Effects of α-arbutin and β-arbutin on melanogenesis in murine melanocytes cocultured with murine keratinocytes

Objective To investigate the effects of α-arbutin and β-arbntin on tyrosinase activity and melanin content in murine melanocytes (MCs) cocultured with murine keratinocytes (KCs) and to define whether the difference in configuration of glucosidic linkage (s) of hydroquinone glucosides is correlated with their inhibitory activities against tyrosinase. Methods Mouse MCs of the line melan-a and mouse KCs of the line SP-1 were cocuhured at a ratio of 1:5. The ceils were treated for 4 days with the compound [α-arbutin or β-arbutin 0.04, 0.2, or 1 mg/ml, nicotinamide 0.04, 0.2, or 1 mg/ml, and 8-methoxypsoralen (S-MOP) 10, 50, 100 μmol/L respectively]. Phenotypic alterations of MCs cocuhured with KCs were examined and photographed by phase-contrast microscopy. The viability/proliferation of the treated ceils was measured by methylthiazol tetrazolium (MTT) assay. The tyrosinase (monophenolase and o-diphenolase) activities were determined by incorporation of radioactive L-[14C] tyrosine substrate into the melanin, and the melanin content was determined by spectrophotometric assay. Results 1 mg/ml nicotinamide slightly increased the melanin in dendrites and cytoplasm of the MCs. The dendrites of the MCs treated by 1 mg/ml α-arbutin and β-arbutin were long and thin and melanin was less compared with the control group. 8-MOP significantly promoted the proliferation of the melan-a and SP-1 cells, especially of the melan-a cells. Nicotinamide, α-arbutin, and β-arbutin did not significantly influence the proliferation of the MCs and KCs. The tyrosinase activity and melanin content were increased by 8-MOP dose-dependently and dramatically inhibited by α-arbutin, and β-arbntin dose-dependently. The inhibitory effect of α-arbutin on tyrosinase was stronger than that of β-arbutin at a dose of 1 mg/ml (the tyrosinase activity:37%±4% vs 54%±9%, P=0.034).Conclusion α-arbutin is an effective and safe ingredient for skin-whitening purpose in vitro experiment. Clinical implication remains to be further evaluated by in vivo studies. Key words: Arbutin;  Metoxsalen ;  Tyrosinase ;  Anomer