Flavones from Cassia siamea and their anti-tobacco mosaic virus activity

Two new flavones, siameflavones A and B (1 and 2), together with five known flavones (3–7) were isolated from the stem of Cassia siamea. Their structures were elucidated by spectroscopic methods including extensive 1D and 2D NMR techniques. Compounds 1–5 were evaluated for their anti-tobacco mosaic virus (Anti-TMV) activity. The results showed that compounds 1–5 showed weak anti-TMV activity with inhibition rates in the range of 11.6–18.5%.