Melanin biosynthesis inhibitory effects of calycosin-7-O-β-d-glucoside isolated from astragalus (Astragalus membranaceus)

To discover an active skin depigmentation agent, we isolated a melanin biosynthesis inhibitor from the methanol extract of astragalus (Astragalus membranaceus) using a bioactivity-guided fractionation and identified it as calycosin-7-O-β-d-glucoside via spectroscopic analysis. The active compound exhibited tyrosinase inhibitory activity with an IC50 value of 68 μM. In addition, calycosin-7-O-β-d-glucoside showed a melanin biosynthesis inhibition zone in a culture plate of Streptomyces bikiniensis. Furthermore, 75.78 μM of calycosin-7-O-β-d-glucoside dramatically decreased 50% of the melanin content on Melan-a cells without any apparent cytotoxicity. Theses results indicate that the calycosin-7-O-β-d-glucoside isolated from astragalus may be a good candidate for skin-whitening agent.