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

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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...

CAROLA HENRIQUEZ; CAROLINA ALIAGA; EDUARDO LISSI

2004-01-01

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

Science.gov (United States)

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

Herraiz, Tomas; Galisteo, Juan

2004-03-01

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

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

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

2009-01-01

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

Directory of Open Access Journals (Sweden)

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

CAROLA HENRIQUEZ

2004-03-01

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

Scientific Electronic Library Online (English)

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

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

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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 the antioxidative behavior of the phenolics (caffeic acid, galangin and pinocembrin) most commonly present in Croatian propolis samples obtained from different Croatian regions. We propose a math...

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

2007-01-01

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

Scientific Electronic Library Online (English)

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

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

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

Science.gov (United States)

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

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

2014-07-01

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Doxorubicin inhibits oxidation of 2,2?-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) by a lactoperoxidase/H2O2 system by reacting with ABTS-derived radical  

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The effect of doxorubicin on oxidation of 2,2?-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) by lactoperoxidase and hydrogen peroxide has been investigated. It was found that: (1) oxidation of ABTS to its radical cation (ABTS•+) is inhibited by doxorubicin as evidenced by its induction of a lag period, duration of which depends on doxorubicin concentration; (2) the inhibition is due to doxorubicin hydroquinone reducing the ABTS•+ radical (stoichiometry 1: 1.8); (3) concomitant wi...

Reszka, Krzysztof J.; Britigan, Bradley E.

2007-01-01

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

Science.gov (United States)

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

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

2014-07-01

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Reactions of the melatonin metabolite N1-acetyl-5-methoxykynuramine (AMK) with the ABTS cation radical: identification of new oxidation products.  

Science.gov (United States)

The melatonin metabolite N1-acetyl-5-methoxykynuramine (AMK; 1), which was previously shown to be a potent radical scavenger, was oxidized using the ABTS cation radical [ABTS = 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid)]. Several new oxidation products were obtained, which were separated by repeated chromatography and characterized by spectroscopic methods such as mass spectrometry (ESI-MS and ESI-HRMS), 1H-NMR and 13C-NMR, HMBC, HSQC, H,H COSY correlations and IR spectroscopy. The main products were oligomers of 1 (3 dimers, 1 trimer and 2 tetramers). In all cases, the amino group N2 was involved in the reactions. Two of the dimers turned out to be cis (2a) and trans (2b) isomers containing an azo bond. In the other dimer (3a), the nitrogen atom N2 was attached to atom C5 of the second aromatic amine, with loss of the methoxy group. In the trimer (5), one N2 formed a bridge to C5 of unit B, as in the respective dimer, while this one of C had bridged to C6 of B. One of the tetramers (6) was composed of a trimer 5 attached to N2 of a fourth 1 molecule via an azo bond as in 2a/b. In the other tetramer (7), an additional C-C bond between rings B and C in 6 is assumed. Although oligomers of AMK may only attain low in vivo concentrations, the types of reactions observed shed light on the physiologically possible metabolism of AMK once reacted with a free radical. The displacement of a methoxy group, rarely seen in the oxidation of methoxylated biomolecules, underlines the reactivity of AMK (1). Preliminary data show that, in the presence of ABTS cation radicals, AMK (1) can interact with side chains of aromatic amino acids, a finding which may be crucial for understanding to date unidentified protein modification by a melatonin metabolite detected earlier in experiments with radioactively labeled melatonin. PMID:16571272

Than, Ni Ni; Heer, Christina; Laatsch, Hartmut; Hardeland, Rüdiger

2006-01-01

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Interactions of melatonin and its metabolites with the ABTS cation radical: extension of the radical scavenger cascade and formation of a novel class of oxidation products, C2-substituted 3-indolinones.  

Science.gov (United States)

Melatonin had previously been shown to reduce up to four 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) cation radicals (ABTS*+) via a scavenger cascade ending with N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK). However, when melatonin is added to the reaction system in much lower quantities than ABTS*+, the number of radicals scavenged per melatonin molecule is considerably higher and can attain a value of ten. Under conditions allowing for such a stoichiometry, novel products have been detected which derive from AFMK (1). These were separated by repeated chromatography and the major compounds were characterized by spectroscopic methods, such as mass spectrometry (HPLC-MS, EI-MS and ESI-HRMS), 1H nuclear magnetic resonance (NMR) and 13C NMR, heteronuclear multiple bond connectivity (HMBC) correlations. The identified substances are formed by re-cyclization and represent 3-indolinones carrying the side chain at C2; the N-formyl group can be maintained, but deformylated analogs seem to be also generated, according to MS. The primary product from AFMK (1) is N-(1-formyl-5-methoxy-3-oxo-2,3-dihydro-1H-indol-2-ylidenemethyl)-acetamide (2), which is obtained after purification as E- and Z-isomers (2a, 2b); a secondary product has been identified as N-(1-formyl-2-hydroxy-5-methoxy-3-oxo-2,3-dihydro-1H-indol-2-ylmethyl)-acetamide (3). When H2O2 is added to the ABTS*+ reaction mixture in quantities not already leading to substantial reduction of this radical, compound 3 is isolated as the major product, whereas 2a and 2b are virtually absent. The substances formed differ from all previously known oxidation products which derive from melatonin and are, among these, the first 3-indolinones. Moreover, the aliphatic side chain at C2 is reminiscent of other substances which have been synthesized in the search for melatonin receptor ligands. PMID:17014695

Rosen, Joachim; Than, Ni Ni; Koch, Dorothea; Poeggeler, Burkhard; Laatsch, Hartmut; Hardeland, Rüdiger

2006-11-01

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Two new organic-inorganic complexes associating the radical anion ABTS ·- and the inorganic cation Ca 2+: Ca 0.55(ABTS)(H 2O) x and Ca 5(ABTS) 6(H 2O) 29  

Science.gov (United States)

The synthesis, crystal structure determination and physical properties of two new charge transfer salts containing the azinobisethylbenzothiazoline (ABTS) anion are described. Electrochemical oxidation in water of the diammonium salt of ABTS in presence of calcium chloride yields black single crystals of two new compounds with different morphologies. The needle-like crystals with Ca 0.55(ABTS)(H 2O) x formula ( x depending on the temperature) belong to the monoclinic symmetry, space group C2/ c and cell parameters a=21.568(5), b=14.535(5), c=8.0278(17) Å, ?=108.32(3)° at room temperature and a=22.180(4), b=14.288(3), c=8.0823(16) Å, ?=108.13(3)°, with a lowering of the symmetry, space group Cc, at 200 K. The plate-shaped crystals formulated as Ca 5(ABTS) 6(H 2O) 29 belong also to the monoclinic symmetry with P2 1 space group and cell parameters a=11.222(2), b=37.991(8), c=19.327(4) Å, ?=106.37(3)° at 200 K. The structure analysis of the first phase shows a one-dimensional character based on the stacking of organic molecules creating channels in which Ca 2+ cations and water molecules are located. The second phase can be described as an alternation of organic and inorganic layers corresponding to a bidimensional hybrid network. The magnetic and electrical properties will be discussed.

Denis, Annaig; Palvadeau, Pierre; Molinié, Philippe; Chauvet, Olivier; Boubekeur, Kamal

2001-09-01

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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

15

pH-dependent long-term radical scavenging activity of AA-2G and 6-Octa-AA-2G against 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation.  

Science.gov (United States)

The 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS (radical +)) decolorization assay was applied to evaluate the stoichiometric radical scavenging activity of ascorbic acid (AA) and two AA derivatives, 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G) and 2-O-alpha-D-glucopyranosyl-6-O-octanoyl-L-ascorbic acid (6-Octa-AA-2G). AA rapidly reacted with ABTS (radical +), and the reaction was completed within 10 min. In contrast, AA-2G and 6-Octa-AA-2G continuously reacted with ABTS (radical +), and the reaction was not completed after 2 h. The radical scavenging activity of AA-2G and 6-Octa-AA-2G in aqueous solutions at pH 4.0 and above was higher than that at pH 3.0, whereas AA showed no difference in the pH range 3 to 6. The amounts of ABTS (radical +) scavenged by one molecule of AA, AA-2G and 6-Octa-AA-2G after 2 h of reaction at pH 6.0 were approximately 2.0, 3.4 or 3.9 molecules, respectively. This study demonstrates that the quantity of ABTS (radical +) quenched by AA-2G and 6-Octa-AA-2G is superior to that of AA in a long-term reaction. PMID:12951491

Takebayashi, Jun; Tai, Akihiro; Yamamoto, Itaru

2003-09-01

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Mechanistic and comparative studies of melatonin and classic antioxidants in terms of their interactions with the ABTS cation radical.  

Science.gov (United States)

Melatonin and classic antioxidants possess the capacity to scavenge ABTSb+ with IC50s of 4, 11, 15.5, 15.5, 17 and 21 microm for melatonin, glutathione, vitamin C, trolox, NADH and NADPH, respectively. In terms of scavenging ABTSb+, melatonin exhibits a different profile than that of the classic antioxidants. Classic antioxidants scavenge one or less ABTSb+, while each melatonin molecule can scavenge more than one ABTSb+, probably with a maximum of four. Classic antioxidants do not synergize when combined in terms of scavenging ABTSb+. However, a synergistic action is observed when melatonin is combined with any of the classic antioxidants. Cyclic voltammetry indicates that melatonin donates an electron at the potential of 715 mV. The scavenging mechanism of melatonin on ABTSb+ may involve multiple-electron donations via intermediates through a stepwise process. Intermediates including the melatoninyl cation radical, the melatoninyl neutral radical and cyclic 3-hydroxymelatonin (cyclic 3-OHM) and N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK) seem to participate in these reactions. More interestingly, the pH of the solution dramatically modifies the ABTSb+ scavenging capacity of melatonin while pH changes have no measurable influence on the scavenging activity of classic antioxidants. An acidic pH markedly reduces the ABTSb+ scavenging capacity of melatonin while an increased pH promotes the interaction of melatonin and ABTSb+. The major melatonin metabolites that develop when melatonin interacts with ABTSb+ are cyclic 3-OHM and AFMK. Cyclic 3-OHM is the intermediate between melatonin and AFMK, and cyclic 3-OHM also has the ability to scavenge ABTSb+. Melatonin and the metabolites which are generated via the interaction of melatonin with ABTSb+, i.e. the melatoninyl cation radical, melatoninyl neutral radical and cyclic 3-OHM, all scavenge ABTSb+. This unique cascade action of melatonin, in terms of scavenging, increases its efficiency to neutralized ABTSb+; this contrasts with the effects of the classic antioxidants. PMID:12662346

Tan, Dun-xian; Hardeland, Rüdiger; Manchester, Lucien C; Poeggeler, Burkhard; Lopez-Burillo, Silvia; Mayo, Juan C; Sainz, Rosa M; Reiter, Russel J

2003-05-01

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

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

2010-01-01

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Synthesis, crystal structure determination and physical characterization of two new hybrid inorganic-organic salts associating the organic anion ABTS 2- and its radical anion ABTS rad - to the transition metal cations Fe 3+ or Cu 2+: Fe 2O(ABTS) 2(H 2O) 16 and Cu(ABTS) 2·(H 2O) 8  

Science.gov (United States)

Synthesis, crystal structure of two new ABTS (2,2-azinobis-3-ethyl benzothiazoline-6-sulfonate) hybrid organic-inorganic salts containing Fe 3+ or Cu 2+ cations is described. Electrochemical oxidation of the diammonium salt (ABTS)(NH 4) 2·2H 2O in presence of FeSO 4·7H 2O or CuSO 4·5H 2O in aqueous solutions yields to black single crystals of Fe 2O(ABTS) 2(H 2O) 16 and Cu(ABTS) 2·(H 2O) 8. Due to the low thermal stability of three water molecules intercalated in the network, crystal structures were solved at 200 K using a STOE IPDS diffractometer. Cell parameters are: a=8.5635(7) Å, b=8.69236(6) Å, c=20.336(2) Å, ?=84.69(1)°, ?=82.10(1)°, ?=81.767(9)°, space group P-1 for the iron complex and a=15.691(3) Å, b=14.474(3) Å, c=21.552(4) Å, ?=94.60(3)°, space group P2 1/c for the copper complex. Transition metal cations are in an octahedral coordination with a different condensation, corner-sharing octahedra Fe 2O 11 dimmers or CuO 6 octahedra. Taking in account these structural results, the chemical formula must be written: [Fe 2O(H 2O) 10][ABTS] 2·6H 2O and [Cu(H 2O) 5][ABTS] 2·3H 2O. The crystalline networks are also different; the iron complex salt presents a bidimensional character and the copper one can be considered as a one-dimensional network. Values obtained from bond valence calculations correspond to iron Fe 3+ and copper Cu 2+. A Mossbauer study shows that iron is in a high spin 3 + oxidation state without any magnetic ordering even at 4 K (isomer shift ?=0.62 mm s -1 and quadrupole splitting ? E=1.64 mm s -1).

Denis, Annaig; Boubekeur, Kamal; Molinié, Philippe; Léone, Philippe; Palvadeau, Pierre

2004-02-01

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

Science.gov (United States)

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

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

2006-04-01

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Reduction of the 2,2?-Azinobis(3-Ethylbenzthiazoline-6-Sulfonate) Cation Radical by Physiological Organic Acids in the Absence and Presence of Manganese  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Laccase is a copper-containing phenoloxidase, involved in lignin degradation by white rot fungi. The laccase substrate range can be extended to include nonphenolic lignin subunits in the presence of a noncatalytic cooxidant such as 2,2?-azinobis(3-ethylbenzthiazoline-6-sulfonate) (ABTS), with ABTS being oxidized to the stable cation radical, ABTS·+, which accumulates. In this report, we demonstrate that the ABTS·+ can be efficiently reduced back to ABTS by physiologically occurring organi...

Collins, Patrick J.; Dobson, Alan D. W.; Field, Jim A.

1998-01-01

 
 
 
 
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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

2013-08-01

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2010-01-01

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Nitric oxide converts fatty acid alkoxyl radicals into fatty acid allyl radicals.  

Science.gov (United States)

Nitric oxide (()NO) is thought to react with fatty acid alkoxyl radical, which is generated from fatty acid hydroperoxide via one-electron reduction. However, detail in the reaction remains obscure. In the present study, we examined the reaction of nitric oxide with fatty acid alkoxyl radical generated in the lipoxygenase/linoleate/13-hydroperoxyoctadecadienoate (13-HpODE) system under anaerobic conditions via HPLC equipped with mass spectrometry and photodiode array detections. In this reaction system, nitric oxide can scavenge linoleate alkoxyl radical, producing 13-ONO-9Z,11E-ODE. However, instead of 13-ONO-9Z,11E-ODE, 13-NO-9E,11E-ODE and 9-NO-10E,12E-ODE were alternatively detected in the reaction solution. To explain this contradiction, we proposed a mechanism as follows: (1) 13-ONO-9E/11Z-ODE undergoes homolytic cleavage at >CHONO bond into the linoleate allyl radical and nitrogen dioxide, (2) the allyl radical undergoes resonance stabilization into the E/E-form, and (3) nitric oxide scavenges the E/E-pentadiene radical at C9 or C13 position. Consequently, we concluded that nitric oxide immediately converts fatty acid alkoxyl radical into allyl radical. PMID:22037355

Koshiishi, Ichiro; Yokota, Azusa; Takajo, Tokuko

2011-12-15

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

Science.gov (United States)

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

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

2010-07-01

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

Scientific Electronic Library Online (English)

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

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

26

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

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

TOPOLSKA Dominika

2014-02-01

27

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- free radicals, total antioxidant activity and inhibition of lipid peroxidation by ferric thiocyanate (FTC) method. Butylated hydroxytoluene and ascorbic acid were used as positive con...

Zheleva-Dimitrova Dimitrina; Nedialkov Paraskev; Kitanov Gerassim

2010-01-01

28

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

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The free radical scavenging activity of the methanolic extract of Malva parviflora L. was examined using spectroscopic method against 2, 2-diphenyl-1-picrylhydrazyl radical (DPPH•), radical cation ABTS•+ (2, 2`-azinobis [3-ethylbenzothiazoline-6-sulfonic acid] diammonium salt) and the ferric reducing agent. Total phenolic, flavonoid and proanthocyanidin contents were also determined to assess their effects on the antioxidant activity of the extrac...

Afolayan, A. J.; Aboyade, O. M.; Sofidiya, M. O.

2008-01-01

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

Directory of Open Access Journals (Sweden)

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

A.J. Afolayan

2008-01-01

30

Peroxyl radicals of nucleic acids and their components  

International Nuclear Information System (INIS)

If free radicals add to the bases of nucleic acids or abstract a hydrogen atom from the sugar moiety, mainly carbon-centered radicals are formed. In the presence of oxygen such carbon-centered radicals are converted into the corresponding peroxyl radicals at nearly diffusion-controlled rates (k ? 2 x 109 M-1 s-1). Our knowledge of the free-radical chemistry of purines, especially in the presence of oxygen, is at present still very limited, so that this discussion must be restricted to pyrimidines and to the sugar moiety. This article attempts to make the reader familiar with some of the complexities of peroxy radical reactions and to give some examples of how such reactions are reflected in the degradation of the free components of nucleic acids, and to what extent such results may be extrapolated to the nucleic acids themselves. 30 refs., 1 tab

1986-01-01

31

Estimation of scavenging activity of phenolic compounds using the ABTS(*+) assay.  

Science.gov (United States)

Observations on the applicability of the ABTS(*+) assay to define structure-activity relationships (SARs) among phenols (AH) were based on experimental data and theoretical calculations. All AH examined (hydroxycinnamic derivatives, simple polyphenols, polyhydroxybenzoates, and flavonoids) were found to be active toward ABTS(*+). Moreover, known weak radical scavengers (i.e., coumaric and isoferulic acids) were found to be efficient or comparatively active to caffeic or rosmarinic acids in contradiction to the AH classification based on 1,1-diphenyl-2-picrylhydrazyl (DPPH) data or the bond dissociation enthalpy values. This behavior was observed both in ethanol and in buffered (pH 7.4) environment. Resorcinol and phloroglucin were found to be more active than catechol and hydroquinone, whereas, among polyhydroxybenzoates, 2,4-dihydroxybenzoic acid was the least active, in line with the DPPH and theoretical data. Therefore, it can be argued that the ABTS(*+) assay may give an indication for the presence of antioxidants in a certain system but SARs cannot be readily inferred. PMID:15264898

Nenadis, Nikolaos; Wang, Lan-Fen; Tsimidou, Maria; Zhang, Hong-Yu

2004-07-28

32

Pairwise trapping of radicals in ?irradiated malonic acid single crystals  

International Nuclear Information System (INIS)

High dose irradiation of malonic acid single crystals (up to 3 x 1021 eV/g) leads to the formation of measurable amounts of radical pairs. The build-up curve and the composition of radical pairs strongly suggest that the pairwise trapping is due to occasional overlapping of spurs. The stability of the pairs at a given temperature is a function of the distance between the radical sites but also of the relative orientations of the free electron orbitals. (author)

1977-01-01

33

e.s.r. of spin-trapped radicals in aqueous solutions of amino acids: reactions of the hydroxyl radical  

International Nuclear Information System (INIS)

The radicals produced by reactions of hydroxyl radicals with amino acids in aqueous solutions have been investigated. Hydroxyl radicals were formed by U.V.-photolysis of hydrogen peroxide and the short-lived amino acid radicals were spin-trapped by tert-nitrosobutane and identified by electron spin resonance spectroscopy. Nineteen amino acids were studied, and several radicals were identified which have not been observed previously by other methods. Only side-chain radicals were identified by alanine, threonine, aspartic acid, asparagine, lysine, phenylalanine, tyrosine, proline and hydroxyproline; whereas for glycine the C(2) carbon radical was spin-trapped. Both C(2) carbon radicals and side-chain radicals were assigned to valine, leucine, isoleucine, serine, glutamic acid, glutamine, arginine and methionine. (author)

1977-01-01

34

Amino acid peroxyl radicals. Formation and reaction with ascorbate  

International Nuclear Information System (INIS)

Complete text of publication follows. Proteins are significant targets for partly reduced oxygen species in vivo. This results in random formation of radicals on the amino acid residues (AA·) of the protein, which in turn, in the presence of oxygen, can yield the corresponding peroxyl radicals (AAOO·). Both radical types can cause further biological damage. We studied the N-acetylamide derivatives of the amino acids glycine, alanine and proline as models of these residues in proteins. We generated the amino acid radicals specifically by reaction with hydroxyl radicals produced in solutions irradiated with 2 MeV electrons in the presence of N2O. In the absence of oxygen the amino acid radicals decayed with rate constants in the narrow range (0.9-1.3) x 109 M-1s-1, while in the presence of oxygen they were converted very rapidly to the corresponding peroxyl radicals with rate constants that vary between 6.3 x 108 and 5.5 x 109 M-1s-1, depending on the amino acid. The corresponding N-acetylated amino acids were also studied and showed similar behaviour but with slightly smaller rate constants. Antioxidants are able to repair tyrosyl and tryptophanyl radicals in various proteins in vitro. For ascorbate, the principal endogenous biological antioxidant, we have measured rate constants in the range 105-108 M-1s-1. The peroxyl radicals of all amino acids studied here were reduced by oxidizing ascorbate to the ascorbyl radical. The reaction was followed at 360 nm, where ascorbyl radical has an absorption coefficient of 3300 M-1cm-1, and the derived rate constants were all close to 107 M-1s-1. However, the spontaneous decay of peroxyl radicals is also fast and competes with the reaction with ascorbate. It is to be stressed that reaction of AAOO· and ascorbate gives rise to hydroperoxides (AAOOH) that are also reactive molecules. Our study suggests that reaction with protein radicals may be responsible for the ascorbate loss reported in organisms exposed to oxidative stress.

2009-09-02

35

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

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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 a...

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

2008-01-01

36

Automatic flow system for sequential determination of ABTS scavenging capacity and Folin-Ciocalteu index: A comparative study in food products  

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In the present work, an automatic flow procedure for the sequential spectrophotometric determination of Folin-Ciocalteu reducing capacity (FC assay) and 2,2 -azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS•+) scavenging capacity expressed as the trolox equivalent (TEAC assay) is proposed for a comparative study of antioxidant properties in food products. Exploiting the flexibility of flow management associated to the computer control offered by multisyringe flow inject...

Magalha?es, Lui?s M.; Segundo, Marcela A.; Reis, Salette; Lima, Jose? L. F. C.; To?th, Ildiko? V.; Rangel, Anto?nio O. S. S.

2007-01-01

37

Antioxidant activity of selected phenols estimated by ABTS and FRAP methods  

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

Izabela Biskup

2013-09-01

38

Comparative evaluation of the radical-scavenging activities of fucoxanthin and its stereoisomers.  

Science.gov (United States)

Fucoxanthin (Fuco) is a characteristic carotenoid of brown seaweeds. In the present study, Fuco and its stereoisomers 9'Z-Fuco, 13Z- and 13'Z-Fuco were extracted from Laminaria japonica Aresch. They were isolated and purified by silica gel column chromatography, Sephadex LH-20, and reversed-phase HPLC. The radical-scavenging activities of the three stereoisomers were evaluated toward 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, 2-2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical, hydroxyl radical, and superoxide radical. The order of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity was 13Z- and 13'Z-Fuco > (all-E)-Fuco > 9'Z-Fuco. The order of 2-2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and hydroxyl radical-scavenging activities were 9'Z-Fuco > (all-E)-Fuco > 13Z-and 13'Z-Fuco. The order of superoxide radical-scavenging activity was 13Z- and 13'Z-Fuco > (all-E)-Fuco > 9'Z-Fuco. The scavenging activities of Fuco and its stereoisomers toward the four radical types were all dose-dependent. The ABTS, DPPH, and superoxide radical-scavenging activities were all weaker than that of tocopherol (VE), while their hydroxyl radical-scavenging activities were stronger than that of VE. The results confirmed that Fuco and its stereoisomers have potent antioxidant activities. PMID:24549234

Zhang, Yiping; Fang, Hua; Xie, Quanling; Sun, Jipeng; Liu, Rui; Hong, Zhuan; Yi, Ruizao; Wu, Hao

2014-01-01

39

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

Directory of Open Access Journals (Sweden)

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

Yiping Zhang

2014-02-01

40

URIC ACID REACTION WITH DPPH RADICALS AT THE MICELLAR INTERFACE  

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Uric acid, a water soluble antioxidant, is able to react with micelle incorporated diphenylpicrylhydracyl radicals. This indicates that uric acid can react at the lipid/water interface. The rate of the process follows the order cationic micelles >buffer/etanol > neutral micelles anionic micelles These results can be explained in terms of the compartmentalization of the reactants in different environments and the effect of electrostatic interactions in modulating the access of the urate anion ...

Abuin, E.; Lissi, E.; Ortiz, P.; Henriquez, C.

2002-01-01

 
 
 
 
41

Generation of hydroxyl radicals from metal-loaded humic acids  

Energy Technology Data Exchange (ETDEWEB)

Humic acids (HAs) are naturally occurring biopolymers that are ubiquitous in the environment. They are most commonly found in the soil, drinking water, and a variety of plants. Pharmacological and therapeutic studies involving humic acids have been reported to some extent. However, when certain transition metals are bound to humic acids, e.g., iron and copper, they can be harmful to biological organisms. For this study, humic acids were extracted from German, Irish, and New Hampshire soils that were selectively chosen because of their reich abundance in humic material. Each sample was treated at room temperature with 0.1 M ferric and cupric solutions for 48 h. The amount of iron and copper adsorbed by humic acid was accurately quantitated using atomic absorption spectroscopy. The authors further demonstrate that these metal-loaded humic acids can produce deleterious oxidizing species such as the hydroxyl radical (HO*) through the metal-driven Fenton reaction. Electron paramagnetic resonance (EPR) employing spin trapping techniques with 5,5-dimethylpyrroline N-oxide (DMPO) is used to confirm the generation of hydroxyl radicals. The DMPO-OH adduct with hyperfine splitting constants A{sub N} = A{sub H} = 14.9 G is observed upon the addition of exogenous hydrogen peroxide. The concentration of hydroxyl radical was determined using 4-hydroxytempo (TEMPO-OH) as a spin standard. The presence of another oxidizing species, Fe{double_bond}O{sup 2+}, is also proposed in the absence of hydrogen peroxide.

Paciolla, M.D.; Jansen, S.A. [Temple Univ., Philadelphia, PA (United States). Dept. of Chemistry; Davies, G. [Northeastern Univ., Boston, MA (United States). Dept. of Chemistry

1999-06-01

42

Spectrophotometric determination of ferrate (Fe(VI)) in water by ABTS.  

Science.gov (United States)

A new method for the determination of low concentrations (0.03-35 microM) of the aqueous ferrate (Fe(VI)) was developed. The method is based on the reaction of Fe(VI) with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) which forms a green radical cation (ABTS(+)) that can be measured spectrophotometrically at 415 nm (ABTS method). The reaction of Fe(VI) with ABTS has a stoichiometry of 1 : 1 in excess of ABTS (73 microM). The increase in absorbance at 415 nm for ABTS*+ generation was linear with respect to Fe(VI) added (0.03-35 microM) in buffered solutions (acetate/phosphate buffer at pH = 4.3) and was (3.40+/-0.05) x 10(4) M(-1) cm(-1). The reaction of Fe(VI) with ABTS was very rapid with a half-life time below 0.01 s at pH 4.3 and 73 microM of ABTS. This enables the ABTS method to measure Fe(VI) selectively. The residual absorbance of ABTS*+ was found to be stable in several water matrices (synthetic buffer solution and natural waters) and concentrations of Fe(VI) spiked in natural waters could be determined with high accuracy. The ABTS method can also be used as a tool to determine rate constants of reactions of Fe(VI). The second-order rate constant for the reaction of phenol with Fe(VI) was determined to be 90 M(-1) s(-1) at pH 7. PMID:15876448

Lee, Yunho; Yoon, Jeyong; von Gunten, Urs

2005-05-01

43

Coupling interactions between sulfurous acid and the hydroperoxyl radical.  

Science.gov (United States)

Radical-molecule complexes associated with the hydroperoxyl radical (HOO) play an important role in atmospheric chemistry. Herein, the nature of the coupling interactions between sulfurous acid (H(2)SO(3)) and the HOO radical is systematically investigated at the B3LYP/6-311++G(3df,3pd) level of theory in combination with the atoms in molecules (AIM) theory, the natural bond orbital (NBO) method, and energy decomposition analyses (EDA). Eight stable stationary points possessing double H-bonding features were located on the H(2)SO(3)...HOO potential energy surface. The largest binding energies of -12.27 and -11.72 kcal mol(-1) are observed for the two most stable complexes, where both of them possess strong double intermolecular H-bonds of partially covalence. Moreover, the characteristics of the IR spectra for the two most stable complexes are discussed to provide some help for their possible experimental identification. PMID:20041456

Li, Ping; Ma, Zhi-Ying; Wang, Wei-Hua; Shen, Zhi-Tao; Bi, Si-Wei; Sun, Hai-Tao; Bu, Yu-Xiang

2010-02-22

44

Structure and recombination of radicals in amino acid crystals  

International Nuclear Information System (INIS)

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

1975-01-01

45

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

46

Hydroxyl radical scavenging activity of naturally occurring furan fatty acids.  

Science.gov (United States)

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

Okada, Y; Kaneko, M; Okajima, H

1996-12-01

47

Fractionation and evaluation of radical-scavenging peptides from in vitro digests of buckwheat protein ?  

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Buckwheat protein (BWP) isolate was subjected to a two-stage in vitro digestion (1 h pepsin followed by 2 h pancreatin at 37 °C). The antioxidant potential of the BWP digests was compared by assessing their capacity to scavenge 2,2?-azinobis (3-ethylbenzothiszoline-6-sulphonic acid) (ABTS+•) and hydroxyl (•OH) radicals. The 2-h pancreatin digest, which demonstrated the strongest activity against both radicals, was subjected to Sephadex G-25 gel filtration. Of the six fractions collecte...

Ma, Yuanyuan; Xiong, Youling L.; Zhai, Jianjun; Zhu, Haining; Dziubla, Thomas

2010-01-01

48

Electrochemistry of ABTS at Glassy Carbon Electrodes  

Science.gov (United States)

The electrochemical and the mass transport behavior of ABTS2-/ABTS.- (2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate)) redox couple at glassy carbon electrode (GCE) in phosphate buffer solution (PBS, pH=4.4) is studied in detail by cyclic voltammetry combined with rotating disk electrode system. From the i-E curves recorded at different electrode rotating rate, rate constant, and transfer coefficient for ABTS 2- ? ABTS.-+e reaction at GCE electrode and the diffusion coefficient of ABTS2- in PBS are estimated to be 4.6 × 10-3 cm/s, 0.28, and 4.4 × 10-6 cm2/s, respectively. The transfer coefficient with a value of ca. 0.28 differs largely from the value of 0.5 that is always assumed in the literature. The origins for the difference of the rate constant determined and the challenges for estimating the standard rate constant are discussed. The performance for such ABTS2- mediated bio-cathode toward oxygen reduction reaction is discussed according to the over-potential drop as well as current output limit associated with the charge transfer kinetics of ABTS2- ? ABTS.-+e redox reaction and/or the mass transport effect.

Zeng, Han; Tang, Zhi-qiang; Liao, Ling-wen; Kang, Jing; Chen, Yan-xia

2011-12-01

49

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

50

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

International Nuclear Information System (INIS)

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

2012-06-01

51

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-09-15

52

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

53

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

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

Sibi, Mukund P.; Patil, Kalyani

2006-01-01

54

Characterization of major radical scavenger species in bovine milk through size exclusion chromatography and functional assays.  

Science.gov (United States)

Radical scavenging activities of bovine milk components were quantified following size exclusion chromatography (SEC) with postcolumn characterization of fractions using the scavenging of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radicals (ABTS*(+)) in the Trolox equivalent antioxidant capacity (TEAC) assay and peroxyl radicals formed from cleavage of 2,2'-azobis(2-amidinopropane) (AAPH) in the oxygen radical absorbance capacity (ORAC) fluorometric assay. Caseins were quantitatively the major radical scavenger species in both assays, whereas beta-lactoglobulin (beta-lg) and alpha-lactalbumin (alpha-la) were much less active and only in the peroxyl radical assay. The radical scavenging activity of the caseins could be quantitatively accounted for by their constituent amino acids, as there were no effects of denaturing agents or complete digestion with proteases. In contrast, the activities of the whey proteins were dependent on denaturation or partial hydrolysis and dominated by the free thiol in beta-lg. A component in milk serum with a molecular mass of approximately 100 kDa contributed significantly to both ABTS*(+) and peroxyl radical scavenging but was absent in whey. This radical scavenger was identified as beta-casein. The only significant low molecular weight radical scavenger species were identified as ascorbate and urate in both assays. PMID:19281275

Clausen, Morten R; Skibsted, Leif H; Stagsted, Jan

2009-04-01

55

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

International Nuclear Information System (INIS)

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

1993-02-01

56

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

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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 a...

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

2010-01-01

57

Reaction of azide radicals with amino acids and proteins  

International Nuclear Information System (INIS)

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

1979-01-01

58

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

Science.gov (United States)

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

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

2014-07-01

59

Reactions of the radical cations of acetic acid and acetic anhydride in CFClsub(3). [Gamma radiation  

Energy Technology Data Exchange (ETDEWEB)

The ESR spectra of el-irradiated solutions of acetic acid and acetic anhydride were studied depending on their concentrations in CFClsub(3). The structure of thus produced radical cations is confirmed with the deuterium substituted analogues. It is shown that the ion-molecular reaction of the radical cation CHsub(3) COOHsup(+) in the isolated dimer takes place for the dilute solutions of acetic acid in CFClsub(3) resulting in the formation of CHsub(3)COO followed by its decomposition to CHsub(3) + COsub(2) while the radicals CHsub(2)COOH are formed via secondary processes. The reactions of radical cations of acetic oxide were also studied.

Belevskij, V.N.; Belopushkin, S.I.; Feldman, V.I.

1985-11-01

60

Reactions of the radical cations of acetic acid and acetic anhydride in CFClsub(3)  

International Nuclear Information System (INIS)

The ESR spectra of ?-irradiated solutions of acetic acid and acetic anhydride were studied depending on their concentrations in CFClsub(3). The structure of thus produced radical cations is confirmed with the deuterium substituted analogues. It is shown that the ion-molecular reaction of the radical cation CHsub(3) COOHsup(+) in the isolated dimer takes place for the dilute solutions of acetic acid in CFClsub(3) resulting in the formation of CHsub(3)COO followed by its decomposition to CHsub(3) + COsub(2) while the radicals CHsub(2)COOH are formed via secondary processes. The reactions of radical cations of acetic oxide were also studied. (author)

1985-11-01

 
 
 
 
61

Measurement of antioxidant activity with trifluoperazine dihydrochloride radical cation  

Scientific Electronic Library Online (English)

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

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

62

Measurement of antioxidant activity with trifluoperazine dihydrochloride radical cation  

Directory of Open Access Journals (Sweden)

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

M.N. Asghar

2008-06-01

63

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

Scientific Electronic Library Online (English)

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

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

64

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2003-01-01

65

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

Directory of Open Access Journals (Sweden)

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

RENÉ TORRES

2003-09-01

66

Generation of guanine-amino acid cross-links by a free radical combination mechanism.  

Science.gov (United States)

A direct method has been developed for the in vitro synthesis of stable DNA-protein cross-links (DPC's) between guanine and amino acids (lysine and arginine). This method employs the combination of guanine neutral radicals, G(-H)?, and side-chain C-centered amino acid radicals. The latter were generated indirectly after first causing the selective photoionization of 2-aminopurine (2AP) embedded in the oligonucleotide, 5'-d(CC[2AP]TCGCTACC), by intense nanosecond 308 nm excimer laser pulses. The 2AP radical cation deprotonates rapidly to form the 2AP(-H)? neutral radical which, in turn, oxidizes the nearby guanine to form the neutral guanine G(-H)? radical, as described previously (Shafirovich et al., J. Phys. Chem. B, 2001, 105, 8431). In parallel, the hydrated electrons, generated by the photoionization of 2AP, are scavenged by nitrous oxide to generate hydroxyl radicals. In the presence of a large excess of the amino acids, the hydroxyl radicals oxidize the latter to produce C-centered amino acid radicals that combine with the G(-H)? radicals to form the guanine-amino acid cross-linked oligonucleotide product. Analogous products were generated by photoionizing the free nucleoside, 2',3',5'-tri-O-acetylguanosine, (tri-O-Ac-Guo), using intense nanosecond 266 nm Nd:YAG laser pulse irradiation. The guanine-amino acid cross-links thus produced site-specifically positioned either in oligonucleotides, or in the free nucleoside tri-O-Ac-Guo were isolated by HPLC methods and identified by high resolution LC-TOF/MS and LC-MS/MS methods. The possibility that analogous guanine-amino acid cross-linked products could be formed in vivo using single hit radical generation mechanisms during oxidative stress is discussed. PMID:24810398

Uvaydov, Yuriy; Geacintov, Nicholas E; Shafirovich, Vladimir

2014-06-21

67

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)

2000-03-01

68

Hydroxyl radical modify amino acids and prevent E. coli growth  

International Nuclear Information System (INIS)

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

1986-05-01

69

Hydroxyl radical modify amino acids and prevent E. coli growth  

Energy Technology Data Exchange (ETDEWEB)

The authors report that hydroxyl radical (/sup ./OH) damage to amino acids (AA) affects their incorporation into E. coli proteins. Modification of AA (Try, Trp, Met, Cys, His, Lys, Asn, Gln) by /sup ./OH was achieved by exposure to /sup 60/Co radiation (1-100 krads at 600 rads/min) in N/sub 2/O saturated water. Following exposure to /sup ./OH, the modified AA were added to suspensions of 8 AA requiring E. coli mutants in M9 medium + glucose. Mutants incubated with the /sup ./OH modified AA underwent less growth than those incubated with unmodified AA; with a declining exponential relationship between /sup ./OH exposure of AA and cell growth. The sensitivity of each AA to modification by /sup ./OH was as follows: Tyr > Trp > Met > Cys > His > Lys > Asn > Gln. Essentially the same pattern was observed for inhibition of mutant growth, which was proportional to the concentration of remaining unmodified (i.e. native) AA. Furthermore, cell growth was restored to normal levels by replenishment of native AA. When AA were irradiated at 50..mu..M and then diluted to concentrations expected to support exponential growth (different for each AA) the radiation doses at which mutant growth was inhibited by 63% were as follows (in krad): Tyr 41, Trp 48, Met 53, Cys 56, His 57, Lys 68, Asn 80, Gln 116. /sup ./OH-modified /sup 3/H-Trp was not a substrate for protein synthesis in Trp requiring mutants but was taken up by the cells. Modified Trp was also not incorporated in cell-free synthesis experiments. No toxicity was observed when wild type E. coli, in M9 medium + glucose, were supplemented with any of the/sup ./OH-modified AA. Thus /sup ./OH-modified AA do not support E. coli growth.

Zhang, Y.; Davies, K.J.A.

1986-05-01

70

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

Scientific Electronic Library Online (English)

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

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

71

Free-radical redox reactions of uranium ions in sulphuric acid solutions  

International Nuclear Information System (INIS)

The radiolytic reduction of uranyl ions in degassed sulphuric acid solutions containing various organic solutes was studied. It was shown that while COOH, CO2-, and ?-hydroxyl-alkyl radicals reduced uranyl ions, the ?-hydroxy-alkyl radicals and those derived from gluconic acid could not affect the reduction. The oxidation of uranium(IV) by hydrogen peroxide at pH 0.7 involves hydroxyl radicals in a chain mechanism but at pH 2.0 the oxidation proceeds by a non-radical reaction pathway. From the enhancement of the rate of oxidation of uranium(IV) by oxygen in the presence of 2-propanol, a mechanism involving the perhydroxyl radical, which reconciles earlier published data on kinetics and oxygen tracer studies, is proposed for the oxygen-uranium(IV) reactions

1986-02-01

72

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

Science.gov (United States)

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

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

2012-06-01

73

Protonated o-semiquinone radical as a mimetic of the humic acids native radicals: A DFT approach to the molecular structure and EPR properties  

Science.gov (United States)

Organic radicals are known to be an indispensable component of the humic acids (HA) structure. In HA two forms of radicals, stable (native) and short-lived (transient), are identified. Importantly, these radical forms can be easily differentiated by electron paramagnetic resonance (EPR) spectroscopy. This article provides a DFT-based insight into the electronic and molecular structure of the native radicals. The molecular models including an increase of the radical aromaticity and the hydrogen bonding between the radical and other functional groups of HA are taken under investigation. In consequence the interesting pieces of information on the structure of the native radical centers in HA are revealed and discussed, especially in terms of differences between the electronic structure of the native and transient forms.

Witwicki, Maciej; Jezierska, Julia

2012-06-01

74

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

Scientific Electronic Library Online (English)

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

Murat, Aydin.

75

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

International Nuclear Information System (INIS)

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

2010-12-01

76

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-12-15

77

Nucleophilic and electrophilic radical attack on maleic and fumaric acids in aqueous solution  

Science.gov (United States)

Rate coefficients ( k) of rad CH 2OH, CH3rad CHOH, (CH)2rad COH and Cl2-rad radical addition to maleic and fumaric acids were investigated between pH 1 and 8. Strong pH dependences observed were attributed to changes in protonation states of acids: H 2X, HX - and X 2-. k of rad CH 2OH, CH3rad CHOH, (CH)2rad COH addition to fumaric acid decreased in the order kF>k>k in agreement with the nucleophilic character of reaction. The electrophilic Cl2-rad radical showed opposite tendency. With maleic acid the monoanion had the highest reactivity towards nucleophilic and the lowest one towards electrophilic radicals. This is attributed to a prevalence of steric over polar effects for HM -.

Wojnárovits, László; Takács, Erzsébet; Emmi, Salvatore S.

2008-07-01

78

Free radicals in pyrimidines: ESR of ?-irradiated 5-cyclohexenyl-1,5-dimethyl barbituric acid  

International Nuclear Information System (INIS)

ESR studies have determined that ionizing radiation damage of hexobarbital (5-cyclohexenyl-1,5-dimethylbarbituric acid) causes the formation of a free radical (A) by hydrogen abstraction from the cyclohexenyl group. Hyperfine coupling tensors were determined for coupling of the unpaired electron to four protons. Visible light of wavelengths near 450 nm reversibly converts this radical to a second free radical (B) which also has the unpaired electron localized in the cyclohexenyl group. The activation energy for a thermally induced reverse conversion (B ? A) was determined to be 1.4 eV

1981-01-01

79

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 demon...

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

2006-01-01

80

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

Science.gov (United States)

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

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

1992-02-01

 
 
 
 
81

Spin trapping study on the nature of radicals generated by X radiolysis and peroxidation of linolenic acid  

International Nuclear Information System (INIS)

The radicals of linolenic acid and their spin adducts (SA) with PBN formed during X radiolysis of linolenic acid and in lipid peroxidation with ferrous ions were investigated and identified. It was found that in the absence of oxygen in pure linolenic acid at 77 K X irradiation produces alkyl and carboxyl radicals. In the presence of the spin trap alkyl radical spin adducts were formed. Irradiation of linolenic acid in the presence of oxygen at 77 K also resulted in the formation of alkyl radicals. These radicals were transformed into peroxy radicals in the interaction of alkyl radical with oxygen upon heating to 117 K. In the presence of spin trap X irradiation of linolenic acid and heating of the sample up to 300 K gave rise to EPR spectra of SA alkyl and unidentified radicals. Lipid peroxidation of linolenic acid induced by ferrous ions in the presence of spin trap also formed radicals and SA of linolenic acid. The spectral parameters of SA generated with ferrous ions in lipid peroxidation and of those generated during X radiolysis do not differ. The similarity of spectral parameters of SA in these two cases suggests a similarity in the structure of linolenic acid radicals. (author)

1983-09-14

82

Spin trapping study on the nature of radicals generated by X-radiolysis and peroxidation of linolenic acid  

Energy Technology Data Exchange (ETDEWEB)

The radicals of linolenic acid and their spin adducts (SA) with PBN formed during X-radiolysis of linolenic acid and in lipid peroxidation with ferrous ions were investigated and identified. It was found that in the absence of oxygen in pure linolenic acid at 77 K X-irradiation produces alkyl and carboxyl radicals. In the presence of the spin trap alkyl radical spin adducts were formed. Irradiation of linolenic acid in the presence of oxygen at 77 K also resulted in the formation of alkyl radicals. These radicals were transformed into peroxy radicals in the interaction of alkyl radical with oxygen upon heating to 117 K. In the presence of spin trap X-irradiation of linolenic acid and heating of the sample up to 300 K gave rise to EPR spectra of SA alkyl and unidentified radicals. Lipid peroxidation of linolenic acid induced by ferrous ions in the presence of spin trap also formed radicals and SA of linolenic acid. The spectral parameters of SA generated with ferrous ions in lipid peroxidation and of those generated during X-radiolysis do not practically differ. The similarity of spectral parameters of SA in these two cases suggests a similarity in the structure of linolenic acid radicals. 10 references, 3 figures.

Azizova, O.A.; Osipov, A.N.; Zubarev, V.E.; Yakhyaev, A.V.; Savov, V.M.; Kagan, V.E.; Vladimirov, Yu.A.

1983-01-01

83

Spin trapping study on the nature of radicals generated by X radiolysis and peroxidation of linolenic acid  

Energy Technology Data Exchange (ETDEWEB)

The radicals of linolenic acid and their spin adducts (SA) with PBN formed during X radiolysis of linolenic acid and in lipid peroxidation with ferrous ions were investigated and identified. It was found that in the absence of oxygen in pure linolenic acid at 77 K X irradiation produces alkyl and carboxyl radicals. In the presence of the spin trap alkyl radical spin adducts were formed. Irradiation of linolenic acid in the presence of oxygen at 77 K also resulted in the formation of alkyl radicals. These radicals were transformed into peroxy radicals in the interaction of alkyl radical with oxygen upon heating to 117 K. In the presence of spin trap X irradiation of linolenic acid and heating of the sample up to 300 K gave rise to EPR spectra of SA alkyl and unidentified radicals. Lipid peroxidation of linolenic acid induced by ferrous ions in the presence of spin trap also formed radicals and SA of linolenic acid. The spectral parameters of SA generated with ferrous ions in lipid peroxidation and of those generated during X radiolysis do not differ. The similarity of spectral parameters of SA in these two cases suggests a similarity in the structure of linolenic acid radicals.

Azizova, O.A.; Osipov, A.N.; Zubarev, V.E.; Yakhyaev, A.V.; Vladimirov, Yu.A. (Second Moscow State Medical Institute, Moscow (USSR)); Savov, V.M.; Kagan, V.E. (Moskovskij Gosudarstvennyj Univ. (USSR))

1983-09-14

84

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

International Nuclear Information System (INIS)

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

1980-01-01

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

Study of reactivity of neptunium ions toward OH radicals in perchloric acid solutions by pulse radiolysis method  

International Nuclear Information System (INIS)

This study investigated the reaction rates of neptunium ions with OH radicals in aqueous perchloric acid solutions using pulse radiolysis. Absolute rate constants were determined for reactions of OH radicals with Np(IV) and Np(V) ions in aqueous perchloric acid solutions, these rate constants were found to be practically independent of the acidity of the medium and are quite high, possibly to exclude the recombination of the OH radicals in the presence of these ions

1982-10-20

87

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

International Nuclear Information System (INIS)

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

1978-01-01

88

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

Science.gov (United States)

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

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

2010-12-01

89

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

International Nuclear Information System (INIS)

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

2010-12-01

90

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

91

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

International Nuclear Information System (INIS)

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

1978-01-01

92

Pulse radiolysis studies in model lipid systems: formation and behavior of peroxy radicals in fatty acids  

Energy Technology Data Exchange (ETDEWEB)

Radiolytic formation and peroxidation of fatty acid radicals have been investigated by pulse radiolysis techniques in oleate, linoleate, linolenate and arachidonate systems. A strong absorption band at 280 nm associated with conjugated radicals, R/sub conj/., formed in polyunsaturated fatty acid moieties has been used as a probe for kinetic processes occurring at doubly allylic sites in the hydrocarbon chain. Formation of R/sub conj/. by O/sup -/ has been found to be more efficient than the less selective OH radical. Peroxidation of R/sub conj/. is shown to be somewhat slower, (k/sub R.+O/sub 2/ approx. 3 x 10/sup 8/ M/sup -1/s/sup -1/), than O/sub 2/ reactions with radicals in oleate (k/sub R+O/sub 2/ = 1 x 10/sup 9/ M/sup -1/s/sup -1/). Peroxy radicals generated in these reactions disappear slowly be essentially second order processes (2k/sub RO/sub 2// approx. 10/sup 7/ M/sup -1/s/sup -1/). The superoxide radical, O/sub 2//sup -/, shows little if any reactivity towards 0.01 M linolenate or arachidonate over periods of 20s. 3 figures, 1 table.

Hasegawa, K.; Patterson, L.K.

1978-01-01

93

Indole-3-propionate: a potent hydroxyl radical scavenger in rat brain.  

Science.gov (United States)

The hydroxyl radical scavenging activity of indole-3-propionate was evaluated by kinetic competition studies with the hydroxyl radical trapping reagent 2,2'-azino-bis-(3-ethyl-benz-thiazoline-6-sulfonic acid) (ABTS) and by measuring hydroxyl radical-initiated lipid peroxidation in the rat striatum. Using ABTS, the indole was shown to act as a potent hydroxyl radical scavenger with a rate constant of 7.8x1010 mol l-1 s-1. Hydroxyl radical-initiated lipid peroxidation, determined by measuring tissue malondialdehyde formation, was inhibited dose-dependently both in vitro and in vivo. Indole-3-propionate reacts with hydroxyl radicals at a diffusion controlled rate and can thereby provide on-site protection against the oxidative damage of biomolecules induced by these highly reactive and toxic oxygen intermediates. While it remains to be established if endogenous brain tissue levels of indole-3-propionate are sufficiently high to have a significant impact on total antioxidative capacity, the compound itself or a structurally related agent may be useful as an antioxidant adjuvant to combat hydroxyl radical-mediated oxidative stress. PMID:9878843

Poeggeler, B; Pappolla, M A; Hardeland, R; Rassoulpour, A; Hodgkins, P S; Guidetti, P; Schwarcz, R

1999-01-01

94

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 l...

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

2013-01-01

95

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

2012-03-01

96

Influence of metal ions binding on free radical concentration in humic acids. A quantitative electron paramagnetic resonance study  

Energy Technology Data Exchange (ETDEWEB)

The influence of metal ions, e.g. Co(II), Cu(II), Mn(II), Ni(II), Fe(II), on free radical concentration in humic acids isolated from soil, peat and compost was investigated by electron paramagnetic resonance (EPR). The results show that metal ions with unfilled d-shell exhibit antiferromagnetic interactions with semiquinone radicals. Moreover, coordinated metals shift the quinone-semiquinone-hydroquinone equilibrium in the macromolecular matrix of humic acids. A strong decrease of semiquinone radical concentration in humic acid-metal complexes is observed. This effect is caused by interactions of metal ions with oxygen-containing stable radicals occurring in the aromatic systems of humic acids. Furthermore, the effect of metal coordination on free radical concentration in humic acids-metal complexes depends on the humic acid origin. FTIR spectroscopy was also used as an additional tool for studies of the metal ions interactions with carboxylic groups. [author].

Jerzykiewicz, M.; Jezierski, A. [Wroclaw Univ. (Poland). Faculty of Chemistry; Czechowski, F. [Wroclaw Univ. of Technology (Poland). Inst. of Organic Chemistry, Biochemistry and Biotechnology; Drozd, J. [Agricultural Univ. of Wroclaw (Poland). Inst. of Soil Science and Agricultural Environment Protection

2002-07-01

97

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

International Nuclear Information System (INIS)

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

2011-05-06

98

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)

1995-03-01

99

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

100

[Free radicals formed during UV-irradiation of unsaturated fatty acids containing peroxidation products].  

Science.gov (United States)

On the irradiation of oxidized linolic acid an assymetric ESR signal with g-factor 2.0039 and the linewidth 30--33 Oe has been registered. The signal could be the result of photolysis of hydroperoxides. During prolonged irradiation of all the samples accumulation of alkyl radicals characterized by a symmetric signal with a well-defined ultrafine structure has been observed. An increase of the sample temperature up to 87 K in the presence of oxygen was preceded by transformation of alkyl radical R into RO2. All the radicals disappeared at the temperature of 160 K. All these processes seem to be the first phases of photoperoxidation of unsaturated fat acids in lipid-containing systems, including biological membranes. PMID:221052

Odinokova, G G; Azizova, O A; Vladimirov, Iu A; Remizov, A N; Roshchupkin, D I

1979-01-01

 
 
 
 
101

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

Science.gov (United States)

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

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

2010-12-01

102

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

International Nuclear Information System (INIS)

The reactivity of the hydrated electron and the hydroxyl radical with boric acid has been investigated by steady-state and pulse radiolytic techniques. No evidence was found for appreciable reactivity with hydroxyl radicals by either method and an upper limit of 5 x 10"4 dm"3 mol"-"1 s"-"1 is estimated for the reaction rate constant. Steady-state irradiations gave no evidence for reactivity with the hydrated electron, but pulse-radiolysis experiments showed the hydrated electron decay rate to be linearly dependent on boric acid concentration but independent of pH. Although superficially suggesting a reaction with boric acid it seems more likely that the enhanced decay is due to an impurity in the boric acid (probably nitrate) and an upper limit of 5 x 10"3 dm"3 mol"-"1 s"-"1 is estimated for k(e"-sub(aq) + H_3B0_3). (author)

1987-01-01

103

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

International Nuclear Information System (INIS)

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

1978-01-01

104

Diastereoselective radical addition to ?-alkyl-?-methylene-?-butyrolactams and the synthesis of a chiral pyroglutamic acid derivative  

Science.gov (United States)

Summary The cis- and trans-stereoselective radical additions to ?-methylene-?-alkyl- ?-lactams were investigated and the scope and limitation of the reaction were also revealed. This stereoselective radical reaction was used for synthesis of chiral pyroglutamic acid derivatives starting from a commercially available chiral amino acid.

Yoshida, Eriko; Hamano, Masako

2013-01-01

105

The pH-induced shift in the g-tensor components of semiquinone-type radicals in humic acids DFT and EPR studies  

Science.gov (United States)

DFT method has been applied to calculate p Ka and g-tensors values of semiquinone radicals mimicking the radicals present in humic acids. The results obtained support the hypothesis that naturally occurring stable semiquinone radicals ( native form) are trapped in the humic acid macromolecule matrices which unables their direct involvement in the acid-base equilibrium with short-lived radicals ( transient form). The differences between calculated g parameters for protonated and deprotonated model radicals are similar to those observed for humic acids allowing to attribute the stable radicals to protonated semiquinones and the short-lived radicals to deprotonated forms.

Witwicki, Maciej; Jaszewski, Adrian R.; Jezierska, Julia; Jerzykiewicz, Maria; Jezierski, Adam

2008-09-01

106

On heterogeneity of radical distribution in ?-irradiated monocrystals of malonic acid  

International Nuclear Information System (INIS)

At 77 K the EPR spectra are investigated of ?-irradiated monocrystals (dose rate of 0.45 Mrad/hr, irradiation dose of 0.9 Mrad) of malonic acid-CH2(COOH)2, CD2(COOD)2 and CH2(COOH)2 with heterogenous addition of CD2(COOD)2 set down on the surface of crystal defects. It is shown that during the radiolysis of malonic acid the initial radicals are formed mainly close to crystal structure defects

1979-01-01

107

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

108

Free Radical Scavenging Activity of Kielmeyera variabilis (Clusiaceae)  

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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?...

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

2013-01-01

109

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

2008-01-01

110

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

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

Seiichiro Fujisawa

2008-10-01

111

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

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Full Text Available Previous experiments have demonstrated that the aqueous OH radical oxidation of methylglyoxal produces low volatility products including pyruvate, oxalate and oligomers. These products are found predominantly in the particle phase in the atmosphere, suggesting that methylglyoxal is a precursor of secondary organic aerosol (SOA. Acetic acid plays a central role in the aqueous oxidation of methylglyoxal and it is a ubiquitous product of gas phase photochemistry, making it a potential "aqueous" SOA precursor in its own right. However, the fate of acetic acid upon aqueous-phase oxidation is not well understood. In this research, acetic acid (20 ?M–10 mM was oxidized by OH radicals, and pyruvic acid and methylglyoxal experimental samples were analyzed using new analytical methods, in order to better understand the formation of SOA from acetic acid and methylglyoxal. Glyoxylic, glycolic, and oxalic acids formed from acetic acid and OH radicals. In contrast to the aqueous OH radical oxidation of methylglyoxal, the aqueous OH radical oxidation of acetic acid did not produce succinic acid and oligomers. This suggests that the methylgloxal-derived oligomers do not form through the acid catalyzed esterification pathway proposed previously. Using results from these experiments, radical mechanisms responsible for oligomer formation from methylglyoxal oxidation in clouds and wet aerosols are proposed. The importance of acetic acid/acetate as an SOA precursor is also discussed. We hypothesize that this and similar chemistry is central to the daytime formation of oligomers in wet aerosols.

Y. Tan

2012-01-01

112

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

Science.gov (United States)

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

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

2013-12-01

113

Thiyl radical attack on polyunsaturated fatty acids: a possible route to lipid peroxidation.  

Science.gov (United States)

Absolute rate constants have been measured for the reaction of cysteinyl free radicals, CysS., with linoleic (18:2), linolenic (18:3) and arachidonic acid (20:4) in water/alcohol mixtures using the radiation chemical technique of pulse radiolysis. They are in the order of 10(6)-10(7) M-1 s-1 and increase with the number of biallylic functions, and with the polarity of the solvent. The reaction is shown to be a hydrogen atom abstraction from biallylic C-H bonds and yields pentadienyl radicals. The thiol mediated repair of the latter is considerably slower. Thiyl free radicals must consequently be considered as a potential source of lipid peroxidation. PMID:2567162

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

1989-05-30

114

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

115

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

Science.gov (United States)

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

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

2013-12-01

116

Inhibitory effect of caffeic acid analogues isolated from Salviae Miltiorrhizae Radix against 1,1-diphenyl-2-picrylhydrazyl radical.  

Science.gov (United States)

Caffeic acid and its four polymers isolated from Salviae Miltiorrhizae Radix were examined for their activity of scavenging free radicals in a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical generating system. The results showed that the polymers of caffeic acid inhibited the DPPH radical more strongly than caffeic acid. The strongest activity was displayed by two tetramers, lithospermic acid B and its Mg2+ salt. The trimer (lithospermic acid) and dimer (rosmarinic acid) showed similar efficiency. In comparison, caffeic acid was less efficient in scavenging free radicals. Determination of the activity of caffeic acid derivatives of small molecules revealed that the o-dihydroxyl group was the most important active structure of caffeic acid derivatives for scavenging of free radicals. Lack or substitution of this structure resulted in marked reduction or even loss of the activity. Structural modification of the side chain of caffeic acid produced slight changes in activity. The present results demonstrate that a saturated group connected to the aromatic ring has slightly higher inhibitory activity against the DPPH radical than an unsaturated group. PMID:10048715

Chen, C P; Yokozawa, T; Chung, H Y

1999-01-01

117

ABT-199: A New Hope for Selective BCL-2 Inhibition  

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ABT-199 is a new selective small molecule inhibitor of BCL-2 that appears to spare platelets while achieving potent antitumor activity. Assays that can predict the efficacy of ABT-199 in individual tumors will be critical in determining how best to incorporate this promising agent into the armamentarium of cancer therapies.

Davids, Matthew S.; Letai, Anthony

2013-01-01

118

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

Science.gov (United States)

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

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

2014-04-15

119

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

International Nuclear Information System (INIS)

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

1976-01-01

120

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

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

Leifer Nicole

2006-04-01

 
 
 
 
121

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 O_2 was determined from the rate of buildup of the peroxyl radical absorption at 520 nm as a function of [O_2] and found to be 1.6 x 10"9 L mol"-"1 s"-"1. Phenyl radicals react with 2-PrOH by H abstraction; a rate constants of 4 x 10"6 L mol"-"1 s"-"1 was determined for 4-carboxyphenyl by competition with the reaction of this radical with O_2. 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 10"8-10"9 L mol"-"1 s"-"1. 24 refs., 4 figs., 1 tab

1994-08-18

122

Antioxidant and Free Radical Scavenging Capacity of Seed and Shell Essential Oils Extracted from Abrus precatorius (L  

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Full Text Available Essential oils from plants have been proven safe as natural antioxidants, and few are already marketed as digestive enhancers as well as in prevention of several degenerative diseases. This study evaluated the antioxidant capacity of seed and shell essential oils of Abrus precatorius (L, a herb used for ethno-medicinal practices in Nigeria. The essential oils were obtained by hydro-distillation. The ability of the oils to act as hydrogen/electrons donor or scavenger of radicals were determined by in-vitro antioxidant assays using 2,2-diphenyl-2-picryl-hydrazyl free radical (DPPH. scavenging; 2,2?-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS radical scavenging; lipid peroxide and nitric oxide radicals scavenging assays. The IC50 of the seed and shell oils (2.10 mg/mL and 1.20 mg/mL respectively showed that antioxidant activity is higher than that for the standard drugs (3.20 mg/mL and 3.40 mg/mL for the nitric oxide scavenging assay. The lipid peroxidation radical activity of the oils were similar to vitamin C, weak DPPH and ABTS radical scavenging activities were discovered in comparison to vitamin C and rutin. Generally, in the four antioxidant assays, a significant correlation existed between concentrations of the oils and percentage inhibition of free radicals and lipid peroxidation. The composition of A. precatorius essential oils reported earlier may account for their antioxidant capacity.

Sunday O. Okoh

2014-04-01

123

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2007-10-15

124

The reaction of sulfite anion radical (S0_3sup(.-)) with polyunsaturated fatty acids  

International Nuclear Information System (INIS)

Using the pulse radiolysis technique, S0_3sup(.-) was produced in aqueous solution by the reaction of S0_3"2"-with either sup(.)OH or the (pseudo-) halide radicals N_3sup(.),Br_2sup(.-), and (SCN)_2sup(.-); for the latter reactions rate constants were measured. The reaction of S0_3sup(.-) with linoleic, linolenic, and arachidonic acids was monitored using the strong absorption of the pentadienyl radical, one possible primary reaction product. In micellar systems no detectable reaction took place, however, monomeric fatty acids were observed to react with S0_3sup(.-). Lower limits of the rate constants for S0_3sup(.-) attack derived from the data are 1 x 10"5, 8 x 10"5, and 1.3 x 10"6 (dm"3 mol"-"1 s"-"1) for linoleate, linolenate, and arachidonate, respectively. (author)

1986-01-01

125

Concerted effects in the reaction of ·OH radicals with aromatics. Radiolytic oxidation of salicylic acid  

International Nuclear Information System (INIS)

Complete text of publication follows. Liquid chromatographic and capillary electrophoretic studies have been used to resolve the products produced in the radiolytic oxidation of salicylic acid in aqueous solution. These studies have shown that, as in the case of phenol, OH radicals preferentially add to the 3- and 5-positions that are, respectively, ortho and para to the OH substituent. However, in contrast to its reaction with phenol, addition at the ortho position is favored over addition to the para position. Because ·OH radical is a strong electrophile this difference suggests that addition of ·OH to the ortho position is enhanced as a result of the hydrogen bonding in salicylic acid. Similarly, addition to the 6-position is discriminated against

2002-09-05

126

PHENOLIC ACIDS AND FREE RADICAL SCAVENGING ACTIVITY OF ALCHEMILLA JUMRUKCZALICA PAWL  

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

M. Nikolova et al.

2012-03-01

127

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

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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 measur...

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

2013-01-01

128

Effect of hydrocarbon radical length of fatty acid collectors on flotation separation process of thorium ions  

International Nuclear Information System (INIS)

It is shown experimentally that the degree of flotation separation of thorium ions collected by their means increases firstly (potassium laurate), then decreases (potassium tridecanate) and after that increases again (potassium palminate) when increasing the length of the hydrocarbon radical of potassium soaps of saturated fatty acids. The first increase of the collector efficiency is due to the decrease of solubility of thorium-containing sublates, and drop and further increase is due to the change in colloidchemical properties of sublates

1991-01-01

129

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

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

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

2012-10-01

130

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

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

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

2010-05-01

131

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

International Nuclear Information System (INIS)

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

1987-01-01

132

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

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

2008-01-01

133

Uric acid a better scavenger of free radicals than vitamin C in rheumatoid arthritis  

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Uric acid an endogenous aqueous antioxidant in normal humans is present in much higher concentrations than vitamin C and has been known to cover 2/3rd of the free radical scavenging capacity in plasma. In the present study average uric acid levels of patients of rheumatoid arthritis were found to be close to the normal individuals. A unique feature was observed after classifying the patients on the basis of the duration of suffering, the patients having longer duration of disease had least ur...

Mahajan, Mridula; Kaur, Sukhraj; Mahajan, Shruti; Kant, Ravi

2009-01-01

134

Ion Radicals. Xiii. Spectroscopic and Cryoscopic Characterization of Ions and Ion Radicals from Phenothiazine and n-Methylphenothiazine in Sulfuric Acid Solutions (1,2).  

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The formation and interconversion of the N-methylphenothiazine cation radical and the N-methylphenothiazine dication from both N-methylphenothiazine and N-methylphenothiazine S-oxide in sulfuric acid solutions were demonstrated with e.s.r. and absorption ...

H. J. Shine D. R. Thompson C. Veneziani

1967-01-01

135

Radical-driven carbonyl-to-acid conversion and acid degradation in tropospheric aqueous systems studied by CAPRAM  

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Model studies on the aqueous phase radical-driven processing of carbonyl compounds and acids in clouds and deliquescent particles were performed. The model exposed that aqueous radical conversions of carbonyl compounds and its oxidation products can contribute potentially to the formation of functionalised organic acids. The main identified C 2-C 4 organic gas phase precursors are ethylene glycol, glycolaldehyde, glyoxal, methylglyoxal and 1,4-butenedial. The aqueous phase is shown to contribute significantly with about 93%/63%, 47%/8%, 31%/4%, 7%/4%, 36%/8% to the multiphase oxidative fate of these compounds under remote/urban conditions. Interestingly, the studies revealed that aqueous chemical processing is not only limited to in-cloud conditions but also proceeds in deliquescent particle phase with significant fluxes. Oxalic acid is shown to be formed preferably in deliquescent particles subsequent to the in-cloud oxidations. Mean aqueous phase oxalate formation fluxes of about 12, 42 and 0.4 ng m -3 h -1 in the remote, urban and maritime scenario, respectively. Additionally, the turnovers of the oxidation of organics such as methylglyoxal by NO 3 radical reactions are identified to be competitive to their OH pendants. At the current state of CAPRAM, mean C 2-C 4 in-cloud oxidation fluxes of about 0.12 and 0.5 ?g m -3 h -1 are modelled under the idealised remote and urban cloud conditions. Finally, turnovers from radical oxidations were compared with those of thermal reactions. It is demonstrated that, based on the sparse kinetic data available organic accretion reaction might be of interest in just a few cases for cloud droplets and aqueous particles but generally do not reach the oxidative conversion rates of the main radical oxidants OH and NO 3. Interestingly, oxidation reactions of H 2O 2 are shown to be competitive to the OH radical conversions in cases when H 2O 2 is not readily used up by the S(IV) oxidation.

Tilgner, A.; Herrmann, H.

2010-12-01

136

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

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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

137

Investigation into reaction of hydroxyl radical with oxalate-ion in acid aqueous solution by pulse radiolysis  

International Nuclear Information System (INIS)

Reaction of .OH radical with oxalate-ion in acid aqueous solution was studied by the pulse radiolysis method. The solutions studied after applying an accelerated electron pulse are characterized by optical absorption in UV range induced by formation of .OH radicals and radical products of their interaction with oxalate-ion. Computer simulation of the process was made to describe oxidation of the oxalate-ions. The rate constant of the reaction yielding radical HOOC-COO. (?max=250 nm, ?=1800 l mol-1 cm-1) is (5.0±0.5)x107 l mol-1 s-1. During interaction with hydrogen ion (k=1.1x107 l mol-1 s-1) radical HOOC-COO. is transformed into a radical of unstated nature, which is conditionally designated as H+(HOOC-COO). (?max=260 nm, ?=4000 l mol-1 cm-1)

2008-06-01

138

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

Science.gov (United States)

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

139

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

2012-10-24

140

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

Science.gov (United States)

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

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

2014-09-01

 
 
 
 
141

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

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Full Text Available SciELO Brazil | Language: English Abstract in portuguese Extratos etanólicos de 23 ervas e condimentos desidratados comercializados no Brasil foram analisados quanto as suas propriedades antioxidantes utilizando os radicais 2,2'-difenil-?-picrilhidrazil (DPPH•) e ácido 2,2'-azino-bis(3-etilbenzotiazolina-6-sulfônico) (ABTS•+), Trolox foi [...] usado como 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. 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) 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.

142

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

Directory of Open Access Journals (Sweden)

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

Lilian Regina Barros Mariutti

2008-12-01

143

Spectroscopic studies on the antioxidant activity of ellagic acid.  

Science.gov (United States)

Ellagic acid (EA, C14H6O8) is a natural dietary polyphenol whose benefits in a variety of diseases shown in epidemiological and experimental studies involve anti-inflammation, anti-proliferation, anti-angiogenesis, anticarcinogenesis and anti-oxidation properties. In vitro radical scavenging and antioxidant capacity of EA were clarified using different analytical methodologies such as total antioxidant activity determination by ferric thiocyanate, hydrogen peroxide scavenging, 1,1-diphenyl-2-picryl-hydrazyl free radical (DPPH) scavenging, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging activity and superoxide anion radical scavenging, ferrous ions (Fe(2+)) chelating activity and ferric ions (Fe(3+)) reducing ability. EA inhibited 71.2% lipid peroxidation of a linoleic acid emulsion at 45?g/mL concentration. On the other hand, butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), ?-tocopherol and ascorbic acid displayed 69.8%, 66.8%, 64.5% and 59.7% inhibition on the peroxidation of linoleic acid emulsion at the same concentration, respectively. In addition, EA had an effective DPPH(•) scavenging, ABTS(+) scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, ferric ions (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 EA can be used in the pharmacological, food industry and medicine because of these properties. PMID:24813273

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

2014-09-15

144

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

International Nuclear Information System (INIS)

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

2002-01-01

145

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

Science.gov (United States)

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. PMID:21813286

Matsui, Kei; Nazifi, Ehsan; Kunita, Shinpei; Wada, Naoki; Matsugo, Seiichi; Sakamoto, Toshio

2011-10-01

146

Characterization of fatty acids, bioactive lipids, and radical scavenging activity of Canterbury bells seed oil  

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Full Text Available The aim of this study was to characterize the chemical composition and radical scavenging activity of Canterbury bells (Campanula medium seed oil. C. medium seeds contained 9.2% extractable oil. The lipid classes, fatty acids, phytosterol and tocopherol composition of C. medium seed oil were determined. The amount of neutral lipids in the oil was the highest, followed by glycolipids and phospholipids. Linoleic and oleic were the main fatty acids. C. medium oil is characterized by high levels of phytosterols and ?-sitosterol was the main compound. ?-Tocopherol constituted 42.5% of the total tocopherol content followed by ?-tocopherol. The radical scavenging activity (RSA toward 1,1-diphenyl-2-picrylhydrazyl (DPPH radicals and galvinoxyl radicals of C. medium oil were higher than those of extra virgin olive oil. The diverse potential uses of C. medium oil may make this plant industrially important.El objetivo de este estudio fue caracterizar la composición química y la actividad de captación de radicales de aceites de semillas de campanillas de Canterbury (Campanula medium. Las semillas de C. medium contenían 9,2 % de aceite extraíble. Se determinó la composición de las diferentes clases de lípidos, ácidos grasos, fitoesteroles y tocoferoles. La cantidad de lípidos neutros en el aceite fue mayoritario, seguido de glicolípidos y fosfolípidos. Linoleico y oleico fueron los ácidos grasos principales. El aceite de C. medium se caracteriza por altos niveles de fitoesteroles y ?-sitosterol fue el compuesto principal. ?-tocoferol constituía 42,5 % del contenido total de tocoferol seguido de ?-tocoferol. La actividad de captación de radicales (RSA a 1,1-difenil-2- picrilhidrazil (DPPH y radicales galvinoxil de C. medium fueron superiores a las de aceite de oliva virgen extra. Los diversos usos potenciales de los aceites de C. medium pueden hacer que esta planta pueda ser importante industrialmente.

Hassanien, M. F.R.

2014-06-01

147

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

148

Rates and mechanism of the reactions of hydroxyl radicals with acetic, deuterated acetic, and propionic acids in the gas phase  

International Nuclear Information System (INIS)

Rate constants for the reactions of hydroxyl radicals with the monomer and dimer of acetic acid, deuterated acetic acids, and propionic acid have been determined by a laser photolysis-resonance absorption technique. Hydroxyl radicals were generated by photolysis of the acids at 222 nm with a KrCl laser and their decay was followed by time-resolved resonance absorption. The monomers of acetic and deuterated acetic acids reacted with OH much faster than the dimers, whereas the monomer and dimer of propionic acid reacted with about equal rate constants. A primary isotope effect was observed when carboxylic but not alkyl hydrogen was substituted by deuterium in acetic acid. The results are entirely consistent with the two-channel mechanism that we proposed for the reaction of OH with formic acid. The results are interpreted in terms of the variations in C-H bond strengths and in equilibrium constants for adduct formation of the acids studied

1989-07-05

149

Rates and mechanism of the reactions of hydroxyl radicals with acetic, deuterated acetic, and propionic acids in the gas phase  

Energy Technology Data Exchange (ETDEWEB)

Rate constants for the reactions of hydroxyl radicals with the monomer and dimer of acetic acid, deuterated acetic acids, and propionic acid have been determined by a laser photolysis-resonance absorption technique. Hydroxyl radicals were generated by photolysis of the acids at 222 nm with a KrCl laser and their decay was followed by time-resolved resonance absorption. The monomers of acetic and deuterated acetic acids reacted with OH much faster than the dimers, whereas the monomer and dimer of propionic acid reacted with about equal rate constants. A primary isotope effect was observed when carboxylic but not alkyl hydrogen was substituted by deuterium in acetic acid. The results are entirely consistent with the two-channel mechanism that we proposed for the reaction of OH with formic acid. The results are interpreted in terms of the variations in C-H bond strengths and in equilibrium constants for adduct formation of the acids studied.

Singleton, D.L.; Paraskevopoulos, G.; Irwin, R.S. (National Research Council of Canada, Ottawa, Ontario (Canada))

1989-07-05

150

Antioxidant properties of 2-O-beta-D-glucopyranosyl-L-ascorbic acid.  

Science.gov (United States)

The antioxidant activity of a provitamin C agent, 2-O-beta-D-glucopyranosyl-L-ascorbic acid (AA-2betaG), was compared to that of 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G) and ascorbic acid (AA) using four in vitro methods, 1,1-diphenyl-picrylhydrazyl (DPPH) radical-scavenging assay, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS(*+))-scavenging assay, oxygen radical absorbance capacity (ORAC) assay, and 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced erythrocyte hemolysis inhibition assay. AA-2betaG slowly and continuously scavenged DPPH radicals and ABTS(*+) in roughly the same reaction profiles as AA-2G, whereas AA quenched these radicals immediately. In the ORAC assay and the hemolysis inhibition assay, AA-2betaG showed similar overall activities to AA-2G and to AA, although the reactivity of AA-2betaG against the peroxyl radical generated in both assays was lower than that of AA-2G and AA. These data indicate that AA-2betaG had roughly the same radical-scavenging properties as AA-2G, and a comprehensive in vitro antioxidant activity of AA-2betaG appeared to be comparable not only to that of AA-2G but also to that of AA. PMID:18540110

Takebayashi, Jun; Yagi, Yasuyuki; Ishii, Rie; Abe, Shigeki; Yamada, Kazuhiko; Tai, Akihiro

2008-06-01

151

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

Science.gov (United States)

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. PMID:19551737

Kovala-Demertzi, Dimitra; Hadjipavlou-Litina, Dimitra; Primikiri, Alexandra; Staninska, Malgorzata; Kotoglou, Chronis; Demertzis, Mavroudis A

2009-06-01

152

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

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Fatty acid profile, polyphenolic content and resulting antioxidant activity of the most consumed edible oils on Macedonian market were studied. The levels of total polyphenolics were estimated spectrophotometically by extraction with 60 % aqueous methanol using Folin-Ciocalteau reagent. A common method for determination of the antioxidant activity of edible oils is the 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS•+) method. This method was used for...

Sanja Kostadinovic-Velickovska; Saša Mitrev

2013-01-01

153

Polyphenols, Ascorbic Acid and Carotenoids Contents and Antioxidant Properties of Habanero Pepper (Capsicum chinense) Fruit  

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Their high bioactive compounds content and importance as dietary antioxidants has increased interest in Capsicum fruit. The fruit of seven Capsicum chinense Jacq. var. habanero genotypes grown in Yucatan, Mexico, were analyzed to quantify their phenolic compounds, carotenoids and ascorbic acid contents, and to measure their free radical scavenging (ABTS assay) and antioxidant activities (?-carotene/linoleic acid assay). Phenolics (20.54 to 20.75 mg/100...

Maira Rubi Segura Campos; Karen Ramírez Gómez; Yolanda Moguel Ordoñez; David Betancur Ancona

2013-01-01

154

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

Science.gov (United States)

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

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

2013-12-01

155

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

156

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

Directory of Open Access Journals (Sweden)

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

M. Mendez

2013-06-01

157

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

International Nuclear Information System (INIS)

The mechanism of the benzophenone ketyl radical formation in acid methanol, ethanol, and 2-propanol was studied by using pulse-radiolysis and rigid-matrix techniques. When a 0.1 M ethanol solution of benzophenone containing hydrogen chloride (1.2 M) was irradiated at 77 K by ? rays from "6"0Co, the absorption spectrum of the trapped intermediates was ascribed solely to benzophenone ketyl radicals. The pulse-radiolysis study of the solution at 100 K revealed that the ketyl radicals are produced by protonation of presolvated benzophenone anion radicals. At 153 K, the ketyl radicals were observed to be produced also by hydrogen-atom transfer from CH_3CHOH and CH_3CH(OH)CH_3 to benzophenone; the temperature dependence of the transfer rate constant was studied

1980-10-02

158

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

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

Yoshinori Kadoma; Seiichiro Fujisawa

2012-01-01

159

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

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

Manoel L. de Menezes

2012-01-01

160

Reaction of sulfite anion radical (S0/sub 3/sup(. -)) with polyunsaturated fatty acids  

Energy Technology Data Exchange (ETDEWEB)

Using the pulse radiolysis technique, S0/sub 3/sup(.-) was produced in aqueous solution by the reaction of S0/sub 3//sup 2 -/with either sup(.)OH or the (pseudo-) halide radicals N/sub 3/sup(.),Br/sub 2/sup(.-), and (SCN)/sub 2/sup(.-); for the latter reactions rate constants were measured. The reaction of S0/sub 3/sup(.-) with linoleic, linolenic, and arachidonic acids was monitored using the strong absorption of the pentadienyl radical, one possible primary reaction product. In micellar systems no detectable reaction took place, however, monomeric fatty acids were observed to react with S0/sub 3/sup(.-). Lower limits of the rate constants for S0/sub 3/sup(.-) attack derived from the data are 1 x 10/sup 5/, 8 x 10/sup 5/, and 1.3 x 10/sup 6/ (dm/sup 3/ mol/sup -1/ s/sup -1/) for linoleate, linolenate, and arachidonate, respectively.

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

1986-01-01

 
 
 
 
161

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

International Nuclear Information System (INIS)

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

2009-07-15

162

Characterization of hydrogen bonds in the interactions between the hydroperoxyl radical and organic acids.  

Science.gov (United States)

The hydrogen bonds formed between the hydroperoxyl radical and formic, acetic, and trifluoroacetic acids were characterized using geometric, energetic, and electronic parameters through calculations done with the UB3LYP/6-311++G (3df,3pd) and UB3LYP/EPR-III methods. The wave functions were analyzed through the natural bond orbital, natural steric analysis, natural resonance theory, and atoms in molecules methods. The energy decomposition method proposed by Xantheas was used. The vibrational frequencies and the intensity of the O-H stretching bands, as well as the spin densities, were compared with experimental evidence. The results allowed the characterization of the hydrogen bonds formed in the complexation of the acids with the hydroperoxyl radical. Complexation led to significant alterations in the equilibrium geometry of the monomers. Energetic analysis proved that the studied complexes are stable and allowed the understanding of the effect of the electron-donating and electron-withdrawing groups in their stabilization. The alterations in the electronic structure of the monomers after complexation led to an increase in the resonance of the carboxyl group, which can be partially attributed to the hydrogen bond. PMID:14664609

Parreira, Renato L T; Galembeck, Sérgio E

2003-12-17

163

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

International Nuclear Information System (INIS)

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

1979-05-17

164

ABT-089 and ABT-894 reduce levodopa-induced dyskinesias in a monkey model of Parkinson's disease.  

Science.gov (United States)

Levodopa-induced dyskinesias (LIDs) are a serious complication of levodopa therapy for Parkinson's disease for which there is little treatment. Accumulating evidence shows that nicotinic acetylcholine receptor (nAChR) drugs decrease LIDs in parkinsonian animals. Here, we examined the effect of two ?2 nAChR agonists, ABT-089 and ABT-894, that previously were approved for phase 2 clinical trials for other indications. Two sets of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned monkeys were administered levodopa/carbidopa (10 mg/kg and 2.5 mg/kg, respectively) twice daily 5 days a week until they were stably dyskinetic. Each set had a vehicle-treated group, an nAChR agonist-treated group, and a nicotine-treated group as a positive control. Set A monkeys had previously received other nAChR drugs (nAChR drug-primed), whereas Set B monkeys were initially nAChR drug-naive. Both sets were administered the partial agonist ABT-089 (range, 0.01-1.0 mg/kg) orally 5 days a week twice daily 30 minutes before levodopa with each dose given for 1 to 5 weeks. ABT-089 decreased LIDs by 30% to 50% compared with vehicle-treated monkeys. Nicotine reduced LIDs by 70% in a parallel group. After 4 weeks of washout, the effect of the full agonist ABT-894 (range, 0.0001-0.10 mg/kg) was assessed on LIDs in Set A and Set B. ABT-894 reduced LIDs by 70%, similar to nicotine. Both drugs acted equally well at ?4?2* and ?6?2* nAChRs; however, ABT-089 was 30 to 60 times less potent than ABT-894. Tolerance did not develop for the time periods tested (range, 3-4 months). The nAChR drugs did not worsen parkinsonism or cognitive ability. Emesis, a common problem with nAChR drugs, was not observed. ABT-894 and ABT-089 appear to be good candidate nAChR drugs for the management of LIDs in Parkinson's disease. PMID:24515328

Zhang, Danhui; Bordia, Tanuja; McGregor, Matthew; McIntosh, J Michael; Decker, Michael W; Quik, Maryka

2014-04-01

165

An electron spin resonance study of radicals formed from tetrolic acid by radiolysis in a freon matrix  

International Nuclear Information System (INIS)

In the present study, e.s.r. spectra have been observed following ?-irradiation of dilute frozen solutions of tetrolic acid, MeC?CCO2H, in CFCl3 at 77 K. A typical spectrum is shown which we interpret in terms of an isotropic quartet from the parent radical cation. MeC?CCo2H+·, and an anisotropic triplet arising from the propargyl radical, ·CH2C?CCO2H, formed by deprotonation of the parent cation. This appears to be the first example of an alkyne radical cation to be observed in a CFCl3 matrix. (author)

1989-01-01

166

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

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

Y. Tan

2011-06-01

167

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 10"6 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

168

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

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

2006-01-01

169

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

International Nuclear Information System (INIS)

A partial decomposition of RNA molecules in Saccharomyces cerevisiae is caused by photochemically produced superoxide anion radical (O_2."-). Hydroxyl radicals (OH.) lead to complete destruction of RNA. Such radicals as originating from peroxidase-hydrogen peroxide reaction cause a partial decomposition of RNA molecules. All RNA species are damaged to the same extent by radicals. Damages due to oxygen radicals can be prevented or reduced by strong radical captors (dimethyl sulfoxide, 1,4-diazabicyclo-(2,2,2)-octane or superoxide dismutase). All these reactions proceed in aqueous solution. Correlations with the use of radicals in radiotherapy are discussed. (orig.)

1986-01-01

170

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

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

A.J. Afolayan

2013-01-01

171

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

International Nuclear Information System (INIS)

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

2008-01-01

172

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

173

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

Science.gov (United States)

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

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

2010-05-20

174

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

Science.gov (United States)

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

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

2013-01-01

175

On the gas phase hydrogen bond complexes between formic acid and hydroperoxyl radical. A theoretical study.  

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We present a systematic study on the gas-phase hydrogen-bonded complexes formed between formic acid and hydroperoxyl radical, which has been carried out by using B3LYP and CCSD(T) theoretical approaches in connection with the 6-311+G(2df,2p) basis set. For all complexes we have employed the AIM theory by Bader and the NBO partition scheme by Weinhold to analyze the bonding features. We have found 17 stationary points, and 11 of them present a cyclic structure. Their computed stabilities vary from 0.3 to 11.3 kcal/mol, depending on several factors, such as involvement in the hydrogen bond interaction, the geometrical constraints, and the possible concurrence of further effects such as resonance-assisted hydrogen bonds or inductive effects. In addition, three stationary points correspond to transition structures involving a double proton-transfer process whose features are also analyzed. PMID:16884204

Torrent-Sucarrat, M; Anglada, J M

2006-08-10

176

Electron paramagnetic resonance (EPR) studies on stable and transient radicals in humic acids from compost, soil, peat and brown coal  

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Quantitative EPR method was applied to characterise four types of humic acids (HA) derived from composts, soil, peat and soft brown coal. For each sample of HA the level of native (indigenous) radicals was estimated. Interactions of the HA with various gaseous agents and organic solvents were investigated. Strong effects of gaseous ammonia and aliphatic amines on spin concentration enhancement were observed; additionally, higher values of g-value were found to be associated with the formed 'transient' radicals. Correlation of copper(II) ions uptake by different HA with effect diminishing primary spin concentration was established. It was recognised that the radical centres, which are enhanced by 'ammonia effect' are quenched in the formed HA-Cu(II) complexes. The both opposite effects are competitive from each other, where 'copper(II) quenching effect' prevails. Reaction of nitrogen dioxide with the humic acids was also examined. The presence of diketones and/or other compounds with active methylene group results in formation of the iminoxy radicals; these radicals are immobilized in the solid (macromolecular) matrix of the humic acids.

Jezierski, Adam; Czechowski, Franciszek; Jerzykiewicz, Maria; Chen, Yona; Drozd, Jerzy

2000-02-01

177

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

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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. PMID:23399128

Pitarresi, Giovanna; Fiorica, Calogero; Licciardi, Mariano; Palumbo, Fabio Salvatore; Giammona, Gaetano

2013-02-15

178

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

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Full Text Available The radical-scavenging activities of two thiols, eight (thiobarbituric acid derivatives and six chain-breaking phenolic antioxidants were investigated using the induction period method for polymerization of methyl methacrylate (MMA initiated by thermal decomposition of 2,2’-azobisisobutyronitrile (AIBN and monitored by differential scanning calorimetry (DSC. The induction period (IP for the thiols 2-mercaptoethanol (ME and 2-mercapto-1-methylimidazole (MMI was about half that for phenolic antioxidants. Except for the potent inhibitor 5,5-dimethyl-2-thiobarbituric acid (3, the IP for thiobarbituric acid derivatives was about one tenth of that for phenolic antioxidants. The IP for 1,3,5-trimethyl-2-thiobarbituric acid (1 and 5-allyl-1, 3-dimethyl-2-thiobarbituric acid (7 was less than that of the control, possibly due to inhibition by a small amount of atmospheric oxygen in the DSC container. The ratio of the chain inhibition to that of chain propagation (CI/CP for the thiols and thiobarbituric acid compounds except for 1, 3 and 7 was about 10 times greater or greater than that for phenolic compounds. A kinetic chain length (KCL about 10% greater than that of the control was observed for 1, suggesting that 1 had chain transfer reactivity in the polymerization of MMA. The average molecular weight of polymers formed from thiobarbituric acid derivatives is discussed.

Seiichiro Fujisawa

2012-04-01

179

Electron paramagnetic resonance (EPR) studies on stable and transient radicals in humic acids from compost, soil, peat and brown coal  

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Quantitative EPR method was applied to characterise four types of humic acids (HA) derived from composts, soil, peat and soft brown coal. For each sample of HA the level of native (indigenous) radicals was estimated. Interactions of the HA with various gaseous agents and organic solvents were investigated. Strong effects of gaseous ammonia and aliphatic amines on spin concentration enhancement were observed; additionally, higher values of g-value were found to be associated with the formed 'transient' radicals. Correlation of copper (II) ions uptake by different HA with effect diminishing primary spin concentration was established. It was recognised that the radical centres, which are enhanced by 'ammonia effect' are quenched in the formed HA-Cu(II) complexes. Reaction of nitrogen dioxide with the humic acids was also examined

Jezierski, A.; Czechowski, F.; Jerzykiewicz, M.; Chen, Y.; Drozd, J. [University of Wroclaw, Wroclaw (Poland). Faculty of Chemistry

2000-02-01

180

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

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

Mileski Ksenija

2014-01-01

 
 
 
 
181

ABT-controllable laser hyperthermia of biological objects  

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The results of experimentally investigated laser heating of optically absorbing inhomogeneities inside the biological objects accompanied with monitoring of internal temperature by acoustical brightness thermometry (ABT) have been presented. One of the urgent problems of modern medicine is to provide organism safety during photodynamic therapy of various neoplasms including malignant ones. In the case when neoplasm differs from normal tissue mainly in optical absorption it seems to be effective to use laser heating for this purpose. In our experiments we used the NIR emission of CW and pulse-periodic Nd:YAG lasers (1064 nm) as well as CW semiconductor laser (800 nm) for heating of tissue- simulating phantom. Optically transparent gelatine with absorbing inhomogeneity inside was used as a phantom. Internal temperature was measured non-invasively by means of multi-channel ABT after long heating of an object by laser radiation. Temperature was also measured independently by contact electronic thermometer. The results of experiments demonstrated high efficiency of ABT application for internal temperature monitoring during PDT and other hyperthermia procedures. Besides that laser radiation can be used for backlighting followed by ABT investigation of internal structure of temperature distribution inside biological tissues. This work was supported by Russian Foundation for Basic Research (Projects # 00-02-16600; 01-02-06417; 01-02- 17645) and 6th competition-expertise of young scientists of Russian Academy of Sciences (Project #399).

Krotov, Eugene V.; Yakovlev, Ivan V.; Zhadobov, Maxim; Reyman, Alexander M.

2002-05-01

182

Cyclopropyl fatty acids implicate a radical but not a cation as an intermediate in P450BM3-catalysed hydroxylations.  

Science.gov (United States)

Novel cyclopropyl containing fatty acids are good substrates for P450(BM3) catalysed hydroxylation and analysis of their oxidation products indicates the presence of a radical intermediate (maximum rebound rate 2.6 x 10(10) s(-1)) and the absence of any cationic intermediate. PMID:14973583

Cryle, Max J; Stuthe, Julia M U; Ortiz de Montellano, Paul R; De Voss, James J

2004-03-01

183

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

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Full Text Available

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

G. L. FREITAS

2009-01-01

184

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

Science.gov (United States)

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

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

2013-06-01

185

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

Science.gov (United States)

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

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

2014-04-01

186

Damage of amino acids and proteins induced by nitrogen dioxide, a free radical toxin, in air.  

Science.gov (United States)

Damage of amino acids and proteins induced by nitrogen dioxide, a free radical toxin in polluted air, was investigated. When nitrogen dioxide (30-90 ppm) in air was exposed to a solution of an amino acid at pH 7.5 for several hours, tryptophan and tyrosine were damaged. Degradation of tryptophan was accompanied by formation of a nitroindole derivative. Decrease of tyrosine was accompanied by formation of 3-nitrotyrosine and fluorescent dityrosine. When nitrogen dioxide was exposed to a solution of bovine serum albumin, human gamma-globulin and bovine eye lens alpha-crystallin, the proteins were crosslinked by nondisulfide bonds. Tryptophan and tyrosine residues in the proteins were extensively decreased, and significant amounts of 3-nitrotyrosine and fluorescent dityrosine were formed. The modification of the proteins with nitrogen dioxide in air may have toxicological significance. Because fluorescent dityrosine is detected in a wide variety of natural proteins, nitrogen dioxide may play a role in its occurrence in natural proteins. PMID:7520406

Kikugawa, K; Kato, T; Okamoto, Y

1994-03-01

187

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

International Nuclear Information System (INIS)

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

1993-08-01

188

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

1998-11-15

189

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

1991-06-01

190

Release of reactive oxygen intermediates (superoxide radicals, hydrogen peroxide, and hydroxyl radicals) and peroxidase in germinating radish seeds controlled by light, gibberellin, and abscisic acid.  

Science.gov (United States)

Germination of radish (Raphanus sativus cv Eterna) seeds can be inhibited by far-red light (high-irradiance reaction of phytochrome) or abscisic acid (ABA). Gibberellic acid (GA3) restores full germination under far-red light. This experimental system was used to investigate the release of reactive oxygen intermediates (ROI) by seed coats and embryos during germination, utilizing the apoplastic oxidation of 2',7'-dichlorofluorescin to fluorescent 2',7'-dichlorofluorescein as an in vivo assay. Germination in darkness is accompanied by a steep rise in ROI release originating from the seed coat (living aleurone layer) as well as the embryo. At the same time as the inhibition of germination, far-red light and ABA inhibit ROI release in both seed parts and GA3 reverses this inhibition when initiating germination under far-red light. During the later stage of germination the seed coat also releases peroxidase with a time course affected by far-red light, ABA, and GA3. The participation of superoxide radicals, hydrogen peroxide, and hydroxyl radicals in ROI metabolism was demonstrated with specific in vivo assays. ROI production by germinating seeds represents an active, developmentally controlled physiological function, presumably for protecting the emerging seedling against attack by pathogens. PMID:11299341

Schopfer, P; Plachy, C; Frahry, G

2001-04-01

191

Solvent effect on EPR, molecular and electronic properties of semiquinone radical derived from 3,4-dihydroxybenzoic acid as model for humic acid transient radicals: High-field EPR and DFT studies  

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The g-tensor components and isotropic hyperfine constants of solvent-affected radical anion from 3,4-dihydroxybenzoic acid were computed at UBP86/EPR-II level and correlated with the molecular and electronic structures. The role of solvent was considered in two ways: by using a conductor-like screening model (COSMO) and by adding water molecules, hydrogen bonded to the radical. To reach the best efficiency of the calculations, the theoretical EPR parameters were compared with experimental derived from high-field (406.4 GHz) and X-band spectra. Inclusion of water molecules in the first hydration sphere of the radical appears to be mandatory for correct prediction of its properties.

Witwicki, Maciej; Jezierska, Julia; Ozarowski, Andrzej

2009-04-01

192

Manganese(II)-bicarbonate-mediated catalytic activity for hydrogen peroxide dismutation and amino acid oxidation: detection of free radical intermediates.  

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To examine the structural identities of reactive free radicals and the mechanism of the oxidative modification of proteins, we used EPR and spin-trapping methods to investigate the oxidation of amino acids by H2O2 as well as the decomposition of H2O2 itself catalyzed by Mn(II) ions. Superoxide and hydroxyl radicals (O2-. and OH.) were trapped by a spin trap, 5,5-dimethyl-1-pyrroline-1-oxide (DMPO), in a reaction mixture containing Mn(II) and H2O2 in bicarbonate/CO2 buffer. When Hepes was used...

Yim, M. B.; Berlett, B. S.; Chock, P. B.; Stadtman, E. R.

1990-01-01

193

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

Science.gov (United States)

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

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

2008-07-17

194

Picosecond Pulse Radiolysis of Highly Concentrated Sulfuric Acid Solutions: Evidence for the Oxidation Reactivity of Radical Cation H2O(•+).  

Science.gov (United States)

Aqueous solution of sulfuric acid is used as a suitable system to investigate the reactivity of the short-lived radical cation H2O(•+) which is generated by radiation in water. Ten aqueous solutions containing sulfuric acid with concentration from 1 to 18 mol?L(-1) are studied by picosecond pulse radiolysis. The absorbance of the secondary radical SO4(•-) (or HSO4(•)) formed within the 10 ps electron pulse is measured by a pulse-probe method in the visible range. The analysis of the kinetics show that the radicals of sulfuric acid are formed within the picosecond electron pulse via two parallel mechanisms: direct electron detachment by the electron pulse and oxidation by the radical cation of water H2O(•+). In highly concentrated solution when SO4(2-) is in contact with H2O(•+), the electron transfer becomes competitive against proton transfer with another water molecule. Therefore, H2O(•+) may act as an extremely strong oxidant. The maximum radiolytic yield of scavenged H2O(•+) is estimated to be 5.3 ± 0.1 × 10(-7) mol?J(-1). PMID:24824373

Ma, Jun; Schmidhammer, Uli; Mostafavi, Mehran

2014-06-12

195

Bond Dissociation Free Energies (BDFEs) of the Acidic H-A Bonds in HA(*)(-) Radical Anions by Three Different Pathways.  

Science.gov (United States)

Cleavage of radical anions, HA(*)(-), have been considered to give either H(*) + A(-) (path a) or H(-) + A(*) (path b), and factors determining the preferred mode of cleavage have been discussed. It is conceivable that cleavage to give a proton and a radical dianion, HA(*)(-) right harpoon over left harpoon H(+) + A(*)(2)(-) (path c), might also be feasible. A method, based on a thermodynamic cycle, to estimate the bond dissociation free energy (BDFE) by path c has been devised. Comparison of the BDFEs for cleavage of the radical anions derived from 24 nitroaromatic OH, SH, NH, and CH acids by paths a, b, c has shown that path c is favored thermodynamically. PMID:11667531

Zhao, Yongyu; Bordwell, Frederick G.

1996-09-20

196

[Lavoisier and radicals].  

Science.gov (United States)

Lavoisier and his co-workers (Guyton de Morveau, Bertholet, Fourcroy) considered that acids were constituted of oxygen and of something else that they called radicals. These radicals were known in some cases, i.e. nitrogen for nitrous acid, carbon for carbonic acid, phosphorus for phosphoric acid. In the case of sulfur, the sulfuric radical could be associated with different quantities of oxigen leading to sulfuric or sulfurous acids. In other cases radicals remained unknown at the time i.e. muriatic radical for muriatic acid, or benzoyl radical for benzoic acid. It is interesting to notice that Lavoisier evoked the case of compound radicals constituted of different substances such as carbon and hydrogen. PMID:17575840

Lafont, Olivier

2007-01-01

197

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

International Nuclear Information System (INIS)

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

1981-01-01

198

Probing the influence of protecting groups on the anomeric equilibrium in sialic acid glycosides with the persistent radical effect.  

Science.gov (United States)

A method for the investigation of the influence of protecting groups on the anomeric equilibrium in the sialic acid glycosides has been developed on the basis of the equilibration of O-sialyl hydroxylamines by reversible homolytic scission of the glycosidic bond following the dictates of the Fischer-Ingold persistent radical effect. It is found that a trans-fused 4O,5N-oxazolidinone group stabilizes the equatorial glycoside, i.e., reduces the anomeric effect, when compared to the 4O,5N-diacetyl protected systems. This effect is discussed in terms of the powerful electron-withdrawing nature of the oxazolidinone system, which in turn is a function of its strong dipole moment in the mean plane of the pyranose ring system. The new equilibration method displays a small solvent effect and is most pronounced in less polar media consistent with the anomeric effect in general. The unusual (for anomeric radicals) poor kinetic selectivity of anomeric sialyl radicals is discussed in terms of the planar ?-type structure of these radicals and of competing 1,3-diaxial interactions in the diastereomeric transition states for trapping on the ?- and ?-faces of the radical. PMID:24606062

Kancharla, Pavan K; Kato, Takayuki; Crich, David

2014-04-01

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

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

Science.gov (United States)

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

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

2014-04-01

 
 
 
 
201

The ABT Methodology Employment For VET of Quality Auditors  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents some achievements of the project entitled ???Disseminating Open and Innovative Tools and Services for Vocational Education and Training in Quality Assurance??? (acronym Do-IT financed by European Commission. The recent developments and results obtained during pilot testing of new pedagogical models and services, in Do-IT project, targeting engineering education in Romania are presented. This includes the activity Based Training methodology (ABT for quality management system audit course according to ISO 19011 and ISO 9001. ABT focuses on delivering theoretical content linking directly theory and practice according to the industrial production path of an object. The testing of the theoretical and practical achievements has been done using Student Response System (SRS, by using individual voting systems

Liviu Moldovan

2011-11-01

202

Addition and elimination kinetics in OH radical induced oxidation of phenol and cresols in acidic and alkaline solutions  

Science.gov (United States)

The rates of the two consecutive reactions, OH radical addition and H 2O/OH - elimination, were studied by pulse radiolysis in highly acidic (pH=1.3-1.9) and alkaline (pH?11) solutions, respectively, for phenol and for the three cresol isomers. The rate coefficient of the addition as measured by the build-up of phenoxyl radical absorbance and by a competitive method is the same (1.4±0.1)×10 10 mol -1 dm 3 s -1 both in acidic and alkaline solution. The rate coefficient of the H 2O elimination in acidic solution is (1.6±0.2)×10 6 s -1, whereas the coefficient of the OH - elimination in alkaline solutions is 6-8 times higher. The kinetics of the phenoxyl radical formation was described by the two-exponential equation of the consecutive reactions: the first exponential is related to the pseudo-first-order addition, while the second to the elimination reaction. No considerable structure dependence was found in the rate coefficients, indicating that the methyl substitutent in these highly acidic or alkaline solutions influences neither the addition nor the elimination rate.

Roder, M.; Wojnárovits, L.; Földiák, G.; Emmi, S. S.; Beggiato, G.; D'Angelantonio, M.

1999-05-01

203

The ABT Methodology Employment For VET of Quality Auditors  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper presents some achievements of the project entitled ???Disseminating Open and Innovative Tools and Services for Vocational Education and Training in Quality Assurance??? (acronym Do-IT) financed by European Commission. The recent developments and results obtained during pilot testing of new pedagogical models and services, in Do-IT project, targeting engineering education in Romania are presented. This includes the activity Based Training methodology (ABT) for quality management sys...

Liviu Moldovan

2011-01-01

204

Free Radical Scavenging Activity of Kielmeyera variabilis (Clusiaceae  

Directory of Open Access Journals (Sweden)

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

Dulce Helena Siqueira Silva

2013-02-01

205

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

Directory of Open Access Journals (Sweden)

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

Nesrin Colak

2013-05-01

206

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

207

2-O-alpha-D-glucopyranosyl-L-ascorbic acid scavenges 1,1-diphenyl-2-picrylhydrazyl radicals via a covalent adduct formation.  

Science.gov (United States)

The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging mechanism of 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G) was studied. We found two undefined products, named X and Y, in the reaction mixture of AA-2G and the DPPH radical under acidic conditions by HPLC analysis. The reaction mixture was further subjected to LC-MS analysis. X was found to be a covalent adduct of AA-2G and the DPPH radical. On the other hand, Y could not be identified, probably because it was a mixture. A time-course study of the radical-scavenging reaction revealed that one molecule of AA-2G scavenged one molecule of DPPH radical to generate an AA-2G radical, which readily reacted with another molecule of the DPPH radical to form a covalent adduct (X). Subsequently, this adduct slowly quenched a third molecule of the DPPH radical, resulting in reaction products (Y). Therefore, one molecule of AA-2G has only one oxidizable -OH group, but can scavenge three molecules of the DPPH radical. The radical-scavenging mechanism of AA-2G elucidated in this study should be useful in understanding the biological roles of AA-2G per se in the food and cosmetic fields. PMID:17341834

Takebayashi, Jun; Asano, Ryuji; Nakae, Yoshinori; Saito, Morio; Gohda, Eiichi; Yamamoto, Itaru; Tai, Akihiro

2007-03-01

208

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

International Nuclear Information System (INIS)

Complete text of publication follows. Thiyl radicals radiolytically generated from thiophenol in methanolic solution are known to isomerise double bonds of poly-unsaturated fatty acids (PUFA). ?-irradiating of such a system containing all-cis 5,8,11,14 eicosatetraenoic acid (arachidonic acid, AA) with low doses (0.1-0.8 kGy) results in a mixture of 8 to 32% mono-trans-isomers. Here we report about the influence of mono-trans-AA on the primary steps of AA-metabolism and prostaglandin synthesis, catalysed by cyclooxygenase (COX). In the cell-free model system the reaction of COX-1 with AA was analysed by controlling the oxygen level during the enzymatic reaction. As an example, a mixture of a low quantity of mono-trans-isomerized AA (10%) and 90% all-cis-isomer exhibits a marked reduced oxygen consumption by 45%. As further proofs - the yield of reactive oxygen species (ROS) generated by the COX-coupled peroxidase reaction was detected, - and the COX-1 activity in presence of different amounts of trans-AA was characterized using a photometric assay based on the oxidation of TMPD. All these methods indicated semiquantitatively a reduced activity of COX-1, depending on the trans-isomer yield. Therefore, an inhibition of COX-1 activity by only one trans-double-bond in AA could be concluded. Furthermore, in vitro cell-line experiments were performed analysing the influence of mono-trans-isomerized AA on the activity of the cell-own COX-2. Hence, VD_3-differentiated and LPS-stimulated monocyte-like cells were incubated with mono-trans-AA and ROS-production was detected by the chemiluminescence measurements mentioned above. Compared to the reaction with all-cis-AA we found a considerable lowered formation of ROS. Likewise, we obtained a reduced PGE_2-expression between 15 and 40% for cells treated with 8 to 29% trans-AA. The model as well as in vivo experiments demonstrate an inhibition effect of mono-trans-AA and give rise for postulating an enzyme blocking mechanism for COX-1 and COX-2 by trans-isomers

2002-09-05

209

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

210

Effects of Precursor Concentration and Acidic Sulfate in Aqueous Glyoxal?OH Radical Oxidation and Implications for Secondary Organic Aerosol  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Previous experiments demonstrated that aqueous OH radical oxidation of glyoxal yields low-volatility compounds. When this chemistry takes place in clouds and fogs, followed by droplet evaporation (or if it occurs in aerosol water), the products are expected to remain partially in the particle phase, forming secondary organic aerosol (SOA). Acidic sulfate exists ubiquitously in atmospheric water and has been shown to enhance SOA formation through aerosol phase reactions. In this work, we inves...

Tan, Yi; Perri, Mark J.; Seitzinger, Sybil P.; Turpin, Barbara J.

2009-01-01

211

Characterization of the Peroxidase Mechanism upon Reaction of Prostacyclin Synthase with Peracetic Acid. Identification of a Tyrosyl Radical Intermediate†  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Prostacyclin synthase (PGIS) is a membrane-bound class III cytochrome P450 that catalyzes an isomerization of prostaglandin H2, an endoperoxide, to prostacyclin. We report here the characterization of the PGIS intermediates in reactions with other peroxides, peracetic acid (PA), and iodosylbenzene. Rapid-scan stopped-flow experiments revealed an intermediate with an absorption spectrum similar to that of compound ES (Cpd ES), which is an oxo–ferryl (Fe(IV)=O) plus a protein-derived radical....

Yeh, Hui-chun; Gerfen, Gary J.; Wang, Jinn-shyan; Tsai, Ah-lim; Wang, Lee-ho

2009-01-01

212

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Previous experiments have demonstrated that the aqueous OH radical oxidation of methylglyoxal produces low volatility products including oxalate and oligomers. These products are found predominantly in the particle phase in the atmosphere, suggesting that methylglyoxal is a precursor of secondary organic aerosol (SOA). Acetic acid is an important intermediate in aqueous methylglyoxal oxidation and a ubiquitous product of gas phase photochemistry, making it a potential "aqueous" SOA pr...

2011-01-01

213

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Previous experiments have demonstrated that the aqueous OH radical oxidation of methylglyoxal produces low volatility products including pyruvate, oxalate and oligomers. These products are found predominantly in the particle phase in the atmosphere, suggesting that methylglyoxal is a precursor of secondary organic aerosol (SOA). Acetic acid plays a central role in the aqueous oxidation of methylglyoxal and it is a ubiquitous product of gas phase photochemistry, making it a potential "aque...

2012-01-01

214

Spectroscopic studies on the antioxidant activity of p-coumaric acid  

Science.gov (United States)

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

Kiliç, Ismail; Ye?ilo?lu, Ye?im

2013-11-01

215

Kinetics of radical decay in crystalline amino acids. II. High-temperature study  

International Nuclear Information System (INIS)

Radical decay in x-irradiated L-leucine, and DL-valine, L- and DL-alanine, and L-arginine hydrochloride was studied between 300 and 4300K. Free radical decay was observed to take place with two distinct rates: an initial short duration process having an activation energy of 18 kcal/mole and a second, slower process. In most cases, the fraction of radicals decaying by the faster process is the same as the very slow room-temperature decay previously observed. The major process has a 3--6-kcal/mole higher activation energy. There is no evidence of radical conversion in either the initial or the slower process. However, in at least two cases residual peroxy radicals were observed at the termination of the slower process. Both decays obey second-order rate laws. The peroxy radical in at least one case decayed by a second-order law also. Vacancy controlled bulk diffusion is proposed for the major process, and the initial process is thought to be a conformationally aided bulk diffusion. It was observed that at any given temperature the spin concentration reaches a constant value. Increasing the temperature results in a second decay to a new constant value in a stepwise fashion. In the case of hydrated L-arginine hydrochloride and its partially deuterated derivative, the decay was found to be related to the dehydration process. A rapidly propagating radical transfer mechanism involving hydrogen abstraction is postulated for this decay process

1976-01-01

216

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

International Nuclear Information System (INIS)

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

1980-01-01

217

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

218

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

Science.gov (United States)

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

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

2013-07-01

219

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.

Yu Chen

2010-08-01

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

Uric acid provides an antioxidant defense in humans against oxidant- and radical-caused aging and cancer: a hypothesis  

Energy Technology Data Exchange (ETDEWEB)

During primate evolution, a major factor in lengthening life-span and decreasing age-specific cancer rates may have been improved protective mechanisms against oxygen radicals. We propose that one of these protective systems is plasma uric acid, the level of which increased markedly during primate evolution as a consequence of a series of mutations. Uric acid is a powerful antioxidant and is a scavenger of singlet oxygen and radicals. We show that, at physiological concentrations, urate reduces the oxo-heme oxidant formed by peroxide reaction with hemoglobin, protects erythrocyte ghosts against lipid peroxidation, and protects erythrocytes from peroxidative damage leading to lysis. Urate is about as effective an antioxidant as ascorbate in these experiments. Urate is much more easily oxidized than deoxynucleosides by singlet oxygen and is destroyed by hydroxyl radicals at a comparable rate. The plasma urate level in humans (about 300 ..mu..M) is considerably higher than the ascorbate level, making it one of the major antioxidants in humans. Previous work on urate reported in the literature supports our experiments and interpretations, although the findings were not discussed in a physiological context.

Ames, B.N. (Univ. of California, Berkeley); Cathcart, R.; Schwiers, E.; Hochstein, P.

1981-11-01

222

The ABT methodology employment for VET of quality auditors  

Directory of Open Access Journals (Sweden)

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

Liviu Moldovan

2011-12-01

223

Pulse radiolytic investigations on the reaction of the 6-yl radicals of uracils with Cu(II)-amino acid complexes  

International Nuclear Information System (INIS)

The 6-yl-radicals of uracil and 1,3-dimethyluracil reduced Cu(II)-amino acid complexes to produce Cu(I), that was proved by the formation of the complex with 2,9-dimethyl-1,10-phenanthroline (DMP). Rate constants for the reduction increased with increasing pH, ranging from 106 to 108 dm3mol-1 s-1. The kinetic pKa obtained for the complexes of glycine, alanine, and valine were all in agreement with pKa of the uracil-OH-adduct radical. The formation rate of Cu(I)-DMP complex suggests the existence of the transient adduct between initial reactants. (author)

1996-11-01

224

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 of trovafloxacin, levofloxacin, and ciprofloxacin against seven species of quinolone-susceptible members of the family Enterobacteriaceae, although it was less active than the comparators against Ci...

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

2003-01-01

225

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

226

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

227

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

Directory of Open Access Journals (Sweden)

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

Bogdanovi?-Pristov Jelena

2012-01-01

228

Antioxidant and Anti-inflammatory Activities of Methanol Extracts of Tremella fuciformis and Its Major Phenolic Acids.  

Science.gov (United States)

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

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

2014-04-01

229

Reaction of 2-hydroxy-2-propyl radical with maleic and fumaric acids in aqueous solution: pH dependence  

Science.gov (United States)

2-Hydroxy-2-propyl radical reacts with highly different rate coefficients ( k) with the three protonation forms of maleic and fumaric acids. With protonated fumaric acid k is high, (2.1 ± 0.4) × 10 9 mol -1 dm 3 s -1 due to the nucleophilic character of IP reaction and the electron withdrawing -COOH groups. With mono- and dianion molecules the k's are smaller, (6.6 ± 0.7) × 10 8 and (3.1 ± 3.0) × 10 7 mol -1 dm 3 s -1. In maleic acid k for the monoanion is higher ((1.34 ± 0.03) × 10 9 mol -1 dm 3 s -1) than for protonated and dianion species, (5.6 ± 0.6) × 10 8 and (3.5 ± 3.1) × 10 7 mol -1 dm 3 s -1. The high k is interpreted in terms of cyclic structure and charge localization between carboxylic groups.

Wojnárovits, László; Takács, Erzsébet; Emmi, Salvatore S.

2007-04-01

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

Accessibility of nucleic acid-complexed biomolecules to hydroxyl radicals correlates with their conformation: a fluorescence polarization spectroscopy study  

International Nuclear Information System (INIS)

A fluorescence methodology has been developed to examine the relationship between the conformational state of specific biomolecules in simple chromatin models and their accessibility to hydroxyl radicals (".OH). Polylysine and histone H1 were labelled with SECCA, the succinimidyl ester of coumarin-3-carboxylic acid, which generates the fluorescent derivative 7-OH-SECCA following its interaction with radiation-induced ".OH in aqueous solution. The fluorescence induced per unit ?-ray dose reflecting the accessibility of ".OH to such SECCA-conjugated biomolecules was recorded. The biomolecules were also labelled with the fluorescent derivative 7-OH-SECCA in trace amounts to study their conformation under identical conditions via fluorescence polarization spectroscopy. (author)

1994-09-01

232

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

1991-01-20

233

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

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The radical scavenging capacity and antioxidant activity of the vitamin E extracted from palm fatty acid distillate by the sequential cooling hexane were compared to those of the synthetic antioxidants including butylated hydroxyanisole (BHA), 2,6-di-tert-butyl-4-methylphenol (BHT), pyrogallol (PG), tert-butylhydroquinone (TBHQ) and commercial Alpha-tocopherol. The extracted vitamin E contained 2,509.57, 9.24, 157.85, 6.70, 1,779.92, 3.97, 2,376.38, 818.80...

2013-01-01

234

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

Science.gov (United States)

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

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

2013-01-01

235

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

Science.gov (United States)

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. PMID:22077157

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

2012-01-01

236

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

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

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

2013-01-01

237

Radical-scavenging-linked antioxidant activities of extracts from black chokeberry and blueberry cultivated in Korea.  

Science.gov (United States)

The objective of this study was to investigate the radical-scavenging-linked antioxidant properties of the extracts from black chokeberry and blueberry cultivated in Korea. The 70% ethanol extracts were prepared from black chokeberry and blueberry, and evaluated for total phenolic content, total flavonoid content, total proanthocyanidin content, and antioxidative activities, using various in vitro assays, such as DPPH(2,2-diphenyl-1-picrylhydrazyl), ABTS(2,2-azino-bis-(3-ethylenebenzothiozoline-6-sulphonic acid)) radical-scavenging activity, FRAP(ferric-reducing antioxidant power) and reducing power. The major phenolic compounds, including cyanidin-3-galactoside, cyanidin-3-arabinoside, neochlorogenic acid, procyanidin B1, were analysed by HPLC with a photodiode array detector. Results showed that total phenol, flavonoid and proanthocyanidin contents of black chokeberry extract were higher than those of blueberry extract. In addition, black chokeberry extract exhibited higher free radical-scavenging activity and reducing power than did blueberry extract. Cyanidin-3-galactoside was identified as a major phenolic compound, with considerable content in black chokeberry, that correlated with its higher antioxidant and radical-scavenging effects. These results suggest that black chokeberry extracts could be considered as a good source of natural antioxidants and functional food ingredients. PMID:24176315

Hwang, Seok Joon; Yoon, Won Byong; Lee, Ok-Hwan; Cha, Seung Ju; Kim, Jong Dai

2014-03-01

238

Phytochemical analysis and in vitro free-radical-scavenging activities of the essential oils from leaf and fruit of Melaleuca leucadendra L.  

Science.gov (United States)

The phytochemical profile of Melaleuca leucadendra L. leaf and fruit oils from Cuba was investigated by GC and GC/MS. Forty-one and sixty-four volatile compounds were identified and quantified, accounting for 99.2 and 99.5% of the leaf-oil and fruit-oil total composition, respectively. The main components were 1,8-cineol (43.0%), viridiflorol (24.2%), ?-terpineol (7.0%), ?-pinene (5.3%), and limonene (4.8%) in the leaf oil, and viridiflorol (47.6%), globulol (5.8%), guaiol (5.3%), and ?-pinene (4.5%) in the fruit oil. The antioxidant capacity of these essential oils was determined by three different in vitro assays (2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, thiobarbituric acid reactive species (TBARS), and 2,2'-Azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation), and significant activities were evidenced for all of them. PMID:20860029

Pino, Jorge A; Regalado, Erik L; Rodríguez, José L; Fernández, Miguel D

2010-09-01

239

Spectroscopic studies on the antioxidant activity of ellagic acid  

Science.gov (United States)

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

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

2014-09-01

240

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

International Nuclear Information System (INIS)

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

1982-08-19

 
 
 
 
241

Exploring water catalysis in the reaction of thioformic Acid with hydroxyl radical: a global reaction route mapping perspective.  

Science.gov (United States)

Hydrogen abstraction pathways, in the gas-phase reaction of tautomers of thioformic acid (TFA), TFA(thiol), and TFA(thione), with hydroxyl radical in the presence and absence of single water molecule acting as a catalyst, is investigated with high-level quantum mechanical calculations at CCSD(T)/6-311++G(2d,2p)//MP2/6-311++G(2d,2p), CCSD(T)/6-311++G(d,p)//DFT/BHandHLYP/6-311++G(d,p), and DFT/B3LYP/6-311++G(2df,2p) levels of the theory. A systematic and automated search of the potential energy surface (PES) for the reaction pathways is performed using the global reaction route mapping (GRRM) method that employs an uphill walking technique to search prereaction complexes and transition states. The computations reveal significant lowering of the PES and substantial reduction in the activation energy for the hydrogen abstraction pathway in the presence of water, thereby proving water as an efficient catalyst in the reaction of both the TFA tautomers with OH radical. The hydrogen-bonding interactions are observed to be responsible for the large catalytic effect of water. Notably, in the case of TFA(thiol), formyl hydrogen abstraction is observed to be kinetically more favorable, while acidic hydrogen abstraction is observed to be thermodynamically more feasible. Interestingly, in the case of TFA(thione), reaction pathways involving only formyl hydrogen abstraction were observed to be feasible. The water-catalyzed hydrogen abstraction reaction of TFA with hydroxyl radical, investigated in this work, can provide significant insights into the corresponding reaction in the biological systems. PMID:24835635

Kaur, Gurpreet; Vikas

2014-06-12

242

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)=(4.5â??6.2)Ã?109 dm3 molâ??1 sâ??1, have been studied by pulse radiolysis in N2O saturated solutions. The absorption maxima of the OH-adducts were in the range of 320â??340 nm. Their decay was according to a second-order reaction, 2k=(1â??9)Ã?108 dm3 molâ??1 sâ??1. In the presence of N2O/O2 the formation of peroxyl radicals was detectable for 2-, 4-ClBzA and ClBz, k(OH-adduct+O2)=(2â??4)Ã?107 dm3 molâ??1 sâ??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

243

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-05-15

244

ABT-869, a promising multi-targeted tyrosine kinase inhibitor: from bench to bedside  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Tyrosine Kinase Inhibitors (TKI have significantly changed the landscape of current cancer therapy. Understanding of mechanisms of aberrant TK signaling and strategies to inhibit TKs in cancer, further promote the development of novel agents. ABT-869, a novel ATP-competitive receptor tyrosine kinase inhibitor is a potent inhibitor of members of the vascular endothelial growth factor (VEGF and platelet derived growth factor (PDGF receptor families. ABT-869 showed potent antiproliferative and apoptotic properties in vitro and in animal cancer xenograft models using tumor cell lines that were "addicted" to signaling of kinases targeted by ABT-869. When given together with chemotherapy or mTOR inhibitors, ABT-869 showed at least additive therapeutic effects. The phase I trial for ABT-869 was recently completed and it demonstrated respectable efficacy in solid tumors including lung and hepatocellular carcinoma with manageable side effects. Tumor cavitation and reduction of contrast enhancement after ABT-869 treatment supported the antiangiogenic activity. The correlative laboratory studies conducted with the trial also highlight potential biomarkers for future patient selection and treatment outcome. Parallel to the clinical development, in vitro studies on ABT-869 resistance phenotype identified novel resistance mechanism that may be applicable to other TKIs. The future therapeutic roles of ABT-869 are currently been tested in phase II trials.

Goh Boon-Cher

2009-07-01

245

Comparative In Vitro Activity of ABT-773, a Novel Antibacterial Ketolide  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The in vitro activities of ABT-773, erythromycin, clarithromycin, and azithromycin were compared. ABT-773 was the most active compound against macrolide-susceptible Streptococcus pneumoniae, Streptococcus pyogenes, Staphylococcus aureus, Staphylococcus epidermidis, Listeria monocytogenes, and Enterococcus spp. and multidrug-resistant Streptococcus pneumoniae. It also had good activity against gram-negative and atypical respiratory tract pathogens and Helicobacter pylori.

Nilius, A. M.; Bui, M. H.; Almer, L.; Hensey-rudloff, D.; Beyer, J.; Ma, Z.; Or, Y. S.; Flamm, R. K.

2001-01-01

246

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

247

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2012-01-01

248

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

1993-08-08

249

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

250

Antioxidant Activity and Mechanism of Protocatechuic Acid in vitro  

Directory of Open Access Journals (Sweden)

Full Text Available Background: Protocatechuic acid (PCA is a natural phenolic acid widely distributed in plantsand is considered as an active component of some traditional Chinese herbal medicines such as Cibotium barometz (L. J.Sm, Stenoloma chusanum (L. Ching, Ilex chinensis Sims. PCA was reported to possess various pharmacological effects which may be closely correlated with its antioxidant activities. However, the antioxidant of PCA has not been investigatedsystematically yet. Methods: In the study, the antioxidant activities of protocatechuic acid were measured in vitrousing various antioxidant assays including 1,1-diphenyl-2-picryl-hydrazyl (DPPH•, 2,2’-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid (ABTS+•, superoxide anion radicals (•O2- and hydroxyl radical (•OH scavenging activity, ferric ions (Fe3+ and cupric ions (Cu2+ reducing power, ferrous ions (Fe2+ and cupric ions (Cu2+ chelating activity, compared with the positive controls Trolox or BHT.Results: In all assays, PCA along with positive controls exhibited dose-dependently antioxidant ability. Comparing to a standard antioxidant Trolox, the relative antioxidant activity of PCA (i.e. the ratio of IC50(Trolox/IC50(PCA was calculated as 2.8, 2.3, 3.7, 6.1, 4.2, 1.0, 2.7, 1.5, respectively, for DPPH, ABTS, reducing power (Fe3+, reducing power (Cu2+, superoxide anion radical-scavenging, hydroxyl radical-scavenging, chelating ability (Fe2+ and chelating ability (Cu2+. Functional Foods in Health and Disease 2011; 7:232-244 Conclusion: Comparing to Trolox, PCA shows much more effective antioxidant activity in vitro in both lipid and aqueous media. Hence, it could therefore be used in pharmacological or food industry as a natural antioxidant. It may exhibit antioxidant activity by both chelating metal transition ions as well as by scavenging free radicals via donating hydrogen atom (H• or electron (e.

Shuzhi Chen

2011-07-01

251

Ion Radicals. Xi. The Reactions of Thioxanthene and Thioxanthene 10-Oxide in Sulfuric Acid.  

Science.gov (United States)

Thioxanthene in 96% sulfuric acid is converted partly into the thioxanthylium ion and partly into a sulfonated thioxanthylium ion. The products obtained from this solution were thioxanthene, thioxanthone, and a thioxanthene-sulfonic acid. Solutions of thi...

H. J. Shine L. Hughes

1966-01-01

252

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

Directory of Open Access Journals (Sweden)

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

Bhujbal Akshay

2011-05-01

253

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

International Nuclear Information System (INIS)

Since data are accumulating that seem to dispute the role of O_2"- as a potent agent of biological damage, a study of the previously ignored conjugate acid, the perhydroxyl radical (HO_2), a transient species always formed in the presence of O_2"- in H_2O, was undertaken. The results of the systematic studies of the reaction rates of HO_2/O_2"- with a number of biochemicals as a function of pH are tabulated. The data indicated that HO_2 reacts faster than O_2"- with all of the compounds, and the reaction conditions are such that its presence is always assured. The reaction of HO_2 with linoleic acid (a C_1_8 unsaturated fatty acid with 2 double bonds) was studied in detail using HO_2 formed from O_2"- generated by photolysis of oxygenated alkaline ethanol solutions in a special apparatus previously described. The present work does not answer the question whether the oxidation of linoleic acid and probably other polyunsaturated fatty acids by HO_2 can lead to biological damage, but it can be assumed now that the most obvious sites for damage are the plasma and intracellular membranes

1981-11-18

254

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

Directory of Open Access Journals (Sweden)

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

J. L. Li

2009-10-01

255

Scavenging of es- and OH· radicals in concentrated acidic aqueous solutions, a new mechanism for reactivity of UV in acidic solution  

International Nuclear Information System (INIS)

Complete text of publication follows. The direct ionization of aqueous solutions by highly energetic photons or accelerated particles leads to the decomposition of the water molecule and results in the ultrafast formation of highly reactive radicals that are initially non-homogeneously distributed in the solution along the irradiation track. The determination of the initial radiolytic yields of the formation of these primary species, and their evolution during the spur expansion is the center of interest of many studies in the field of radiation chemistry. The ability to predict the evolution of systems exposed to ionizing radiation is important to a wide field of applications: nuclear power plants and waste treatment and storage, radiotherapy and radiobiology, electron beam depolution, and others. During the 1980s and 1990s, a wealth of pulse radiolysis and radical scavenging measurements were performed to obtain the time dependent radiolytic yield of different free radicals and molecular products. Recently, the values for the yield of the solvated electron were re-evaluated for water. Nevertheless, the initial G value of the OH. radical is still controversial. In neutral and acidic aqueous solutions containing 2 mol L-1 of Cl-, we studied the decay of the solvated electron and the formation of ClOH·- and Cl2·- by picosecond pulse radiolysis experiment. We estimated the yield of the OH· radical at 100 ps to be 5.0 x 10-7 mol J-1. In the framework of our studies on spent nuclear fuel it is also necessary to have a better understanding of the radiolytic transformation of the fourth valency of uranium, UIV. In fact, the spent nuclear fuel or waste are supposed to be buried deep underground or in salt mines. Several problems still remain to be resolved and one of the aspects studied is to consider a possible incident where the container fails by corrosion or the salt mines are exposed to water. In these cases UIV can be oxidized to very soluble hexavalent uranium, UVI, which promotes radionuclide release to the biosphere. In this particular case, it is also important to have a realistic understanding of the mechanism of the radiolytic processes involved in the complex medium. Thanks to the radiolytic yields measurements, we present a new mechanism for oxidation of UIV in acidic solution.

2009-09-02

256

Radical polymerization of methyl methacrylate in the presence of sulfuric acid  

International Nuclear Information System (INIS)

Mechanism of MMA polymerization in the presence of 80 and 95.6% H2SO4 and molar ratio [H2SO4]:[MMA]=1:1 was studied. Reaction was initiated by UV-irradiation at 20 deg C and ?-irradiation at -196 deg C. It was determined that reaction can be described as in ordinary terms of adduct polymerization. Basic kinetic effect in the investigated systems is decreasing of bimolecular chain break off constanta. Dilatometric method was used for kinetic study. EPR-spectra of produced radicals are presented

1975-04-01

257

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

Science.gov (United States)

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

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

2001-10-01

258

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

259

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

Scientific Electronic Library Online (English)

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

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

260

Accessibility of nucleic acid-complexed biomolecules to hydroxyl radicals correlates with their conformation: a fluorescence polarization spectroscopy study  

Energy Technology Data Exchange (ETDEWEB)

A fluorescence methodology has been developed to examine the relationship between the conformational state of specific biomolecules in simple chromatin models and their accessibility to hydroxyl radicals ([sup .]OH). Polylysine and histone H1 were labelled with SECCA, the succinimidyl ester of coumarin-3-carboxylic acid, which generates the fluorescent derivative 7-OH-SECCA following its interaction with radiation-induced [sup .]OH in aqueous solution. The fluorescence induced per unit [gamma]-ray dose reflecting the accessibility of [sup .]OH to such SECCA-conjugated biomolecules was recorded. The biomolecules were also labelled with the fluorescent derivative 7-OH-SECCA in trace amounts to study their conformation under identical conditions via fluorescence polarization spectroscopy. (author).

Makrigiorgos, G.M.; Bump, E.; Huang, C.; Kassis, A.I. (Harvard Medical School, Boston, MA (United States)); Baranowska-Kortylewicz, J. (Univ. of Nebraska Medical Center, Ohmaha, NE (United States))

1994-09-01

 
 
 
 
261

Hydrogen bonding interaction between HO2 radical and selected organic acids, RCOOH (R = CH3, H, Cl and F)  

Science.gov (United States)

A systematic study on the H-bonding interaction of hydroperoxyl radical with formic, acetic, chloroformic and fluoroformic acids has been carried out using B3LYP/6-311++G(2df,2p) and MP2/aug-cc-pVTZ methods. Several possible geometries have been considered, and the calculated global minima of RCOOH-HO2 have been found to be planar cyclic structure with two hydrogen bonds. A definite trend has been found between the electron donating character of the R group with calculated bond lengths, binding energies and vibrational frequencies. The most stable complex of RCOOH-HO2 with H2O has been found to be associated with a planar cyclic structure involving three hydrogen bonds.

Joshi, Ravi; Ghanty, Tapan K.

2013-10-01

262

Reaction of Ferrate(VI) with ABTS and Self-Decay of Ferrate(VI): Kinetics and Mechanisms.  

Science.gov (United States)

Reactions of ferrate(VI) during water treatment generate perferryl(V) or ferryl(IV) as primary intermediates. To better understand the fate of perferryl(V) or ferryl(IV) during ferrate(VI) oxidation, this study investigates the kinetics, products, and mechanisms for the reaction of ferrate(VI) with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and self-decay of ferrate(VI) in phosphate-buffered solutions. The oxidation of ABTS by ferrate(VI) via a one-electron transfer process produces ABTS(•+) and perferryl(V) (k = 1.2 × 10(6) M(-1) s(-1) at pH 7). The perferryl(V) mainly self-decays into H2O2 and Fe(III) in acidic solution while with increasing pH the reaction of perferryl(V) with H2O2 can compete with the perferryl(V) self-decay and produces Fe(III) and O2 as final products. The ferrate(VI) self-decay generates ferryl(IV) and H2O2 via a two-electron transfer with the initial step being rate-limiting (k = 26 M(-1) s(-1) at pH 7). Ferryl(IV) reacts with H2O2 generating Fe(II) and O2 and Fe(II) is oxidized by ferrate(VI) producing Fe(III) and perferryl(V) (k = ?10(7) M(-1) s(-1)). Due to these facile transformations of reactive ferrate(VI), perferryl(V), and ferryl(IV) to the much less reactive Fe(III), H2O2, or O2, the observed oxidation capacity of ferrate(VI) is typically much lower than expected from theoretical considerations (i.e., three or four electron equivalents per ferrate(VI)). This should be considered for optimizing water treatment processes using ferrate(VI). PMID:24697210

Lee, Yunho; Kissner, Reinhard; von Gunten, Urs

2014-05-01

263

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

Science.gov (United States)

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

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

2005-12-01

264

Stellar Astrophysics - A Tribute to Helmut A. Abt  

Science.gov (United States)

This conference was the sixth of the Pacific Rim Stellar Conference series and was the second time that China hosted the series. One of the main purposes of this conference was held as a tribute to Dr. Helmut A. Abt, who has spent tremendous effort in promoting the research and education in astronomy and astrophysics worldwide. The series of Pacific Rim Stellar Conference started in 1985 with the concentration on binary star research. Over the years, the series has grown wider in scope. In this conference, four topics were covered: binary stars, compact stars, high energy phenomena around compact stars and solar-type stars. Though a `Pacific Rim' conference, many of the eighty strong participants were from far regions of the world. This proceedings collects fifty-two papers contributed by over one hundred authors/co-authors working in the field of stellar physics research. The contributions to this proceedings are categorized according to the expertise of the participants into the following six groups: Compact Stars and High Energy Astrophysics, Binary Star Systems, Stars, Variable Stars and Cataclysmic Variables, and Galactic Astronomy. The volume contains many updated reviews in these research areas. Link: http://www.wkap.nl/prod/b/1-4020-1683-2

Cheng, K. S.; Leung, K. C.; Li, T. P.

265

Dimethyl Sulfoxide Prevents Hydroxyl Radical-Mediated Depolymerization of Hyaluronic Acid.  

Science.gov (United States)

We found that DMSO protected hyaluronic acid against deploymerization due to either of two sources of .OH, gamma irradiation or activated PMN. These findings are consistent with previous studies in which DMSO blocked the effects of .OH in other test syste...

R. B. Fox W. K. Fox

1983-01-01

266

First-principles study of radiation-induced radicals in solid-state amino acids and sugars: confrontation of density-functional calculations with experimental results  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this work, we present an extensive computational study of several radiationinduced radicals of biomolecules. In particular, two specific types of molecular systems will be highlighted: amino acids and sugars. Both systems are abundantly present in the natural world and are vital to the existence of life in all its forms. Amino acids are the building blocks of polypeptides and proteins, which are involved in nearly all biochemical processes. Sugars (or carbohydrates) also play a key role, n...

2004-01-01

267

Norcantharidin enhances ABT-263-mediated anticancer activity in neuroblastoma cells by upregulation of Noxa.  

Science.gov (United States)

Neuroblastoma is an aggressive childhood disease. Even with intensive conventional treatments, the long term survival rate for children with neuroblastoma remains less than 40%, highlighting the importance of finding new therapies. Bcl-2 family proteins play crucial roles in survival, proliferation and chemotherapeutic resistance of neuroblastoma cells. Therefore, targeting Bcl-2 with small molecule inhibitor ABT-263 could be a novel strategy for treatment of neuroblastoma. However, previous studies indicated that most neuroblastoma cell lines are resistant to ABT-263-mediated apoptosis. Thus, it is crucial to discover approaches that could overcome ABT-263 resistance. In this study, we examined the anticancer activity of ABT-263 in combination with norcantharidin (NCTD), a small-molecule anticancer drug derived from a traditional Chinese medicine, in human malignant neuroblastoma cells. We found that NCTD substantially enhanced ABT-263-mediated apoptosis induction, cell viability inhibition, and clonal formation inhibition in neuroblastoma SH-SY5Y and CHLA-119 cell lines. Moreover, the combination anticancer activity was accompanied by upregulation of Noxa, and was associated with characteristics of mitochondrial apoptosis signaling, such as cytosolic release of cytochrome c, activation of caspase-9,-3, and cleavage of PARP. Notably, we observed that knockdown of Noxa significantly attenuated cell death induction by cotreatment with ABT-263 and NCTD, indicating Noxa essentially contributes to the combination anticancer effect. Collectively, our study demonstrated that NCTD could overcome ABT-263-resistance in neuroblastoma cells, and suggested that combinational treatment of ABT-263 with NCTD might be a novel therapeutic option for children with neuroblastoma. PMID:24891300

Wang, Xiaohui; Gu, Zhimin; Li, Gongquan; Zhang, Shufeng; Cao, Zhenjie; Yang, Zhanfeng; Liu, Guangzhi

2014-08-01

268

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2010-01-01

269

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

Energy Technology Data Exchange (ETDEWEB)

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

Hicks, M.; Gebicki, J.M. (Macquarie Univ., North Ryde, NSW (Australia). School of Biological Sciences)

1993-08-01

270

Evaluation of antioxidant activity of isoferulic acid in vitro.  

Science.gov (United States)

Isoferulic acid (3-hydroxy-4-methoxycinnamic acid, IFA), the isomer of ferulic acid (4-hydroxy-3-methoxycinnamic acid), is a rare phenolic acid occurring in Rhizoma Cimicifugae. Unlike ferulic acid, which has been well investigated, the antioxidant activity of IFA has not been measured. In this study, IFA was systematically evaluated for its in vitro antioxidant activity for the first time. IC50 values were calculated of 7.30 +/- 0.57, 4.58 +/- 0.17, 1.08 +/- 0.01, 8.84 +/- 0.43, 7.69 +/- 0.39, 1.57 +/- 0.2, 13.33 +/- 0.49 microg/mL, respectively, for lipid peroxidation, DPPH (1,1-diphenyl-2-picrylhydrazyl radical) and ABTS (3-ethylbenzthiazoline-6-sulfonic acid diammonium salt) radical scavenging, reducing power on Fe3+ and CU2+ ions, and hydroxyl and superoxide anion radical scavenging. Comparison with the IC50 values with those of the positive controls, Trolox and butylated hydroxyanisole (BHA), it can be concluded that isoferulic acid is an effective natural antioxidant in both lipid and aqueous media. PMID:21941899

Wang, Xiaozhen; Li, Xican; Chen, Dongfeng

2011-09-01

271

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

International Nuclear Information System (INIS)

When cellular systems are exposed to ionizing radiation the long-term effects may range from minor disturbances to such dramatic changes as mutations and cell death. The processes leading to these macroscopical injuries are primarily confined at the molecular level. In all models aimed at a description of the action of radiation at the molecular level the formation of free radicals (which are species containing unpaired electrons) is a central concept. The technique of ESR spectroscopy is uniquely suited to study free radicals, as it is based on resonance absorption of energy by unpaired electrons in a magnetic field. ESR spectroscopy makes it possible to detect free radicals and, in some cases, to identify them. In order to study free radicals by ESR it is necessary to build up a sufficient number of unpaired spins in the sample (approximately 10"1"1 or more, depending on the shape of the resonance). This may be different techniques have been used to trap the induced radicals or to attain a sufficient steady state concentration level. A procedure which seems to contain a large amount of information is to irradiate at low temperatures, and, by subsequent heat-treatment of the sample to study the reactions and fate of the induced radicals. In this thesis single crystal studies of aromatic amino acids and pyrimidine derivitives together with some substituted purine derivitives are presented, and the results are discussed in relation to the present knowledge about radical formation in these classes of compounds. Single crystal studies of some sulfur-containing aromatic compounds have been presented with the purpose of shedding light on the electronic structure of sulfur-centred radicals. (JIW)

1979-01-01

272

About formation of radicals by the photolysis of uranyl salts in aliphatic carbon acids  

International Nuclear Information System (INIS)

The photolysis of UO_2(NO_3)_2x6H_2O and UO_2(RCOO)_2 (R=CH_3, C_2H_5, C_3H_7, and CH(CH_3)_2) has been studied by ESR spin trapping technique using nitrosodurene as a spin trap. Evidences for electron transfer from both coordinated anions and carboxylic acid to U(VI) were found. (author)

1982-05-11

273

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

AÍDA NEIRA; MIGUEL TARRAGA; ROSA CATALAN

2008-01-01

274

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

Science.gov (United States)

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

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

2008-10-01

275

Copper--ligand interactions and the physiological free radical processes. Part 3. Influence of histidine, salicylic acid and anthranilic acid on copper-driven Fenton chemistry in vitro.  

Science.gov (United States)

With a view to the possible use of copper(II)-*OH inactivating ligand (OIL) complexes as regulators of inflammation, the reactivity of the copper(II)-ascorbate system with hydrogen peroxide has been investigated in the presence of three key substances: histidine (the main copper(II) low molecular mass ligand in extracellular fluid), salicylic acid (the well-known nonsteroidal antiinflammatory drug, previously shown to be potentiated by copper(II) in animal models of inflammation), and anthranilic acid (an inactive substance by itself, known to be activated by copper(II) in the same models) at physiological pH (7.4) and inflammatory pH (5.5). Such substances may affect the amount of TBARS detected in solution following copper-mediated Fenton-like reactions through three distinct mechanisms: (i) by decreasing the Cu(II)/Cu(I) redox potential, i.e. at the expense of *OH radical production, (ii) by scavenging *OH radicals in the body of the solution, and/or (iii) by acting as a true OIL, i.e. at the expense of *OH detection. Redox potential measurements of initial solutions have been performed in parallel to TBARS determinations to help discriminate between different ligand influences. Computer-aided speciation has been used to understand the role of copper(II) distribution on the ligand effects characterised. Contrary to previous interpretations, histidine has been found to mainly affect *OH production by lowering the redox potential of the Cu(II)/Cu(I) couple. Salicylate, which has no effect on *OH production, has been confirmed to mainly scavenge *OH radicals in the body of the solution. Anthranilate, which both increases *OH production and decreases *OH detection, behaves as a potential OIL. These results tend to confirm our previous hypothesis that copper potentiation of antiinflammatory substances is indirect, i.e. independent of any interaction between metal and drug, whereas copper activation of substances that are inactive by themselves results from specific metal-substance interactions taking place at inflammatory sites. PMID:10766413

Gaubert, S; Bouchaut, M; Brumas, V; Berthon, G

2000-05-01

276

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

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

2009-01-01

277

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

International Nuclear Information System (INIS)

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

278

Formation of acyl radical in lipid peroxidation of linoleic acid by manganese-dependent peroxidase from Ceriporiopsis subvermispora and Bjerkandera adusta.  

Science.gov (United States)

Lipid peroxidation by managanese peroxidase (MnP) is reported to decompose recalcitrant polycyclic aromatic hydrocabon (PAH) and nonphenolic lignin models. To elucidate the oxidative process, linoleic acid and 13(S)-hydroperoxy-9Z,11E-octadecadienoic acid [13(S)-HPODE] were reacted with MnPs from Ceriporiopsis subvermispora and Bjerkandera adusta and the free radicals produced were analyzed by ESR. When the MnPs were reacted with 13(S)-HPODE in the presence of Mn(II), H2O2 and tert-nitrosobutane (t-NB), the ESR spectrum contained a sharp triplet of acyl radical (aN = 0.81 mT). Formation of acyl radical was also observed in the reactions of Mn(III)-tartrate with 13(S)-HPODE and with linoleic acid, but the latter reaction occurred explosively after an induction period of around 30 min. Reactions of MnP with linoleic acid in the presence of Mn(II), H2O2 and t-NB gave no spin adducts while addition of t-NB after preincubation of linoleic acid with MnP/Mn(II)/H2O2 for 2 h gave spin adducts of carbon-centered (aN = 1.53 mT, aH = 0.21 mT) and acyl (aN = 0.81 mT) radicals. In contrast to linoleic acid, methyl linoleate and oleic acid were not peroxidized by MnP and chelated Mn(III) within a few hours, indicating that structures containing both the 1,4-pentadienyl moiety and a free carboxyl group are necessary for inducing the peroxidation in a short reaction time. These results indicate that MnP-dependent lipid peroxidation is not initiated by direct abstraction of hydrogen from the bis-allylic position during turnover but proceeds by a Mn(III)-dependent hydrogen abstraction from enols and subsequent propagation reactions involving the formation of acyl radical from lipid hydroperoxide. This finding expands the role of chelated Mn(III) from a phenol oxidant to a strong generator of free radicals from lipids and lipid hydroperoxides in lignin biodegradation. PMID:10866827

Watanabe, T; Katayama, S; Enoki, M; Honda, Y; Kuwahara, M

2000-07-01

279

Free radical mechanisms for the oxidation of substituted ascorbates. A pulse radiolysis study of L-ascorbic acid-2-sulfate  

International Nuclear Information System (INIS)

The oxidations of L-ascorbate 2-sulfate by Br2- and OH radicals generated in aqueous solutions (pH 4.5 to 9.5) were studied by pulse radiolysis. The (2-SO4A).- radical, generated in an electron transfer reaction between Br2- and the parent compound, loses sulfate (tau approx. 500 ?sec) to give ascorbate free radical (A.-) with a G(A.-) = 2.0. The oxidation of L-ascorbate 2sulfate by OH radicals is complex, yielding both (2-SO4A)- and OH radical adducts. Some of these transients subsequently yield A.-. HPLC studies corroborate the overall mechanism postulated for the oxidation of L-ascorbate 2-sulfate by OH radicals

1983-01-01

280

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

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

AÍDA NEIRA

2008-03-01

 
 
 
 
281

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

Scientific Electronic Library Online (English)

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

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

282

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 Br 2·- 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 -/Br 2·- and reactivity of the radicals towards buffers or other nucleophiles.

Madej, Edyta; Wardman, Peter

2006-09-01

283

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

2006-09-01

284

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

285

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

286

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

Science.gov (United States)

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

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

2014-02-01

287

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

Science.gov (United States)

Human catestatin CgA352-372 (SL21) is an endogenous neuropeptide with multiple biological functions. The present study aimed to evaluate the antioxidant, antibacterial, cytotoxic, and DNA damage protective effects of SL21 neuropeptide. SL21 neuropeptide generated from the C-terminus of chromogranin A (CgA) was synthesized by solid-phase method. Synthetic peptide was subjected to various in vitro antioxidant assays including the scavenging of 1,1-diphenyl-2-pycryl-hydrazyl (DPPH), 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(·+) ), and hydroxyl free radicals, metal ion chelation, inhibition of lipid peroxidation, and reducing power. Moreover, protective effect of SL21 on H2 O2 -induced DNA damage was analyzed using pTZ57/RT plasmid. Methylthiazoltetrazolium assay was also performed to study the cytotoxic effect of SL21 neuropeptide on human peripheral blood mononuclear cells. Furthermore, antibacterial and hemolysis assays were conducted. The results demonstrated high activities of SL21 in scavenging free radicals (DPPH, ABTS(·+) , and hydroxyl), chelating of Cu(2+) /Fe(2+) metal ions, reducing power, and inhibition of lipid peroxidation in a concentration-dependent manner. SL21 neuropeptide revealed a protective effect on DNA damage caused by hydroxyl radicals. Interestingly, the peptide exhibited no significant cytotoxicity towards peripheral blood mononuclear cells. Furthermore, SL21 peptide displayed antimicrobial activity against Staphylococcus aureus and Pseudomonas aeruginosa without any hemolytic activity on human red blood cells. Conclusively, the present study established SL21 (catestatin) as a novel antioxidative peptide that could further be investigated for its potential use as a pharmaceutical agent. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd. PMID:24723458

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

2014-06-01

288

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

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

Radhakrishnan Ammu

2010-09-01

289

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

Directory of Open Access Journals (Sweden)

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

Manat CHAIJAN

2010-01-01

290

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

291

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

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

Piming Ma

2014-05-01

292

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

Science.gov (United States)

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

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

2013-12-01

293

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

Energy Technology Data Exchange (ETDEWEB)

The main objective of this investigation was to identify the principal lesions produced by ionizing radiation and autoxidation processes in DNA model compounds. Synthetic deoxynuclei acid oligomers were subjected to ionizing radiation in aqueous solutions. The damage products of d(ApT) irradiated under N{sub 2}O saturation were isolated by reverse phase high performance liquid chromatography in different solvent systems. The major components of the HPLC profile were studied mainly by proton Nuclear Magnetic Resonance spectroscopy. The product profile was dramatically altered when mediators such as oxygen were present. One product, identified as a N-formamido derivative of d(ApT), formed due to the breakdown of the thymine base, was predominant. The presence of radiation protectors markedly altered the products obtained from d(ApT). Two stereoisomers of dihydrothymine derivatives were identified. d(ApT) irradiated in the solid state generated direct damage products which were isolated by HPLC and identified by NMR spectroscopy. A comparative study of the degradation of d(ApT) produced by ionizing radiation and by chemical degradation by autoxidizing agents was carried out. The result showed that the autoxidizing agents produced the same profile of damaged products as ionizing radiation with oxygen present.

Paul, C.R.

1988-01-01

294

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

Directory of Open Access Journals (Sweden)

Full Text Available There is abundant evidence that reactive oxygen species are implicated in several physiological and pathological processes. To protect biological targets from oxidative damage, antioxidants must react with radicáis and other reactive species faster than biological substrates do. The aim of the present study was to determine the in vitro antioxidant activity of aqueous extracts from leaves of Bauhinia forficata Link (Fabaceae - Caesalpinioideae and Cissus sicyoides L. (Vitaceae (two medicinal plants used popularly in the control of diabetes mellitus, using several different assay systems, namely, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS decolorization, superoxide anión radical (0(2•- scavenging and myeloperoxidase (MPO activity. In the ABTS assay for total antioxidant activity, B. forficata showed IC50 = 8.00±0.07 ?g/mL, while C. sicyoides showed IC50 = 13.0±0.2 ?g/mL. However, the extract of C. sicyoides had a stronger effect on 0(2•- (IC50 = 60.0±2.3 ?g/mL than the extract of B. forficata (IC50 = 90.0±4.4 ?g/ mL. B. forficata also had a stronger inhibitory effect on MPO activity, as measured by guaiacol oxidation, than C. sicyoides. These results indicate that aqueous extracts of leaves of B. forficata and C. sicyoides are a potential source of natural antioxidants and may be helpful in the prevention of diabetic complications associated with oxidative stress.

NAJEH M KHALIL

2008-01-01

295

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

Science.gov (United States)

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. PMID:11383624

Fujinami, Y; Tai, A; Yamamoto, I

2001-05-01

296

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

Science.gov (United States)

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

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

2012-11-01

297

Influence of Pb(II) Ions on the EPR Properties of the Semiquinone Radicals of Humic Acids and Model Compounds: High Field EPR and Relativistic DFT Studies  

Science.gov (United States)

X-band (9.76 GHz) and high field (416.00 GHz) electron paramagnetic resonance spectroscopy (EPR) was used to study the interactions between Pb(II) ions and semiquinone radicals of natural humic acids and their simple models. The EPR experiments were performed on powder samples. The formation of Pb(II) complexes with the radicals was accompanied by a significant decrease of g parameters as compared to those observed for parent radicals. Two types of complexes were identified depending on the initial concentration of Pb(II) ions. For one of them the anisotropic hyperfine coupling with the 207Pb nucleus was observed. Systematic DFT calculations were carried out for complexes with different forms of radical ligands (L2-•, HL-•, and H2L•) derived from 3,4-dihydroxybenzoic acid representing different ligation schemes. The g parameters calculated for the structure characterized by a significant accumulation of spin density on the Pb atom are strongly deviated from the values observed experimentally. Moreover, a decrease of the spin population on all oxygen atoms as a result of complexation of Pb(II) via carboxyl oxygens and protonation of hydroxyl oxygens is required to reproduce the experimental g parameters.

Witwicki, Maciej; Jerzykiewicz, Maria; Jaszewski, Adrian R.; Jezierska, Julia; Ozarowski, Andrzej

2009-11-01

298

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

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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

2008-01-01

299

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

Science.gov (United States)

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

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

2013-12-01

300

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Poly(methyl methacrylate) in the brush form is grown from the surface of magnetite nanoparticles by ambient temperature atom transfer radical polymerization (ATATRP) using a phosphonic acid based initiator. The surface initiator was prepared by the reaction of ethylene glycol with 2-bromoisobutyrl bromide, followed by the reaction with phosphorus oxychloride and hydrolysis. This initiator is anchored to magnetite nanoparticles via physisorption. The ATATRP of methyl methacrylate was carried o...

Babu, Kothandapani; Dhamodharan, Raghavachari

2008-01-01

 
 
 
 
301

Effects of ionising radiation on deoxyribonucleic acid. Pt. 6; Effects of hydroxyl radical scavengers on radiation damage to DNA  

Energy Technology Data Exchange (ETDEWEB)

Exposure of dilute aqueous DNA to ionizing radiation at ambient temperatures results in indirect damage to the DNA, major reactions being the addition of {sup .}OH radicals to DNA bases and abstraction of C-H hydrogen atoms from deoxyribose units. In order to concentrate on direct damage processes, we have studied frozen aqueous solutions, but it remains possible that some damage is still caused by {sup .}OH radicals generated close to DNA molecules. In order to check this, we have used two {sup .}OH radical scavengers, dimethyl sulphoxide (DMSO) and t-butyl alcohol (TBA). For both, in low concentrations ({le}1 : 1, base-pair), the damage is confined to DNA and exactly corresponds to normal damage in the absence of scavengers. In a second series of experiments, solid solutions containing hydrogen peroxide were photolysed with UV light at 77 K. This gave a poorly defined sextet assigned to sugar radicals or possibly to thymine {sup .}OH-radical adducts, which was not detected in the absence of hydrogen peroxide, or during {gamma}-radiolysis. We conclude that hydroxyl radical attack is not important for fully hydrated frozen DNA. The nature and significance of a range of other radicals detected in DNA solutions more concentrated in DMSO and TBA are also discussed, together with the identification of a species giving a broad singlet in the hydrogen peroxide studies. (author).

Cullis, P.M.; Langman, S.; Podmore, I.D.; Symons, M.C.R. (Leicester Univ. (UK). Dept. of Chemistry)

1990-10-07

302

ABT-737 promotes the dislocation of ER luminal proteins to the cytosol, including pseudomonas exotoxin.  

Science.gov (United States)

Impaired apoptosis is often a key element in tumor development. Therefore, drugs mimicking prosurvival antagonists offer promise as cancer therapeutics. When ABT-737, a BH3-only mimetic, was added to KB3-1 human cervical adenocarcinoma cells, we noted an induction of an endoplasmic reticulum (ER) stress response and the dislocation of ER luminal proteins, including chaperones, to the cell cytosol. Furthermore, when immunotoxin (antibody-toxin chimeric molecule) and ABT-737 combinations were added to cells, there was enhanced toxin-mediated inhibition of protein synthesis, consistent with enhanced translocation of toxin to the cytosol. A similar enhancement was not seen with thapsigargin, suggesting that ER stress alone was not responsible for enhanced translocation. Cytosol preparations from ABT-737-treated but not from thapsigargin-treated cells revealed the presence of greater amounts of processed 37-kDa toxin fragment compared with the addition of immunotoxin alone. As early as 4 hours after the addition of ABT-737 and immunotoxin, there was release of mitochondrial cytochrome c and activation of caspase-3/7 indicating that the combination caused apoptotic cell death. These results were reflected in decreased cellular ATP levels that were noted with combinations of ABT-737 and immunotoxin but not with either agent alone or with combinations of thapsigargin and immunotoxin. We conclude that ABT-737 increases ER permeability, promoting the dislocation of toxin from the ER to the cytosol resulting in early apoptotic cell death. These mechanistic insights suggest why this class of BH3-only mimetic synergizes in a particular way with Pseudomonas exotoxin-based immunotoxins. PMID:24739394

Antignani, Antonella; Sarnovsky, Robert; FitzGerald, David J

2014-06-01

303

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

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

B. H. Czader

2012-02-01

304

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

Directory of Open Access Journals (Sweden)

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

B. H. Czader

2012-08-01

305

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

Energy Technology Data Exchange (ETDEWEB)

Purpose: Poly(ADP-ribose) polymerase plays a critical role in the recognition and repair of DNA single-strand breaks and double-strand breaks (DSBs). ABT-888 is an orally available inhibitor of this enzyme. This study seeks to evaluate the use of ABT-888 combined with chemotherapy and radiation therapy (RT) in colorectal carcinoma models. Methods and Materials: RT clonogenic assays were performed on HCT116 and HT29 cells treated with 5-fluorouracil, irinotecan, or oxaliplatin with or without ABT. The surviving fraction at 2 Gy and dose-modifying factor at 10% survival were analyzed. Synergism was assessed by isobologram analysis for combination therapies. ?H2AX and neutral comet assays were performed to assess the effect of therapy on DSB formation/repair. In vivo assessments were made by use of HCT116 cells in a xenograft mouse model. Tumor growth delay was measured at a volume of 500 mm{sup 3}. Results: Both lines were radiosensitized by ABT alone, and ABT further increased chemotherapy dose-modifying factors to the 1.6 to 1.8 range. All combinations were synergistic (combination indices <0.9). ABT treatment significantly increased DSB after RT (?H2AX, 69% vs 43%; P=.017) and delayed repair. We found tumor growth delays of 7.22 days for RT; 11.90 days for RT and ABT; 13.5 days for oxaliplatin, RT, and ABT; 14.17 days for 5-fluorouracil, RT, and ABT; and 23.81 days for irinotecan, RT, and ABT. Conclusion: ABT-888 radiosensitizes at similar or higher levels compared with classic chemotherapies and acts synergistically with these chemotherapies to enhance RT effects. In vivo confirmation of these results indicates a potential role for combining its use with existing chemoradiation regimens.

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

2013-07-01

306

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

International Nuclear Information System (INIS)

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

2013-07-01

307

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

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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

2013-01-01

308

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2002-12-15

309

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

310

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

Science.gov (United States)

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 were 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. PMID:24060682

Franck, Thierry; Mouithys-Mickalad, Ange; Robert, Thierry; Ghitti, Gianangelo; Deby-Dupont, Ginette; Neven, Philippe; Serteyn, Didier

2013-11-25

311

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

Science.gov (United States)

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

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

2013-10-01

312

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

313

Physiology of free radicals  

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

Stevanovi? Jelka

2011-01-01

314

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

315

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

Science.gov (United States)

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

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

2012-12-19

316

Sensitization of BCL-2-expressing breast tumors to chemotherapy by the BH3 mimetic ABT-737.  

Science.gov (United States)

Overexpression of the prosurvival protein BCL-2 is common in breast cancer. Here we have explored its role as a potential therapeutic target in this disease. BCL-2, its anti-apoptotic relatives MCL-1 and BCL-XL, and the proapoptotic BH3-only ligand BIM were found to be coexpressed at relatively high levels in a substantial proportion of heterogeneous breast tumors, including clinically aggressive basal-like cancers. To determine whether the BH3 mimetic ABT-737 that neutralizes BCL-2, BCL-XL, and BCL-W had potential efficacy in targeting BCL-2-expressing basal-like triple-negative tumors, we generated a panel of primary breast tumor xenografts in immunocompromised mice and treated recipients with either ABT-737, docetaxel, or a combination. Tumor response and overall survival were significantly improved by combination therapy, but only for tumor xenografts that expressed elevated levels of BCL-2. Treatment with ABT-737 alone was ineffective, suggesting that ABT-737 sensitizes the tumor cells to docetaxel. Combination therapy was accompanied by a marked increase in apoptosis and dissociation of BIM from BCL-2. Notably, BH3 mimetics also appeared effective in BCL-2-expressing xenograft lines that harbored p53 mutations. Our findings provide in vivo evidence that BH3 mimetics can be used to sensitize primary breast tumors to chemotherapy and further suggest that elevated BCL-2 expression constitutes a predictive response marker in breast cancer. PMID:21768359

Oakes, Samantha R; Vaillant, François; Lim, Elgene; Lee, Lily; Breslin, Kelsey; Feleppa, Frank; Deb, Siddhartha; Ritchie, Matthew E; Takano, Elena; Ward, Teresa; Fox, Stephen B; Generali, Daniele; Smyth, Gordon K; Strasser, Andreas; Huang, David C S; Visvader, Jane E; Lindeman, Geoffrey J

2012-02-21

317

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

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

Hassan Dariushnejad

2014-03-01

318

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

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

Dariushnejad, Hassan; Zarghami, Nosratallah; Rahmati, Mohammad; Ghasemali, Samaneh; Sadeghi, Zohreh; Davoodi, Zahra; Jafari Tekab, Hossein; Gandomkar Ghalhar, Masoud

2014-01-01

319

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.

Elena E. Stashenko

2007-01-01

320

The gas-phase acidity of 2(3H)-oxepinone: a step toward an experimental heat of formation for the 2-oxepinoxy radical.  

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In an effort to gain further insight into the oxidation of the phenyl radical, this contribution details the first of three experiments designed to establish the heat of formation of the 2-oxepinoxy radical. We report here the synthesis of the previously unknown 2(7H)-oxepinone (12a) and 2(3H)-oxepinone (12b). We have determined the gas-phase acidity (Delta(acid)H(298)) of 12b by means of a bracketing study employing a flowing afterglow apparatus with quadrupole mass spectrometric detection. In this experiment, compound 12b was reacted in the gas phase with a series of bases of varying strength. A proton-transfer reaction was observed when 12b was reacted with t-BuS(-), but not when 12b was reacted with HS(-). We conclude that the gas-phase acidity of 12b lies between those of t-BuSH and H(2)S, and it is thereby assigned a value of Delta(acid)H(298) = 352 +/- 2 kcal/mol. Additional support for this value was found by performing the reverse reactions (i.e. the 2-oxepinoxy anion (15a) was reacted with proton sources of differing acidities). Anion 15a underwent a proton-transfer reaction with H(2)S but not with t-BuSH, in agreement with the results from the forward reactions. The experimental value of the gas-phase acidity agrees well with those from DFT calculations, which predicted Delta(acid)H(298) = 348.9 kcal/mol at the B3LYP/6-31+G(d) level and 349.2 kcal/mol at the B3LYP/aug-cc-pVTZ level. PMID:15898796

Kroner, Steven M; Dematteo, Matthew P; Hadad, Christopher M; Carpenter, Barry K

2005-05-25

 
 
 
 
321

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

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

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

2013-07-17

322

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

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

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

2009-01-01

323

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

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

Chung Pin Liang

2014-04-01

324

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

Science.gov (United States)

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

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

2014-01-01

325

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

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

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

1997-04-01

326

Chemical aspects of radiosensitization. Reaction of sensitizers with radicals produced in the radiolysis of aqueous solutions of nucleic acid components  

International Nuclear Information System (INIS)

The effects of oxidants (sensitizers) in the radiolysis of aqueous solutions of pyrimidine and purine bases have been investigated. Their influence on the nature of the permanent radiolysis products and on the kinetics of disappearance of transient intermediates is reported. Particular attention has been paid to the chemical fates of carbocationic intermediates which can be produced from radical-sensitizer interaction. (author)

1978-01-01

327

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

Science.gov (United States)

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

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

2012-01-01

328

The effects of ABT-491 administration on visual evoked potentials in rat model of hypoxic ischemic brain injury - Original Article  

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Full Text Available Aim: In the present study, we aimed to investigate the effects of ABT-491 on visual evoked potentials (VEP in rat model of hypoxic ischemic brain injury (HIBI. Material and Method: Fifty-seven male Wistar newborn rats were used in this study. Animals were divided into three groups randomly. HIBI was formed on postnatal seventh day according to modified Levine-Rice model in 1st (n=18 and 2nd (n=20 groups. Third group (n=19 served as sham group. After HIBI, ABT-491 was applied intraperitoneally to rats in the 1st group (ABT group and saline was administered to the rats in the 2nd group (saline group. On postnatal 16th weeks, VEPs were recorded from Ag-AgCl disc electrode placed on the occipital region. Results: The latencies of P3 wave were shorter in the ABT group than the saline group (p<0.05. Peak-to-peak amplitudes of P2-N2 and N2-P3 were smaller in the ABT and saline groups compared to the sham group (for all pairwise comparisons p<0.001.Conclusions:It was concluded that HIBI caused a decrement in amplitudes of VEP responses and this change could not be ameliorated with ABT-491. However, shortening in latencies of P3 wave could be ameliorated with ABT-491 treatment after HIBI was formed. (Turk Arch Ped 2010; 45: 319-23

Tolgay Ergeno?lu

2010-12-01

329

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

International Nuclear Information System (INIS)

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

2012-02-01

330

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

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Activation of T-type Ca(2+) channels contributes to nociceptive signaling by facilitating action potential bursting and modulation of membrane potentials during periods of neuronal hyperexcitability. The role of T-type Ca(2+) channels in chronic pain is supported by gene knockdown studies showing that decreased Cav3.2 channel expression results in the loss of low voltage-activated (LVA) currents in dorsal root ganglion (DRG) neurons and attenuation of neuropathic pain in the chronic constriction injury (CCI) model. ABT-639 is a novel, peripherally acting, selective T-type Ca(2+) channel blocker. ABT-639 blocks recombinant human T-type (Cav3.2) Ca(2+) channels in a voltage-dependent fashion (IC50=2?M) and attenuates LVA currents in rat DRG neurons (IC50=8?M). ABT-639 was significantly less active at other Ca(2+) channels (e.g. Cav1.2 and Cav2.2) (IC50>30?M). ABT-639 has high oral bioavailability (%F=73), low protein binding (88.9%) and a low brain:plasma ratio (0.05:1) in rodents. Following oral administration ABT-639 produced dose-dependent antinociception in a rat model of knee joint pain (ED50=2mg/kg, p.o.). ABT-639 (10-100mg/kg, p.o.) also increased tactile allodynia thresholds in multiple models of neuropathic pain (e.g. spinal nerve ligation, CCI, and vincristine-induced, and capsaicin secondary hypersensitivity). ABT-639 did not attenuate hyperalgesia in inflammatory pain models induced by complete Freund's adjuvant or carrageenan. At higher doses (e.g. 100 - 300mg/kg) ABT-639 did not significantly alter hemodynamic or psychomotor function. The antinociceptive profile of ABT-639 provides novel insights into the role of peripheral T-type (Cav3.2) channels in chronic pain states. PMID:24726441

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

2014-06-15

331

Ion Radicals. X. The Formation of the Phenothiazinyl Radical by the Ultraviolet Irradiation of Phenothiazine Solutions.  

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The irradiation by ultraviolet light of solutions of phenothiazine in ethanol cause the formation of a radical. The e.s.r. spectrum of this radical was interpreted as that of the neutral phenothiazinyl radical. Addition of acid to the radical solution cau...

H. J. Shine C. Veneziani E. E. Mach

1966-01-01

332

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

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

2010-01-01

333

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

Science.gov (United States)

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

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

2012-12-19

334

Aqueous-phase photolysis of biacetyl (An ?-dicarbonyl compound): A sink for biacetyl, and a source of acetic acid, peroxyacetic acid, hydrogen peroxide, and the highly oxidizing acetylperoxyl radical in aqueous aerosols, fogs, and clouds  

Science.gov (United States)

Aqueous-phase photolysis of biacetyl represents a heretofore uncharacterized sink for biacetyl and source of organic acids and peroxides to aqueous aerosols, and fog and cloud drops. The photolysis half-life of aqueous-phase biacetyl is approximately 1.0-1.6 h for a solar zenith angle of 36° (midday equinox sunlight in Durham, NC). Major products of aqueous biacetyl photolysis are acetic acid, peroxyacetic acid, and hydrogen peroxide. Pyruvic acid and methylhydroperoxide are minor photoproducts. Common atmospheric reductants (H-atom donors), such as formate, formaldehyde, glyoxal, phenol (as a model for phenolic compounds) and ?- D-glucose (as a model for carbohydrates), substantially increase the quantum yields of peroxyacetic acid Formate also significantly increases the quantum yields of hydrogen peroxide. The highly oxidizing acetylperoxyl radical is proposed as a key intermediate in the photolysis of aqueous biacetyl. The sources and reactions of acetylperoxyl radicals in aqueous aerosols, fogs, and clouds should be investigated in future studies of atmospheric water-drop chemistry.

Faust, Bruce C.; Powell, Kendall; Rao, C. Janakiram; Anastasio, Cort

335

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

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

Yuliana Markovska

2012-08-01

336

Superoxide radical anion adduct of 5,5-dimethyl-1-pyrroline n-oxide (DMPO). 1. The thermodynamics of formation and its acidity.  

Science.gov (United States)

The nitrone 5,5-dimethyl-1-pyrroline N-oxide (DMPO) has been the most widely used spin trap for the detection of transient free radicals in chemical, biological, and biomedical research using electron paramagnetic resonance (EPR) spectroscopy. A density functional theory (DFT) approach was used to predict the thermodynamics of formation of the superoxide anion/hydroperoxyl radical (O2*-/*O2H) adduct of DMPO as well as its pK(a) in aqueous systems. At the B3LYP/6-31+G(d,p)//B3LYP/6-31G(d) level, we predicted (in the gas phase and with a polarizable continuum model (PCM) for water) three conformational minima for both the DMPO-O2- and DMPO-O2H adducts. Using DFT and the PCM solvation method, the pK(a) of DMPO-O2H was predicted to be 14.9 +/- 0.5. On the basis of free energy considerations, the formation of DMPO-O2H at neutral pH proceeds via initial addition of O2*- to DMPO to form the DMPO-O2- adduct and then subsequent protonation by water (or other acidic sources) to form DMPO-O2H. Under acidic conditions, the addition of *O2H to DMPO is predicted to be more exoergic than the addition of O2*- and is consistent with available experimental kinetic data. PMID:16833945

Villamena, Frederick A; Merle, John K; Hadad, Christopher M; Zweier, Jay L

2005-07-14

337

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

Science.gov (United States)

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

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

2006-05-01

338

Scavenging effects of dexrazoxane on free radicals.  

Science.gov (United States)

Dexrazoxane (ICRF-187) has been clinically used to reduce doxorubicin-induced cardiotoxicity for more than 20 years. It has been proposed that dexrazoxane may act through its rings-opened hydrolysis product ADR-925, which can either remove iron from the iron-doxorubicin complex or bind to free iron, thus preventing iron-based oxygen radical formation. However, it is not known whether the antioxidant actions of dexrazoxane are totally dependent on its metabolization to its rings-opened hydrolysis product and whether dexrazoxane has any effect on the iron-independent oxygen free radical production. In this study, we examined the scavenging effect of dexrazoxane on hydroxyl, superoxide, lipid, DPPH and ABTS(+) free radicals in vitro solution systems. The results demonstrated that dexrazoxane was an antioxidant that could effectively scavenge these free radicals and the scavenging effects of dexrazoxane did not require the enzymatic hydrolysis. In addition, dexrazoxane was capable to inhibit the generation superoxide and hydroxyl radicals in iron free reaction system, indicating that the antioxidant properties of dexrazoxane were not solely dependent on iron chelation. Thus the application of dexrazoxane should not be limited to doxorubicin-induced cardiotoxicity. Instead, as an effective antioxidant that has been clinically proven safe, dexrazoxane may be used in a broader spectrum of diseases that are known to be benefited by antioxidant treatments. PMID:21103033

Junjing, Zhang; Yan, Zhao; Baolu, Zhao

2010-11-01

339

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

Science.gov (United States)

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

Hwang, Eun-Sun; Thi, Nhuan Do

2014-01-01

340

The BH3 mimetic ABT-737 increases treatment efficiency of paclitaxel against hepatoblastoma  

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Abstract Background The primary goal of current chemotherapy in hepatoblastoma (HB) is reduction of tumour volume and vitality to enable complete surgical resection and reduce risk of recurrence or metastatic disease. Drug resistance remains a major challenge for HB treatment. In some malignancies inhibition of anti-apoptotic pathways using small BH3 mimetic molecules like ABT-737 shows synergistic effects in combination with cystotoxic agents in vitro. Now we analysed toxico...

Lieber Justus; Eicher Carmen; Wenz Julia; Kirchner Bettina; Warmann Steven W; Fuchs Jörg; Armeanu-Ebinger Sorin

2011-01-01

 
 
 
 
341

The BH3 mimetic ABT-737 increases treatment efficiency of paclitaxel against hepatoblastoma  

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Full Text Available Abstract Background The primary goal of current chemotherapy in hepatoblastoma (HB is reduction of tumour volume and vitality to enable complete surgical resection and reduce risk of recurrence or metastatic disease. Drug resistance remains a major challenge for HB treatment. In some malignancies inhibition of anti-apoptotic pathways using small BH3 mimetic molecules like ABT-737 shows synergistic effects in combination with cystotoxic agents in vitro. Now we analysed toxicology and synergistic effects of this approach in HB cells and HB xenografts. Methods Viability was monitored in HB cells (HUH6 and HepT1 and fibroblasts treated with paclitaxel, ABT-737 and a combination of both in a MTT assay. HUH6 xenotransplants in NOD/LtSz-scid IL2R?null mice (NSG were treated accordingly. Tumour volume and body weight were monitored. Xenografted tumours were analysed by histology and immunohistochemistry (Ki-67 and TUNEL assay. Results ABT-737 reduced viability in HUH6 and HepT1 cells cultures at concentrations above 1 ?M and also enhanced the cytotoxic effect of paclitaxel when used in combination. Thereby paclitaxel could be reduced tenfold to achieve similar reduction of viability of tumour cells. In contrast no toxicity in fibroblasts was observed at the same regiments. Subcutaneous HB (HUH6 treated with paclitaxel (12 mg/kg body weight, n = 7 led to delayed tumour growth in the beginning of the experiment. However, tumour volume was similar to controls (n = 5 at day 25. Combination treatment with paclitaxel and ABT-737 (100 mg/kg, n = 8 revealed significantly 10 fold lower relative tumour volumes compared to control and paclitaxel groups. Paclitaxel dependent toxicity was observed in this mice strain. Conclusions Our results demonstrate enhancement of chemotherapy by using modulators of apoptosis. Further analyses should include improved pharmacological formulations of paclitaxel and BH3 mimetics in order to reduce toxicological effects. Sensitising HB to apoptosis may also render resistant HB susceptible to established chemotherapy regimens.

Fuchs Jörg

2011-08-01

342

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 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, resi...

Dorota Martysiak-?urowska; Weronika Wenta

2012-01-01

343

Discovery of ABT-267, a pan-genotypic inhibitor of HCV NS5A.  

Science.gov (United States)

We describe here N-phenylpyrrolidine-based inhibitors of HCV NS5A with excellent potency, metabolic stability, and pharmacokinetics. Compounds with 2S,5S stereochemistry at the pyrrolidine ring provided improved genotype 1 (GT1) potency compared to the 2R,5R analogues. Furthermore, the attachment of substituents at the 4-position of the central N-phenyl group resulted in compounds with improved potency. Substitution with tert-butyl, as in compound 38 (ABT-267), provided compounds with low-picomolar EC50 values and superior pharmacokinetics. It was discovered that compound 38 was a pan-genotypic HCV inhibitor, with an EC50 range of 1.7-19.3 pM against GT1a, -1b, -2a, -2b, -3a, -4a, and -5a and 366 pM against GT6a. Compound 38 decreased HCV RNA up to 3.10 log10 IU/mL during 3-day monotherapy in treatment-naive HCV GT1-infected subjects and is currently in phase 3 clinical trials in combination with an NS3 protease inhibitor with ritonavir (r) (ABT-450/r) and an NS5B non-nucleoside polymerase inhibitor (ABT-333), with and without ribavirin. PMID:24400777

DeGoey, David A; Randolph, John T; Liu, Dachun; Pratt, John; Hutchins, Charles; Donner, Pamela; Krueger, A Chris; Matulenko, Mark; Patel, Sachin; Motter, Christopher E; Nelson, Lissa; Keddy, Ryan; Tufano, Michael; Caspi, Daniel D; Krishnan, Preethi; Mistry, Neeta; Koev, Gennadiy; Reisch, Thomas J; Mondal, Rubina; Pilot-Matias, Tami; Gao, Yi; Beno, David W A; Maring, Clarence J; Molla, Akhter; Dumas, Emily; Campbell, Andrew; Williams, Laura; Collins, Christine; Wagner, Rolf; Kati, Warren M

2014-03-13

344

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

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

Bojan Matijevi?

2010-09-01

345

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  

Science.gov (United States)

The reactions of rad OH, H rad and e aq- 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 rad 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( rad OH+2,4,5-T)=6.4 (±0.5)×10 9 mol dm -3 s -1 and k( rad OH+MCPA)=8.5 (±0.8)×10 9 mol dm -3 s -1. The radiation induced decomposition of the pesticides, chloride- and product formation (phenolic compounds, aliphatic acids) was studied by gamma radiolysis as a function of dose. A mechanism for acetate formation is discussed. The presence of oxygen during irradiation affected the decomposition rate only indiscernibly, however, chloride elimination, ring fragmentation (formation of aliphatic acids), TOC- and toxicity reduction were strongly enhanced. For complete removal of 500 ?mol dm -3 herbicides a dose of ˜4 kGy was required. Using air saturation during irradiation a reduction of 37-40% of the TOC was observable at 5 kGy, detoxification (luminescence inhibition <20%) was achieved with 10 kGy.

Zona, Robert; Solar, Sonja; Sehested, Knud

2012-02-01

346

ABT-869, a multitargeted receptor tyrosine kinase inhibitor: inhibition of FLT3 phosphorylation and signaling in acute myeloid leukemia.  

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In 15% to 30% of patients with acute myeloid leukemia (AML), aberrant proliferation is a consequence of a juxtamembrane mutation in the FLT3 gene (FMS-like tyrosine kinase 3-internal tandem duplication [FLT3-ITD]), causing constitutive kinase activity. ABT-869 (a multitargeted receptor tyrosine kinase inhibitor) inhibited the phosphorylation of FLT3, STAT5, and ERK, as well as Pim-1 expression in MV-4-11 and MOLM-13 cells (IC(50) approximately 1-10 nM) harboring the FLT3-ITD. ABT-869 inhibited the proliferation of these cells (IC(50) = 4 and 6 nM, respectively) through the induction of apoptosis (increased sub-G(0)/G(1) phase, caspase activation, and PARP cleavage), whereas cells harboring wild-type (wt)-FLT3 were less sensitive. In normal human blood spiked with AML cells, ABT-869 inhibited phosphorylation of FLT3 (IC(50) approximately 100 nM), STAT5, and ERK, and decreased Pim-1 expression. In methylcellulose-based colony-forming assays, ABT-869 had no significant effect up to 1000 nM on normal hematopoietic progenitor cells, whereas in AML patient samples harboring both FLT3-ITD and wt-FLT3, ABT-869 inhibited colony formation (IC(50) = 100 and 1000 nM, respectively). ABT-869 dose-dependently inhibited MV-4-11 and MOLM-13 flank tumor growth, prevented tumor formation, regressed established MV-4-11 xenografts, and increased survival by 20 weeks in an MV-4-11 engraftment model. In tumors, ABT-869 inhibited FLT3 phosphorylation, induced apoptosis (transferase-mediated dUTP nick-end labeling [TUNEL]) and decreased proliferation (Ki67). ABT-869 is under clinical development for AML. PMID:17209055

Shankar, Deepa B; Li, Junling; Tapang, Paul; Owen McCall, J; Pease, Lori J; Dai, Yujia; Wei, Ru-Qi; Albert, Daniel H; Bouska, Jennifer J; Osterling, Donald J; Guo, Jun; Marcotte, Patrick A; Johnson, Eric F; Soni, Niru; Hartandi, Kresna; Michaelides, Michael R; Davidsen, Steven K; Priceman, Saul J; Chang, Jenny C; Rhodes, Katrin; Shah, Neil; Moore, Theodore B; Sakamoto, Kathleen M; Glaser, Keith B

2007-04-15

347

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

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

J Sharma

2012-12-01

348

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

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

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

2006-01-01

349

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

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

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

2005-01-01

350

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

Science.gov (United States)

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

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

2012-08-01

351

[Free radicals and HIV infection].  

Science.gov (United States)

In HIV infected patients, the increase of the concentration of free radicals is related to: a depletion of protective system (glutathione peroxidase, superoxide dismutase, vitamin E, selenium ...), and an increased production of free radicals (superoxide anion, hydrogen peroxide, hydroxil radical) consecutive to the activation of lymphocytes and phagocyting cells, the chronic inflammation, the increased polyinsatured fatty acids concentration and lipoperoxidation, and direct or indirect effect of several pathologic agents including Mycoplasma sp. This free radical excess could impair cell membranes and generate apoptosis, the main cause of lymphocytes CD4+ depletion. After a brief review of the free radicals synthesis pathway, their potential deleterious effects and the protective systems, the role of free radicals in the pathogenesis of HIV infection are discussed in regard to data reported in the literature. PMID:9499916

Rabaud, C; Tronel, H; Fremont, S; May, T; Canton, P; Nicolas, J P

1997-01-01

352

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

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

Ang Zhang

2011-12-01

353

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2002-01-01

354

Kinetics and mechanism for the oxidation of ascorbic acid/ascorbate by HO"2/O"2"- radicals. A pulse radiolysis and stopped-flow photolysis study  

International Nuclear Information System (INIS)

The reaction between ascorbic acid/ascorbate and molecular oxygen and its derivatives (HO"2/O"2"-) (AH"2/AH"-) was followed from pH 0.3 to 11, leading to the following rate constants: kappa"8 = 1.6 x 10_4 M"-_1 s"-_1 for the reaction between AH"2 and HO"2, kappa"1"7 + 0.365 kappa"1"8 = 1.22 x 10_7 M"-_1 s"-_1 for the reactions between AH"- and HO"2 and AH"2 and O"2"-, respectively, and kappa"1"9 = 5 x 10_4 M"-_1 s"-_1 for the reaction between AH"- and O"2"-. The radical-radical reactions of A"- with HO"2 and O"2"- were measured and found to proceed at rates of kappa"9 = 5 x 10_9 s"-_1 and kappa"1"1 = 2.6 x 10_8 M"-_1 s"-_1, respectively. An overall mechanism for the oxidation of AH"2/AH"- by HO"2/O"2"- consistent with the experimental results is also proposed. 1 figure, 1 table

1983-05-12

355

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

Science.gov (United States)

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

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

2013-03-15

356

Preclinical discovery of candidate genes to guide pharmacogenetics during phase I development: the example of the novel anticancer agent ABT-751  

Science.gov (United States)

Objective ABT-751, a novel orally available antitubulin agent, is mainly eliminated as inactive glucuronide (ABT-751G) and sulfate (ABT-751S) conjugates. We performed a pharmacogenetic investigation of ABT-751 pharmacokinetics using in-vitro data to guide the selection of genes for genotyping in a phase I trial of ABT-751. Methods UDP-glucuronosyltransferase (UGT) and sulfotransferase (SULT) enzymes were screened for ABT-751 metabolite formation in vitro. Forty-seven cancer patients treated with ABT-751 were genotyped for 21 variants in these genes. Results UGT1A1, UGT1A4, UGT1A8, UGT2B7, and SULT1A1 were found to be involved in the formation of inactive ABT-751 glucuronide (ABT-751G) and sulfate (ABT-751S). SULT1A1 copy number (> 2) was associated with an average 34% increase in ABT-751 clearance (P= 0.044), an 18% reduction in ABT-751 AUC (P = 0.045), and a 50% increase in sulfation metabolic ratios (P=0.025). UGT1A8 rs6431558 was associated with a 28% increase in glucuronidation metabolic ratios (P =0.022), and UGT1A4*2 was associated with a 65% decrease in ABT-751 Ctrough (P = 0.009). Conclusion These results might represent the first example of a clinical pharmacokinetic effect of the SULT1A1 copy number variant on the clearance of a SULT1A1 substrate. A-priori selection of candidate genes guided by in-vitro metabolic screening enhanced our ability to identify genetic determinants of interpatient pharmacokinetic variability.

Innocenti, Federico; Ramirez, Jacqueline; Obel, Jennifer; Xiong, Julia; Mirkov, Snezana; Chiu, Yi-Lin; Katz, David A.; Carr, Robert A.; Zhang, Wei; Das, Soma; Adjei, Araba; Moyer, Ann M.; Chen, Pei Xian; Krivoshik, Andrew; Medina, Diane; Gordon, Gary B.; Ratain, Mark J.; Sahelijo, Leonardo; Weinshilboum, Richard M.; Fleming, Gini F.; Bhathena, Anahita

2013-01-01

357

The Bcl-2/xL inhibitor ABT-263 increases the stability of Mcl-1 mRNA and protein in hepatocellular carcinoma cells  

Science.gov (United States)

Background Hepatocellular carcinoma (HCC) is one of the major causes of mortality. ABT-263 is a newly synthesized, orally available Bcl-2/xL inhibitor that shows promising efficacy in HCC therapy. ABT-263 inhibits the anti-apoptotic activity of Bcl-2 and Bcl-xL, but not Mcl-1. Previous reports have shown that ABT-263 upregulates Mcl-1 in various cancer cells, which contributes to ABT-263 resistance in cancer therapy. However, the associated mechanisms are not well known. Methods Western blot, RNAi and CCK-8 assays were used to investigate the relationship between Mcl-1 upregulation and ABT-263 sensitivity in HCC cells. Real-time PCR and Western blot were used to detect Mcl-1 mRNA and protein levels. Luciferase reporter assay and RNA synthesis inhibition assay were adopted to analyze the mechanism of Mcl-1 mRNA upregulation. Western blot and the inhibition assays for protein synthesis and proteasome were used to explore the mechanisms of ABT-263-enhanced Mcl-1 protein stability. Trypan blue exclusion assay and flow cytometry were used to examine cell death and apoptosis. Results ABT-263 upregulated Mcl-1 mRNA and protein levels in HCC cells, which contributes to ABT-263 resistance. ABT-263 increased the mRNA level of Mcl-1 in HCC cells by enhancing the mRNA stability without influencing its transcription. Furthermore, ABT-263 increased the protein stability of Mcl-1 through promoting ERK- and JNK-induced phosphorylation of Mcl-1Thr163 and increasing the Akt-mediated inactivation of GSK-3?. Additionally, the inhibitors of ERK, JNK or Akt sensitized ABT-263-induced apoptosis in HCC cells. Conclusions ABT-263 increases Mcl-1 stability at both mRNA and protein levels in HCC cells. Inhibition of ERK, JNK or Akt activity sensitizes ABT-263-induced apoptosis. This study may provide novel insights into the Bcl-2-targeted cancer therapeutics.

2014-01-01

358

Synthesis of novel folic acid-functionalized biocompatible block copolymers by atom transfer radical polymerization for gene delivery and encapsulation of hydrophobic drugs.  

Science.gov (United States)

Two synthetic routes to folic acid (FA)-functionalized diblock copolymers based on 2-(methacryloyloxy)ethyl phosphorylcholine [MPC] and either 2-(dimethylamino)ethyl methacrylate [DMA] or 2-(diisopropylamino)ethyl methacrylate [DPA] were explored. The most successful route involved atom transfer radical polymerization (ATRP) of MPC followed by the tertiary amine methacrylate using a 9-fluorenylmethyl chloroformate (Fmoc)-protected ATRP initiator. Deprotection of the Fmoc groups produced terminal primary amine groups, which were conjugated with FA to produce two series of novel FA-functionalized biocompatible block copolymers. Nonfunctionalized MPC-DMA diblock copolymers have been previously shown to be effective synthetic vectors for DNA condensation; thus, these FA-functionalized MPC-DMA diblock copolymers appear to be well suited to gene therapy applications based on cell targeting strategies. In contrast, the FA-MPC-DPA copolymers are currently being evaluated as pH-responsive micellar vehicles for the delivery of highly hydrophobic anticancer drugs. PMID:15762681

Licciardi, M; Tang, Y; Billingham, N C; Armes, S P; Lewis, A L

2005-01-01

359

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 chemistry in urban areas is altitude dependent. Measurements at one altitude, for example at the ground, where most air quality monitoring stations are located, are not representative for the rest of the NBL. Our model also revealed that radical chemistry is, in general, altitude dependent at night. We distinguish three regions: an unreactive, NO rich, ground layer; an upper, O3 and NO3 dominated layer, and a reactive mixing layer, where RO2 radicals are mixed from aloft with NO from the ground. In this reactive layer an active radical chemistry and elevated OH radical levels can be found. The downward transport of N2O5 and HO2NO2, followed by their thermal decay, was also identified as a radical source in this layer. Our observations also gave insight into the formation of HONO in the NBL. Based on our field experiments we were able to show that the NO2 to HONO conversion was relative humidity dependent. While this fact was well known, we found that it is most likely the uptake of HONO onto surfaces which is R.H. dependent, rather than the NO2 to HONO conversion. This finding led to the proposal of a new NO2 to HONO conversion mechanism, which is based on solid physical chemical principles. Noteworthy is also the observation of enhanced NO2 to HONO conversion during a dust storm event in Phoenix. The final activity in our project investigated the influence of the urban canopy, i.e. building walls and surfaces, on nocturnal chemistry. For the first time the surface area of a city was determined based on a Geographical Information System database of the city of Santa Monica. The surface to volume areas found in this study showed that, in the 2 lower part of the NBL, buildings provide a much larger surface area than the aerosol. In addition, buildings take up a considerable amount of the volume near the ground. The expansion of our model and sensitivity studies based on the Santa Monica data revealed that the surface area of buildings considerably influences HONO levels in urban areas. The volume reduction leads to a decrease of O3 and an increase of NO2 near the ground due to the stronger impact o

Jochen Stutz

2005-05-24

360

Sensitization of BCL-2–expressing breast tumors to chemotherapy by the BH3 mimetic ABT-737  

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Overexpression of the prosurvival protein BCL-2 is common in breast cancer. Here we have explored its role as a potential therapeutic target in this disease. BCL-2, its anti-apoptotic relatives MCL-1 and BCL-XL, and the proapoptotic BH3-only ligand BIM were found to be coexpressed at relatively high levels in a substantial proportion of heterogeneous breast tumors, including clinically aggressive basal-like cancers. To determine whether the BH3 mimetic ABT-737 that neutralizes BCL-2, BCL-XL, ...

2012-01-01

 
 
 
 
361

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

International Nuclear Information System (INIS)

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

1996-07-01

362

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

International Nuclear Information System (INIS)

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

2008-08-01

363

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

Science.gov (United States)

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

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

2013-12-01

364

Radical-radical reaction dynamics  

Science.gov (United States)

We present an overview of our recent studies of the gas-phase reaction dynamics of O(3P) with a series of hydrocarbon radicals [allyl (C3H5), propargyl (C3H3), t-butyl (t-C4H9)] as prototypal radical-radical oxidation reactions. High-resolution laser spectroscopy in a crossed-beam configuration was applied to examine the nascent rovibrational state distributions and Doppler profiles of the reactive scattering products. The analyses of the product energy and population distributions demonstrated the existence of unusual dynamic characteristics and competition between the addition and abstraction reaction mechanisms at the molecular level. These features, which are in sharp contrast with those of the oxidation reactions of closed-shell hydrocarbon molecules, are discussed with the aid of ab initio and quantum statistical calculations.

Choi, Jong-Ho

365

Plasma thiobarbituric acid reactivity: reaction conditions and the role of iron, antioxidants and lipid peroxy radicals on the quantitation of plasma lipid peroxides  

Energy Technology Data Exchange (ETDEWEB)

The effects of Fe/sup 3 +/, lipid peroxy radicals and the antioxidant butylated hydroxytoluene on the 2-thiobarbituric (TBA) acid quantitation of plasma lipid peroxides were investigated. Whole plasma and plasma fractions prepared by trichloroacetic acid (TCA) protein precipitation and lipid extraction, demonstrated markedly differing TBA reactivities in the presence or absence of added Fe/sup 3 +/. Examination of the spectral profiles of the TBA reacted whole plasma and TCA precipitated fractions demonstrated the presence of interfering compounds which gave rise to an artifactual increase in lipid peroxide concentrations. In contrast the TBA reacted lipid extracts had low levels of interfering compounds that could be removed by our previously described high pressure liquid chromatographic method. Further characterization of the TBA reactivity of the lipid extract showed that Fe/sup 3 +/ at an optimal concentration of 0.5 mM was necessary for the quantitative decomposition of the lipid peroxides to the TBA reactive product malondialdehyde (MDA). However the presence of Fe/sup 3 +/ resulted in further peroxidation of any unsaturated lipids present.

Wade, C.R.; van Rij, A.M.

1988-01-01

366

ABT-199, a potent and selective BCL-2 inhibitor, achieves antitumor activity while sparing platelets.  

Science.gov (United States)

Proteins in the B cell CLL/lymphoma 2 (BCL-2) family are key regulators of the apoptotic process. This family comprises proapoptotic and prosurvival proteins, and shifting the balance toward the latter is an established mechanism whereby cancer cells evade apoptosis. The therapeutic potential of directly inhibiting prosurvival proteins was unveiled with the development of navitoclax, a selective inhibitor of both BCL-2 and BCL-2-like 1 (BCL-X(L)), which has shown clinical efficacy in some BCL-2-dependent hematological cancers. However, concomitant on-target thrombocytopenia caused by BCL-X(L) inhibition limits the efficacy achievable with this agent. Here we report the re-engineering of navitoclax to create a highly potent, orally bioavailable and BCL-2-selective inhibitor, ABT-199. This compound inhibits the growth of BCL-2-dependent tumors in vivo and spares human platelets. A single dose of ABT-199 in three patients with refractory chronic lymphocytic leukemia resulted in tumor lysis within 24 h. These data indicate that selective pharmacological inhibition of BCL-2 shows promise for the treatment of BCL-2-dependent hematological cancers. PMID:23291630

Souers, Andrew J; Leverson, Joel D; Boghaert, Erwin R; Ackler, Scott L; Catron, Nathaniel D; Chen, Jun; Dayton, Brian D; Ding, Hong; Enschede, Sari H; Fairbrother, Wayne J; Huang, David C S; Hymowitz, Sarah G; Jin, Sha; Khaw, Seong Lin; Kovar, Peter J; Lam, Lloyd T; Lee, Jackie; Maecker, Heather L; Marsh, Kennan C; Mason, Kylie D; Mitten, Michael J; Nimmer, Paul M; Oleksijew, Anatol; Park, Chang H; Park, Cheol-Min; Phillips, Darren C; Roberts, Andrew W; Sampath, Deepak; Seymour, John F; Smith, Morey L; Sullivan, Gerard M; Tahir, Stephen K; Tse, Chris; Wendt, Michael D; Xiao, Yu; Xue, John C; Zhang, Haichao; Humerickhouse, Rod A; Rosenberg, Saul H; Elmore, Steven W

2013-02-01

367

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2011-01-01

368

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

Science.gov (United States)

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

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

1997-01-01

369

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Nitrous acid (HONO) mixing ratios for the Houston metropolitan area were simulated with the Community Multiscale Air Quality (CMAQ) model for an episode during the Texas Air Quality Study (TexAQS) II in August/September 2006 and compared to in-situ MC/IC (mist-chamber/ion chromatograph) and long path DOAS (Differential Optical Absorption Spectroscopy) measurements at three different altitudes. Several HONO sources were accounted for in simulations, such as gas phase formation, direct emission...

Czader, B. H.; Rappenglu?ck, B.; Percell, P.; Byun, D. W.; Ngan, F.; Kim, S.

2012-01-01

370

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

International Nuclear Information System (INIS)

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

1976-06-11

371

ABT-869, a multitargeted receptor tyrosine kinase inhibitor: inhibition of FLT3 phosphorylation and signaling in acute myeloid leukemia  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In 15% to 30% of patients with acute myeloid leukemia (AML), aberrant proliferation is a consequence of a juxtamembrane mutation in the FLT3 gene (FMS-like tyrosine kinase 3–internal tandem duplication [FLT3-ITD]), causing constitutive kinase activity. ABT-869 (a multitargeted receptor tyrosine kinase inhibitor) inhibited the phosphorylation of FLT3, STAT5, and ERK, as well as Pim-1 expression in MV-4-11 and MOLM-13 cells (IC50 approximately 1-10 nM) harboring the FLT3-ITD. ABT-869 inhibite...

Shankar, Deepa B.; Li, Junling; Tapang, Paul; Owen Mccall, J.; Pease, Lori J.; Dai, Yujia; Wei, Ru-qi; Albert, Daniel H.; Bouska, Jennifer J.; Osterling, Donald J.; Guo, Jun; Marcotte, Patrick A.; Johnson, Eric F.; Soni, Niru; Hartandi, Kresna

2007-01-01

372

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

International Nuclear Information System (INIS)

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

2004-01-01