Carbazole and Quinazolinone Derivatives from a Fluoride-Tolerant Strain OUCMDZ-5511.

Six new 9-carbazole derivatives (-) and nine previously reported compounds (-) were isolated from a fermented solid medium of the Thailand mangrove-derived strain, OUCMDZ-5511, under fluoride stress. Compounds -, , and were exclusively present in the fluoride-supplemented fermentation medium, while compounds -, , and were newly discovered natural products. The molecular structures of the compounds were identified by a spectroscopic analysis. The new compound displayed antiquorum sensing activity against ATCC 12472 by reducing the violacein production and inhibiting the biofilm formation in a concentration-dependent manner. The study revealed that compound could be a novel potential inhibitor of quorum sensing.