Tyrosinase Inhibitory Activity of Ethanol Extracts from Medicinal and Edible Plants Cultivated in Okinawa and Identification of a Water-Soluble Inhibitor from the Leaves of Nandina domestica

The tyrosinase inhibitory activity of the extracts of 53 parts of 36 plant species cultivated for edible and medicinal use in Okinawa was investigated. The extract of Nandina domestica showed potent activity among these. The inhibitor in the extract was purified by assay-guided fractionation to give a simple phenol glucoside. Although it was a known compound (4-β-D-glucopyranosyloxybenzoic acid), its inhibitory activity toward tyrosinase is revealed for the first time in this work.