Objective: To study the effects of the decoction of Tribulus terrestris L on tyrosinase activity and melanogenesis.
Methods: MTT was employed to study the proliferation of human melanocytes cultured in vitro, and tyrosinase activity was estimated by measuring the rate of oxidation of DL-dopa, after the cells were treated with different concentrations of decoction of Tribulus terrestris L.
Results: The treatment with the decoction increased the amount of melanin at higher concentrations but act to the reverse effect at lower concentrations, with the best concentrations for promoting and inhibiting the cell growth being 1.5 mg/ml (P<0.05) and 0.5 mg/ml (P<0.05) respectively. At high concentrations the decoction enhanced the tyrosinase activity that was inhibited at low concentrations. The best concentrations for enhancing and inhibiting tyrosinase activity were 100 mg/ml (P<0.05) and 10 mg/ml (P<0.05) respectively.
Conclusion: Tribulus terrestris L decoction exercises a two-way regulation on the activity of tyrosinase and the proliferation of melanocytes.