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 (O-2(center dot-)), nitric oxide (center dot NO) and peroxynitrite (ONOO-) in vitro, and total reactive species (RS) generation, O-2(center dot-), center dot NO and ONOO-, reduced glutathione (GSH)/GSH-to-oxidized glutathione (GSSG) ratio, prostaglandin E-2 (PGE(2)) and thromboxane B-2 (TXB2) in B16 cells. Results revealed that rhamnetin inhibited murine tyrosinase activity, suppressed melanin content and oxidative stress, reducing O2(2)(center dot-), center dot NO and ONOO- in vitro and total RS generation, O-2(center dot-), center dot NO and ONOO- in B16 cells, while maintaining a well-balanced GSH/GSSG ratio in B16 cells. Results further revealed that rhamnetin suppressed key proinflammatory mediators such as PGE(2) and TXB2. Thus, these results strongly indicate that rhamnetin has powerful anti-melanogenic properties through its anti-oxidative and anti-inflammatory actions.