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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。
The acetylation of epigallocatechin gallate (EGCG) with vinyl acetate was catalyzed by lipase Lipozyme RM IM in acetonitrile reaction system to obtain acetylated EGCG. Acetylated products were confirmed by liquid chromatography-tandem mass spectrometry (LC-MS / MS) and infrared spectroscopy, and their products were mixtures of different degrees of substitution. Comparison of IR spectra before and after the reaction shows that the main structure of EGCG after acylation is similar to that of EGCG, but obvious carbonyl and methyl absorption peaks are increased. The anti-oxidative activities of EGCG in vitro were studied by measuring the ability of EGCG to scavenge superoxide anion (O2-), hydroxyl radical (· OH) and DPPH free radicals. The results showed that the acetylated EGCG had good activity on O2- ·, · OH and DPPH ·, respectively. The half-inhibitory rates (IC50) were 0.52 mg / mL, 0.43 mg / mL and 11.5 mg / L, respectively. In vitro anti-lipid peroxidation experiments showed that when the concentration of acetylated EGCG was 320 mg / L, the inhibitory rate of H2O2-induced malondialdehyde (MDA) production in liver mitochondria was 61.11%, and the inhibitory effect on H2O2-induced erythrocyte oxidation and hemolysis The inhibition rate reached 93.54%. Acetylated EGCG has good antioxidant activity in vitro, and its concentration and antioxidant activity showed a certain dose-effect relationship.