Isochromenes from the Nicotiana tabacum-Derived Endophytic Fungus Aspergillus versicolor and Their Bioactivities

Two new isochromenes, 5-methoxy-3-methyl-7-prenyl-1H-isochromene (1) and 7-(3-hydroxypropyl)-5-methoxy-3-methyl-1H-isochromene (2), along with four known ones (3-6) were isolated from the fermentation products of the Nicotiana tabacum-derived endophytic fungus Aspergillus versicolor. Their structures were elucidated by spectroscopic methods, including extensive 1D and 2D NMR techniques. Compounds 1 and 2 were evaluated for their anti-tobacco mosaic virus (anti-TMV) and anti-methicillin-resistant Staphylococcus aureus (anti-MRSA) activities. The results showed that compounds 1 and 2 exhibited potential anti-TMV activities with inhibition rates of 36.5 and 42.2%, respectively, and also showed good anti-MRSA activities with IZD of 16.8 +/- 2.2 and 20.6 +/- 2.5 mm, respectively.