Five previously undescribed citrinin derivatives from the endophytic fungus Penicillium citrinum GZWMJZ-836

Abstract

Penicillium citrinum GZWMJZ-836 is an endophytic fungus from Drynaria roosii Nakaike. Five previously undescribed citrinin derivatives (1–5) and six intermediates related to their biosynthesis (6–11) were obtained from the extract of this strain's solid fermentation using multiple column chromatography separations, including high-performance liquid chromatography. The structures of these compounds were determined through comprehensive spectroscopic analyses, primarily using NMR and HRESIMS data. The stereochemistry was mainly confirmed by ECD calculations, and the configurations of C-7′ in compounds 4 and 5 were determined using 13C NMR calculations. Compounds 4–5 and 8 showed antibacterial activity against five strains, with minimum inhibitory concentration values ranging from 7.8 to 125 μM. Compounds 4 and 7 exhibited inhibitions against three plant pathogenic fungi, with IC50 values ranging from 66.6 to 152.1 μM. Additionally, a putative biosynthetic pathway for compounds 1–5 derived from citrinin was proposed.