Synthesis, biological profiling, and computational investigation of 1,2,4-triazole-5-thione–quinoline Schiff base hybrids

Aims To synthesize novel 1,2,4-triazole-5-thione-quinoline Schiff base hybrids and evaluate their urease inhibitory, antimicrobial, antioxidant, and computational properties.Materials and methods Two series of compounds, 7(a–d) and 8(a–d), were synthesized and structurally characterized by Fourier Transform-Infrared (FT-IR), 1 H/13C Nuclear Magnetic Resonance (NMR), mass spectrometry, and elemental analysis. Urease inhibition was determined spectrophotometrically. Antimicrobial activity was assessed by disc diffusion and broth microdilution methods. Antioxidant activity was evaluated using ferric-reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. Density functional theory (DFT) and molecular docking studies were also performed.Results and conclusions Compounds 7c and 8c showed the strongest urease inhibitory activity, each with an IC50 value of 1.37 mM. 8c displayed the best docking score (−7.6 kcal/mol), while 7c showed favorable binding affinity (−6.9 kcal/mol). Antimicrobial screening revealed selective activity mainly against Gram-positive bacteria and fungi, while Gram-negative bacteria were generally resistant. Compound 7d displayed the broadest antimicrobial profile, with minimum inhibition concentration (MIC) values of 39.06 µg/mL against Staphylococcus aureus and 19.53 µg/mL against Streptococcus pyogenes. In antioxidant assays, 7d and 8d showed the highest FRAP values, whereas 8c and 8a showed the strongest DPPH radical-scavenging activity. DFT results supported the observed structure–activity relationships.