Design, synthesis and antibacterial evaluation of novel unsaturated butenolide-fatty amine hybrids against multidrug-resistant pathogens

To address the growing public health challenge of multidrug-resistant Bacterial infections, 26 new butenolide amides bearing fatty chains of different lengths (C_nH_2n+1, n = 4-16) were designed and synthesized and evaluated for their Antibacterial activity. The Antibacterial activities of the derivatives were evaluted against four clinically common pathogens, Acinetobacter baumannii ATCC 19606(A. baumannii), Klebsiella pneumoniae ATCC 13883(K. pneumoniae), Pseudomonas aeruginosa ATCC 15442(P. aeruginosa) and methicillin-resistant Staphylococcus aureus ATCC 43300(MRSA 43300). The results indicated that derivative 17j, with a 13‑carbon fatty chain, exhibited prominent Antibacterial activity, with MIC values of 0.25 μg/mL against A. baumannii and K. pneumoniae, 0.125 μg/mL against P. aeruginosa, and 1 μg/mL against MRSA 43300. The Antibacterial activity of 17j against A. baumannii, K. pneumoniae and P. aeruginosa was approximately 64-fold higher than of that of kanamycin, while its activity against MRSA 43300 was close to that of vancomycin. Structure-activity relationship analysis revealed that the length of the fatty chain is a crucial determinant that impacts Antibacterial activity. Cytotoxicity and hemolysis assays revealed that 17j exhibited very low toxicity toward mammalian cells (Beas-2B, SMMC-7721, MCF7) and red blood cells. The in vivo Antibacterial activity of compound 17j was evaluated using the Galleria mellonella larval Infection model, in which 17j showed better Antibacterial activity than kanamycin. Scanning electron microscopy (SEM) analysis revealed that the likely mechanism of action involves the disruption of Bacterial membrane integrity, leading to Cell Lysis and death. This research provides promising lead compounds for the development of Antibacterial drugs targeting drug-resistant bacteria.