Two New Xanthones from Comastoma pulmonarium and Their Anti-Tobacco Mosaic Virus Activity

Two new xanthones (1 and 2), together with three known xanthones (3–5), were isolated from the whole plants of Comastoma pulmonarium. Their structures were elucidated by spectroscopic methods, including extensive 1D and 2D NMR techniques. Compounds 1 and 2 were also evaluated for their anti-tobacco mosaic virus (anti-TMV) activity. The results showed that compounds 1 and 2 showed high anti-TMV activity with inhibition rates of 42.8% and 52.4%, respectively. These rates are higher than that of positive control.