Butyrolactones from the Endophytic Fungus Aspergillus versicolor and their Anti-Tobacco Mosaic Virus Activity

New butyrolactones aspernolides C and D, along with two known butyrolactones (A and B) were isolated from the culture of the endophytic fungus Aspergillus versicolor. Their structures were elucidated on the basis of extensive spectroscopic analysis, including 1D and 2D nuclear magnetic ressonance techniques, and electronic circular dichroism. The butyrolactones aspernolides C and D were tested for their anti-tobacco mosaic virus activity. The results showed that butyrolactones aspernolides C and D exhibited moderate anti-tobacco mosaic virus activity with IC50 values of 64.2 and 88.6 μM, respectively.