Isoflavonoid Phytoalexins of Yam Bean (Pachyrrhizus erosus)

Leguminosae, Pachyrrhizus, Isoflavonoids, Pterocarpans, Phytoalexins The furanopterocarpan, neodunol, has been isolated as a major phytoalexin from the fungusinoculated stems o f Pachyrrhizus erosus. Neodunol is accompanied by small quantities o f demethylmedicarpin and a third compound provisionally identified as the prenylated pterocarpan, homoedudiol; traces o f a neodunol isomer were also isolated from P. erosus although its precise struc­ ture could not be determined. The apparently close chemical relationship between Pachyrrhizus and Neorautanenia is discussed in the light o f a recent study which allocates these genera to differ­ ent sections o f the legume tribe Phaseoleae.