Discovery of Brominated Alboflavusins With Anti-MRSA Activities

Area of Science:

• Microbiology
• Natural Products Chemistry
• Medicinal Chemistry

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant global health threat, necessitating the development of novel antibiotics.
• Alboflavusins (AFNs) are a class of halogenated cyclohexapeptides known to possess anti-MRSA properties.

Purpose of the Study:

• To isolate and characterize novel brominated and dehalogenated alboflavusin congeners.
• To evaluate the anti-MRSA activities of these AFN congeners and elucidate the role of halogenation in their bioactivity.

Main Methods:

• Fermentation of wild-type and genetically modified Streptomyces alboflavus strains (including a strain with inactivated tryptophan halogenase gene afnX).
• Isolation and structural elucidation of AFN congeners using NMR and MS analyses.
• Assessment of anti-MRSA activities against various MRSA strains.

Main Results:

• Two novel brominated AFN congeners (compounds 1 and 2) were isolated from NaBr-supplemented fermentation.
• Two new and one known dehalogenated AFN congeners (compounds 3, 4, and 5) were isolated from the S. alboflavus ΔafnX mutant.
• Brominated compounds 1 and 2 exhibited effective anti-MRSA activities, with compound 2 showing particularly good activity.
• Dehalogenated compounds 3, 4, and 5 displayed weak anti-MRSA activities, highlighting the importance of halogen substitution.

Conclusions:

• Halogenation significantly enhances the anti-MRSA bioactivity of alboflavusins.
• Novel brominated AFNs, particularly compound 2, represent promising candidates for the development of new antibiotics against MRSA infections.