Byelyankacin: A novel melanogenesis inhibitor produced by Enterobacter sp. B20

A novel melanogenesis inhibitor, byelyankacin (1), was isolated from the fermentation broth of a bacterial strain. The producing organism, designated B20, was identified as a member of the genus Enterobacter based on taxonomic characteristics. 1 was obtained as a white powder from the culture medium by solvent extraction and serial chromatographic purification. The structure of 1 was determined as (E)-4-(2-isocyanovinyl)phenyl α-L-rhamnopyranoside on the basis of spectroscopic data. 1 potently inhibited mushroom tyrosinase and melanogenesis of B16-2D2 melanoma cells with IC₅₀ value of 2.1 nM and 30 nM, respectively.