Targeting metallo-β-lactamase inhibition with Schiff bases of 4-amino-1,2,4-triazole-3-thione: In silico docking, molecular dynamics, and pharmacological assessments

Metallo-β-lactamases are zinc-dependent enzymes that hydrolyze and inactivate a wide range of β-lactam antibiotics, including penicillins, cephalosporins, and carbapenems, making them a significant factor in bacterial resistance. Therefore, developing inhibitors targeting metallo-β-lactamases is crucial for combating antibiotic resistance in Gram-negative bacteria and restoring the effectiveness of these essential antimicrobial agents. This study focuses on the synthesis, in silico docking, molecular dynamics simulations, and biological evaluation of twenty-one Schiff base analogs (6a–u) derived from trans-4-amino-5-(4-(4-chlorophenyl)cyclohexyl)-1,2,4-triazole-3-thione. Molecular docking studies were carried out on the New Delhi metallo-β-lactamase-1 active sites of Klebsiella pneumoniae (PDB: 5N0H) and Escherichia coli (PDB: 6KXI) to evaluate the binding interactions between the thiolate form of ligands and zinc ions. Docking analysis reveals that the synthesized analogs are stably positioned in the NDM-1 active site, aligning closely with zinc ions. The zinc ions in the active binding site coordinate with the nitrogen atoms of the triazole ring and the thiolate anion. Molecular Dynamics Simulations confirmed the stability of the protein-ligand complexes, demonstrating that the ligands maintained optimal positioning within the active site with minimal fluctuations in surrounding residues. The in vitro antibacterial activity of these analogs was evaluated at concentrations of 4 mg/L and 8 mg/L in combination with meropenem against various carbapenem-resistant Gram-negative isolates expressing NDM-1, Class A (SHV, TEM), or Class C (CMY) β-lactamases. The results indicated modest potentiation of meropenem's antibacterial activity, with a 2–3 fold increase in efficacy when used alongside the Schiff base analogs. Notably, two analogs emerged as significant hits in this study.