Apigenin, a member of the flavone subclass of flavono-ids, has long been considered to have various biological activities. Its glucosides, in particular, have been reported to have higher water solubility, increased chemical stability, and enhanced biological activities. Here, the synthesis of apigenin glucosides by the in vitro glucosylation reaction was successfully performed using a UDP-glucosyltrans-ferase YjiC, from Bacillus licheniformis DSM 13. The glucosylation has been confirmed at the phenolic groups of C-4′ and C-7 positions ensuing apigenin 4′-O-glucoside, apigenin 7-O-glucoside and apigenin 4′,7-O-diglucoside as the products leaving the C-5 position unglucosylated. The position of glucosylation and the chemical structures of glucosides were elucidated by liquid chromatography/ mass spectroscopy and nuclear magnetic resonance spec- troscopy. The parameters such as pH, UDP glucose concentration and time of incubation were also analyzed during this study.

Keywords: apigenin, enzymatic synthesis, glucosides, UDP-glucosyltransferase, YjiC