Abstract
To identify novel tyrosinase inhibitors, a series of isocryptolepine 'aza' type acyl thiourea analogs (6a-6h) were designed and synthesized using a multistep strategy. Spectroscopic methods including FTIR, UV-vis, 1H NMR, 13C NMR, and EI-MS were utilized for detailed analysis of compounds. Their tyrosinase inhibitory activities were evaluated in vitro, demonstrating superior potency compared with kojic acid (IC50 = 16.83 ± 1.162 μM). The synthesized compounds exhibited IC50 values ranging from 0.832 ± 0.03 to 7.945 ± 0.63 μM, with compound 6g emerging as the most potent inhibitor (IC50 = 0.832 ± 0.03 μM). Kinetic studies revealed competitive inhibition by compound 6g, highlighting its potential as a lead candidate for treating tyrosinase-mediated hyperpigmentation. Additional evaluations showed that these compounds also effectively inhibited other enzymes involved in cancer progression, indicating their broad therapeutic potential. Molecular modeling studies against the tyrosinase enzyme (PDB: 4OUA) confirmed strong binding interactions, while structure-activity relationship analyses provided insights into their inhibitory mechanisms. Geometry optimization of the compounds, supporting their favorable molecular properties. Drug-likeness evaluations further validated the potential of these analogs as promising anti-tyrosinase agents. Overall, this study establishes compound 6g and its analogs as compelling candidates for further development in hyperpigmentation and cancer therapeutics.