Objectives: The aim of the study was to determine the mechanism of the whitening effect of acteoside.
Methods: We used tyrosinase activity and melanin production stimulated in B16 melanoma cells by alpha-melanocyte stimulating hormone (alpha-MSH) or forskolin to measure the whitening effect of acteoside.
Key findings: Acteoside did not directly inhibit mushroom tyrosinase activity, but dose-dependently inhibited tyrosinase activity and melanin production in B16 melanoma cells stimulated by 1 micromol/l alpha-MSH. Acteoside also reduced cyclic AMP levels in cells stimulated by 1 micromol/l alpha-MSH, suggesting direct inhibition of adenyl cyclase. Acteoside also inhibited production of both melanin and cyclic AMP in cells stimulated by 1 micromol/l forskolin, an adenyl cyclase activator. Acteoside showed antioxidant activity in a cell-free DPPH (1-diphenyl-2-picrylhydroazyl) assay and inhibited generation of intracellular reactive oxygen species.
Conclusions: These results suggest that the whitening activity of acteoside results from inhibition of adenyl cyclase and alpha-MSH signalling.