Flavonoids enhance melanogenesis in human melanoma cells

Flavonoids are pigmentary compounds existing widely in plants. We have reported that quercetin (3, 3', 4', 5, 7-pentahydroxylflavone), one of the typical flavonoids, strongly promotes melanogenesis by melanocytes. Meanwhile, there are 8000 or more flavonoids having a chemical structure different from each other in the natural world. Their distinctive chemical properties suggest that they may be different in melanogenic actions. In the present study, the melanogenic actions of 14 flavonoids were analyzed to correlate their chemical structures with melanogenic actions. To evaluate the effects of flavonoids on melanogenesis, the HMV II cell line derived from human malignant melanoma was used. Flavonols including quercetin, kaempferol, rhamnetin and fisetin, flavones including apigenin, luteolin and chrysin, and isoflavones including genestein showed melanogenesis-promoting actions but rutin, robinetin, myricetin, ipriflavone, epigalocatechin gallate (EGCg) and naringin did not. From analyses of the relationships between the chemical structures of flavonoids and their melanogenesis-promoting actions, it was inferred that a hydroxyl group bound to the phenyl group plays an important role in stimulating melanogenesis. From the above results, 8 flavonoids were identified as melanogenesis promoters. Also, correlations were established between the melanogenesis-promoting actions of flavonoids and their chemical structures.