Silymarin inhibits melanin synthesis in melanocyte cells.

OBJECTIVES: The aim was to search for inhibitors of melanogenesis from natural resources. METHODS: The inhibitory effect of silymarin on melanogenesis in a spontaneously immortalized mouse melanocyte cell line, Mel-Ab, was studied. KEY FINDINGS: Silymarin significantly prevented melanin production in a dose-dependent manner with an IC50 value (concentration producing 50% maximal inhibition) of 28.2 microg/ml, without effects on cell viability. Also, silymarin inhibited L-DOPA oxidation activity of tyrosinase, the rate-limiting melanogenic enzyme, in cell based-systems but it did not directly affect cell-free tyrosinase activity. Furthermore, Western blot analysis indicated that silymarin decreased the expression of tyrosinase protein. CONCLUSIONS: This study suggests that the depigmenting effect of silymarin might be attributable to inhibition of tyrosinase expression and that silymarin may be useful as a natural skin-lightening agent.