Two New Isoquinoline Alkaloids from the Barks of Cassia fistula and Their Anti-Tobacco Mosaic Virus Activity

Two new isoquinoline alkaloids, fistulaquinolines A and B ( 1 and 2 ), were isolated from the barks of Cassia fistula. Their structures were determined by means of HR-ESI-MS and extensive 1D and 2D NMR spectroscopic studies. Compounds 1 and 2 were tested for their anti-tobacco mosaic virus (anti-TMV) activity. The results showed that the two compounds showed weak anti-TMV activity with inhibition rates of 18.9 and 22.6%.