyar, Adam; Polyakov, Nikolay E; Kispert, Lowell D

2012-11-01

220

DPPH radical scavenging activity of a mixture of fatty acids and peptide-containing compounds in a protein hydrolysate of Jatropha curcas seed cake.  

Science.gov (United States)

Jatropha curcas, a tropical plant, has great potential commercial relevance as its seeds have high oil content. The seeds can be processed into high-quality biofuel producing seed cake as a byproduct. The seed cake, however, has not gotten much attention toward its potential usefulness. This work was aimed to determine the antioxidant activity of different fractions of a protein hydrolysate from J. curcas seed cake and to elucidate the molecular structures of the antioxidants. Seed cake was first processed into crude protein isolate and the protein was hydrolyzed by Neutrase. The hydrolysate obtained from 1 h of Neutrase hydrolysis showed the strongest antioxidant activity against DPPH radical (2,2-diphenyl-1-picrylhydrazyl). After a purification series of protein hydrolysate by liquid chromatography, chemicals acting as DPPH radical inhibitors were found to be a mixture of fatty acids, fatty acid derivatives, and a small amount of peptides characterized by mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy. PMID:24191657

Phengnuam, Thanyarat; Goroncy, Alexander K; Rutherfurd, Shane M; Moughan, Paul J; Suntornsuk, Worapot

2013-12-01

 
 
 
 
221

Synthesis and antiviral activities of the major metabolites of the HIV protease inhibitor ABT-378 (Lopinavir).  

Science.gov (United States)

The HIV protease inhibitor ABT-378 (Lopinavir) is metabolized rapidly and extensively by CYP-3A4 catalyzed oxidation. Three of the major metabolites identified were synthesized and their antiviral (HIV) activities determined. PMID:11378352

Sham, H L; Betebenner, D A; Herrin, T; Kumar, G; Saldivar, A; Vasavanonda, S; Molla, A; Kempf, D J; Plattner, J J; Norbeck, D W

2001-06-01

222

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

223

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

224

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

Directory of Open Access Journals (Sweden)

Full Text Available Nitrous acid (HONO mixing ratios for the Houston metropolitan area were simulated with the Community Multiscale Air Quality (CMAQ Model for an episode during the Texas Air Quality Study (TexAQS II in August/September 2006 and compared to in-situ MC/IC (mist-chamber/ion chromatograph and long path DOAS (Differential Optical Absorption Spectroscopy measurements at three different 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

225

Caenorhabditis elegans bicarbonate transporter ABTS-1 is involved in arsenite toxicity and cholinergic signaling.  

Science.gov (United States)

Arsenic poisoning affects millions of people worldwide. Although there is accumulating evidence to suggest that the nervous system is a target of arsenic, relatively little information is known regarding its effects on the nervous system. The effects of arsenite on the nervous system in Caenorhabditis elegans were investigated in the present study. We found that abts-1, which encodes a Na(+)-dependent Cl(-)/HCO(3)(-) transporter, is required to protect C. elegans from arsenite toxicity. The abts-1::GFP transgene is primarily expressed in neurons and the hypodermis, but stronger expression was also observed in the pharynx and body wall muscle cells after exposure to arsenite. The steady-state level of ABTS-1 mRNA increased in response to arsenite exposure. We showed that worms lacking abts-1 are hypersensitive to the paralytic effects of the cholinesterase inhibitor, aldicarb, and the nicotinic acetylcholine receptor agonist, levamisole. We also showed that arsenite enhanced sensitivity to aldicarb and levamisole in abts-1 mutant worms. Our results indicate neuronal effects of arsenite and the ABTS-1 bicarbonate transporter. PMID:20423156

Liao, Vivian Hsiu-Chuan; Liu, Jui-Tung; Li, Wen-Hsuan; Yu, Chan-Wei; Hsieh, Yi-Chen

2010-05-17

226

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

227

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

228

Antioxidant properties of a human neuropeptide and its protective effect on free radical-induced DNA damage.  

Science.gov (United States)

Human catestatin CgA352-372 (SL21) is an endogenous neuropeptide with multiple biological functions. The present study aimed to evaluate the antioxidant, antibacterial, cytotoxic, and DNA damage protective effects of SL21 neuropeptide. SL21 neuropeptide generated from the C-terminus of chromogranin A (CgA) was synthesized by solid-phase method. Synthetic peptide was subjected to various in vitro antioxidant assays including the scavenging of 1,1-diphenyl-2-pycryl-hydrazyl (DPPH), 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(·+) ), and hydroxyl free radicals, metal ion chelation, inhibition of lipid peroxidation, and reducing power. Moreover, protective effect of SL21 on H2 O2 -induced DNA damage was analyzed using pTZ57/RT plasmid. Methylthiazoltetrazolium assay was also performed to study the cytotoxic effect of SL21 neuropeptide on human peripheral blood mononuclear cells. Furthermore, antibacterial and hemolysis assays were conducted. The results demonstrated high activities of SL21 in scavenging free radicals (DPPH, ABTS(·+) , and hydroxyl), chelating of Cu(2+) /Fe(2+) metal ions, reducing power, and inhibition of lipid peroxidation in a concentration-dependent manner. SL21 neuropeptide revealed a protective effect on DNA damage caused by hydroxyl radicals. Interestingly, the peptide exhibited no significant cytotoxicity towards peripheral blood mononuclear cells. Furthermore, SL21 peptide displayed antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa without any hemolytic activity on human red blood cells. Conclusively, the present study established SL21 (catestatin) as a novel antioxidative peptide that could further be investigated for its potential use as a pharmaceutical agent. PMID:24723458

Mohseni, Simin; Emtenani, Shirin; Emtenani, Shamsi; Asoodeh, Ahmad

2014-06-01

229

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

Science.gov (United States)

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

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

2014-11-01

230

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.

231

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 present study was to determine the in vitro antioxidant activity of aqueous extracts from leaves of Bauhinia forficata Link (Fabaceae - Caesalpinioideae and Cissus sicyoides L. (Vitaceae (two medicinal plants used popularly in the control of diabetes mellitus, using several different assay systems, namely, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS decolorization, superoxide 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

2008-01-01

232

Characterization of structure-antioxidant activity relationship of peptides in free radical systems using QSAR models: key sequence positions and their amino acid properties.  

Science.gov (United States)

Antioxidative peptides have attracted increasing attention from researchers because of their antioxidant properties as natural materials in functional food and for applications in medicine. However, the relationship between structure and activity (SAR) remains unclear, especially in antioxidative peptides in free radical systems. Antioxidative peptides with different lengths were obtained from the literature, measured using different methods, and were organized into three databases, namely, Trolox-equivalent antioxidant capacity (TEAC), oxygen radical absorption capacity (ORAC), and superoxide radical (SOR). After the peptides were processed using the two-terminal position numbering method, quantitative SAR modeling was performed on antioxidative peptides in the three databases. The vectors of hydrophobic, steric, and electronic properties (VHSE) and the divided physicochemical property scores descriptors (DPPS) were selected from 17 physicochemical descriptors to express electronic, hydrophobic, and steric properties (or hydrogen bonding) of the three (or four) external amino acids in the N-terminal and C-terminal positions. Models were estimated using partial least squares regression and validated through full cross-validation and external validation (R(2)>0.7, Q(2)>0.5 for TEAC; R(2)>0.9, Q(2)>0.5 for ORAC and SOR). The results found a relationship between the physicochemical properties of the C-terminal and N-terminal regions and antioxidant potency. The properties of amino acids at C-terminal regions were more important than those at the N-terminal regions for predicting antioxidant activity. The properties of amino acids at C(2)>C(1) for TEAC, C(3)>C(4)>C(1) for ORAC, and C(4)>C(1)>N(1) for SOR were highly correlated with antioxidant activity. Although electronic property most significantly contributed to antioxidant activity in the three free radical systems, it had complex effects at each position. Bulky hydrophobic amino acids at the C-terminal were related to the antioxidant activity of peptides in the three free radical systems. For peptides in the TEAC database, the relationship between the N-terminal segment (N(2), N(3)) and the activity increased when longer peptides were included, which reflects the likely influence of stericity. This study contributes to the ongoing research on antioxidants in food and its application in medicine. PMID:23127747

Li, Yao-Wang; Li, Bo

2013-02-01

233

The PARP inhibitor ABT-888 synergizes irinotecan treatment of colon cancer cell lines.  

Science.gov (United States)

Poly [ADP-ribose] polymerase-1 (PARP-1) localizes rapidly to sites of DNA damage and has been associated with various repair mechanisms including base excision repair (BER) and homologous recombination/non-homologous end joining (HRR/NHEJ). PARP-1 acts by adding poly-ADP ribose side chains to target proteins (PARylation) altering molecular interactions and functions. Recently small molecule inhibitors of PARP-1 have been shown to have significant clinical potential and third generation PARP inhibitors are currently being investigated in clinical trials. These drugs alone or in combination with radio/chemotherapy have resulted in meaningful patient responses and an increase in survival in metastatic breast cancer cases bearing BRCA-deficient or triple negative tumors and BRCA-deficient ovarian cancer patients. ABT-888, a potent PARP-1 inhibitor, sensitizes many cancer cells in-vitro and in-vivo to temozolomide. As such, we hypothesized that colon cancers would be sensitized to the DNA damaging chemotherapeutic agents, oxaliplatin and irinotecan, by ABT-888. Using colon cancer cell lines significant synergy was observed between ABT-888 and irinotecan at concentrations of ABT-888 as low as 0.125 ?M. The level of synergy observed correlated with the degree of PARP1 inhibition as measured biochemically in cell lysates. ABT-888 at concentrations of 0.5-4 ?M resulted in synergy with oxaliplatin. Furthermore, 24 h post treatment combinations of ABT-888/irinotecan generally resulted in increased G2/M cell cycle arrest and increased levels of DNA damage, followed by increased levels of apoptosis 48 h post treatment. In conclusion this study suggests that ABT-888 may be a clinically effective adjuvant to current colon cancer therapies that include the use of irinotecan and/or oxaliplatin. PMID:23054213

Davidson, David; Wang, Yunzhe; Aloyz, Raquel; Panasci, Lawrence

2013-04-01

234

Physiology of free radicals  

Directory of Open Access Journals (Sweden)

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

235

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

236

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

Science.gov (United States)

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

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

1997-04-01

237

Oil, protein, antioxidants and free radical scavenging activity of stone from wild olive trees (Olea europaea L.).  

Science.gov (United States)

The wild olive trees or oleaster (var. sylvestris) and the cultivated olive trees (var. europaea) constitute the two botanical varieties of Olea europaea L. from Mediterranean. In this study, a partial chemical profile was conducted including the total lipids, the fatty acid profiles, soluble proteins, polyphenols, flavanoids contents and antioxidants activities of stone from six oleaster trees. The comparison was made by two olive cultivars cultivated in the same region. The oleaster and cultivar stones were richer in oil content having an average of 8.99 and 7.38 % dry weight basis (DW), respectively. Qualitatively, all studied oils have the same fatty acids profile with the oleic acid C18:1n-9 as the major fatty acid. The oleaster stone oils were richer in monounsaturated fatty acids having an average of 64.87%. They, also, richer in protein content with an average of 198.86 mg/g DW.The globulin is the major fraction, followed by the albumin, the prolamin and the glutemin fractions. The oleaster stone extracts contain polyphenols, flavonoids with an average of 151.14 and 11.91 mg gallic acid equivalent/100g of DW, respectively. The studied extracts showed antioxidant activity using the free radical scavenging activity determined by DPPH and ABTS. The unexploited oleaster stone seems to be a source of oil with good fatty acids balance, in protein and antioxidants metabolites and would be useful for the formulation of supplements and/or pharmaceutical ingredients. PMID:23625423

Hannachi, Hédia; Elfalleh, Walid; Marzouk, Sizaiem

2013-05-01

238

Scavenging capacity of medicinal plants against free radical-induced cellular damage by radiation and photoactivation  

International Nuclear Information System (INIS)

The scavenging capacity of medicinal plants. Andrographis paniculata (Ap) and Swertia chirata (Sc) was examined against cellular damage, induced by radiation and photo-activation in sub-cellular membranes. The results demonstrated significant radical scavenging capacity of the extracts. The rate constants as evaluated by deoxyribose degradation studies and the pulse radiolysis studies carried in presence of ABTS radical well supported the antioxidant properties of the extracts. (author)

239

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

International Nuclear Information System (INIS)

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

240

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

 
 
 
 
241

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

242

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

Science.gov (United States)

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

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

2013-11-01

243

Dihydroasparagusic acid: antioxidant and tyrosinase inhibitory activities and improved synthesis.  

Science.gov (United States)

Dihydroasparagusic acid (DHAA) is the reduced form of asparagusic acid, a sulfur-containing flavor component produced by Asparagus plants. In this work, DHAA was synthetically produced by modifying some published protocols, and the synthesized molecule was tested in several in vitro assays (DPPH, ABTS, FRAP-ferrozine, BCB, deoxyribose assays) to evaluate its radical scavenging activity. Results show that DHAA is endowed with a significant in vitro antioxidant activity, comparable to that of Trolox. DHAA was also evaluated for its inhibitory activity toward tyrosinase, an enzyme involved, among others, in melanogenesis and in browning processes of plant-derived foods. DHAA was shown to exert an inhibitory effect on tyrosinase activity, and the inhibitor kinetics, analyzed by a Lineweaver-Burk plot, exhibited a competitive mechanism. Taken together, these results suggest that DHAA may be considered as a potentially active molecule for use in various fields of application, such as pharmaceutical, cosmetics, agronomic and food. PMID:23790134

Venditti, Alessandro; Mandrone, Manuela; Serrilli, Anna Maria; Bianco, Armandodoriano; Iannello, Carmelina; Poli, Ferruccio; Antognoni, Fabiana

2013-07-17

244

Effect of free radical spin trap N-tert-butyl-alpha-phenylnitrone (PBN) on seizures induced in immature rats by homocysteic acid.  

Science.gov (United States)

The present study has examined the effect of free radical spin trap N-tert-butyl-alpha-phenylnitrone (PBN) in the model of seizures induced in immature 12-day-old rats by bilateral intracerebroventricular infusion of dl-homocysteic acid (dl-HCA, 600 nmol/side). PBN was given i.p. in two doses (100 mg/kg each), 30 min prior and 30 min after dl-HCA infusion. PBN did not significantly influence the severity of seizures, evident both from the behavioral symptoms and EEG recordings. PBN normalized decreased ATP levels in the hippocampus, occurring during the acute phase of seizures ( approximately 45-50 min after infusion) and persisting until the end of the 24-h recovery period. PBN also led to normalization of decreased glucose levels and to a significant reduction of lactate accumulation in the cerebral cortex and hippocampus. The neuroprotective effect of PBN was evaluated after 24 h and 6 days of survival following dl-HCA-induced seizures (Nissl and Fluoro-Jade B staining). The administration of PBN resulted in a partial amelioration of severe damage observed in many brain regions following infusion of dl-HCA alone. The data suggest that increased free radical production is apparently occurring during seizures induced in immature rats by homocysteic acid. Free radical scavenger PBN had a clear-cut protective effect, evident as the improved recovery of brain energy status and as a partial, but significant, attenuation of neuronal degeneration associated with this model of seizures. PMID:16756975

Folbergrová, Jaroslava; Druga, Rastislav; Otáhal, Jakub; Haugvicová, Renata; Mares, Pavel; Kubová, Hana

2006-09-01

245

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

Science.gov (United States)

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

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

2013-10-01

246

The BCL2 inhibitor ABT-199 significantly enhances imatinib-induced cell death in chronic myeloid leukemia progenitors.  

Science.gov (United States)

BCR-ABL1-specific tyrosine kinase inhibitors prolong the life of patients with chronic myeloid leukemia (CML) but cannot completely eradicate CML progenitors. The BH3 mimetic, ABT-263, targets prosurvival BCL2 family members, and has activity against CML progenitors. However, the inhibitory effect of ABT-263 on BCL-XL, which mediates platelet survival, produces dose-limiting thrombocytopenia. A second-generation BH3 mimetic, ABT-199, has been developed to specifically bind BCL2 but not BCL-XL. We determined the activity of ABT-199 against CML cell lines, as well as primary CML and normal cord blood (NCB) progenitors. We find that BCL2 expression levels predict sensitivity to ABT-199 in CML and NCB progenitors, and that high NCB BCL2 levels may explain the reported hematologic toxicities in ABT-199-treated patients. Also, while single agent ABT-199 has modest activity against CML progenitors, when combined with imatinib, ABT-199 significantly enhances imatinib activity against CML progenitors at concentrations predicted to avoid hematologic toxicities. PMID:25333252

Ko, Tun Kiat; Chuah, Charles T H; Huang, John W J; Ng, King-Pan; Ong, S Tiong

2014-10-15

247

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

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

Amner Mu\\u00F1oz

2007-01-01

248

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2006-01-01

249

Population analyses of efficacy and safety of ABT-594 in subjects with diabetic peripheral neuropathic pain.  

Science.gov (United States)

ABT-594, a neuronal nicotinic acetylcholine receptor ligand, is 30- to 100-fold more potent than morphine in animal models of nociceptive and neuropathic pain. Efficacy and safety of ABT-594 in subjects with painful diabetic polyneuropathy was evaluated in a phase 2 study. The objective of this work was to use a nonlinear mixed effects model-based approach for characterizing the relationship between dose and response (efficacy and safety) of ABT-594. Subjects (N?=?266) were randomized into four groups in a double-blind, placebo-controlled, 7-week study to receive twice daily regimens of placebo or 150, 225, and 300 ?g of ABT-594. The primary efficacy variable, pain score (11-point Likert scale), was assessed on five occasions. The probability of change from baseline pain score of ?1, ?2, and ?3 was modeled using cumulative logistic regression with dose and days of treatment as explanatory variables. The incidence of five most frequently occurring adverse events (AEs) was modeled using linear logistic regression. ABT-594 ED(50) values (improvement in 50% of subjects) for improvement in pain scores of ?1, ?2, and ?3 were 50, 215, and 340 ?g, respectively, for the average number of days (33) on treatment. The rank order of ED(50) values for AEs was nausea, vomiting, dizziness, headache, and abnormal dreams; nicotine users were less sensitive to AEs. Population pharmacodynamic models developed to characterize the improvement in pain score and incidence of adverse events indicate an approximately twofold separation between the ED(50) values for efficacy and AEs. PMID:22328206

Dutta, Sandeep; Hosmane, Balakrishna S; Awni, Walid M

2012-06-01

250

ABT-263 and rapamycin act cooperatively to kill lymphoma cells in vitro and in vivo.  

Science.gov (United States)

ABT-263 is a potent, orally bioavailable inhibitor of the antiapoptotic Bcl-2 family members Bcl-2, Bcl-x(L), and Bcl-w, which is currently in phase I clinical trials. Previous work has shown that this compound has low nanomolar cell-killing activity in a variety of lymphoma and leukemia cell lines, many of which overexpress Bcl-2 through a variety of mechanisms. Rapamycin is a macrolide antibiotic that inhibits the mammalian target of rapamycin complex, leading to cell cycle arrest and inhibition of protein translation. Rapamycin (and its analogues) has shown activity in a variety of tumor cell lines primarily through induction of cell cycle arrest. Activity has also been shown clinically in mantle cell lymphoma and advanced renal cell carcinoma. Here, we show that treatment of the follicular lymphoma lines DoHH-2 and SuDHL-4 with 100 nmol/L rapamycin induces substantial G(0)-G(1) arrest. Addition of as little as 39 nmol/L ABT-263 to the rapamycin regimen induced a 3-fold increase in sub-G(0) cells. Combination of these agents also led to a significant increase in Annexin V staining over ABT-263 alone. In xenograft models of these tumors, rapamycin induced a largely cytostatic response in the DoHH-2 and SuDHL-4 models. Coadministration with ABT-263 induced significant tumor regression, with DoHH-2 and SuDHL-4 tumors showing 100% overall response rates. Apoptosis in these tumors was significantly enhanced by combination therapy as measured by staining with an antibody specific for cleaved caspase-3. These data suggest that combination of ABT-263 and rapamycin or its analogues represents a promising therapeutic strategy for the treatment of lymphoma. PMID:18852130

Ackler, Scott; Xiao, Yu; Mitten, Michael J; Foster, Kelly; Oleksijew, Anatol; Refici, Marion; Schlessinger, Sally; Wang, Baole; Chemburkar, Sanjay R; Bauch, Joy; Tse, Christin; Frost, David J; Fesik, Stephen W; Rosenberg, Saul H; Elmore, Steven W; Shoemaker, Alex R

2008-10-01

251

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

Science.gov (United States)

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

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

2012-12-19

252

Kinetics and mechanism for the oxidation of ascorbic acid/ascorbate by HO2/O2- radicals. A pulse radiolysis and stopped-flow photolysis study  

International Nuclear Information System (INIS)

The reaction between ascorbic acid/ascorbate and molecular oxygen and its derivatives (HO2/O2-) (AH2/AH-) was followed from pH 0.3 to 11, leading to the following rate constants: kappa8 = 1.6 x 104 M-1 s-1 for the reaction between AH2 and HO2, kappa17 + 0.365 kappa18 = 1.22 x 107 M-1 s-1 for the reactions between AH- and HO2 and AH2 and O2-, respectively, and kappa19 = 5 x 104 M-1 s-1 for the reaction between AH- and O2-. The radical-radical reactions of A- with HO2 and O2- were measured and found to proceed at rates of kappa9 = 5 x 109 s-1 and kappa11 = 2.6 x 108 M-1 s-1, respectively. An overall mechanism for the oxidation of AH2/AH- by HO2/O2- consistent with the experimental results is also proposed. 1 figure, 1 table

253

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

254

Effects of Extraction and Processing Methods on Antioxidant Compound Contents and Radical Scavenging Activities of Laver (Porphyra tenera)  

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Laver is one of the most consumed edible red algae seaweeds in the genus Porphyra. Laver is primarily prepared in the form of dried, roasted, and seasoned products. We investigated the total polyphenol and flavonoid contents of laver products, and evaluated the in vitro antioxidant properties of solvent extracts from commercially processed laver products. Significant differences in the concentration of phenolic compounds were found among differently processed laver. The total phenolic content for laver extracts ranged from 10.81 mg gallic acid equivalent (GAE)/g extract to 32.14 mg GAE/g extract, depending on extraction solvent and temperature. Laver extracts contained very few flavonoids (0.55 mg catechin equivalent/g extracts to 1.75 mg catechin equivalent/g extracts). 2,2-Diphenyl-1-picrylhydrazyl (DPPH), 2,2?-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS), hydroxyl radical, and superoxide anion scavenging assays were used to determine the radical scavenging capacities of laver extracts. These assays revealed that the processing method and extraction condition affected the antioxidant potentials of laver. Antioxidant activity of dried laver, roasted laver, and seasoned laver increased in a concentration-dependent manner (100~1,000 ?g/mL). The radical scavenging activities of 37°C and 100°C water extracts were lower than that of a 37°C 70% ethanol extract. The highest radical scavenging capacity was observed in the 37°C 70% ethanol extracts of dried laver, roasted laver, and seasoned laver. Overall, these results support that notion that laver contains bioactive compounds, such as polyphenols and flavonoids, which may have a positive effect on health. PMID:24772408

Hwang, Eun-Sun; Thi, Nhuan Do

2014-01-01

255

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)

256

A novel Bcl-2/Bcl-X(L)/Bcl-w inhibitor ABT-737 as therapy in multiple myeloma.  

Science.gov (United States)

Bcl-2 or Bcl-X(L) confers resistance to chemotherapy in multiple myeloma (MM). Here we characterized the effects of ABT-737, a potent small-molecule inhibitor of antiapoptotic proteins Bcl-2, Bcl-X(L) and Bcl-w with markedly higher affinity than previously reported compounds, on human MM cells. ABT-737 induces apoptosis in MM cells, including those resistant to conventional therapy. Examination of purified patient MM cells demonstrated similar results, without significant toxicity against normal peripheral blood mononuclear cells and MM bone marrow stromal cells. Importantly, ABT-737 decreases the viability of bortezomib-, dexamethasone-(Dex) and thalidomide-refractory patient MM cells. Additionally, ABT-737 abrogates MM cell growth triggered by interleukin-6 or insulin-like growth factor-1. Mechanistic studies show that ABT-737-induced apoptosis is associated with activation of caspase-8, caspase-9 and caspase-3, followed by poly(ADP-ribose) polymerase cleavage. Combining ABT-737 with proteasome inhibitor bortezomib, melphalan or dexamethasone induces additive anti-MM activity. Taken together, our study provides the rationale for clinical protocols evaluating ABT-737, alone and together with botezomib, mephalan or dexamethasone, to enhance MM cell killing, overcome drug resistance conferred by Bcl-2 and improve patient outcome in MM. PMID:17016430

Chauhan, D; Velankar, M; Brahmandam, M; Hideshima, T; Podar, K; Richardson, P; Schlossman, R; Ghobrial, I; Raje, N; Munshi, N; Anderson, K C

2007-04-01

257

THERMOCHEMISTRY OF HYDROCARBON RADICALS  

Energy Technology Data Exchange (ETDEWEB)

Gas phase negative ion chemistry methods are employed to determine enthalpies of formation of hydrocarbon radicals that are important in combustion processes and to investigate the dynamics of ion-molecule reactions. Using guided ion beam tandem mass spectrometry, we measure collisional threshold energies of endoergic proton transfer and hydrogen atom transfer reactions of hydrocarbon molecules with negative reagent ions. The measured reaction threshold energies for proton transfer yield the relative gas phase acidities. In an alternative methodology, competitive collision-induced dissociation of proton-bound ion-molecule complexes provides accurate gas phase acidities relative to a reference acid. Combined with the electron affinity of the R {center_dot} radical, the gas phase acidity yields the RH bond dissociation energy of the corresponding neutral molecule, or equivalently the enthalpy of formation of the R{center_dot} organic radical, using equation: D(R-H) = {Delta}{sub acid}H(RH) + EA(R) - IE(H). The threshold energy for hydrogen abstraction from a hydrocarbon molecule yields its hydrogen atom affinity relative to the reagent anion, providing the RH bond dissociation energy directly. Electronic structure calculations are used to evaluate the possibility of potential energy barriers or dynamical constrictions along the reaction path, and as input for RRKM and phase space theory calculations. In newer experiments, we have measured the product velocity distributions to obtain additional information on the energetics and dynamics of the reactions.

Kent M. Ervin, Principal Investigator

2004-08-17

258

Comparative evaluation of free radical scavenging activity of Boerhaavia diffusa root extracts (BDRE and determination of dose effectivity against radiation induced damages in Swiss albino mice  

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Full Text Available Summary: Purpose of the study was to evaluate free radical scavenging activity (FRSA of root extracts of Boerhaavia diffusa in different solvents and to examine its dose effectivity against radiation induced damages in Swiss albino mice. Scavenging activities of aqueous, ethanolic and hydroethanolic extracts of B. diffusa roots were evaluated by DPPH (2, 2-diphenyl-1 picryl hydrazyl, ABTS (2,2’-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid and NO (nitric oxide assay to find the most effective extract and results were expressed as IC50. To find the most effective dose, hydroethanolic root extract (50:50 of B. diffusa was orally administered to Swiss albino mice at the dose of 250, 500 and 1000 mg/Kg.body.weight for 15 consecutive days prior to irradiation with 8 Gy gamma radiation. Results indicates that hydroethanolic extract exhibited the highest free radical scavenging activity in DPPH., ABTS.+ and NO. assays showing IC50 as 293.77, 43.62 and 32.58 µg/ml, respectively. Reduced symptoms of radiation sickness, decline in body weight and mortality were minimum when mice were pre-treated with hydroethanolic extract at the dose of 1000 mg/Kg.body.weight prior to irradiation with 8 Gy gamma radiation as compared to mice pre-treated with extract at  the dose of 250 and 500 mg/Kg.body.weight prior to irradiation with same dose of radiation. Thus, it was Concluded that certain phenolic constituents of B. diffusa roots like quercitin, caeffic acid, kempferol etc. and their derivatives act as antioxidant compounds confirming B. diffusa roots a potential source of antioxidant agent. Industrial Relevance: Having noticed with the importance of phytochemicals including flavonoids and phenolic acids as contributing factors to the antioxidant activity and common use of roots of Boerhaavia diffusa in majority of medicinal aspects can be responsible in curing oxidative stress related diseases in human beings. This study perhaps will be helpful in development of the effective drug for providing protection to biological systems against free radical induced damage. Keywords: Radioprotection, Boerrhavia diffusa, Free Radical Scavenging Activity, Dose Reduction Factor, Antioxidants.

J Sharma

2012-12-01

259

Kinetics of self-decomposition and hydrogen atom transfer reactions of substituted phthalimide N-oxyl radicals in acetic acid.  

Science.gov (United States)

Kinetic data have been obtained for three distinct types of reactions of phthalimide N-oxyl radicals (PINO(.)) and N-hydroxyphthalimide (NHPI) derivatives. The first is the self-decomposition of PINO(.) which was found to follow second-order kinetics. In the self-decomposition of 4-methyl-N-hydroxyphthalimide (4-Me-NHPI), H-atom abstraction competes with self-decomposition in the presence of excess 4-Me-NHPI. The second set of reactions studied is hydrogen atom transfer from NHPI to PINO(.), e.g., PINO(.) + 4-Me-NHPI NHPI + 4-Me-PINO(.). The substantial KIE, k(H)/k(D) = 11 for both forward and reverse reactions, supports the assignment of H-atom transfer rather than stepwise electron-proton transfer. These data were correlated with the Marcus cross relation for hydrogen-atom transfer, and good agreement between the experimental and the calculated rate constants was obtained. The third reaction studied is hydrogen abstraction by PINO(.) from p-xylene and toluene. The reaction becomes regularly slower as the ring substituent on PINO(.) is more electron donating. Analysis by the Hammett equation gave rho = 1.1 and 1.8 for the reactions of PINO(.) with p-xylene and toluene, respectively. PMID:15624928

Cai, Yang; Koshino, Nobuyoshi; Saha, Basudeb; Espenson, James H

2005-01-01

260

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

Science.gov (United States)

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

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

2013-12-01

 
 
 
 
261

Free radical scavenging activity of 4-(3,4-dihydroxybenzoyloxymethyl)phenyl-O-?-D-glucopyranoside from Origanum vulgare and its protection against oxidative damage.  

Science.gov (United States)

4-(3,4-Dihydroxybenzoyloxymethyl)phenyl-O-?-d-glucopyranoside (DBPG), a polyphenolic glycoside, isolated from Origanum vulgare has shown 1,1-diphenyl-2-picrylhydrazyl (DPPH(•))-scavenging capacity in previous work. This study demonstrated that DBPG exhibits antioxidant activity by a series of DPPH(•), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS(•+)), and superoxide anion radical (O(2)(•-)) radical-scavenging assays. The inhibition of lipid peroxidation (LP) by DBPG exceeded that by l-ascorbic acid (AA) in a liposome model system. Adding DBPG to mouse liver and brain tissue inhibited the formation of thiobarbituric acid reactive substances (TBARS) to a greater extent than did trolox. In the oxygen stress test, BNLCL2 and HaCaT cells pretreated with DBPG showed increased activities of glutathione peroxidase (GPx), perhaps as a result of reduction of the production of reactive oxygen species (ROS). These findings proved that DBPG had antioxidant activities and a cytoprotective effect in hepatocytes and keratinocytes, suggesting that DBPG may be a useful food and cosmetic additive. PMID:22800339

Liang, Chia-Hua; Chan, Leong-Perng; Ding, Hsiou-Yu; So, Edmund Cheung; Lin, Rong-Jyh; Wang, Hui-Min; Chen, Ying-Ging; Chou, Tzung-Han

2012-08-01

262

Comparative in vitro activities of ABT-773 against 362 clinical isolates of anaerobic bacteria.  

Science.gov (United States)

The activity of ABT-773, a novel ketolide antibiotic, against clinical isolates of anaerobic bacteria was determined and compared to the activities of other antimicrobial agents. MICs at which 90% of isolates were inhibited (MIC(90)s) were 32 microg/ml, respectively, for Eubacterium spp., Lactobacillus spp., Clostridium difficile, and Clostridium ramosum. The MIC(90) for Bilophila wadsworthia, Bacteroides ureolyticus, and Campylobacter gracilis was 1 microg/ml, and that for Prevotella bivia and other Prevotella spp. was 0.5 microg/ml. The MIC(90) for Fusobacterium nucleatum was 8 microg/ml, and that for Fusobacterium mortiferum and Fusobacterium varium was >32 microg/ml. The MIC(90)s for the Bacteroides fragilis group were as follows: for B. fragilis, 8 microg/ml; for Bacteroides thetaiotaomicron, Bacteroides ovatus, Bacteroides distasonis, and Bacteroides uniformis, >32 microg/ml; and for Bacteroides vulgatus, 4 microg/ml. Telithromycin MICs for the B. fragilis group were usually 1 to 2 dilutions higher than ABT-773 MICs. For all strains, ABT-773 was more active than erythromycin by 4 or more dilutions, and for some strains this drug was more active than clindamycin. PMID:11120995

Citron, D M; Appleman, M D

2001-01-01

263

Selective BCL-2 Inhibition by ABT-199 Causes On Target Cell Death in Acute Myeloid Leukemia  

Science.gov (United States)

B-cell leukemia/lymphoma 2 (BCL-2) prevents commitment to programmed cell death at the mitochondrion. It remains a challenge to identify those tumors that are best treated by inhibition of BCL-2. Here we demonstrate that acute myeloid leukemia (AML) cell lines, primary patient samples, and murine primary xenografts are very sensitive to treatment with the selective BCL-2 antagonist ABT-199. In primary patient cells, the median IC50 was approximately 10 nM, and cell death occurred within 2 h. Our ex vivo sensitivity results compare favorably with those observed for chronic lymphocytic leukemia (CLL), a disease for which ABT-199 has demonstrated consistent activity in clinical trials. Moreover, mitochondrial studies using BH3 profiling demonstrate activity at the mitochondrion that correlates well with cytotoxicity, supporting an on target mitochondrial mechanism of action. Our protein and BH3 profiling studies provide promising tools that can be tested as predictive biomarkers in any clinical trial of ABT-199 in AML. PMID:24346116

Pan, Rongqing; Hogdal, Leah J.; Benito, Juliana M; Bucci, Donna; Han, Lina; Borthakur, Gautam; Cortes, Jorge; DeAngelo, Daniel J.; Debose, LaKeisha; Mu, Hong; Dohner, Hartmut; Gaidzik, Verena I.; Galinsky, Ilene; Golfman, Leonard S.; Haferlach, Torsten; Harutyunyan, Karine G.; Hu, Jianhua; Leverson, Joel D; Marcucci, Guido; Muschen, Markus; Newman, Rachel; Park, Eugene; Ruvolo, Peter P.; Ruvolo, Vivian; Ryan, Jeremy; Schindela, Sonja; Zweidler-McKay, Patrick; Stone, Richard M.; Kantarjian, Hagop; Andreeff, Michael; Konopleva, Marina; Letai, Anthony G.

2014-01-01

264

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

265

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

266

Stability studies of ascorbic acid 2-glucoside in cosmetic lotion using surface response methodology.  

Science.gov (United States)

Ascorbic acid 2-glucoside (AA-2G) has been widely used in cream and lotion types of cosmetic products. Thus, the degradation of AA-2G caused by the temperature change and pH variation was very critical for determining the bio-functionality of cosmetics. Response surface methodology (RSM) was introduced to study the influence of temperature and pH on the stability of AA-2G. The optimal condition of retaining AA-2G with the highest stability was determined to be 55.3°C and pH 6.4. The antioxidative activities of AA-2G including DPPH and ABTS free radical scavenging activities, metal chelating activity, and reducing ability were also determined. AA-2G was a good ascorbic acid derivative which could be used in cosmetic products as an active ingredient. PMID:23416010

Huang, Wen-Ying; Lee, Pei-Chi; Huang, Ling-Kuei; Lu, Li-Ping; Liao, Wayne C

2013-03-15

267

Potential cytoprotection: antioxidant defence by caffeic acid phenethyl ester against free radical-induced damage of lipids, DNA, and proteins.  

Science.gov (United States)

Oxidative stress is considered to be a major cause of cellular injuries in a variety of chronic health problems, such as carcinogenesis and neurodegenerative disorders. Caffeic acid phenethyl ester (CAPE), derived from the propolis of honeybee hives, possesses a variety of biological and pharmacological properties including antioxidant and anticancer activity. In the present study, we focused on the diverse antioxidative functionalities of CAPE and its related polyphenolic acid esters on cellular macromolecules in vitro. The effects on human erythrocyte membrane ghost lipid peroxidation, plasmid pBR322 DNA, and protein damage initiated by the water-soluble initiator 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH) and hydrogen peroxide (H(2)O(2)) were monitored by formation of hydroperoxides and by DNA nicking assay, single-cell alkaline electrophoresis, and SDS-polyacrylamide gel electrophoresis. Our results showed that CAPE and its related polyphenolic acid esters elicited remarkable inhibitory effects on erythrocyte membrane lipid peroxidation, cellular DNA strand breakage, and protein fragmentation. The results suggest that CAPE is a potent exogenous cytoprotective and antigenotoxic agent against cell oxidative damage that could be used as a template for designing novel drugs to combat diseases induced by oxidative stress components, such as various types of cancer. PMID:18432289

Wang, Ting; Chen, Lixiang; Wu, Weimin; Long, Yuan; Wang, Rui

2008-05-01

268

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

Directory of Open Access Journals (Sweden)

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

Ang Zhang

2011-12-01

269

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

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

Yu-Ra Son

2014-07-01

270

Degradation of hyaluronic acid by photosensitized riboflavin in vitro. Modulation of the effect by transition metals, radical quenchers, and metal chelators.  

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The effect of photoexcited riboflavin (RF) on the viscosity of hyaluronic acid (HA) solutions has been investigated. UV irradiation of RF causes under aerobic conditions fragmentation of HA and a decrease in the viscosity of its solutions. A decrease of HA viscosity occurs in PO(4)-buffered solutions and is accelerated by high pH, Fe2+ (but much less so by Fe3+), certain metal chelators, and horseradish peroxidase (HRP); it is partially inhibited by catalase and less so by superoxide dismutase (SOD). The reactivity of the system was completely blocked by Tris, ethanol, aspirin, d-manitol, dimethylthiourea (DMTU), dimethylsulfoxide (DMSO), and sodium azide. These results indicate that the most likely chemical species involved in the reaction is the hydroxyl radical. Singlet oxygen ((1)O(2)) generation is suggested by the ability of NaN3 and DMSO to completely inhibit the reactivity of the system. These two agents, however, may also interact with OH. radical, as well and suppress the reactivity of the system. H(2)O(2) and O(2).- seem also to be produced in significant amounts, because catalase and SOD partially block the reactivity of the system. The effect of HRP may be due to hydrogen subtraction from HA and H(2)O(2) reduction to water. Photoexcitation of RF may potentially occur in vitro and in vivo in the organs and tissues that are permeable to light, such as the eye or skin, and damage HA and other cell-matrix components causing inflammation and accelerating aging. PMID:9098086

Frati, E; Khatib, A M; Front, P; Panasyuk, A; Aprile, F; Mitrovic, D R

1997-01-01

271

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

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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

272

The ratio of Mcl-1 and Noxa determines ABT737 resistance in squamous cell carcinoma of the skin.  

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Tumour progression and therapy resistance in squamous cell carcinoma of the skin (SCC) is strongly associated with resistance to intrinsic mitochondrial apoptosis. We thus investigated the role of various anti-apoptotic Bcl-2 proteins for apoptosis protection in SCC using the BH3 agonist ABT737 that can overcome multidomain Bcl-2 protein protection. Sensitive SCC cells underwent rapid loss of mitochondrial membrane potential (MMP), subsequent apoptosis concomitant with caspase-3 activation and an early release of mitochondria-derived cytochrome c and smac/DIABLO. In contrast, ABT737 resistance in subsets of SCC cells was not explained by XIAP, important for protection from DR-induced apoptosis in SCC. Of note, ABT737 did not prime SCC cells to DR-induced apoptosis. Interestingly, the ratio of Mcl-1 and Noxa determined sensitivity to ABT737: loss of Mcl-1 rendered resistant cells sensitive to ABT737, whereas loss of Noxa promoted resistance in sensitive cells. In line, suppression of Mcl-1 by the pan-Bcl-2 inhibitor Obatoclax or overexpression of Noxa rendered resistant SCC cells sensitive to BH3 mimetics. Our data indicate that targeting of the Mcl-1/Noxa axis is important to overcome resistance to mitochondrial apoptosis in SCC. Therefore, combination treatment of ABT737 or derivatives with Mcl-1 inhibitors, or inducers of Noxa, may represent a novel option of targeted therapy in metastatic SCC of the skin. PMID:25210795

Geserick, P; Wang, J; Feoktistova, M; Leverkus, M

2014-01-01

273

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

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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

274

[Effect of modifications of a series of amino acid radicals on the enzymatic activity of glucoamylase from Aspergillus awamori].  

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The effect of chemical modification of various amino acid residues on the enzymatic activity of glucoamylase from Asp. awamori was studied. Modification of the carboxyl groups by taurine in the presence of water-soluble carbodiimide results in complete inactivation of the enzyme. The inactivation process includes two steps, namely non-specific modification and modification of the active center carboxyls. The rate constants of inactivation at both steps were measured in the presence and absence of the substrate, i. e. maltose. It was shown that the enzyme is inactivated by N-bromosuccinimide. Based on the data on the protection of the enzyme active center by the substrates (maltooligosaccharides of various lengths), it was concluded that the essential tryptophane residue(s) is localized in the fourth subsite. Ethoxycarbonylation, nitration and acetylation of glucoamylase do not change the catalytic activity of the enzyme. The protein was shown to contain no SH-groups. PMID:6414534

Savel'ev, A N; Firsov, L M

1983-08-01

275

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

276

Redox properties of free radicals  

International Nuclear Information System (INIS)

Results of electron transfer reactions observed and monitored by pulse radiolysis are reported. This technique allows determination of the first one-electron reduction or oxidation of a compound rather than the overall two-electron transfer usually reported. Pulse radiolysis allows the determination of absolute rate constants for reactions of free radicals and helps elucidate the mechanisms involved. Studies using this technique to study radicals derived from quinones, nitro compounds, pyridines, phenols, and anilines are reported. Radicals of biochemical interest arising from riboflavin, ascorbic acid, vitamin K3, vitamin E, MAD+, porphyrins, etc. have also been studied

277

?-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 CH2-C(O)CH3 radicals are observed following the pulse radiolysis of CH3CH2SCH2C(O)CH3

278

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

279

Trivalent acid radical-centered YLi4(+) (Y = PO4, AsO4, VO4) cations: new polynuclear species designed to enrich the superalkali family.  

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A new series of polynuclear superalkali cations YLi4(+) (Y = PO4, AsO4, VO4) has been characterized using ab initio methods. The central Y(3-) (PO4(3-), AsO4(3-), VO4(3-)) acid radicals preserve their structural and electronic integrity in the first several lowest-lying isomers of YLi4(+). Meanwhile, the introduction of Li(+) cations can also dissociate an O(2-) ion from the Y(3-) groups. Besides, the AsO4(3-) group is discerned to be separated into AsO2(-) and O2(2-) fragments other than AsO3(-) and O(2-) units. This is why the AsO4Li4(+) cation has been found to possess more diverse structures. The vertical electron affinities (EAvert) of the YLi4(+) cations range from 2.44 to 4.67 eV, which are low enough to validate the superalkali or pseudoalkali identity of the title species. It is also noteworthy that the YLi4(+) conformer with Td symmetry allows a more even distribution of the excess positive charge, and consequently exhibits the lowest EAvert value of ca. 2.45 eV. PMID:25353318

Liu, Jia-Yuan; Wu, Di; Sun, Wei-Ming; Li, Ying; Li, Zhi-Ru

2014-11-18

280

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

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

Windelborn, James A; Lipton, Peter

2008-07-01

 
 
 
 
281

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

International Nuclear Information System (INIS)

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

282

Effect of ABT + S3307 on sugar metabolism and adventitious root in cuttings of Dendrocalamus spp  

International Nuclear Information System (INIS)

Application of ABT + S3307 to the cuttings of Dendrocalamus spp. promoted the sucrase activity. The contents of sucrose and starch in the cuttings based and the first node were decreased. Compared with the control, the content of reducing sugar was increased obviously in the cutting based. The transportation of 3H-glucose from labeled site to the base in treated cuttings was increased with the adventitious root formation. At the same time, the contents of structural substance in the cuttings based and the adventitious root were raised. The high content of carbohydrate and reducing activity in the adventitious root were available for growth of the roots

283

Antiedematogenic and free radical scavenging activity of swertiamarin isolated from Enicostemma axillare.  

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Swertiamarin, a secoiridoid isolated from the ethyl acetate extract of Enicostemma axillare, was evaluated for antiedematogenic activity using carrageenan-, formalin-, and histamine-induced paw edema methods in rats. In the carrageenan-induced method, the percentages of edema inhibition obtained after 5 h induction were 38.60, 52.50, and 45.44, respectively, for 100 and 200 mg/kg bw swertiamarin and 100 mg/kg bw of standard diclofenac sodium given orally. The activity of swertiamarin at 200 mg/kg bw was found to be superior to that of standard diclofenac sodium in all these methods. Swertiamarin was also screened for IN VITRO antioxidant activity using seven different methods: good activity was observed in ABTS and hydrogen peroxide methods, and moderate activity was observed in hydroxyl radical by deoxyribose and lipid peroxidation methods, with IC50 values of 2.83, 5.70, 52.56, and 78.33 microg/mL, respectively. The total antioxidant capacity was found to be 4.51 mM of ascorbic acid per gram of swertiamarin. Swertiamarin possesses antiedematogenic and in vitro antioxidant activities, and it may be the active constituent responsible for the anti-inflammatory activity of E. AXILLARE. PMID:19006050

Vaijanathappa, Jaishree; Badami, Shrishailappa

2009-01-01

284

Roaming Radicals  

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Roaming is a recently verified unusual pathway to molecular products from unimolecular dissociation of an energized molecule. Here we present the evidence for this pathway for H2CO and CH3CHO. Theoretical analysis shows that this path visits the plateau region of the potential energy surface near dissociation to radical products. It is not clear whether roaming is a distinct isolated pathway, in addition to the conventional one via the well-known molecular saddle-point transition state. Evidence is presented to suggest that the two pathways may originate from a single, but highly complicated, dividing surface. Other examples of unusual reaction dynamics are also reviewed.

Bowman, Joel M.; Shepler, Benjamin C.

2011-05-01

285

Development of methods for determining organic free radical structures by electron spin resonance and application to the radiation chemistry of nucleic acid model compounds  

International Nuclear Information System (INIS)

This project was undertaken with the objective of developing more efficient and reliable methods for the analysis of free radicals in organic single crystals. A technique was developed for the rapid calculation of single crystal ESR line positions and intensities. This method, which avoids the time-consuming matrix operations required by conventional methods, has been incorporated into a computer program for determining ESR parameters by the least-squares fitting of digitized ESR spectra. This program has been used to analyze complex spectra arising from a . CH2-CH2-O-PO3H- radical trapped in O-phosphorylethanolamine. A method was developed for the estimation of variance and covariance of eigenvectors and eigenvalues of experimentally-determined tensors. This error analysis is quite general, and may be applied to any tensors which can be determined by the non-linear least-squares fitting of ESR data. Monte-Carlo simulations have been employed to estimate the limitations of the approximation method. This error analysis has been included in the analysis of two phosphite radicals, -O2-P-OX, found in single crystals of O-phosphorylethanolamine. To aid in the formulation and evaluation of free radical models, a generalized method for the calculation of theoretically-expected hyperfine coupling tensors for arbitrary radical models was developed. Tensors are calculated for a furan-type radical which may be found in 5' dCMP. These calculated tensors are compared with tensors determined by an ENDOR experiment. Two ENDOR studies were done, one in 5' dCMP, the other in L-asparagine. The observed radical in 5' dCMP is allylic, characterized by coupling to three ?-hydrogens. In L-asparagine, the dominant room-temperature radical has the form CO(NH2)CHCH(N+H3)CO2-. In both these studies, a series of molecular orbital calculations were performed as a means of substantiating the postulated radical structures

286

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

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

Susceptibilities of Haemophilus influenzae and Moraxella catarrhalis to ABT-773 compared to their susceptibilities to 11 other agents.  

Science.gov (United States)

The activity of the ketolide ABT-773 against Haemophilus and Moraxella was compared to those of 11 other agents. Against 210 Haemophilus influenzae strains (39.0% beta-lactamase positive), microbroth dilution tests showed that azithromycin and ABT-773 had the lowest MICs (0.5 to 4.0 and 1.0 to 8.0 microg/ml, respectively), followed by clarithromycin and roxithromycin (4.0 to >32.0 microg/ml). Of the beta-lactams, ceftriaxone had the lowest MICs (32.0 microg/ml). Against 50 Moraxella catarrhalis strains, all of the compounds except amoxicillin and cefprozil were active. Time-kill studies against 10 H. influenzae strains showed that ABT-773, at two times the MIC, was bactericidal against 9 of 10 strains, with 99% killing of all strains at the MIC after 24 h; at 12 h, ABT-773 gave 90% killing of all strains at two times the MIC. At 3 and 6 h, killing by ABT-773 was slower, with 99.9% killing of four strains at two times the MIC after 6 h. Similar results were found for azithromycin, with slightly slower killing by erythromycin, clarithromycin, and roxithromycin, especially at earlier times. beta-Lactams were bactericidal against 8 to 10 strains at two times the MIC after 24 h, with slower killing at earlier time periods. Most compounds gave good killing of five M. catarrhalis strains, with beta-lactams killing more rapidly than other drugs. ABT-773 and azithromycin gave the longest postantibiotic effects (PAEs) of the ketolide-macrolide-azalide group tested (4.4 to >8.0 h), followed by clarithromycin, erythromycin, and roxithromycin. beta-Lactam PAEs were similar and shorter than those of the ketolide-macrolide-azalide group for all strains tested. PMID:11120946

Credito, K L; Lin, G; Pankuch, G A; Bajaksouzian, S; Jacobs, M R; Appelbaum, P C

2001-01-01

289

MLN2238 synergizes BH3 mimetic ABT-263 in castration-resistant prostate cancer cells by induction of NOXA.  

Science.gov (United States)

Patients undergoing androgen blockade therapy develop castration-resistant prostate cancer (CRPC), which is associated with Bcl-2 upregulation and results in disease progression and death. In recent years, promising therapeutic agents, such as the BH3-only mimetic ABT-263 and proteasome inhibitors, have been developed and widely evaluated against a broad spectrum of cancer types, including prostate cancer, alone or in combination with other chemotherapeutic agents. In this study, the antitumor efficacy of ABT-263 and MLN2238 were evaluated as single agents and in combination in four CRPC cell lines: PC3, C4-2B, C4-2, and DU145. The viability of the treated cells and markers of apoptosis were assayed. Protein-protein interactions were analyzed by co-immunoprecipitation in drug-treated cells. Lentivirus-mediated short hairpin RNA was used to knockdown Bax, Mcl-1, and NOXA expressions. We found that ABT-263 and MLN2238 alone exhibited a mild cytotoxicity, and in combination, they elicited a synergistic cytotoxic effect in CRPC cells. The cell apoptosis induced by the combination drug treatment was evidenced by enhanced caspase-3 and Poly (ADP-ribose) polymerase (PARP) cleavage, and annexin-V-positive staining was significantly depleted by Bax knockdown. MLN2238 treatment upregulated NOXA and Mcl-1 expression, leading NOXA/Mcl-1 complexes to disassociate Bak from its complexes with Mcl-1 and enhancing ABT263-triggered Bax activation. NOXA knockdown by short hairpin RNA significantly attenuated the cytotoxicity of ABT-263 and MLN2238 co-administration. In conclusion, MLN2238 and ABT-263 synergistically triggered apoptosis in CRPC cells by upregulating NOXA and activating Bax, indicating a promising therapeutic strategy for the treatment of CRPC. PMID:25027405

Wei, Xinghua; Zhou, Ping; Lin, Xuanting; Lin, Yurong; Wu, Sifeng; Diao, Pengfei; Xie, Haiqing; Xie, Keji; Tang, Ping

2014-10-01

290

Chemical repair of trypsin-histidinyl radical  

International Nuclear Information System (INIS)

Oxyl radicals, such as hydroxyl, alkoxyl and peroxyl, react with biomolecules to produce bioradicals. Unless chemically repaired by suitable antioxidants, these bioradicals form stable products. This leads to loss of biological function of parent biomolecules with deleterious biological results, such as mutagenesis and cancer. Consequently, the understanding of the mechanisms of oxyl radical damage to biomolecules and chemical repair of such damage is crucial for the development of strategies for anticarcinogenesis and radioprotection. In this study the chemical repair of the histidinyl radical generated upon the trichloromethylperoxyl radical reaction with trypsin vas investigated by gamma radiolysis. The trypsin histidinyl radical is a resonance-stabilized heterocyclic free radical which was found to be unreactive with oxygen. The efficacy of the chemical repair of the trypsin-histidinyl radical by endogenous antioxidants which are electron donors (e.g. 5-hydroxytryptophan, uric acid) is compared to that of antioxidants which are H-atom donors (e. g. glutathione). 9 refs., 2 figs., 1 tab

291

Implications for degenerative disorders: antioxidative activity, total phenols, flavonoids, ascorbic acid, beta-carotene and beta-tocopherol in Aloe vera.  

Science.gov (United States)

In order to demonstrate whether the known biological effects of Aloe vera (L.) Burm. fil. could correlate with the antioxidant activity of the plant, the antioxidant activity of the aqueous leaf extract was investigated. The present study demonstrated that the aqueous extract from A. vera leaves contained naturally occuring antioxidant components, including total phenols, flavonoids, ascorbic acid, beta-carotene and alpha-tocopherol. The extract exhibited inhibitory capacity against Fe(3+)/ascorbic acid induced phosphatidylcholine liposome oxidation, scavenged stable DPPH(*), ABTS(*+) and superoxide anion radicals, and acted as reductant. In contrast, the leaf inner gel did not show any antioxidant activity. It was concluded that the known beneficial effects of Aloe vera could be attributed to its antioxidant activity and could be related to the presence of phenolic compounds and antioxidant vitamins. PMID:20357932

Ozsoy, Nurten; Candoken, Eda; Akev, Nuriye

2009-01-01

292

Evaluation of Free Radical Scavenging Activity of Pandanus odoratissimus  

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Full Text Available Pandanus odoratissimus is used in traditional medicinal and it is also famous for its fragency. The present study was performed to evaluate the methanolic effect of Pandanus odoratissimus (MEPO against free radical damage. The antioxidant activity of has MEPO been studied using its ability to scavenging DPPH, Nitric acid, superoxide radicals and hydroxyl radicals. The MEPO shows antioxidant activity by 87.52% reducing the DPPH and 73.55% inhibition of nitric acid. The result also indicates maximum inhibition of superoxide radical’s inhibition 74.12 and 78.14% inhibition of hydroxyl radicals. The BHT was used as standard.

R. Londonkar

2009-01-01

293

Chitosan-hydroxycinnamic acid conjugates: preparation, antioxidant and antimicrobial activity.  

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In this study, the antioxidant and antimicrobial activities of chitosan-caffeic acid, chitosan-ferulic acid, and chitosan-sinapic acid conjugates with different grafting ratios were investigated. The synthesized chitosan-hydroxycinnamic acid conjugates were verified by performing (1)H NMR and differential scanning calorimetry analysis. The antioxidant activities of the conjugates were increased compared to the unmodified chitosan, by 1.79-fold to 5.05-fold (2,2-diphenyl-1-picrylhydrazyl scavenging assay), 2.44-fold to 4.12-fold (hydrogen peroxide scavenging assay), 1.34-fold to 3.35-fold (ABTS(+) radical scavenging assay), and also exhibited an increased reducing power. The conjugates also showed excellent lipid peroxidation inhibition abilities in a linoleic acid emulsion system. The conjugates exhibited antimicrobial activity against 15 clinical isolates, two standard methicillin-resistant Staphylococcus aureus (MRSA) and three standard methicillin-susceptible S. aureus strains, as well as eight foodborne pathogens. Additionally, the conjugates showed no cytotoxic activity towards human Chang liver and mouse macrophage RAW264.7 cells. PMID:24262532

Lee, Dae-Sung; Woo, Ji-Young; Ahn, Chang-Bum; Je, Jae-Young

2014-04-01

294

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

295

Synthesis and structure-activity relationships of a novel series of HIV-1 protease inhibitors encompassing ABT-378 (Lopinavir).  

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The HIV protease inhibitor ABT-378 (Lopinavir) has a 2,6-dimethylphenoxyacetyl group in the P-2' position. Analogues in which this group is replaced with various substituted phenyl or heteroaryl groups were synthesized and the structure-activity relationships explored. PMID:11934584

Sham, Hing L; Betebenner, David A; Chen, Xiaoqi; Saldivar, Ayda; Vasavanonda, Sudthida; Kempf, Dale J; Plattner, Jacob J; Norbeck, Daniel W

2002-04-22

296

Rapid detection of an ABT-737-sensitive primed for death state in cells using microplate-based respirometry.  

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Cells that exhibit an absolute dependence on the anti-apoptotic BCL-2 protein for survival are termed "primed for death" and are killed by the BCL-2 antagonist ABT-737. Many cancers exhibit a primed phenotype, including some that are resistant to conventional chemotherapy due to high BCL-2 expression. We show here that 1) stable BCL-2 overexpression alone can induce a primed for death state and 2) that an ABT-737-induced loss of functional cytochrome c from the electron transport chain causes a reduction in maximal respiration that is readily detectable by microplate-based respirometry. Stable BCL-2 overexpression sensitized non-tumorigenic MCF10A mammary epithelial cells to ABT-737-induced caspase-dependent apoptosis. Mitochondria within permeabilized BCL-2 overexpressing cells were selectively vulnerable to ABT-737-induced cytochrome c release compared to those from control-transfected cells, consistent with a primed state. ABT-737 treatment caused a dose-dependent impairment of maximal O(2) consumption in MCF10A BCL-2 overexpressing cells but not in control-transfected cells or in immortalized mouse embryonic fibroblasts lacking both BAX and BAK. This impairment was rescued by delivering exogenous cytochrome c to mitochondria via saponin-mediated plasma membrane permeabilization. An ABT-737-induced reduction in maximal O(2) consumption was also detectable in SP53, JeKo-1, and WEHI-231 B-cell lymphoma cell lines, with sensitivity correlating with BCL-2:MCL-1 ratio and with susceptibility (SP53 and JeKo-1) or resistance (WEHI-231) to ABT-737-induced apoptosis. Multiplexing respirometry assays to ELISA-based determination of cytochrome c redistribution confirmed that respiratory inhibition was associated with cytochrome c release. In summary, cell-based respiration assays were able to rapidly identify a primed for death state in cells with either artificially overexpressed or high endogenous BCL-2. Rapid detection of a primed for death state in individual cancers by "bioenergetics-based profiling" may eventually help identify the subset of patients with chemoresistant but primed tumors who can benefit from treatment that incorporates a BCL-2 antagonist. PMID:22880001

Clerc, Pascaline; Carey, Gregory B; Mehrabian, Zara; Wei, Michael; Hwang, Hyehyun; Girnun, Geoffrey D; Chen, Hegang; Martin, Stuart S; Polster, Brian M

2012-01-01

297

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

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Tumor initiation, progression and resistance to therapies are tightly associated with over-expression of anti-apoptotic proteins Bcl-2, Bcl-xL , 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-xL , 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-xL 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

2015-02-15

298

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

299

Effects of the cognition-enhancing agent ABT-239 on fetal ethanol-induced deficits in dentate gyrus synaptic plasticity.  

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Prenatal ethanol exposure causes deficits in hippocampal synaptic plasticity and learning. At present, there are no clinically effective pharmacotherapeutic interventions for these deficits. In this study, we examined whether the cognition-enhancing agent 4-(2-{2-[(2R)-2-methylpyrrolidinyl]ethyl}-benzofuran-5-yl) benzonitrile (ABT-239), a histamine H(3) receptor antagonist, could ameliorate fetal ethanol-induced long-term potentiation (LTP) deficits. Long-Evans rat dams consumed a mean of 2.82 g/kg ethanol during a 4-h period each day. This voluntary drinking pattern produced a mean peak serum ethanol level of 84 mg/dl. Maternal weight gain, offspring litter size, and birth weights were not different between ethanol-consuming and control groups. A stimulating electrode was implanted in the entorhinal cortical perforant path, and a recording electrode was implanted in the dorsal dentate gyrus of urethane-anesthetized adult male offspring. Baseline input/output responses were not affected either by prenatal ethanol exposure or by 1 mg/kg ABT-239 administered 2 h before data collection. No differences were observed between prenatal treatment groups when a 10-tetanus train protocol was used to elicit LTP. However, LTP elicited by 3 tetanizing trains was markedly impaired by prenatal ethanol exposure compared with control. This fetal ethanol-induced LTP deficit was reversed by ABT-239. In contrast, ABT-239 did not enhance LTP in control offspring using the 3-tetanus train protocol. These results suggest that histamine H(3) receptor antagonists may have utility for treating fetal ethanol-associated synaptic plasticity and learning deficits. Furthermore, the differential effect of ABT-239 in fetal alcohol offspring compared with controls raises questions about the impact of fetal ethanol exposure on histaminergic modulation of excitatory neurotransmission in affected offspring. PMID:20308329

Varaschin, Rafael K; Akers, Katherine G; Rosenberg, Martina J; Hamilton, Derek A; Savage, Daniel D

2010-07-01

300

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

 
 
 
 
301

Reactions of radicals in gamma-irradiated polymethyl methacrylate  

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The reactions of radicals formed by 60Co irradiation in polymethyl methacrylate and copolymers of methyl methacrylate and methacrylic acid (70/30) have been investigated. Additional radical formation was found to occur with increasing temperature, amounting to 10% of the radical formation by ?-radiolysis. The validity of the model of a wide distribution of reaction rates is discussed. (author)

302

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

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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.)

303

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)  

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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

304

Synthesis and biological evaluation of new 1,3-thiazolidine-4-one derivatives of 2-(4-isobutylphenyl)propionic acid.  

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New thiazolidine-4-one derivatives of 2-(4-isobutylphenyl)propionic acid (ibuprofen) have been synthesized as potential anti-inflammatory drugs. The structure of the new compounds was proved using spectral methods (FR-IR, 1H-NMR, 13C-NMR, MS). The in vitro antioxidant potential of the synthesized compounds was evaluated according to the total antioxidant activity, the DPPH and ABTS radical scavenging assays. Reactive oxygen species (ROS) and free radicals are considered to be involved in many 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. PMID:25237755

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

2014-01-01

305

A randomized, double-blind, placebo-controlled trial evaluating the efficacy and safety of ABT-594 in patients with diabetic peripheral neuropathic pain.  

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ABT-594 is a neuronal nicotinic acetylcholine receptor (NNR) agonist that exhibits potent analgesic activity in preclinical models of acute, chronic, and neuropathic pain. The purpose of this phase 2, randomized, multicenter, double-blind, placebo-controlled study was to evaluate the safety and analgesic efficacy of ABT-594 in patients with diabetic peripheral neuropathic pain (DPNP). A total of 266 DPNP patients were randomized 1:1:1:1 to receive placebo, ABT-594 150 microg BID, ABT-594 225 microg BID, or ABT-594 300 microg BID. Patients were titrated to a fixed-dose of ABT-594 over 7 days and remained at this dose for another 6 weeks. Compared to placebo, all three ABT-594 treatment groups showed significantly greater decreases on the average diary-based 0-10 Pain Rating Scale (PRS) score from baseline to final evaluation, the primary efficacy measure (placebo, -1.1; 150 microg BID, -1.9; 225 microg BID, -1.9; 300 microg BID, -2.0). The proportion of patients achieving at least a 50% improvement in the average diary-based PRS was greater in all three ABT-594 treatment groups. However, adverse event (AE) dropout rates were significantly higher in all three ABT-594 treatment groups (28% for 150 microg BID, 46% for 225 microg BID, and 66% for 300 microg BID) than for the placebo group (9%). Consistent with the expected side-effect profile of NNR agonists, the most frequently reported AEs were nausea, dizziness, vomiting, abnormal dreams, and asthenia. This study establishes proof of concept for NNR agonists as a new class of compounds for treating neuropathic pain. PMID:19632048

Rowbotham, Michael C; Duan, W Rachel; Thomas, James; Nothaft, Wolfram; Backonja, Misha-Miroslav

2009-12-01

306

Nanoencapsulation of ABT-737 and camptothecin enhances their clinical potential through synergistic antitumor effects and reduction of systemic toxicity.  

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The simultaneous delivery of multiple cancer drugs in combination therapies to achieve optimal therapeutic effects in patients can be challenging. This study investigated whether co-encapsulation of the BH3-mimetic ABT-737 and the topoisomerase I inhibitor camptothecin (CPT) in PEGylated polymeric nanoparticles (NPs) was a viable strategy for overcoming their clinical limitations and to deliver both compounds at optimal ratios. We found that thrombocytopenia induced by exposure to ABT-737 was diminished through its encapsulation in NPs. Similarly, CPT-associated leukopenia and gastrointestinal toxicity were reduced compared with the administration of free CPT. In addition to the reduction of dose-limiting side effects, the co-encapsulation of both anticancer compounds in a single NP produced synergistic induction of apoptosis in both in vitro and in vivo colorectal cancer models. This strategy may widen the therapeutic window of these and other drugs and may enhance the clinical efficacy of synergistic drug combinations. PMID:25299779

Schmid, D; Jarvis, G E; Fay, F; Small, D M; Greene, M K; Majkut, J; Spence, S; McLaughlin, K M; McCloskey, K D; Johnston, P G; Kissenpfennig, A; Longley, D B; Scott, C J

2014-01-01

307

Effects of the histamine H3 receptor antagonist ABT-239 on acute and repeated nicotine locomotor responses in rats.  

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The addictive potential of nicotine is linked to psychomotor and cognition-enhancing effects. Histamine (H)(3) receptor antagonism has similarly received attention for a role in cognition, however, the role of H(3) receptors are far less studied for affects on nicotine-induced locomotor responses. In the present study we tested whether the H(3) receptor antagonist 4-(2-{2-[(2R)-2 methylpyrrolidinyl] ethyl}-benzofuran-5-yl) benzonitrile (ABT-239) influenced the psychomotor responses to acute and repeated nicotine, including sensitization and conditioned locomotion. ABT-239 (0.3-3 mg/kg) did not alter basal, nicotine-evoked (0.4 mg/kg) locomotor responses, the expression of sensitization, or cue-conditioned locomotion. However, in combination studies rats pretreated with a separate dose of ABT-239 (1 mg/kg) prior to nicotine (0.4 mg/kg) for 5 days and then challenged with nicotine (0.4 mg/kg) after a 5-day withdrawal period, showed significantly higher locomotor hyperactivity in comparison with the effect observed in nicotine-pretreated and challenged rats. Our findings implicate a limited role for H(3) receptors in locomotor responses to nicotine. PMID:22358104

Miszkiel, Joanna; Kruk, Marta; McCreary, Andrew C; Przegali?ski, Edmund; Bia?a, Gra?yna; Filip, Ma?gorzata

2011-01-01

308

Two radical neuron doctrines  

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Two radical neuron doctrines must be distinguished--strong and weak. G&S direct much of their attack at the former--but the Churchlands only hold the latter. The weak radical neuron doctrine remains a serious possibility.

Hilbert, David R.; Byrne, Alex

1999-01-01

309

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

310

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

311

Effect of Bucillamine on Free-Radical-Mediated Degradation of High-Molar-Mass Hyaluronan Induced in vitro by Ascorbic Acid and Cu(II Ions  

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Full Text Available The bucillamine effect on free-radical-mediated degradation of high-molar-mass hyaluronan (HA has been elucidated. As HA fragmentation is expected to decrease its dynamic viscosity, rotational viscometry was applied to follow the oxidative HA degradation. Non-isothermal chemiluminometry, thermogravimetry, differential scanning calorimetry, and size-exclusion chromatography (SEC were applied to characterize resulting HA fragments. Although bucillamine completely inhibited the HA viscosity decrease caused by oxidative system, indicating HA protection from degradation, SEC analysis suggested that some other mechanisms leading to the bucillamine transformations without the decay of the viscosity may come into a play as well. Nonetheless, the link between the reduction of chemiluminescence intensity and disappearance of the differential scanning calorimetry exotherm at 270 °C for fragmented HAs indicates a particular role of the bucillamine in preventing the decrease of HA viscosity.

Mária Ba?asová

2014-10-01

312

Reactions of melatonin with radicals in deoxygenated aqueous solution  

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Reactions of melatonin (N-acetyl-5-methoxytryptamine) with radiolytically generated radicals were studied. Reaction of melatonin with OH radicals is diffusion-controlled (k=1.2 x 1010 dm3 mol-1 x s-1), the main (but not the only one) intermediate being the indolyl-type radical, while the rate constant for the reaction with hydrated electrons is k=4.3 x 108 dm3 x mol-1 x s-1. Melatonin is capable of scavenging tert-butanol radicals, while its reactivity towards polymer radicals of poly(acrylic acid) and poly(vinyl pyrrolidone) is very low. (author)

313

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

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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

314

Chemical composition, fatty acid content and antioxidant potential of meat from goats supplemented with Moringa (Moringa oleifera) leaves, sunflower cake and grass hay.  

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The present study determined the chemical composition, fatty acid (FA) content and antioxidant capacity of meat from goats supplemented with Moringa oleifera leaves (MOL) or sunflower cake (SC) or grass hay (GH). The meat from goat supplemented with MOL had higher concentrations of total phenolic content (10.62±0.27 mg tannic acid equivalent E/g). The MOL significantly scavenged 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic-acid (ABTS) radical to 93.51±0.19% (93.51±0.19%) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical to 58.95±0.3% than other supplements. The antioxidative effect of MOL supplemented meat on catalase (CAT), reduced glutathione (GSH), superoxide dismutase (SOD) and lipid oxidation (LO) was significantly (P<0.05) higher than other meat from goat feed on grass hay or those supplemented with sunflower seed cake. The present study indicated that the anti-oxidative potential of MOL may play a role in improving meat quality (chemical composition, colour and lipid stability). PMID:23273450

Qwele, K; Hugo, A; Oyedemi, S O; Moyo, B; Masika, P J; Muchenje, V

2013-03-01

315

Characterization of pH-responsive hydrogels of poly(itaconic acid-g-ethylene glycol) prepared by UV-initiated free radical polymerization as biomaterials for oral delivery of bioactive agents.  

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Effective oral delivery of proteins is impeded by steep pH gradients and proteolytic enzymes in the gastrointestinal tract, as well as low absorption of the proteins into the bloodstream because of their size, charge, or solubility. In this work, pH-responsive complexation hydrogels of poly(itaconic acid) (PIA) with poly(ethylene glycol) (PEG) grafts were synthesized for applications in oral drug delivery. These hydrogels were expected to be in collapsed configuration at low pH because of hydrogen bonding between PIA carboxyl groups and PEG, and to swell with increasing pH because of charge repulsion between deprotonated carboxylic acid groups. Hydrogels were prepared by UV-initiated free radical polymerization using tetraethylene glycol as the crosslinking agent and Irgacure 2959 as the initiator. The effect of monomer ratios, crosslinking ratio, and solvent amount on the properties of the hydrogels were investigated. The composition of the hydrogels was confirmed by Fourier transform infrared spectroscopy. Equilibrium swelling studies in the pH range of 1.2-7 revealed that the extent of swelling increased with increasing pH up to a pH of about 6, when no further carboxylic acid deprotonation occurred. Studies in Caco-2 colorectal carcinoma cells confirmed the cytocompatibility of these materials at concentrations of up to 5 mg/mL. PMID:19536838

Betancourt, Tania; Pardo, Juan; Soo, Ken; Peppas, Nicholas A

2010-04-01

316

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

317

Radiation induced reactions involving sulfur-centered radicals  

International Nuclear Information System (INIS)

Complete text of publication follows. Sulfur-centered radicals represent an important class of radicals since they exhibit very interesting redox chemistry, including biological redox processes, and different spectral and kinetic properties as compared to carbon-centered radicals. This is due to the fact that the lone electron pairs present in sulfur atom influenced on the overall electronic structure of radicals. In the past few years unprecedented progress has been made in the recognition and understanding the role of structures and reaction mechanisms of sulfur-centered radicals. Research on these transients flourished particularly in systems that are relevant in biology, biochemistry and medicine. Relevant examples will highlight only the very recent achievements emerging from radiation chemical studies. These include radical processes connected with the intramolecular addition of cysteine thiyl radicals (CysS·) to phenylalanine, reversible H-atom transfer between CysS· and amino acids within a peptide chain, addition reaction of thiyl radicals (RS·) involving double bonds in pyrimidines, RS·-catalyzed cis/trans isomerization of lipid double bonds in unsaturated fatty acids, ·OH and ·H-induced degradation of molecules containing sulfur atoms, stabilization of monomeric sulfur radical cations (>S+·) with peptide bonds, and stabilization of disulfide radical anions (>S.·.S<) in uracil-derived disulfides. Important outputs from these studies are new directions for improving our knowledge how sulfur-centered radicals interact with major cellular targets during oxidative stress, i.e. proteins, DNA and lipids.

318

Preparation and study of dialkyl nitroxide radicals  

International Nuclear Information System (INIS)

These radicals are obtained by oxidation of N-hydroxy-imides with lead tetracetate or p-nitro-perbenzoic acid. These imides are prepared by heating dicarboxylic acids anhydrides with benzyloxy-amine followed by catalytic hydrogenation of N-benzyloxy-imides so obtained. Two series of radicals have mainly been studied, the first concerning five-membered cyclic imides, the second six-membered cyclic imides, these molecules having methyls substituents or no on the carbon ring. N. M. R. spectra of some O-benzyl-imides have been analysed. These different results have made it possible to study the conformation and stereochemistry of these imides. (author)

319

Gamut of alkoxy radicals  

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It is shown that various radicals exhibiting diverse ESR and ENDOR spectral characteristics are nonetheless a closely related family of alkoxy radicals. The relationship is established by correlating the g tensor with crystal structure and by relating dihedral angles inferred from proton hyperfine couplings to dihedral angles inferred from the g tensor and crystal structure. The analysis also serves to demonstrate that an ESR absorption observed in x-irradiated single crystals of uridine 5'-monophosphate is due to an alkoxy radical

320

Reactions of alkoxy radicals in aqueous solutions  

International Nuclear Information System (INIS)

The kinetic and mechanistic properties of alkoxy radicals in organic solvents are briefly reviewed. Owing to the scarcity of such data in aqueous solutions and since reactions at the membrane/water interface may be also biologically important, we have studied the reactivity of these radicals in water and the results of our investigations are reported. Alkoxy radicals were generated by photolytic or radiolytic cleavage of peroxide precursors (tert-butyl hydroperoxide and di-tert-butyl peroxide as well as hydroperoxides of polyunsaturated fatty acids). A quantitative correlation between the structure of various substances, in particular, phenolic antioxidants, and their activity in inhibiting the alkoxy radical-induced bleaching of the water-soluble carotenoid crocin will be discussed. Rate constants for intermolecular reactions of t-BuO. radicals were determined by pulse radiolysis. The diffusion-controlled reaction with the catechol antioxidant nordihydroguaiaretic acid demonstrates an effective competition with the very rapid intra molecular ?-fragmentation in water. The results aupport the view that a considerable amount of alkoxy radicals interact with substrates before they can rearrange intramolecularly

 
 
 
 
321

Reactions of alkoxy radicals in aqueous solutions  

Energy Technology Data Exchange (ETDEWEB)

The kinetic and mechanistic properties of alkoxy radicals in organic solvents are briefly reviewed. Owing to the scarcity of such data in aqueous solutions and since reactions at the membrane/water interface may be also biologically important, we have studied the reactivity of these radicals in water and the results of our investigations are reported. Alkoxy radicals were generated by photolytic or radiolytic cleavage of peroxide precursors (tert-butyl hydroperoxide and di-tert-butyl peroxide as well as hydroperoxides of polyunsaturated fatty acids). A quantitative correlation between the structure of various substances, in particular, phenolic antioxidants, and their activity in inhibiting the alkoxy radical-induced bleaching of the water-soluble carotenoid crocin will be discussed. Rate constants for intermolecular reactions of t-BuO. radicals were determined by pulse radiolysis. The diffusion-controlled reaction with the catechol antioxidant nordihydroguaiaretic acid demonstrates an effective competition with the very rapid intra molecular ..beta..-fragmentation in water. The results aupport the view that a considerable amount of alkoxy radicals interact with substrates before they can rearrange intramolecularly.

Bors, W.; Tait, D.; Michel, C.; Saran, M.; Erben-Russ, M. (Gesellschaft fuer Strahlen- und Umweltforschung m.b.H. Muenchen, Neuherberg (Germany, F.R.). Abt. fuer Strahlenbiologie)

1984-01-01

322

Radical Scavenging Effects of Different Veronica species  

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Full Text Available It is well known that the excessive production of reactive oxygen species is hazardous for living organisms and damages major cellular constituents such as DNA, lipid and protein. To find new products reducing free radical damage is very important researches in recent pharmaceutical investigations. Considering this information, fourteen Veronica species are decided to research in the view point of their antioxidant capacity and the chemical content. Water extracts of the plants were tested for their radical scavenging activity against 2,2-diphenyl-1-picryl hydrazyl (DPPH, superoxide (SO and nitric oxide (NO radicals spectroscopically. Dose dependent radical scavenging activity was observed and the results were found to be comparable to that of ascorbic acid, quercetin and BHA which are known antioxidative compounds. In addition, gallic acid equivalent total phenolic contents of the plants were also determined using Folin-Ciocalteau reagent. The most significant scavenging activity was found for V. chamaedrys against SO radical (IC50 113.40 ?g/ml and V. officinalis against DPPH and NO radicals (IC50 40.93 ?g/ml, 570.33 ?g/ml, respectively .

Ummuhan ?ebnem Harput

2011-01-01

323

Local administration of lactic acid and a low dose of the free radical scavenger, edaravone, alleviates myocardial reperfusion injury in rats.  

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The effects of local myocardial administration of lactic acid and low-dose edaravone were investigated to determine if this combination provides benefits similar to mechanical postconditioning. We randomly divided 108 rats into 6 groups: sham, reperfusion injury, postconditioning (Post), lactic acid (Lac), low-dose edaravone (Eda), and lactic acid + low-dose edaravone (Lac+Eda). The left coronary arteries of the rats were occluded for 45 minutes, before the administration of the treatments. The rats were euthanized at different time points to examine the infarct size and serum markers of myocardial injury and apoptosis and measure the expression of signal pathway markers. We found that the infarct areas caused by ischemic-reperfusion injury were reduced largely by postconditioning and Lac+Eda injection; a similar trend was observed for serum markers of myocardial injury, apoptosis, and hemodynamic parameters. Compared with the Post group, the Lac+Eda group had similar blood pH values, levels of reactive oxygen species, mitochondrial absorbance, and levels of signal pathway marker. The Lac and Eda groups partly mimicked the protective role. These data suggest that local myocardial administration of lactic acid and low dose of edaravone initiates protective signal pathways of mechanical postconditioning and replicates the myocardial protection. PMID:23884160

Zhang, Guoming; Sun, Yuanyuan; Wang, Yu; Li, Xiaoyan; Li, Tiande; Su, Shaoping; Xu, Lin; Shen, Hong

2013-10-01

324

Free radical scavenging activity of papaya juice  

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Papaya juice is an efficient scavenger of highly reactive hydroxyl radicals (OH radical) formed during /sup 60/Co irradiation of water. The OH anion radicals were detected by the electron spin resonance (ESR) technique of spin trapping using DMPO (5,5-dimethyl-1-pyrroline-N-oxide) or by a colorimetric assay in which salicylate is converted into polyhydroxybenzoic acids. Papaya juice is also able to quench the ESR signal of a stable free radical (TEMPOL) and the ESR signal of the DMPO-OH adduct. The active substance(s) in papaya juice are heat-stable, dialyzable, and soluble in water but not in lipid solvents. The active agents do not appear to be ascorbate, tocopherol, or carotenoids.

Webman, E.J.; Mower, H.F.; Edlin, Gordon

1989-03-01

325

Free radical scavenging activity of papaya juice  

International Nuclear Information System (INIS)

Papaya juice is an efficient scavenger of highly reactive hydroxyl radicals (OH radical) formed during 60Co irradiation of water. The OH anion radicals were detected by the electron spin resonance (ESR) technique of spin trapping using DMPO (5,5-dimethyl-1-pyrroline-N-oxide) or by a colorimetric assay in which salicylate is converted into polyhydroxybenzoic acids. Papaya juice is also able to quench the ESR signal of a stable free radical (TEMPOL) and the ESR signal of the DMPO-OH adduct. The active substance(s) in papaya juice are heat-stable, dialyzable, and soluble in water but not in lipid solvents. The active agents do not appear to be ascorbate, tocopherol, or carotenoids. (author)

326

The kinetics of oxidation of GSH by protein radicals  

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Current studies provide evidence that proteins are initial targets of ROS (reactive oxygen species) in biological systems and that the damaged proteins can in turn damage other cell constituents. This study was designed to test the possibility that protein radicals generated by ROS can oxidize GSH and assess the probability of this reaction in vivo by measurement of the rate constant of this reaction. Lysozyme radicals were generated by hydroxyl and azide radicals in steady-state gamma ray radiolysis. In the absence of dioxygen, a range of protein carbon-centred amino acid radicals were produced by the hydroxyl radicals, and defined tryptophan radicals by the azide radicals. In the presence of dioxygen, each carbon-centred radical was converted to a protein peroxyl radical. Each of the peroxyl radicals was able to oxidize a molecule of GSH, regardless of its location in the protein. The peroxyl radicals were 10 and 20 times more effective GSH oxidants than the carbon-centred radicals produced randomly in the lysozyme, or the defined tryptophan lysozyme radicals respectively. We obtained for the first time the rate constant of reaction between a protein free-radical and GSH. Lysozyme tryptophan carbon radicals generated by nanosecond pulse radiolysis and flash photolysis oxidized GSH with a rate constant of (1.05±0.05)×105 M?1·s?1. Overall, the results are consistent with the hypothesis that protein radicals may be important intermediates in the pathway linking oxidative stress and damage in living organisms and emphasize the strongly enhancing role of dioxygen in this process. PMID:16086667

Nauser, Thomas; Koppenol, Willem H.; Gebicki, Janusz M.

2005-01-01

327

HOCO radical chemistry.  

Science.gov (United States)

Free radicals are important species in atmospheric chemistry, combustion, plasma environments, interstellar clouds, and biochemistry. Therefore, researchers would like to understand the formation mechanism, structure, stability, reactivity, spectroscopy, and dynamics of these chemical species. However, due to the presence of one or more unpaired electrons, radicals are often very reactive and have short lifetimes, which makes it difficult to conduct experiments. The HOCO radical appears in the atmosphere as well as in combustion environments and plays an important role in the conversion of CO to CO(2). Through the interplay between theoretical and experimental investigations, researchers have only recently understood the chemical role of the HOCO radical. In this Account, we systematically describe the current state of knowledge of the HOCO radical based on recent theoretical and experimental studies. This radical's two stable conformers, trans- and cis-HOCO, have been identified by high-level ab initio calculations and experimental spectroscopy. trans-HOCO is more stable by approximately 1.8 kcal/mol. The heat of formation of HOCO (298 K) was determined to be -43.0 ± 0.5 kcal/mol, giving a potential well depth of 30.1 ± 0.5 kcal/mol relative to the asymptote of the reactants OH + CO. The HOCO radical is very reactive. In most reactions between the HOCO radical and atoms, the HOCO radical acts as a hydrogen donor to reaction partners. Generally, the hydrogen is transferred through the formation of an association intermediate, which then proceeds through a molecular elimination step to produce the reaction products. The reaction rates of HOCO with some small radicals fall in the range of 10(-11)-10(-10) cm(3) molecule(-1) s(-1). These results clearly illustrate important features in the reactivity of the HOCO radical with other molecules. PMID:20929216

Francisco, Joseph S; Muckerman, James T; Yu, Hua-Gen

2010-12-21

328

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

329

Phytochemical Evaluation and in vitro Free Radical Scavenging Activity of Cold and Hot Successive Pseudobulb Extracts of Medicinally Important Orchid Flickingeria nodosa (Dalz. Seidenf  

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Full Text Available Flickingeria nodosa (Dalz. Seidenf is an epiphytic orchid with pseudobulbs which has medicinal importance in traditional system of medicine. In charak samhita it is known as Jeewanti which means life promoter. Based on its importance the present work was designed to evaluate its phytochemical constituents and free radical scavenging activity of pseudobulb cold and hot successive extracts. The phytochemical secondary metabolite screening of extracts revealed the presence of alkaloids, flavonoids, phenols, phytosterols and total antioxidant components. Based on the quantitative estimation studies it revealed that extracts have a good amount of secondary metabolites. The cold and hot successive extracts were subjected to free radical scavenging activity on DPPH, ABTS radical cation decolorization assay, Hydroxyl radical scavenging activity and Nitric oxide scavenging activity. The result revealed that the highest DPPH scavenging and ABTS scavenging activity was seen in the cold acetone extract, hydroxyl radical scavenging activity was more with hot chloroform extract and nitric oxide scavenging activity was more with cold water extracts. The plant can be a source material to herbal drug industry since it is a reservoir of phytochemical components that can be used for the development of therapeutic phytomedicine for the therapy and treatments.

Nalini Satishchandra

2013-01-01

330

Carbohydrate radicals: from ethylene glycol to DNA strand breakage.  

Science.gov (United States)

Radiation-induced DNA strand breakage results from the reactions of radicals formed at the sugar moiety of DNA. In order to elucidate the mechanism of this reaction investigations were first performed on low molecular weight model systems. Results from studies on deoxygenated aqueous solutions of ethylene glycol, 2-deoxy-d-ribose and other carbohydrates and, more relevantly, of d-ribose-5-phosphate have shown that substituents can be eliminated from the ?-position of the radical site either proton and base-assisted (as in the case of the OH substituent), or spontaneously (as in the case of the phosphate substituent). In DNA the C(4') radical undergoes strand breakage via this type of reaction. In the presence of oxygen the carbon-centred radicals are rapidly converted into the corresponding peroxyl radicals. Again, low molecular weights models have been investigated to elucidate the key reactions. A typical reaction of DNA peroxyl radicals is the fragmentation of the C(4')-C(S') bond, a reaction not observed in the absence of oxygen. Although OH radicals may be the important direct precursors of the sugar radicals of DNA, results obtained with poly(U) indicate that base radicals may well be of even greater importance. The base radicals, formed by addition of the water radicals (H and OH) to the bases would in their turn attack the sugar moiety to produce sugar radicals which then give rise to strand breakage and base release. For a better understanding of strand break formation it is therefore necessary to investigate in more detail the reactions of the base radicals. For a start, the radiolysis of uracil in oxygenated solutions has been reinvestigated, and it has been shown that the major peroxyl radical in this system undergoes base-catalysed elimination of [Formula: see text], a reaction that involves the proton at N(l). In the nucleic acids the pyrimidines are bound at N(l) to the sugar moiety and this type of reaction can no longer occur. Therefore, with respect to the nucleic acids, pyrimidines are good models only in acid solutions where the [Formula: see text] elimination reaction is too slow to compete with the bimolecular reactions of the peroxyl radicals. Moreover, the long lifetime of the radical sites on the nucleic acid strand may allow reactions to occur which are kinetically of first order, and which cannot be studied in model systems at ordinary dose rates. It is therefore suggested to extend model system studies to low dose rates and to oligonucleo-tides. Such studies might eventually reveal the key reactions in radical-induced DNA degradation. PMID:24882513

von Sonntag, Clemens

2014-06-01

331

Muonium substituted free radicals  

International Nuclear Information System (INIS)

Muonium-substituted free radicals are observed by means of the ?SR technique when unsaturated liquids are irradiated with energetic positive muons. Formally, these radicals are derived by Mu addition to the unsaturated parent molecules. Determination of the frequencies of ?SR lines allows the identification of radical structures. The line amplitudes and widths are associated with the processes of formation and subsequent chemical reaction of the radicals. The major advances in the past year are the following: a) The relation between muon-electron hyperfine coupling constants Asub(?) and structures of methyl and fluorine substituted cyclohexadienyl type radicals was investigated. b) Fundamental radiation chemical processes govern the distribution of muons between the different observable muonic species. It was shown that the radical formation in methyl substituted butadienes is quite selective and affords a similar product distribution as it is known for the addition of thermal H atoms (chemically a heavy isotope of Mu). c) Most of the present effort is spent on the determination of rate constants of radical reactions from ?SR in line widths. (Auth.)

332

Salvage robotic radical prostatectomy.  

Science.gov (United States)

Failure of non-surgical primary treatment for localized prostate cancer is a common occurrence, with rates of disease recurrence ranging from 20% to 60%. In a large proportion of patients, disease recurrence is clinically localized and therefore potentially curable. Unfortunately, due to the complex and potentially morbid nature of salvage treatment, radical salvage surgery is uncommonly performed. In an attempt to decrease the morbidity of salvage therapy without sacrificing oncologic efficacy, a number of experienced centers have utilized robotic assistance to perform minimally invasive salvage radical prostatectomy. Herein, we critically evaluate the existing literature on salvage robotic radical prostatectomy with a focus on patient selection, perioperative complications and functional and early oncologic outcomes. These results are compared with contemporary and historical open salvage radical prostatectomy series and supplemented with insights we have gained from our experience with salvage robotic radical prostatectomy. The body of evidence by which conclusions regarding the efficacy and safety of robotic salvage radical prostatectomy can be drawn comprises fewer than 200 patients with limited follow-up. Preliminary results are promising and some outcomes have been favorable when compared with contemporary open salvage prostatectomy series. Advantages of the robotic platform in the performance of salvage radical prostatectomy include decreased blood loss, short length of stay and improved visualization. Greater experience is required to confirm the long-term oncologic efficacy and functional outcomes as well as the generalizability of results achieved at experienced centers. PMID:25378826

Kaffenberger, Samuel D; Smith, Joseph A

2014-10-01

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

ENZYMOLOGY: Coenzymes and Radicals  

Science.gov (United States)

Access to the article is free, however registration and sign-in are required. Organic radicals play an important role in many enzymatic reactions, but as Frey explains in his Perspective, information about their structure is hard to come by. He highlights the report by Chabrière et al., who have crystallized the enzyme pyruvate:ferredoxin oxidoreductase with the intermediate radical form of hydroxyethylidene-thiamine pyrophosphate bound to its active site. The structure of the radical provides important clues to its electronic structure.

Perry A. Frey (University of Wisconsin-Madison;Department of Biochemistry)

2001-12-21

337

Resonance Raman spectra of p-benzosemiquinone radical and hydroquinone radical cation  

International Nuclear Information System (INIS)

The time-resolved resonance Raman spectrum of the p-benzosemiquinone radical (HOC6H4O), excited at 415 nm and observed on the microsecond time scale in the pulse radiolysis of moderately acidic solutions of hydroquinone (pH 2-4), is reported. The nu/sub 7a/ CO stretching mode appears prominently in the spectrum at 1511 cm-1, showing that the CO bond is very similar to that in phenoxyl where this vibration is observed at 1505 cm-1. Strongly resonance enhanced bands are also observed at 1613 and 1162 cm-1 and are assigned respectively to the nu/sub 8a/ ring stretching and nu/sub 9a/ CH bending modes. The strong enhancement of these latter vibrations, which are very much weaker in the corresponding spectrum of the phenoxyl radical, and the similarity of the ring stretching frequency (nu/sub 8a/) to that in p-benzosemiquinone radical anion (1620 cm-1) indicate that there is a strong interaction of the OH p(?) electron pair with the phenoxyl radical's ?-electron system. The coefficient for the acid-catalyzed dehydroxylation of the OH adduct of hydroquinone is estimated from the pH and time dependences of the Raman signals of the semiquinone to be 5.4 x 108 M-1 s-1. In strongly acidic solutions (e.g., ? 2.3 M H2SO4) a second transient species, identified as the hydroquinone radical cation, is observed. The vibrational features of this radical are qualitatively similar to those for p-benzosemiquinone radical anion with the nu/sub 8a/ ring stretching mode very strongly resonance enhanced and observed at 1644 cm-1. The nu/sub 7a/ CO stretching mode is observed at 1426 cm-1 but is very much weaker than in the corresponding spectrum of the radical anion

338

Radical scavenging activity of antioxidants evaluated by means of electrogenerated HO radical.  

Science.gov (United States)

A method is proposed and tested concerning the characterization of antioxidants by means of their reaction with electrogenerated HO radicals in galvanostatic assays with simultaneous O2 evolution, using a Pt anode fairly oxidized. The consumption of a set of species with antioxidant activity, ascorbic acid (AA), caffeic acid (CA), gallic acid (GA) and trolox (T), is described by a first order kinetics. The rate of the processes is limited by the kinetics of reaction with HO radicals and by the kinetics of charge transfer. Information regarding the scavenger activity of antioxidants is obtained by the relative value of the rate constant of the reaction between antioxidants and HO radicals, k(AO,HO)/k(O2). The number of HO radicals scavenged per molecule of antioxidant is also estimated and ranged from 260 (ascorbic acid) to 500 (gallic acid). The method is applied successfully in the characterization of the scavenger activity of ascorbic acid in a green-tea based beverage. PMID:25127602

Oliveira, Raquel; Geraldo, Dulce; Bento, Fátima

2014-11-01

339

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

340

Composition of Essential Oil, Radical Scavenging and Antibacterial Properties of Interspecific Hybrid Thymus × oblongifolius Opiz  

Directory of Open Access Journals (Sweden)

Full Text Available Radical scavenging and antibacterial properties of thyme extracts isolated from the two different Thymus × oblongifolius Opiz samples (TO1 and TO2 were studied. The oil of the TO1 was constituted mainly of hydrocarbon terpenes (83.4%, while the oil of the TO2 was composed mainly of oxygenated compounds with a -terpenyl acetate (37.9% being the major one. The extracts isolated with hexane, acetone and ethanol from the whole and deodorized herb were tested for their radical scavenging capacity (RSC in the model reaction systems containing stable radical DPPH • and cation radical ABTS •+. The extracts isolated with ethanol from undeodorized herb possessed the strongest RSC, while hexane extracts were not active. Undeodorized acetone extracts of the TO1 possessed higher RSC than those of the TO2, while undeodorized ethanol extracts of the TO2 were stronger radical scavengers than similar extracts of the TO1. The antibacterial activity of the extracts tested by using seven food pathogenic species depended on the species, extract concentration and extract type. Bacillus cereus, Staphylococcus aureus and St. epidermidis were more sensitive to plant extracts than Micrococcus luteus, Esherichia coli, Salmonella typhimurium and Enterobacter aerogenes.

Kristina Lo žien?

2012-01-01

 
 
 
 
341

Radical anions of flavonoids.  

Science.gov (United States)

Several representatives of natural flavonoids and their synthetic nitro-derivatives have been investigated by polarography and electron paramagnetic resonance (EPR) spectroscopy under electrochemical reduction in acetonitrile, dimethylformamide (DMF), dimethylsulfoxide (DMSO) or 1,2-dimethoxyethane. All the compounds studied are reduced in the first stage by one-electron transfer, apart from flavanone, which accepts two electrons simultaneously. However, the primary radical anions were detected by EPR spectroscopy only for 4'-nitroflavone. It was shown that radical anions of other flavonoids quickly dimerized. The analysis of the temperature dependence of the hyperfine interaction constants and broadening of lines in EPR spectra of 4'-nitroflavone radical anions has shown that the distribution of spin density is due to both the change of polarity of the medium and rotation of the nitrophenyl moiety. The assignment of hyperfine structure constants for the 4'-nitroflavone radical anion was confirmed by density functional theory (DFT) calculations. Copyright © 2011 John Wiley & Sons, Ltd. PMID:21751247

Vakulskaya, Tamara I; Larina, Lyudmila I; Vashchenko, Alexander V

2011-08-01

342

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)

343

Effect of ascorbic acid on hydroxyl radical generation by chemical, enzymatic and cellular systems. Importance for antioxidant prevention of pulmonary emphysema.  

Science.gov (United States)

The ability of ascorbic acid (AA) (25 to 500 microM) to increase OH production by a chemical (Fe(2+)-EDTA-H2O2), an enzymatic (xanthine-xanthine oxidase-Fe(2+)-EDTA) and a cellular system (3.10(6) human polymorphonuclear leukocytes (PMNL) or murine peritoneal macrophages (PM) activated with 7.2 ng PMA/ml) was studied. At all concentrations used AA strongly enhanced OH generation by the chemical and the enzymatic systems. However, the maximal increase of about 14-fold was found for incomplete chemical system (10 microM Fe(2+)-20 microM EDTA) and 500 microM AA. In the case of phorbol-myristate-acetate-activated-PMNL and macrophages, the moderate increase in OH formation was only caused by low AA concentrations. At 50 microM AA, the OH formation was 112 +/- 3 and 117 +/- 4% of control, respectively. Higher AA concentrations had no influence or even decreased OH formation by phagocytes. It is suggested that administration of AA will not significantly enhance OH generation from pulmonary phagocytes and could be useful for prevention of the oxidant-mediated lung injury related to inflammation. PMID:1659390

Nowak, D; Piasecka, G; Antczak, A; Pietras, T

1991-01-01

344

Oxygen radicals stimulate guinea pig gallbladder glycoprotein secretion in vitro  

International Nuclear Information System (INIS)

In several animal models of cholelithiasis, and in humans with gallstones, hypersecretion of gallbladder mucin is observed. This study was undertaken to determine the effect of oxygen radicals on guinea pig gallbladder glycoprotein secretion in organ culture. Mucosal explants were incubated with [3H]glucosamine hydrochloride to label glycoproteins, then exposed to oxygen radicals generated by chelated ferric iron and ascorbic acid. Marked stimulation of glycoprotein release was observed after a 30-min exposure to the oxygen radical-generating system, and the effect was inhibited by mannitol. The stimulatory effect of hydroxyl radical was not accompanied by leakage of intracellular lactate dehydrogenase. Parallel experiments with human granulocytes activated with f-Met-Leu-Phe and coincubated with gallbladder explants revealed similar results. These results indicate that oxygen radicals, especially the hydroxyl radical (OH), are capable of stimulating rapid release of mucous-type glycoproteins from gallbladder epithelium

345

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

346

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

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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

347

Resveratrol products resulting by free radical attack  

Energy Technology Data Exchange (ETDEWEB)

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.

Bader, Yvonne; Quint, R.M. [Section Radiation Biology, Department of Nutritional Sciences, Faculty of Life Sciences, University of Vienna, UZAII, Althanstrasse 14, A-1090 Vienna (Austria); Getoff, Nikola [Section Radiation Biology, Department of Nutritional Sciences, Faculty of Life Sciences, University of Vienna, UZAII, Althanstrasse 14, A-1090 Vienna (Austria)], E-mail: nikola.getoff@univie.ac.at

2008-06-15

348

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

349

Resveratrol products resulting by free radical attack  

Science.gov (United States)

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.

Bader, Yvonne; Quint, R. M.; Getoff, Nikola

2008-06-01

350

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)

351

Nefrectomía radical laparoscópica / Radical laparoscopic nephroureterectomy  

Scientific Electronic Library Online (English)

Full Text Available SciELO Spain | Language: Spanish Abstract in spanish Al igual que la cirugía laparoscópica está cada vez más presente en la cirugía del adenocarcinoma renal, lo mismo está ocurriendo en cuanto al tratamiento radical del tumor de urotelio superior. En esta intervención laparoscópica es importante hacer hincapié en las distintas posibilidades para desin [...] sertar el uréter distal (mediante resección transuretral, mediante laparoscopia, o de forma abierta), así como tener en consideración que es el tumor con mayor riesgo de implante en los puertos de entrada. Hacemos en este trabajo una revisión de la bibliografía, así como una puesta al día de las distintas formas de abordar el uréter distal. Abstract in english As with the increasingly common presence of laparoscopic surgery in renal adenocarcinoma, the same situation is also occurring with radical management of tumours of the upper urothelium. In this type of clinical condition, it is important to emphasize the different ways to mobilise the distal ureter [...] (with transuretral resection or unroofing, pure laparoscopy, or open), and to take into account that this tumour has the highest risk of implantation at the ports of entry. Here, we conduct a literature review and up-date of the different approaches to the distal urethra.

L.A., Fariña Pérez.

352

Laparoscopic radical cholecystectomy.  

Science.gov (United States)

Controversy exists as to the role of minimally invasive techniques in the management of early gallbladder cancer. The majority of early gallbladder cancers are diagnosed upon final pathology after laparoscopic cholecystectomy. For stage pT1a tumors, no further surgery is warranted; however, for pT1b or greater lesions, patients usually undergo port-site excisions and completion of open radical cholecystectomy involving a partial hepatectomy of segments IV and V and a lymphadenectomy of the hepatoduodenal ligament. Presented in this paper is a totally laparoscopic radical cholecystectomy performed for suspected early gallbladder cancer. Despite the fact that a preoperative serum IgG4 level was within normal limits, final pathology was consistent with autoimmune cholecystitis. As a result, the laparoscopic radical cholecystectomy may be useful in select patients with a preoperative suspicion of early-stage gallbladder cancer by sparing them the necessity of a second-stage open procedure. PMID:19215212

Gumbs, Andrew A; Milone, Luca; Geha, Rula; Delacroix, Johanna; Chabot, John A

2009-08-01

353

A 'Radical' Approach to Reading Development in Chinese: The Role of Semantic Radicals and Phonetic Radicals  

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Two studies investigating the significance of radical knowledge in Chinese reading development are reported in this paper. Study 1 examined the semantic radical knowledge of 20 Grade 1, 20 Grade 3, and 20 Grade 5 Chinese children in Hong Kong. It was found that various types of semantic radical knowledge, including the position and semantic category of semantic radicals, correlated significantly with Chinese word reading and sentence comprehension. Study 2 examined phonetic radical knowledge ...

Ho, Csh; Ng, Tt; Ng, Wk

2003-01-01

354

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

355

The oxidation of trimethylamine by OH radicals in aqueous solution, as studied by pulse radiolysis, ESR, and product analysis  

International Nuclear Information System (INIS)

Hydroxyl radical reactions with trimethylamine in aqueous solution lead to the formation of the aminoalkyl radical (CH3)2NCH2 (A) and its conjugated acid (CH3)2HNCH2 (AH+) as well as to the alkylamine radical cation (CH3)3N+ (N+). These radicals are transformed into each other by hydrolytic reactions. Radicals AH+ are more acidic (pKa ? 3.6) than the radicals N+ (pKa ? 8.0). Consequently, N+ predominate over AH+ under quasi equilibrium conditions (e.g. in the presence of phosphate buffer) and are the only species observed by ESR in acid solutions. Reacting with the protonated amine, OH radicals abstract hydrogen at nitrogen and at carbon with comparable ease. Reaction of OH radicals with the free amine may initially also generate N+, beside H-abstraction at carbon. Radicals A absorb more strongly at 260 nm (?=3390 dm3 mol-1 cm-1) than the radical cation N+ (?=950 dm3 mol-1 cm-1). Radical A has reducing properties whereas radicals AH+ and N+ have oxidizing properties and hence can be monitored with p-nitroacetophenone (the reducing radicals), and Fe(CN)64-, N,N'-tetramethyl-p-phenylenediamine and 2,2'-azinobis-(3-ethyl-benzthiazoline-6-sulphonate) (the oxidizing radicals). These radicals mainly (?85%) disproportionate, one of the products being formaldehyde. (orig./HK)

356

OH radicals in the troposphere  

International Nuclear Information System (INIS)

OH radicals are radicals which determine the photochemistry of the troposphere. The reactivity of OH radicals to organic substances is one of the fundamental criteria for the evaluation of abiotic decomposition. Details are given about the photochemical formation and reaction of OH radicals, the decomposition reactions of organic compounds in the gaseous phase, the determination of the specific rates of OH radical decomposition reactions, measuring methods for the determination of OH radical concentrations in the troposphere, selected results, OH concentration distributions obtained from model calculations, and the influence of trace gases on OH concentrations. A summary, conclusions, and research proposals are attached. (orig./BBR)

357

The perchlorotriphenylmethyl (PTM) radical.  

Science.gov (United States)

In spite of the considerable understanding and development of perchlorotriphenylmethyl (PTM) radical derivatives, the preparation of crystals of the pure unsubstituted PTM radical, C19Cl15, suitable for single-crystal X-ray diffraction has remained a challenge since its discovery, and only two studies dealing with the crystal structure of the unsubstituted PTM radical have been published. In one study, the radical forms clathrates with aromatic solvents [Veciana, Carilla, Miravitlles & Molins (1987). J. Chem. Soc. Chem. Commun. pp. 812-814], and in the other the structure was determined ab initio from powder X-ray diffraction data [Rius, Miravitlles, Molins, Crespo & Veciana (1990). Mol. Cryst. Liq. Cryst. 187, 155-163]. We report here the preparation of PTM crystals for single-crystal X-ray diffraction and their resolution. The structure, which shows monoclinic symmetry (C2/c), revealed a nonsymmetric molecular propeller conformation (D3 symmetry) caused by the steric strain between the ortho-Cl atoms, which protect the central C atom (sp(2)-hybridization and major spin density) and give high chemical and thermal persistence to the PTM. The supramolecular structure of PTM shows short Cl...Cl intermolecular interactions and can be described in terms of layers formed by rows of molecules positioned in a head-to-tail manner along the c axis. PMID:23459350

Guasch, Judith; Fontrodona, Xavier; Ratera, Imma; Rovira, Concepció; Veciana, Jaume

2013-03-01

358

Enzyme Initiated Radical Polymerizations  

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Full Text Available Biocatalysis is propagating into practically every area of organic chemistry, amongst them radical polymerizations. A review of the recent developments of this dynamic and quickly evolving area of research is presented together with a critical evaluation of its potential to yield novel polymers and/or environmentally more benign synthetic procedures.

Frank Hollmann

2012-03-01

359

Radical School Reform.  

Science.gov (United States)

This book provides a comprehensive examination of the nature of the school crisis and the ways in which radical thinkers and educators are dealing with it. Excerpts from the writings of Jonathan Kozol, John Holt, Kenneth Clark, and others are concerned with the realities of education in ghettos and suburbs. Paul Goodman, Marshall McLuhan, Sylvia…

Gross, Beatrice, Ed.; Gross, Ronald, Ed.

360

Beyond Radical Educational Cynicism.  

Science.gov (United States)

An alternative is presented to counter current radical arguments that the schools cannot bring about social change because they are instruments of capitalism. The works of Samuel Bowles, Herbert Gintis, and Louis Althusser are discussed. Henry Giroux's "Ideology, Culture and the Process of Schooling" provides an alternative to cynicism. (PP)

Wood, George H.

1982-01-01

 
 
 
 
361

Toward living radical polymerization.  

Science.gov (United States)

Radical polymerization is one of the most widely used processes for the commercial production of high-molecular-weight polymers. The main factors responsible for the preeminent position of radical polymerization are the ability to polymerize a wide array of monomers, tolerance of unprotected functionality in monomer and solvent, and compatibility with a variety of reaction conditions. Radical polymerization is simple to implement and inexpensive in relation to competitive technologies. However, conventional radical polymerization severely limits the degree of control that researchers can assert over molecular-weight distribution, copolymer composition, and macromolecular architecture. This Account focuses on nitroxide-mediated polymerization (NMP) and polymerization with reversible addition-fragmentation chain transfer (RAFT), two of the more successful approaches for controlling radical polymerization. These processes illustrate two distinct mechanisms for conferring living characteristics on radical polymerization: reversible deactivation (in NMP) and reversible or degenerate chain transfer (in RAFT). We devised NMP in the early 1980s and have exploited this method extensively for the synthesis of styrenic and acrylic polymers. The technique has undergone significant evolution since that time. New nitroxides have led to faster polymerization rates at lower temperatures. However, NMP is only applicable to a restricted range of monomers. RAFT was also developed at CSIRO and has proven both more robust and more versatile. It is applicable to the majority of monomers subject to radical polymerization, but the success of the polymerization depends upon the selection of the RAFT agent for the monomers and reaction conditions. We and other groups have proposed guidelines for selection, and the polymerization of