酶促乙酰化EGCG清除自由基及抗脂质过氧化活性研究

Free Radicals Scavenging and Inhibition of Lipid Peroxidation Activity of the Enzymatic Acetylated EGCG

摘要:

利用脂肪酶Lipozyme RM IM在乙腈反应体系中催化表没食子儿茶素没食子酸酯(EGCG)与乙酸乙烯酯进行乙酰化反应，得到EGCG乙酰化产物。通过液相色谱串联质谱(LC-MS/MS)和红外光谱对乙酰化产物进行了确证，其产物为不同取代度的混合物。反应前后红外图谱对照表明，酰化后EGCG主体结构与EGCG类似，但增加了明显的羰基、甲基吸收峰。通过测定乙酰化EGCG对超氧阴离子自由基（O2-?）、羟基自由基(?OH)、DPPH自由基的清除能力，研究其体外抗氧化活性，结果表明乙酰化EGCG对O2-?、?OH、DPPH?均具有较强的清除能力，半抑制率（IC50）分别为0.52 mg/mL、0.43 mg/mL和11.5 mg/L。体外抗脂质过氧化实验表明当乙酰化EGCG浓度为320 mg/L时，对H2O2诱导大鼠肝线粒体丙二醛（MDA）生成的抑制率为61.11%，对H2O2诱导大鼠红细胞氧化溶血的抑制率达93.54%。乙酰化EGCG具有良好的体外抗氧化活性，其浓度与抗氧化活性呈现一定的量效关系。

Abstract:

(-)-Epigallocatechin-3-O-gallate (EGCG) acetylated derivatives were prepared by enzymatic acylation with vinyl acetate and catalyzed by Lipozyme RM IM in acetonitrile. Liquid chromatography tandem mass spectrometry (LC-MS/MS) and infrared (IR) spectrometry were used to confirm the acylated EGCG product. It indicated that the product was a mixture of different degrees of substitutions. IR spectra showed that the acetylated EGCG derivatives had two strong absorption peaks of carbonyl and methyl, and the other parts were similar to EGCG. The antioxidant activity of acetylated EGCG in vitro was investigated by measuring scavenging effects of superoixide anion (O2-?), hydroxyl radical (?OH) and 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical. The acetylated EGCG was found to have good scavenging effects on O2-?, ?OH and DPPH? and the 50% inhibitory concentrations (IC50) were 0.52 mg/mL, 0.43 mg/mL and 11.5 mg/L, respectively. Anti-lipid peroxidation experiments showed that the inhibition rates of malonyldialdehyde (MDA) formation in rat liver mitochondria and hemolysis for rat red blood cells induced by H2O2 were 61.11% and 93.54% , respectively, when acetylated EGCG concentration was 320 mg/L. Therefore, acetylated EGCG had strong antioxidant activity in vitro, and their antioxidant activity is positively related to their concentration.