Three novel cyclic hexapeptides from Streptomyces alboflavus 313 and their antibacterial activity

Three novel cyclic hexapeptides, designated NW-G05 (1), NW-G06 (2) and NW-G07 (3), were isolated from the fermentation broth of Streptomyces alboflavus 313. Their structures were elucidated on the basis of extensive spectroscopic analysis, MS experiments, and chemical analysis. Their antibacterial activities against several strains of bacteria were evaluated by micro-broth dilution method. Among these compounds, NW-G06 (2) and NW-G07 (3) displayed highly antibacterial activity against gram-positive bacteria, but not gram negative ones. However, NW-G05 (1) was not active against all tested microorganisms.

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► Three novel cyclic hexapeptides were obtained from S. alboflavus 313.
► NW-G06 (2) and NW-G07 (3) were highly antibacterial against gram-positive bacteria, including methicillin-resistant Staphylococcus aureus.
► NW-G05 (1) was not active to all tested microorganisms.