Chromones from the stems of Cassia fistula and their anti-tobacco mosaic virus activities

Three new chromones, 5-methoxy-2,2-dimethyl-7-(2-oxopropyl)-2,3-dihydrochromen-4-one (1), 5-methoxy- 2,2-dimethyl-8-(2-oxopropyl)-2,3-dihydrochromen-4-one (2), and 1-(3,4-dihydro-5-methoxy- 2,2-dimethyl-2H-chromen-7-yl)propan-2-one (3), together with four known chromones (4-7) were isolated from the stems of Cassia fistula. 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) activities. The results showed that compound 5 exhibited high anti-TMV activity with inhibition rate of 30.8% at a concentration of 20 mu M. The other compounds also exhibited potential anti-TMV activities with inhibition rates in the range of 15.6-22.1% at the same concentration. (C) 2014 Published by Elsevier B.V. on behalf of Phytochemical Society of Europe.