Stability and biological activity of Merlot (Vitis vinifera) grape pomace phytochemicals after simulated in vitro gastrointestinal digestion and colonic fermentation

Grape pomace is an abundant/accessible food industry by-product that contains a wide range of phenolic compounds, which have been related to several health benefits and bioactivities. The aim of this study was to mimic the gastrointestinal digestion and the colonic fermentation of Merlot grape pomace, in order to unravel possible phytochemical contents reductions and the processes associated with them, as a tentative to relate the phenolic compound profiles of the extracts with their biological properties. LC-DAD-ESI/MS suggested that the in vitro digestion process promoted drastic qualitative and quantitative reductions in the phenolic compounds profile of the Merlot grape pomace crude extract. Such alterations could be related to the decreases of some bioactivities of the extract, which seems to be the case of antioxidant and antibacterial properties, although not in a directly proportional manner. However, the simulated colonic fermentation seems to have a positive effect over the extract's antiproliferative potential.