Isoflavanones from the Stem of Cassia siamea and Their Anti-tobacco Mosaic Virus Activities

Isoflavanones from the Stem of Cassia siamea and Their Anti-tobacco Mosaic Virus Activities

Two new isoflavanones, (3R) 7,2',4'-trihydroxy-3'-methoxy-5-methoxycarbonyl-isoflavanone (1) and (3R) 7,2'-dihydroxy-3',4'-dimethoxy-5-methoxycarbonyl-isoflavanone (2), together with six known isoflavanones (3-8), were isolated from the stems of Cassia siamea. The structure of 1-8 was elucidated by spectroscopic methods including extensive 1D- and 2D-NMR techniques. Compounds 1, 2, 5-8 were evaluated for their anti-tobacco mosaic virus (Anti-TMV) activity. The results showed that compounds 1 and 6 showed potential anti-TMV activity with inhibition rates of 24.6% and 26.9%, respectively. Compounds 2, 5, 7, 8 also showed anti-TMV activity with inhibition rates in the range of 11.8-18.6%.