Tyrosinase Inhibitory Chemical Constituents from Cleyera japonica Thunberg Branches

Bioassay-guided investigation of the branches of Cleyera japonica led to the isolation of four phenolic constituents: 3,3’-di-O-methylellagic acid (1), 3,3’-di-O-methylellagic acid 4’-O-β-D-xylofuranoside (2),  3,5,7-trihydroxychromone 3-O-α-L-arabinofuranoside (3) and aviculin (4). Their structures were elucidated on the basis of spectral studies, as well as by comparison with literature data. Tyrosinase inhibition activities were carried out for the isolated compounds using arbutin as a positive control. Among them, compound 2 was identified as a potent tyrosinase inhibitor. It inhibited mushroom tyrosinase with an IC50 value of 0.078 mM, which is about three times more active than arbutin (IC50 =0.25 mM). All of the compounds 1-4 were isolated for the first time from this plant.