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

Eubacterium limosum (ATCC 8486), a strict anaerobe from the human intestinal 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 elution profiles of metabolites produced from biochanin A, formononetin, and glycitein showed peaks that had identical retention times to authentic genistein, daidzein, and 6,7,4'-trihydroxyisoflavone, respectively. The metabolites were identified, using an on line liquid chromatography-electrospray mass spectrometer. E. limosum produced 61.4 muM of genistein and 13.2 muM of daidzein from 100 muM of biochanin A and formononetin, after 26 days incubation. O-demethylase activity is cell-associated and was not detected in the extracellular fraction of bacterial culture. This is the first study in which conversion of biochanin A, and formononetin to more potent phytoestrogens by a bacterium has been shown. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.