A new dithiolopyrrolone antibiotic triggered by a long fermentation of Saccharothrix algeriensis NRRL B‐24137 in sorbic acid‐amended medium
Résumé
Saccharothrix algeriensis NRRL B‐24137 is an actinobacterium isolated from Algerian Saharan soil. It produces bioactive compounds belonging to the dithiolopyrrolone class of antibiotics, which are characterized by the possession of a unique pyrrolinonodithiole nucleus. Dithiolopyrrolones are known for their strong antibacterial and antifungal activities. This class of antibiotics generated great interest after the discovery of their anticancer properties. In this study, an antibiotic named PR11, produced after a long bacterial fermentation (11 days) in sorbic acid‐containing culture broth, was characterized as a new dithiolopyrrolone derivative. After HPLC analysis and purification, the chemical structure of this antibiotic was determined by 1H‐ and 13C‐nuclear magnetic resonance, mass and UV‐visible data. PR11 was thus characterized as an iso‐hexanoyl‐pyrrothine, a novel dithiolopyrrolone derivative. The minimum inhibitory concentrations of the new induced antibiotic were determined against several pathogenic micro‐organisms. A moderate to strong activity was noted against all Gram‐positive bacteria, filamentous fungi and yeasts tested.
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