Optimization of lipase-catalyzed synthesis of acetylated EGCG by response surface methodology

(-)-Epigallocatechin-3-O-gallate (EGCG) acetylated derivatives, which can be widely used as a natural antioxidant in both lipid containing food and cosmetic applications, were prepared by lipase catalyzed acylation of EGCG with vinyl acetate. Response surface methodology (RSM) and 5-level-4-factor central composite rotatable design (CCRD) were employed to evaluate the effects of synthesis parameters, such as reaction time (6-10 h), temperature (30-50 degrees C), enzyme amount (1.5-2.5% (w/w) of substrate), and substrate molar ratio of EGCG to vinyl acetate (0.5-1.5) on conversion of EGCG. By using multiple regression analysis, the experimental data were fitted to a second order polynomial model. The most suitable combination of variables was 40 degrees C, 2.12%, 10 h and 1.13 for the reaction temperature, the enzyme amount, the reaction time, and EGCG/vinyl acetate mole ratio, respectively. At these optimal conditions, the conversion yield reached 87.37%. The presence of mono-, di- and tri-acetylated derivatives in acetylated EGCG was confirmed by LC-MS-MS and identified as 5 ''-O-acetyl-EGCG, 3 '', 5 ''-2-O-acetyl-EGCG and 5', 3 '', 5 ''-3-O-acetyl-EGCG by NMR. (C) 2013 Elsevier B.V. All rights reserved.