Antioxidant evaluation of O-methylated metabolites of catechin, epicatechin and quercetin
Antioxidant evaluation of O-methylated metabolites of catechin, epicatechin and quercetin
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DOI：
10.1016/j.jpba.2009.04.007
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发表时间：
2010-01-20
影响因子：
3.4
通讯作者：
Santos-Buelga, Celestino
中科院分区：
文献类型：
--
作者：
Duenas, Montserrat;Gonzalez-Manzano, Susana;Santos-Buelga, Celestino
儿茶素和槲皮素是许多植物性食品中的主要多酚，与促进健康有关。在人体有机体中，它们主要代谢为不同的代谢物，这些代谢物进一步在血浆中发现，并有助于与母体化合物的摄入相关的生物效应。槲皮素和儿茶素代谢的一个重要步骤是儿茶酚基团的 O-甲基化，预计这会对其抗氧化和清除特性产生影响。在目前的工作中，已经制备并表征了儿茶素和表儿茶素的3'-和4'-甲基醚，并评估了它们的抗氧化活性，并与相应的槲皮素衍生物进行了比较。使用三价铁还原力（FRAP）测定和两种基于在不同pH值下清除ABTS（中心点+）自由基阳离子的能力的方法来评估抗氧化活性。在这些测定中，三种黄酮类化合物比通常公认的抗氧化剂（如α-生育酚）表现出更好的自由基清除剂和还原性化合物。儿茶酚 B 环羟基的 O-甲基化导致母体化合物的抗氧化活性降低。然而，甲基化代谢物在 pH 7.4 时仍保留显着的自由基清除活性，表明它们可以在生理条件下充当潜在的抗氧化剂。一般来说，槲皮素及其甲基化代谢物表现出比表儿茶素及其 O-甲基衍生物更高的活性，尽管在 pH 7.4 下 3'-O-甲基儿茶素具有相对较高的抗氧化活性，与其母体化合物和槲皮素代谢物相当。经证实，所检测的黄酮类化合物的抗氧化活性强烈依赖于培养基的pH值，在较高的pH值下显示出较高的活性。所获得的结果预计将有助于理解因摄入富含类黄酮的饮食而产生的生物效应所涉及的机制。 (C) 2009 Elsevier B.V. 保留所有权利。
Catechins and quercetin are major polyphenols in many plant foods that have been related to health promotion. In the human organism they are largely metabolized to different metabolites, which are further found in plasma and should contribute to the biological effects associated to the intake of the parent compounds. An important step in quercetin and catechins metabolism is the O-methylation of the catechol group, which can be expected to have an effect on their antioxidant and scavenging properties. In the present work, the 3'- and 4'-methylethers of catechin and epicatechin have been prepared and characterised and their antioxidant activity evaluated and compared to that of the corresponding quercetin derivatives. The antioxidant activity was assessed using the ferric reducing power (FRAP) assay and two methods based on the ability to scavenge the ABTS(center dot+) radical cation at different pH values. In these assays the three flavonoids behave as better radical scavengers and reducing compounds than usually recognised antioxidants like alpha-tocopherol. The O-methylation of the hydroxyls of the catechol B-ring resulted in a decrease of the antioxidant activity with regard to the parent compounds. However, the methylated metabolites still retain significant radical scavenging activity at pH 7.4, suggesting that they could act as potential antioxidants ill physiological conditions. Quercetin and its methylated metabolites showed, in general, greater activity than (epi)catechin and their O-methyl derivatives, although a relatively high antioxidant activity was found in the case of 3'-O-methyl catechin at pH 7.4, comparable to those of its parent compound and the quercetin metabolites. It was confirmed that the antioxidant activity of the flavonoids assayed was strongly dependent on the pH of the medium, showing higher activity at greater pH values. The results obtained are expected to contribute to the understanding of the mechanisms involved in the biological effects attributed to the intake of flavonoid-rich diets. (C) 2009 Elsevier B.V. All rights reserved.