Enzymatic Synthesis of Resveratrol alpha-Glucoside by Amylosucrase of Deinococcus geothermalis

Glycosylation of resveratrol was carried out by using the amylosucrase of Deinococcus geothermalis, and the glycosylated products were tested for their solubility, chemical stability, and biological activities. We synthesized and identified these two major glycosylated products as resveratrol-4'-O-alpha-glucoside and resveratrol-3-O-alpha-glucoside by nuclear magnetic resonance analysis with a ratio of 5:1. The water solubilities of the two resveratrol-alpha-glucoside isomers (alpha-piceid isomers) were approximately 3.6 and 13.5 times higher than that of beta-piceid and resveratrol, respectively, and they were also highly stable in buffered solutions. The antioxidant activity of the alpha-piceid isomers, examined by radical scavenging capability, showed it to be initially lower than that of resveratrol, but as time passed, the alpha-piceid isomers' activity reached a level similar to that of resveratrol. The alpha-piceid isomers also showed better inhibitory activity against tyrosinase and melanin synthesis in B16F10 melanoma cells than beta-piceid. The cellular uptake of the alpha-piceid isomers, which was assessed by ultra-performance liquid chromatography (UPLC) analysis of the cell-free extracts of B16F10 melanoma cells, demonstrated that the glycosylated form of resveratrol was gradually converted to resveratrol inside the cells. These results indicate that the enzymatic glycosylation of resveratrol could be a useful method for enhancing the bioavailability of resveratrol.