Dimeric Phthalides from an endophytic fungus Phomopsis sp. of Aconitum carmichaeli

Three racemic pairs of new dimeric phthalides, (±)-phomophthalides A-C ((±)-1-3), together with eight known compounds (4-11), were obtained from the culture broth of the endophytic fungus Phomopsis sp. YM 355364 isolated from the medicinal plant Aconitum carmichaeli. The chemical structures of the new compounds were established by extensive NMR spectroscopic and HRESI-MS analysis and DP4+ calculations. The new compounds were tested for their antimicrobial activities by broth microdilution method. Compound 1 showed moderate inhibitory activity toward three pathogenic fungal strains Fusarium solani, Candida albicans, and Botrytis cinerea with MIC values of 16, 32, and 32 μg/mL, respectively. Compound 2 exhibited antifungal activity against B. cinerea and C. albicans with MIC values of 16 and 32 μg/mL, respectively.