Efficient enzymatic modification of epigallocatechin gallate in ionic liquids

摘要

Epigallocatechin gallate (EGCG), the main polyphenolic substance in tea, exhibits well-known biological benefits. In order to improve fat solubility and bioavailability, a novel path for the lipase enzymatic transesterification synthesis of acylated EGCG derivatives in an ionic liquid solvent was established. The optimal reaction parameters were determined and a maximum conversion of the transesterification reaction was achieved at 98.65%. [Bmim][BF 4 ] was the best reaction medium and the immobilized lipase Novozym 435 was the best catalyst. The enzyme was added to a final concentration of 2% (w/w, EGCG), and the reaction was performed at an optimum temperature of 70°C stirring for 10?h at 250?rpm. The most suitable acyl donor, vinyl acetate, and EGCG were mixed at a molar ratio of 90:1 for the reaction. The structure of the purified acetylated EGCG was determined to be 5″- O -acetyl-EGCG and 3″, 5″-2- O -acetyl-EGCG by mass spectrometry, NMR, and infrared analyses.