Epigallocatechin-3-gallate (EGCG), an antioxidant present in green tea, could play an important role in the prevention of cancer. However, its bioavailability is low due to its instability in gastrointestinal environment. β-Lactoglobulin (β-Lg), the major protein in whey, is known for its capacity to bind bioactive molecules and could protect them from oxidation. Interaction between β-Lg and EGCG was investigated at pH 7.0 and 4.0 using fluorescence and Fourier transform infrared spectroscopy, and its impact on EGCG antioxidant activity was determined using the ferric-reducing antioxidant power method. EGCG bound to native or heat-denatured β-Lg by hydrogen bonding and possibly hydrophobic interaction at pH 7.0 and 4.0. The affinity of EGCG for heat-denatured β-Lg at pH 7.0 was greater than for native β-Lg and greater than its affinity for the protein in either state at pH 4.0. Complexing with β-Lg decreased the antioxidant activity of EGCG under all conditions investigated. However, the protein provided limited protection of EGCG against degradation over time, the heat-denatured form being slightly more effective at pH 7.0. This study provides insight into the characteristics of β-Lg binding with a flavonoid and its impact on the antioxidant activity of flavonoids in food systems.

摘要 表没食子儿茶素没食子酸酯(EGCG)是绿茶中类黄酮类多酚物质。它具有抗氧化活性,可预防和延缓癌症的发生。然而,由于不稳定性,EGCG的生物利用度比较低。β-乳球蛋白(β-LG)是牛奶中的主要乳清蛋白,可结合生物活性分子,并降低它们的氧化降解。本研究采用荧光光谱法和傅里叶变换红外光谱法研究β-LG和EGCG的相互作用,并通过铁离子还原/抗氧化能力(FRAP)法表征了β-LG对EGCG抗氧化活性的影响。当溶液pH在7.0和4.0时,EGCG与天然和热变性的β-Lg反应生成复合物。氢键是两者结合的驱动力。此外,疏水作用也可能发生在茶多酚和蛋白质间。当pH为7.0时,EGCG与热变性蛋白质间的结合力高于天然态蛋白质,也高于它与两种蛋白质在pH4.0时的结合作用。虽然β- Lg-EGCG复合物的形成降低EGCG的抗氧化活性,但是β-LG在某种程度上可以延缓EGCG的降解。β-LG的延缓作用在热变性态和中性pH时是稍更有效的。这些研究结果为β-LG与类黄酮化合物的结合作用以及其对食品体系中类黄酮的抗氧化性的影响提供了理论基础和实验数据。