Structures and antipathogenic fungi activities of flavonoids from pathogen-infected Astragalus adsurgens

Healthy Astragalus adsurgens is a highly palatable forage widely cultivated in arid areas of north China, while pathogen- (Embellisia asttrgali ) infected A. adsurgens is poisonous forage and often causes disastrous livestock losses. A phytochemical investigation was carried out on the E. asttrgali-infected A. adsurgens; as a result, a new compound, (2R, 3S)-7,4′-dimethoxy-2′-hydroxyflavanol (1), together with nine known flavonoids was obtained. It was found that the content of most of these compounds in E. asttrgali-infected A. adsurgens was higher than that in healthy A. adsurgens. Moreover, compounds 2 and 3 exhibited weak inhibitory activity against Fusarium graminearum and E. asttrgali with EC50 over 100 μg/mL, and showed moderate inhibitory activity against Bipolaris sorokinianum with EC50 of 39.1 and 95.0 μg/mL. Compounds 1–4 exhibited a high degree of inhibitory activity against Curvularia lunata, with 21.73, 43.93, 45.02 and 44.51% inhibition ratio at concentration of 50 μg/mL.