Abstract: Objective To explore the effects of traditional Chinese medicinal herbs (TCMHs) on the expression of tyrosinase gene, melanogenesis and proliferation of melanocytes and elucidate the mechanism of TCMHs in promoting melanogenesis. Methods Seven TCMHs including Herba Ecliptae, Spica Prunellae, Caulis Spatholob, etc, which were known to be effective in activating tyrosinase in vivo, were selected. Brownish guinea pigs were selected as the experimental model. The mRNA in situ hybridization (ISH), Schmorl-staining and dopa-oxygenase staining were performed to observe the effects of TCMHs on gene expression of tyrosinase, melanogenesis and melanocyte proliferation. Results The mRNA ISH showed that these seven drugs, especially Herba Ecliptae,Spica Prunellae and Tribulus terrestris could significantly increase the number of positive cells and the intensity of hybridization signal in the treated group as compared with that in the control group (P<0.01). In Schmorl staining and dopa-oxygenase staining, the number of cells containing melanin granules and dopa-staining positive cells per 100 basal layer cells were significantly increased in TCM treated groups (P<0.05), and these two effects of TCMHs were not parallel with each other (P>0.1). Conclusions These results suggested that these 7 TCMHs including Herba Ecliptae can upregulate the gene expression of tyrosinase, enhance the melanogenesis and promote the proliferation of melanocytes.

Key words: Drugs, Chinese herbal, Monophenol monooxygenase, Melanins