Antiviral anthraquinones and azaphilones produced by an endophytic fungus Nigrospora sp. from Aconitum carmichaeli.

A new hydroanthraquinone derivative, 6-O-demethyl-4-dehydroxyaltersolanol A (1), and two new azaphilones, 8,11-didehydrochermesinone B (6) and (7S)-7-hydroxy-3,7-dimethyl-isochromene-6,8-dione (8), along with five known analogues (2-5 and 7), were isolated from the culture broth of Nigrospora sp. YE3033, an endophytic fungus obtained from Aconitum carmichaeli. Their structures were elucidated on the basis of spectroscopic analyses. Biological activity test indicated that compounds 1-3, and 7 exhibited the inhibitory effects on influenza viral strain of A/Puerto Rico/8/34 (H1N1) with the IC50 values of 2.59, 8.35, 7.82, and 0.80μg/mL, respectively, while the low cytotoxicity of 7 with the CC50 value of 184.75μg/mL, displaying a promising potential of 7 in the development of anti-influenza A virus drugs.