Antioxidant, antibacterial, enzyme inhibition and fluorescence characteristics of unsymmetrical thiourea derivatives

Abstract

A series of six unsymmetrical thiourea derivatives, namely 1-cyclohexyl-3-(pyridin-2-yl) thiourea (1), 1-cyclohexyl-3-(3-methylpyridin-2-yl)thiourea (2), 1-cyclohexyl-3-(2,4-dimethylphenyl) thiourea (3), 1-(4-chlorophenyl)-3-cyclohexylthiourea (4), 1-(3-methylpyridin-2-yl)-3-phenylthiourea (5), and 1-(3-chlorophenyl)-3-phenylthiourea (6), were successfully synthesized via reaction between different amines with isothiocyanates under a non-catalytic environment. Structural elucidation of compounds (1–6) was performed using FT-IR and NMR (1H and 13C) spectroscopy. The infrared spectra displayed characteristic stretching vibrations, while the 13C NMR chemical shifts of the thiourea moiety (CS) were observed in the range of 179.1–181.4 ppm. The antioxidative and antimicrobial properties of the compounds were assessed, as well as their inhibitory effects on acetylcholinesterase and butyrylcholinesterase were evaluated. In order to analyze the fluorescence characteristics of each compound (1–6), the excitation (λex) and emission (λem) wavelengths were scanned within the range of 250–750 nm, with the solvent blank serving as a standard. It was observed that when dissolved in acetone, toluene, tetrahydrofuran, and ethyl acetate, these compounds exhibited emission peaks ranging from 367 to 581 nm and absorption peaks ranging from 275 to 432 nm.

Keywords

• Thiourea derivatives
• Unsymmetrical thioureas
• Structural characterization
• Free radical scavenging
• Antimicrobial
• Fluorescence characteristics