Effects of the isoflavone puerarin and its glycosides on melanogenesis in B16 melanocytes

We investigated the effects of puerarin (8-C-glucosyl-7,4′-dihydroxy isoflavone), an isoflavone found in Kudzu roots (Pueraria lobata), and its glycosides (enzymatically synthesised, water-soluble derivatives of puerarin) on melanogenesis in vitro. Puerarin and its glycosides reduced mushroom tyrosinase activity by 88 and 67% at 4.8 mM, respectively, in a concentration-dependent manner. The puerarin glycosides were less effective than puerarin at the same concentration but showed a comparable inhibitory effect at a concentration at which puerarin is insoluble in water. In cultured B16 melanocytes, the melanin content was reduced significantly; moreover, tyrosinase activity was inhibited significantly by both puerarin and its glycosides when added at a concentration of 480 μM. DNA microarray and RT-PCR analyses showed significant downregulation of the expression of microphthalmia-associated transcription factor (MITF) and its target genes. The protein expression of MITF and tyrosinase was also downregulated significantly by 40 and 50%, respectively. Our findings suggest that puerarin and its glycosides cause hypopigmentation via dual mechanisms: by inhibiting tyrosinase activity directly and by altering the expression of melanogenesis-related genes, such as MITF and tyrosinase. Therefore, puerarin and its glycosides may have potential for the development of functional cosmetics causing hypopigmentation.