Three new cyclotetrapeptides isolated from Streptomyces sp. 447

Area of Science:

• Microbiology
• Natural Products Chemistry
• Biochemistry

Background:

• Endophytic actinobacteria, particularly Streptomyces species, are a rich source of novel bioactive compounds.
• Cyclotetrapeptides represent a class of cyclic peptides with diverse biological activities.
• The discovery of new natural products is crucial for drug development.

Purpose of the Study:

• To isolate and characterize new cyclotetrapeptides from an endophytic Streptomyces strain.
• To elucidate the chemical structures and absolute configurations of the isolated compounds.
• To evaluate the antimicrobial activities of the novel cyclotetrapeptides.

Main Methods:

• Isolation of cyclotetrapeptides using chromatographic techniques.
• Structure elucidation via 1D and 2D Nuclear Magnetic Resonance (NMR) spectroscopy and mass spectrometry.
• Determination of amino acid absolute configuration through hydrolysis, derivatization, and Gas Chromatography-Mass Spectrometry (GC-MS).
• Antimicrobial activity screening.

Main Results:

• Three new cyclotetrapeptides, cyclo-(L-Leu-L-Glu-L-Leu-L-Glu) (1), cyclo-(L-Ile-L-Glu-L-Ile-L-Glu) (2), and cyclo-(L-Val-L-Glu-L-Val-L-Glu) (3), were isolated.
• The structures and absolute configurations of the three cyclotetrapeptides were successfully determined.
• The producer strain was identified as Streptomyces sp. through 16S rDNA sequencing.

Conclusions:

• The study successfully identified and characterized three novel cyclotetrapeptides from an endophytic Streptomyces isolate.
• The findings contribute to the understanding of cyclotetrapeptide diversity in microbial natural products.
• Further investigation into the antimicrobial potential of these compounds is warranted.