Application of an in vitro digestion model to study the bioaccessibility and the effect of the intestinal microbiota on the red wine proanthocyanidins

Proanthocyanidins are important phenolic fraction for wine quality, contributing to astringency, bitterness and color. Their metabolism begins in the mouth and continues throughout the gastrointestinal tract; however, most of them are accumulated in the colon where are metabolized by the intestinal microbiota, giving rise to a whole series of phenolic acids that may have greater activity at physiological level than the precursors[1]. This study aimed to evaluate in vitro the bioaccessibility of proanthocyanidins in a red wine developed by Bodegas Pradorey, as well as to evaluate the potential effect of intestinal microbiota on polyphenols metabolism identifying and quantifying secondary metabolites. The evaluation of the effects of the intestinal microbiota was carried out using an in vitro Digester of Colonic Fermentation. The fecal microbiota was inoculated, and 100 mL of red wine was added daily for 14 days. For the determination of proanthocyanidins and phenolic metabolites, related, high performance liquid chromatography coupled with mass spectrometry (UHPLC-QqQ-MS/MS) was used. The major phenolic metabolites detected were propionic and acetic acid, and the highest concentrations were detected in the transverse and descending colon, mainly at the end of fermentation process. On the other hand, the main families of microbial proanthocyanidin metabolites detected were valerolactones and benzoic acids mainly between 10-14 days of wine fermentation.