Metabolization of flavan-3-ol oligomers by human gut bacteria

International audienceFlavan-3-ols are a largely consumed subclass of flavonoids and are involved in the prevention of cardiovascular diseases [1]. The contribution of phenolic metabolites produced by the gut microbiota in the health effects of polyphenols (including flavan-3-ols) is currently an open field of investigation. Although a few bacterial species metabolize flavan-3-ol monomers [2] no bacterial isolates active on oligomers (called procyanidins) have been described. Knowing that the gut microbiota hydrolyzes procyanidins [3], our aim was to identify bacteria degrading flavan-3-ol oligomers and the degradation products. From human stools of three healthy individuals, culturomic approaches combined with screening for the metabolic activity of bacterial isolates by HPLC-DAD allowed us to obtain four strains of Eggerthella lenta and one strain of Flavonifractor plautii degrading (+)-catechin and (-)-epicatechin. The activity of these strains was then tested on B-type (DP2 to 4) and A-type (DP2) procyanidins and the metabolites generated were characterized by LC-ESI-MS / MS. These two species co-metabolized (+)-catechin and (-)-epicatechin into hydroxyphenylvaleric acid derivatives. Only E. lenta converted procyanidins while F. plautii alone or in co-culture with E. lenta did not show any activity towards procyanidins. The reaction catalyzed by E. lenta on dimers (B-type and A-type) corresponded to the opening of the C-ring of the terminal unit. This work is the first report of flavan-3-ol oligomers metabolization by the human gut bacterium E. lenta