Transformation of plant isoflavones into bioactive isoflavones by lactic acid bacteria and bifidobacteria

Isoflavones are usually found in nature in their glycosilated or methylated forms, and should be hydrolysed to become bioavailable and physiologically active. The deglycosylation of isoflavone C-glycosides and O-glycosides and the demethylase activity were studied in a selection of lactic acid bacteria (LAB) and bifidobacteria by assessing the degree of transformation of the pure precursor compounds, daidzin, genistin, puerarin, formononetin and biochanin A into daidzein or genistein. Only one Bifidobacterium strain and two Enterococcus strains hydrolysed the C-glycosidic bond of puerarin, while deglycosylation of O-glycosides daidzin and genistin was observed in all the tested strains. Demethylation of biochanin A and formononetin was observed in the most of LAB and bifidobacteria. Besides, the subsequent metabolites dihydrodaidzein and dihydrogenistein where produced by many of the strains via daidzein and genistein. In this work, we show the potential of LAB and bifidobacteria as part of functional foods because of their ability to transform plant isoflavones into their bioactive forms.