Three new flavones from the whole plants of Cassia auriculata Linn. and their antiviral activities

Cassia auriculata, a widely grown medicinal plant in China, has not been fully studied in terms of its secondary metabolites. In our pursuit of new bioactive metabolites from Cassia plants, we conducted a phytochemical reinvestigation on C. auriculata. This investigation resulted in the isolation of three new (1-3) and six known (4-9) flavones. Their structures were elucidated by spectroscopic methods, including extensive 1D-and D-2 NMR techniques. Interestingly, Compounds 1-3 are rare flavones bearing an unusual (4-methylfuran-2-yl)methyl moiety. In addition, Compounds 1-3 were evaluated for their anti-tobacco mosaic virus (anti-TMV) activities. The results showed that Compounds 1-3 exhibited potential anti-TMV activities with inhibition rates of 26.8%, 30.5% and 34.6% at a concentration of 20 mu M, respectively, and these rates are close to that of the positive control. Compounds 1-9 were also tested for their anti-rotavirus activities. The results revealed that 1-9 exhibited potential anti-rotavirus activity with therapeutic index (TI) values in the range of 13.3-20.8. These values are lower than that of the positive control (with a therapeutic index of 23.4).