Prenylated isoflavanone from the roots of Erythrina sigmoidea.

A novel prenylated isoflavanone, sigmoidin I, has been isolated from the roots of Erythrina sigmoidea, in addition to the known isoflavones, corylin and neobavaisoflavone and the known pterocarpan, phaseollidin. Its structure was established as 7,4'-dihydroxy-3'-methoxy-5'-(3-methylbut-2-enyl) isoflavanone by means of spectroscopic analyses and chemical transformations. Neobavaisoflavone displayed antifungal potency in vitro with minimum inhibitory concentrations against Aspergillus fumigatus and Cryptococcus neoformans, of 50 mg ml-1.