Flavonoids from a grape seed extract interact with digestive secretions and intestinal cells as assessed in an in vitro digestion/Caco-2 cell culture model

Although the bioactivity of flavonoids is related to their bioavailability, little is known about pre-absorption events in the gastrointestinal tract and their possible interactions with digestive constituents and intestinal cells. Using an in vitro digestion/Caco-2 cell culture model, we investigated the effect of digestive secretions on the stability of (+)-catechin (CAT), (−)-epicatechin (EC) and B2 and B3 dimers from a procyanidin-rich grape seed extract (GSE). The availability of phenolic compounds was not affected by salivary and gastric incubations but decreased during intestinal digestion in the absence of Caco-2 cells due to interactions with pancreatic proteins, unmasked by acetonitrile extraction. Then, in the presence of cells, about 43.9% of CAT, 85.3% of EC and all dimers disappeared at the end of 2 h of intestinal incubation. The stability of all compounds at intestinal pH was demonstrated as well as interactions with proteins, associated with a decrease of some cells enzyme activities, e.g., alkaline phosphatase (−79.8%), sucrase-isomaltase (−60.9%) and aminopeptidase N (−60.7%). Moreover, no compounds were detected in the basal compartment of transwells or in cell monolayers.