Rhamnetin attenuates melanogenesis by suppressing oxidative stress and pro-inflammatory mediators.

Rhamnetin is a naturally occurring polyphenolic compound. In this report, experimental evidence is presented on the suppression of melanogenesis by rhamnetin using B16 murine melanoma cells (B16 cells). To document the underlying anti-melanogenic action of rhamnetin, several key biochemical mediators were quantified: superoxide (O2(•-)), nitric oxide (·NO) and peroxynitrite (ONOO(-)) in vitro, and total reactive species (RS) generation, O2(•-), ·NO and ONOO(-), reduced glutathione (GSH)/GSH-to-oxidized glutathione (GSSG) ratio, prostaglandin E2 (PGE2) and thromboxane B2 (TXB2) in B16 cells. Results revealed that rhamnetin inhibited murine tyrosinase activity, suppressed melanin content and oxidative stress, reducing O2(•-),·NO and ONOO(-) in vitro and total RS generation, O2(•-), ·NO and ONOO(-) in B16 cells, while maintaining a well-balanced GSH/GSSG ratio in B16 cells. Results further revealed that rhamnetin suppressed key pro-inflammatory mediators such as PGE2 and TXB2. Thus, these results strongly indicate that rhamnetin has powerful anti-melanogenic properties through its anti-oxidative and anti-inflammatory actions.