Tyrosinase inhibitory components from the seeds of Cassia tora

Ten compounds (1-10) isolated from the seeds of Cassia tora were evaluated for tyrosinase inhibition. Compounds 3, 4, and 7 inhibited tyrosinase enzymatic activity in a dose-dependent manner, with IC50 values of 3.0 +/- 0.8, 7.0 +/- 0.4, and 9.2 +/- 3.4 mu M, respectively. Kinetic analyses revealed a mechanism consistent with competitive inhibition. In silico molecular docking showed that compounds 3 and 4 docked in the active site of tyrosinase, whereas 7 interacted with Ala246 and Val248 at outside of the active site, and His244 and Glu256 at inside. Additionally, compounds 3, 4, and 7 suppressed melanogenesis in alpha-MSH-treated B16F10 melanoma cells at a concentration of 10 mu M.