Populus nigra (Salicaceae) absolute rich in phenolic acids, phenylpropanoïds and flavonoids as a new potent tyrosinase inhibitor

The purpose of this study was to evaluate the tyrosinase inhibitory capacity of Populus nigra buds absolute (PBA) and compare it to kojic acid (KA), controversial reference tyrosinase inhibitor. Populus nigra buds were extracted with hexane and ethanol to obtain PBA. The inhibitory effect of this absolute was first tested on the mushroom Agaricus bisporus tyrosinase. Then the depigmenting potential of PBA was tested on B16F10 murine melanocytes by assaying the activity of tyrosinase and melanin content. Consecutively, a microscopic analysis of intracellular melanin granules was performed. Finally, melanised reconstructed human epidermis (RHE) were used to assess the lightening potential activity of this PBA on human skin. Results show that PBA inhibits A. bisporus tyrosinase (IC50 = 77 ± 8 ppm) and inhibits melanocytes B16F10 tyrosinase (IC50 = 27 ± 1 ppm). PBA decreases intracellular melanin levels, with 50% loss at 39 ± 9 ppm. Finally, PBA at 1000 ppm lightens RHE and decreases their melanin content of 20%. PBA is a strong inhibitor of tyrosinase and reduces melanogenesis in melanocytes B16F10. Thus, PBA has potential applications in skin-lightening cosmetics.