Arora A, Nair M G, Strasburg G M
Department of Food Science and Human Nutrition, National Food Safety and Toxicology Center, Michigan State University, East Lansing 48824, USA.
Free Radic Biol Med. 1998 Jun;24(9):1355-63. doi: 10.1016/s0891-5849(97)00458-9.
Structurally diverse plant phenolics were examined for their abilities to inhibit lipid peroxidation induced either by Fe(II) and Fe(III) metal ions or by azo-derived peroxyl radicals in a liposomal membrane system. The antioxidant abilities of flavonoids were compared with those of coumarin and tert-butylhydroquinone (TBHQ). The antioxidant efficacies of these compounds were evaluated on the basis of their abilities to inhibit the fluorescence intensity decay of an extrinsic probe, 3-(p-(6-phenyl)-I,3,5-hexatrienyl)phenylpropionic acid (DPH-PA), caused by the free radicals generated during lipid peroxidation. All the flavonoids tested exhibited higher antioxidant efficacies against metal-ion-induced peroxidations than peroxyl-radical-induced peroxidation, suggesting that metal chelation may play a larger role in determining the antioxidant activities of these compounds than has previously been believed. Distinct structure-activity relationships were also revealed for the antioxidant abilities of the flavonoids. Presence of hydroxyl substituents on the flavonoid nucleus enhanced activity, whereas substitution by methoxy groups diminished antioxidant activity. Substitution patterns on the B-ring especially affected antioxidant potencies of the flavonoids. In cases where the B-ring could not contribute to the antioxidant activities of flavonoids, hydroxyl substituents in an catechol structure on the A-ring were able to compensate and become a larger determinant of flavonoid antioxidant activity.
在脂质体膜系统中，研究了结构多样的植物酚类物质抑制由亚铁离子和铁离子或偶氮衍生的过氧自由基诱导的脂质过氧化的能力。将黄酮类化合物的抗氧化能力与香豆素和叔丁基对苯二酚（TBHQ）的抗氧化能力进行了比较。根据这些化合物抑制脂质过氧化过程中产生的自由基引起的外在探针3-（对-（6-苯基）-1,3,5-己三烯基）苯基丙酸（DPH-PA）荧光强度衰减的能力，评估了它们的抗氧化效果。所有测试的黄酮类化合物对金属离子诱导的过氧化的抗氧化效果均高于过氧自由基诱导的过氧化，这表明金属螯合在决定这些化合物的抗氧化活性方面可能比以前认为的发挥更大的作用。还揭示了黄酮类化合物抗氧化能力的明显构效关系。黄酮核上羟基取代基的存在增强了活性，而甲氧基取代则降低了抗氧化活性。B环上的取代模式尤其影响黄酮类化合物的抗氧化效力。在B环对黄酮类化合物的抗氧化活性没有贡献的情况下，A环上邻苯二酚结构中的羟基取代基能够起到补偿作用，并成为黄酮类化合物抗氧化活性的更大决定因素。
