Ampyrone increases pigmentation in a human 3D epidermal model, The top row shows visible epidermal darkening after treatment every other day with ampyrone for 21 days as compared to negative control. The bottom row shows magnification of epidermal cells revealing increased melanin synthesis in the ampyrone treated melanocytes as compared to negative control. Positive control is alpha-melanocyte stimulating hormone (αMSH) plus beta-fibroblast growth factor (βFGF). Photo by Dr.

Tyrosinase (Tyr) catalyzes hydroquinone (HQ) oxidation via two main pathways. The HBQ pathway directly oxidizes HQ to 2-hydroxy-1,4-benzoquinone (HBQ), which dimerizes and forms hydroquinone-eumelanin (HQ-EM). The BQ pathway involves dopaquinone (DQ)-mediated redox exchange producing p-benzoquinone (BQ), which reacts with cysteine (Cys) to form 2-S-cysteinylhydroquinone (Cys-HQ) and further oxidizes to hydroquinone-pheomelanin (HQ-PM). These pathways illustrate the enzymatic