Multifaceted Evaluation of Acetophenones: From RSM-Assisted Optimization to In Vivo Depigmentation and Molecular Docking Validation

Abstract

Hyperpigmentation is characterized by excessive melanin production, often associated with skin irritation and inflammation, leading to uneven skin tone. This underscores the need for safer and more effective depigmenting agents. In this study, the benzoic acid derivative, 4-hydroxyacetophenone (2), was synthesized by demethylation of 4-methoxyacetophenone (1) using a long-chain thiol. For the first time, this demethylation reaction was optimized using Response Surface Methodology (RSM), offering an efficient approach for hydroxylated compound synthesis. The optimized conditions, 128.85°C, 4.00 mmol 1-dodecanethiol, and 20.752 minutes reaction time, resulted in maximum product yield. Subsequent evaluations demonstrated that no significant acute toxicity was observed in the four key parameters. Depigmentation studies showed significant effects of both compounds 1 and 2 compared to the control group in the zebrafish model. This is the first report demonstrating the depigmenting effect of compound 2 in an in vivo zebrafish model, which is further supported by the tyrosinase inhibitory properties of the compound with an IC₅₀ value of 62.72 ± 1.39 µM. Molecular docking confirmed the stronger binding affinity of compound 2 to tyrosinase, outperforming 1 and the standard control, 1-phenyl-2-thiourea (PTU). Overall, this work highlights the effectiveness of RSM optimization and the potential of hydroxylated acetophenones as anti-tyrosinase agents.