Lam Henry S, Proctor Andrew, Nyalala John, Morris Manford D, Smith W Grady
Department of Food Science, University of Arkansas, Fayetteville, Arkansas 72704, USA.
Lipids. 2005 Jun;40(6):569-74. doi: 10.1007/s11745-005-1417-x.
We investigated the changes in human LDL primary and secondary lipid oxidation products and modification of the apolipoprotein B-100 (apoB-100) secondary structures during Cu2+-mediated oxidation by FTIR spectroscopy in the presence of catechin, quercetin, and alpha-tocopherol at physiological concentrations. Catechin- and quercetin-containing samples had slower rates and longer lag phases for conjugated diene hydroperoxide (CD) formation than alpha-tocopherol-containing samples; however, all antioxidant-treated LDL samples generated similar CD levels (P< 0.05). A lower maximum (98.4 nmol/mg LDL protein) of carbonyl compounds was produced in the quercetin- and catechin-treated samples than in alpha-tocopherol samples. Modification of the apoB-100 secondary structures corresponded closely to the formation of carbonyls and was hampered by the presence of antioxidants. Physiological concentrations of catechin and quercetin offered similar levels of protection against modification by carbonyls of the apoB-100 at advanced stages (carbonyls approximately 96.0 nmol/mg LDL protein) but not at the intermediate stages (carbonyls approximately 58.0 nmol/mg LDL protein) of LDL oxidation probably owing to differences in the protein-binding mechanisms of catechin and quercetin. Relationships between peroxide formation, carbonyl products, and LDL protein denaturation were shown by the FTIR approach. The FTIR technique provided a simple new tool for a comprehensive evaluation of antioxidant performance in protecting LDL during in vitro oxidation.
我们通过傅里叶变换红外光谱法，在生理浓度的儿茶素、槲皮素和α-生育酚存在的情况下，研究了铜离子介导的氧化过程中人类低密度脂蛋白（LDL）一级和二级脂质氧化产物的变化以及载脂蛋白B-100（apoB-100）二级结构的修饰情况。与含α-生育酚的样品相比，含儿茶素和槲皮素的样品中共轭二烯氢过氧化物（CD）形成的速率较慢且滞后阶段较长；然而，所有抗氧化剂处理的LDL样品产生的CD水平相似（P<0.05）。槲皮素和儿茶素处理的样品中羰基化合物的最大生成量（98.4 nmol/mg LDL蛋白）低于α-生育酚样品。apoB-100二级结构的修饰与羰基的形成密切相关，并受到抗氧化剂的阻碍。生理浓度的儿茶素和槲皮素在LDL氧化的晚期（羰基约为96.0 nmol/mg LDL蛋白）对apoB-100羰基修饰提供了相似水平的保护，但在LDL氧化的中期（羰基约为58.0 nmol/mg LDL蛋白）则不然，这可能是由于儿茶素和槲皮素与蛋白质结合机制的差异。傅里叶变换红外光谱法显示了过氧化物形成、羰基产物和LDL蛋白质变性之间的关系。傅里叶变换红外光谱技术为在体外氧化过程中全面评估抗氧化剂对LDL的保护性能提供了一种简单的新工具。
