Melanogenesis inhibitors from Oenothera laciniata extracts

Oenothera laciniata Hill (Onagraceae), a perennial herb, is used to treat various inflammatory diseases such as systemic lupus erythematosus, ankylosing spondylitis, and rheumatoid arthritis. However, the phytochemical and the anti-melanogenic studies of O. laciniata are not identified. The aim of this study compared the anti-melanogenic activity of methanolic extract of O. laciniata (OLM) and its different soluble fractions, including ethyl acetate (OLEF), n-butanol (OLBF), and water (OLWF), by determing the inhibition of cellular melanin content and tyrosinase activity in B16F10 melanoma cell. The melanin synthesis proteins were also quantified by western blot assay, including tyrosinase, tyrosinase related protein-1 (TRP-1), tyrosinase related protein-2 (TRP-2), microphthalmia-associated transcription factor (MITF), phospho-cAMP-response element binding protein (p-CREB), phospho-extracellular-signal-regulated kinase (ERK), and phospho-c-jun N-terminal kinase (JNK). The results showed that OLM and its fractions decreased melanin production and inhibited tyrosinase activity in a dose-dependent manner in B16F10 melanoma cells. Moreover, OLM and its fractions demonstrated that induced down-regulation of melanogenesis via inhibiting p-CREB and subsequently reducing the expression of MITF, which in turn down-regulated tyrosinase and TRP-2 activities at the protein levels, but not inhibit TRP-1 expression in B16F10 cell. The results also indicated that OLM, OLBF, and OLWF reduced melanogenesis through an increase in ERK phosphorylation, but OLEF inhibited melanogenesis by inducing JNK phosphorylation. These results suggest that O. laciniata has great potential for becoming anti-melanogenesis agents in cosmetics.