Abstract: Objective To investigate the effects of Qibai-mixture on the proliferation,tyrosinase activity and melanogenesis of cultured human melanocytes.Methods The water decoction of Qibai-mixture, which consisted of huangqi,dangshen,baizhi,baijili,jixueteng,was concentrated to 3 g/mL,then was used to treat black,purple and blue rabbits by intragastric administration at a dose of 12 mL·kg^-1·d^-1 for three days.Serum samples were collected from the rabbits at 1 h,2 h and 5 h alter the last intragastric administration.Human melanocytes were cultured with the serum samples or drug-free serum as control for 24 or 48 h.The proliferation,tyrosinase activity and melanogenesis of melanocytes were detected by MTT method,DOPA-oxidation,and NaOH-assay,respectively.The mRNA expression of tyrosinase and microphthalmia transcription factor(MITF)was examined with semiquantitative RT-PCR.Results Compared with the control serum,the serum collected at 1 h and 2 h after the last administration could significantly stimulate the proliferation,up-regulate the activity of tyrosinase,promote the melaningenesis, and increase the mRNA expression of tyrosinase and MITF,of the cultured melanocytes.Conclusion These results demonstrate that Qibai-mixture could promote melanogenesis by directly acting on melanocytes and tyrosinase signal pathway.

Key words: Melanocytes, Monophenol monooxygenase, QIBAI-mixture, MITF