Biotransformation of the isoflavonoids biochanin A, formononetin, and glycitein by Eubacterium limosum

Eubacterium limosum (ATCC 8486), a strict anaerobe from the human intestina l tract that is capable of O-demethylation of several compounds, was tested for the ability to metabolize three methoxylated isoflavonoids, biochanin A, formononetin, and glycitein. Highperformance liquid chromatography eluti on profiles of metabolites produced from biochanin A, formononetin, and gly citein showed peaks that had identical retention times to authentic geniste in, daidzein, and 6,7,4'-trihydroxyisoflavone, respectively. The metabolite s were identified, using an on line liquid chromatography-electrospray mass spectrometer. E. limosum produced 61.4 muM of genistein and 13.2 muM of da idzein from 100 muM of biochanin A and formononetin, after 26 days incubati on. O-demethylase activity is cell-associated and was not detected in the e xtracellular fraction of bacterial culture. This is the first study in whic h conversion of biochanin A, and formononetin to more potent phytoestrogens by a bacterium has been shown. (C) 2000 Federation of European Microbiolog ical Societies. Published by Elsevier Science B.V. All rights reserved.