An optimized 2,2′-dipicolylamine-rutaecarpine quaternary ammonium derivative: targeting bacterial membrane disruption for enhanced anti-methicillin-resistant Staphylococcus aureus (MRSA) activity

The escalating threat of antibiotic resistance necessitates innovative strategies to combat multidrug-resistant pathogens. Herein, we reported the rational design of amphiphilic rutaecarpine derivatives through structural modular optimization, aiming to enhance antibacterial efficacy. A quaternary ammonium derivative IV4, bearing a 2,2′-dipicolylamine group, was found to be the most potent candidate, exhibiting remarkable activity against methicillin-resistant Staphylococcus aureus (MRSA) with MIC values of 2–4 μg/mL, demonstrated rapid bactericidal kinetics, effective biofilm eradication, and exceptional plasma stability. Its superior selectivity was evidenced by low hemolytic activity (HC₅₀ > 640 μg/mL) and minimal cytotoxicity toward mammalian cells. In a murine skin infection model, IV4 outperformed vancomycin in reducing bacterial load and attenuating inflammation without systemic toxicity, highlighting its strong therapeutic potential and favorable safety profile. Mechanistic studies revealed that IV4 specifically binds to phosphatidylglycerol (PG) on bacterial membranes, leading to membrane disruption, excessive production of reactive oxygen species (ROS), and metabolic collapse, ultimately resulting in bacterial cell death. Collectively, these findings establish IV4 as a promising membrane-targeting antibacterial agent that combines potent anti-MRSA activity with favorable biosafety, offering a novel framework for addressing antimicrobial resistance.