Design, Synthesis, Biological Evaluation of Novel Substituted Benzoxazole-Schiff Base Derivatives as Antibacterial Agents

A series of benzoxazole-Schiff base hybrids were synthesized and evaluated for broad-spectrum anti-infective activity. Two compounds emerged as potent antibacterial agents, inhibiting S. aureus [including methicillin-resistant Staphylococcus aureus (MRSA)], B. subtilis at 2–8 µg/mL, and E. coli at 16 µg.mL. One lead analogue combined the highest antibacterial activity with negligible mammalian cytotoxicity and demonstrated strong synergism with clinically relevant antibiotics. At elevated concentrations, this compound eradicated MRSA, disrupted pre-formed biofilms, and significantly delayed resistance development compared with norfloxacin. In-silico ADME profiling predicted that several of the synthesized compounds comply with Lipinski’s rules and exhibit favorable oral bioavailability and intestinal permeability. Mechanistic investigations attributed bacterial lethality to rapid membrane depolarization and ultrastructural disintegration. In a murine MRSA keratitis model, topically applied this lead analogue achieved dose-dependent bacterial clearance from infected corneas, underscoring its therapeutic potential for treating ocular and potentially systemic infections.