Griseofulvin enantiomers and bromine-containing griseofulvin derivatives with antifungal activity produced by the mangrove endophytic fungus sp. QQYB1.

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Marine microorganisms have long been recognized as potential sources for drug discovery. Griseofulvin was one of the first antifungal natural products and has been used as an antifungal agent for decades. In this study, 12 new griseofulvin derivatives [(±)--, (+)-, (±)-, -, and -] and two new griseofulvin natural products ( and ) together with six known analogues [(-)-, -, and ] were isolated from the mangrove-derived fungus sp. QQYB1 treated with 0.3% NaCl or 2% NaBr in rice solid medium. Their 2D structures and absolute configurations were established by extensive spectroscopic analysis (1D and 2D NMR, HRESIMS), ECD spectra, computational calculation, DP4 + analysis, and X-ray single-crystal diffraction. Compounds - represent the first griseofulvin enantiomers with four absolute configurations (2, 6'; 2, 6'; 2, 6'; 2, 6'), and compounds - represent the first successful production of brominated griseofulvin derivatives from fungi via the addition of NaBr to the culture medium. In the antifungal assays, compounds and demonstrated significant inhibitory activities against the fungi , , and with inhibition zones varying between 28 and 41 mm (10 μg/disc). The structure-activity relationship (SAR) was analyzed, which showed that substituents at C-6, C-7, C-6' and the positions of the carbonyl and double bond of griseofulvin derivatives significantly affected the antifungal activity.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s42995-023-00210-0.