β-乳球蛋白与邻苯醌类物质反应效率分析

Efficiency of Reaction betweenβ-Lactoglobulin and o-Benzoquinones

乳清蛋白作为营养健康食品的重要原料或成分,可能与多酚氧化形成的邻苯醌类物质反应,即发生蛋白-多酚共价相互作用。乳清蛋白与邻苯醌类物质的反应效率是阐明两者反应行为的重要科学依据。以乳清蛋白主要成分β-乳球蛋白(β-Lactoglobulin,β-LG)作为研究对象,利用循环伏安技术研究了不同条件下β-LG与邻苯醌类物质的反应效率。结果表明:在pH值7.0,扫描速率50mV/s条件下,β-LG(0.03mmol/L)与非黄酮型邻苯醌的反应效率顺序为:原儿茶酸(54.72%)>咖啡酸(47.01%)>迷迭香酸(41.86%)>绿原酸(39.29%)>邻苯二酚(27.36%)>4-甲基邻苯二酚(22.51%)>原儿茶酸乙酯(19.24%),与黄酮型邻苯醌的反应效率的顺序为:木犀草素(19.34%)>槲皮素(14.68%)>芦丁(12.50%)≈儿茶素(11.97%)>表儿茶素(6.66%)。研究表明:邻苯醌类物质的结构会影响其与β-LG的反应效率,醌环上含有给电子基团的邻苯醌类物质反应效率高于醌环上含有吸电子基团的邻苯醌类物质;此外,醌环上取代基的空间位阻会削弱邻苯醌类物质与β-LG的反应效率。

As an important raw material and component of nutritious and healthy food,interactions between whey proteins and o-benzoquinone,a result of polyphenol oxidation,are thought likely to affect the structure and function of the proteins.The reaction efficiency between whey proteins with o-benzoquinones is a useful scientific basis upon which the reaction behavior can be elucidated;thus,the reactions betweenβ-lactoglobulin(β-LG),the main component of whey proteins,and different o-benzoquinones were investigated by cyclic voltammetry under different conditions.The reaction betweenβ-LG(0.03 mmol/L)and non-flavonoid o-benzoquinones was thus examined under conditions of pH value 7.0 and a scan rate of 50 mV/s,resulting in the following efficiencies,in descending order:protocatechuic acid(54.72%)>caffeic acid(47.01%)>rosmarinic acid(41.86%)>chlorogenic acid(39.29%)>catechol(27.36%)>4-methylcatechol(22.51%)>protocatechuic acid ethyl ester(19.24%),while reaction efficiencies of:luteolin(19.34%)>quercetin(14.68%)>rutin(12.50%)≈(+)-catechin(11.97%)>(-)-epicatechin(6.66%)were obtained for flavonoid o-benzoquinones(0.60 mmol/L),in descending order.These results prove that o-benzoquinone structure affects the efficiency of the reaction withβ-LG,with the reactivity of o-benzoquinones andβ-LG weakened by electron-donating groups and strengthened by the electron-withdrawing groups on the o-benzoquinone rings.The steric hindrance of the o-benzoquinone ring substituents also reduces the reactivity.