Eupafolin, a skin whitening flavonoid isolated from Phyla nodiflora, downregulated melanogenesis: Role of MAPK and Akt pathways

Ethnopharmacological relevance: In hyperpigmentation disorders marked by melanin overproduction in the skin, including melisma and freckles, melanogenesis is caused by tyrosinase overexpression. Natural medicinal resources, like Phyla nodiflora, a traditional Chinese herbal medicine, have been used for a long time to management of dermatological conditions, such as skin inflammation and melanogenesis. Eupafolin, a functional flavonoid isolated from Phyla nodiflora, is an herbal tea constituent and possesses anti-inflammatory and anticancer activities. However, molecular mechanisms of eupafolin-mediated antimelanogenesis remain unknown. We thus focused on its antimelanogenesis effects in B16F10 mouse melanoma cells. Material and methods: B16F10 cells were treated with eupafolin (0.01, 0.1, 1, and 10 mu M) in a dose-escalation-dependent manner for the determination of melanin, tyrosinase activity and melanogenesis protein levels by ELISA or western blot analysis. Results: Eupafolin treatment significantly reduced cellular melanin content and tyrosinase activity in a dose-dependent manner (P < 0.05), and no cytotoxic effects were observed. Eupafolin was associated with reduction in the levels of phospho-cAMP response element-binding protein and microphthalmia-associated transcription factor (MITF), and downregulation of tyrosinase synthesis and tyrosinase-related protein expression, leading to inhibit melanin production. In addition, eupafolin significantly induced the phosphorylation of ERK1/2 and p38 MAPK, whereas the decreased effect was observed in the phosphorylation of Akt Moreover, inhibitors of these signals recovered or attenuated the inhibitory effects of eupafolin on melanogenesis. Conclusions: Our results seem that inhibition of Akt and activation of phospho-ERK or p38 MAPK may lead to the suppression of melanogenesis in eupafolin-treated B16F10 mouse melanoma cells. (C) 2013 Elsevier Ireland Ltd. All rights reserved.