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

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

CAROLA HENRIQUEZ; CAROLINA ALIAGA; EDUARDO LISSI

2004-01-01

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

Scientific Electronic Library Online (English)

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

HENRIQUEZ, CAROLA; ALIAGA, CAROLINA; LISSI, EDUARDO

2004-03-01

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

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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 ...

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

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

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 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 with peroxyl radicals. Diclofenac bleached ABTS radical cation in a concentration-dependent way. In ORAC assays, diclofenac inhibited the consumption of fluorescein and c-phycoc (more) yanin 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.

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

2009-01-01

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

Directory of Open Access Journals (Sweden)

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

2007-01-01

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Screening of free radical scavengers from Erigeron breviscapus using on-line HPLC-ABTS/DPPH based assay and mass spectrometer detection.  

UK PubMed Central (United Kingdom)

Erigeron breviscapus is a well-known traditional Chinese herbal medicine. In this study, on-line HPLC-ABTS/DPPH assay coupled with MS detection were applied to screen and identify the free radical scavengers in 70% methanol extracts of E. breviscapus. Using on-line HPLC-ABTS-MS and HPLC-DPPH-MS assay, 13 radical scavengers (including 4-O-caffeoylquinic acid (4-CQA) (1), 9-caffeoyl-2,7-anhydro-2-octulosonic acid (9-COA) (2), 3-caffeoyl-2,7-anhydro-3-deoxy-2-octulopyranosonic acid (3-CDOA) (3), erigeside I (4), quercetin-3-O-glucuronide (5), eriodictyol-7-O-glucuronide (6), scutellarin (7), 1,4-di-O-caffeoylquinic acid (1,4-di-CQA) (8), 3,5-di-CQA (9), 1-malonyl-3,5-di-CQA (10), erigoster B (11), 4,5-di-CQA (12) and 4,9-di-CDOA (13)) and 9 radical scavengers (including 1, 4, 7, 8, 9, 10, 11, 12 and 13) were discovered, respectively. Furthermore, the anti-oxidative activities of 4 compounds, including 7, 9, 11 and 12 were evaluated. Reverse anti-oxidative activity order of scutellarin and 3,5-di-CQA was observed in on-line HPLC-ABTS assay and on-line HPLC-DPPH assay. To validate their anti-oxidative activities, the off-line ABTS and DPPH assays were performed. Given sufficient reaction time, 3,5-di-CQA showed higher activity than scutellarin, which was consistent with the order obtained in on-line HPLC-ABTS assay. These results revealed that on-line HPLC-ABTS assay is a more sensitive method for screening and determining free radical scavengers, especially more suitable for those compounds with slower reaction kinetics.

Li F; Zhang LD; Li BC; Yang J; Yu H; Wan JB; Wang YT; Li P

2012-03-01

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EVALUATION OF THE EXTINCTION COEFFICIENT OF THE ABTS DERIVED RADICAL CATION  

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish Conocer el valor exacto del coeficiente de extinción del radical catión derivado del ABTS es un pre-requisito para su empleo en la evaluación de la capacidad antioxidante de compuestos puros polifuncionales o mezclas complejas. Nosotros hemos realizado emperimentos que permiten establecer límites inferiores y superiores para su valor. Los límites obtenidos \t\t\t1.0 x 10(4) M-1 cm-1 (more) dos en la literatura. Sin embargo, el uso de estos valores conduced a coeficientes estequiométricos anormalmente altos para sus reacciones con comuestos simples como monofenoles y triptofano. Abstract in english The exact knowledge of the value of the extinction coefficient of the ABTS derived radical is necessary for its quantitative use in the evaluation of the antioxidant capacity of pure compounds and/or complex mixtures. We have performed experiments in order to stablish its lower and upper limits of its value. The limits obtained, \t\t\t\t1.0 x 10(4) M-1 cm-1 (more) of these values leads to large stoichiometric coefficients for the reaction of these radicals with simple substrates, such as monophenols or tryptophan.

Henriquez, Carola; Lissi, Eduardo

2002-12-01

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EVALUATION OF THE EXTINCTION COEFFICIENT OF THE ABTS DERIVED RADICAL CATION  

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

Carola Henriquez; Eduardo Lissi

2002-01-01

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Optimization of ABTS radical cation assay specifically for determination of antioxidant capacity of intracellular extracts of microalgae and cyanobacteria.  

UK PubMed Central (United Kingdom)

A renewed interest in antioxidants has arisen in recent years; microalgae and cyanobacteria are potential sources thereof for use as food/feed ingredients. However, improved methods for comprehensive screening of antioxidant capacity specifically in intracellular extracts of marine microorganisms are required - encompassing lipophilic and hydrophilic compounds simultaneously. The original ABTS method was thus improved, and in particular the procedures of cell disruption and storage were optimized. The best solvent found was ethanol/water (1:1, v/v). The reaction to form ABTS(+) in said solvent was essentially complete by eight hours, and this radical cation was stable for at least 6 days; at room temperature, the ABTS(+) solution remained within an allowable analytical range for up to 13 h. Ultra Turrax was the best cell disruption method, and refrigeration was the best preservation method. This improved methodology was validated with four representative strains that respond poorly to cell disruption.

Guedes AC; Amaro HM; Gião MS; Malcata FX

2013-05-01

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

UK PubMed Central (United Kingdom)

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

Branchi B; Galli C; Gentili P

2005-07-01

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

Science.gov (United States)

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

Branchi, Barbara; Galli, Carlo; Gentili, Patrizia

2005-06-10

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

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

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

2005-01-01

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Thrombospondin-1 peptide ABT-510 combined with valproic acid is an effective antiangiogenesis strategy in neuroblastoma.  

Science.gov (United States)

In the pediatric cancer neuroblastoma, clinically aggressive disease is associated with increased levels of angiogenesis stimulators and high vascular index. We and others have hypothesized that blocking angiogenesis may be effective treatment for this pediatric malignancy. However, little is known about the efficacy of antiangiogenic agents in pediatric malignancies. Recently, promising results have been reported in an adult phase I study of ABT-510, a peptide derivative of the natural angiogenic inhibitor thrombospondin-1. Histone deacetylase inhibitors, such as valproic acid (VPA), have also been shown to have antiangiogenic activity in several cancer models. In this study, we evaluated the effects of ABT-510 and VPA on neuroblastoma tumor growth and angiogenesis. Although only VPA was capable of blocking the proliferation of neuroblastoma cells and inducing neuroblastoma cell apoptosis in vitro, treatment with VPA or ABT-510 alone significantly suppressed the growth of neuroblastoma xenografts established from two different MYCN-amplified cell lines. Combination therapy more effectively inhibited the growth of small neuroblastoma xenografts than single-agent treatment, and in animals with large xenografts, total cessation of tumor growth was achieved with this treatment approach. The microvascular density was significantly reduced in the xenografts treated with combination therapy compared with controls or tumors treated with single agents. In addition, the number of structurally abnormal vessels was reduced, suggesting that these agents may "normalize" the tumor vasculature. Our results indicate that ABT-510 combined with VPA may be an effective antiangiogenic treatment strategy for children with high-risk neuroblastoma. PMID:17308113

Yang, Qiwei; Tian, Yufeng; Liu, Shuqing; Zeine, Rana; Chlenski, Alexandre; Salwen, Helen R; Henkin, Jack; Cohn, Susan L

2007-02-15

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Thrombospondin-1 peptide ABT-510 combined with valproic acid is an effective antiangiogenesis strategy in neuroblastoma.  

UK PubMed Central (United Kingdom)

In the pediatric cancer neuroblastoma, clinically aggressive disease is associated with increased levels of angiogenesis stimulators and high vascular index. We and others have hypothesized that blocking angiogenesis may be effective treatment for this pediatric malignancy. However, little is known about the efficacy of antiangiogenic agents in pediatric malignancies. Recently, promising results have been reported in an adult phase I study of ABT-510, a peptide derivative of the natural angiogenic inhibitor thrombospondin-1. Histone deacetylase inhibitors, such as valproic acid (VPA), have also been shown to have antiangiogenic activity in several cancer models. In this study, we evaluated the effects of ABT-510 and VPA on neuroblastoma tumor growth and angiogenesis. Although only VPA was capable of blocking the proliferation of neuroblastoma cells and inducing neuroblastoma cell apoptosis in vitro, treatment with VPA or ABT-510 alone significantly suppressed the growth of neuroblastoma xenografts established from two different MYCN-amplified cell lines. Combination therapy more effectively inhibited the growth of small neuroblastoma xenografts than single-agent treatment, and in animals with large xenografts, total cessation of tumor growth was achieved with this treatment approach. The microvascular density was significantly reduced in the xenografts treated with combination therapy compared with controls or tumors treated with single agents. In addition, the number of structurally abnormal vessels was reduced, suggesting that these agents may "normalize" the tumor vasculature. Our results indicate that ABT-510 combined with VPA may be an effective antiangiogenic treatment strategy for children with high-risk neuroblastoma.

Yang Q; Tian Y; Liu S; Zeine R; Chlenski A; Salwen HR; Henkin J; Cohn SL

2007-02-01

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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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Free radical yields from the homolysis of peroxynitrous acid.  

Science.gov (United States)

A recent study reports discordant results for maximal free-radical yields from the decomposition of peroxynitrous acid using different assay reagents and a puzzling decrease (to zero) of the radical yields with increasing pH. An assay method using 2,2,'azino-bis(3-ethyl-benzthiazoline sulphonate) (ABTS) has been tested using stopped-flow kinetic studies, and the results imply that the assay is satisfactory when [HOONO] much greater than [-OONO] but that reactions involving peroxynitrite anion interfere at higher pH. Evidence is presented that peroxynitrite was an interfering species in the earlier studies. PMID:1315711

Yang, G; Candy, T E; Boaro, M; Wilkin, H E; Jones, P; Nazhat, N B; Saadalla-Nazhat, R A; Blake, D R

1992-01-01

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Free radical yields from the homolysis of peroxynitrous acid.  

UK PubMed Central (United Kingdom)

A recent study reports discordant results for maximal free-radical yields from the decomposition of peroxynitrous acid using different assay reagents and a puzzling decrease (to zero) of the radical yields with increasing pH. An assay method using 2,2,'azino-bis(3-ethyl-benzthiazoline sulphonate) (ABTS) has been tested using stopped-flow kinetic studies, and the results imply that the assay is satisfactory when [HOONO] much greater than [-OONO] but that reactions involving peroxynitrite anion interfere at higher pH. Evidence is presented that peroxynitrite was an interfering species in the earlier studies.

Yang G; Candy TE; Boaro M; Wilkin HE; Jones P; Nazhat NB; Saadalla-Nazhat RA; Blake DR

1992-01-01

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Effects of molecular structure on kinetics and dynamics of the trolox equivalent antioxidant capacity assay with ABTS(+•).  

UK PubMed Central (United Kingdom)

Reaction kinetics in the Trolox equivalent antioxidant capacity (TEAC) assay between ABTS(+•) [2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) cation radical] and compounds with different structure, molecular weight, number of OH groups, and redox potential were investigated by recording loss of ABTS(+•) absorbance (734 nm) continuously over time. Curves showed six distinguishable kinetic patterns, including both immediate and extended reaction components. Radical quenching rates in the immediate component most relevant to reactions in foods and tissues depended on phenol structure and steric accessibility to the hindered radical, while reaction stoichiometry correlated with the number of phenol groups (>0.81) but not redox potential. Current assay procedures measure antioxidant capacity under conditions not relevant to actual applications and do not determine radical quenching rates. Results raise serious questions regarding the ability of reactions with the hindered ABTS(+•) to rank actual radical quenching by compounds with different structures and invalidate reporting antioxidant activity as Trolox equivalents.

Tian X; Schaich KM

2013-06-01

20

Differential effects of ABT-510 and a CD36-binding peptide derived from the type 1 repeats of thrombospondin-1 on fatty acid uptake, nitric oxide signaling, and caspase activation in vascular cells.  

Science.gov (United States)

ABT-510 is a potent mimetic of an anti-angiogenic sequence from the second type 1 repeat of thrombospondin-1. ABT-510 and the original d-Ile mimetic from which it was derived, GDGV(dI)TRIR, are similarly active for inhibiting vascular outgrowth in a B16 melanoma explant assay. Because GDGV(dI)TRIR and thrombospondin-1 modulate nitric oxide signaling by inhibiting the fatty translocase activity of CD36, we examined the ability ABT-510 to modulate fatty acid uptake into vascular cells and downstream nitric oxide/cGMP signaling. Remarkably, ABT-510 is less active than GDGV(dI)TRIR for inhibiting myristic acid uptake into both endothelial and vascular smooth muscle cells. Correspondingly, ABT-510 is less potent than GDGV(dI)TRIR for blocking a myristate-stimulated increase in cell adhesion to collagen and nitric oxide-driven accumulation of cGMP. ABT-510 at concentrations sufficient to inhibit CD36 fatty acid translocase activity synergizes with thrombin in aggregating platelets and blunts the activity of NO to delay aggregation, but again less than GDGV(dI)TRIR. In contrast, ABT-510 is more potent than GDGV(dI)TRIR for inducing caspase activation in vascular cells. Thus, we propose that ABT-510 is a drug with at least two mechanisms of action, and its potent anti-tumor activity may be in part independent of CD36 fatty acid translocase inhibition. PMID:18068687

Isenberg, Jeff S; Yu, Christine; Roberts, David D

2007-11-01

 
 
 
 
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Differential effects of ABT-510 and a CD36-binding peptide derived from the type 1 repeats of thrombospondin-1 on fatty acid uptake, nitric oxide signaling, and caspase activation in vascular cells.  

UK PubMed Central (United Kingdom)

ABT-510 is a potent mimetic of an anti-angiogenic sequence from the second type 1 repeat of thrombospondin-1. ABT-510 and the original d-Ile mimetic from which it was derived, GDGV(dI)TRIR, are similarly active for inhibiting vascular outgrowth in a B16 melanoma explant assay. Because GDGV(dI)TRIR and thrombospondin-1 modulate nitric oxide signaling by inhibiting the fatty translocase activity of CD36, we examined the ability ABT-510 to modulate fatty acid uptake into vascular cells and downstream nitric oxide/cGMP signaling. Remarkably, ABT-510 is less active than GDGV(dI)TRIR for inhibiting myristic acid uptake into both endothelial and vascular smooth muscle cells. Correspondingly, ABT-510 is less potent than GDGV(dI)TRIR for blocking a myristate-stimulated increase in cell adhesion to collagen and nitric oxide-driven accumulation of cGMP. ABT-510 at concentrations sufficient to inhibit CD36 fatty acid translocase activity synergizes with thrombin in aggregating platelets and blunts the activity of NO to delay aggregation, but again less than GDGV(dI)TRIR. In contrast, ABT-510 is more potent than GDGV(dI)TRIR for inducing caspase activation in vascular cells. Thus, we propose that ABT-510 is a drug with at least two mechanisms of action, and its potent anti-tumor activity may be in part independent of CD36 fatty acid translocase inhibition.

Isenberg JS; Yu C; Roberts DD

2008-02-01

22

Characterization of the radical-scavenging reaction of 2-O-substituted ascorbic acid derivatives, AA-2G, AA-2P, and AA-2S: a kinetic and stoichiometric study.  

UK PubMed Central (United Kingdom)

The aim of this study was to characterize the antioxidant activity of three ascorbic acid (AA) derivatives O-substituted at the C-2 position of AA: ascorbic acid 2-glucoside (AA-2G), ascorbic acid 2-phosphate (AA-2P), and ascorbic acid 2-sulfate (AA-2S). The radical-scavenging activities of these AA derivatives and some common low molecular-weight antioxidants such as uric acid or glutathione against 1,1-diphenyl-picrylhydrazyl (DPPH) radical, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS+), or galvinoxyl radical were kinetically and stoichiometrically evaluated under pH-controlled conditions. Those AA derivatives slowly and continuously reacted with DPPH radical and ABTS+, but not with galvinoxyl radical. They effectively reacted with DPPH radical under acidic conditions and with ABTS+ under neutral conditions. In contrast, AA immediately quenched all species of radicals tested at all pH values investigated. The reactivity of Trolox, a water-soluble vitamin E analogue, was comparable to that of AA in terms of kinetics and stoichiometrics. Uric acid and glutathione exhibited long-lasting radical-scavenging activity against these radicals under certain pH conditions. The radical-scavenging profiles of AA derivatives were closer to those of uric acid and glutathione rather than to that of AA. The number of radicals scavenged by one molecule of AA derivatives, uric acid, or glutathione was equal to or greater than that by AA or Trolox under the appropriate conditions. These data suggest the potential usage of AA derivatives as radical scavengers.

Takebayashi J; Tai A; Gohda E; Yamamoto I

2006-04-01

23

Influence of different amino acid groups on the free radical scavenging capability of multi walled carbon nanotubes.  

Science.gov (United States)

Multi-walled carbon nanotubes (MWCNTs) were functionalized with a series of amino acids (lysine, arginine, cysteine, histidine, and aspartic acid) by sonication. Surface functional groups of the treated MWCNTs were investigated by infrared spectroscopy, Raman spectroscopy and thermogravimetric analysis. The results indicated the formation of various amino acid functionalities on the MWCNT surface, as well as the improved dispersion of MWCNTs in water. After functionalization, the antioxidant activity of all treated samples was analyzed using 2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH), and hydroxyl radical scavenging, metal ion chelating, and reducing power assays. The antioxidant activity of the functionalized MWCNTs was 2-2.5 times greater than that of reduced glutathione (GSH) in ABTS radical scavenging, 1.5-5 times greater than that of GSH in reducing power, 1.3-1.8 times greater than that of butylated hydroxyanisole (BHA) in DPPH scavenging, and 3-10 times greater than that of GSH in hydroxyl radical scavenging. Accordingly, the amino acid-functionalized MWCNTs were appeared to be more potent than BHA and GSH synthetic antioxidants, and can thus be considered as excellent antioxidants to scavenge free radicals. PMID:23281168

Amiri, Ahmad; Memarpoor-Yazdi, Mina; Shanbedi, Mehdi; Eshghi, Hossein

2012-12-28

24

Influence of different amino acid groups on the free radical scavenging capability of multi walled carbon nanotubes.  

UK PubMed Central (United Kingdom)

Multi-walled carbon nanotubes (MWCNTs) were functionalized with a series of amino acids (lysine, arginine, cysteine, histidine, and aspartic acid) by sonication. Surface functional groups of the treated MWCNTs were investigated by infrared spectroscopy, Raman spectroscopy and thermogravimetric analysis. The results indicated the formation of various amino acid functionalities on the MWCNT surface, as well as the improved dispersion of MWCNTs in water. After functionalization, the antioxidant activity of all treated samples was analyzed using 2,2-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH), and hydroxyl radical scavenging, metal ion chelating, and reducing power assays. The antioxidant activity of the functionalized MWCNTs was 2-2.5 times greater than that of reduced glutathione (GSH) in ABTS radical scavenging, 1.5-5 times greater than that of GSH in reducing power, 1.3-1.8 times greater than that of butylated hydroxyanisole (BHA) in DPPH scavenging, and 3-10 times greater than that of GSH in hydroxyl radical scavenging. Accordingly, the amino acid-functionalized MWCNTs were appeared to be more potent than BHA and GSH synthetic antioxidants, and can thus be considered as excellent antioxidants to scavenge free radicals.

Amiri A; Memarpoor-Yazdi M; Shanbedi M; Eshghi H

2013-08-01

25

Antioxidant activity of selected phenols estimated by ABTS and FRAP methods.  

UK PubMed Central (United Kingdom)

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

Biskup I; Golonka I; Gamian A; Sroka Z

2013-01-01

26

Technology evaluation: ABT-510, Abbott.  

Science.gov (United States)

ABT-510 is a small peptide thrombospondin-1 mimetic angiogenesis inhibitor under development by Abbott Laboratories for the potential treatment of solid tumors. ABT-510 is undergoing phase II clinical trials. PMID:15468604

Westphal, Johan R

2004-08-01

27

Technology evaluation: ABT-510, Abbott.  

UK PubMed Central (United Kingdom)

ABT-510 is a small peptide thrombospondin-1 mimetic angiogenesis inhibitor under development by Abbott Laboratories for the potential treatment of solid tumors. ABT-510 is undergoing phase II clinical trials.

Westphal JR

2004-08-01

28

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

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An autographic assay suitable for the detection of antioxidant compounds in a complex matrix (liquid and semi-solid pharmaceutical formulations) or in isolated compounds was described. The pre-formed radical monocation of 2,2?-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS•+) was generated ...

Zampini, Iris Catiana; Ordoñez, Roxana Mabel; Isla, María Inés

29

How do erythrocytes contribute to the ABTS* scavenging capacity of blood?  

UK PubMed Central (United Kingdom)

It has been suggested lately that erythrocytes contribute significantly to the oxidant scavenging capacity (OSC) of blood and that surface adsorption of polyphenols enhances the antioxidant capacity of erythrocytes. The aim of this study was to examine the contribution of erythrocytes to the OSC of whole blood measured with a substrate not penetrating into the cells. Comparison of reduction of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical (ABTS*) by whole blood and blood plasma indicates that erythrocytes do contribute to ABTS* reduction but their contribution is lower with respect to plasma. ABTS* reduction by erythrocytes and its enhancement by polyphenols were inhibited by thiol reagents (N-ethylmaleimide and iodacetate). These reagents inhibited also the reduction of extracellular ferricyanide by erythrocytes and its enhancement by polyphenols. On this basis we postulate that the contribution of erythrocytes to the blood OSC estimated by ABTS* decolorization is at least partly due to the transmembrane-reducing system, which activity is routinely assayed by ferricyanide reduction.

Sadowska-Woda I; Bartosz G

2013-01-01

30

Antioxidant activity of Hypericum androsaemum infusion: scavenging activity against superoxide radical, hydroxyl radical and hypochlorous acid.  

Science.gov (United States)

Hypericum androsaemum is a medicinal plant species containing many polyphenolic compounds, namely flavonoids and phenolic acids. Since polyphenolic compounds have high antioxidant potential, the ability of H. androsaemum infusion to act as a scavenger of reactive oxygen species (superoxide radical, hydroxyl radical and hypochlorous acid) was investigated. Superoxide radical was generated by the xanthine/xanthine oxidase and phenazine methosulphate/NADH systems. The infusion-mediated prevention of nitroblue tetrazolium reduction by the superoxide radical was used as the measured endpoint. Hydroxyl radical was generated by the Fe3+-EDTA/ascorbate Fenton system, and assayed by evaluating deoxyribose degradation using the thiobarbituric acid method. Hypochlorous acid scavenging activity was tested by measuring the inhibition of hypochlorous acid-induced 5-thio-2-nitrobenzoic acid oxidation to 5,5'-dithiobis(2-nitrobenzoic acid). The tested infusion mainly exhibited a potent scavenging effect on superoxide radicals (although a noncompetitive inhibitory effect on xanthine oxidase was also observed). The infusion also acted as a moderate scavenger of hydroxyl radicals and hypochlorous acid. A phytochemical study of the infusion was also undertaken, and nine phenolic compounds were identified. PMID:12392087

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

2002-10-01

31

Antioxidant activity of Hypericum androsaemum infusion: scavenging activity against superoxide radical, hydroxyl radical and hypochlorous acid.  

UK PubMed Central (United Kingdom)

Hypericum androsaemum is a medicinal plant species containing many polyphenolic compounds, namely flavonoids and phenolic acids. Since polyphenolic compounds have high antioxidant potential, the ability of H. androsaemum infusion to act as a scavenger of reactive oxygen species (superoxide radical, hydroxyl radical and hypochlorous acid) was investigated. Superoxide radical was generated by the xanthine/xanthine oxidase and phenazine methosulphate/NADH systems. The infusion-mediated prevention of nitroblue tetrazolium reduction by the superoxide radical was used as the measured endpoint. Hydroxyl radical was generated by the Fe3+-EDTA/ascorbate Fenton system, and assayed by evaluating deoxyribose degradation using the thiobarbituric acid method. Hypochlorous acid scavenging activity was tested by measuring the inhibition of hypochlorous acid-induced 5-thio-2-nitrobenzoic acid oxidation to 5,5'-dithiobis(2-nitrobenzoic acid). The tested infusion mainly exhibited a potent scavenging effect on superoxide radicals (although a noncompetitive inhibitory effect on xanthine oxidase was also observed). The infusion also acted as a moderate scavenger of hydroxyl radicals and hypochlorous acid. A phytochemical study of the infusion was also undertaken, and nine phenolic compounds were identified.

Valentão P; Fernandes E; Carvalho F; Andrade PB; Seabra RM; de Lourdes Bastos M

2002-10-01

32

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

Directory of Open Access Journals (Sweden)

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

R. S. PAL; R. ARUN KUMAR; CHANDRASHEKARA C.; N. K. HEDAU; P. K. AGARWAL; J. C. BHATT

2013-01-01

33

Dichloro-4-quinolinol-3-carboxylic acid: synthesis and antioxidant abilities to scavenge radicals and to protect methyl linoleate and DNA.  

UK PubMed Central (United Kingdom)

5,7-, 5,8-, 6,8-, 7,8-dichloro-4-quinolinol-3-carboxylic acid (5,7-, 5,8-, 6,8-, 7,8-DCQA) together with 7-chloro-4-quinolinol-3-carboxylic acid (7-CQA) and 4-quinolinol-3-carboxylic acid (QA) were synthesized to investigate the antioxidant properties. 5,7-DCQA exhibited the highest ability to scavenge 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS+.), 2,2'-diphenyl-1-picrylhydrazyl (DPPH) and galvinoxyl radicals. 6,8-DCQA possessed the highest efficacy to protect methyl linoleate against 2,2'-azobis(2-amidinopropane)dihydrochloride (AAPH)-induced oxidation. 5,7-, 5,8-DCQA and QA were able to retard the beta-carotene-bleaching in beta-carotene-linoleic acid emulsion. In addition, 5,8- and 6,8-DCQA efficiently protected DNA against hydroxyl radical (.OH)-mediated oxidation, and 5,8-DCQA and 7-CQA were active to protect DNA against AAPH-induced oxidation. Furthermore, only 7-CQA can protect DNA against Cu2+/glutathione (GSH)-mediated oxidation. Dichloro-4-quinolinol-3-carboxylic acids were potent to be antiradical drugs, and were worthy to be researched pharmacologically.

Li GX; Liu ZQ; Luo XY

2010-05-01

34

Study of radical processes in amino acids and peptides containing thioether group induced by hydroxyl radicals  

International Nuclear Information System (INIS)

Results of investigations of the OH-induced oxidation of amino acids and peptides containing thioether group are presented. Experiments have been carried out over pH range (0-10.5), employing pulse radiolysis and steady-state ?-radiolysis together with a gas-chromatography (GC), a high-performance ionic chromatography (HPICE), and electron spin resonance (ESR) techniques. A general OH-induced oxidation mechanism of these compounds has been proposed, with a hydroxysulfuranyl radical as a primary product formed by an addition of a hydroxyl radical to the thioether group. Secondary reactions of hydroxysulfuranyl radical are dependent on the geometry of the amino acid/peptide molecule, the number of functionalities and on the concentration of the amino acid/peptide and protons in the solutions. Transient products have been identified spectroscopically together with kinetic parameters of some radical reactions. Carbon dioxide acetaldehyde have been also identified as a final products. (author)

1996-01-01

35

Radical processes in radiolysis of monocarboxylic acids in liquid phase  

International Nuclear Information System (INIS)

A possibility of investigating short-lived radicals arising at radiolysis of liquid monocarbon acids, particularly, acetic and propionic acids by means of spin traps (c-phenyl-ter.butylnitron, ter.-butylmethylenenitron, ter.-nitroisobuthane, 2, 4, 6-tri-ter.-butyl-nitrosobenzene) is disclosed. Solutions of spin traps have been vacuumized and ?-irradiated with 60Co at 20 deg or - 196 deg, then they have been frozen. EPR spectra have been taken at temperatures from - 24 to 10 deg. Alkyl and acyl radicals are the basic radical products of radiolysis of acetic and propionic acids while CH2COOH and CH3CHCOOH are, probably, formed as secondary products. Additions of effective electron acceptor-benzophenone decrease yield of adducts with acyl radicals in the propionic acid and they do not affect yield of adducts with C2H5.

1983-01-01

36

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

International Nuclear Information System (INIS)

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

1977-05-25

37

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)

[en] 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.)

1985-01-01

38

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  

Energy Technology Data Exchange (ETDEWEB)

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).

Cabelli, D.E.; Bielski, B.H.J.

1985-12-01

39

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 104–105 molecules per cubic centimeter. Here, we present direct measurements of significant amounts of OH radicals of up to 1.8?106 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.

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

2013-01-01

40

Unexpectedly high indoor hydroxyl radical concentrations associated with nitrous acid.  

UK PubMed Central (United Kingdom)

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.

Gómez Alvarez E; Amedro D; Afif C; Gligorovski S; Schoemacker C; Fittschen C; Doussin JF; Wortham H

2013-08-01

 
 
 
 
41

Thermal-induced conversion of maleic and fumaric acid anion radicals in poly(methyl methacrylate)  

International Nuclear Information System (INIS)

Thermal-induced conversion of maleic and fumaric acid anion radicals produced by ? irradiation at 770K in poly(methyl methacrylate) (PMMA) was studied by electron spin resonance (ESR) and optical absorption spectroscopic measurements. The ESR spectra of these acid anion radicals change into two-line spectra with a line separation of ca. 10 G by thermal annealing. This spectrum is assigned to a protonated radical of each acid anion radical. Anion radicals of the solutes are relatively stable below the ? transition point of PMMA and the conversion reaction takes place near this point. This means that the molecular motion of matrix molecule affects the radical conversion reaction

1980-01-01

42

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

UK PubMed Central (United Kingdom)

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

Valentão P; Fernandes E; Carvalho F; Andrade PB; Seabra RM; de Lourdes Basto M

2002-10-01

43

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2001-02-09

44

Reactions of thiyl radicals from thiols and disulphides with antioxidants. A pulse radiolytic study (Preprint No. RC-5)  

International Nuclear Information System (INIS)

Absolute rate constants for the reactions of thiyl radicals generated from a variety of thiols and disulphides with 2,2'-azino bis-(3-ethyl-benzthiazoline-6-sulphonate) (ABTS) and ascorbic acid (AH-) using pulse radiolysis technique have been evaluated. (author). 3 refs

1988-01-01

45

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

International Nuclear Information System (INIS)

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

2012-01-01

46

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. (author).

1987-01-01

47

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1987-09-01

48

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english 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-hyroxyethyl) 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-hyroxyethyl) iminodiacetic acid powders to the HNCHCH2(COOH)2 and HOCH2CH2NCHCH2 (more) (COOH)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.

Aydin, Murat; Baskan, M. Halim; Emre Osmanoglu, M. Y.

2009-09-01

49

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

International Nuclear Information System (INIS)

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

2004-10-08

50

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

Science.gov (United States)

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

Takahashi, Ohgi; Sumita, Masato

2004-10-01

51

Pharmacology of endothelin receptor antagonists ABT-627, ABT-546, A-182086 and A-192621: ex vivo and in vivo studies.  

Science.gov (United States)

Endothelins (ETs), 21-amino-acid peptides involved in the pathogenesis of various diseases, bind to ET(A) and ET(B) receptors to initiate their effects. Based on the same core structure, we have developed four small-molecule ET receptor antagonists, ABT-627 (atrasentan), ABT-546, A-182086 and A-192621, which exhibit differences in selectivity for ET(A) and ET(B) receptors. In this report, we compare the efficacy, potency and pharmacokinetic properties of these four antagonists, including potency in inhibiting ET-1- or Sarafotoxin 6c-induced vessel constriction in isolated arteries and efficacy in antagonizing ET-1-, big ET-1- or Sarafotoxin 6c-induced pressor responses in rats. PMID:12193067

Wessale, Jerry L; Adler, Andrew L; Novosad, Eugene I; Calzadilla, Samuel V; Dayton, Brian D; Marsh, Kennan C; Winn, Martin; Jae, Hwan-Soo; von Geldern, Thomas W; Opgenorth, Terry J; Wu-Wong, J Ruth

2002-08-01

52

Thermal-induced conversion of maleic and fumaric acid anion radicals in poly(methyl methacrylate)  

Energy Technology Data Exchange (ETDEWEB)

Thermal-induced conversion of maleic and fumaric acid anion radicals produced by ..gamma.. irradiation at 77/sup 0/K in poly(methyl methacrylate) (PMMA) was studied by electron spin resonance (ESR) and optical absorption spectroscopic measurements. The ESR spectra of these acid anion radicals change into two-line spectra with a line separation of ca. 10 G by thermal annealing. This spectrum is assigned to a protonated radical of each acid anion radical. Anion radicals of the solutes are relatively stable below the ..gamma.. transition point of PMMA and the conversion reaction takes place near this point. This means that the molecular motion of matrix molecule affects the radical conversion reaction.

Torikai, A.; Fukumoto, M.

1980-04-01

53

Measurement of antioxidant activity with trifluoperazine dihydrochloride radical cation.  

Science.gov (United States)

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 (R(2)) 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. PMID:18622491

Asghar, M N; Khan, I U

2008-06-01

54

Measurement of antioxidant activity with trifluoperazine dihydrochloride radical cation.  

UK PubMed Central (United Kingdom)

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 (R(2)) 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.

Asghar MN; Khan IU

2008-06-01

55

Measurement of antioxidant activity with trifluoperazine dihydrochloride radical cation  

Scientific Electronic Library Online (English)

Full Text Available 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 w (more) ith 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.

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

2008-06-01

56

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; I.U. Khan

2008-01-01

57

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

Directory of Open Access Journals (Sweden)

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

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

2003-01-01

58

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

Scientific Electronic Library Online (English)

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

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

2003-09-01

59

LC-MS/MS determination of 2-(4-((2-(2S,5R)-2-Cyano-5-ethynyl-1-pyrrolidinyl)-2-oxoethylamino)-4-methyl-1-piperidinyl)-4-pyridinecarboxylic acid (ABT-279) in dog plasma with high-throughput protein precipitation sample preparation.  

Science.gov (United States)

As an effective DPP-IV inhibitor, 2-(4-((2-(2S,5R)-2-Cyano-5-ethynyl-1-pyrrolidinyl)-2-oxoethylamino)-4-methyl-1-piperidinyl)-4-pyridinecarboxylic acid (ABT-279), is an investigational drug candidate under development at Abbott Laboratories for potential treatment of type 2 diabetes. In order to support the development of ABT-279, multiple analytical methods for an accurate, precise and selective concentration determination of ABT-279 in different matrices were developed and validated in accordance with the US Food and Drug Administration Guidance on Bioanalytical Method Validation. The analytical method for ABT-279 in dog plasma was validated in parallel to other validations for ABT-279 determination in different matrices. In order to shorten the sample preparation time and increase method precision, an automated multi-channel liquid handler was used to perform high-throughput protein precipitation and all other liquid transfers. The separation was performed through a Waters YMC ODS-AQ column (2.0 x 150 mm, 5 microm, 120 A) with a mobile phase of 20 mm ammonium acetate in 20% acetonitrile at a flow rate of 0.3 mL/min. Data collection started at 2.2 min and continued for 2.0 min. The validated linear dynamic range in dog plasma was between 3.05 and 2033.64 ng/mL using a 50 microL sample volume. The achieved r(2) coefficient of determination from three consecutive runs was between 0.998625 and 0.999085. The mean bias was between -4.1 and 4.3% for all calibration standards including lower limit of quantitation. The mean bias was between -8.0 and 0.4% for the quality control samples. The precision, expressed as a coefficient of variation (CV), was < or =4.1% for all levels of quality control samples. The validation results demonstrated that the high-throughput method was accurate, precise and selective for the determination of ABT-279 in dog plasma. The validated method was also employed to support two toxicology studies. The passing rate was 100% for all 49 runs from one validation study and two toxicology studies. PMID:17590862

Kim, Joseph; Flick, Jeanette; Reimer, Michael T; Rodila, Ramona; Wang, Perry G; Zhang, Jun; Ji, Qin C; El-Shourbagy, Tawakol A

2007-11-01

60

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)

2000-01-01

 
 
 
 
61

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

International Nuclear Information System (INIS)

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

2000-01-01

62

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

International Nuclear Information System (INIS)

[en] 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

1986-02-15

63

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

64

Decarboxylative C-H Arylation of Benzoic Acids under Radical Conditions.  

UK PubMed Central (United Kingdom)

A decarboxylative radical cyclization reaction has been developed for the synthesis of fluorenones. The reaction uses Ag(I)/K(2)S(2)O(8) to oxidatively decarboxylate an aroylbenzoic acid to an aryl radical, which undergoes cyclization to afford fluorenone products in good yield.

Seo S; Slater M; Greaney MF

2012-05-01

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 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 contr (more) ol 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 resid (more) ual 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.

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

2008-03-01

66

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

International Nuclear Information System (INIS)

Molecular orbital calculation and pulse radiolysis method are combined in the studies of interaction of caffeic acid with eaq-, (CH3)2(OH)CCH2., CO2.-, H., ·OH and N3. radicals. Reaction rate constants, UV-visible spectra of electron|·OH adducts, semiquinone radicals of caffeic ions, and the resulted stable products were derived from experimental data. While the radical attacked sites and the most favorable structures of the transient radicals were predicted by calculation. Reaction mechanisms were proposed. (author)

2000-01-01

67

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-07-01

68

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.

2002-10-15

69

Production of 5- and 15-hydroperoxyeicosatetraenoic acid from arachidonic acid by halothane-free radicals generated by UV-irradiation.  

UK PubMed Central (United Kingdom)

The authors are studying the molecular details of the process that begins with hepatic metabolism of halogenated inhalation anesthetics and ends with hepatic necrosis. In previous studies they have shown that the halothane-free radical produced by UV-irradiation is identical to that produced during reductive metabolism of halothane by hepatic cytochrome P-450. In the present study, the authors have examined a mechanism by which free radicals may propagate damage in the endoplasmic reticulum of liver cells. The 1-chloro-2,2,2-trifluoroethyl free radical produced by UV-irradiation of halothane can abstract a hydrogen radical from arachidonic acid to yield 2-chloro-1,1,1-trifluoroethane and an arachidonic acid-free radical. The arachidonic acid-free radical reacts with molecular oxygen to form 5- and 15-hydroperoxyeicosatetraenoic acid. There is considerable evidence that the peroxidation process that we studied in the model system will be similar when the arachidonic acid is an acyl chain on a membrane phospholipid and the free radicals are generated metabolically. The authors suggest that these hydroperoxides may be toxic by acting as intermediates in the pathway of leukotriene production as well as by direct oxidation of membrane components.

Bösterling B; Trudell JR

1984-03-01

70

Production of 5- and 15-hydroperoxyeicosatetraenoic acid from arachidonic acid by halothane-free radicals generated by UV-irradiation.  

Science.gov (United States)

The authors are studying the molecular details of the process that begins with hepatic metabolism of halogenated inhalation anesthetics and ends with hepatic necrosis. In previous studies they have shown that the halothane-free radical produced by UV-irradiation is identical to that produced during reductive metabolism of halothane by hepatic cytochrome P-450. In the present study, the authors have examined a mechanism by which free radicals may propagate damage in the endoplasmic reticulum of liver cells. The 1-chloro-2,2,2-trifluoroethyl free radical produced by UV-irradiation of halothane can abstract a hydrogen radical from arachidonic acid to yield 2-chloro-1,1,1-trifluoroethane and an arachidonic acid-free radical. The arachidonic acid-free radical reacts with molecular oxygen to form 5- and 15-hydroperoxyeicosatetraenoic acid. There is considerable evidence that the peroxidation process that we studied in the model system will be similar when the arachidonic acid is an acyl chain on a membrane phospholipid and the free radicals are generated metabolically. The authors suggest that these hydroperoxides may be toxic by acting as intermediates in the pathway of leukotriene production as well as by direct oxidation of membrane components. PMID:6696254

Bösterling, B; Trudell, J R

1984-03-01

71

Potent antioxidant and radical-scavenging activity of Chenpi--compensatory and cooperative actions of ascorbic acid and citric acid.  

UK PubMed Central (United Kingdom)

Dried peels of Satsuma mandarin (Citrus unshiu Marcov.) have been used as traditional Chinese and Japanese medicine, which are called 'Chenpi'. In our present study, cold and hot water extracts of Chenpi exhibited a strong inhibitory activity against linoleic acid peroxidation and 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical-scavenging activity compared with o-methanol extract. When these extracts were separated into ethanol-soluble(ES) and ethanol-precipitable fractions, the dominant antioxidant and radical-scavenging activities were detected in the ES fractions, which suggests that these antioxidant and radical-scavenging activities are responsible for water-soluble and low-molecular-weight substances. As possible active principles for antioxidant activities in the water extracts, the contents of ascorbic acid and citric acid in these extracts were measured, and the antioxidant and radical-scavenging activities of these substances were assayed at various concentrations. The experimental results indicate that the antioxidant activity against lipid peroxidation in the water extracts is dominantly associated with citric acid, and the DPPH radical-scavenging activity of the water extracts is majorly responsible for ascorbic acid, suggesting a compensatory action of ascorbic acid and citric acid in expression of the antioxidant and radical-scavenging activities of Chenpi.

Higashi-Okai K; Ishikawa A; Yasumoto S; Okai Y

2009-12-01

72

Radical processes in radiolysis of monocarboxylic acids in liquid phase. [Gamma radiation  

Energy Technology Data Exchange (ETDEWEB)

A possibility of investigating short-lived radicals arising at radiolysis of liquid monocarbon acids, particularly, acetic and propionic acids by means of spin traps (c-phenyl-ter.butylnitron, ter.-butylmethylenenitron, ter.-nitroisobuthane, 2, 4, 6-tri-ter.-butyl-nitrosobenzene) is disclosed. Solutions of spin traps have been vacuumized and ..gamma..-irradiated with /sup 60/Co at 20 deg or - 196 deg, then they have been frozen. EPR spectra have been taken at temperatures from - 24 to 10 deg. Alkyl and acyl radicals are the basic radical products of radiolysis of acetic and propionic acids while CH/sub 2/COOH and CH/sub 3/CHCOOH are, probably, formed as secondary products. Additions of effective electron acceptor-benzophenone decrease yield of adducts with acyl radicals in the propionic acid and they do not affect yield of adducts with C/sub 2/H/sub 5/.

Fel' dman, V.I.; Belevskij, V.N.; Yarkov, S.P. (Moskovskij Gosudarstvennyj Univ. (USSR))

1983-01-01

73

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

International Nuclear Information System (INIS)

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

2001-01-01

74

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

Science.gov (United States)

Molecular calculations coupled with pulse radiolysis studies are performed to understand the reactions of radicals with caffeic acid. From molecular calculation, we find that eaq- and .OH tend to form adducts with caffeic acid, while N3 tends to abstract H from 4-hydroxyl group in benzene ring, generating a semi-quinoid radical. Based on comparison of the heat of formation, the most favorable radical attack sites and the most stable radical structures are predicted. The calculation results suggest that the stability of the electron adducts caffeic ions, in good agreement with their experimental second-order decay rate constants (2k=(1.1+/-0.2)×109, (6.0+/-0.4)×107 and (2.0+/-0.2)×107M-1s-1, respectively), determined by pulse radiolysis. Molecular calculations seem to be a powerful tool to predict the stability and structures of transient radicals.

Li, X.; Cai, Z.; Katsumura, Y.; Wu, G.; Muroya, Y.

2001-01-01

75

New Convenient Approach for the Synthesis of Benzyl 2H-Chromenones and their ?-Amylase Inhibitory, ABTS.+ Scavenging Activities.  

UK PubMed Central (United Kingdom)

Series of new benzyl 2H-chromenones 6a-n was synthesized by Pechmann condensation of substituted benzyl resorcinols 2a-c and 3a with various ?-ketoesters such as ethyl 3-oxobutanoate, ethyl 3-oxo-3-phenylpropanoate, ethyl 4- chloro-3-oxobutanoate, ethyl 4,4,4-trifluoro-3-oxobutanoate and ethyl 2-chloro-3-oxobutanoate 5a-e in very good yields. Synthesized compounds 6a-n were screened for their ?-amylase inhibitory, and ABTS.+ scavenging activities. In the present series of compounds, compound 8-benzyl-7-hydroxy-4-phenyl-2H-chromen-2-one 6c and 8-benzyl-7-hydroxy-4- methyl-2H-chromen-2-one 6a were most potent ABTS.+ radical scavenging and ?-amylase inhibitor. Although compound 6,8-dibenzyl-7-hydroxy-4-(trifluoromethyl)-2H-chromen-2-one 6h displayed potent ABTS.+ free radical scavenging potential, it was found poor in inhibiting pancreatic ?-amylase.

Kumar JA; Tiwari AK; Saidachary G; Kumar DA; Ali Z; Sridhar B; Raju BC

2013-07-01

76

New convenient approach for the synthesis of benzyl 2H-chromenones and their ?-amylase Inhibitory, ABTS.+ scavenging activities.  

UK PubMed Central (United Kingdom)

Series of new benzyl 2H-chromenones 6a-n was synthesized by Pechmann condensation of substituted benzyl resorcinols 2a-c and 3a with various ?-ketoesters such as ethyl 3-oxobutanoate, ethyl 3-oxo-3-phenylpropanoate, ethyl 4- chloro-3-oxobutanoate, ethyl 4,4,4-trifluoro-3-oxobutanoate and ethyl 2-chloro-3-oxobutanoate 5a-e in very good yields. Synthesized compounds 6a-n were screened for their ?-amylase inhibitory, and ABTS.+ scavenging activities. In the present series of compounds, compound 8-benzyl-7-hydroxy-4-phenyl-2H-chromen-2-one 6c and 8-benzyl-7-hydroxy-4- methyl-2H-chromen-2-one 6a were most potent ABTS.+ radical scavenging and ?-amylase inhibitor. Although compound 6,8-dibenzyl-7-hydroxy-4-(trifluoromethyl)-2H-chromen-2-one 6h displayed potent ABTS.+ free radical scavenging potential, it was found poor in inhibiting pancreatic ?-amylase.

Kumar JA; Tiwari AK; Saidachary G; Kumar DA; Ali Z; Sridhar B; Raju BC

2013-09-01

77

Reaction of OH with benzoic acid. Isomer distribution in the radical intermediates  

International Nuclear Information System (INIS)

[en] Products of the reaction of radiation-produced OH radicals with benzoic acid under conditions where the intermediate hydroxycyclohexadienyl radicals are quantitatively oxidized to hydroxybenzoic acids was examined by liquid chromatographic methods. In N2O-saturated 1 mM benzoic acid solutions containing 0.5 mM ferricyanide as the radical oxidant the initial radiation chemical yields of o-, m-, and p-hydroxybenzoic acids are 1.7, 2.3, and 1.2, respectively. Decarboxylation contributes an additional phenol yield of 0.4 to give a total product yield of 5.6 which accounts for essentially all of the OH radicals produced in this system. Material balance considerations show that no major product is unaccounted for. The initially produced hydroxybenzoic acids are, however, not consumed to any important extent in the secondary processes so that the resultant phenoxyl radicals must, in this mixed-radical system, be reduced back to the original products rather than being oxidized further. A detailed model is described, which allows numerical integration methods to be used to take the competitive effects of the secondary processes into account and to describe the course of the reaction quite well up to conversions of approximately 25 percent. (auth)

1975-08-14

78

Resistance to ABT-737 in activated T lymphocytes: molecular mechanisms and reversibility by inhibition of the calcineurin-NFAT pathway.  

UK PubMed Central (United Kingdom)

Dynamic regulation of the intrinsic apoptosis pathway controls central and peripheral lymphocyte deletion, and may interfere with the pro-apoptotic potency of B-cell lymphoma 2 inhibitors such as ABT-737. By following a T-cell receptor (TCR) transgenic population of alloantigen-specific T cells, we found that sensitivity to ABT-737 radically changed during the course of allo-specific immune responses. Particularly, activated T cells were fully resistant to ABT-737 during the first days after antigen recognition. This phenomenon was caused by a TCR-calcineurin-nuclear factor of activated T cells-dependent upregulation of A1, and was therefore prevented by cyclosporine A (CsA). As a result, exposure to ABT-737 after alloantigen recognition induced selection of alloreactive T cells in vivo, whereas in combination with low-dose CsA, ABT-737 efficiently depleted alloreactive T cells in murine host-versus-graft and graft-versus-host models. Thus, ABT-737 resistance is not a prerogative of neoplastic cells, but it physiologically occurs in T cells after antigen recognition. Reversibility of this process by calcineurin inhibitors opens new pharmacological opportunities to modulate this process in the context of cancer, autoimmunity and transplantation.

Cippà PE; Kraus AK; Lindenmeyer MT; Chen J; Guimezanes A; Bardwell PD; Wekerle T; Wüthrich RP; Fehr T

2012-01-01

79

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

Science.gov (United States)

Reactions of ?-hydroxyalkyl radicals derived from 2-propanol, ethanol and methanol with nicotinamide (NICAM) and 6-methyl nicotinic acid (6-MNA) were studied at various pHs using pulse radiolysis technique. It is found that ?-hydroxyalkyl radicals react with NICAM and 6-MNA at pHs when nitrogen is in the protonated state. In these reactions, radical adducts of NICAM/6-MNA with ?-hydroxyalkyl radicals are formed which have absorption maxima at about 340-350 nm which subsequently decay to give pyridinyl type of radicals of NICAM and 6-MNA having ?max at 410 nm. Rate constants for the reactions of (CH3)2COH, CH3CHOH and CH2OH radicals with NICAM and 6-MNA were found to have linear dependence on reduction potentials of corresponding ?-hydroxyalkyl radicals. Adducts formed in the reactions of CH3CHOH and CH2OH radicals with both NICAM and 6-MNA decayed slowly compared to the decay of adduct formed in reactions with (CH3)2COH radicals.

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

2012-06-01

80

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

Scientific Electronic Library Online (English)

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

Aydin, Murat

2010-12-01

 
 
 
 
81

Trans-fatty acids and radical stress: what are the real culprits?  

Science.gov (United States)

Free radical-catalysed cis-trans isomerization of unsaturated lipids in biomimetic models and their significance in eukaryotic cells have been explored in the last few years, an integrating hypothesis being that trans-fatty acids have their origins in both dietary sources and from isomerization of natural isomers by an endogenous radical stress. In this perspective, a summary of the achievements and a discussion of the possible biological sources of isomerizing radical species are given, indicating a need for further research on thiyl radical generation in biological systems. In this context, crucial questions remain to be answered by free radical research involving membrane lipids, thus contributing to lipidomics and embracing biology and medicine. PMID:16766191

Chatgilialoglu, Chryssostomos; Ferreri, Carla; Lykakis, Ioannis N; Wardman, Peter

2006-06-12

82

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-09-15

83

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english Powders of N- acetyl- L- leucine and N- methyl- L- glutamic acid were gamma irradiated and the free radicals formed were investigated at room temperature by electron paramagnetic resonance technique. The free radicals formed in compounds were attributed to the (CH3)2CCH2CH(NHCOCH3)COOH and HOOCCH2CH2C (NHCH3)COOH radicals respectively. Both radicals are very stable and we could observe them for five months without almost intensity diminution at room temperature. The g val (more) ues of the radicals and the hyperfine structure constants of the free electron with nearby protons and 14N nucleus were determined. The results were found to be in good agreement with the existing literature data.

Aydin, Murat

2010-09-01

84

The reaction of oxygen with radicals from oxidation of tryptophan and indole-3-acetic acid.  

UK PubMed Central (United Kingdom)

The oxidation of tryptophan and indole-3-acetic acid (IAA) by the dibromine radical anion or peroxidase from horseradish in aqueous solution was investigated and compared, especially with respect to the involvement of oxygen and superoxide. Using EPR with spin-trapping, the tryptophanyl radical, generated by either method was found to react with oxygen, although this reaction is too slow to be observed by pulse radiolysis (k < 5 x 10(6) dm3 mol-1 s-1). No superoxide results from this reaction, thus excluding an electron-transfer mechanism and suggesting the formation of a tryptophan peroxyl radical, possibly in a reversible process. These observations imply that in proteins where the tryptophanyl radical exists as a stable species it must either have its reactivity modified by the protein environment or be inaccessible to oxygen. The related molecule LAA is oxidized by either peroxidase or Br2.- to a radical cation that decarboxylates to yield a skatolyl radical. The latter reacts with oxygen to give a peroxyl radical that does not release superoxide. However, O2.- is formed during the peroxidase-catalyzed oxidation of indoleacetic acid. This supports the hypothesis that the peroxidase can act in an oxidase cycle involving ferrous enzyme and compound III, with superoxide as a product.

Candeias LP; Wardman P; Mason RP

1997-09-01

85

Formation and reactivity of vinylperoxyl radicals in aqueous solutions  

Energy Technology Data Exchange (ETDEWEB)

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

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

1995-03-30

86

Peroxyl-radical-scavenging activity of garlic: 2-propenesulfenic acid versus allicin.  

UK PubMed Central (United Kingdom)

The OOH radical reactions with allicin and its Cope elimination products (2-propenesulfenic acid and thioacrolein) in aqueous solution have been studied. The CBS-QB3 quantum chemistry method has been used, with geometries and frequencies at BHandHLYP/6-311++G(d,p) level and conventional transition state theory. 2-Propenesulfenic acid is predicted to be over 1000 times more reactive toward OOH radical than allicin (2.60 x 10(7) vs 7.38 x 10(3) L mol(-1) s(-1), at 298 K). Accordingly, our results strongly support the novel suggestion by Vaidya et al. (Angew. Chem., Int. Ed. 2009, 48, 157) that the active ingredient responsible for the free radical scavenging activity of garlic is actually 2-propenesulfenic acid and not allicin. In addition, direct reaction branching ratios and product distribution for the three studied reactions are proposed for the first time.

Galano A; Francisco-Marquez M

2009-12-01

87

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 -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.

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

2010-12-01

88

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

89

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

International Nuclear Information System (INIS)

[en] 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.

2010-01-01

90

Drug-induced protein free radical formation is attenuated by unsaturated fatty acids by scavenging drug-derived phenyl radical metabolites.  

Science.gov (United States)

Aromatic amine drugs like aminoglutethimide (AG) and related congeners have been shown to produce phenyl radicals through metabolism by myeloperoxidase (MPO)/H(2)O(2), which has been proposed to play a role in drug-induced agranulocytosis. AG has also been shown to induce MPO protein radical formation, but the ultimate fate of these metabolically generated phenyl radicals is still unknown. We tested the reactivity of linoleic acid (LA) and GSH with aniline-based compounds in the presence of horseradish peroxidase (HRP)/H(2)O(2) by measuring oxygen consumption. We found a qualitative correlation between drugs or xenobiotics that formed phenyl radical metabolites with the cooxidation of LA. Most compounds that reacted with LA did not react with GSH. Furthermore, an AG-derived phenyl radical was detected by EPR spin-trapping with MNP (2-methyl-2-nitrosopropane), in a reaction containing AG and HRP/H(2)O(2); these spectra were attenuated in the presence of LA and docosahexaenoic acid (DHA) indicating that phenyl radical scavenging occurred. Since it has been proposed that the phenyl radical metabolite leads to protein radical formation on MPO, we investigated the effect of LA and DHA in immuno-spin trapping experiments with MPO-containing HL-60 cell lysate. Using anti-DMPO, a protein radical was detected on a putative MPO fragment from the reaction of DMPO, AG, and glucose/glucose oxidase. When LA or DHA was included in this reaction, protein radical formation was significantly inhibited. Our results show that certain polyunsaturated fatty acids (PUFAs) act as scavengers of aromatic amine drug-derived phenyl radicals which in turn prevent protein radical formation. However, the interaction of phenyl radical drug metabolites with PUFAs will be dictated by their relative concentrations compared to those of other targets. Most importantly, it is possible to differentiate peroxidase substrates that generate phenyl radical metabolites from N-centered radicals on the basis of their reactivity toward GSH vs PUFAs, and PUFAs are targets for metabolically generated phenyl radicals. PMID:21671642

Narwaley, Malyaj; Michail, Karim; Arvadia, Pratik; Siraki, Arno G

2011-06-28

91

Drug-induced protein free radical formation is attenuated by unsaturated fatty acids by scavenging drug-derived phenyl radical metabolites.  

UK PubMed Central (United Kingdom)

Aromatic amine drugs like aminoglutethimide (AG) and related congeners have been shown to produce phenyl radicals through metabolism by myeloperoxidase (MPO)/H(2)O(2), which has been proposed to play a role in drug-induced agranulocytosis. AG has also been shown to induce MPO protein radical formation, but the ultimate fate of these metabolically generated phenyl radicals is still unknown. We tested the reactivity of linoleic acid (LA) and GSH with aniline-based compounds in the presence of horseradish peroxidase (HRP)/H(2)O(2) by measuring oxygen consumption. We found a qualitative correlation between drugs or xenobiotics that formed phenyl radical metabolites with the cooxidation of LA. Most compounds that reacted with LA did not react with GSH. Furthermore, an AG-derived phenyl radical was detected by EPR spin-trapping with MNP (2-methyl-2-nitrosopropane), in a reaction containing AG and HRP/H(2)O(2); these spectra were attenuated in the presence of LA and docosahexaenoic acid (DHA) indicating that phenyl radical scavenging occurred. Since it has been proposed that the phenyl radical metabolite leads to protein radical formation on MPO, we investigated the effect of LA and DHA in immuno-spin trapping experiments with MPO-containing HL-60 cell lysate. Using anti-DMPO, a protein radical was detected on a putative MPO fragment from the reaction of DMPO, AG, and glucose/glucose oxidase. When LA or DHA was included in this reaction, protein radical formation was significantly inhibited. Our results show that certain polyunsaturated fatty acids (PUFAs) act as scavengers of aromatic amine drug-derived phenyl radicals which in turn prevent protein radical formation. However, the interaction of phenyl radical drug metabolites with PUFAs will be dictated by their relative concentrations compared to those of other targets. Most importantly, it is possible to differentiate peroxidase substrates that generate phenyl radical metabolites from N-centered radicals on the basis of their reactivity toward GSH vs PUFAs, and PUFAs are targets for metabolically generated phenyl radicals.

Narwaley M; Michail K; Arvadia P; Siraki AG

2011-07-01

92

Free radical addition of 2-bromoalkanoic acids to alkenes  

Energy Technology Data Exchange (ETDEWEB)

The benzoyl peroxide-catalyzed reaction of 2-bromoalkanoic acids such as bromoacetic, 2-bromopropionic, and 2-bromobutyric acid with 1-alkenes was found to proceed through the addition of the C-Br bond across the double bond followed by cyclization affording 4-alkanolides in good yields. 16 references, 3 tables.

Nakano, T.; Kayama, M.; Nagai, Y.

1987-03-01

93

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2001-07-01

94

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

Directory of Open Access Journals (Sweden)

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; Weronika Wenta

2012-01-01

95

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

UK PubMed Central (United Kingdom)

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.

Matilainen K; Hämäläinen T; Savolainen A; Sipiläinen-Malm T; Peltonen J; Erho T; Smolander M

2012-02-01

96

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2005-02-01

97

Catalytic mechanism of a heme and tyrosyl radical-containing fatty acid ?-(di)oxygenase.  

UK PubMed Central (United Kingdom)

The steady-state catalytic mechanism of a fatty acid ?-(di)oxygenase is examined, revealing that a persistent tyrosyl radical (Tyr379(•)) effects O(2) insertion into C(?)-H bonds of fatty acids. The initiating C(?)-H homolysis step is characterized by apparent rate constants and deuterium kinetic isotope effects (KIEs) that increase hyperbolically upon raising the concentration of O(2). These results are consistent with H(•) tunneling, transitioning from a reversible to an irreversible regime. The limiting deuterium KIEs increase from ?30 to 120 as the fatty acid chain is shortened from that of the native substrate. In addition, activation barriers increase in a manner that reflects decreased fatty acid binding affinities. Anaerobic isotope exchange experiments provide compelling evidence that Tyr379(•) initiates catalysis by H(•) abstraction. C(?)-H homolysis is kinetically driven by O(2) trapping of the ?-carbon radical and reduction of a putative peroxyl radical intermediate to a 2(R)-hydroperoxide product. These findings add to a body of work which establishes large-scale hydrogen tunneling in proteins. This particular example is novel because it involves a protein-derived amino acid radical.

Mukherjee A; Angeles-Boza AM; Huff GS; Roth JP

2011-01-01

98

Stable radical in the ribose moiety of x-irradiated 3'-cytidylic acid and its relation to a similar radical in cytidine: an ESR-ENDOR study  

International Nuclear Information System (INIS)

A stable free radical, labeled 3?H, is formed in 3'-cytidylic acid (3'CMP) single crystals by x-irradiating at 770K and then warming to above room temperature. It remains stable up to 1500C. ESR and ENDOR measurements explicitly indicate a structure of the form H2C - CX = CHY. The same free radical structure is assigned to a radical in cytidine (whose spectral parameters have been analyzed by Hampton and Alexander). The chemical structures of groups N and Y are tentatively assigned for the 3?H radical in both 3'CMP and cytidine. Measurements on the formation of the 3?H radical in 3'CMP indicate that the precursor radical is due to hydrogen abstraction of C/sub 5'/. The activation energy of the conversion is ca. 30 kcal/mole. A mechanism is postulated for the formation of the 3?H radical in both 3'CMP and cytidine. It is shown to account for the decay of the 3?H radical in cytidine and the presence of yet another hitherto unassigned radical product observed by Allison and Alexander. The postulated mechanism provides a reaction scheme for arriving at various end products identified in aqueous radiolysis studies of DNA and its components

1976-01-01

99

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

International Nuclear Information System (INIS)

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

1994-01-01

100

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1995-03-01

 
 
 
 
101

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

International Nuclear Information System (INIS)

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

1995-01-01

102

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.

Erol Ayranci; Naciye Erkan

2013-01-01

103

Radical scavenging capacity of methanolic Phillyrea latifolia L. extract: anthocyanin and phenolic acids composition of fruits.  

Science.gov (United States)

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 IC(50) 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. PMID:23364751

Ayranci, Erol; Erkan, Naciye

2013-01-30

104

Radical scavenging capacity of methanolic Phillyrea latifolia L. extract: anthocyanin and phenolic acids composition of fruits.  

UK PubMed Central (United Kingdom)

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 IC(50) 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.

Ayranci E; Erkan N

2013-01-01

105

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

International Nuclear Information System (INIS)

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

1995-01-01

106

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

Energy Technology Data Exchange (ETDEWEB)

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 {gamma}-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).

Kantoglu, O.; Ozbey, T.; Gueven, O. [Hacettepe Univ., Ankara (Turkey)

1995-10-01

107

Iron-catalyzed decarboxylative alkenylation of cycloalkanes with arylvinyl carboxylic acids via a radical process  

Science.gov (United States)

Summary A Fe(acac)3-catalyzed decarboxylative coupling of 2-(aryl)vinyl carboxylic acids with cycloalkanes was developed by using DTBP as an oxidant through a radical process. This reaction tolerates a wide range of substrates, and products are obtained in good to excellent yields (71–95%). The reaction also shows excellent stereoselectivity, and only trans-isomers are obtained.

Zhao, Jiancan; Fang, Hong

2013-01-01

108

Copper-catalyzed trifluoromethylation of aryl- and vinylboronic acids with generation of CF3-radicals.  

UK PubMed Central (United Kingdom)

The selective trifluoromethylation of aryl- and vinylboronic acids proceeds smoothly with CF3SO2Na (Langlois reagent) in the presence of copper catalysts and t-BuOOH. Therefore, the method relies both on transition metal catalysis and selective radical reactions. Advantageously, the protocol can be performed at room temperature under an air atmosphere and avoids the issue of poor regioselectivity.

Li Y; Wu L; Neumann H; Beller M

2013-04-01

109

Synthesis of functionalized nitrogen heterocycles by radical decarboxylation of ?- and ?-amino acids  

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10 pages, 1 figure, 2 tables, 9 schemes.-- Supporting information available: Synthesis and spectroscopic data of compounds 18–22 and 25 and the synthetic intermediates 44 and 45. , Iodinated or oxygenated nitrogen heterocycles are obtained by radical decarboxylation of ?- and ?-amino acids. This mild, ...

Boto, Alicia; Hernández, Rosendo; León, Yolanda de; Murguía, José R.; Rodríguez-Afonso, Abigail

110

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

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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 hig...

Erol Ayranci; Naciye Erkan

111

Niobium Complexes As Lewis Acid and Radical Catalysts  

Energy Technology Data Exchange (ETDEWEB)

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

Wayne Tikkanen

2005-10-01

112

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

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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- ...

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

113

Is lipid peroxidation of polyunsaturated acids the only source of free radicals that induce aging and age-related diseases?  

UK PubMed Central (United Kingdom)

The increase in free radicals is hypothesised to cause aging and age-related diseases. The most common source of free radicals is thought to be superoxide. This superoxide is claimed to be released from mitochondria during the enzymatic transformation of oxygen to water by a "leakage" process. This article presents evidence that leakage does not occur. Instead, protonated superoxide radicals are generated by lipid peroxidation processes. In nature, polyunsaturated fatty acids (PUFAs) represent particularly oxygen-sensitive compounds. Apparently, nature uses this sensitivity for signalling processes by producing lipidhydroperoxides (LOOHs) by any change to cell membrane structure. LOOHs easily undergo further enzymatic transformations to compounds which contribute to activation of genes. Bivalent metal ions within the active site of lipoxygenases catalyse LOOH production. The metal ions generate radicals which are transformed within the enzyme complex to non-radical molecules. Thus radicals never leave the enzyme complex except in severe stress situations. In this case the radical intermediates attack bonds, keeping the metal ion in its complex state. Thus, metal ions are released and react in a Fenton reaction with LOOH molecules produced earlier by lipoxygenase to form LO. radicals. Radicals are typically four orders of magnitude more reactive than non-radical molecules. Their action is not under genetic control, they attack nearly all biological molecules, destroying lipids, proteins, nucleic acids, hormones and enzymes until the radicals are quenched by scavenger molecules. The principal degradation routes are outlined in this review. Lysophospholipids are generated in large amounts after stress by activation of phospholipases and are transformed to LO. radicals. These can abstract a hydrogen radical from a lysophospholipid. The radical thus formed adds oxygen and decomposes to a 2-oxolysophospholipid and a HOO. radical (protonated superoxide). HOO. radicals in turn abstract hydrogen atoms from other molecules and produce H(2)O(2). Since any cell preparation method causes membrane destruction, it is inevitable that protonated superoxide is generated, explaining why H(2)O(2) molecules are found as "byproducts" of many reactions.

Spiteller G

2010-02-01

114

Synthesis and antioxidant capacities of hydroxyl derivatives of cinnamoylphenethylamine in protecting DNA and scavenging radicals.  

UK PubMed Central (United Kingdom)

Cinnamoylphenethylamine (CNPA) derivatives including feruloylphenethylamine (FRPA), caffeoylphenethylamine (CFPA), cinnamoyltyramine (CNTA), feruloyltyramine (FRTA) and caffeoyltyramine (CFTA) were synthesized in order to investigate the influence of the number and position of hydroxyl group on Cu(2+)/glutathione (GSH) and 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced oxidation of DNA. The radical-scavenging properties of these CNPA derivatives were also evaluated by trapping 2,2'-azinobis(3-ethylbenzothiazoline-6-sulphonate) cationic radical (ABTS(+•)), 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH) and galvinoxyl radical. In addition, these CNPA derivatives were tested by linoleic acid (LH)-?-carotene-bleaching experiment. The chemical kinetic was employed to treat the results from AAPH-induced oxidation of DNA and gave the order of antioxidant ability as CFTA > CFPA > FRTA > FRPA. CFTA and CFPA also possessed high abilities to inhibit Cu²(+)/GSH-mediated degradation of DNA, whereas FRPA and FRTA can protect LH against the auto-oxidation efficiently. Finally, CFPA and FRPA exhibited high activity in trapping ABTS(+•), DPPH and galvinoxyl radicals. Therefore, the cinnamoyl group bearing ortho-dihydroxyl or hydroxyl with ortho-methoxyl benefited for CNPA derivatives to protect DNA, while hydroxyl in tyramine cannot enhance the radical-scavenging abilities of CNPA derivatives.

Yang Y; Song ZG; Liu ZQ

2011-04-01

115

Radicals scavenging by molybdates and tungstates in water-formic acid systems  

Energy Technology Data Exchange (ETDEWEB)

The radiation reduction of polymolybdates and polytungstates in aqueous-formic acid systems has been investigated. The reductions of 6- to 5-valent compounds take place and the molybdenum and tungsten blue compounds are formed. The yields and the structures of the blue formed compounds depend on the initial concentrations of the compounds, matrix composition and dose applied. The highest measured yields (in the case of molybdates) reaching the value of 12 equivalents per 100 eV can be explained on the basis of two-electron reduction processes with participation of HC/OH/2 radicals. The efficiencies of radicals scavenging by molybdates and tungstates have been measured.

Kalecinski, J. (Polska Akademia Nauk, Wroclaw. Inst. Niskich Temperatur i Badan Strukturalnych)

1981-01-01

116

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

UK PubMed Central (United Kingdom)

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

Kiliç I; Ye?ilo?lu Y

2013-11-01

117

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

Science.gov (United States)

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

Kiliç, Ismail; Ye?ilo?lu, Ye?im

2013-07-08

118

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  

Directory of Open Access Journals (Sweden)

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.

Yoshinori Kadoma; Seiichiro Fujisawa

2008-01-01

119

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.  

Science.gov (United States)

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 (k(inh)/k(p)) 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. PMID:18923340

Kadoma, Yoshinori; Fujisawa, Seiichiro

2008-10-15

120

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2000-03-01

 
 
 
 
121

In Vitro Antibacterial Potency and Spectrum of ABT-492, a New Fluoroquinolone  

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ABT-492 demonstrated potent antibacterial activity against most quinolone-susceptible pathogens. The rank order of potency was ABT-492 > trovafloxacin > levofloxacin > ciprofloxacin against quinolone-susceptible staphylococci, streptococci, and enterococci. ABT-492 had activity comparable to those o...

Nilius, Angela M.; Shen, Linus L.; Hensey-Rudloff, Dena; Almer, Laurel S.; Beyer, Jill M.; Balli, Darlene J.; Cai, Yingna

122

Formation and reactivity of phenylperoxyl radicals in aqueous solutions  

International Nuclear Information System (INIS)

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

1994-08-18

123

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

Directory of Open Access Journals (Sweden)

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.

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

2006-01-01

124

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

Directory of Open Access Journals (Sweden)

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

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

2010-01-01

125

Free radical scavenging capacity and antioxidant activity of cochineal (Dactylopius coccus C.) extracts  

UK PubMed Central (United Kingdom)

Carminic acid (CA) is a natural red pigment produced by Dactylopius coccus C. insects. It is widely used in the food industry to replace synthetic colourants. Despite being known for a long time, its antioxidant properties have not been studied so far. The aim of this study was to determine CA activities by different methods namely, free radical scavenging capacity against DPPH and ABTS radicals as well as its inhibition ability of ?-carotene bleaching enzymatically induced by lipoxygenase (LOX). CA exhibited a remarkable antiradical activity similar to that of known antioxidants such as quercetin, ascorbic acid and trolox. Effectiveness of CA to protect ?-carotene in the co-oxidation with linoleic acid is attributed to enzymatic inhibition of LOX rather than peroxyl radical trapping.

González EvangelinaA; García ElisaM; Nazareno MónicaA

2010-03-01

126

The roles of hydroxyl radicals, photo-generated holes and oxygen in the photocatalytic degradation of humic acid  

Science.gov (United States)

This article is aimed at studying on the roles of the hydroxyl radicals, photo-generated holes, and oxygen in the photocatalytic degradation of humic acid (HA) in acid and alkaline conditions. The results indicate that hydroxyl radicals' scavenger alone can inhibit the photocatalytic degradation process completely in alkaline condition, which implies that photo-generated holes cannot directly degrade the organic matter in alkaline condition. Moreover, the reaction sites between hydroxyl radicals and HA is on the TiO2 surface in acid condition. But in alkaline condition, hydroxyl radicals diffuse and react with HA in the solution. The generation of hydroxyl radicals almost stops and the photocatalytic degradation is inhibited seriously without oxygen, which illustrates that oxygen plays an important role in the photocatalytic degradation of HA.

Yan, Xiaoju; Bao, Ruiling; Yu, Shuili; Li, Qiongfang; Jing, Qingfeng

2012-09-01

127

Inhibition of free radical-induced erythrocyte hemolysis by 2-O-substituted ascorbic acid derivatives.  

UK PubMed Central (United Kingdom)

Inhibitory effects of 2-O-substituted ascorbic acid derivatives, ascorbic acid 2-glucoside (AA-2G), ascorbic acid 2-phosphate (AA-2P), and ascorbic acid 2-sulfate (AA-2S), on 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced oxidative hemolysis of sheep erythrocytes were studied and were compared with those of ascorbic acid (AA) and other antioxidants. The order of the inhibition efficiency was AA-2S> or =Trolox=uric acid> or =AA-2P> or =AA-2G=AA>glutathione. Although the reactivity of the AA derivatives against AAPH-derived peroxyl radical (ROO(*)) was much lower than that of AA, the derivatives exerted equal or more potent protective effects on AAPH-induced hemolysis and membrane protein oxidation. In addition, the AA derivatives were found to react per se with ROO(*), not via AA as an intermediate. These findings suggest that secondary reactions between the AA derivative radical and ROO(*) play a part in hemolysis inhibition. Delayed addition of the AA derivatives after AAPH-induced oxidation of erythrocytes had already proceeded showed weaker inhibition of hemolysis compared to that of AA. These results suggest that the AA derivatives per se act as biologically effective antioxidants under moderate oxidative stress and that AA-2G and AA-2P may be able to act under severe oxidative stress after enzymatic conversion to AA in vivo.

Takebayashi J; Kaji H; Ichiyama K; Makino K; Gohda E; Yamamoto I; Tai A

2007-10-01

128

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

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

Ismaila Muhammad Sani; Shahid Iqbal; Kim Wei Chan; Maznah Ismail

2012-01-01

129

Urocanic acid as an efficient hydroxyl radical scavenger: a quantum theoretical study.  

Science.gov (United States)

The photoisomerization of urocanic acid (UCA)--which is present in human skin epidermis, where it acts as a sunscreen--from its trans isomer to its cis isomer upon exposure to UV-B radiation is known to cause immunosuppression. In recent years, the antioxidant properties of UCA (it acts as a hydroxyl radical scavenger) have also been recognized. In view of this, the mechanisms of stepwise reactions of trans-UCA with up to four hydroxyl radicals were investigated. The molecular geometries of the different species and complexes involved in the reactions (reactant, intermediate and product complexes, as well as transition states) were optimized via density functional theory in the gas phase. Solvation in aqueous media was treated with single point energy calculations using DFT and the polarizable continuum model. Single point energy calculations in the gas phase and aqueous media were also carried out using second-order Møller-Plesset perturbation theory (MP2). The AUG-cc-pVDZ basis set was employed in all calculations. Corrections for basis set superposition error (BSSE) were applied. Vibrational frequency analysis was performed for each optimized structure to ensure the validity of the optimized transition states. It was found that the binding of the first OH? radical to UCA involves a positive energy barrier, while subsequent reactions of OH? radicals are exergonic. Transition states were successfully located, even in those cases where the barrier energies were found to be negative. The cis-trans isomerization barrier energy of UCA and that of the first OH? radical addition to UCA are comparable, meaning that both processes can occur simultaneously. It was found that UCA could serve as an antioxidant in the form of an efficient OH? radical scavenger. PMID:20361345

Tiwari, Saumya; Chand Mishra, Phool

2010-04-02

130

Urocanic acid as an efficient hydroxyl radical scavenger: a quantum theoretical study.  

UK PubMed Central (United Kingdom)

The photoisomerization of urocanic acid (UCA)--which is present in human skin epidermis, where it acts as a sunscreen--from its trans isomer to its cis isomer upon exposure to UV-B radiation is known to cause immunosuppression. In recent years, the antioxidant properties of UCA (it acts as a hydroxyl radical scavenger) have also been recognized. In view of this, the mechanisms of stepwise reactions of trans-UCA with up to four hydroxyl radicals were investigated. The molecular geometries of the different species and complexes involved in the reactions (reactant, intermediate and product complexes, as well as transition states) were optimized via density functional theory in the gas phase. Solvation in aqueous media was treated with single point energy calculations using DFT and the polarizable continuum model. Single point energy calculations in the gas phase and aqueous media were also carried out using second-order Møller-Plesset perturbation theory (MP2). The AUG-cc-pVDZ basis set was employed in all calculations. Corrections for basis set superposition error (BSSE) were applied. Vibrational frequency analysis was performed for each optimized structure to ensure the validity of the optimized transition states. It was found that the binding of the first OH? radical to UCA involves a positive energy barrier, while subsequent reactions of OH? radicals are exergonic. Transition states were successfully located, even in those cases where the barrier energies were found to be negative. The cis-trans isomerization barrier energy of UCA and that of the first OH? radical addition to UCA are comparable, meaning that both processes can occur simultaneously. It was found that UCA could serve as an antioxidant in the form of an efficient OH? radical scavenger.

Tiwari S; Chand Mishra P

2011-01-01

131

Peroxynitrite-derived carbonate and nitrogen dioxide radicals readily react with lipoic and dihydrolipoic acid.  

Science.gov (United States)

Alpha-lipoic acid (LA) and dihydrolipoic acid (DHLA) may have a role as antioxidants against nitric oxide-derived oxidants. We previously reported that peroxynitrite reacts with LA and DHLA with second-order rate constants of 1400 and 500 M(-1) s(-1), respectively, but indicated that these direct reactions are not fast enough to protect against peroxynitrite-mediated damage in vivo. Moreover, the mechanism of the reaction of peroxynitrite with LA has been recently challenged (J. Biol. Chem.279:9693-9697; 2004). Pulse radiolysis studies indicate that LA and DHLA react with peroxynitrite-derived nitrogen dioxide (*NO2) (k2 = 1.3 x 10(6) and 2.9 x 10(7) M(-1) s(-1), respectively) and carbonate radicals (CO(3-)) (k2 = 1.6 x 10(9) and 1.7 x 10(8) M(-1) s(-1), respectively). Carbonate radical-mediated oxidation of LA led to the formation of the potent one-electron oxidant LA radical cation. LA inhibited peroxynitrite-mediated nitration of tyrosine and of a hydrophobic tyrosine analog, N-t-BOC L-tyrosine tert-butyl ester (BTBE), incorporated into liposomes but enhanced tyrosine dimerization. Moreover, while LA competitively inhibited the direct oxidation of glutathione by peroxynitrite, it was poorly effective against the radical-mediated thiol oxidation. The mechanisms of reaction defined herein allow to rationalize the biochemistry of peroxynitrite based on direct and free radical-mediated processes and contribute to the understanding of the antioxidant actions of LA and DHLA. PMID:15964519

Trujillo, Madia; Folkes, Lisa; Bartesaghi, Silvina; Kalyanaraman, Balaraman; Wardman, Peter; Radi, Rafael

2005-04-05

132

Synthesis of dimeric phenol derivatives and determination of in vitro antioxidant and radical scavenging activities.  

Science.gov (United States)

In this study, di(2,6-dimethylphenol) (Di-DMP), di(2,6-diisopropylphenol) (Di-DIP, dipropofol) and di(2,6-di-t-butylphenol) (Di-DTP) were synthesized by the reaction of monomeric phenol derivatives with catalytic CuCl(OH). TMEDA and Na2S2O4. Their antioxidant capacity and radical scavenging activity were examined using different in vitro methodologies such as 1,1-diphenyl-2-picryl-hydrazyl (DPPH*) free radical scavenging, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, total antioxidant activity by ferric thiocyanate, total reducing power by potassium ferricyanide reduction method, superoxide anion radical scavenging, hydrogen peroxide scavenging and ferrous ions chelating activities. PMID:18237020

Güllçin, Ilhami; Da?tan, Arif

2007-12-01

133

Synthesis of dimeric phenol derivatives and determination of in vitro antioxidant and radical scavenging activities.  

UK PubMed Central (United Kingdom)

In this study, di(2,6-dimethylphenol) (Di-DMP), di(2,6-diisopropylphenol) (Di-DIP, dipropofol) and di(2,6-di-t-butylphenol) (Di-DTP) were synthesized by the reaction of monomeric phenol derivatives with catalytic CuCl(OH). TMEDA and Na2S2O4. Their antioxidant capacity and radical scavenging activity were examined using different in vitro methodologies such as 1,1-diphenyl-2-picryl-hydrazyl (DPPH*) free radical scavenging, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity, total antioxidant activity by ferric thiocyanate, total reducing power by potassium ferricyanide reduction method, superoxide anion radical scavenging, hydrogen peroxide scavenging and ferrous ions chelating activities.

Güllçin I; Da?tan A

2007-12-01

134

Enhancing the efficacy of photodynamic cancer therapy by radicals from plant auxin (indole-3-acetic acid).  

UK PubMed Central (United Kingdom)

Indole-3-acetic acid (plant auxin) has low toxicity but dramatically enhances the killing of mammalian cells on illuminating phenothiazinium dyes with red light. Suitable dyes include toluidine blue, used in cancer diagnosis because of localization in tumors, and methylene blue, used in experimental photodynamic therapy of cancer. The photosensitized oxidation of indole acetic acid forms a free radical that fragments in microseconds, forming reactive cytotoxins. Unlike conventional photodynamic therapy, requiring excitation of oxygen to the reactive singlet state, the treatment is effective even at the low oxygen levels common in tumors and with much lower light doses than normally used.

Folkes LK; Wardman P

2003-02-01

135

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

International Nuclear Information System (INIS)

[en] 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)

1986-01-01

136

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

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The Bcl-2 antagonist ABT-737 kills transformed cells in association with displacement of Bim from Bcl-2. The histone deactetylase (HDAC) inhibitor suberoyl bis-hydroxamic acid (SBHA) was employed to determine whether and by what mechanism ABT-737 might interact with agents that upregulate Bim. Expre...

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

137

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

Directory of Open Access Journals (Sweden)

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

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

2008-01-01

138

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

Scientific Electronic Library Online (English)

Full Text Available 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 referência para ambos radicais. As curvas cinéticas seguiram o modelo cinético de primeira ordem, e a partir destas foram calculadas as constantes de velocidad (more) e 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 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) (more) 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.

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

2008-12-01

139

Association of dopamine-related genetic loci to dopamine D3 receptor antagonist ABT-925 clinical response  

Science.gov (United States)

ABT-925, a selective dopamine D3 receptor (DRD3) antagonist, was tested in schizophrenia. A DRD3 gene polymorphism results in an S9G amino-acid change that has been associated with lower risk of schizophrenia, higher affinity for dopamine and some antipsychotics, and differential response to some antipsychotics. The effect of S9G genotype on response to ABT-925 was examined. DNA samples (N=117) were collected in a proof-of-concept, double-blind, randomized, placebo-controlled study of ABT-925 (50 or 150?mg QD) in acute exacerbation of schizophrenia. A pre-specified analysis assessed impact of genotype (SS versus SG+GG) on change from baseline to final evaluation for the Positive and Negative Syndrome Scale (PANSS) total score using analysis of covariance with genotype, treatment and genotype-by-treatment interaction as factors, and baseline score as covariate. Significant genotype-by-treatment interaction (P=0.015) was observed for change from baseline to final evaluation for the PANSS total score. Within subgroup analyses showed significant improvement from placebo in the SG+GG group treated with ABT-925 150?mg. More favorable clinical outcomes were observed in patients treated with ABT-925 150?mg who carried the DRD3 G allele than in those who carried the DRD3 SS genotype.

Bhathena, A; Wang, Y; Kraft, J B; Idler, K B; Abel, S J; Holley-Shanks, R R; Robieson, W Z; Spear, B; Redden, L; Katz, D A

2013-01-01

140

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

Science.gov (United States)

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

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

2002-03-22

 
 
 
 
141

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

UK PubMed Central (United Kingdom)

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

Sibi MP; Liu P; Ji J; Hajra S; Chen JX

2002-03-01

142

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.

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

2012-01-01

143

On the reaction of lupulones, hops ?-acids, with 1-hydroxyethyl radical.  

Science.gov (United States)

Lupulones, hops ?-acids, are one of the main constituents of the hops resin and have an important contribution to the overall bacteriostatic activity of hops during beer brewing. The use of lupulones as natural alternatives to antibiotics is increasing in the food industry and also in bioethanol production. However, lupulones are easy oxidizable and have been shown to be very reactive toward 1-hydroxyethyl radical with apparent bimolecular rate constants close to diffusion control k = 2.9 × 10(8) and 2.6 × 10(8) L mol(-1) s(-1) at 25.0 ± 0.2 °C in ethanol-water solution (10% of ethanol (v/v)) as probed by EPR and ESI-IT-MS/MS spin-trapping competitive kinetics, respectively. The free energy change for an electron-transfer mechanism is ?G° = 106 kJ/mol as calculated from the oxidation peak potential experimentally determined for lupulones (1.1 V vs NHE) by cyclic voltammetry and the reported reduction potential for 1-hydroxyethyl radical. The major reaction products identified by LC-ESI-IT-MS/MS and ultrahigh-resolution accurate mass spectrometry (orbitrap FT-MS) are hydroxylated lupulone derivatives and 1-hydroxyethyl radical adducts. The lack of pH dependence for the reaction rate constant, the calculated free energy change for electron transfer, and the main reaction products strongly suggest the prenyl side chains at the hops ?-acids as the reaction centers rather than the ?,?'-triketone moiety. PMID:23031058

de Almeida, Natália E C; do Nascimento, Eduardo S P; Cardoso, Daniel R

2012-10-12

144

On the reaction of lupulones, hops ?-acids, with 1-hydroxyethyl radical.  

UK PubMed Central (United Kingdom)

Lupulones, hops ?-acids, are one of the main constituents of the hops resin and have an important contribution to the overall bacteriostatic activity of hops during beer brewing. The use of lupulones as natural alternatives to antibiotics is increasing in the food industry and also in bioethanol production. However, lupulones are easy oxidizable and have been shown to be very reactive toward 1-hydroxyethyl radical with apparent bimolecular rate constants close to diffusion control k = 2.9 × 10(8) and 2.6 × 10(8) L mol(-1) s(-1) at 25.0 ± 0.2 °C in ethanol-water solution (10% of ethanol (v/v)) as probed by EPR and ESI-IT-MS/MS spin-trapping competitive kinetics, respectively. The free energy change for an electron-transfer mechanism is ?G° = 106 kJ/mol as calculated from the oxidation peak potential experimentally determined for lupulones (1.1 V vs NHE) by cyclic voltammetry and the reported reduction potential for 1-hydroxyethyl radical. The major reaction products identified by LC-ESI-IT-MS/MS and ultrahigh-resolution accurate mass spectrometry (orbitrap FT-MS) are hydroxylated lupulone derivatives and 1-hydroxyethyl radical adducts. The lack of pH dependence for the reaction rate constant, the calculated free energy change for electron transfer, and the main reaction products strongly suggest the prenyl side chains at the hops ?-acids as the reaction centers rather than the ?,?'-triketone moiety.

de Almeida NE; do Nascimento ES; Cardoso DR

2012-10-01

145

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

International Nuclear Information System (INIS)

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

1990-01-01

146

Formation of hydroxyl radicals on reaction of hypochlorous acid with ferrocyanide, a model iron(II) complex.  

UK PubMed Central (United Kingdom)

Hypochlorous acid reacts with the model iron(II) complex, ferrocyanide (Fe(CN)6(4-)) in aqueous solution with the rate constant 220 +/- 15 dm3 mol-1 s-1. Free hydroxyl radicals are formed in this reaction in 27% yield as shown by the hydroxylation of benzoate to give a product distribution identical to that of free (radiolytically generated) hydroxyl radicals. This reaction is three orders of magnitude faster than the analogous reaction involving hydrogen peroxide (the Fenton reaction), suggesting that the hypochlorous acid generated by activated neutrophils may be a source of hydroxyl radicals.

Candeias LP; Stratford MR; Wardman P

1994-04-01

147

Novel glycosylated mycosporine-like amino acids with radical scavenging activity from the cyanobacterium Nostoc commune.  

UK PubMed Central (United Kingdom)

Mycosporine-like amino acids (MAAs) are UV absorbing pigments, and structurally distinct MAAs have been identified in taxonomically diverse organisms. Two novel MAAs were purified from the cyanobacterium Nostoc commune, and their chemical structures were characterized. An MAA with an absorption maximum at 335 nm was identified as a pentose-bound porphyra-334 derivative with a molecular mass of 478 Da. Another identified MAA had double absorption maxima at 312 and 340 nm and a molecular mass of 1,050 Da. Its unique structure consisted of two distinct chromophores of 3-aminocyclohexen-1-one and 1,3-diaminocyclohexen and two pentose and hexose sugars. These MAAs had radical scavenging activity in vitro; the 1050-Da MAA contributed approximately 27% of the total radical scavenging activities in a water extract of N. commune. These results suggest that these glycosylated MAAs have multiple roles as a UV protectant and an antioxidant relevant to anhydrobiosis in N. commune.

Matsui K; Nazifi E; Kunita S; Wada N; Matsugo S; Sakamoto T

2011-10-01

148

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1998-12-17

149

Preclinical evaluation of antiangiogenic thrombospondin-1 peptide mimetics, ABT-526 and ABT-510, in companion dogs with naturally occurring cancers.  

UK PubMed Central (United Kingdom)

PURPOSE: The angiogenic phenotype of malignant cancers has been established as a target for cancer therapy. ABT-526 and ABT-510, two peptide mimetics of thrombospondin-1 (TSP-1), block angiogenesis in vitro and in vivo and slow tumor growth in mice. To guide the clinical development of these drugs, translational studies in dogs with naturally occurring cancers were initiated. EXPERIMENTAL DESIGN: A prospective open-label trial using ABT-510 or ABT-526 in pet dogs with measurable malignant spontaneously arising tumors. Endpoints included safety, pharmacokinetics, antitumor activity, and preliminary assessment of changes in circulating endothelial cell populations. RESULTS: Two-hundred and forty-two dogs were sequentially entered to this open-label trial. The elimination half-life for ABT-510 and ABT-526 was 0.7 and 0.8 h, respectively (range, 0.5-1 h). No dose-limiting toxicities were seen in any dogs (N = 242). Forty-two dogs receiving peptide had objective responses (>50% reduction in tumor size; n = 6) or significant disease stabilization. Most objective responses were seen after 60 days of exposure to the TSP-1 peptide. Antitumor activity was similar for both peptides and was seen in several histologies, including mammary carcinoma, head and neck carcinoma, soft tissue sarcoma, cutaneous T-cell lymphoma, and non-Hodgkin's lymphoma. Assessment of circulating endothelial cell populations in a small subset of dogs suggested that effective exposure to TSP-1 peptides may be associated with reductions in circulating endothelial cells. CONCLUSIONS: These results support the safety and activity of ABT-526 and ABT-510 in dogs with naturally occurring malignant cancers. Data from this preclinical trial support the development of TSP-1 mimetic peptides as anticancer agents.

Rusk A; McKeegan E; Haviv F; Majest S; Henkin J; Khanna C

2006-12-01

150

Is lipid peroxidation of polyunsaturated acids the only source of free radicals that induce aging and age-related diseases?  

Science.gov (United States)

The increase in free radicals is hypothesised to cause aging and age-related diseases. The most common source of free radicals is thought to be superoxide. This superoxide is claimed to be released from mitochondria during the enzymatic transformation of oxygen to water by a "leakage" process. This article presents evidence that leakage does not occur. Instead, protonated superoxide radicals are generated by lipid peroxidation processes. In nature, polyunsaturated fatty acids (PUFAs) represent particularly oxygen-sensitive compounds. Apparently, nature uses this sensitivity for signalling processes by producing lipidhydroperoxides (LOOHs) by any change to cell membrane structure. LOOHs easily undergo further enzymatic transformations to compounds which contribute to activation of genes. Bivalent metal ions within the active site of lipoxygenases catalyse LOOH production. The metal ions generate radicals which are transformed within the enzyme complex to non-radical molecules. Thus radicals never leave the enzyme complex except in severe stress situations. In this case the radical intermediates attack bonds, keeping the metal ion in its complex state. Thus, metal ions are released and react in a Fenton reaction with LOOH molecules produced earlier by lipoxygenase to form LO. radicals. Radicals are typically four orders of magnitude more reactive than non-radical molecules. Their action is not under genetic control, they attack nearly all biological molecules, destroying lipids, proteins, nucleic acids, hormones and enzymes until the radicals are quenched by scavenger molecules. The principal degradation routes are outlined in this review. Lysophospholipids are generated in large amounts after stress by activation of phospholipases and are transformed to LO. radicals. These can abstract a hydrogen radical from a lysophospholipid. The radical thus formed adds oxygen and decomposes to a 2-oxolysophospholipid and a HOO. radical (protonated superoxide). HOO. radicals in turn abstract hydrogen atoms from other molecules and produce H(2)O(2). Since any cell preparation method causes membrane destruction, it is inevitable that protonated superoxide is generated, explaining why H(2)O(2) molecules are found as "byproducts" of many reactions. PMID:20230283

Spiteller, Gerhard

2010-02-01

151

Anti-inflammatory, antiproliferative, and radical-scavenging activities of tolfenamic acid and its metal complexes.  

UK PubMed Central (United Kingdom)

Some new complexes of tolfenamic acid (=2-[(2-methyl-3-chlorophenyl)amino]benzoic acid; Htolf) with potentially interesting biological activities are described. The complexes [Mn(tolf)(2)(H(2)O)(2)], [Co(tolf)(2)(H(2)O)(2)], [Ni(tolf(2)(H(2)O)(2)], [Cu(tolf)(2)(H(2)O)](2), and [Zn(tolf)(2)(H(2)O)] were prepared by the reaction of tolfenamic acid, a potent anti-inflammatory drug, with metal salts. The radical-scavenging activities of the complexes were evaluated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging assay. Their ability to inhibit soybean lipoxygenase, beta-glucuronidase, and trypsin-induced proteolysis was studied. Their inhibitory effects on rat paw edema induced by carrageenin was studied and compared with those of tolfenamic acid. The complex [Zn(tolf)(2)(H(2)O)] exhibited the strongest in vivo inhibitory effect at 0.1 mm/kg Body Weight (BW; 93.0+/-0.9%), superior than the inhibition induced by tolfenamic acid at the same molar dose (76.0+/-0.9%). Tolfenamic acid and its metal complexes have been evaluated for antiproliferative activity in vitro against the cells of three human cancer cell lines, MCF-7 (breast cancer cell line), T24 (bladder cancer cell line), and A-549 (non-small cell lung carcinoma), and a mouse fibroblast L-929 cell line. The complexes [Mn(tolf)(2)(H(2)O)(2)] and [Cu(tolf)(2)(H(2)O)](2) have shown selectivity against T24 cell line. The IC(50) values of these two complexes against T24 cancer cell lines are in a micromolar range similar or better to that of the antitumor drug cisplatin.

Kovala-Demertzi D; Hadjipavlou-Litina D; Primikiri A; Staninska M; Kotoglou C; Demertzis MA

2009-06-01

152

New convenient approach for the synthesis of benzyl 2H-chromenones and their ?-amylase Inhibitory, ABTS.+ scavenging activities.  

Science.gov (United States)

Series of new benzyl 2H-chromenones 6a-n was synthesized by Pechmann condensation of substituted benzyl resorcinols 2a-c and 3a with various ?-ketoesters such as ethyl 3-oxobutanoate, ethyl 3-oxo-3-phenylpropanoate, ethyl 4- chloro-3-oxobutanoate, ethyl 4,4,4-trifluoro-3-oxobutanoate and ethyl 2-chloro-3-oxobutanoate 5a-e in very good yields. Synthesized compounds 6a-n were screened for their ?-amylase inhibitory, and ABTS.+ scavenging activities. In the present series of compounds, compound 8-benzyl-7-hydroxy-4-phenyl-2H-chromen-2-one 6c and 8-benzyl-7-hydroxy-4- methyl-2H-chromen-2-one 6a were most potent ABTS.+ radical scavenging and ?-amylase inhibitor. Although compound 6,8-dibenzyl-7-hydroxy-4-(trifluoromethyl)-2H-chromen-2-one 6h displayed potent ABTS.+ free radical scavenging potential, it was found poor in inhibiting pancreatic ?-amylase. PMID:23190002

Kumar, Jaladi Ashok; Tiwari, Ashok Kumar; Saidachary, Gannerla; Kumar, Domati Anand; Ali, Zehra; Sridhar, Balasubramanian; Raju, Bhimapaka China

2013-09-01

153

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

154

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

Directory of Open Access Journals (Sweden)

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

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

2013-01-01

155

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1994-04-01

156

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

International Nuclear Information System (INIS)

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

1994-01-01

157

Subcritical water extraction of phenolic compounds from pomegranate (Punica granatum L.) seed residues and investigation into their antioxidant activities with HPLC–ABTS+ assay  

UK PubMed Central (United Kingdom)

Subcritical water extraction (SWE) of phenolic compounds from pomegranate seed residues (PSR) was performed. Total phenolic content (TPC) and antioxidant capacities of the extracts obtained at different temperatures were determined, and the individual antioxidant capacities were evaluated by coupling high performance liquid chromatography with ABTS radical reaction system (HPLC–ABTS+). The results showed that the optimum extraction time was 30min, solid to water ratio was 1:40, and the highest TPC was obtained at 220°C. The effect of extraction temperature on TPC was significant (p<0.05), and TPC ranged from 651.7 to 4854.7 (mg/100g DW) between 100°C and 220°C. HPLC–ABTS+ profiles revealed that nine compounds had antioxidant activity. Furthermore, the formation of Maillard reaction products during SWE was investigated, and the content of 5-hydroxymethylfurfural (5-HMF) was determined. The comparative study indicated that SWE was a promising technique for preparation of PSR phenolics.

He L; Zhang X; Xu H; Xu C; Yuan F; Knez Ž; Novak Z; Gao Y

2012-04-01

158

Water soluble and heat resistant polymers by free radical polymerization of lactic acid-based monomers  

Science.gov (United States)

Tactic heat resistant polymer was prepared by free radical polymerization of lactic acid-based monomers, i.e. chiral 2-isopropyl-5-methylene-1,3-dioxolan-4-ones (1). The polymerization of 1 proceeded smoothly without ring-opening to give a polymer with high isotacticity (mm) of 29.7~100% and glass transition temperature (Tg) of 172~213°C. 1 also showed high reactivity in the copolymerization with styrene and methyl methacrylate, and the incorporation of 1 unit in the copolymer structure increased Tg of each polymer. In addition, hydrolysis of poly(1) produced a new type of water soluble poly(lactic acid), i.e. poly(?-hydroxy acrylate), and poly(?-hydroxy acrylate-co-divinyl benzene) hydrogel absorbed water as high as 1000 times of the original polymer weight.

Tanaka, Hitoshi; Kibayashi, Tatsuya; Niwa, Miki

2013-08-01

159

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

Science.gov (United States)

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

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

2013-01-01

160

The influence of repulsive electrostatic forces on the lifetimes of poly(acrylic acid) radicals in aqueous solution  

Energy Technology Data Exchange (ETDEWEB)

Poly(acrylic acid) derived carbon-centered radicals were generated either radiolytically or photolytically in deoxygenated aqueous solutions and their decay observed by photometry or EPR. Reaction kinetics strongly depends on electrostatic forces as proved during studies of pH function. The electrostatic forces influences also the rate of intermolecular H-abstraction reactions. Half-lifes of corresponding peroxyl radicals, although also strongly influenced by degree of dissociation of polyelectrolyte, do not reach such high enhancement values. This is interpreted as being due to longer encounter distance in the case of peroxyl radicals. (author). 31 refs, 6 figs, 1 tab.

Ulanski, P.; Rosiak, J.M. [Institute of Applied Radiation Chemistry, Technical University of Lodz, Lodz (Poland); Bothe, E.; Hildenbrand, K.; Sonntag, C. von [Max-Planck-Institut fuer Strahlenchemie, Muelheim an der Ruhr (Germany)

1997-12-31

 
 
 
 
161

The influence of repulsive electrostatic forces on the lifetimes of poly(acrylic acid) radicals in aqueous solution  

International Nuclear Information System (INIS)

Poly(acrylic acid) derived carbon-centered radicals were generated either radiolytically or photolytically in deoxygenated aqueous solutions and their decay observed by photometry or EPR. Reaction kinetics strongly depends on electrostatic forces as proved during studies of pH function. The electrostatic forces influences also the rate of intermolecular H-abstraction reactions. Half-lifes of corresponding peroxyl radicals, although also strongly influenced by degree of dissociation of polyelectrolyte, do not reach such high enhancement values. This is interpreted as being due to longer encounter distance in the case of peroxyl radicals. (author).

1997-01-01

162

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

UK PubMed Central (United Kingdom)

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

Porter NA

2013-04-01

163

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

Science.gov (United States)

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

Porter, Ned A

2013-04-09

164

Characterization of radical intermediates in laccase-mediator systems. A multifrequency EPR, ENDOR and DFT/PCM investigation.  

UK PubMed Central (United Kingdom)

Suitable low molecular-weight compounds, called mediators, can be used in combination with the phenol-oxidase enzyme laccase to indirectly oxidize large organic substrates, such as environmental pollutants, which are not laccase natural substrates. The oxidation of two different synthetic redox mediators, violuric acid (VIO) and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) has been studied under catalysis of two laccases from white-rot fungi (Trametes versicolor and Pleurotus ostreatus). VIO was selected as a prototype of the -NOH type of mediators and compared to ABTS, a well-known two-step redox system. To characterize the radical intermediates formed from both mediators after the enzymatic oxidation, a multifrequency EPR approach has been adopted. The radical species have been investigated employing 9.4 GHz (X-band), 34 GHz (Q-band) and 244 GHz (high field) EPR and pulse electron nuclear double resonance (ENDOR) techniques. Theoretical calculations based on density functional theory (DFT/PCM) have been performed to support and further interpret the experimental EPR and ENDOR data. This integrated approach allowed us to obtain a complete characterization of both radicals and to elucidate the type of the radical state (neutral or cationic).

Brogioni B; Biglino D; Sinicropi A; Reijerse EJ; Giardina P; Sannia G; Lubitz W; Basosi R; Pogni R

2008-12-01

165

Characterization of radical intermediates in laccase-mediator systems. A multifrequency EPR, ENDOR and DFT/PCM investigation.  

Science.gov (United States)

Suitable low molecular-weight compounds, called mediators, can be used in combination with the phenol-oxidase enzyme laccase to indirectly oxidize large organic substrates, such as environmental pollutants, which are not laccase natural substrates. The oxidation of two different synthetic redox mediators, violuric acid (VIO) and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) has been studied under catalysis of two laccases from white-rot fungi (Trametes versicolor and Pleurotus ostreatus). VIO was selected as a prototype of the -NOH type of mediators and compared to ABTS, a well-known two-step redox system. To characterize the radical intermediates formed from both mediators after the enzymatic oxidation, a multifrequency EPR approach has been adopted. The radical species have been investigated employing 9.4 GHz (X-band), 34 GHz (Q-band) and 244 GHz (high field) EPR and pulse electron nuclear double resonance (ENDOR) techniques. Theoretical calculations based on density functional theory (DFT/PCM) have been performed to support and further interpret the experimental EPR and ENDOR data. This integrated approach allowed us to obtain a complete characterization of both radicals and to elucidate the type of the radical state (neutral or cationic). PMID:19060974

Brogioni, Barbara; Biglino, Daniele; Sinicropi, Adalgisa; Reijerse, Edward J; Giardina, Paola; Sannia, Giovanni; Lubitz, Wolfgang; Basosi, Riccardo; Pogni, Rebecca

2008-10-27

166

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

UK PubMed Central (United Kingdom)

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.

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

2012-01-01

167

Identification of the radicals formed in the reactions of some endogenous photosensitizers with oleic acid under the UVA irradiation.  

Science.gov (United States)

Electron spin resonance measurements were performed for the reactions of some endogenous photosensitizers (flavin mononucleotide or flavin adenine dinucleotide or folic acid or ?-nicotinamide adenine dinucleotide or ?-nicotinamide adenine dinucleotide phosphate or pyridoxal-5'-phosphate or urocanic acid) with oleic acid under the ultraviolet light A irradiation using ?-(4-pyridyl-1-oxide)-N-tert-butylnitrone as a spin trap reagent. Of the endogenous photosensitizers, prominent electron spin resonance signals (?(N) = 1.58 mT and ?(H)? = 0.26 mT) were observed for the reaction mixture of flavin mononucleotide (or flavin adenine dinucleotide or folic acid), suggesting that radical species form in the reaction mixtures. Singlet oxygen seems to participate in the formation of the radicals because the electron spin resonance peak heights increased for the reactions in D(2)O to a great extent. A high performance liquid chromatography-electron spin resonance-mass spectrometry was employed to identify the radicals formed in the reactions of the endogenous photosensitizers (flavin mononucleotide or flavin adenine dinucleotide or folic acid) with oleic acid under the ultraviolet light A irradiation. The high performance liquid chromatography-electron spin resonance-mass spectrometry analyses showed that 7-carboxyheptyl and 1-(3-carboxypropyl)-4-hydroxybutyl radicals form in the reaction mixture of flavin mononucleotide (or flavin adenine dinucleotide or folic acid). PMID:23170043

Mori, Hiroko; Iwahashi, Hideo

2012-07-11

168

Identification of the radicals formed in the reactions of some endogenous photosensitizers with oleic acid under the UVA irradiation.  

UK PubMed Central (United Kingdom)

Electron spin resonance measurements were performed for the reactions of some endogenous photosensitizers (flavin mononucleotide or flavin adenine dinucleotide or folic acid or ?-nicotinamide adenine dinucleotide or ?-nicotinamide adenine dinucleotide phosphate or pyridoxal-5'-phosphate or urocanic acid) with oleic acid under the ultraviolet light A irradiation using ?-(4-pyridyl-1-oxide)-N-tert-butylnitrone as a spin trap reagent. Of the endogenous photosensitizers, prominent electron spin resonance signals (?(N) = 1.58 mT and ?(H)? = 0.26 mT) were observed for the reaction mixture of flavin mononucleotide (or flavin adenine dinucleotide or folic acid), suggesting that radical species form in the reaction mixtures. Singlet oxygen seems to participate in the formation of the radicals because the electron spin resonance peak heights increased for the reactions in D(2)O to a great extent. A high performance liquid chromatography-electron spin resonance-mass spectrometry was employed to identify the radicals formed in the reactions of the endogenous photosensitizers (flavin mononucleotide or flavin adenine dinucleotide or folic acid) with oleic acid under the ultraviolet light A irradiation. The high performance liquid chromatography-electron spin resonance-mass spectrometry analyses showed that 7-carboxyheptyl and 1-(3-carboxypropyl)-4-hydroxybutyl radicals form in the reaction mixture of flavin mononucleotide (or flavin adenine dinucleotide or folic acid).

Mori H; Iwahashi H

2012-11-01

169

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

1987-04-23

170

The antioxidant activity and free radical-scavenging capacity of dietary phenolic extracts from horse gram (Macrotyloma uniflorum (Lam.) Verdc.) seeds  

UK PubMed Central (United Kingdom)

Total phenolics and the antioxidative properties of two varieties of horse gram (Macrotyloma uniflorum) were studied. The raw and dry-heated seed samples were extracted successively with methanol and 70% acetone separately. After removing the solvents, the extracts were freeze-dried. The black seeds contained relatively high levels of total phenolics and tannins than the brown seeds with respect to the treatments and solvents extraction. The extracts were subjected to assess their potential antioxidant activities using systems such as ?,?-diphenyl-?-picrylhydrazyl (DPPH.), ABTS.+, FRAP, linoleic acid emulsion, superoxide radicals and OH. The superoxide anion radical-scavenging activity was found to be higher in 70% acetone extract of the both raw and dry heated seeds of the respective varieties at the concentration of 600 ?g in the reaction mixture. The DPPH radical and ABTS cation radical-scavenging activities were well proved and related with the ferric-reducing/antioxidant capacity of the extracts. Interestingly, among the various extracts, 70% acetone extracts of dry-heated samples of brown variety, and raw and dry-heated samples of black variety showed significantly (P < 0.05) higher hydroxyl radical-scavenging activity. In general, all extracts exhibited good antioxidant activity (53.3-73.1%) against the linoleic acid emulsion system but were significantly (P < 0.05) lower than the synthetic antioxidant, BHA (93.3%).

Siddhuraju P; Manian. S.

2007-01-01

171

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

Directory of Open Access Journals (Sweden)

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

B.T. Aluko; O.I. Oloyede; A.J. Afolayan

2013-01-01

172

Interaction of retinoic acid radical cation with lysozyme and antioxidants: laser flash photolysis study in microemulsion.  

Science.gov (United States)

All-trans retinoic acid (ATRA) plays essential roles in the normal biological processes and the treatment of cancer and skin diseases. Considering its photosensitive property, many studies have been focused on the photochemistry of ATRA. In this study, we investigated the transient phenomena in the laser flash photolysis (LFP) of ATRA in microemulsion to further understand the photochemistry of ATRA. Results show that 355 nm LFP of ATRA in both acidic and alkaline conditions leads to the generation of retinoic acid cation radicals (ATRA(•+)) via biphotonic processes. The employment of microemulsion system allows us to investigate the reaction of hydrophobic ATRA(•+) with molecules of different polarity. Therefore, we studied the reaction activity of ATRA(•+) to many hydrophobic and hydrophilic molecules. Results show that ATRA(•+) can efficiently interact with lysozyme, tyrosine, tryptophan and many antioxidants, such as curcumin (Cur), vitamin C (VC) and gallic acid (GA). The apparent rate constants of these reactions were measured and compared. These findings suggest that ATRA(•+) is a reactive transient product which may pose damage to lysozyme, and antioxidants, such as Cur, VC and GA, may inactivate ATRA(•+) by efficient quenching reactions. PMID:23819830

Li, Kun; Wang, Mei; Wang, Ting; Sun, Dongmei; Zhu, Rongrong; Sun, Xiaoyu; Wu, Xianzheng; Wang, Shi-Long

2013-08-17

173

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

The homolysis of peracetic acid (PAA) as a relevant source of free radicals (e.g., •OH) was studied in detail. Radicals formed as a result of chain radical reactions were detected with electron spin resonance and nuclear magnetic resonance spin trapping techniques and subsequently identified by mean...

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

174

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)

[en] 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)

2008-01-01

175

The atmospheric degradation reaction of dehydroabietic acid (DHAA) initiated by OH radicals and O3.  

UK PubMed Central (United Kingdom)

Dehydroabietic acid (DHAA) is the major marker compound emitted from the burning of conifer. In this paper, the atmospheric mechanism of DHAA initiated by OH radicals and O3 was studied at the MPWB1K/6-31+G(d,p)//MPWB1K/6-311+G(3df,2p) level. For OH radicals, two types of reactions including OH addition and hydrogen abstraction were investigated. The cycloaddition reactions of O3 were considered. The rate constants over the temperature range of 200-400 K were calculated with the Rice-Ramsperger-Kassel-Marcus (RRKM) theory. At 298 K and under the pressure of 760 Torr, the whole rate constants are 0.89×10(-11) cm(3) molecule(-1) s(-1) and 2.29×10(-20) cm(3) molecule(-1) s(-1) for DHAA+OH and DHAA+O3, respectively. This study can be regarded as an attempt to investigate the OH-initiated and O3-initiated photochemical reaction mechanisms of DHAA in the atmosphere.

Bai J; Sun X; Zhang C; Zhao Y; Gong C

2013-08-01

176

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

International Nuclear Information System (INIS)

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

2011-01-01

177

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-06-15

178

Prospective study of thrombospondin-1 mimetic peptides, ABT-510 and ABT-898, in dogs with soft tissue sarcoma.  

UK PubMed Central (United Kingdom)

BACKGROUND: Exposure to anti-angiogenic thrombospondin-1 (TSP-1) mimetic peptides (MPs) has resulted in sporadic anti-tumor activity in humans and dogs. HYPOTHESIS: Novel TSP-1 MPs formulations will be safe, tolerated, and clinically active in soft tissue sarcoma (STS) in dogs. ANIMALS: Sixty-two client-owned dogs with measurable STS were enrolled, excluding hemangiosarcoma. METHODS: A prospective, single agent, multicenter, open-label study assessing ABT-510 bolus, ABT-898 bolus, or ABT-898 depot formulations of TSP-1 in dogs. Endpoints included tolerability, antitumor activity, and the assessment of ability of clinical covariates and circulating endothelial cells (CEC) concentration to predict tumor response. RESULTS: Two non-dose-limiting toxicoses possibly attributed to treatment were observed (keratitis and osteoarthritis). Antitumor activity (10/44 = 23% responses) was observed in study subjects who received treatment for >28 days (n = 44) including both partial (7) and minimal responses (3). Responses were disproportionately seen in dogs receiving ABT-898 formulations (9/28 = 32%) versus those receiving ABT-510 (1/16 = 6%; P < .045). Disease stabilization for >84 days was also documented (8/44 = 18%). Slow rates of tumor progression before study entry correlated with anti-tumor activity in treated dogs, whereas no significant association was found between changes in total CEC concentration and tumor response (P = .28) or time to progression (P = .42). CONCLUSIONS AND CLINICAL IMPORTANCE: Safely achieved antitumor activity was documented with TSP-1 MPs in dogs with STS. The most notable activity was achieved with the ABT-898 formulations.

Sahora AI; Rusk AW; Henkin J; McKeegan EM; Shi Y; Khanna C

2012-09-01

179

New hyaluronic acid based brush copolymers synthesized by atom transfer radical polymerization.  

UK PubMed Central (United Kingdom)

In this work, an efficient method for the synthesis of hyaluronic acid based brush copolymers using atom transfer radical polymerization (ATRP) has been reported. At first, two different hyaluronic acid (HA) based macroinitiators have been prepared and then they have been used for the polymerization via ATRP of hydrophilic or hydrophobic molecules carrying vinyl portions. In particular, by linking 2-bromo-2-methylpropionic acid (BMP) to the primary hydroxyl groups of tetrabutyl ammonium salt of HA (HA-TBA) or to amino groups of the ethylenediamino derivative of HA-TBA (HA-TBA-EDA), two macroinitiators (HA-TBA-BMP and HA-TBA-EDA-BMP) have been obtained. Then they have been used for the ATRP of poly(ethylene glycol) methacrylate (PEGMA), butyl methacrylate (BUTMA) or N-isopropylacrylamide (NIPAM) using a complex of Cu(I) and 2,2'-Bipyridyl (Bpy), as a catalyst. Both macroinitiators and final copolymers, named as HA-BMP-pPEGMA, HA-BMP-pBUTMA, HA-BMP-pNIPAM, HA-EDA-BMP-pPEGMA, HA-EDA-BMP-pBUTMA and HA-EDA-BMP-pNIPAM, have been characterized by spectroscopic analysis and size exclusion chromatography to confirm the success of the polymerization process.

Pitarresi G; Fiorica C; Licciardi M; Palumbo FS; Giammona G

2013-02-01

180

The BH3-mimetic ABT-737 inhibits allogeneic immune responses.  

UK PubMed Central (United Kingdom)

Apoptosis controls the adaptive immune system through regulation of central and peripheral lymphocyte deletion. Therefore, substances that selectively interact with the intrinsic apoptosis pathway in lymphocytes offer unexplored opportunities to pharmacologically modulate the immune response. Here, we present evidence that the BH3-mimetic ABT-737 suppresses allogeneic immune responses. In vitro, ABT-737 prevented allogeneic T-cell activation, proliferation, and cytotoxicity by apoptosis induction, but without impairing the physiological functions of remaining viable T cells. In vivo, ABT-737 was highly selective for lymphoid cells and inhibited allogeneic T- and B-cell responses after skin transplantation. The immunosuppressive effect of ABT-737 was markedly increased in combination with low-dose cyclosporine A, as shown by the induction of long-term skin graft survival without significant inflammatory infiltrates in 50% of the recipients in an MHC class I single antigen mismatched model. Thus, pharmacological targeting of Bcl-2 proteins represents a novel immunosuppressive approach to prevent rejection of solid organ allografts.

Cippà PE; Kraus AK; Edenhofer I; Segerer S; Chen J; Hausmann M; Liu Y; Guimezanes A; Bardwell PD; Wüthrich RP; Fehr T

2011-07-01

 
 
 
 
181

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

Directory of Open Access Journals (Sweden)

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

Yoshinori Kadoma; Seiichiro Fujisawa

2012-01-01

182

Combination treatments with ABT-263 and an immunotoxin produce synergistic killing of ABT-263-resistant small cell lung cancer cell lines.  

UK PubMed Central (United Kingdom)

Synergistic killing was achieved when Small Cell Lung Cancer (SCLC) cell lines were incubated with ABT-263 and an immunotoxin directed to the transferrin receptor. SCLC lines are variably sensitive to the BH-3 only peptide mimetic, ABT-263. To determine their sensitivity to toxin-based reagents, we incubated four representative SCLC lines with a model Pseudomonas exotoxin-based immunotoxin directed to the transferrin receptor. Remarkably in 4-of-4 lines, there was little evidence of immunotoxin-mediated cytotoxicity despite near complete inhibition of protein synthesis. However, when combinations of ABT-263 and immunotoxin were added to the ABT-263-resistant cell lines (H196 and H69AR), there was synergistic killing as evidenced by increased activation of caspase 3/7, annexin V staining, and loss of cell integrity. Synergistic killing was evident at 6 hr and correlated with loss of Mcl-1. This synergy was also noted when the closely related compound ABT-737 was combined with the same immunotoxin. To establish that the synergy seen in tissue culture could be achieved in vivo, H69AR cells were grown as tumors in nude mice and shown to be susceptible to the killing action of an immunotoxin-ABT-737 combination but not to either agent alone. When immunotoxin-ABT combinations were added to ABT-263-sensitive lines (H146 and H1417), killing was additive. Our data support combination approaches for treating ABT-263-resistant SCLC with ABT-263 and a second agent that provides synergistic killing action.

Mattoo AR; FitzGerald DJ

2013-02-01

183

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

Directory of Open Access Journals (Sweden)

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

G. L. FREITAS; E. M. KUSKOSKI; L. GONZAGA; R. FETT

2009-01-01

184

Activities of ABT-773 against Listeria monocytogenes and Coryneform Bacteria of Clinical Interest  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The in vitro activities of ABT-773 were evaluated against 15 Listeria monocytogenes strains and 196 coryneform bacteria isolated from clinical samples. One hundred percent of the L. monocytogenes strains were inhibited by ?0.015 ?g of ABT-773/ml. MICs of ABT-773 (?g/ml) at which 50% of the isolates ...

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

185

Free radical intermediates in the oxidation of flavone-8-acetic acid: possible involvement in its antitumour activity.  

UK PubMed Central (United Kingdom)

The sulphate radical (SO4.-), a model one-electron oxidant, reacts with the antitumour drug flavone-8-acetic acid (FFA) with the rate constant 9.1 x 10(8) dm3mol-1s-1 to yield an uncharged radical that reacts with oxygen (k approximately 1 x 10(9) dm3mol-1s-1). The oxidation of FAA by SO4.- in a steady-state system was found to release carbon dioxide with a yield of 96% relative to that of the SO.4-. The results are interpreted by fast (t1/2 < or = 1 microsecond) and efficient decarboxylation of the FAA radical cation, resulting in a carbon-centred radical. The reaction of the latter with oxygen is a possible source of radical-driven cytotoxic pathways, such as singlet oxygen formation via the Russell mechanism or H-abstraction from lipids. On the basis of the observations in the model system, a possible free radical mechanism for the antitumour action of the drug is suggested.

Candeias LP; Everett SA; Wardman P

1993-10-01

186

On the origin of the methyl radical loss from deprotonated ferulic and isoferulic acids: electronic excitation of a transient structure.  

UK PubMed Central (United Kingdom)

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

Zhang X; Li F; Lv H; Wu Y; Bian G; Jiang K

2013-06-01

187

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

UK PubMed Central (United Kingdom)

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

Narici L; Paci M; Brunetti V; Rinaldi A; Sannita WG; De Martino A

2012-08-01

188

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

Science.gov (United States)

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

Schütze, M.; Herrmann, H.

189

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 reaction

1998-01-01

190

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

International Nuclear Information System (INIS)

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

1991-01-01

191

Synthesis, antielastase, antioxidant and radical scavenging activities of 4-(aza substituted) methylene substituted dihydroxy coumarines.  

UK PubMed Central (United Kingdom)

A series of some 4-(aza substituted) methylene substituted dihydroxy coumarines were evaluated for their antioxidant and antielastase activities. Different in vitro methodologies such as total reducing power, 1,1-diphenyl-2-picryl-hydrazil (DPPH·) free radical scavenging, ABTS radical scavenging activity were used as antioxidant activity. All the tested compounds exhibited potent free radical scavenging ability and antielastase activites.

Sokmen BB; Aydin G; Gumus A; Karadeniz S; Ugras HI; Yanardag R; Cak?r U

2013-08-01

192

Hydroxyl radical induced oxidation of acetylene in oxygenated aqueous solution. The formation of a highly acidic intermediate  

International Nuclear Information System (INIS)

[en] Pulsed irradiation was used in a study of the action of 2.8 MeV electron pulses on aqueous solutions containing an acetylene-oxygen mixture or an acetylene-oxygen-nitrous oxide mixture in order to investigate the reactions of the beta-hydroxy-vinyl-peroxyl radical. This radical is formed from acetylene by reaction with OH followed by addition of molecular oxygen. The results show that a highly acidic intermediate is formed with a pK value of greater or equal to 2. The decay of this intermediate leads to the observed products. 6 references, 2 figures, 1 table

1981-01-01

193

In vitro free radical scavenging activity of hepatic metallothionein induced in an Indian freshwater fish, Channa punctata Bloch.  

UK PubMed Central (United Kingdom)

Mammalian metallothioneins (MT) have been reported to scavenge free radicals. There is no experimental evidence to show that fish MT has a similar property. In the present study cadmium-induced MT (Cd-MT) from the liver of an Indian freshwater fish Channa punctata Bloch was investigated for its free radical scavenging activity using three different in vitro assays. Exposure to cadmium chloride (0.2 mg/kg body weight; three doses on alternate days) resulted in a marked induction of Cd-MT in liver. Only a single isoform of Cd-MT was found to be induced. Molecular weight of Cd-MT was found to be 14 kDa as deduced by SDS-PAGE analysis. The purified Cd-MT effectively scavenged the following free radicals: superoxide radical (O2*-), 2,2'-azinobis 3-ethylbenzothiazoline-6-sulfonic acid (ABTS*+) and 1,1-diphenyl-picrylhydrazyl radical (DPPH*). The radical scavenging effect was found to be concentration-dependent. Also, the purified MT exhibited an inhibitory effect on ferric nitrilotriacetate (Fe-NTA) induced oxidative DNA damage in vitro. The cysteine residues of MT are proposed to be the main candidate for its radical scavenging activity. Findings of the present study strongly suggest a free radical scavenging role for fish MT. Present study adds to the little existing knowledge about fish MT and its possible biological functions.

Atif F; Kaur M; Yousuf S; Raisuddin S

2006-08-01

194

Reactions of radiation-produced free radicals with copper-amino acid complexes and related compounds in aqueous solution  

Energy Technology Data Exchange (ETDEWEB)

Reactions of oxidizing free radicals, generated by radiation-chemical techniques, with some copper compounds in aqueous systems have been investigated. In the case of copper-amino acid complexes, it is concluded that OH radical attack occurs both on the metal and the ligand, giving respectively a Cu(III) species and ligand radical. The reaction of the aqua Cu(I) ion with H/sub 2/O/sub 2/, either formed by radiation as the molecular yield or added directly before irradiation, was studied in irradiated copper-methanol systems. It was found that, in the absence of an organic scavenger, Cu(III), produced by the reaction of OH with the aqua Cu(II) ion, reacts with itself to give H/sub 2/O/sub 2/ or reacts with H/sub 2/O/sub 2/ to give O/sub 2/. The kinetics of these competing reactions have been investigated. In experiments aimed at obtaining information about the catalysis of O/sub 2//sup /minus// dismutation by copper ions, the H/sub 2/O/sub 2/ yields from irradiated solutions of HCOO/sup /minus// + aquaCu(II) + O/sub 2/ were measured as a function of radiation dose. In similar experiments, but with the Cu(II) complexed with alanine, the H/sub 2/O/sub 2/ yield passed through a maximum then decreased with increasing dose. Deamination of the ligand coincided with the decrease in H/sub 2/O/sub 2/ concentration. The reactions of OH radicals with Ni(II)(glycine)/sub 2/ complexes were studied for comparison with Cu(II)-amion acid systems. It is concluded that, in the Ni(II) system, the OH radical attack is mainly on the metal and the ligand radical is formed by electron transfer from the ligand to the metal.

Saadalla-Nazhat, R.A.

1987-01-01

195

Structure and radical scavenging activity relationships of pyrolytic lignins.  

UK PubMed Central (United Kingdom)

This work deals with antioxidant properties of pyrolytic lignins against two free radicals, 1,1-diphenyl-2-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid). Pyrolytic lignins produced by the thermal pyrolysis of the Etek lignin were extracted from the liquid pyrolysis product and fractionated using solvents of different polarities. The main functional groups linked to the lignin skeleton have been characterized by (1)H NMR and (19)F NMR upon acetylation and trifluoromethylation, respectively. Their radical scavenging activity against targeted free radicals was evaluated in vitro, and it was correlated to the content of studied functional groups. In contrast to the extracted Etek lignin, thermal pyrolysis produces lignin adducts that have higher scavenging efficacy than the nonthermally altered lignin and even higher than that of quercetin, a well-known phenolic antioxidant. The phenyl hydroxyl and methoxyl groups appear to be the main lignin structural factors contributing to the overall scavenging properties against the DPPH and ABTS free radicals. Also, these results show that there is no correlation between the content of aliphatic hydroxyl and carbonyl groups and the antioxidant activity.

Nsimba RY; West N; Boateng AA

2012-12-01

196

Free radical scavenging activity of Kielmeyera variabilis (Clusiaceae).  

UK PubMed Central (United Kingdom)

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.

Coqueiro A; Regasini LO; Skrzek SC; Queiroz MM; Silva DH; da Silva Bolzani V

2013-01-01

197

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

2013-02-19

198

Free Radical Scavenging Activity of Kielmeyera variabilis (Clusiaceae)  

Directory of Open Access Journals (Sweden)

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

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

2013-01-01

199

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

International Nuclear Information System (INIS)

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

2006-11-21

200

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

UK PubMed Central (United Kingdom)

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.

González-Perilli L; Álvarez MN; Prolo C; Radi R; Rubbo H; Trostchansky A

2013-05-01

 
 
 
 
201

Linoleic acid peroxidation vs. isomerization: a biomimetic model of free radical reactivity in the presence of thiols.  

UK PubMed Central (United Kingdom)

Biomimetic models of free radical-induced transformation of polyunsaturated fatty acids, such as micelles and liposomes, have been used for the study of lipid peroxidation and lipid isomerization. Free radical reactivity of thiol compounds is the common link between the two processes, since lipid peroxidation is inhibited by thiols, due to their H-donation ability, whereas lipid isomerization is catalysed by S-centered radicals. In this paper the two processes are compared for the first time, in solution and under biomimetic conditions, demonstrating that hydroperoxides and trans lipids are formed to comparable extents as a result of oxidative free radical conditions. The biomimetic model of micelles of linoleic acid, prepared by addition of a non-ionic surfactant (TWEEN(®)-20) and 2-mercaptoethanol as the amphiphilic thiol, was irradiated by ionizing radiation up to 400 Gy under various conditions. In air-equilibrated solutions, the cis-trans isomerization process was observed with a catalytic cycle of 370 together with a substantial amount of hydroperoxides (LOOH). The effect of micelle size was also studied in order to envisage the effect of the supramolecular organization on the outcome of the two processes, and in particular, for the positional preference of the double bond isomerization.

Mihaljevi? B; Tartaro I; Ferreri C; Chatgilialoglu C

2011-05-01

202

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

Directory of Open Access Journals (Sweden)

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

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

2010-01-01

203

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 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, açaí, araçá-boi, bacaba, bacuri, buriti, cajá, cajarana, caju, cupuaçu, graviola, murici, noni e tamarindo). A atividade de radicais livres foi avaliada pelo m (more) étodo 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, buriti, cajá, cajarana, caju, cupuaçu, graviola, murici, noni e tamarindo). The free radical scavenger activity was evaluated by the ABTS assay. Some pulps presented high ant (more) ioxidant 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.

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

2010-12-01

204

Formation and reactivity of pyridylperoxyl radicals in solution  

Energy Technology Data Exchange (ETDEWEB)

2-Pyridyl radicals were produced by the reaction of 2-chloro- or 2-bromopyridine with solvated electrons (k approximately 10{sup 10} L mol{sup -1} s{sup -1}) and reacted rapidly with oxygen (k = 2.2 x 10{sup 9} L mol{sup -1} s{sup -1}) to produce the 2-pyridylperoxyl radical. This radical exhibits optical absorption in the visible range, with {lambda}{sub max} at 440 nm. 2-Pyridylperoxyl radical is a fairly strong oxidant, which reacts with 2,2`-azinobis(3-ethylbenzothiazoline-6-sulfonate ion) (ABTS), chlorpromazine, and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox C) by one-electron oxidation. The rate constants k for these reactions, determined from the rate of formation of the one-electron oxidation as a function of substrate concentration, vary between 2 x 10{sup 6} and 2 x 10{sup 9} L mol{sup -1} s{sup -1} in various mixtures. For each substrate, a good correlation was found between log k and the cohesive pressure of the solvent or solvent mixture, as found before for CCI{sub 3}O{sub 2} radical reactions in nearly neat solvents. 3-Bromo, 3-chloro- and 4-chloropyridine also reacted rapidly with solvated electrons, but their radical anions underwent protonation on the nitrogen in competition with the dehalogenation process. Therefore, no pyridylperoxyl radicals were formed from these species in aqueous solutions and only partial yield was found in neat methanol. 20 refs., 4 figs., 1 tab.

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

1995-03-30

205

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

International Nuclear Information System (INIS)

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

1977-01-01

206

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.

Hülya Torun; Faik Ahmet Ayaz; Nesrin Colak; Ji?í Grúz; Miroslav Strnad

2013-01-01

207

Thrombospondin-1 (TSP-1) analogs ABT-510 and ABT-898 inhibit prolactinoma growth and recover active pituitary transforming growth factor-?1 (TGF-?1).  

Science.gov (United States)

Prolactinomas are the most prevalent type of secreting pituitary tumors in humans and generally respond well to a medical therapy with dopamine agonists. However, for patients exhibiting resistance to dopaminergic drugs, alternative treatments are desired. Antiangiogenic strategies might represent a potential therapy for these tumors. Thrombospondin 1 (TSP-1) is a large multifunctional glycoprotein involved in multiple biological processes including angiogenesis, apoptosis, and activation of TGF-?1. Because tumors that overexpress TSP-1 grow more slowly, have fewer metastases, and have decreased angiogenesis, TSP-1 provides a novel target for cancer treatment. ABT-510 and ABT-898 are TSP-1 synthetic analogs that mimic its antiangiogenic action. In the present study, we explored the potential effect of ABT-510 and ABT-898 on experimental prolactinomas induced by chronic diethylstilbestrol (DES) treatment in female rats. We demonstrated that a 2-wk treatment with ABT-510 and ABT-898 counteracted the increase in pituitary size and serum prolactin levels as well as the pituitary proliferation rate induced by DES. These inhibitory effects on tumor growth could be mediated by the antiangiogenic properties of the drugs. We also demonstrated that ABT-510 and ABT-898, in addition to their described antiangiogenic effects, increased active TGF-?1 level in the tumors. We postulate that the recovery of the local cytokine activation participates in the inhibition of lactotrope function. These results place these synthetic TSP-1 analogs as potential alternative or complementary treatments in dopamine agonist-resistant prolactinomas. PMID:22700773

Recouvreux, M Victoria; Camilletti, M Andrea; Rifkin, Daniel B; Becu-Villalobos, Damasia; Díaz-Torga, Graciela

2012-06-14

208

Thrombospondin-1 (TSP-1) analogs ABT-510 and ABT-898 inhibit prolactinoma growth and recover active pituitary transforming growth factor-?1 (TGF-?1).  

UK PubMed Central (United Kingdom)

Prolactinomas are the most prevalent type of secreting pituitary tumors in humans and generally respond well to a medical therapy with dopamine agonists. However, for patients exhibiting resistance to dopaminergic drugs, alternative treatments are desired. Antiangiogenic strategies might represent a potential therapy for these tumors. Thrombospondin 1 (TSP-1) is a large multifunctional glycoprotein involved in multiple biological processes including angiogenesis, apoptosis, and activation of TGF-?1. Because tumors that overexpress TSP-1 grow more slowly, have fewer metastases, and have decreased angiogenesis, TSP-1 provides a novel target for cancer treatment. ABT-510 and ABT-898 are TSP-1 synthetic analogs that mimic its antiangiogenic action. In the present study, we explored the potential effect of ABT-510 and ABT-898 on experimental prolactinomas induced by chronic diethylstilbestrol (DES) treatment in female rats. We demonstrated that a 2-wk treatment with ABT-510 and ABT-898 counteracted the increase in pituitary size and serum prolactin levels as well as the pituitary proliferation rate induced by DES. These inhibitory effects on tumor growth could be mediated by the antiangiogenic properties of the drugs. We also demonstrated that ABT-510 and ABT-898, in addition to their described antiangiogenic effects, increased active TGF-?1 level in the tumors. We postulate that the recovery of the local cytokine activation participates in the inhibition of lactotrope function. These results place these synthetic TSP-1 analogs as potential alternative or complementary treatments in dopamine agonist-resistant prolactinomas.

Recouvreux MV; Camilletti MA; Rifkin DB; Becu-Villalobos D; Díaz-Torga G

2012-08-01

209

Thrombospondin-1 (TSP-1) Analogs ABT-510 and ABT-898 Inhibit Prolactinoma Growth and Recover Active Pituitary Transforming Growth Factor-?1 (TGF-?1)  

Science.gov (United States)

Prolactinomas are the most prevalent type of secreting pituitary tumors in humans and generally respond well to a medical therapy with dopamine agonists. However, for patients exhibiting resistance to dopaminergic drugs, alternative treatments are desired. Antiangiogenic strategies might represent a potential therapy for these tumors. Thrombospondin 1 (TSP-1) is a large multifunctional glycoprotein involved in multiple biological processes including angiogenesis, apoptosis, and activation of TGF-?1. Because tumors that overexpress TSP-1 grow more slowly, have fewer metastases, and have decreased angiogenesis, TSP-1 provides a novel target for cancer treatment. ABT-510 and ABT-898 are TSP-1 synthetic analogs that mimic its antiangiogenic action. In the present study, we explored the potential effect of ABT-510 and ABT-898 on experimental prolactinomas induced by chronic diethylstilbestrol (DES) treatment in female rats. We demonstrated that a 2-wk treatment with ABT-510 and ABT-898 counteracted the increase in pituitary size and serum prolactin levels as well as the pituitary proliferation rate induced by DES. These inhibitory effects on tumor growth could be mediated by the antiangiogenic properties of the drugs. We also demonstrated that ABT-510 and ABT-898, in addition to their described antiangiogenic effects, increased active TGF-?1 level in the tumors. We postulate that the recovery of the local cytokine activation participates in the inhibition of lactotrope function. These results place these synthetic TSP-1 analogs as potential alternative or complementary treatments in dopamine agonist-resistant prolactinomas.

Recouvreux, M. Victoria; Camilletti, M. Andrea; Rifkin, Daniel B.; Becu-Villalobos, Damasia

2012-01-01

210

In vitro radical scavenging activity of two Columbian Magnoliaceae  

Science.gov (United States)

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

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

2005-08-01

211

Inhibitory effects of caffeic acid ester analogues on free radicals and human liver microsome CYP1A2 activities.  

UK PubMed Central (United Kingdom)

Ethyl caffeate (EC), octyl caffeate(OC), benzyl caffeate(BC) and phenethyl caffeate(PC) were synthesized and evaluated for scavenging of superoxide anion, nitric oxide radical and 1,1-diphenyl-1-picrylhydrazyl radical (DPPH). Antioxidant activity was investigated with reducing power method. Pooled human liver microsome was used for investigating the effects on cytochrome P450 1A2 (CYP1A2) catalytic activities by using phenacetin as a substrate. Dixon and Cornish-Bowden plots were used for enzyme kinetic analysis. The EC, OC, BC and PC potentially inhibited superoxide anion, nitric oxide and DPPH radicals. IC(50) values of superoxide anion scavenging of EC, OC, BC and PC were 16.42, 79.83, 123.69 and 123.69 µg/ml, respectively. EC was more potent than OC and BC in terms of nitric oxide radical scavenger: IC(50) values of EC, OC and BC were 24.16, 37.34 and 52.64 µg/ml, respectively. In addition, the IC(50) values of EC, OC, BC and PC on DPPH radical scavenging were 70.00, 184.56, 285.34 and 866.54 µg/ ml, respectively. The IC(50) values of EC, OC, BC and PC on phenacetin O-deethylation were 124.98, 111.86, 156.68 and 31.05 µg/ml, respectively. Enzyme kinetics showed that the type of inhibition mechanism was mixed-type. The result of this study shows that caffeic acid ester analogues potentially scavenge free radicals and inhibit catalytic activity of CYP1A2. This may lead to important implications in the prevention of CYP1A2-mediated chemical carcinogenesis.

Jaikang C; Chaiyasut C; Narongchai P; Niwatananun K; Narongchai S; Kusirisin W

2011-03-01

212

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

International Nuclear Information System (INIS)

[en] Tributyl phosphate (TBP) is the most common organic compound used in liquid-liquid separations for the recovery of uranium, neptunium, and plutonium from acidic nuclear fuel dissolutions. The goal of these processes is to extract the actinides while leaving fission products in the acidic, aqueous, phase. However, the radiolytic degradation of TBP has been shown to reduce the separation factors for fission products, and to impede the back-extraction of the actinides during stripping. As most previous investigations of the radiation chemistry of TBP have focused on steady state radiolysis and stable product identification, with dibutylphosphoric acid (HDBP) invariably being the major product, here we have determined room temperature rate constants for the reactions TBP and HDBP with the hydroxyl radical ((5.00 +/- 0.02) x 109, (4.40 +/- 0.10) x 109), hydrogen atom ((1.8 +/- 0.2) x 108, (1.1 +/- 0.1) x 108), nitrate radical ((4.3 +/- 0.7) x 106, (2.9 +/- 0.2) x 106) and nitrite radical (

2008-07-01

213

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

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Effect of caffeic acid on the formation of 1-hydroxyethyl radicals via the microsomal ethanol-oxidizing system pathway was examined. The electron spin resonance spin trapping showed that 1-hydroxyethyl radicals form in the control reaction mixture which contained 0.17 M ethanol, 1 mg protein/ml rat ...

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

214

Ascorbic acid as a free radical scavenger in porcine and bovine aqueous humour.  

UK PubMed Central (United Kingdom)

AIM: To study the antioxidant activity, UV absorption, concentration and stability of ascorbic acid (AA) in porcine and bovine aqueous humour (AH). METHODS: Porcine and bovine AH was taken within 5 min after death and frozen at -70 degrees C. The characteristic UV absorption band of AA and the concentration of AA in AH was determined by UV spectrophotometry. The antioxidant activity of AA to serve as a free radical scavenger in AH has been determined by using a novel fluorescent probe for antioxidants, the azoalkane 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO). The fluorescence lifetime and intensity of this probe reflect the concentration of dissolved antioxidants. The time-resolved fluorescence of DBO (laser excitation at 351 nm) in AH and in a neutral phosphate-buffered saline (PBS) solution containing only the natural amount of AA as an additive were measured. RESULTS: The characteristic UV absorption band of AA has its maximum at 266 nm in AH. The concentration of AA in porcine and bovine AH was found to be 0.547 +/- 0.044 and 1.09 +/- 0.16 mM, respectively, by spectrophotometry. The fluorescence lifetime of the probe DBO was reduced from 320 +/- 5 ns in pure aerated PBS to 205 +/- 5 ns in porcine AH and 165 +/- 3 ns in bovine AH. A detailed kinetic analysis of the lifetime shortening suggests that AA contributes approximately 75 and 85% to the antioxidant activity of porcine and bovine AH, respectively. CONCLUSIONS: Our experiments suggest that AA is the major contributor to the antioxidant activity of porcine and bovine AH. The role of AA to serve as an antioxidant in AH is discussed. In addition, UV spectrophotometry is established as an alternative method to determine the concentration of AA in AH.

Erb C; Nau-Staudt K; Flammer J; Nau W

2004-01-01

215

Icariin: a special antioxidant to protect linoleic acid against free-radical-induced peroxidation in micelles.  

UK PubMed Central (United Kingdom)

The objective in this work is to determine the antioxidant capacity and effectiveness of icariin (2-(4'-methoxylphenyl)-3-rhamnosido-5-hydroxyl-7-glucosido-8-(3'-methyl-2-butylenyl)-4-chromanone), the major component in herba epimedii being used widely in traditional Chinese medicine for the treatment of artherosclerosis and neuropathy, in which 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced peroxidation of linoleic acid (LH) in sodium dodecyl sulfate (SDS) acts as the experimental system. By containing an intramolecular hydrogen bond, icariin protects LH against AAPH-induced peroxidation of LH only in SDS, an anionic micelle. The number of trapping peroxyl radicals (LOO(*)), n, by icariin is just 0.0167 whereas alpha-tocopherol (TOH) and L-ascorbyl-6-laurate (VC-12) are 2.14 and 1.25, respectively, with reference to the n of 6-hydroxyl-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox), 2.00. This is also related to how the intramolecular hydrogen bond enhances the bond dissociation enthalpy (BDE) of O-H in icariin. However, calculation of the inhibition rate constant, k(inh), a kinetic parameter to describe the reaction between the antioxidant and LOO(*), results in a k(inh) of icariin at about one magnitude larger than those of Trolox, TOH, and VC-12. This fact reveals that, by the view of kinetics, icariin is an antioxidant with much higher effectiveness. In addition, the antioxidant capacities of icariin used together with other antioxidants have been determined and the results indicate that the n of icariin decreases markedly while the n values of Trolox and TOH increase, even if the n of icariin is a negative value in the presence of VC-12. Furthermore, an analysis of k(inh) in this case reveals that the k(inh)(icariin) increases nearly one magnitude with the decrease of k(inh)(Trolox) and no remarkable change occurs for k(inh)(TOH). The negative value of k(inh)(icariin) in the presence of VC-12 can be regarded as the icariin functions as a prooxidant that can be rectified by VC-12 effectively. These findings implicate that the evaluation of antioxidant activity should not only focus on an n value, a thermodynamic possibility, but k(inh) and the charge property of the micelle should be also taken into account. To some extent, the latter factors are more important than the thermodynamic possibility.

Liu ZQ

2006-05-01

216

Icariin: a special antioxidant to protect linoleic acid against free-radical-induced peroxidation in micelles.  

Science.gov (United States)

The objective in this work is to determine the antioxidant capacity and effectiveness of icariin (2-(4'-methoxylphenyl)-3-rhamnosido-5-hydroxyl-7-glucosido-8-(3'-methyl-2-butylenyl)-4-chromanone), the major component in herba epimedii being used widely in traditional Chinese medicine for the treatment of artherosclerosis and neuropathy, in which 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced peroxidation of linoleic acid (LH) in sodium dodecyl sulfate (SDS) acts as the experimental system. By containing an intramolecular hydrogen bond, icariin protects LH against AAPH-induced peroxidation of LH only in SDS, an anionic micelle. The number of trapping peroxyl radicals (LOO(*)), n, by icariin is just 0.0167 whereas alpha-tocopherol (TOH) and L-ascorbyl-6-laurate (VC-12) are 2.14 and 1.25, respectively, with reference to the n of 6-hydroxyl-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox), 2.00. This is also related to how the intramolecular hydrogen bond enhances the bond dissociation enthalpy (BDE) of O-H in icariin. However, calculation of the inhibition rate constant, k(inh), a kinetic parameter to describe the reaction between the antioxidant and LOO(*), results in a k(inh) of icariin at about one magnitude larger than those of Trolox, TOH, and VC-12. This fact reveals that, by the view of kinetics, icariin is an antioxidant with much higher effectiveness. In addition, the antioxidant capacities of icariin used together with other antioxidants have been determined and the results indicate that the n of icariin decreases markedly while the n values of Trolox and TOH increase, even if the n of icariin is a negative value in the presence of VC-12. Furthermore, an analysis of k(inh) in this case reveals that the k(inh)(icariin) increases nearly one magnitude with the decrease of k(inh)(Trolox) and no remarkable change occurs for k(inh)(TOH). The negative value of k(inh)(icariin) in the presence of VC-12 can be regarded as the icariin functions as a prooxidant that can be rectified by VC-12 effectively. These findings implicate that the evaluation of antioxidant activity should not only focus on an n value, a thermodynamic possibility, but k(inh) and the charge property of the micelle should be also taken into account. To some extent, the latter factors are more important than the thermodynamic possibility. PMID:16686474

Liu, Zai-Qun

2006-05-18

217

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

UK PubMed Central (United Kingdom)

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

Champagne PP; Nesheim ME; Ramsay JA

2013-07-01

218

Nighttime hydrogen peroxide production on sulfuric-acid-aerosols involving nitrate and sulfate radicals  

Energy Technology Data Exchange (ETDEWEB)

The authors propose a nighttime reaction process between nitrate radicals, sulfate radicals, and hydrogen peroxide, which very simple modeling indicates could double the density of hydrogen peroxide in one night. This reaction can be a cumulative one, so the authors urge more detailed study in order to see if the reaction kinetics would support such atmospheric reactions, since hydrogen peroxide concentrations in the lower stratosphere can contribute to ozone depletion.

Pedersen, T. [Univ. of Copenhagen (Denmark)

1995-06-15

219

Separation and characterisation of chlorogenic acid?rich conserves from green coffee beans and their radical scavenging potential  

UK PubMed Central (United Kingdom)

Methanolic extract (Me?) obtained from low?grade green coffee beans (LCB), which is one of the major by?products in the coffee industry, was enriched with phenolics by different methods viz., partitioning in solvents, chromatographic separation using dowex & diaion HP20 resins and precipitation by lead acetate. Separated fractions and Me? were analysed for total polyphenol, chlorogenic acid, caffeine and radical scavenging activity (RSA). Chlorogenic acid isomers of Me? and the isolated fractions were analysed by HPLC. Me? found to contain total polyphenol (16.60?±?0.4%), chlorogenic acids (CGAs) (29.60?±?0.9%), caffeine (7.52?±?0.2%) and exhibited RSA (92.50%) at 100?ppm concentration. Precipitation method resulted significantly (P???0.05) higher phenolics (46.33?±?0.5%) as well as CGAs (43.50?±?0.7%). HPLC analysis indicated that the composition of 5?Caffeoylquinic acid (5?CQA) was more in all the isolated fractions.

Ramalakshmi K; Hithamani G; Asha KR; Jagan Mohan Rao L

2011-01-01

220

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

 
 
 
 
221

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

Directory of Open Access Journals (Sweden)

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

Hua Fan; Guang-Zhong Yang; Tong Zheng; Zhi-Nan Mei; Xiang-Ming Liu; Yu Chen; Su Chen

2010-01-01

222

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

International Nuclear Information System (INIS)

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

1988-01-01

223

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

224

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

International Nuclear Information System (INIS)

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

2013-01-01

225

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

Directory of Open Access Journals (Sweden)

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

Pejin Boris; Bogdanovi?-Pristov Jelena

2012-01-01

226

Thermochromism of metal ion complexes of semiquinone radical anions. Control of equilibria between diamagnetic and paramagnetic species by Lewis acids.  

UK PubMed Central (United Kingdom)

Metal ion complexes of semiquinone radical anions exhibit different types of thermochromism depending on metal ions and quinones. Metal ion complexes of 1,10-phenanthroline-5,6-dione radical anion (PTQ(.-)) produced by the electron-transfer reduction of PTQ by 1,1'-dimethylferrocene (Me(2)Fc) in the presence of metal ions (Mg(2+) and Sc(3+)) exhibit the color change depending on temperature, accompanied by the concomitant change in the ESR signal intensity. In the case of Mg(2+), electron transfer from Me(2)Fc to PTQ is in equilibrium, when the concentration of the PTQ(.-)-Mg(2+) complex (lambda(max) = 486 nm) increases with increasing temperature because of the positive enthalpy for the electron-transfer equilibrium. In contrast to the case of Mg(2+), electron transfer from Me(2)Fc to PTQ is complete in the presence of Sc(3+), which is a much stronger Lewis acid than Mg(2+), to produce the PTQ(.-)-Sc(3+) complex (lambda(max) = 631 nm). This complex is in disproportionation equilibrium and the concentration of the PTQ(.-)-Sc(3+) complex increases with decreasing temperature because of the negative enthalpy for the proportionation direction, resulting in the remarkable color change in the visible region. On the other hand, the p-benzosemiquinone radical anion (Q(.-)) forms a 2:2 pi-dimer radical anion complex [Q(.-)-(Sc(3+))(2)-Q] with Q and Sc(3+) ions at 298 K (yellow color), which is converted to a 2:3 pi-dimer radical anion complex [Q(.-)-(Sc(3+))(3)-Q] with a strong absorption band at lambda(max) = 604 nm (blue color) when the temperature is lowered to 203 K. The change in the number of binding Sc(3+) ions depending on temperature also results in the remarkable color change, associated with the change in the ESR spectra.

Yuasa J; Suenobu T; Fukuzumi S

2005-10-01

227

Thermochromism of metal ion complexes of semiquinone radical anions. Control of equilibria between diamagnetic and paramagnetic species by Lewis acids.  

Science.gov (United States)

Metal ion complexes of semiquinone radical anions exhibit different types of thermochromism depending on metal ions and quinones. Metal ion complexes of 1,10-phenanthroline-5,6-dione radical anion (PTQ(.-)) produced by the electron-transfer reduction of PTQ by 1,1'-dimethylferrocene (Me(2)Fc) in the presence of metal ions (Mg(2+) and Sc(3+)) exhibit the color change depending on temperature, accompanied by the concomitant change in the ESR signal intensity. In the case of Mg(2+), electron transfer from Me(2)Fc to PTQ is in equilibrium, when the concentration of the PTQ(.-)-Mg(2+) complex (lambda(max) = 486 nm) increases with increasing temperature because of the positive enthalpy for the electron-transfer equilibrium. In contrast to the case of Mg(2+), electron transfer from Me(2)Fc to PTQ is complete in the presence of Sc(3+), which is a much stronger Lewis acid than Mg(2+), to produce the PTQ(.-)-Sc(3+) complex (lambda(max) = 631 nm). This complex is in disproportionation equilibrium and the concentration of the PTQ(.-)-Sc(3+) complex increases with decreasing temperature because of the negative enthalpy for the proportionation direction, resulting in the remarkable color change in the visible region. On the other hand, the p-benzosemiquinone radical anion (Q(.-)) forms a 2:2 pi-dimer radical anion complex [Q(.-)-(Sc(3+))(2)-Q] with Q and Sc(3+) ions at 298 K (yellow color), which is converted to a 2:3 pi-dimer radical anion complex [Q(.-)-(Sc(3+))(3)-Q] with a strong absorption band at lambda(max) = 604 nm (blue color) when the temperature is lowered to 203 K. The change in the number of binding Sc(3+) ions depending on temperature also results in the remarkable color change, associated with the change in the ESR spectra. PMID:16833278

Yuasa, Junpei; Suenobu, Tomoyoshi; Fukuzumi, Shunichi

2005-10-20

228

Near-ultraviolet photolysis of beta-phenylpyruvic acid generates free radicals and results in DNA damage.  

UK PubMed Central (United Kingdom)

Ultraviolet A (UVA) light (315-400 nm) is ubiquitously found in our environment and constitutes about 95% of the total solar UV; all UVC and most UVB being absorbed by the stratospheric ozone layer. Compared with UVB and C, UVA does not show any direct effect on biological systems. Indirect effects of UVA, however, have been recognised overwhelmingly and this includes photosensitization of biological and non-biological compounds and production of free radicals many of which include oxygen and are hence known as reactive oxygen species or ROS. Several types of free radicals have been identified although their impacts on various macro- and micro-biomolecules are yet to be fully elucidated. beta-Phenylpyruvic acid is ubiquitously found in eukaryotic cells as a metabolite of phenylalanine, which is subsequently converted to phenyllactate and/or to 2-hydroxyphenylacetate and mandelate. In patients suffering from phenylketonuria the hydroxylation of phenylalanine to tyrosine is defective due to lack of phenylalanine hydroxylase. These result in accumulation and excretion of this compound in the urine. Here we present evidence that photolysis of beta-phenylpyruvic acid by a skin tanning lamp, emitting 99% UVA (315-400 nm) and 1% UVB (290-315 nm) generates carboxyl radicals (CO(2)(*)) and also possibly causes direct electron transfer (or type 1) reactions. Electron paramagnetic resonance was used to detect the free radicals. To determine the biological effects of this photolytic reaction, T7 was exposed to these photolytic reactive agents and found to lead to high levels of phage inactivation. Damage to DNA and/or components such as tail fibre proteins may be involved in T7 inactivation. In addition, our unpublished data suggest that certain phenylketonuria cell lines are more sensitive to PPA+NUV, lending importance to photolytic studies of this agent.

Hargreaves A; Taiwo FA; Duggan O; Kirk SH; Ahmad SI

2007-12-01

229

Effect of indole-3-acetic acid on pea root growth, peroxidase profiles and hydroxyl radical formation  

Directory of Open Access Journals (Sweden)

Full Text Available Changes in growth, peroxidase profiles, and hydroxyl radical formation were examined in IAA (0.5-10 mg/l) treated pea plants grown hydroponically and in isolated roots in liquid in vitro culture. IAA inhibited root elongation, both in hydroponically grown pea plants and in isolated roots in vitro. A remarkable increase in the number of POD iso­forms was noticed in isolated roots grown in vitro, compared to the roots from plants grown hydroponically. IAA induced both disappearance of several root POD isoforms and hydroxyl radical formation in the root and the root cell wall.

Kukavica Biljana; Mitrovi? Aleksandra; Mojovi? M.; Veljovi?-Jovanovi? Sonja

2007-01-01

230

Arylperoxyl radicals. Formation, absorption spectra, and reactivity in aqueous alcohol solutions  

Energy Technology Data Exchange (ETDEWEB)

Aryl radicals (phenyl, 4-biphenylyl, 2-naphthyl, 1-naphthyl, and 9-phenanthryl) were produced by the reaction of the corresponding aryl bromide with solvated electrons and reacted rapidly with oxygen to produce the arylperoxyl radicals. These radicals exhibit optical absorptions in the visible range, with [lambda][sub max] at 470, 550, 575, 650, and 700 nm, respectively. Arylperoxyl radicals react with 2,2[prime]-azinobis(3-ethylbenzothiazoiine-6-sulfonate ion) (ABTS), chlorpromazine, and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox C) by one-electron oxidation. The rate constants k for these reactions, determined from the rate of formation of the one-electron oxidation products as a function of substrate concentration, vary between 4 [times] 10[sup 6] and 2 [times] 10[sup 9] L mol[sup [minus]1] s[sup [minus]1] and increase in the order phenyl-, 4-biphenyl-, 2-naphthyl-, 1-naphthyl-, and 9-phenanthrylperoxyl, the same order as the absorption peaks of these radicals. Good correlation was found between log k and the energy of the absorption peak. 16 refs., 2 figs., 2 tabs.

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

1995-01-05

231

Vinblastine Rapidly Induces NOXA and Acutely Sensitizes Primary Chronic Lymphocytic Leukemia Cells to ABT-737.  

UK PubMed Central (United Kingdom)

Proteins of the BCL2 family provide a survival mechanism in many human malignancies, including chronic lymphocytic leukemia (CLL). The BCL2 inhibitor ABT-263 (navitoclax) is active in clinical trials for lymphoid malignancies, yet resistance is expected on the basis of preclinical models. We recently showed that vinblastine can dramatically sensitize several leukemia cell lines to ABT-737 (the experimental congener of ABT-263). The goal of these experiments was to determine the impact of vinblastine on ABT-737 sensitivity in CLL cells isolated from peripheral blood and to define the underlying mechanism. Freshly isolated CLL cells from 35 patients, as well as normal lymphocytes and platelets, were incubated with various microtubule-disrupting agents plus ABT-737 to assess sensitivity to the single agents and the combination. ABT-737 and vinblastine displayed a range of sensitivity as single agents, and vinblastine markedly sensitized all CLL samples to ABT-737 within six hours. Vinblastine potently induced the proapoptotic protein PMAIP1 (NOXA) in both time- and dose-dependent manner and this was required for the observed apoptosis. Combretastatin A4, which dissociates microtubules by binding to a different site, had the same effect, confirming that interaction of these agents with microtubules is the initial target. Similarly, vincristine and vinorelbine induced NOXA and enhanced CLL sensitivity to ABT-737. Furthermore, vinblastine plus ABT-737 overcame stroma-mediated resistance to ABT-737 alone. Apoptosis was induced with clinically achievable concentrations with no additional toxicity to normal lymphocytes or platelets. These results suggest that vinca alkaloids may improve the clinical efficacy of ABT-263 in patients with CLL. Mol Cancer Ther; 12(8); 1504-14. ©2013 AACR.

Bates DJ; Danilov AV; Lowrey CH; Eastman A

2013-08-01

232

Antioxidant potential and radical-scavenging effects of flavonoids from the leaves of Psidium cattleianum grown in French Polynesia.  

UK PubMed Central (United Kingdom)

Psidium cattleianum J. Sabine (Myrtaceae) is a traditional medicinal plant in French Polynesia. The leaves and roots possess many medicinal properties. These effects may be correlated with the presence of antioxidant compounds. Seven flavonoids along with a benzoic acid were isolated from the leaves of P. cattleianum. The compounds indicated strong antioxidant and radical-scavenging activities in ALP, DPPH(·), ABTS(·-) and ORAC assays. This study demonstrates that the leaves of P. cattleianum possess main compounds with interesting antioxidant and radical-scavenging activities, as clarified by four biological assays. Our findings may justify the use of these leaves in the traditional medicine of French Polynesia. Among the total eight known compounds, reynoutrin and luteolin were isolated for the first time from the genus Psidium.

Ho R; Violette A; Cressend D; Raharivelomanana P; Carrupt PA; Hostettmann K

2012-01-01

233

Measurments of nitrous acid, nitrate radicals, formaldehyde and nitrogen dioxide for the Southern California Air Quality Study by differential optical  

International Nuclear Information System (INIS)

This paper reports that two rapid scanning (?3000 scan min-1) differential optical absorption spectrometers were interfaced to 25 m basepath open, multiple reflection systems operated routinely at a total optical path of 800 m at Long Beach and Claremont, CA during the 1987 Southern California Air Quality Study. These instruments permitted measurements of atmospheric concentrations of nitrous acid, nitrogen dioxide and formaldehyde at the part per billion levels, and detection of the nitrate radicals with sensitivity of several tens of parts per trillion

1991-01-01

234

Free Radical Scavenging Activity of Kielmeyera variabilis (Clusiaceae)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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-ethylenebenzothi...

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

235

Definition of the ABTS-test efficiency by Raman spectroscopy method  

Science.gov (United States)

Dynamics of the biochemical reactions of the ABTS-test had been investigated by the Raman spectroscopy method for the first time in this work. Velocity coefficients of the given reactions and the theoretical model of the ABTS-test reactions had been specified by the experiment.

Kutsenko, S. A.; Ulchenko, I. N.

2007-07-01

236

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

2008-10-08

237

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

DEFF Research Database (Denmark)

The reactions of OH radicals with 2-, 3-, 4-chlorobenzoic acids (ClBzA) and chlorobenzene (ClBz), k(OH+substrates)=(4.5?6.2)×109 dm3 mol?1 s?1, have been studied by pulse radiolysis in N2O saturated solutions. The absorption maxima of the OH-adducts were in the range of 320?340 nm. Their decay was according to a second-order reaction, 2k=(1?9)×108 dm3 mol?1 s?1. In the presence of N2O/O2 the formation of peroxyl radicals was detectable for 2-, 4-ClBzA and ClBz, k(OH-adduct+O2)=(2?4)×107 dm3 mol?1 s?1, while this reaction for 3-ClBzA was too slow to be registered. In the presence of N2O the degradation rates induced by gamma radiation were very similar for all chlorobenzoic acids, yet the chloride formation was distinctly higher for 3-ClBzA. In the presence of oxygen the initial degradation of 2-and 4-ClBzA equaled the OH-radical concentration, whereas in case of 3-ClBzA only 60% of OH led to degradation. The order for the efficiency of dehalogenation was 4->2->3-ClBzA. Several primary radiolytic products could be detected by HPLC. To evaluate the toxicity of final products a bacterial bioluminescence test was carried out.

Zona, Robert; Solar, Sonja

2010-01-01

238

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

International Nuclear Information System (INIS)

The reactions of OH radicals with 2-, 3-, 4-chlorobenzoic acids (ClBzA) and chlorobenzene (ClBz), k(?OH+substrates)=(4.5-6.2)x109 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)x108 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)x107 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.

2010-01-01

239

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

Energy Technology Data Exchange (ETDEWEB)

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

Gaffney, J.S.; Marley, N.A.

1993-05-01

240

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

International Nuclear Information System (INIS)

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

1993-01-01

 
 
 
 
241

The gas-phase reaction of methane sulfonic acid with the hydroxyl radical without and with water vapor.  

UK PubMed Central (United Kingdom)

The gas phase reaction between methane sulfonic acid (CH3SO3H; MSA) and the hydroxyl radical (HO), without and with a water molecule, was investigated with DFT-B3LYP and CCSD(T)-F12 methods. For the bare reaction we have found two reaction mechanisms, involving proton coupled electron transfer and hydrogen atom transfer processes that produce CH3SO3 and H2O. We also found a third reaction mechanism involving the double proton transfer process, where the products and reactants are identical. The computed rate constant for the oxidation process is 8.3 × 10(-15) cm(3) s(-1) molecule(-1). CH3SO3H forms two very stable complexes with water with computed binding energies of about 10 kcal mol(-1). The presence of a single water molecule makes the reaction between CH3SO3H and HO much more complex, introducing a new reaction that consists in the interchange of H2O between HO and CH3SO3H. Our kinetic calculations show that 99.5% of the reaction involves this interchange of the water molecule and, consequently, water vapor does not play any role in the oxidation reaction of methane sulfonic acid by the hydroxyl radical.

Jørgensen S; Jensen C; Kjaergaard HG; Anglada JM

2013-04-01

242

Correlation between iodide dosimetry and terephthalic acid dosimetry to evaluate the reactive radical production due to the acoustic cavitation activity.  

UK PubMed Central (United Kingdom)

Acoustic cavitation plays an important role in sonochemical processes and the rate of sonochemical reaction is influenced by sonication parameters. There are several methods to evaluate cavitation activity such as chemical dosimetry. In this study, to comparison between iodide dosimetry and terephthalic acid dosimetry, efficacy of sonication parameters in reactive radical production has been considered by iodide and terephthalic acid dosimetries. For this purpose, efficacy of different exposure parameters on cavitations production by 1 MHz ultrasound has been studied. The absorbance of KI dosimeter was measured by spectrophotometer and the fluorescence of terephthalic acid dosimeter was measured using spectrofluorometer after sonication. The result of experiments related to sonication time and intensity showed that with increasing time of sonication or intensity, the absorbance is increased. It has been shown that the absorbance for continuous mode is remarkably higher than for pulsing mode (p-value < 0.05). Also results show that with increasing the duty cycles of pulsed field, the inertial cavitation activity is increased. With compensation of sonication time or intensity in different duty cycles, no significant absorbance difference were observed unless 20% duty cycle. A significant correlation between the absorbance and fluorescence intensities (count) at different intensity (R = 0.971), different sonication time (R = 0.999) and different duty cycle (R = 0.967) were observed (p-value < 0.05). It is concluded that the sonication parameters having important influences on reactive radical production. These results suggest that there is a correlation between iodide dosimetry and terephthalic acid dosimetry to examine the acoustic cavitation activity in ultrasound field.

Ebrahiminia A; Mokhtari-Dizaji M; Toliyat T

2013-01-01

243

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

Directory of Open Access Journals (Sweden)

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

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

2009-01-01

244

Determination of Arrhenius and Thermodynamic Parameters for the Aqueous Reaction of the Hydroxyl Radical with Lactic Acid  

Energy Technology Data Exchange (ETDEWEB)

Lactic acid is a major component of the TALSPEAK process planned for use in the separation of trivalent lanthanide and actinide elements. This acid acts both as a buffer, and also to protect the actinide complexant from radiolytic damage. However, there is little kinetic information on the reaction of water radiolysis species with lactic acid, particularly under the anticipated process conditions of aerated aqueous solution at pH~3, where oxidizing reactions are expected to dominate. Here we have determined temperature-dependent reaction rate constants for the reactions of the hydroxyl radical with lactic acid and the lactate ion. For lactic acid this rate constant is given by the equation: ln k1 = (23.85 ± 0.19) – (1120 ± 54) / T, corresponding to an activation energy of 9.31 ± 0.45 kJ mol-1 and a room temperature reaction rate constant of (5.24 ± 0.09) x 108 M-1 s-1 (24.0oC). For the lactate ion, the temperature-dependent rate constant is given by: ln k2 = (24.83 ± 0.14) – (1295 ± 42) / T, for an activation energy of 10.76 ± 0.35 kJ mol-1 and a room temperature value of (7.77 ± 0.11) x 108 M-1 s-1 (22.2oC). These kinetic data have been combined with autotitration measurements to determine the temperature-dependent behavior of the lactic acid pKa value, allowing thermodynamic parameters for the acid dissociation to be calculated as ?Hº = -10.75 ± 1.77 kJ mol-1, ?Sº = -103.9 ± 6.0 J K-1 mol-1 and ?Gº = 20.24 ± 2.52 kJ mol-1 at low ionic strength.

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

2009-01-01

245

Species-dependent metabolism of a novel selective ?7 neuronal acetylcholine receptor agonist ABT-107.  

UK PubMed Central (United Kingdom)

Metabolism of ABT-107 was investigated in in vitro hepatic systems, in rat and monkey receiving [¹?C]ABT-107, and in vivo plasma in rat, dog, monkey and human. In in vitro hepatic systems, ABT-107 was primarily cleared via oxidative metabolism, and proceeded via two parallel pathways. Pathway 1, ABT-107 was oxidized at the nitrogen of quinuclidine moiety to form M1. Pathway 2, oxidation occurred at indole-containing moiety to form M2. Metabolism via N-oxidation was predominant in dog and rat, while in monkey and human, metabolism proceeded primarily via oxidation of indole-containing moiety. ABT-107 was extensively metabolized in vivo in rat and monkey. M1 was primarily found in rat urine and bile; whereas, M2 was the major metabolite in monkey urine and feces. M1 was the predominant circulating metabolite in dog and rat. M2 was the primary circulating metabolite in monkey and human. Enzymatic studies suggested M1 formation was primarily mediated by renal FMO1. CYP3A4, 1A2, 2J2 and 2D6 were primary enzymes catalyzing M2 formation. Biotransformation of ABT-107 in human and monkey is markedly different from that in dog and rat, suggesting that monkey is an appropriate model for predicting human biotransformation and toxicology of ABT-107.

Liu H; Deng X; Liu J; Liu N; Stuart P; Xu H; Guan Z; Marsh KC; De Morais SM

2013-09-01

246

Rate constants for the reactions of halogenated organic radicals  

International Nuclear Information System (INIS)

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

1988-01-01

247

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

Scientific Electronic Library Online (English)

Full Text Available 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 - foram 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 qu (more) e 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 bioa (more) ctive 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).

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

2009-01-01

248

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background Gallic acid (3,4,5-trihydroxybenzoic acid) is found in a wide variety of plants; it is extensively used in tanning, ink dyes, as well as in the manufacturing of paper. The gallate moiety is a key component of many functional phytochemicals. In this work electron ...

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

249

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?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

250

Macrophages overexpressing tartrate-resistant acid phosphatase show altered profile of free radical production and enhanced capacity of bacterial killing.  

Science.gov (United States)

Activated macrophages and osteoclasts express high amounts of tartrate-resistant acid phosphatase (TRACP, acp5). TRACP has a binuclear iron center with a redox-active iron that has been shown to catalyze the formation of reactive oxygen species (ROS) by Fenton's reaction. Previous studies suggest that ROS generated by TRACP may participate in degradation of endocytosed bone matrix products in resorbing osteoclasts and degradation of foreign compounds during antigen presentation in activated macrophages. Here we have compared free radical production in macrophages of TRACP overexpressing (TRACP+) and wild-type (WT) mice. TRACP overexpression increased both ROS levels and superoxide production. Nitric oxide production was increased in activated macrophages of WT mice, but not in TRACP+ mice. Macrophages from TRACP+ mice showed increased capacity of bacterial killing. Recombinant TRACP enzyme was capable of bacterial killing in the presence of hydrogen peroxide. These results suggest that TRACP has an important biological function in immune defense system. PMID:15845367

Räisänen, Seija R; Alatalo, Sari L; Ylipahkala, Hannele; Halleen, Jussi M; Cassady, A Ian; Hume, David A; Väänänen, H Kalervo

2005-05-27

251

Conformation specific and charge directed reactivity of radical cation intermediates of alpha-substituted (amino, hydroxy, and keto) bioactive carboxylic acids.  

UK PubMed Central (United Kingdom)

The reactivity of radical cation carboxylic acids is investigated on the basis of mass spectrometry, infrared-vacuum ultraviolet (IR-VUV) photoionization spectroscopy, and high level correlated ab initio calculations. Their reactivity is found to be highly conformation specific and is governed by their initial charge distribution following ionization. In the present work, the radical cations of lactic acid, pyruvic acid, glycine, and valine are studied to probe their stability and conformation specific reactivity following single photon, vertical ionization at 10.5 eV. For lactic acid, glycine, and valine, the localization site of the hole following sudden removal of an electron depends on their specific intramolecular hydrogen bonding network. Lactic acid, glycine, and valine undergo complete fragmentation following vertical ionization at 10.5 eV; however, pyruvic acid does not completely dissociate following vertical ionization. Only 45% of the pyruvic acid parent ions undergo C(alpha)-C(carboxylic) bond dissociation. If the hole is localized on the COOH moiety of glycine, valine, and lactic acid, a hydrogen transfer is favored from the COOH to the alpha-substituent. If the hole is localized on the alpha-hydroxy or -amine substituent and the singly occupied molecular orbital (SOMO, where the hole resides) is parallel to the C(alpha)-C(carboxylic) bond, C(alpha)-C(carboxylic) bond dissociation occurs through charge transfer from the alpha-substituent to the C(alpha)-C(carboxylic) bond. The present study reveals that the specific conformations of alpha-substituted carboxylic acids govern their radical cationic reactivity. The radical cation of pyruvic acid exhibits a special stability due to enolization of the alpha-keto form on the cationic surface.

Bhattacharya A; Shin JW; Clawson KJ; Bernstein ER

2010-09-01

252

Mutant Prevention Concentrations of ABT-492, Levofloxacin, Moxifloxacin, and Gatifloxacin against Three Common Respiratory Pathogens  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The purpose of this study was to compare the mutant prevention concentration (MPC) of ABT-492 to those of levofloxacin, moxifloxacin, and gatifloxacin against Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. The fluoroquinolones had comparable mutation selection windows, ...

Hermsen, Elizabeth D.; Hovde, Laurie B.; Konstantinides, George N.; Rotschafer, John C.

253

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

UK PubMed Central (United Kingdom)

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.

Hamauzu Y; Mizuno Y

2011-03-01

254

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

Energy Technology Data Exchange (ETDEWEB)

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

Bobrowski, K.; Raghavan, N.V.

1982-10-28

255

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

1982-10-28

256

ABT-737 is highly effective against molecular subgroups of multiple myeloma.  

UK PubMed Central (United Kingdom)

Multiple myeloma is a plasma cell malignancy that is heterogeneous with respect to its causative molecular abnormalities and the treatment response of patients. The Bcl-2 protein family is critical for myeloma cell survival. ABT-737 is a cell-permeant compound that binds to Bcl-2 and Bcl-x(L) but not to Mcl-1. Using a myeloma cell line collection (n = 25) representative of different molecular translocations, we showed that ABT-737 effectively kills a subset of cell lines (n = 6), with a median lethal dose ranging from 7 ± 0.4 nM to 150 ± 7.5 nM. Of interest, all sensitive cell lines harbored a t(11;14). We demonstrated that ABT-737-sensitive and ABT-737-resistant cell lines could be differentiated by the BCL2/MCL1 expression ratio. A screen of a public expression database of myeloma patients indicates that the BCL2/MCL1 ratio of t(11;14) and hyperdiploid patients was significantly higher than in all other groups (P < .001). ABT-737 first induced the disruption of Bcl-2/Bax, Bcl-2/Bik, or Bcl-2/Puma complexes, followed by the disruption of Bcl-2 heterodimers with Bak and Bim. Altogether, the identification of a subset of cell lines and primary cells effectively killed by ABT-737 alone supported the evaluation of ABT-263, an orally active counterpart to ABT-737, for the treatment of t(11;14) and hyperdiploid groups of myeloma harboring a Bcl-2(high)/Mcl-1(low) profile.

Bodet L; Gomez-Bougie P; Touzeau C; Dousset C; Descamps G; Maïga S; Avet-Loiseau H; Bataille R; Moreau P; Le Gouill S; Pellat-Deceunynck C; Amiot M

2011-10-01

257

Impurity rejection in the crystallization of ABT-510 as a method to establish starting material specifications.  

UK PubMed Central (United Kingdom)

Understanding impurity rejection in a drug substance crystallization process is valuable for establishing purity specifications for the starting materials used in the process. Impurity rejection has been determined for all known ABT-510 impurities and for many of the reasonable & conceivable impurities. Based on this study, a very high purity specification (e.g., > 99.7%) can be set for ABT-510 with a high level of confidence.

Tolle JC; Becker CL; Califano JC; Chang JL; Gernhardt K; Napier JJ; Wittenberger SJ; Yuan J

2009-01-01

258

Hydrogen Transfer between Sulfuric Acid and Hydroxyl Radical in the Gas Phase: Competition among Hydrogen Atom Transfer, Proton-Coupled Electron-Transfer, and Double Proton Transfer  

Digital Repository Infrastructure Vision for European Research (DRIVER)

9 pages, 2 tables, 1 scheme. , In an attempt to assess the potential role of the hydroxyl radical in the atmospheric degradation of sulfuric acid, the hydrogen transfer between H2SO4 and HO• in the gas phase has been investigated by means of DFT and quantum-mechanical electronic-structure calculations,...

Anglada Rull, Josep M; Olivella, Santiago; Solé, Albert

259

Asymmetric cleavage of 2,2'-pyridil to a picolinic acid anion radical coordinated to ruthenium(II): splitting of water to hydrogen.  

UK PubMed Central (United Kingdom)

The Ru(II)-H and water promoted asymmetric cleavage of 2,2'-pyridil to pyridine-2-carbaldehyde and unprecedented picolinic acid anion radical (PyCOOH(-)?) complexes, which in solution produce H2 gas and diamagnetic picolinate complexes of ruthenium(II) in moderate yields, is reported.

Biswas MK; Patra SC; Maity AN; Ke SC; Weyhermüller T; Ghosh P

2013-05-01

260

Synthesis of alkaloid analogues from ?-amino acids by one-pot radical decarboxylation/alkylation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

8 pages, 1 figure, 7 schemes.-- Printed version published Aug 2005. , A mild, one-pot methodology to obtain ?-substituted nitrogen heterocycles from commercial amino acids is reported. This versatile procedure has been applied to the synthesis of different alkaloid analogues in good to excellent yields...

Boto, Alicia; León, Yolanda de; Gallardo, Juan Antonio; Hernández, Rosendo

 
 
 
 
261

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

UK PubMed Central (United Kingdom)

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

Dudonné S; Vitrac X; Coutière P; Woillez M; Mérillon JM

2009-03-01

262

Interaction(s) between essential fatty acids, eicosanoids, cytokines, growth factors and free radicals: relevance to new therapeutic strategies in rheumatoid arthritis and other collagen vascular diseases.  

UK PubMed Central (United Kingdom)

Eicosanoids, lymphokines, and free radicals are known to participate in the pathogenesis of inflammation. Tumour necrosis factor (TNF), interleukin-1 and 6 (IL-1 and IL-6) and colony stimulating factor -1 (CSF-1) are secreted mainly by activated macrophages, whereas T-cells secrete IL-2, IL-3, IL-4 and interferon-gamma (IFN-gamma). In addition, activated macrophages and lymphocytes can also produce eicosanoids and free radicals which have potent pro-inflammatory actions. Eicosanoids, lymphokines, and free radicals can modulate the immune response, cell proliferation, stimulate collagenase and proteases secretion and induce bone resorption; events which are known to be associated with various collagen vascular diseases. On the other hand transforming growth factor-beta (TGF-beta) produced by synovial tissue, platelets and lymphocytes can inhibit collagenase production, suppress T-cell and NK-cell proliferation and activation and block free radical generation and seems to be of benefit in rheumatoid arthritis. Drugs such as cyclosporine, 1,25,dihydroxycholecalciferol and pentoxyfylline can block lymphokine and TNF production and thus, may inhibit the inflammatory process. Essential fatty acids, the precursors of eicosanoids, are suppressors of T-cell proliferation, IL-1, IL-2 and TNF production and have been shown to be of benefit in rheumatoid arthritis, systemic lupus erythematosus and glomerulonephritis. Thus, the interactions between essential fatty acids, eicosanoids, lymphokines, TGF-beta and free radicals suggest that new therapeutic strategies can be devised to modify the course of collagen vascular diseases.

Das UN

1991-12-01

263

Atmospheric peroxy radical measurements by ion molecule reaction-mass spectrometry: A novel analytical method using amplifying chemical conversion to sulfuric acid  

Science.gov (United States)

A novel method for measuring atmospheric peroxy radical concentrations has been developed and tested in various field and laboratory studies. The method relies on amplifying chemical conversion of peroxy radicals to gaseous sulfuric acid via the chain reaction with NO and SO2 (NO/SO2 chemical amplifier) and detection of the reaction product sulfuric acid by ion molecule reaction-mass spectrometry (IMR-MS). The high sensitivity of IMR-MS and the low atmospheric background of gaseous H2SO4 allows for work with small chain lengths and short reaction times, which reduces the impact of potential interference and loss processes. The basic kinetic foundations of the amplification process including its sensitivity to interference and radical loss processes are discussed. Field and laboratory measurements indicate nominal operation of the NO/SO2 chemical amplifier system and its suitability for highly sensitive peroxy radical measurements even under atmospheric conditions characterized by low peroxy radical concentrations such as nighttime, winter, and high-latitude conditions.

Reiner, Thomas; Hanke, Markus; Arnold, Frank

1997-01-01

264

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

265

Free radical degradation of pentafluoro benzioic acid (Preprint No. RC.21)  

International Nuclear Information System (INIS)

[en] Radiolytic degradation of pentafluorobenzoic acid (PFBA) in aqueous solutions has been undertaken with a view to understand the degradation mechanism. Fluorocarbons in general have high ionisation potential, electron affinity and high C-F bond strength. F- ions and H2O2 yields are measured in irradiated solutions of PFBA by specific F- ion electrode and spectrophotometry respectively. Dose rate was ? 24Gy/m. G(F-) and G(H2O2) for 2.5x10-4M PFBA under variety of conditions are given. (author)

1989-01-01

266

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.  

UK PubMed Central (United Kingdom)

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.

Quansah JK; Udenigwe CC; Saalia FK; Yada RY

2013-03-01

267

Structure of ascorbic acid and its biological function. I. ESR determination of the ascorbyl radical in biological samples and in model systems.  

UK PubMed Central (United Kingdom)

ESR investigations on lyophilized systems have shown that the signal at g = 2.005 can be explained by an interaction between Na+ or K+ and the anionic ascorbyl radical. The unpaired electron is probably localized near the C(4) region and is produced by a cleavage of an H atom belonging to a water molecule bound tightly to C(4). Experiments on aqueous samples revealed that ascorbic acid in its radical configuration and in its highest concentration exists only at physiological pH and temperature. An additional splitting is obtained by the ring formation between C(3) and C(6)-OH. The coupling constants of the triplets produced by the CH2-6 protons differ between ascorbic acid and isoascorbic acid. Thus, the ESR technique can be applied for an easy distinction between these two epimers.

Lohmann W; Holz D

1984-01-01

268

Kinetics of formation and reactions of thiyl radicals in aqueous solution  

Energy Technology Data Exchange (ETDEWEB)

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

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

1992-03-04

269

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

International Nuclear Information System (INIS)

One-electron transfer equilibria between seven phenothiazines were characterized by pulse radiolysis, producing radical-cations via oxidation by Br2 .- or (SCN)2 .- radicals. The reduction potentials of the phenothiazine radicals were determined by cyclic voltammetry. As an independent check, the redox equilibrium between one phenothiazine and the redox indicator ABTS was investigated. The data establish phenothiazines as useful indicators for radical redox properties. However, there are potential problems of aggregation, additional reactions with Br-/Br2 .- and reactivity of the radicals towards buffers or other nucleophiles.

2006-01-01

270

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2006-09-15

271

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

Science.gov (United States)

One-electron transfer equilibria between seven phenothiazines were characterized by pulse radiolysis, producing radical-cations via oxidation by Br2·- or (SCN)2·- radicals. The reduction potentials of the phenothiazine radicals were determined by cyclic voltammetry. As an independent check, the redox equilibrium between one phenothiazine and the redox indicator ABTS was investigated. The data establish phenothiazines as useful indicators for radical redox properties. However, there are potential problems of aggregation, additional reactions with Br-/Br2·- and reactivity of the radicals towards buffers or other nucleophiles.

Madej, Edyta; Wardman, Peter

2006-09-01

272

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

Directory of Open Access Journals (Sweden)

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

AÍDA NEIRA; MIGUEL TARRAGA; ROSA CATALAN

2008-01-01

273

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

Scientific Electronic Library Online (English)

Full Text Available 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 carbox (more) ylic 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).

NEIRA, AÍDA; TARRAGA, MIGUEL; CATALAN, ROSA

2008-03-01

274

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

Science.gov (United States)

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

Gupta, Suneel; Banerjee, Rintu

2011-01-01

275

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

UK PubMed Central (United Kingdom)

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

Gupta S; Banerjee R

2011-01-01

276

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

Directory of Open Access Journals (Sweden)

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; Nedialkov Paraskev; Kitanov Gerassim

2010-01-01

277

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

Science.gov (United States)

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

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

2010-04-08

278

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

UK PubMed Central (United Kingdom)

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

Gautam R; Karkhile KV; Bhutani KK; Jachak SM

2010-10-01

279

Effects of rice protein hydrolysates prepared by microbial proteases and ultrafiltration on free radicals and meat lipid oxidation  

UK PubMed Central (United Kingdom)

This study was to evaluate whether rice protein hydrolysates with strong antioxidant activity can be used to prevent lipid oxidation and improve shelf-life of meat products. Rice proteins were hydrolysed by three microbial proteases and further separated by sequential ultrafiltration to 12 hydrolysate fractions. The resulting hydrolysates were first evaluated for free radical scavenging capacity. The oxygen radical absorbance capacity (ORAC) of the fractions varied significantly ranging between 34.2 and 87.3 ?mol Trolox equivalents (TE)/g dry weight with two small peptide fractions: Val-F3 produced by Validase from Aspergillus oryzae and AP-F3 produced by alkaline protease from Bacillus licheniformis possessing the highest values. The hydrolysate fractions at 100 mg/mL scavenged 31.2–49.7% of 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH•). The hydrolysates also exerted remarkable cation radical 2,2?-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS+•) scavenging activity (10.8 and 28.3 ?mol TE/g dry weight). Val-F3 and AP-F3 were incorporated into ground beef to determine their effect on lipid oxidation during a 15-day storage period. Val-F3 treatment at 500 ?g/g inhibited lipid oxidation by 19% and 15% at storage day 8 and 15, suggesting that rice protein hydrolysates could be further developed and used to improve shelf-life of meat products.

Zhou K; Canning C; Sun S

2013-01-01

280

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; MARIA T PEPATO; IGUATEMY L BRUNETTI

2008-01-01

 
 
 
 
281

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 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 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. (V (more) itaceae) (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.

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

2008-01-01

282

Free-radical scavenging and mitochondrial antioxidant activities of Reishi-Ganoderma lucidum (Curt: Fr) P. Karst and Arogyapacha-Trichopus zeylanicus Gaertn extracts.  

UK PubMed Central (United Kingdom)

Endogenous damage to mitochondrial DNA by free radicals is believed to be a major contributory factor to aging. The current study examined the effects of the extracts of two important anti-fatigue and rejuvenating medicinal herbs Ganoderma lucidum and Trichopus zeylanicus for their free-radical scavenging property and for their effects on liver mitochondrial antioxidant activity in aged mice. Both extracts were administrated orally to aged BALB/c mice at doses of 50 and 250 mg/kg body weight for 15 days. Super oxide dismutase (SOD) and catalase (CAT) activity and levels of reduced glutathione (GSH) and lipid peroxidation as equivalents of malondialdehyde (MDA) formed were determined. Groups of young mice and aged mice (more than 15 months old) were taken as controls. Both G. lucidum and T. zeylanicus extracts increased antioxidant status in liver mitochondria of aged mice compared with the aged control. Higher levels of GSH, increased activity of SOD and CAT, and decreased level of MDA in both treated groups compared with the controls were evident. Both extracts possessed significant 2,2-diphenyl-1-picrylhydrazil (DPPH), 2, 2'-azinobis (3-ethylbenzothiazolin-6-sulphonic acid) (ABTS) radical scavenging activities and ferric reducing antioxidant power (FRAP). The DPPH, ABTS, and FRAP activities were higher in G. lucidum extract than in T. zeylanicus. G. lucidum extract also showed superoxide and hydroxyl radical scavenging activities. T. zeylanicus had significantly higher lipid peroxidation inhibiting activity than G. lucidum. Thus, we conclude that the antioxidative effect of the G. lucidum extract was higher than that of T. zeylanicus. Our findings suggest a potential therapeutic efficacy of G. lucidum extract to protect against aging and to a certain extent against age-related degenerative diseases.

Cherian E; Sudheesh NP; Janardhanan KK; Patani G

2009-01-01

283

Nitro radical anions from megazol and related nitroimidazoles in aprotic media. A father-son type reaction triggered by an acidic proton  

Energy Technology Data Exchange (ETDEWEB)

We have studied the electrochemical reduction of some nitroimidazoles such as megazol(2-amino-5-(1-methyl-5-nitro-2-imidazolyl)-1,3,4-thiadiazol, CAS 19622-55-0) and two related derivatives in aprotic media (100% DMF, 0.1 M TBAP). All the studied compounds were easily reducible in aprotic media generating the corresponding nitro radical anions as products of the one electron reduction of the parent compound. The nitro radical anions decay by a dimerization reaction and the dimerization rate constants were obtained according to the Olmstead's approach by obtaining values of 150{+-}24, 1690{+-}42 and 640{+-}32 M{sup -1} s{sup -1} for megazol, GC-361 and GC-284, respectively. The existence of an acidic proton on the acetamide group in the GC-361 molecule triggered the appearance of father-son type reactions between the nitro radical anion from GC-361 (son compound) and GC-361 (father compound) generating the neutral radical and the conjugate base of GC-361. Thus the nitro radical anion from GC-361 acts as a Broensted base abstracting the proton of the acetamide group in the GC-361 derivative of megazol.

Bonta, M.; Chauviere, G.; Perie, J.; Nunez-Vergara, L.J.; Squella, J.A

2002-09-25

284

Nitro radical anions from megazol and related nitroimidazoles in aprotic media. A father-son type reaction triggered by an acidic proton  

International Nuclear Information System (INIS)

We have studied the electrochemical reduction of some nitroimidazoles such as megazol(2-amino-5-(1-methyl-5-nitro-2-imidazolyl)-1,3,4-thiadiazol, CAS 19622-55-0) and two related derivatives in aprotic media (100% DMF, 0.1 M TBAP). All the studied compounds were easily reducible in aprotic media generating the corresponding nitro radical anions as products of the one electron reduction of the parent compound. The nitro radical anions decay by a dimerization reaction and the dimerization rate constants were obtained according to the Olmstead's approach by obtaining values of 150±24, 1690±42 and 640±32 M-1 s-1 for megazol, GC-361 and GC-284, respectively. The existence of an acidic proton on the acetamide group in the GC-361 molecule triggered the appearance of father-son type reactions between the nitro radical anion from GC-361 (son compound) and GC-361 (father compound) generating the neutral radical and the conjugate base of GC-361. Thus the nitro radical anion from GC-361 acts as a Broensted base abstracting the proton of the acetamide group in the GC-361 derivative of megazol

285

Forgotten radicals in biology.  

Science.gov (United States)

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

Luc, Rochette; Vergely, Catherine

2008-12-01

286

Forgotten radicals in biology.  

UK PubMed Central (United Kingdom)

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

Luc R; Vergely C

2008-12-01

287

Forgotten Radicals in Biology  

Directory of Open Access Journals (Sweden)

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

Rochette Luc; Catherine Vergely

2008-01-01

288

Biotechnological treatment for colorless denim and textil wastewater treatment with laccase and abts  

Directory of Open Access Journals (Sweden)

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

Myrna Solís-Oba; Javier Almendáriz; Gustavo Viniegra-González

2008-01-01

289

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

UK PubMed Central (United Kingdom)

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.

Focsan AL; Bowman MK; Shamshina J; Krzyaniak MD; Magyar A; Polyakov NE; Kispert LD

2012-11-01

290

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

2012-10-25

291

Radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl of ascorbic acid 2-glucoside (AA-2G) and 6-acyl-AA-2G.  

UK PubMed Central (United Kingdom)

The radical scavenging activity of the stable derivatives, which are O-substituted at the C-2 position of ascorbic acid (AA), against 1,1-diphenyl-2-picrylhydrazyl (DPPH) was evaluated in buffer under different pH conditions, and compared with those of AA and alpha-tocopherol. AA was shown to have 50% radical scavenging ability (EC50) at a concentration of 2.2 x 10(-5) M against 0.1 mM DPPH in 60% ethanol. Ascorbyl 6-palmitate, a lipophilic AA derivative which has a free endiol group and is therefore unstable, also showed potent radical scavenging activity with EC50 of 2.9 x 10(-5) M. A typical lipophilic antioxidant, alpha-tocopherol gave a similar EC50 value as that of AA. In contrast, ascorbyl 2,6-dipalmitate, AA 2-phosphate and AA 2-sulfate exhibited negligible scavenging activity. On the other hand, 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G) and a series of 6-O-acyl-2-O-alpha-D-glucopyranosyl-L-ascorbic acids (6-Acyl-AA-2G) themselves exhibited the radical scavenging activity of EC50: 6.1 x 10(-5) M and 4.4 x 10(-5)-5.9 x 10(-5) M, respectively, although their activities were lower than that of AA. Among 6-Acyl-AA-2G derivatives, the EC50 values tended to decrease with increasing length of their acyl carbon group. Increasing pH of the buffer resulted in decrease in the scavenging activity of all compounds tested as expected. We speculate that the difference in the radical scavenging activity of derivatives O-substituted at the C-2 position of AA may be ascribed to the linkage type of the substituent group to the endiol-lactone resonance system and the degree of dissociation of the C-3 proton.

Fujinami Y; Tai A; Yamamoto I

2001-05-01

292

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

UK PubMed Central (United Kingdom)

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

Ribeiro T; Motta A; Marcus P; Gaigeot MP; Lopez X; Costa D

2013-11-01

293

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

The free-radical-scavenging activities of various solvent extracts of Microcos paniculata were evaluated through in vitro model systems, such as 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and Co (II) EDTA-induced luminol chemiluminescence by flow...

Hua Fan; Guang-Zhong Yang; Tong Zheng; Zhi-Nan Mei; Xiang-Ming Liu; Yu Chen; Su Chen

294

Activities of ABT-773 against Listeria monocytogenes and Coryneform Bacteria of Clinical Interest  

Science.gov (United States)

The in vitro activities of ABT-773 were evaluated against 15 Listeria monocytogenes strains and 196 coryneform bacteria isolated from clinical samples. One hundred percent of the L. monocytogenes strains were inhibited by ?0.015 ?g of ABT-773/ml. MICs of ABT-773 (?g/ml) at which 50% of the isolates tested were inhibited (MIC50s) and MIC90s for other organisms were 0.125 and 0.5 (Corynebacterium amycolatum), 1 and >32 (Corynebacterium jeikeium), 0.03 and >32 (Corynebacterium minutissimum), >32 and >32 (Corynebacterium pseudodiphtheriticum and Corynebacterium urealyticum), 0.125 and >32 (Corynebacterium striatum), and 0.03 and 0.5 (Rhodococcus equi), respectively.

Conejo, Maria del Carmen; Martinez-Martinez, Luis; Pascual, Alvaro; Suarez, Ana Isabel; Perea, Evelio J.

2003-01-01

295

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

UK PubMed Central (United Kingdom)

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

Conejo Mdel C; Martínez-Martínez L; Pascual A; Suárez AI; Perea EJ

2003-04-01

296

Free radical-induced liver injury. II. Effects of intraperitoneally administered 2,2'-azobis(2-amidinopropane) dihydrochloride on the fatty acid profiles of hepatic triacylglycerol and phospholipids.  

UK PubMed Central (United Kingdom)

Liver injury induced by the radical initiator, 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) and carbon tetrachloride (CCI4) was examined by the analysis of lipids in the liver of rats. Increased triacylglycerol (TAG) was found in the liver within 24 hr following injection of these drugs. In AAPH-treated and CCI4-treated rats, it was 2.1 and 1.8 times that in the controls, respectively. TAG-palmitate and -oleate were found at particularly increased levels, while polyunsaturated fatty acid profiles of hepatic phospholipids were essentially the same for the treated and untreated rats. It is evident from these findings that radical initiators cause no decrease in polyunsaturated fatty acids in hepatic lipids, but accumulate TAG in the liver. Such a condition is the equivalent of liver injury in the rats in whose diets vitamin E has long been deficient.

Shimasaki H; Saypil WH; Ueta N

1991-01-01

297

A new acylated flavone glycoside with antioxidant and radical scavenging activities from Teucrium polium leaves.  

UK PubMed Central (United Kingdom)

The antioxidant properties of six flavones from Teucrium polium L., one of them isolated for the first time, have been established through the determination of their abilities to inhibit free radicals using DPPH, ABTS radicals and ORAC test. The structure of the new metabolite has been elucidated by 1-D (1H, 13C and DEPT) and 2-D (COSY, TOCSY, HSQC, CIGAR) NMR experiments and by ESI Q-TOF HRMS analysis. Flavones 1-3 presented an efficacious activity towards the stable DPPH radical. Analogously, compounds 2 and 3 resulted significantly active also versus ABTS cation radical. On the basis of the comparable bioactivity of luteolin-based compounds, the presence of an ortho-dihydroxy substitution in the flavone B-ring is supposed to be the structural feature responsible for the antioxidant activity.

D'Abrosca B; Pacifico S; Scognamiglio M; D'Angelo G; Galasso S; Monaco P; Fiorentino A

2013-03-01

298

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

UK PubMed Central (United Kingdom)

ABT-384 is a potent, selective inhibitor of 11-beta-hydroxysteroid dehydrogenase type 1 (HSD-1). One milligram of ABT-384 daily fully inhibited hepatic HSD-1. Establishing the dose that fully inhibits central nervous system (CNS) HSD-1 would enable definitive clinical studies in potential CNS indications. [9,11,12,12-(2)H4] cortisol (D4 cortisol), a stable labeled tracer, was used to characterize HSD-1 inhibition by ABT-384. D4 cortisol and its products were measured in the plasma and cerebrospinal fluid (CSF) of healthy male volunteers during D4 cortisol infusions, for up to 40?h after five daily doses of 1-50?mg ABT-384. Similar procedures were conducted in control subjects who received no ABT-384. Peripheral HSD-1 inhibition was calculated from plasma levels of D4 cortisol and its products. CNS HSD-1 inhibition was characterized from plasma and CSF levels of D4 cortisol and its products. ABT-384 regimens ?2?mg daily maintained peripheral HSD-1 inhibition ?88%. ABT-384 1?mg daily maintained peripheral HSD-1 inhibition ?81%. No CNS formation of D3 cortisol (the mass-labeled product of HSD-1) was detected following ABT-384 ?2?mg daily, indicating full CNS HSD-1 inhibition by these regimens. Partial CNS HSD-1 inhibition was associated with 1?mg ABT-384 daily. CNS HSD-1 inhibition was characterized by strong hysteresis and increased with maximum post-dose plasma concentration of ABT-384 and its active metabolites. ABT-384 has a wide potential therapeutic window for potential indications including Alzheimer's disease and major depressive disorder. Stable labeled substrates may be viable tools for measuring CNS effect during new drug development for other enzyme targets.

Katz DA; Liu W; Locke C; Jacobson P; Barnes DM; Basu R; An G; Rieser MJ; Daszkowski D; Groves F; Heneghan G; Shah A; Gevorkyan H; Jhee SS; Ereshefsky L; Marek GJ

2013-01-01

299

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

Science.gov (United States)

ABT-384 is a potent, selective inhibitor of 11-beta-hydroxysteroid dehydrogenase type 1 (HSD-1). One milligram of ABT-384 daily fully inhibited hepatic HSD-1. Establishing the dose that fully inhibits central nervous system (CNS) HSD-1 would enable definitive clinical studies in potential CNS indications. [9,11,12,12-2H4] cortisol (D4 cortisol), a stable labeled tracer, was used to characterize HSD-1 inhibition by ABT-384. D4 cortisol and its products were measured in the plasma and cerebrospinal fluid (CSF) of healthy male volunteers during D4 cortisol infusions, for up to 40?h after five daily doses of 1–50?mg ABT-384. Similar procedures were conducted in control subjects who received no ABT-384. Peripheral HSD-1 inhibition was calculated from plasma levels of D4 cortisol and its products. CNS HSD-1 inhibition was characterized from plasma and CSF levels of D4 cortisol and its products. ABT-384 regimens ?2?mg daily maintained peripheral HSD-1 inhibition ?88%. ABT-384 1?mg daily maintained peripheral HSD-1 inhibition ?81%. No CNS formation of D3 cortisol (the mass-labeled product of HSD-1) was detected following ABT-384 ?2?mg daily, indicating full CNS HSD-1 inhibition by these regimens. Partial CNS HSD-1 inhibition was associated with 1?mg ABT-384 daily. CNS HSD-1 inhibition was characterized by strong hysteresis and increased with maximum post-dose plasma concentration of ABT-384 and its active metabolites. ABT-384 has a wide potential therapeutic window for potential indications including Alzheimer's disease and major depressive disorder. Stable labeled substrates may be viable tools for measuring CNS effect during new drug development for other enzyme targets.

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

2013-01-01

300

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

Science.gov (United States)

ABT-384 is a potent, selective inhibitor of 11-beta-hydroxysteroid dehydrogenase type 1 (HSD-1). One milligram of ABT-384 daily fully inhibited hepatic HSD-1. Establishing the dose that fully inhibits central nervous system (CNS) HSD-1 would enable definitive clinical studies in potential CNS indications. [9,11,12,12-(2)H4] cortisol (D4 cortisol), a stable labeled tracer, was used to characterize HSD-1 inhibition by ABT-384. D4 cortisol and its products were measured in the plasma and cerebrospinal fluid (CSF) of healthy male volunteers during D4 cortisol infusions, for up to 40?h after five daily doses of 1-50?mg ABT-384. Similar procedures were conducted in control subjects who received no ABT-384. Peripheral HSD-1 inhibition was calculated from plasma levels of D4 cortisol and its products. CNS HSD-1 inhibition was characterized from plasma and CSF levels of D4 cortisol and its products. ABT-384 regimens ?2?mg daily maintained peripheral HSD-1 inhibition ?88%. ABT-384 1?mg daily maintained peripheral HSD-1 inhibition ?81%. No CNS formation of D3 cortisol (the mass-labeled product of HSD-1) was detected following ABT-384 ?2?mg daily, indicating full CNS HSD-1 inhibition by these regimens. Partial CNS HSD-1 inhibition was associated with 1?mg ABT-384 daily. CNS HSD-1 inhibition was characterized by strong hysteresis and increased with maximum post-dose plasma concentration of ABT-384 and its active metabolites. ABT-384 has a wide potential therapeutic window for potential indications including Alzheimer's disease and major depressive disorder. Stable labeled substrates may be viable tools for measuring CNS effect during new drug development for other enzyme targets. PMID:23982627

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

2013-08-27

 
 
 
 
301

In vitro and in vivo enhancement of chemoradiation using the oral PARP inhibitor ABT-888 in colorectal cancer cells.  

UK PubMed Central (United Kingdom)

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(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 JW; Waxweiler TV; Landry J; Gao H; Xu Y; Wang L; El-Rayes B; Shu HK

2013-07-01

302

Catalytic ozonation of 2,4-dichlorophenoxyacetic acid using alumina in the presence of a radical scavenger.  

Science.gov (United States)

Using a laboratory-scale mixed reactor, the performance of alumina in degrading 2,4-Dichlorophenoxyacetic acid with ozone in the presence of tert-butyl alcohol radical scavenger was studied. The operating variables investigated were the dose of alumina catalyst and solution pH. Results showed that using ozone and alumina leads to a significant increase in 2,4-D removal in comparison to non-catalytic ozonation and adsorption processes. The observed reaction rate constants (k(obs)) for 2,4-D during ozonation were found to increase linearly with increasing catalyst dose. At pH 5, the k(obs) value increased from 19.3 to 26 M(-1) s(-1) and 67 M(-1) s(-1) when varying the alumina dose from 1 to 2 and 4 g L(-1), respectively. As pH was increased, higher reaction rates were observed for both non-catalytic ozonation and catalytic ozonation processes. Thus, at pH 3 and using a catalyst dose of 8 g L(-1), the k(obs) values for non-catalytic ozonation and catalytic ozonation processes were 3.4 and 58.9 M(-1) s(-1), respectively, whereas at pH 5 reaction rate constants of 6.5 and 128.5 M(-1) s(-1) were observed, respectively. Analysis of total organic carbon suggested that catalytic ozonation with alumina achieved a considerable level of mineralization of 2,4-D. Adsorption of 2,4-D on alumina was found to play an important role in the catalytic ozonation process. PMID:22494378

Guzman-Perez, Carlos A; Soltan, Jafar; Robertson, Jared

2012-01-01

303

Catalytic ozonation of 2,4-dichlorophenoxyacetic acid using alumina in the presence of a radical scavenger.  

UK PubMed Central (United Kingdom)

Using a laboratory-scale mixed reactor, the performance of alumina in degrading 2,4-Dichlorophenoxyacetic acid with ozone in the presence of tert-butyl alcohol radical scavenger was studied. The operating variables investigated were the dose of alumina catalyst and solution pH. Results showed that using ozone and alumina leads to a significant increase in 2,4-D removal in comparison to non-catalytic ozonation and adsorption processes. The observed reaction rate constants (k(obs)) for 2,4-D during ozonation were found to increase linearly with increasing catalyst dose. At pH 5, the k(obs) value increased from 19.3 to 26 M(-1) s(-1) and 67 M(-1) s(-1) when varying the alumina dose from 1 to 2 and 4 g L(-1), respectively. As pH was increased, higher reaction rates were observed for both non-catalytic ozonation and catalytic ozonation processes. Thus, at pH 3 and using a catalyst dose of 8 g L(-1), the k(obs) values for non-catalytic ozonation and catalytic ozonation processes were 3.4 and 58.9 M(-1) s(-1), respectively, whereas at pH 5 reaction rate constants of 6.5 and 128.5 M(-1) s(-1) were observed, respectively. Analysis of total organic carbon suggested that catalytic ozonation with alumina achieved a considerable level of mineralization of 2,4-D. Adsorption of 2,4-D on alumina was found to play an important role in the catalytic ozonation process.

Guzman-Perez CA; Soltan J; Robertson J

2012-01-01

304

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)

2004-01-01

305

An antiapoptotic BCL-2 family expression index predicts the response of chronic lymphocytic leukemia to ABT-737  

Science.gov (United States)

The antiapoptotic BCL-2 proteins regulate lymphocyte survival and are over-expressed in lymphoid malignancies, including chronic lymphocytic leukemia. The small molecule inhibitor ABT-737 binds with high affinity to BCL-2, BCL-XL, and BCL-W but with low affinity to MCL-1, BFL-1, and BCL-B. The active analog of ABT-737, navitoclax, has shown a high therapeutic index in lymphoid malignancies; developing a predictive marker for it would be clinically valuable for patient selection or choice of drug combinations. Here we used RT-PCR as a highly sensitive and quantitative assay to compare expression of antiapoptotic BCL-2 genes that are known to be targeted by ABT-737. Our findings reveal that the relative ratio of MCL-1 and BFL-1 to BCL-2 expression provides a highly significant linear correlation with ABT-737 sensitivity (r = 0.6, P < .001). In contrast, antiapoptotic transcript levels, used individually or in combination for high or low affinity ABT-737-binding proteins, could not predict ABT-737 sensitivity. The (MCL-1 + BFL-1)/BCL-2 ratio was validated in a panel of leukemic cell lines subjected to genetic and pharmacologic manipulations. Changes after ABT-737 treatment included increased expression of BFL-1 and BCL-B that may contribute to treatment resistance. This study defines a highly significant BCL-2 expression index for predicting the response of CLL to ABT-737.

Al-harbi, Sayer; Hill, Brian T.; Mazumder, Suparna; Singh, Kamini; DeVecchio, Jennifer; Choudhary, Gaurav; Rybicki, Lisa A.; Kalaycio, Matt; Maciejewski, Jaroslaw P.; Houghton, Janet A.

2011-01-01

306

ABT-737 promotes tBid mitochondrial accumulation to enhance TRAIL-induced apoptosis in glioblastoma cells  

Digital Repository Infrastructure Vision for European Research (DRIVER)

To search for novel strategies to enhance the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis pathways in glioblastoma, we used the B-cell lymphoma 2/Bcl2-like 2-inhibitor ABT-737. Here we report that ABT-737 and TRAIL cooperate to induce apoptosis in several gliobl...

Cristofanon, S; Fulda, S

307

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 (25, 50 and 100 mg/l) added to humic acid samples and then absorption of samples was measured at 254 nm by using UV-Vis spectrophotometer before and after the electron beam irradiation. This study has done at pH= 8 and at different electron beam adsorbed dose of 1, 3, 6, 9 and 15 kGy. Results: The results of this study showed that the increasing of adsorbed dose from 1 to 15 kGy, the removal efficiency of humic acid also increased. By increasing of nitrate concentration from 25 to 100 mg/l, the removal efficiency of humic acid has decreased from 43.8% to 36.6% and nitrate acts as a radical scavenger. By increasing of humic acid concentration from 10 to 50mg/l, removal efficiency decreased in all adsorbed doses. Kinetic analysis of our results showed that the results well fitted with the second - order reaction. Conclusion: We can conclude from this study that electron beam irradiation could be a useful process for the treatment of natural organic matter (humic acid) from surface waters.

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

2013-01-01

308

Differentiation between stoichiometric and anticatalytic antioxidant properties of benzoic acid analogues: a structure/redox potential relationship study.  

UK PubMed Central (United Kingdom)

We investigated the antioxidant activities of some phenolic acid derivatives on a cell free system and on cellular and enzymatic models involved in inflammation. The stoichiometric antioxidant activities of phenolic acid derivatives were studied by measuring their capacity to scavenge the radical cation 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS(•+)) and reactive oxygen species (ROS) produced by stimulated neutrophils. The anticatalytic antioxidant capacity of the molecules was evaluated on the activity of myeloperoxidase (MPO), an oxidant enzyme present in and released by the primary granules of neutrophils. The ROS produced by PMA-stimulated neutrophils was measured by lucigenin-enhanced chemiluminescence (CL) and the potential interaction of the molecules with MPO was investigated without interferences due to medium by Specific Immuno-Extraction Followed by Enzyme Detection (SIEFED). The antioxidant activities of the phenolic compounds were correlated to their redox potentials measured by differential pulse voltammetry (DPV), and discussed in relation to their molecular structure. The ability of the phenolic molecules to scavenge ABTS radicals and ROS derived from neutrophils was inversely correlated to their increased redox potential. The number of hydroxyl groups (three) and their position (catechol) were essential for their efficacy as stoichiometric antioxidants or scavengers. On MPO activity, the inhibitory capacity of the molecules was not really correlated with their redox potential. Likewise, for the inhibition of MPO activity the number of OH groups and mainly the elongation of the carboxylic group were essential, probably by facilitating the interaction with the active site or the structure of the enzyme. The redox potential measurement, combined with ABTS and CL techniques, seems to be a good technique to select stoichiometric antioxidants but not anticatalytic ones, as seen for MPO, what rather involves a direct interaction with the enzyme.

Franck T; Mouithys-Mickalad A; Robert T; Ghitti G; Deby-Dupont G; Neven P; Serteyn D

2013-09-01

309

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

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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%, 0.1mM: 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%, 0.1mM: 66.32(±0.38)%; OH%,0.1mM: 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

2013-07-15

310

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

UK PubMed Central (United Kingdom)

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%, 0.1mM: 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%, 0.1mM: 66.32(±0.38)%; OH%,0.1mM: 92.51(±0.44)%; LOX: IC50=48.52(±0.88)?M).

Tarushi A; Karaflou Z; Kljun J; Turel I; Psomas G; Papadopoulos AN; Kessissoglou DP

2013-07-01

311

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

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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 sensitivit...

Dorota Martysiak-?urowska; Weronika Wenta

312

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 Muñoz; Edwin J. Bottia; Carol Y. Cardenas; Jose G. Patiño; Olga L. Díaz; Jairo R. Martínez; Vladímir V. Kouznetsov; Elena E. Stashenko

2007-01-01

313

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

314

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

UK PubMed Central (United Kingdom)

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.

Hannachi H; Elfalleh W; Marzouk S

2013-05-01

315

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

Science.gov (United States)

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

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

2012-09-07

316

Lidocaine: an inhibitor in the free-radical-induced hemolysis of erythrocytes.  

UK PubMed Central (United Kingdom)

Lidocaine was reported to protect erythrocytes from hemolysis induced by 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH). Since AAPH-induced hemolysis was a convenient in vitro experimental system to mimic erythrocytes undergoing peroxyl radicals attack, the aim of this work was to investigate the antioxidant effect of lidocaine on AAPH-induced hemolysis by chemical kinetics. As a result, one molecule of lidocaine can only trap 0.37 radical, much lower than melatonin. Meanwhile, lidocaine cannot protect erythrocytes from hemolysis induced by hemin, which the mechanism of hemolysis was due to the erythrocyte membrane destroyed by hemin. Accordingly, lidocaine protected erythrocytes by scavenging radicals preferentially rather than by stabilizing membrane. Moreover, the interactions of lidocaine with two radical species, including 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) radical cation (ABTS(+*)) and 2,2'-diphenyl-1-picrylhydrazyl (DPPH), indicated that lidocaine can reduce ABTS(+*) with 260 microM as the 50% inhibition concentration (IC(50)) and cannot react with DPPH. Thus, lidocaine served as a reductant rather than a hydrogen donor to interact with radicals. Finally, the quantum calculation proved that, compared with the melatonin radical, the stabilization of N-centered radical of lidocaine was higher than the amide-type N-centered radical but lower than the indole-type N-centered radical in melatonin. These results provided basic information for lidocaine to be an antiradical drug.

Tang YZ; Liu ZQ; Wu D

2009-03-01

317

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

2012-11-02

318

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

UK PubMed Central (United Kingdom)

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.

Li YW; Li B

2013-02-01

319

Phase 2 study of ABT-510 in patients with previously untreated advanced renal cell carcinoma.  

UK PubMed Central (United Kingdom)

PURPOSE: Angiogenesis is a characteristic of renal cell carcinoma. ABT-510 is an angiogenesis inhibitor that mimics the antiangiogenic properties of thrombospondin-1. This study was designed to assess the safety and efficacy of ABT-510 in patients with advanced renal cell carcinoma. EXPERIMENTAL DESIGN: Patients with previously untreated metastatic or unresectable renal cell carcinoma were randomized to treatment with one of two doses of ABT-510, self-administered s.c. twice daily in 28-day treatment periods without intervening rest periods. End points were progression-free survival (PFS), objective response rate, overall survival, and toxicity. RESULTS: The objective response rate was 4% in the 10 mg twice daily group, and there were two unconfirmed PRs in the 100 mg twice daily group. Respective median PFS was 4.2 and 3.3 months, with a 6-month PFS of 39% and 32%. Median overall survival was 27.8 months (10 mg twice daily) and 26.1 months (100 mg twice daily). The most frequent adverse events were injection site reactions (84%), fatigue (50%), headache (20%), and nausea (19%). The incidence of treatment-related, grade 3/4 adverse events was low and included three bleeding episodes (gastrointestinal hemorrhage, intracranial hemorrhage, and hemoptysis) and one thrombotic event (deep vein thrombosis). No deaths were attributed to ABT-510. CONCLUSIONS: There was little evidence of clinical activity for ABT-510, and further evaluation as a single agent for treating advanced renal cell carcinoma is not warranted. The evidence of a favorable safety profile may justify further evaluation in combination therapy.

Ebbinghaus S; Hussain M; Tannir N; Gordon M; Desai AA; Knight RA; Humerickhouse RA; Qian J; Gordon GB; Figlin R

2007-11-01

320

A phase II study of ABT-510 (thrombospondin-1 analog) for the treatment of metastatic melanoma.  

UK PubMed Central (United Kingdom)

OBJECTIVES: Thrombospondins are natural inhibitors of angiogenesis, tumor metastases, and tumor growth (melanoma). ABT-510 is a synthetic analog of thrombospondin-1, well tolerated in phase I studies. We conducted a phase II trial evaluating the clinical efficacy of ABT-510 and its effects on biomarkers of angiogenesis and immunity in patients with metastatic melanoma (MM). PATIENTS AND METHODS: A 2-stage phase II clinical trial was conducted to assess the clinical efficacy, safety, and pharmacodynamic effects (angiogenesis and immunity) of ABT-510 in patients with stage IV melanoma. The primary endpoint was 18-week treatment failure rate. Patients self-administered 100 mg of ABT-510 subcutaneously twice daily. Blood samples were collected at baseline and every 3 weeks while on therapy. Eligible patients demonstrated measurable disease, good performance status and no evidence of intracranial metastases. Correlative laboratory studies evaluated biomarkers of angiogenesis and immunity. RESULTS: Twenty-one patients were enrolled. Most patients were stage M1c (71%) and all had prior therapy for MM. Only 3 of the first 20 patients enrolled were progression free and on treatment at 18 weeks resulting in early termination of the study. Decreases in peripheral blood VEGF-A levels and VEGF-C levels, and CD146 and CD34/133 counts relative to pretreatment were detected. Limited changes in antitumor T cell immunity were observed. CONCLUSIONS: ABT-510 therapy administered at 100 mg twice/day in patients with MM did not demonstrate definite clinical efficacy. Further dose escalation or combination with cytotoxic therapy may be more effective therapeutically.

Markovic SN; Suman VJ; Rao RA; Ingle JN; Kaur JS; Erickson LA; Pitot HC; Croghan GA; McWilliams RR; Merchan J; Kottschade LA; Nevala WK; Uhl CB; Allred J; Creagan ET

2007-06-01

 
 
 
 
321

Measurements of nitrous acid, nitrate radicals, formaldehyde, and nitrogen dioxide for the Southern California Air Quality Study by differential optical-absorption spectroscopy. Final report  

Energy Technology Data Exchange (ETDEWEB)

Two differential optical absorption spectrometer (DOAS) systems were operated during the 1987 Southern California Air Quality Study (SCAQS) for the primary purpose of measuring atmospheric concentrations of nitrous acid (HONO) and the nitrate (NO3) radical, as well as ambient levels of nitrogen dioxide (NO2) and formaldehyde (HCHO). Measurements were conducted at Long Beach and Claremont, California, during the summer phase of the program and at Long Beach during the fall episodes. An extensive set of time-resolved (i.e., 15 min) measurements of HONO, NO2 and HCHO concentrations, as well as NO3 radical concentrations, were obtained during the SCAQS program by the DOAS technique under a wide range of pollutant and meteorological conditions.

Winer, A.M.; Biermann, H.W.; Dinoff, T.; Parker, L.; Poe, M.P.

1989-12-01

322

Damage of aromatic amino acids by the atmospheric free radical oxidant NO3? in the presence of NO2?, N2O4, O3 and O2.  

Science.gov (United States)

Analysis of the products formed in the reaction of NO(3)? with the N- and C-protected aromatic amino acids 1-5, which was performed under conditions that simulate exposure of biosurfaces to environmental pollutants, revealed insight how this important atmospheric free-radical oxidant can cause irreversible damage. In general, NO(3)? induced electron transfer at the aromatic ring is the exclusive initial pathway in a multi-step sequence, which ultimately leads to nitroaromatic compounds. In the reaction of NO(3)? with tryptophan 5 tricyclic products 12 and 13 are formed through an intramolecular, oxidative cyclization involving the amide moiety. In addition to this, strong indication for formation of N-nitrosamides was obtained, which likely result from reaction with N(2)O(4) through an independent non-radical pathway. PMID:21412525

Goeschen, Catrin; Wibowo, Natalia; White, Jonathan M; Wille, Uta

2011-03-16

323

Damage of aromatic amino acids by the atmospheric free radical oxidant NO3? in the presence of NO2?, N2O4, O3 and O2.  

UK PubMed Central (United Kingdom)

Analysis of the products formed in the reaction of NO(3)? with the N- and C-protected aromatic amino acids 1-5, which was performed under conditions that simulate exposure of biosurfaces to environmental pollutants, revealed insight how this important atmospheric free-radical oxidant can cause irreversible damage. In general, NO(3)? induced electron transfer at the aromatic ring is the exclusive initial pathway in a multi-step sequence, which ultimately leads to nitroaromatic compounds. In the reaction of NO(3)? with tryptophan 5 tricyclic products 12 and 13 are formed through an intramolecular, oxidative cyclization involving the amide moiety. In addition to this, strong indication for formation of N-nitrosamides was obtained, which likely result from reaction with N(2)O(4) through an independent non-radical pathway.

Goeschen C; Wibowo N; White JM; Wille U

2011-05-01

324

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

UK PubMed Central (United Kingdom)

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.

Venditti A; Mandrone M; Serrilli AM; Bianco A; Iannello C; Poli F; Antognoni F

2013-07-01

325

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

2013-07-08

326

Photochemistry and radiation chemistry of sulfur-containing amino acids. A new reaction of the 1-propenylthiyl radicals  

International Nuclear Information System (INIS)

In connection with food-flavor deterioration caused by uv or ? irradiation, a new reaction of the 1-propenylthiyl radicals from S-(cis-1-propenyl)-L-cysteine irradiated by uv ray or ?-ray in oxygen-free aqueous solutions was investigated. The main products, formed via 1-propenylthiyl radicals, in uv photolysis were 1-propene-1-thiol, 2,4-dimethylthiophene, 3,4-dimethylthiophene, and 3-methylthiophene, while ? radiolysis yielded 1-propene-1-thiol, n-propyl 1-propenyl sulfide (cis and trans), and di-1-propenyl sulfide (cis,cis and cis,trans). Furthermore, cis-trans isomerization of 1-propenylthiyl radicals plays an important role in the formation of these products. (U.S.)

1975-05-30

327

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

UK PubMed Central (United Kingdom)

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

Salamone M; Mangiacapra L; DiLabio GA; Bietti M

2013-01-01

328

The efficacy of cashew nut (Anacardium occidentale L.) skin extract as a free radical scavenger  

UK PubMed Central (United Kingdom)

The free radical scavenging activity of ethanolic extracts of cashew nut (Anacardium occidentale, L.) skin powder (CSP) was evaluated by employing various in vitro antioxidant assay systems. The yield of the extract as well as the total phenolic content was also determined. The yield of ethanolic extract of the skin powder was quite high (0.45 g/g powder) with a total phenolic content of 243 mg/g extract. The cashew nut skin extract (CSE) demonstrated promising antioxidant activity with EC50 of 1.30 ± 0.02 microgram/ml in 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging assay, 10.69 ± 1.13 microgram/ml in superoxide scavenging assay, 17.70 ± 0.05 microgram/ml in deoxyribose oxidation assay, 24.66 ± 0.32 microgram/ml in lipid peroxidation (LPO) assay and 6.00 mg/ml in iron chelation assay. To identify the compounds in the CSE responsible for the antioxidant activity, thin layer chromatography (TLC) was performed with the extract. The spot showing protection towards ?-carotene bleaching was extracted and analyzed by high performance liquid chromatography (HPLC); epicatechin was found to be the major polyphenol present. The results of the present study suggest that cashew nut skin, a byproduct of cashew processing industry, can be used as an economical source of natural antioxidants.

Kamath V; Rajini PS

2007-01-01

329

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

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

Stamelos Vasileios A; Redman Charles W; Richardson Alan

2012-01-01

330

BioRID dummy responses in matched ABTS and conventional seat tests on the IIHS rear sled.  

UK PubMed Central (United Kingdom)

OBJECTIVE: This study analyzed matched rear sled tests with all belts to seat (ABTS) and conventional seats from the same vehicle model to determine differences in BioRID IIg dummy responses. METHODS: The BioRID IIg rear impact dummy was placed on ABTS or conventional seats and subjected to 10 mph rear sled tests using the Insurance Institute for Highway Safety (IIHS) whiplash assessment protocol. Measurements in the dummy included head and pelvis triaxial accelerations, T1 and L1 biaxial accelerations, and upper and lower neck triaxial forces and moments. High-speed video captured the dummy and seat kinematics during seat loading and rebound into the lap-shoulder belts. Four vehicles were available with conventional and ABTS seats in the same model. They were the 2007-2008 Chrysler Sebring, 2006 Ford F-150, 2005-2007 Saab 9-3, and 2006-2007 BMW 3 series. Confidence intervals were used to determine significant differences between the matched ABTS and conventional seat responses. RESULTS: Ten sled tests were available for the 4 vehicle models with ABTS and conventional seats. The upper neck rearward shear force was 75 percent higher (range 17%-156%, P < .05) in the matched ABTS compared to conventional seats. The upper neck tension was 44 percent higher (range 24%-94%, P < .05) and the lower neck extension moment was 102 percent higher (range 38%-187%, P < .05). The Saab 9-3 responses were lower than the 3 other vehicles for both the conventional and ABTS seats. There was less rearward shear and extension of the neck in the Saab seats. CONCLUSIONS: The tests show that ABTS seats involved significantly higher neck tensions, rearward shear forces, and extension moments than matched conventional seats. Overall, ABTS seats applied more load on the head and spine, had less control of neck kinematics, and had higher risks for whiplash and more severe injury than conventional seats in the same vehicle model.

Viano DC; Parenteau CS

2011-08-01

331

ABT-737 promotes tBid mitochondrial accumulation to enhance TRAIL-induced apoptosis in glioblastoma cells.  

UK PubMed Central (United Kingdom)

To search for novel strategies to enhance the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis pathways in glioblastoma, we used the B-cell lymphoma 2/Bcl2-like 2-inhibitor ABT-737. Here we report that ABT-737 and TRAIL cooperate to induce apoptosis in several glioblastoma cell lines in a highly synergistic manner (combination index <0.1). Interestingly, the concerted action of ABT-737 and TRAIL to trigger the accumulation of truncated Bid (tBid) at mitochondrial membranes is identified as a key underlying mechanism. ABT-737 and TRAIL cooperate to cleave BH3-interacting domain death agonist (Bid) into its active fragment tBid, leading to increased accumulation of tBid at mitochondrial membranes. Coinciding with tBid accumulation, the activation of Bcl2-associated X protein (Bax), loss of mitochondrial membrane potential, release of cytochrome-c and second mitochondria-derived activator of caspase (Smac) into the cytosol and caspase activation are strongly increased in cotreated cells. Of note, knockdown of Bid significantly decreases ABT-737- and TRAIL-mediated Bax activation and apoptosis. Also, caspase-3 silencing reduces ABT-737- and TRAIL-induced Bid cleavage and apoptosis, indicating that a caspase-3-driven, mitochondrial feedback loop contributes to Bid processing. Importantly, ABT-737 profoundly enhances TRAIL-triggered apoptosis in primary cultured glioblastoma cells derived from tumor material, underlining the clinical relevance. Also, ABT-737 acts in concert with TRAIL to suppress tumor growth in an in vivo glioblastoma model. In conclusion, the rational combination of ABT-737 and TRAIL cooperates to trigger tBid mitochondrial accumulation and apoptosis. This approach presents a promising strategy for targeting the apoptosis pathways in glioblastoma, which warrants further investigation.

Cristofanon S; Fulda S

2012-01-01

332

ABT-737 promotes tBid mitochondrial accumulation to enhance TRAIL-induced apoptosis in glioblastoma cells.  

Science.gov (United States)

To search for novel strategies to enhance the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis pathways in glioblastoma, we used the B-cell lymphoma 2/Bcl2-like 2-inhibitor ABT-737. Here we report that ABT-737 and TRAIL cooperate to induce apoptosis in several glioblastoma cell lines in a highly synergistic manner (combination index <0.1). Interestingly, the concerted action of ABT-737 and TRAIL to trigger the accumulation of truncated Bid (tBid) at mitochondrial membranes is identified as a key underlying mechanism. ABT-737 and TRAIL cooperate to cleave BH3-interacting domain death agonist (Bid) into its active fragment tBid, leading to increased accumulation of tBid at mitochondrial membranes. Coinciding with tBid accumulation, the activation of Bcl2-associated X protein (Bax), loss of mitochondrial membrane potential, release of cytochrome-c and second mitochondria-derived activator of caspase (Smac) into the cytosol and caspase activation are strongly increased in cotreated cells. Of note, knockdown of Bid significantly decreases ABT-737- and TRAIL-mediated Bax activation and apoptosis. Also, caspase-3 silencing reduces ABT-737- and TRAIL-induced Bid cleavage and apoptosis, indicating that a caspase-3-driven, mitochondrial feedback loop contributes to Bid processing. Importantly, ABT-737 profoundly enhances TRAIL-triggered apoptosis in primary cultured glioblastoma cells derived from tumor material, underlining the clinical relevance. Also, ABT-737 acts in concert with TRAIL to suppress tumor growth in an in vivo glioblastoma model. In conclusion, the rational combination of ABT-737 and TRAIL cooperates to trigger tBid mitochondrial accumulation and apoptosis. This approach presents a promising strategy for targeting the apoptosis pathways in glioblastoma, which warrants further investigation. PMID:23190604

Cristofanon, S; Fulda, S

2012-11-29

333

ABT-510 induces tumor cell apoptosis and inhibits ovarian tumor growth in an orthotopic, syngeneic model of epithelial ovarian cancer.  

UK PubMed Central (United Kingdom)

Epithelial ovarian cancer (EOC) is the fifth most common cancer in women and is characterized by a low 5-year survival rate. One strategy that can potentially improve the overall survival rate in ovarian cancer is the use of antitumor agents such as ABT-510. ABT-510 is a small mimetic peptide of the naturally occurring antiangiogenic compound thrombospondin-1 and has been shown to significantly reduce tumor growth and burden in preclinical mouse models and in naturally occurring tumors in dogs. This is the first evaluation of ABT-510 in a preclinical model of human EOC. Tumorigenic mouse surface epithelial cells were injected into the bursa of C57BL/6 mice that were treated with either 100 mg/kg ABT-510 or an equivalent amount of PBS. ABT-510 caused a significant reduction in tumor size, ascites fluid volume, and secondary lesion dissemination when compared with PBS controls. Analysis of the vasculature of ABT-510-treated mice revealed vascular remodeling with smaller diameter vessels and lower overall area, increased number of mature vessels, and decreased tissue hypoxia. Tumors of ABT-510-treated mice had a significantly higher proportion of apoptotic tumor cells compared with the PBS-treated controls. Immunoblot analysis of cell lysates revealed a reduction in vascular endothelial growth factor, vascular endothelial growth factor receptor-2, and proliferating cell nuclear antigen protein expression as well as expression of members of the phosphatidylinositol 3-kinase and mitogen-activated protein kinase survival pathways. In vitro, ABT-510 induced tumor cell apoptosis in mouse and human ovarian cancer cells. This study shows ABT-510 as a promising candidate for inhibiting tumor growth and ascites formation in human EOC.

Greenaway J; Henkin J; Lawler J; Moorehead R; Petrik J

2009-01-01

334

ABT-510 induces tumor cell apoptosis and inhibits ovarian tumor growth in an orthotopic, syngeneic model of epithelial ovarian cancer.  

Science.gov (United States)

Epithelial ovarian cancer (EOC) is the fifth most common cancer in women and is characterized by a low 5-year survival rate. One strategy that can potentially improve the overall survival rate in ovarian cancer is the use of antitumor agents such as ABT-510. ABT-510 is a small mimetic peptide of the naturally occurring antiangiogenic compound thrombospondin-1 and has been shown to significantly reduce tumor growth and burden in preclinical mouse models and in naturally occurring tumors in dogs. This is the first evaluation of ABT-510 in a preclinical model of human EOC. Tumorigenic mouse surface epithelial cells were injected into the bursa of C57BL/6 mice that were treated with either 100 mg/kg ABT-510 or an equivalent amount of PBS. ABT-510 caused a significant reduction in tumor size, ascites fluid volume, and secondary lesion dissemination when compared with PBS controls. Analysis of the vasculature of ABT-510-treated mice revealed vascular remodeling with smaller diameter vessels and lower overall area, increased number of mature vessels, and decreased tissue hypoxia. Tumors of ABT-510-treated mice had a significantly higher proportion of apoptotic tumor cells compared with the PBS-treated controls. Immunoblot analysis of cell lysates revealed a reduction in vascular endothelial growth factor, vascular endothelial growth factor receptor-2, and proliferating cell nuclear antigen protein expression as well as expression of members of the phosphatidylinositol 3-kinase and mitogen-activated protein kinase survival pathways. In vitro, ABT-510 induced tumor cell apoptosis in mouse and human ovarian cancer cells. This study shows ABT-510 as a promising candidate for inhibiting tumor growth and ascites formation in human EOC. PMID:19139114

Greenaway, James; Henkin, Jack; Lawler, Jack; Moorehead, Roger; Petrik, Jim

2009-01-01

335

The bis(allyl)bismuth cation: a reagent for direct allyl transfer by Lewis acid activation and controlled radical polymerization.  

Science.gov (United States)

A positive effect: the bis(allyl)bismuth cation in [Bi(C(3)H(5))(2)(thf)(2)][B(C(6)H(3)Cl(2))(4)] is superior to neutral tris(allyl)bismuth in the additive-free allylation of unsaturated C-heteroatom functionalities and the controlled living radical polymerization of activated olefins. PMID:23166056

Lichtenberg, Crispin; Pan, Fangfang; Spaniol, Thomas P; Englert, Ulli; Okuda, Jun

2012-11-14

336

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

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

Katty Wan; Matthew Rieser; Tawakol El-Shourbagy

2010-01-01

337

Effects of chloride ion on degradation of Acid Orange 7 by sulfate radical-based advanced oxidation process: implications for formation of chlorinated aromatic compounds.  

UK PubMed Central (United Kingdom)

Sodium chloride is a common salt used during textile wet processes. Here a dual effect of chloride (i.e. inhibitory and accelerating effect) on azo dye (Acid Orange 7, AO7) degradation in an emerging cobalt/peroxymonosulfate (Co/PMS) advanced oxidation process (AOP) was reported. Compared to OH-based AOPs, high concentrations of chloride (>5mM) can significantly enhance dye decoloration independent of the presence of the Co(2+) catalyst, but did greatly inhibit dye mineralization to an extent which was closely dependent upon the chloride content. Both UV-vis absorbance spectra and AOX determination indicated the formation of some refractory byproducts. Some chlorinated aromatic compounds, including 3-chloroisocoumain, 2-chloro-7-hydroxynaphthalene, 1,3,5-trichloro-2-nitrobenzene and tetrachlorohydroquione, were identified by GC-MS measurement in both Co/PMS/Cl(-) and PMS/Cl(-) reaction systems. Based on those experimental results, two possible branched (SO(4)(-)radical-based and non-radical) reaction pathways are proposed. This is one of the very few studies dealing with chlorinated organic intermediates formed via chlorine radical/active chlorine species (HOCl/Cl(2)) attack on dye compounds. Therefore, this finding may have significant technical implications for utilizing Co/PMS regent to detoxify chloride-rich azo dyes wastewater.

Yuan R; Ramjaun SN; Wang Z; Liu J

2011-11-01

338

Effects of chloride ion on degradation of Acid Orange 7 by sulfate radical-based advanced oxidation process: implications for formation of chlorinated aromatic compounds.  

Science.gov (United States)

Sodium chloride is a common salt used during textile wet processes. Here a dual effect of chloride (i.e. inhibitory and accelerating effect) on azo dye (Acid Orange 7, AO7) degradation in an emerging cobalt/peroxymonosulfate (Co/PMS) advanced oxidation process (AOP) was reported. Compared to OH-based AOPs, high concentrations of chloride (>5mM) can significantly enhance dye decoloration independent of the presence of the Co(2+) catalyst, but did greatly inhibit dye mineralization to an extent which was closely dependent upon the chloride content. Both UV-vis absorbance spectra and AOX determination indicated the formation of some refractory byproducts. Some chlorinated aromatic compounds, including 3-chloroisocoumain, 2-chloro-7-hydroxynaphthalene, 1,3,5-trichloro-2-nitrobenzene and tetrachlorohydroquione, were identified by GC-MS measurement in both Co/PMS/Cl(-) and PMS/Cl(-) reaction systems. Based on those experimental results, two possible branched (SO(4)(-)radical-based and non-radical) reaction pathways are proposed. This is one of the very few studies dealing with chlorinated organic intermediates formed via chlorine radical/active chlorine species (HOCl/Cl(2)) attack on dye compounds. Therefore, this finding may have significant technical implications for utilizing Co/PMS regent to detoxify chloride-rich azo dyes wastewater. PMID:21968121

Yuan, Ruixia; Ramjaun, Sadiqua N; Wang, Zhaohui; Liu, Jianshe

2011-09-19

339

Primary steps in the reaction of OH radicals with amino acids at low temperatures in Laval nozzle expansions: perspectives from experiment and theory.  

UK PubMed Central (United Kingdom)

Recent work has focused on the damaging effects of free radicals on biological molecules. This study investigates the kinetics of the attack of OH radicals on L-alanine ethyl ester in the gas phase in cold beams of Laval nozzle expansions. Experiments and high-level theory are used to understand the preferred site of attack by the OH radical. Optimizations of L-alanine and L-alanine ethyl ester show that the essential transition state features for hydrogen abstraction off the C(alpha), C(beta), and N are similar. The energetics show that for L-alanine, the C(alpha)-site, C(beta)-site, and N-site transition states are all below the reactants level. For L-alanine ethyl ester, however, the energetics for hydrogen abstraction off the C(alpha) and N are the preferred site of reaction. These findings are supported by the observed negative temperature dependence of the rate constants of OH with alanine ethyl ester in Laval nozzle expansion experiments. More importantly, both the experiments and theory show that L-alanine ethyl ester provides a good model for gas phase studies of the amino acids such as L-alanine.

Liessmann M; Hansmann B; Blachly PG; Francisco JS; Abel B

2009-07-01

340

Primary steps in the reaction of OH radicals with amino acids at low temperatures in Laval nozzle expansions: perspectives from experiment and theory.  

Science.gov (United States)

Recent work has focused on the damaging effects of free radicals on biological molecules. This study investigates the kinetics of the attack of OH radicals on L-alanine ethyl ester in the gas phase in cold beams of Laval nozzle expansions. Experiments and high-level theory are used to understand the preferred site of attack by the OH radical. Optimizations of L-alanine and L-alanine ethyl ester show that the essential transition state features for hydrogen abstraction off the C(alpha), C(beta), and N are similar. The energetics show that for L-alanine, the C(alpha)-site, C(beta)-site, and N-site transition states are all below the reactants level. For L-alanine ethyl ester, however, the energetics for hydrogen abstraction off the C(alpha) and N are the preferred site of reaction. These findings are supported by the observed negative temperature dependence of the rate constants of OH with alanine ethyl ester in Laval nozzle expansion experiments. More importantly, both the experiments and theory show that L-alanine ethyl ester provides a good model for gas phase studies of the amino acids such as L-alanine. PMID:19552478

Liessmann, Matthias; Hansmann, Björn; Blachly, Patrick G; Francisco, Joseph S; Abel, Bernd

2009-07-01

 
 
 
 
341

The herbicide 2,4-dichlorophenoxyacetic acid induces the generation of free-radicals and associated oxidative stress responses in yeast  

International Nuclear Information System (INIS)

[en] The pro-oxidant action of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is demonstrated in this study using Saccharomyces cerevisiae as a eukaryotic experimental model. Evidence is presented for the generation of hydroxyl-radicals, in yeast cells suddenly exposed to 2,4-D, detected by in vivo electron paramagnetic resonance (EPR) spectroscopy using 5,5'-dimethyl-1-pyrroline N-oxide and 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide as spin-traps. The intensity of the EPR spectra was dependent on the concentration of herbicide tested and was consistently higher in a mutant (?sod1) devoid of the cytosolic CuZn-superoxide dismutase. A time-course-dependent variation of the level of free-radical adducts was registered upon sudden exposure of an yeast cell population to concentrations of 2,4-D that lead to an initial period of viability loss, before resumption of inhibited growth by the viable adapted population. The variation pattern of the level of hydroxyl-radical adducts correlated with the one determined for the activity of Sod1p, cytosolic catalase Ctt1p, and the dithiol glutaredoxins Grx1p and Grx2p

2004-11-19

342

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

UK PubMed Central (United Kingdom)

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.

Shi H; Yang H; Zhang X; Yu LL

2012-12-01

343

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

2012-12-05

344

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.

Miglena Valyova; Stanimir Stoyanov; Yuliana Markovska; Yordanka Ganeva

2012-01-01

345

Comparative evaluation of post-column free radical scavenging and ferric reducing antioxidant power assays for screening of antioxidants in strawberries.  

UK PubMed Central (United Kingdom)

ABTS and FRAP post-column techniques evaluate the antioxidant characteristics of HPLC separated compounds with specific reagents. ABTS characterize their ability to scavenge free radicals by electron-donating antioxidants, resulting in the absorbance decrease of the chromophoric radical. FRAP - is based on the reduction of Fe(III)-tripyridyltriazine complex to Fe(II)-tripyridyltriazine at low pH by electron-donating antioxidants, resulting in an absorbance increase. Both post-column assays were evaluated and compared according to the following validation parameters: specificity, precision, limit of detection (LoD), limit of quantitation (LoQ) and linearity. ABTS and FRAP post-column assays were specific, repeatable and sensitive and thus can be used for the evaluation of antioxidant active compounds. Antioxidant active compounds were quantified according to TEAC for each assay and ABTS/FRAP ratio was derived. No previous records of antioxidative activity of leaves and fruits of strawberries (Fragaria viridis, Fragaria moschata) research have been found. The research results confirm the reliability of ABTS and FRAP post-column assays for screening of antioxidants in complex mixtures and the determination of radical scavenging and ferric reducing ability by their TEAC values.

Raudonis R; Raudone L; Jakstas V; Janulis V

2012-04-01

346

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

Science.gov (United States)

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

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

2003-04-01

347

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

Directory of Open Access Journals (Sweden)

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?; Rajka Božani?; Ljubica Tratnik

2010-01-01

348

A phase I study of ABT-510 plus bevacizumab in advanced solid tumors.  

UK PubMed Central (United Kingdom)

Targeting multiple regulators of tumor angiogenesis have the potential to improve treatment efficacy. Bevacizumab is a monoclonal antibody directed against vascular endothelial growth factor and ABT-510 is a synthetic analog of thrombospondin, an endogenous angiogenesis inhibitor. Dual inhibition may result in additional benefit. We evaluated the safety, tolerability, and efficacy of the combination of bevacizumab plus ABT-510 in patients with refractory solid tumors. We also explored the effects of these agents on plasma-based biomarkers and wound angiogenesis. Thirty-four evaluable subjects were enrolled and received study drug. Therapy was well tolerated; minimal treatment-related grade 3/4 toxicity was observed. One patient treated at dose level 1 had a partial response and five other patients treated at the recommended phase II dose had prolonged stable disease for more than 1 year. Biomarker evaluation revealed increased levels of D-dimer, von Willebrand factor, placental growth factor, and stromal-derived factor 1 in response to treatment with the combination of bevacizumab and ABT-510. Data suggest that continued evaluation of combination antiangiogenesis therapies may be clinically useful.

Uronis HE; Cushman SM; Bendell JC; Blobe GC; Morse MA; Nixon AB; Dellinger A; Starr MD; Li H; Meadows K; Gockerman J; Pang H; Hurwitz HI

2013-06-01

349

A phase I study of ABT-510 plus bevacizumab in advanced solid tumors.  

Science.gov (United States)

Targeting multiple regulators of tumor angiogenesis have the potential to improve treatment efficacy. Bevacizumab is a monoclonal antibody directed against vascular endothelial growth factor and ABT-510 is a synthetic analog of thrombospondin, an endogenous angiogenesis inhibitor. Dual inhibition may result in additional benefit. We evaluated the safety, tolerability, and efficacy of the combination of bevacizumab plus ABT-510 in patients with refractory solid tumors. We also explored the effects of these agents on plasma-based biomarkers and wound angiogenesis. Thirty-four evaluable subjects were enrolled and received study drug. Therapy was well tolerated; minimal treatment-related grade 3/4 toxicity was observed. One patient treated at dose level 1 had a partial response and five other patients treated at the recommended phase II dose had prolonged stable disease for more than 1 year. Biomarker evaluation revealed increased levels of D-dimer, von Willebrand factor, placental growth factor, and stromal-derived factor 1 in response to treatment with the combination of bevacizumab and ABT-510. Data suggest that continued evaluation of combination antiangiogenesis therapies may be clinically useful. PMID:23930208

Uronis, Hope E; Cushman, Stephanie M; Bendell, Johanna C; Blobe, Gerard C; Morse, Michael A; Nixon, Andrew B; Dellinger, Andrew; Starr, Mark D; Li, Haiyan; Meadows, Kellen; Gockerman, Jon; Pang, Herbert; Hurwitz, Herbert I

2013-03-21

350

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

351

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

Science.gov (United States)

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

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

2010-12-27

352

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

UK PubMed Central (United Kingdom)

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.

Sakuma Y; Tsunezumi J; Nakamura Y; Yoshihara M; Matsukuma S; Koizume S; Miyagi Y

2011-03-01

353

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

International Nuclear Information System (INIS)

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

2012-01-01

354

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

UK PubMed Central (United Kingdom)

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.

Liang CH; Chan LP; Ding HY; So EC; Lin RJ; Wang HM; Chen YG; Chou TH

2012-08-01

355

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

Science.gov (United States)

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

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

2009-03-11

356

Radiolytically-induced one-electron reduction of methyl viologen in aqueous solution. Stability of the radical cation in acidic and highly alkaline media  

Energy Technology Data Exchange (ETDEWEB)

Pulse and continuous radiolyses have been used to investigate the stability of the reduced methyl viologen radical cation (MV/sup +/) in acidic and highly alkaline aqueous solution. The reaction of the methyl viologen dication (MV/sup 2 +/) with (CH/sub 3/)/sub 2/COH and (CH/sub 3/)/sub 2/CO/sup -/ radicals generates MV/sup +/ rapidly. The absorption spectrum of MV/sup +/ is the same at pH 1, natural pH, and pH 13 suggesting that MV/sup +/ is not involved in acid-base equilibria in that pH range. Between pH 0 and 2, MV/sup +/ disappears via second-order kinetics with ksub(obs) an inverse function of (MV/sup 2 +/) and pH. The decay of MV/sup +/ occurs via H/sup +/-assisted disproportionation and yields ultimately a hydrogenated species with lambdasub(max) 220, 255 nm. At pH 13, MV/sup +/ is infinitely stable in the absence of O/sub 2/; further reduction of MV/sup +/ yields the moderately stable MV/sup 0/ species with lambdasub(max) 368 nm and a shoulder at 370 nm. Reaction of MV/sup 0/ with O/sub 2/ yields MV/sup 2 +/ quantitatively via two one-electron oxidation steps. Acidification of MV/sup 0/ in the absence of O/sub 2/ yields the same air-insensitive hydrogenation product as is obtained from the disproportionation of MV/sup +/ in acidic solution. The relationship of these observations to the use of MV/sup 2 +/ as an electron relay species in photochemical solar energy conversion schemes is examined.

Venturi, M. (Bologna Univ. (Italy). Ist. de Scienze Chimiche); Mulazzani, Q.G. (Consiglio Nazionale delle Ricerche, Bologna (Italy)); Hoffman, M.Z. (Boston Univ., MA (USA). Dept. of Chemistry)

1984-01-01

357

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

Directory of Open Access Journals (Sweden)

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

G. L. FREITAS; E. M. KUSKOSKI; L. GONZAGA; R. FETT

2009-01-01

358

Stress influenced increase in phenolic content and radical scavenging capacity of Rhodotorula glutinis CCY 20-2-26.  

UK PubMed Central (United Kingdom)

Rhodotorula glutinis CCY 20-2-26 when grown under controlled stress of either NaCl (1–5 %) or H2O2 (1–5 mM) on basal media exhibited a twofold increase in its total phenolic contents. The radical scavenging capacities (RSCs) as determined by ABTS test were found to be highest in 4 mM H2O2 (1.44 mM TEAC mg?1) and 4 % NaCl (1.13 mM TEAC mg?1) as compared to control samples (0.41 mM TEAC mg?1). Similarly, the RSCs as determined by DPPH test were also highest in 4 % NaCl (1.83 mM TEAC mg?1) and 4 mM H2O2 (1.78 mM TEAC mg?1) compared to control (0.48 TEAC mg?1). The relative RSCs from EPR spin-trapping assay for H2O2-stressed cultures were highest in 1 mM H2O2 (56.1 ?M TEAC g?1) whereas in NaCl-stressed cultures it was highest in 5 % NaCl (44.6 ?M TEAC g?1) as compared to control (30.9 ?M TEAC g?1). Five phenolic compounds (gallic acid, benzoic acid, catechin, caffeic acid and ferulic acid) were detected for the first time in R. glutinis CCY 20-2-26.

Salar RK; Certik M; Brezova V; Brlejova M; Hanusova V; Breierová E

2012-05-01

359

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

2011-01-01

360

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

UK PubMed Central (United Kingdom)

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.

Huang WY; Lee PC; Huang LK; Lu LP; Liao WC

2013-03-01

 
 
 
 
361

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

2013-01-30

362

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 identi...

Hülya Torun; Faik Ahmet Ayaz; Nesrin Colak; Ji?í Grúz; Miroslav Strnad

363

Ability of methanolic seed extracts of pawpaw (Asimina triloba) to inhibit n-3 fatty acid oxidation initiated by peroxyl radicals and reactive oxygen, nitrogen, and sulfur  

UK PubMed Central (United Kingdom)

Methanolic extracts from underripe, ripe, and ripe then dried pawpaw seeds (PPSE) were tested for antioxidative effectiveness. Underripe seeds contained more total phenolic compounds than ripe seeds, but ripe seeds showed the highest reducing potential. PPSE samples effectively scavenged DPPH (>86%). PPSE (0-26.8?M gallic acid) effectively inhibited lipid oxidation biomarkers in 22:6 phosphatidylcholine (PC) liposome suspensions over 7 day's incubation at room temperature. PPSE inhibited TBARS in 22:6 PC liposome suspensions induced by peroxyl radical generators, free radical generators that produce reactive oxygen, reactive nitrogen, and reactive sulfur species. After 120min of storage TBARS inhibition by PPSE was in the order of H?O? [greater-than or slanted equal to]SIN-1=DSSO=AAPH[greater-than or slanted equal to]Sulfite>ONOO=MMb>iron/ascorbate. PPSE inhibited lipid oxidation biomarkers in skeletal muscle homogenates induced by iron/ascorbate. The development of value added products from pawpaw seeds may lead to successful commercialisation of this underutilised fruit.

Brannan RobertG; Salabak DaneE

2009-05-01

364

Platinum compounds sensitize ovarian carcinoma cells to ABT-737 by modulation of the Mcl-1/Noxa axis.  

Science.gov (United States)

Ovarian cancer is the leading cause of death from gynecological cancer. The anti-apoptotic protein Bcl-x(L) is frequently overexpressed in ovarian carcinoma which correlates with chemotherapy resistance. It has been demonstrated that Bcl-x(L) cooperates with another anti-apoptotic protein, Mcl-1, to protect ovarian cancer cells against apoptosis, and that their concomitant inhibition induces massive cell death. Here, we examined the interest of ABT-737, a potent BH3-mimetic molecule targeting Bcl-x(L), both alone and in combination with Mcl-1 modulators, in ovarian cancer cell lines. As a single agent, ABT-737 was ineffective at promoting cell death in the four cell lines we tested in vitro. However, the specific inhibition of Mcl-1 by siRNA dramatically increased the sensitivity of chemoresistant cells to ABT-737. Platinum compounds also sensitize to ABT-737 by dose-dependently decreasing Mcl-1 expression or by increasing the expression of pro-apoptotic BH3-only proteins Noxa and, to a lower extent, Bim. Furthermore, we demonstrated that Noxa accumulation was involved in apoptosis occurring in response to the combination of ABT-737 and platinum compounds, since cells were protected from apoptosis by its silencing. Moreover, the combination was also highly cytotoxic ex vivo in sliced SKOV3 tumor nodes. However we observed in these slices a strong basal expression of Noxa and apoptotic cell death in response to ABT-737 alone. Therefore, we have revealed that the modulation of the Mcl-1/Noxa axis by platinum compounds results in a strong sensitization of chemoresistant ovarian carcinoma cells to ABT-737, which could constitute a promising therapeutic in these cancers. PMID:23344663

Simonin, Karin; N'Diaye, Monique; Lheureux, Stéphanie; Loussouarn, Claire; Dutoit, Soizic; Briand, Mélanie; Giffard, Florence; Brotin, Emilie; Blanc-Fournier, Cécile; Poulain, Laurent

2013-04-01

365

The isolation and identification of two compounds with predominant radical scavenging activity in hempseed (seed of Cannabis sativa L.).  

UK PubMed Central (United Kingdom)

Forty samples were extracted from defatted kernels and hulls of two varieties of hempseed (Bama and Yunma No. 1) using 10 different polar solvent systems. The radical scavenging capacity of the extracts was evaluated using 2,2-diphenyl-1-pikrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays and the total phenolic content was determined by Folin-Ciocalteu's phenol reagent. The correlation analysis indicated that the antioxidants in hempseed belonged to phenolic and DPPH() assay was suitable for evaluating the radical scavenging activity. Two compounds, with predominant antiradical activity, were isolated in 60% ethanol extract of hempseed hull using macroporous resin absorption, LH-20 gel chromatography, and high performance liquid chromatography methods, which were identified as N-trans-caffeoyltyramine and cannabisin B by high-resolution mass spectra, nuclear magnetic resonance spectra, and ultraviolet data. The two compounds exhibited significant high DPPH() scavenging activity and protective effect against in vitro oxidation of human low-density lipoprotein compared with extracts from flaxseed, grape seed, and soybean. This suggests that hempseed hull extract is a potential source of natural antioxidants, which could be added to dietary supplements to help prevent oxidative stress.

Chen T; He J; Zhang J; Li X; Zhang H; Hao J; Li L

2012-09-01

366

The isolation and identification of two compounds with predominant radical scavenging activity in hempseed (seed of Cannabis sativa L.).  

Science.gov (United States)

Forty samples were extracted from defatted kernels and hulls of two varieties of hempseed (Bama and Yunma No. 1) using 10 different polar solvent systems. The radical scavenging capacity of the extracts was evaluated using 2,2-diphenyl-1-pikrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) assays and the total phenolic content was determined by Folin-Ciocalteu's phenol reagent. The correlation analysis indicated that the antioxidants in hempseed belonged to phenolic and DPPH() assay was suitable for evaluating the radical scavenging activity. Two compounds, with predominant antiradical activity, were isolated in 60% ethanol extract of hempseed hull using macroporous resin absorption, LH-20 gel chromatography, and high performance liquid chromatography methods, which were identified as N-trans-caffeoyltyramine and cannabisin B by high-resolution mass spectra, nuclear magnetic resonance spectra, and ultraviolet data. The two compounds exhibited significant high DPPH() scavenging activity and protective effect against in vitro oxidation of human low-density lipoprotein compared with extracts from flaxseed, grape seed, and soybean. This suggests that hempseed hull extract is a potential source of natural antioxidants, which could be added to dietary supplements to help prevent oxidative stress. PMID:23107724

Chen, Tianpeng; He, Jinfeng; Zhang, Jianchun; Li, Xiaohui; Zhang, Hua; Hao, Jianxiong; Li, Lite

2012-03-12

367

Nitrogen Oxides in the Nocturnal Boundary Layer: Chemistry of Nitrous Acid (HONO) and the Nitrate Radical (N03)  

Energy Technology Data Exchange (ETDEWEB)

Summary Chemical processes occurring at night in the lowest part of the urban atmosphere, the so called nocturnal boundary layer (NBL), can influence the composition of the atmosphere during the night as well as the following day. They may impact the budgets of some of the most important pollutants, such as ozone and nitrogen oxides, as well as influence size and composition of particular matter. Few studies have thus far concentrated on the nocturnal chemistry of the urban NBL, most likely due to the strong influence of vertical transport and mixing, which requires the measurement of trace gas profiles instead of simple point observations. Motivated by our lack of observations and understanding of nocturnal chemistry, the focus of this project was the study of the vertical distribution of trace gases and the altitude dependence of nocturnal chemistry under polluted conditions through field observations and modeling studies. The analysis of three field experiments (TEXAQS, Houston, 2000; Phoenix Sunrise Ozone Experiment, 2001; NAPOX, Boston, 2002), two of which were performed in this project, showed that ozone concentrations typically increase with height in the lowest 150m, while NO2 typically decreases. NO3, the dominant nocturnal radical species, showed much higher concentrations in the upper part of the NBL, and was often not present at the ground. With the help of a one-dimensional chemical transport model, developed in this project, we found that the interaction of ground emissions of NOx and hydrocarbons, together with their vertical transport, is responsible for the vertical profiles. The dominant chemical reactions influencing ozone, NO2 and NO3 are the reaction of ozone and NO3 with freshly emitted NO. Sensitivity studies with our model showed that the magnitude of the trace gas gradients depend both on the emission rates and the vertical stability of the NBL. Observations and model analysis clearly show that nocturnal