Silymarin inhibits melanin synthesis in melanocyte cells

The aim was to search for inhibitors of melanogenesis from natural resources. The inhibitory effect of silymarin on melanogenesis in a spontaneously immortalized mouse melanocyte cell line, Mel-Ab, was studied. Silymarin significantly prevented melanin production in a dose-dependent manner with an IC50 value (concentration producing 50% maximal inhibition) of 28.2 μg/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. 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.