Design, synthesis, antibacterial activity, and mechanistic studies of Ebselen derivatives against methicillin-resistant Staphylococcus aureus.

The rapid emergence of methicillin-resistant Staphylococcus aureus (MRSA) necessitates the development of novel antibacterial agents with distinct mechanisms of action. Ebselen, has shown promising antibacterial activity through disruption of redox homeostasis. However, its poor aqueous solubility and limited therapeutic potential call for further structural optimization. In this study, 29 ebselen derivatives were designed and synthesized to systematically explore structure-activity relationships (SAR) and improve antibacterial efficacy. Antibacterial profiling evaluation identified the most potent compound HX-27, which exhibited strong activity against MRSA, with minimum inhibitory concentrations (MICs) as low as 2 μM. Its MBC was >16 μM, indicating predominantly bacteriostatic activity at low concentrations. Moreover, HX-27 demonstrated rapid bactericidal activity and effectively inhibited biofilm formation with low hemolytic activity and minimal cytotoxicity. Mechanistic investigations revealed that HX-27 exerts a pronounced membrane-disruptive effect, leading to loss of membrane integrity and bacterial cell death. Integrated metabolomic and proteomic analyses further demonstrated that ebselen derivatives induce significant perturbations in sulfur-containing amino acid metabolism and intracellular redox balance, while also affecting central metabolic pathways and protein transport systems. These results indicate that the antibacterial activity of ebselen derivatives arises from multi-target mechanisms involving both membrane disruption and metabolic dysregulation. Notably, HX-27 displayed satisfactory aqueous solubility and excellent in vivo efficacy in a Galleria mellonella infection model, significantly improving survival under severe infection conditions. Overall, this study establishes a comprehensive structure-activity-mechanism framework for ebselen derivatives and identifies promising lead compounds for the development of novel therapeutics against drug-resistant bacterial infections.