Efficient α-glucosylation of epigallocatechin gallate catalyzed by cyclodextrin glucanotransferase from Thermoanaerobacter sp.

The glycosylation of plant polyphenols may modulate their solubility and bioavailability and protect these molecules from oxygen, light degradation, and during gastrointestinal transit. In this work, the synthesis of various a-glucosyl derivatives of (-)-epigallocatechin gallate, the predominant catechin in green tea, was performed in water at 50 degrees C by a transglycosylation reaction catalyzed by cyclodextrin glycosyltransferase from Thermoanaerobacter sp. The molecular weight of reaction products was determined by high-performance liquid chromatography coupled to mass spectrometry. Using hydrolyzed potato starch as a glucosyl donor, two main monoglucosides were obtained with conversion yields of 58 and 13%, respectively. The products were isolated and chemically characterized by combining two-dimensional nuclear magnetic resonance methods. The major derivative was epigallocatechin gallate 3'-O-alpha-D-glucopyranoside (1), and the minor derivative was epigallocatechin gallate 7-O-alpha-D-glucopyranoside (2).