Structures and antipathogenic fungi activities of flavonoids from pathogen-infected <i>Astragalus adsurgens</i>

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