Chemical exploration of 4-(4-fluorobenzyl)piperidine fragment for the development of new tyrosinase inhibitors.

Tyrosinase is involved in the production of melanin through the hydroxylation of monophenols to o-diphenols. The role of this enzyme was extensively studied in order to identify new therapeutics preventing skin pigmentation and melanoma. In this work we initially identified the 3-(4-benzylpiperidin-1-yl)-1-(1H-indol-3-yl)propan-1-one (1a) as promising mushroom tyrosinase inhibitor (IC = 252 μM). Then, several chemical modifications were performed and new analogues related to compound 1a were synthesized. Biochemical assays demonstrated that several obtained compounds proved to be effective inhibitors showing IC values lower both than "lead compound" 1a and reference inhibitor kojic acid, as a well-known tyrosinase inhibitor. The inhibition kinetics analyzed by Lineweaver-Burk plots revealed that compounds 2 a-c and 10b act as non-competitive inhibitors while the most active inhibitor 2d (IC = 7.56 μM) is a mixed-type inhibitor. Furthermore, experimental and computational structural studies were performed in order to clarify the binding mode of the derivative 2d.