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      Evaluation of Antioxidant and Free Radical Scavenging Capacities of Polyphenolics from Pods of Caesalpinia pulcherrima

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          Abstract

          Thirteen polyphenolics were isolated from fresh pods of Caesalpinia pulcherrima using various methods of column chromatography. The structures of these polyphenolics were elucidated as gallic acid ( 1), methyl gallate ( 2), 6- O-galloyl- d-glucoside ( 3), methyl 6- O-galloyl-β- d-glucoside ( 4), methyl 3,6-di- O-galloyl-α- d-glucopyranoside ( 5), gentisic acid 5- O-α- d-(6′- O-galloyl)glucopyranoside ( 6), guaiacylglycerol 4- O-β- d-(6′- O-galloyl)glucopyranoside ( 7), 3-methoxy-4-hydroxyphenol 1- O-β- d-(6′- O-galloyl) glucopyranoside ( 8), (+)-gallocatechin ( 9), (+)-catechin ( 10), (+)-gallocatechin 3- O-gallate ( 11), myricetin 3-rhamnoside ( 12), and ampelopsin ( 13). All isolated compounds were tested for their antioxidant activities in the 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl, and peroxynitrite radicals scavenging assays. Among those compounds, 11, 12, and 2 exhibited the best DPPH-, hydroxyl-, and peroxynitrite radical-scavenging activities, respectively. Compound 7 is a new compound, and possesses better scavenging activities towards DPPH but has equivalent hydroxyl radical scavenging activity when compared to BHT. The paper is the first report on free radical scavenging properties of components of the fresh pods of Caesalpinia pulcherrima. The results obtained from the current study indicate that the free radical scavenging property of fresh pods of Caesalpinia pulcherrima may be one of the mechanisms by which this herbal medicine is effective in several free radical mediated diseases.

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          The deoxyribose method: a simple "test-tube" assay for determination of rate constants for reactions of hydroxyl radicals.

          Hydroxyl radicals, generated by reaction of an iron-EDTA complex with H2O2 in the presence of ascorbic acid, attack deoxyribose to form products that, upon heating with thiobarbituric acid at low pH, yield a pink chromogen. Added hydroxyl radical "scavengers" compete with deoxyribose for the hydroxyl radicals produced and diminish chromogen formation. A rate constant for reaction of the scavenger with hydroxyl radical can be deduced from the inhibition of color formation. For a wide range of compounds, rate constants obtained in this way are similar to those determined by pulse radiolysis. It is suggested that the deoxyribose assay is a simple and cheap alternative to pulse radiolysis for determination of rate constants for reaction of most biological molecules with hydroxyl radicals. Rate constants for reactions of ATP, ADP, and Good's buffers with hydroxyl radicals have been determined by this method.
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            Apparent hydroxyl radical production by peroxynitrite: implications for endothelial injury from nitric oxide and superoxide.

            Superoxide dismutase reduces injury in many disease processes, implicating superoxide anion radical (O2-.) as a toxic species in vivo. A critical target of superoxide may be nitric oxide (NO.) produced by endothelium, macrophages, neutrophils, and brain synaptosomes. Superoxide and NO. are known to rapidly react to form the stable peroxynitrite anion (ONOO-). We have shown that peroxynitrite has a pKa of 7.49 +/- 0.06 at 37 degrees C and rapidly decomposes once protonated with a half-life of 1.9 sec at pH 7.4. Peroxynitrite decomposition generates a strong oxidant with reactivity similar to hydroxyl radical, as assessed by the oxidation of deoxyribose or dimethyl sulfoxide. Product yields indicative of hydroxyl radical were 5.1 +/- 0.1% and 24.3 +/- 1.0%, respectively, of added peroxynitrite. Product formation was not affected by the metal chelator diethyltriaminepentaacetic acid, suggesting that iron was not required to catalyze oxidation. In contrast, desferrioxamine was a potent, competitive inhibitor of peroxynitrite-initiated oxidation because of a direct reaction between desferrioxamine and peroxynitrite rather than by iron chelation. We propose that superoxide dismutase may protect vascular tissue stimulated to produce superoxide and NO. under pathological conditions by preventing the formation of peroxynitrite.
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              Study on the inhibitory effect of tannins and flavonoids against the 1,1-diphenyl-2 picrylhydrazyl radical.

              Fifty-one tannins and forty-one flavonoids isolated from Oriental medicinal herbs were evaluated for their antioxidant ability with a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-generating system. The results showed that tannins and certain flavonoids are potential free-radical scavengers, and that their activity against the DPPH radical is closely associated with their chemical structure. A comparison of the two classes of compounds showed that tannins have more potential than flavonoids because almost all the tannins demonstrated significant scavenging action within a low concentration range, whereas the activity of flavonoids varied distinctively among the different compounds. An increase of galloyl groups, molecular weight, and ortho-hydroxyl structure enhanced the activity of tannins, whereas the number and position of hydroxyl groups were important features for the scavenging of free radicals by flavonoids. Moreover, it appeared that when the free hydroxyl group was methoxylated or glycosylated, the inhibitory activity was obviously decreased or even abolished.
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                Author and article information

                Journal
                Int J Mol Sci
                Int J Mol Sci
                ijms
                International Journal of Molecular Sciences
                Molecular Diversity Preservation International (MDPI)
                1422-0067
                2012
                18 May 2012
                : 13
                : 5
                : 6073-6088
                Affiliations
                [1 ]Graduate Institute of Pharmacognosy, School of Pharmacy, Taipei Medical University, 250 Wuxing St., Taipei 11031, Taiwan; E-Mails: hsu0320@ 123456tmu.edu.tw (F.-L.H.); wjhuang@ 123456tmu.edu.tw (W.-J.H.); lmh@ 123456tmu.edu.tw (M.-H.L.); m303090001@ 123456tmu.edu.tw (H.-J.L.); wchou@ 123456tmu.edu.tw (W.-C.H.)
                [2 ]Department of Pharmacy, Taipei Medical University Hospital, 250 Wuxing St., Taipei 11031, Taiwan
                [3 ]School of Pharmacy, College of Pharmacy, Taipei Medical University, 250 Wuxing St., Taipei 11031, Taiwan; E-Mails: thwu@ 123456tmu.edu.tw (T.-H.W.); lcchen@ 123456health.gov.tw (L.-C.C.)
                [4 ]Department of Pharmacy, Taipei City Hospital, No.145, Zhengzhou Rd., Taipei 10341, Taiwan
                Author notes
                [* ]Author to whom correspondence should be addressed; E-Mail: mhl00001@ 123456tmu.edu.tw ; Tel.: +886-2-7361661 (ext 6138); Fax: +886-2-2231-1412.
                Article
                ijms-13-06073
                10.3390/ijms13056073
                3382783
                22754350
                4a29a478-df21-461b-af56-4031c425157e
                © 2012 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland.

                This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution license ( http://creativecommons.org/licenses/by/3.0/).

                History
                : 27 February 2012
                : 09 May 2012
                : 10 May 2012
                Categories
                Article

                Molecular biology
                1,1-diphenyl-2-picrylhydrazyl (dpph) radical,butylated hydroxytoluene (bht),peroxynitrite,dihydrorhodamine 123 (dhr 123),hydroxyl radical

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