Structural optimization of natural product honokiol to discover novel membrane-targeting antibacterial agents against Gram-positive bacteria

The global increase in infections caused by multidrug-resistant bacteria, coupled with a dwindling antibiotic pipeline, underscores an urgent need for new therapeutic agents. Inspired by the design principles of cationic antimicrobial peptides, we developed a new class of honokiol-based amphiphiles. From this series, compound 20C emerged as a promising lead, demonstrating potent in vitro activity against Gram-positive bacteria (MICs = 0.5-2 μg/mL). It exhibited a favorable safety profile characterized by low hemolytic (HC₅₀ = 771.8 μg/mL) and cytotoxic activity (CC₅₀ = 28.03 μg/mL), along with good plasma stability. 20C also displayed rapid bactericidal kinetics, a low resistance frequency, and efficacy in inhibiting biofilm formation and disrupting mature biofilms. A detailed mechanistic investigation established that 20C exerted its effect by dissipation of membrane potential, increasing permeability, thereby disrupting membrane integrity. This primary membrane damage triggered secondary lethal events, including ROS accumulation and leakage of proteins and DNA. Notably, 20C displayed superior efficacy compared to vancomycin in an in vivo infection model. These findings established 20C as a promising candidate and underscore the potential of this amphiphilic design strategy in antibiotic discovery.