Antiviral butyrolactones from the endophytic fungus Aspergillus versicolor.

Versicolactones A-D (1-4), four new butyrolactones, along with four known butyrolactones (5-8) were isolated from the fermentation products of the endophytic fungus Aspergillus versicolor. The structures of compounds 1-4, including absolute configuration, were elucidated by interpretation of the NMR and CD data. Compound 2 was further confirmed by single-crystal X-ray diffraction analysis. In particular, compound 1 is the first naturally occurring butyrolactone possessing an unusual 2-oxopropyl group. More importantly, compounds 1 and 8 displayed significant antitobacco mosaic virus activities with inhibition rates of 46.4 % and 35.4 %, even more potent than the positive control ningnanmycin (30.8 %). Compound 1 also showed moderate cytotoxicity against A549 and MCF7 cells with IC50 values of 3.2 and 2.5 µM, respectively.