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首页> 外文期刊>Journal of Agricultural and Food Chemistry >Effects of Structure on Radical-Scavenging Abilities and Antioxidative Activities of Tea Polyphenols:NMR Analytical Approach Using 1,1-Diphenyl-2-picrylhydrazyl Radicals
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Effects of Structure on Radical-Scavenging Abilities and Antioxidative Activities of Tea Polyphenols:NMR Analytical Approach Using 1,1-Diphenyl-2-picrylhydrazyl Radicals

机译：结构对茶多酚自由基清除能力和抗氧化活性的影响：使用1，1-二苯基-2-甲基-2-肼基自由基的NMR分析方法

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摘要

Tea(Camellia sinensis)leaves contain various antioxidants such as ascorbic acid(1)and polyphenols.This study tries to clarify the molecular mechanisms underlying the antioxidative and radical-scavenging activities of these antioxidants,and the reactivities of each antioxidant have been compared against that of the stable free radical 1,1-diphenyl-2-picrylhydrazyl(DPPH,2)using nuclear magnetic resonance(NMR)analysis.Catechol(3)and(+)-taxifolin(4)were oxidized to omicron-quinone by 2.However,ethyl protocatechuate(5)and quercetin(6)were not oxidized to omicron-quinone,even though they possess a catechol structure.The radical-scavenging ability of omicron-dihydroxyl phenolic compounds with a conjugated olefinic double bond(e.g.,6)was superior to that of compounds without this bond(e.g.,4),whereas the ability of omicron-dihydroxyl phenolic compounds possessing a conjugated carbonyl bond(5)was inferior to that of compounds lacking this bond(3).Vicinal trihydroxyl phenolic compounds with a conjugated olefinic double bond [e.g.,myricetin(7)] had an inferior scavenging ability as compared with compounds lacking this bond [e.g.,pyrogallol(8)],but 7 was a better scavenger than compounds with a conjugated carbonyl double bond [e.g.,ethyl gallate(9)].In addition,vicinal trihydroxyl phenolic compounds(e.g.,9)were superior to omicron-dihydroxyl phenolic compounds(e.g.,6).Finally,1 scavenged radicals more quickly than 8.
机译：茶树茶中含有多种抗氧化剂，如抗坏血酸（1）和多酚。本研究试图阐明这些抗氧化剂的抗氧化和清除自由基活性的分子机制，并将每种抗氧化剂的反应性与该抗氧化剂进行了比较。核磁共振（NMR）分析法测定稳定的自由基1,1-二苯基-2-甲基苯并肼基（DPPH，2）。儿茶酚（3）和（+）-紫杉醇（4）被2氧化为邻苯二酚醌。然而，原儿茶酸乙酯（5）和槲皮素（6）即使具有邻苯二酚结构也不会被氧化成微米醌。具有共轭烯烃双键（例如6）的微米二羟基酚化合物的自由基清除能力。优于不具有该键的化合物（例如，4），而具有共轭羰基键（5）的微米二羟基酚化合物的能力要比不具有该键的化合物（3）的能力差。一个公司与没有该键的化合物[例如，邻苯三酚（8）]相比，缀合的烯烃双键[例如，杨梅素（7）]的清除能力较差，但与具有共轭羰基双键的化合物[7]相比，清除剂的清除能力更好。没食子酸乙酯（9）]。此外，邻位三羟基酚类化合物（例如9）优于微米二羟基酚类化合物（例如6）。最后，1清除自由基的速度比8快。

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