Synthesis and antibacterial activity evaluation of octapeptin derivatives / 药学学报

Octapeptin has strong antibacterial activity against Gram-negative bacteria such as Escherichia coli, Klebsiella pneumoniae and Acinetobacter baumannii, while it also has activity against some Gram-positive bacteria. This study used natural octapeptin A3 and B3 as lead compounds for structural modification. Twenty-one peptide derivatives (including A3 and B3) containing eight amino acid residues were prepared by solid-phase synthesis, and evaluated for antibacterial activity and renal cytotoxicity. Among them, three compounds 6, 7 and 17 exhibited broad-spectrum antibacterial activity and significantly enhanced the activity for Gram-positive bacteria while maintaining the activity of Gram-negative bacteria. Several compounds improved the activity for Pseudomonas aeruginosa. Compound 7 was active against all test strains and had relatively low renal cytotoxicity. The results provide a basis for the further development of novel polypeptide antibiotics.

Structure modification and antimicrobial activity of novel cationic melittin analogues / 药学学报

Melittin exhibits high antibacterial potency against drug-resistant bacteria. However, the clinical utility of melittin is limited by its serious hemolytic activity. Thus, the need for developing novel melittin analogues with high antimicrobial activity and low hemolytic activity has grown. We designed, synthesized, and evaluated 20 novel melittin analogues with varying hydrophobic, polar or positively charged amino acids. The results showed that 8 compounds had antimicrobial activity (MIC: 1-4 μg·mL-1) against gram-positive pathogens equal to or better than that of melittin, and 16 compounds had low hemolytic activity (HC50 ≥ 11.9 μg·mL-1). Compounds 13 (MIC: 2-4 μg·mL-1) and 15 (MIC: 1-2 μg·mL-1) showed equal or better antimicrobial activity against both susceptible and resistant strains of Staphylococcus aureus and Enterococcus faecium compared to melittin (MIC: 4 μg·mL-1). Compound 13 (HC50: 24.0 ± 4.3 μg·mL-1) displayed noticeably decreased hemolytic activity compared to melittin (HC50: 5.3 ± 0.4 μg·mL-1). This work established a base for further study on the structure-activity relationships and structure-toxicity relationships of melittin.