Lipase catalyzed acetylation of EGCG, a lipid soluble antioxidant, and preparative purification by high-speed counter-current chromatography (HSCCC)

(−)-Epigallocatechin-3-O-gallate (EGCG) acetylated derivatives, which are widely used as natural antioxidants in both lipid containing food and cosmetic applications, were prepared by lipase catalyzed acylation of EGCG with vinyl acetate in this study. High-speed counter-current chromatography (HSCCC) combined with semi-preparative high performance liquid chromatography (HPLC) was used to separate and purify the acetylated derivatives of EGCG. A two-phase solvent system was optimized by the partition coefficient, K, which was composed of n-hexane-ethyl acetate-methanol-water at a volume ratio of 1.5:5:1.5:5 (v/v/v/v), and the lower phase of the system was used as the mobile phase at the flow rate of 5.0 mL/min. The separation temperature and revolution speed were 20 °C and 700 rpm, respectively. The three acetylated derivatives were identified as 5″-O-acetyl-EGCG, 3″,5″-di-O-acetyl-EGCG and 5′,3″,5″-tri-O-acetyl-EGCG by LC-MS/MS and NMR. The antioxidant activities of the three acetylated EGCG derivatives were superior to that of EGCG as determined by peroxide values (POV) in soybean oil. And 3″,5″-di-O-acetyl-EGCG exhibited the highest 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (IC50 of 0.08 mg/mL). Acetylated EGCGs may be used to control oxidation of oil-based foods.