Antifungal Activities of Isoflavonoids from Uromyces striatus Infected Alfalfa.

Fungal pathogens constitute a severe yield-limiting factor for the pasture crop alfalfa (Medicago sativa L.). Eleven phenolic compounds, including a new isoflavane, were isolated from the Uromyces striatus Schroet. infected alfalfa. The effect of infection with U. striatus Schroet. on the phytochemical profile of alfalfa was investigated using ultra-performance liquid chromatography (UPLC), and the antifungal properties of isolated compounds against a range of pathogens were tested. It was found that the contents of most of the isolated compounds in U. striatus infected alfalfa were higher than those in healthy alfalfa. Compounds 1-5 exhibited a moderate inhibitory activity against Curvularia lunata with 40.14±1.63 %, 48.03±1.22 %, 57.54±1.18 %, 50.10±1.56 %, and 61.54±2.14 % inhibition ratio at the concentration of 50 μg/mL. Compounds 3 and 5 showed a weak inhibitory activity against Fusarium graminearum with the EC values of 104.2±2.66 and 123.0±1.23 μg/mL, and a moderate inhibitory activity against Bipolaris sorokinianum with the EC values of 39.1±2.05 and 95.0±1.01 μg/mL, respectively. In pot experiments with wheat, compounds 1-5 possessed desirable protective efficacy of over 80 % and curative effectiveness of over 50 % against Puccinia striiformis f. sp. tritici at a concentration of 0.5 mg/mL.