Antifungal xanthones produced by the endophytic fungus Paraconionthyrium sp. YM 311593.

During our investigation on the endophytic fungi of Azadirachta indica, the strain YM 311593 was obtained from the fruit of the plant. The culture extract of the strain showed antifungal activities against four phytopathogenic fungi. Based on the morphological features and phylogenetic definition, the strain YM 311593 was identified as Paraconiothyrium sp. Four xanthones and one anthraquinone were obtained from the extract of the fermentation broth of the strain. They were characterized to be globosuxanthone A (1), vertixanthone (2), hydroxyvertixanthone (3), 3,8-dihydroxy-1-methy1-9H- xanthen-9-one (4), and danthron (5), respectively, by spectroscopic elucidation. Furthermore, the absolute configuration of 1 was deduced by X-ray diffraction analysis. Besides, compound 4 was firstly found from natural sources. The antifungal activities of compounds 1-5 towards four phytopathogens were assayed using broth microdilution method. Among them, globosuxanthone A (1) showed obvious antifungal activity towards Fusarium graminearum, Fusarium solani, and Botrytis cinerea with MIC values of 4, 8, and 16 μg/mL, respectively.