C-Alkylated flavonoids from the whole plants of Desmodium caudatum and their anti-TMV activity

BACKGROUND

Natural products are important sources of biopesticides to control plant virus, and flavonoids are identified as promising anti-tobacco mosaic virus (TMV) agents. Since Desmodium caudatum is a rich source of flavonoids, this study focuses on the discovery of the new anti-TMV active flavonoids from D. caudatum and their possible mode of action.

RESULTS

Three new (compounds 1-3) and nine known (compounds 4-12) C-alkylated flavonoids were isolated from D. caudatum. To the best of our knowledge, the framework of 1-3 was reported in natural products for the first time. In addition, 1-3, 5, and 6 showed notable anti-TMV activity with inhibition rates in the range of 35.8-64.3% at a concentration of 50 μg/mL, and these rates are higher than that of positive control (with inhibition rates of 34.6% ± 2.8). In addition, the structure-activity relationship study revealed that the (pyrrol-2-yl)methyl moiety on flavone can significantly increases the activity. This result is helpful to find new anti-TMV inhibitors.

CONCLUSION

C-Alkylated flavonoids showed potent activities against TMV with multiple modes of actions. The increase of defense-related enzyme activities, up-regulate the expression of defense related genes, down-regulate the expression of Hsp70 protein by inhibiting the related Hsp genes that are involved in tobacco resistance to TMV. By the actions mentioned earlier, the infection of TMV was influenced, thereby achieving the effects of control of TMV. The successful isolation of the earlier-mentioned flavonoids provide the new source of biopesticides to TMV proliferation, and also contribute to the utilization of D. caudatum. © 2023 Society of Chemical Industry.

Three new isobenzofurans from the roots of Nicotiana Tabacum and their bioactivities

Three new isobenzofurans (1-3), together with four known phenylpropanoids (4-7) were isolated from the roots of Nicotiana tabacum. Their structures were determined by means of HRESIMS and extensive 1D and 2D NMR spectroscopic studies. Compounds 1-6 were tested for their anti-tobacco mosaic virus (anti-TMV) activities and cytotoxicity activities. The results showed that compounds 5 and 6 exhibited high anti-TMV activities with inhibition rates of 35.1 and 33.4%, respectively. The cytotoxicities of compounds 1-7 against five human tumor cell lines (NB4, A549, SHSY5Y, PC3 were also tested. Compounds 1-7 showed weak inhibitory activities against some tested human tumor cell lines with IC50 values in the range of 3.8-9.6 μM.