Flavonoids From the Flowers of Sophora davidii and Their Anti-Tobacco Mosaic Virus Activities

A new pterocarpan, named davidicarpan A (1), together with 9 known flavonoids, including 3 pterocarpans (2-4) and 6 isoflavones (5-10), were isolated from the flowers of Sophora davidii (France.) Pavol. Their structures were confirmed by high-resolution electrospray ionization-mass spectrometry, one-dimensional (1D) and 2D nuclear magnetic resonance spectroscopy, and comparison with reported literature values. Compounds 1 and 4 exhibited anti-tobacco mosaic virus (anti-TMV) activities with inhibition rates of 27.4% and 26.2%, which was higher than that of the positive control, ningnamycin.