Polyphenolic profile, macro- and microelements in bioaccessible fractions of grape juice sediment using in vitro gastrointestinal simulation

Abstract

Grape and grape constituents have high amounts of essential minerals and polyphenols. Health benefits of these nutrients and other bioactive substances depend on their level of intake and bioaccessibility. The behavior and levels of individual phenolic compounds, macro- and microelements of the grape juice sediment that was removed from red grape juices of Bordo and Isabel varieties were investigated using an in vitro digestion and determined using high performance liquid chromatography-diode array detection and inductively coupled plasma optical emission spectrometry. During digestion, important changes were observed in concentrations of polyphenols and minerals upon passage through the gastric and enteric phases. Bioactive compounds such as trans-resveratrol, catechin and epicatechin were highly bioaccessible from the Bordo sample. A significant decrease in levels of polyphenolics and minerals was observed at the end of the intestinal phase. The grape juice sediment of both varieties showed higher antioxidant capacity in the gastric phase, which was related to the high concentration of polyphenols. The anthocyanins identified at higher concentrations in samples included malvidin-3-O-glucoside and malvidin-3,5-diglucoside that were 7% and 60% bioaccessible, respectively. The elements Ca, Mg, Cu, Fe, Sr, Mn, Zn, Al, Ni and Pb were not detected at the last phase of digestion, being poorly bioaccessible. The bioaccessibility indexes found for this grape juice sediment are consistent with the bioactive properties of grape products.