Assessing the Gut Microbiota's Ability to Metabolize Oligomeric and Polymeric Flavan-3-ols from Aronia and Cranberry

Clinical trials investigating the health effects of flavan-3-ols yield heterogeneous results due to interindividual variability in the gut microbiota metabolism. In fact, different groups in the population have similar metabolic profiles following (-)-epicatechin and (+)-catechin gut microbial metabolism and can be regrouped into so-called metabotypes. In this study, the capacity of 34 donors to metabolize polymeric B-type flavan-3-ols from aronia and oligomeric A-type flavan-3-ols from cranberry is investigated by in vitro fecal batch fermentations. Less than 1% of the flavan-3-ols from both sources are converted into microbial metabolites, such as phenyl-γ-valerolactones (PVLs). To further confirm this result, gut microbial metabolites from flavan-3-ols are quantified in urine samples collected from participants, before and after a 4-day supplementation of cranberry extract providing 82.3 mg of flavan-3-ols per day. No significant difference is observed in the urinary excretion of flavan-3-ols microbial metabolites. Hence, it demonstrates by both in vitro and in vivo approaches that flavan-3-ols from aronia and cranberry are poorly degraded by the gut microbiota. The beneficial health impacts of these molecules likely stem from their capacity to affect gut microbiota and their interactions with the gut epithelium, rather than from their breakdown into smaller metabolites.