Lindera obtusiloba BL. 70% EtOH extract induced ERK activation inhibits melanin synthesis in mouse B16F10 melanoma cells

Lindera obtusiloba BL. (LOB) is known to contain various bioactive constituents such as geranyl acetate, L-phellandrene, linderic acid and tsudzuic acid [1], and the plant is used for antioxidative activities and liver protection. In this study, we investigated the effects of a 70% ethyl alcohol leaf extract of LOB on melanogenesis using cultured mouse B16F10 melanoma cells. In mammalian melanocytes, melanin is synthesized within melanosomes that contain at leat three structurally related enzymes: tyrosinase, tyrosinase related protein-1 (TRP-1), and TRP-2 [2]. Microphthalmia-associated transcription factor (MITF) is involved in the pigmentation, proliferation, and survival of melanocytes [3]. Further more, MITF strongly stimulates tyrosinase and TRP-1 promoter activities, indicating that MITF is an important transcriptional regulator of melanogenesis [4]. Our results show that LOB was found to down-regulate microphthalmia-associated transcription factor (MITF) and tyrosinase, and western blotting showed that LOB induces the activation of extracellular signal-regulated kinase (ERK). These results suggest that the ERK pathway is involved in the melanogenic signaling cascade [5], and the ERK activation by LOB reduces melanin synthesis via MITF down-regulation.

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