Chemical Synthesis and Evaluation of the Antibacterial Activity of the Amino chalcone in Efflux Pump-Carrying Strains

Given the ability of microorganisms to develop drug resistance at a faster pace than the development of new drugs, it becomes urgent to seek alternatives capable of restoring the efficacy of antibiotics, especially against pathogens such as Staphylococcus aureus, known for its versatility in expressing resistance mechanisms.Synthetic chalcones have been extensively investigated as efflux pump inhibitors due to their structural flexibility and ease of chemical modification. Can cite studies that show chalcones derived from Croton anisodontus for their ability to inhibit the NorA and MepA efflux pumps in Staphylococcus aureus strains (1199B and K2068) and studies chalcones act as inhibitors of the NorA efflux pump in whole cells and everted membrane vesicles of Staphylococcus aureus. Among these mechanisms, the NorA and MepA efflux pumps stand out, as they are responsible for expelling antibiotics from the bacterial cell interior. In this context, the present study investigated the potential of the chalcone (E)-1-(3-aminophenyl)-3-(4-chlorophenyl)prop-2-en-1-one as a possible inhibitor of these efflux systems. Initial screening was conducted through in silico studies, followed by in vitro assays determination of minimum inhibitory concentration (MIC), and fluorescence tests using ethidium bromide EtBr and SYTOX Green). Molecular docking results revealed that this chalcone interacts with amino acid residues described in the literature as essential for efflux pump activity (Glu222 and Phe303 in NorA; Tyr35 and Met172 in MepA). The binding distances and energies obtained were consistent with potential inhibitory activity, suggesting that chalcone may interfere with the functionality of these proteins. In vitro assays showed a significant reduction in the MIC of antibiotics such as norfloxacin and ciprofloxacin in resistant strains, indicating a potentiating effect. Furthermore, fluorescence tests demonstrated increased retention of ethidium bromide by up to 736.3% for NorA and 234.8% for MepA, supporting the inhibition of efflux pumps. Increased bacterial membrane permeability was also observed, evidenced by an increase in SYTOX Green fluorescence by 70–855%. Although the results demonstrate the potential of chalcone as a therapeutic adjuvant, the ADMET analyses revealed toxicological alerts that require further investigation. These findings suggest that rational structural modifications may be necessary to ensure its safety and efficacy in combating resistant bacterial infections.