Synthesis, molecular modelling, and evaluation of new mono- and bis-isoxazolines as antibacterial agents: in vitro and in silico analysis

Abstract

This study aimed to design, synthesize, and evaluate a novel series of isoxazoline-thiosemicarbazone derivatives as potential antibacterial agents, supported by computational investigations. Compounds were synthesized and characterized using ¹H and ¹³C NMR and HRMS. Compounds 4a–d and 6 were evaluated for their in vitro antibacterial activity against Gram-positive and Gram-negative bacterial strains by determining their minimum inhibitory concentrations (MICs). Molecular docking studies were conducted to assess binding interactions with the PTGS2 protein, followed by molecular dynamics simulations to evaluate the stability of the ligand–protein complexes. MM-GBSA calculations were performed to estimate binding free energies, and in silico ADMET predictions were carried out to assess drug-likeness. Compounds 4a–d and 6 exhibited potent antibacterial activity, with MIC values ranging from 0.31 to 0.5 µg mL⁻¹. Molecular docking results revealed strong binding affinities of compound 4a toward the active site of PTGS2. Molecular dynamics confirmed the structural stability of the PTGS2-4a complex. MM-GBSA analysis demonstrated that PTGS2-4a displayed the most favorable binding free energy, showing superior or comparable performance to the reference inhibitor Resatorvid. In silico ADME-T analysis indicated acceptable pharmacokinetic properties. These results highlight compounds 4a–d as promising antibacterial candidates, providing a strong rationale for the development of novel isoxazoline-thiosemicarbazone-based antibacterial agents.