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The human intestinal microbiota may influence the fate of bioactive polyphenols, such as the isoflavone puerarin (daidzein 8-C-glucoside), following their oral intake. Faecal suspensions from 19 healthy subjects were tested for their ability toC-deglycosylate puerarin. Only one of these catalysed this reaction. A rod-shaped Gram-positive bacterium, strain CG19-1, capable of deglycosylating puerarin to daidzein was isolated from the corresponding suspension. However, the strictly anaerobic isolate was unable to utilize puerarin as sole carbon and energy source nor any of the tested carbohydrates. Comparative 16S rRNA gene sequence analysis indicated that strain CG19-1 is a new species of theLachnospiraceae. Strain CG19-1 also converted other aromaticC-glucosides in addition to puerarin. The xanthoneC-glucoside mangiferin was deglycosylated to norathyriol. The flavoneC-glucosides homoorientin and vitexin were degraded to 3-(3,4-dihydroxyphenyl)propionic acid via luteolin and 3-(4-hydroxyphenyl)propionic acid respectively. In addition, strain CG19-1 converted flavonoidO-glucosides, but at rates that were lower than those of theC-glucosides tested. The isolate deglycosylated the isoflavoneO-glucosides daidzin and genistin to daidzein and genistein respectively. SeveralO-glucosides of the flavones luteolin and apigenin undergoing deglycosylation were subsequently cleaved to 3-(3,4-dihydroxyphenyl)propionic acid and 3-(4-hydroxyphenyl)propionic acid respectively. Moreover, strain CG19-1 cleaved bothO-desmethylangolensin and 6′-hydroxy-O-desmethylangolensin to yield 2-(4-dihydroxyphenyl)propionic acid. The corresponding cleavage product, resorcinol, was only observed forO-desmethylangolensin.