Natural tyrosinase inhibitors from Betula platyphylla barks

Abstract

During the process of searching for tyrosinase inhibitors from natural medicines, one new monoterpene rhamnoside (1) and 13 known compounds (2–14) were isolated from the ethanolic extract of Betula platyphylla barks by repeated column chromatography. These structures were identified by comprehensive spectroscopic data analysis such as high-resolution electrospray ionization mass spectra (HR-ESI-MS), nuclear magnetic resonance (NMR), optical rotatory dispersion (ORD) and acid hydrolysis. In vitro assay revealed that compounds 6, 7 and 14 showed obvious inhibitory activity against tyrosinase.