Molecular mechanism of suppression of oxidative cell injury by Asteraceous caffeoylquinic acids

在日本，菊科蔬菜、牛蒡的根和加兰菊花的叶是常见的食用品。它们含有一系列咖啡酰奎宁酸（CQA）作为抗氧化成分。通过TBA和硫氰酸盐方法使用通过超声处理鸡蛋卵磷脂或从马血制备的红细胞血影制备的脂质体溶液测定CQA的抗氧化活性。脂质体对自由基引发剂诱导的过氧化反应的抑制作用顺序为DL-α-生育酚（Toc）>三咖啡酰奎宁酸（TCQA）>二咖啡酰奎宁酸（DCQA）>咖啡酸（CA）>绿原酸（=单咖啡酰奎宁酸，MCQA），而红细胞血影的抑制作用顺序为TCQA> DCQA>CA>MCQA>Toc。这些结果表明，CQA的抗氧化活性与分子中CA残基的数量成比例地增加。应该合理地假设CA残基的邻二酚结构是活性的原因。为了获得抗氧化活性和分子结构之间更详细的关系，接下来通过DPPH法测定CQA的自由基猝灭能力。一摩尔CA和MCQA淬灭三个DPPH自由基，这是一个半倍，比TOC更有效。正如预期的那样，DCQA和TCQA的活性再次与CA残基的数量成比例地发展。在DCQA同源物中，携带两个CA残基的分子显示出更强的活性。此外，额外的酰基取代基如琥珀酸酯的存在增强了活性。CA残基的邻近效应被解释为假设CA自由基的分子内偶联将再生一个活性酚基。

The Asteraceous vegetables, roots of burdock and leaves of garland chrysanthemum are commonly consumed in Japan. They contain a series of caffeoylquinic acids (CQAs) as the antioxidative principles. The antioxidative activity of the CQAs was determined by both TBA and thiocyanate methods using a liposome solution prepared by ultrasonication of egg lecithin or red blood cell ghosts prepared from horse blood. The inhibitory activity against the radical initiator-induced peroxidation of the liposome is in the order of DL-alpha-tocopherol (Toc) >tricaffeoylquinic acid (TCQA) >dicaffeoylquinic acids (DCQAs) >caffeic acid (CA) >chlorogenic acid (=monocaffeoylquinic acid, MCQA) , whereas that of the red blood cell ghosts is TCQA>DCQAs>CA>MCQA>Toc. These results indicate that the antioxidative activity of CQAs increases in proportion to the number of CA residues in the molecule. It should be reasonable to suppose that an ortho-diphenol structure of the CA residue is responsible for the activity. In order to obtain more detailed relationships between the antioxidative activity and the molecular structure, a radical quenching ability of the CQAs was next determined by a DPPH method. One molar of CA and MCQA quenched three DPPH radicals, which was one and half times more efficient than Toc. As expected, activity of DCQA and TCQA developed again in proportion to the number of CA residues. In the DCQA congeners, stronger activity was shown in the molecules carrying two CA residues close together. Moreover, the presence of additional acyl substituents such as succinate ester enhanced the activity. The neighboring effect of CA residues is interpreted by the assumption that the intramolecular coupling of CA radicals would regenerate an active phenolic group.