Three new isoflavones from the Pueraria montana var. lobata (Willd.) and their bioactivities.

Three new isoflavones, 7-acetyl-4',6-dimethoxy-isoflavone (1), 7-acetyl-4'-hydroxy-6-methoxy-isoflavone (2) and 7-acetyl-6,8-dimethoxy-4'-hydroxy-isoflavone (3), together with five known flavones (4-8), were isolated from the Pueraria montana var. lobata (Willd.). Their structures were elucidated by spectroscopic methods, including extensive 1D- and 2D NMR techniques. Compounds 1-8 were evaluated for their anti-tobacco mosaic virus (anti-TMV) activities. The results showed that compounds 1 and 2 exhibited high anti-TMV activities with inhibition rates of 36.8 and 33.6%, respectively. The inhibition rates are higher than that of positive control. The other compounds also showed potential anti-TMV activities with inhibition rates in the range of 21.8~28.4%, respectively. The cytotoxicities of compounds 1-3 against five human tumour cell lines (NB4, A549, SHSY5Y, PC3 and MCF7) were also tested. The results revealed that compounds 1-3 showed weak inhibitory activities against some tested human tumour cell lines with IC50 values in the range of 1.2-3.6 μM.