Syntheses of Arbutin-α-glycosides and a Comparison of Their Inhibitory Effects with Those of α-Arbutin and Arbutin on Human Tyrosinase

Abstract

The effects of 4-hydroxyphenyl α-glucopyranoside (α-arbutin) and 4-hydroxyphenyl β-glucopyranoside (arbutin) on the activity of tyrosinase from human malignant melanoma cells were examined. The inhibitory effect of α-arbutin on human tyrosinase was stronger than that of arbutin. The K_i value for α-arbutin was calculated to be 1/20 that for arbutin. We then synthesized arbutin-α-glycosides by the transglycosylation reaction of cyclomaltodextrin glucanotransferase using arbutin and starch, respectively, as acceptor and donor molecules. The structural analyses using ¹³C- and ¹H-NMR proved that the transglycosylated products were 4-hydroxyphenyl β-maltoside (β-Ab-α-G1) and 4-hydroxyphenyl β-maltotrioside (β-Ab-α-G2). These arbutin-α-glycosides exhibited competitive type inhibition on human tyrosinase, and their K_i values were calculated to be 0.7 mM and 0.9 mM, respectively. These arbutin-α-glycosides posessed stronger inhibitory activity than arbutin, but less activity than α-arbutin. These results suggested that the α-glucosidic linkage of hydroquinone-glycosides plays an important role in the inhibitory effect on human tyrosinase.