Synthesis and Evaluation of Alkoxy-Substituted Thiourea Derivatives as Antifouling Agents in Marine Ecosystem Interests

The incorporation of alkoxy-substituted chain into thiourea moiety has attracted considerable interest in recent years due to its promising antimicrobial and antibacterial activities, making them potential candidates for antifouling applications. In this study, two new alkoxy-substituted thiourea derivatives, namely; N-(4-(octyloxy)phenyl)-N’-(4-trifluoromethylbenzoyl)thiourea (3a) and N-(4-(octyloxy)phenyl)-N’-(4-cyanobenzoyl)thiourea (3b) were designed, synthesized, and evaluated for antifouling properties. The compounds were structurally and physiochemically characterized using ¹H and ¹³C NMR spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, UV–visible spectroscopy, and thermogravimetric analysis (TGA). In turn, antifouling activities were assessed against Bacillus subtilis, Staphylococcus epidermidis, Staphylococcus aureus, and Escherichia coli through preventive and detachment assays. Notably, compound 3b exhibited strong antifouling performance, achieving up to 94.56% biofilm reduction in the preventive assay, due to the presence of the electron-withdrawing cyano (–CN) substituent. These findings highlight the potential of alkoxy-substituted thiourea derivatives as effective antifouling agents, warranting further exploration for use in fouling-release applications.