Synthesis, Structural Characterization, and Evaluation of the Antibacterial Activity of Chalcones Against Staphylococcus aureus Strains Overexpressing the NorA and MepA Efflux Pumps: An In Vitro, In Silico, and Molecular Approach

ABSTRACT Staphylococcus aureus is a commensal bacterium that can also cause infections and develop resistance to fluoroquinolones. An important resistance mechanism involves the NorA and MepA efflux pumps, overexpressed in strains 1199B and K2068. Three chalcones: CMABE, CMAPECTOX, and CMA 3 NO 2 were synthesized and evaluated through microbiological, fluorimetric, membrane permeability, and in silico assays. None showed direct antibacterial activity. In strain 1199B, CMAPECTOX and CMABE reduced the MIC of norfloxacin from 96 to 12 and 85.71 µg/mL, respectively, and the MIC of ethidium bromide (EtBr) from 67.92 to 6.01 and 60.51 µg/mL, whereas CMA 3 NO 2 was inactive. In strain K2068, all chalcones potentiated ciprofloxacin and reduced the EtBr MIC, but only CMAPECTOX significantly increased intracellular EtBr accumulation, although all compounds permeabilized the bacterial membrane. Molecular docking indicated that CMAPECTOX binds near the fluoroquinolone‐binding site in both pumps, supported by NMA‐based molecular dynamics showing reduced collective motions. ADMET predictions revealed favorable pharmacokinetic properties for all chalcones. CMAPECTOX exhibited the best predicted safety profile, with low organ toxicity and no first‐pass metabolism‐related hepatotoxicity. These findings identify CMAPECTOX as a promising antibacterial adjuvant targeting NorA and MepA efflux pumps.