LAUSR

BACKGROUND Natural products are important sources of biopesticides to control plant virus, and flavonoids are identified as promising ant-TMV agents. Since Desmodium caudatum is a rich sources of flavonoids, this study focuses to the discovery of the new anti-TMV active flavonoids from D. caudatum and their possible mode of action. RESULTS Three new (1-3) and nine known (4-12) C-alkylated flavonoids were isolated from D. caudatum. To 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 increased 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 are involved in tobacco resistance to TMV. By above actions, the infection of TMV was influenced, thereby achieving the effects of control TMV. The successful isolation of the above flavonoids provide the new source of biopesticides to TMV proliferation, and also contribute to the utilization of D. caudatum. This article is protected by copyright. All rights reserved.