Discovery of bis-thiourea derivatives as potent tyrosinase inhibitors: combined experimental and computational study

Tyrosinase, a key enzyme in melanin synthesis, serves as a primary target for developing depigmenting agents. The search for novel tyrosinase inhibitors is needed due to the adverse effects of current inhibitors. This study evaluated 16 bis-thiourea derivatives using in vitro and in silico methods, identifying compound 4, with chlorine substituents, as the most potent inhibitor. Compound 4 outperformed kojic acid in inhibiting mushroom tyrosinase activity and interacted with catalytic copper ions and active site residues, as revealed by molecular docking and copper-chelating assay. Molecular dynamics simulation and MM/PBSA-based free energy calculations confirmed the greater stability and binding affinity of the compound 4-tyrosinase complex in an aqueous environment compared to kojic acid-tyrosinase complex. Melanin assay revealed that compound 4 significantly suppressed melanin production in B16F10 melanoma cells, showing stronger anti-melanogenic activity than kojic acid. Drug-likeness predictions confirmed its compliance with Lipinski's rule of five, supporting bis-thiourea derivatives as promising tyrosinase inhibitors.