Inhibition of melanogenesis by piceid isolated from Polygonum cuspidatum.

Piceid (5,4'-dihydroxystilbene-3-O-β-D-glucopyranoside) is one of the stilbenes found in Polygonum cuspidatum. Previous studies have shown that this compound has little effect on tyrosinase inhibition when compared with other stilbenes in a cell-free tyrosinase assay. Furthermore, its role for melanogenesis in melanocytes is relatively unknown. In melanocytes, piceid inhibits tyrosinase activity and melanin production in a concentration-dependent manner. To explore the action of piceid on melanogenesis, we studied its effect on several key cellular enzymes and a transcriptional factor known to be involved in melanogenesis, including: tyrosinase, tyrosinase-related protein 1, tyrosinase-related protein 2, and microphthalmia-associated transcription factor. Interestingly, the effects of piceid on hypopigmentation and inhibition of tyrosinase activity were better than those of arbutin, which is well known to inhibit melanin formation in melanocytes. In addition, piceid suppressed the mRNA and protein expression of the aforementioned enzymes and transcriptional factor in a concentration-dependent manner. In this regards, our results showed that piceid represents a safe and new candidate for a skin-lightening agent.