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

在日本，星形蔬菜、牛蒡的根和菊花的叶子是人们常吃的食物。它们含有一系列咖啡酰奎宁酸（CQAs）作为抗氧化原理。CQAs的抗氧化活性采用TBA和硫氰酸盐两种方法测定，采用超声法制备卵磷脂脂质体或马血红细胞鬼液。对自由基引发剂诱导的脂体过氧化的抑制活性依次为dl - α -生育酚(Toc) >三咖啡酰基奎宁酸(TCQA) >二咖啡酰基奎宁酸(dcqa) >咖啡酸(CA) >绿原酸（=单咖啡酰基奎宁酸，MCQA），而红细胞鬼的抑制活性依次为TCQA>DCQAs>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。可以合理地认为，CA残留物的邻二酚结构是其活性的原因。为了获得更详细的抗氧化活性与分子结构之间的关系，接下来用DPPH法测定了cqa的自由基猝灭能力。1摩尔CA和MCQA淬灭3个DPPH自由基的效率是Toc的1.5倍。正如预期的那样，DCQA和TCQA的活性再次与CA残基数成比例地发展。在DCQA同系物中，携带两个靠近的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残基的邻近效应可以通过CA自由基的分子内偶联来解释。

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.