Zhu Qin Yan, Schramm Derek D, Gross Heidrun B, Holt Roberta R, Kim Sun H, Yamaguchi Tomoko, Kwik-Uribe Catherine L, Keen Carl L
Department of Nutrition, University of California, Davis, CA 95616-8669, USA.
Clin Dev Immunol. 2005 Mar;12(1):27-34. doi: 10.1080/17402520512331329514.
Cocoa can be a rich source of antioxidants including the flavan-3-ols, epicatechin and catechin, and their oligomers (procyanidins). While these flavonoids have been reported to reduce the rate of free radical-induced erythrocyte hemolysis in experimental animal models, little is known about their effect on human erythrocyte hemolysis. The major objective of this work was to study the effect of a flavonoid-rich cocoa beverage on the resistance of human erythrocytes to oxidative stress. A second objective was to assess the effects of select purified cocoa flavonoids, epicatechin, catechin, the procyanidin Dimer B2 and one of its major metabolites, 3'-O-methyl epicatechin, on free radical-induced erythrocyte hemolysis in vitro. Peripheral blood was obtained from 8 healthy subjects before and 1, 2, 4 and 8h after consuming a flavonoid-rich cocoa beverage that provided 0.25g/kg body weight (BW), 0.375 or 0.50g/kg BW of cocoa. Plasma flavanol and dimer concentrations were determined for each subject. Erythrocyte hemolysis was evaluated using a controlled peroxidation reaction. Epicatechin, catechin, 3'-O-methyl epicatechin and (-)-epicatechin-(4beta > 8)-epicatechin (Dimer B2) were detected in the plasma within 1 h after the consumption of the beverage. The susceptibility of erythrocytes to hemolysis was reduced significantly following the consumption of the beverages. The duration of the lag time, which reflects the capacity of cells to buffer free radicals, was increased. Consistent with the above, the purified flavonoids, epicatechin, catechin, Dimer B2 and the metabolite 3'-O-methyl epicatechin, exhibited dose-dependent protection against AAPH-induced erythrocyte hemolysis at concentrations ranging from 2.5 to 20 microM. Erythrocytes from subjects consuming flavonoid-rich cocoa show reduced susceptibility to free radical-induced hemolysis (p < 0.05).
可可富含抗氧化剂，包括黄烷-3-醇、表儿茶素和儿茶素及其低聚物（原花青素）。虽然在实验动物模型中，这些类黄酮已被报道可降低自由基诱导的红细胞溶血率，但它们对人类红细胞溶血的影响却鲜为人知。这项工作的主要目的是研究富含类黄酮的可可饮料对人类红细胞抗氧化应激能力的影响。第二个目的是评估选定的纯化可可类黄酮、表儿茶素、儿茶素、原花青素二聚体B2及其主要代谢产物之一3'-O-甲基表儿茶素对体外自由基诱导的红细胞溶血的影响。在8名健康受试者饮用提供0.25g/kg体重（BW）、0.375或0.50g/kg BW可可的富含类黄酮的可可饮料之前以及饮用后1、2、4和8小时采集外周血。测定每个受试者的血浆黄烷醇和二聚体浓度。使用可控过氧化反应评估红细胞溶血情况。饮用饮料后1小时内，在血浆中检测到表儿茶素、儿茶素、3'-O-甲基表儿茶素和（-）-表儿茶素-（4β>8）-表儿茶素（二聚体B2）。饮用饮料后，红细胞溶血的易感性显著降低。反映细胞缓冲自由基能力的延迟时间延长。与此一致的是，纯化的类黄酮、表儿茶素、儿茶素、二聚体B2和代谢产物3'-O-甲基表儿茶素在2.5至20 microM的浓度范围内对AAPH诱导的红细胞溶血表现出剂量依赖性保护作用。饮用富含类黄酮可可的受试者的红细胞对自由基诱导的溶血敏感性降低（p<0.05）。
