Design, Synthesis and Antibacterial Studies of Novel Cationic Amphipathic Cyclic Undecapeptides and Their Linear Counterparts against Virulent Bacterial Strains

Bacteria have acquired resistance against almost all antibiotics because of the misuse antibacterial agents and long periods treatment. Antimicrobial peptides (AMPs) are one most encouraging candidates to solve this problem, as they possess high prokaryotic selectivity, affect bacteria by a unique mode action. Novel cyclic undecapeptides (QNRNFYFNRNQ QNRNFHFNRNQ) their linear counterparts were investigated for activity virulent strains. The minimal inhibitory concentration (MIC) values showed that tyrosine histidine AMPs promising bacteria. MIC P. aeruginosa PA14, E. coli O157:H7 CR3, S. aureus 209P, B. subtilis ATCC 6633 bacterial strains evaluated peptide containing tyrosine, 6.25, 12.5, 12.5 µM, respectively. Meanwhile, form, 9.3, cyclic-peptide–containing histidines’ 3.1, 3.1 6.25 activities new compared with gentamicin sulfate, relatively higher potencies. Time-inhibition studies demonstrated rapid effects novel AMPs, which more likely be concentration-dependent, rather than time-dependent. At double concentration, tested exhibited stable up 24 h, especially an improved effect.