Isocoumarins from the fermentation products of a plant entophytic fungus <i>Penicillium oxalicum</i>

<div><p>Three new isocoumarins, terrecoumarins A–C (<b>1–3</b>), together with six known isocoumarins (<b>4–9</b>) were isolated from the fermentation products of the fungus <i>Penicillium oxalicum</i> 0403. Their structures were elucidated by spectroscopic methods, including extensive 1D and 2D NMR techniques. The anti-tobacco mosaic virus (anti-TMV) activities of <b>1</b>–<b>9</b> were evaluated. The results revealed that compound <b>1</b> showed high anti-TMV activity with inhibition rate 25.4 ± 3.5%. Other compounds also showed weak activity with inhibition rate in the range of 11.3–18.9%.</p></div>