Rational design and synthesis of potent active antimicrobial peptides based on American oyster defensin analogue A3†

The rise of drug-resistant microbes is increasingly recognized as a significant global health challenge. Microbial drug resistance diminishes the efficacy of existing treatment options, underscoring the urgent necessity for the development of novel antibiotic candidates to effectively address infections. Antimicrobial peptides, owing to their distinctive antibacterial mechanisms, are considered a promising alternative to conventional antibiotics. In this work, we modified the structure of the American oyster defensin (AOD) analogue A3 to obtain four novel antimicrobial peptides (D-A3, A3-C4, A3-C5, A3-C6). These synthesized peptides exhibited broad-spectrum antibacterial activity. Notably, it was demonstrated that A3-C4, A3-C5, and A3-C6 showed enhanced glutathione (GSH) stability compared to A3, while D-A3 exhibited superior protease stability. Importantly, none of the peptides displayed hemolytic toxicity. Mechanistic investigations suggested that the synthesized peptides exert their anti-bacterial effects primarily through membrane disruption. D-A3 and A3-C6 were peptides with the best antibacterial activity and enzymatic stability among the synthesized derived peptides. These studies of D-A3 and A3-C6 will contribute to the development of new candidate drugs for the treatment of microbial infections.