Abstract
Previous studies have confirmed the anti-melanogenic effect of the aerial part of Pueraria lobata, however, due to its inherent color, P. lobata has limited commercial use. In this study, an extract (GALM-DC) of the aerial part of P. lobata having improved color by the use of activated carbon was obtained. Furthermore, the active compound neobavaisoflavone (NBI) was identified from GALM-DC. The effect of NBI on melanogenesis, tyrosinase activity, α-glucosidase activity, and mechanism of action in melanocytes was investigated. Tyrosinase activity, melanin contents and the expression of melanin-related genes and proteins were determined in B16F10 cells. NBI reduced melanin synthesis and tyrosinase activity. Furthermore, NBI treatment reduced the mRNA and protein expression levels of MITF, TRP-1, and tyrosinase. NBI also works by phosphorylating and activating proteins that inhibit melanogenesis, such as GSK3β and ERK. Specific inhibitors of Akt/GSK-3β (LY294002) and MEK/ERK (PD98059) signaling prevented the inhibition of melanogenesis by NBI. NBI inhibited melanin production through the regulation of MEK/ERK and Akt/GSK-3β signaling pathways in α-MSH-stimulated B16F10 cells. NBI suppresses tyrosinase activity and melanogenesis through inhibition of α-glucosidase activity. Besides, NBI significantly reduced melanogenesis in a reconstructed human 3D skin model. In conclusion, these results suggest that NBI has potential as a skin-whitening agent for hyperpigmentation.
Highlights
Melanin is produced from melanocytes secreted between the epidermis and the dermis
Melanin synthesis is stimulated by several agents and conditions, including α-melanocyte stimulating hormone (α-MSH), isobutyl methylxanthine (IBMX), and UV radiation
Daidzein, and genistein, which are contained in the aerial part of P. lobata, have been reported to exert anti-melanogenic effects via Microphthalmia-associated transcription factor (MITF) [41,42]
Summary
Melanin is produced from melanocytes secreted between the epidermis and the dermis. Melanin is a phenolic polymer widely distributed in plants and animals, and a major factor determining the color of the skin and hair functions to inhibit damage to skin cells by external stimuli, such as ultraviolet (UV) light and free radicals [1,2]. When melanin is over-synthesized, it is deposited on the surface of the skin, causing various pigmentations, such as spots and freckles, and promoting skin aging [3]. Melanin synthesis is stimulated by several agents and conditions, including α-melanocyte stimulating hormone (α-MSH), isobutyl methylxanthine (IBMX), and UV radiation. The first two steps in melanin synthesis, from L-tyrosine to Molecules 2020, 25, 2683; doi:10.3390/molecules25112683 www.mdpi.com/journal/molecules Dermal hyperpigmentation may depend on increased numbers of melanocytes or increased melanogenic enzyme activities [4,5].
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