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首页> 外文期刊>Journal of Agricultural and Food Chemistry >Synergistic effects of thiols and amines on antiradical efficiency of protocatechuic Acid.
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Synergistic effects of thiols and amines on antiradical efficiency of protocatechuic Acid.

机译：硫醇和胺对原儿茶酸的抗自由基作用的协同作用。

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摘要

DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity of protocatechuic acid and its structural analogues (methyl protocatechuate, 3',4'-dihydroxyacetophenone, 3,4-dihydroxybenzaldehyde, and 3,4-dihydroxybenzonitrile) were examined in aprotic and protic solvents. In aprotic acetonitrile, all test compounds scavenged two radicals. In protic methanol, however, these compounds rapidly scavenged five radicals except for protocatechuic acid, which consumed only two radicals. The result indicated that higher radical scavenging activity in methanol than in acetonitrile was due to a nucleophilic addition of the methanol molecule on the oxidized quinones, which led to a regeneration of catechol structures. To investigate the importance of the nucleophilic addition on the quinones for the high radical scavenging activity, DPPH radical scavenging activity of protocatechuic acid and its analogues was examined in the presence of a variety of nucleophiles. The addition of a strong nucleophile such as a cysteine derivative significantly increased the radical scavenging equivalence. Furthermore, thiol adducts at C-2 and C-2,5 of protocatechuic acid and its analogues were isolated from the reaction mixtures. These results strongly suggest that the quinone of protocatechuic acid and its analogues undergo a nucleophilic attack at C-2 to yield 2-substituted-3,4-diols. Then, a regenerated catechol moiety of adducts scavenge two additional radicals by reoxidation into quinones, which undergo the second nucleophilic attack at the C-5. This mechanism demonstrates a possibility of synergistic effects of various nucleophiles on the radical scavenging ability of plant polyphenols containing a 3,4-dihydroxy substructure like protocatechuic acid and its analogues.
机译：考察了原儿茶酸及其结构类似物（原儿茶酸甲酯，3'，4'-二羟基苯乙酮，3,4-二羟基苯甲醛和3,4-二羟基苯甲腈）的DPPH（2,2-二苯基-1-吡啶基肼基）自由基清除活性。非质子和质子溶剂。在非质子乙腈中，所有测试化合物均清除了两个自由基。然而，在质子甲醇中，这些化合物迅速清除了五个自由基，除了原儿茶酸仅消耗两个自由基。结果表明，在甲醇中比在乙腈中更高的自由基清除活性是由于甲醇分子在氧化醌上的亲核加成，从而导致儿茶酚结构的再生。为了研究在醌上亲核加成对于高自由基清除活性的重要性，在多种亲核试剂存在下检查了原儿茶酸及其类似物的DPPH自由基清除活性。加入强亲核试剂（例如半胱氨酸衍生物）会显着增加自由基清除的当量。此外，从反应混合物中分离出原儿茶酸的C-2和C-2，5处的硫醇加合物。这些结果强烈表明原儿茶酸的醌及其类似物在C-2处经历亲核攻击，产生2-取代的3，4-二醇。然后，加合物的再生邻苯二酚部分通过再氧化成醌清除了两个额外的自由基，这些醌在C-5处经历了第二次亲核攻击。该机理证明了各种亲核试剂对含有3,4-二羟基亚结构的植物多酚如原儿茶酸及其类似物的自由基清除能力的协同作用的可能性。

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