Isoflavanones from the allelopathicaqueousrootexudate of Desmodiumuncinatum

Abstract

Three isoflavanones, 5,7,2′,4′-tetrahydroxy-6-(3-methylbut-2-enyl)isoflavanone (1), 4″,5″-dihydro-5,2′,4′-trihydroxy-5″-isopropenylfurano-(2″,3″;7,6)-isoflavanone (2) and 4″,5″-dihydro-2′-methoxy-5,4′-dihydroxy-5″-isopropenylfurano-(2″,3″;7,6)-isoflavanone (3) and a previously known isoflavone 5,7,4′-trihydroxyisoflavone [genistein (4)] were isolated and characterised spectroscopically from the rootexudate of the legume Desmodiumuncinatum (Jacq.) DC. We propose the names uncinanone A, B, and C for compounds 1, 2 and 3, respectively. Isolated fractions containing uncinanone B (2) induced germination of seeds from the parasitic weed Striga hermonthica (Del.) Benth. and fractions containing uncinanone C (3) moderately inhibited radical growth, the first example of a newly identified potential allelopathic mechanism to prevent S. hermonthica parasitism.

Three isoflavanones, including the two shown were isolated and characterised spectroscopically from the rootexudate of the legume Desmodiumuncinatum (Jacq.) DC. Isolated fractions containing isoflavanone (R=H) induced germination of seeds from the parasitic weed Striga hermonthica (Del.) Benth and fractions containing the isoflavanone (R=Me) moderately inhibited radical growth, the first example of a newly identified potential allelopathic mechanism to prevent S. hermonthica parasitism.