Design, synthesis, bioevaluation, and in silico insights of pyrazole-pyrrolinone and pyridazinone hybrids as potential antimicrobial agents

Abstract

The growing prevalence of antimicrobial resistance demands new molecular scaffolds capable of targeting planktonic pathogens and biofilm-associated infections. In this work, a series of new pyrazole-linked pyrrolinone and pyridazinone derivatives was designed and synthesized, starting from a pyrazolylfuran-2(3H)-one via selective ammonolysis and hydrazinolysis. The acid hydrazide obtained underwent heterocyclization, acylation, benzoylation, and condensation with aldehyde. The resulting compounds were evaluated for antimicrobial, antibiofilm, and mechanistic properties. Biological assessments included antimicrobial activity against five clinically relevant microbial strains, antibiofilm activity against Pseudomonas aeruginosa, cytotoxicity toward human fibroblasts, efflux pump inhibition studies, and molecular docking against Staphylococcus aureus PBP4 and Escherichia coli DNA gyrase B. Several derivatives showed pronounced strain-selective antimicrobial activity. Compounds 4, 6, 7, and particularly 10 showed strong antibacterial potency with MIC ranging from 1 to 8 µg mL⁻¹, while compounds 6, 8, 9, and 10 showed notable activity against Candida albicans. Importantly, compounds 8–10 achieved near-complete eradication of P. aeruginosa biofilms (≥99.999%) and significantly inhibited biofilm formation (≥80%). Efflux inhibition assays displayed a 44–55% decrease in ethidium bromide efflux, supporting a multimodal mechanism of action. Docking studies revealed favorable binding affinities (−7.12 to −8.24 kcal mol⁻¹), and cytotoxicity evaluation confirmed a favorable safety profile (IC₅₀ 120–200 µM). Among the evaluated compounds, pyrrolinone derivative 10 appeared as a promising antibiofilm and antimicrobial candidate for further preclinical development.