Tetrahydropiperic acid (THPA) conjugated cationic hybrid dipeptides as antimicrobial agents.

The present work describes the synthesis of hybrid dipeptides H-Lys-Gpn-PEA, C1; H-Lys-β3,3AC6C-PEA, C2, and THPA conjugated dipeptides, THPA-Lys-Gpn-PEA, C3, and THPA-Lys-β3,3AC6C-PEA, C4. All the peptides were evaluated against both Gram-negative and Gram-positive bacterial strains. Among all, peptide C4 exhibited the most potent activity with MIC 1.56 μM against P. aeruginosa (MTCC 424) and S. aureus (MTCC 737). Further, time-kill kinetics, fluorescence assays, and scanning electron microscopy (SEM) studies were performed in order to understand the mechanism of action and efficacy of peptide C4, The fluorescence assays and SEM images demonstrated the bacterial killing through membrane disruption. The peptide C4 exhibited very low hemolytic activity with negligible cytotoxicity against normal human breast cell line FR2.