RESUMEN
BACKGROUND: Melanoston is a new melanogenesis inhibitor isolated from yeast. However, little is known about the mechanism of this agent in melanogenesis and also its clinical effectiveness on hyperpigmented lesions. OBJECTIVE: The purpose of this study was to examine the inhibitory effect of melanoston on in vivo activity of tyrosinase. METHODS: We assessed tyrosinase activity, which participates in the synthesis of melanin pigment and resides in melanocytes of guinea pig's epidermis, using immunohistochemical methods after application of 0.1% and 0.01% melanoston on the skin of guinea pigs. We also conducted an 8-week clinical trial on 30 women volunteers to determine the clinical efficacy and safety of melanoston. Participants were instructed to apply melanoston and vehicle on 7 small areas of skin on both forearms for 8 weeks, before and after UVB exposure, and they were examined daily for the first week, then weekly thereafter. RESULTS: The lowest level of tyrosinase activity was observed at the 3rd week after application of 0.1% and 0.01% melanoston on the skin of guinea pigs, and melanoston had a relatively strong inhibitory effect on tyrosinase, as compared with vehicle and arbutin. Differences in the degree of pigmentation between areas treated with 0.5% melanoston and application of vehicle only, and between before and after UVB exposure were considered to be significant (p<0.001, on each time). CONCLUSION: We conclude that melanoston has an inhibitory effect on melanogenesis and some eliminating effect on preexisting pigmentation.