In this study, two quercetin-alpha-D-glucopyranosides were synthesized via the acceptor reaction of a glucansucrase obtained from Leuconostoc mesenteroides B-1299CB, with quercetin and sucrose. The two transfer products were purified via HPLC, and the structures of the products were identified as quercetin-4'-O-alpha-D-glucopyranoside (Q-G1) and quercetin-3'-O-alpha-D-glucopyranoside (Q-G1'), in accordance with the results of H-1, C-13, HSQC, H-H COSY, HMBC analyses. The primary product (Q-G1) evidenced slower effects on DPPH radical-scavenging activity (SC50 = 25.2 mu M) than was seen with quercetin (SC50 = 6.5 mu M). The water solubility of Q-G1 was 12.7 mM, whereas the quercetin was barely soluble in water. The K-i value of Q-G 1 (674.5 mu M) was almost identical to that of quercetin (673.3 mu M) with regard to tyrosinase inhibition effects. (c) 2006 Elsevier Inc. All rights reserved.