Accraspiroketides A-B, Phenylnaphthacenoid-Derived Polyketides with Unprecedented [6 + 6+6 + 6] + [5 + 5]...

Area of Science:

• Natural Product Chemistry
• Microbiology
• Synthetic Biology

Background:

• Polyketides are a diverse class of natural products with significant therapeutic potential.
• The discovery of novel polyketides with unique structures is crucial for developing new antimicrobial agents.
• Streptomyces species are a rich source of bioactive secondary metabolites.

Purpose of the Study:

• To isolate and characterize novel polyketides from a Streptomyces MA37 ΔaccJ mutant strain.
• To evaluate the antimicrobial activity of the isolated compounds against Gram-positive bacteria.
• To investigate the potential of these novel compounds as alternatives to existing antibiotics.

Main Methods:

• Isolation and purification of compounds using chromatographic techniques.
• Structure elucidation of novel polyketides using spectroscopic methods (NMR, MS).
• Determination of minimum inhibitory concentrations (MIC) against various bacterial strains.

Main Results:

• Two new polyketides, accraspiroketides A (1) and B (2), with unprecedented spiro architectures were identified.
• Compounds 1 and 2 demonstrated potent activity against Gram-positive bacteria, with MIC values ranging from 1.5-6.3 μg/mL.
• Accraspiroketides A and B showed superior efficacy against a clinically isolated Enterococcus faecium strain compared to ampicillin.

Conclusions:

• Accraspiroketides A and B represent a novel class of polyketides with significant antimicrobial properties.
• The unique spiro chemical architecture may contribute to their potent bioactivity.
• These findings highlight the potential of exploring microbial mutants for the discovery of new antibacterial agents.