木犀草素与槲皮素抗氧化性能差异的电化学研究

黄酮醇的抗氧化活性通常显著强于与之对应的黄酮，而两者的分子结构仅在C环3-位上相差一个羟基。为了揭示黄酮醇3-OH增强抗氧化活性的反应机理，选取槲皮素和木犀草素，对两者的氧化过程进行循环伏安法和现场薄层长光程紫外可见光谱电化学测试。结果表明，两者在发生2e－/2H+反应氧化为对应的邻醌之后，只有槲皮素邻醌能够进一步转化为更稳定的单一共轭结构，带动失电子步骤的进行，从而增强了槲皮素的抗氧化活性。这个后行转化反应必须以3-位羟基的存在为前提。

Electrochemical Study on Difference in Antioxidant Ability between Luteolin and Quercetin

As one of flavonols with a 3-OH group in their chemical structures, quercetin (3,5,7,3',4'-pentahydroxyflavone) shows much stronger antioxidant activity than its corresponding flavone luteolin (5,7,3',4'-tetrahydroxyflavone) does. In the present study, cyclic voltammetry and in situ UV-Vis spectroelectrochemical method were used to investigate the electro-oxidation processes of both flavonoids for discovering the reaction mechanism by which 3-OH group promotes the antioxidant activity. The results indicateed that both compounds are oxidized to the corresponding o-quinones via 2e–/2H+ reactions, and only the quercetin o-quinone can be further isomerized to the more stable united conjugated structure in the presence of 3-OH group. This subsequent chemical transformation drives the loss process of electron and gives an additional contribution to the antioxidant activity of quercetin.