Anti-Tobacco Mosaic Virus Isocoumarins from the Fermentation Products of the Endophytic Fungus Aspergillus versicolor

Two new isocoumarins, (3R)-methyl-8-hydroxy-6-(hydroxymethyl)-7-methoxydihydroisocoumarin (1) and (3R)-methyl-7,8-dimethoxy-6-(hydroxymethyl)dihydroisocoumarin (2), together with three known isocoumarins (3–5), were isolated from the fermentation products of an endophytic fungus Aspergillus versicolor. Their structures were elucidated by spectroscopic methods, including extensive 1D and 2D NMR techniques. The anti-tobacco mosaic virus (anti-TMV) activities of compounds 1 and 2 were evaluated. Compounds 1 and 2 showed anti-TMV activities with inhibition rates of 21.8 and 18.6% at the concentration of 20 μM, respectively.