Anthocyanins from red wine--their stability under simulated gastrointestinal digestion

The stability of anthocyanins from red wine was assessed using an in vitro digestion system that simulated the physiochemical changes that occur in the upper gastrointestinal tract. Anthocyanins in red wine were stable to gastric conditions whereas there was a small loss in total phenol content. After pancreatic digestion, the total anthocyanins were very poorly recovered compared to the bulk phenols in the IN sample, which was previously described as the "serum-available" fraction, and the majority of the anthocyanins and phenols were recovered in the OUT fraction, previously described as the "colon-available" fraction. Removing alcohol from the wine samples prior to the procedure did not markedly affect this pattern. The composition of anthocyanins in the post gastric, IN and OUT samples was analysed using liquid chromatography mass-spectrometry. The red wine used contained over 20 identifiable anthocyanins of which the main components were 3-O-glucosides of malvidin, peonidin, petundin, delphidin and cyanidin. Coumaroylated-glucoside derivatives of malvidin, petundin, peonidin, and delphinidin were observed and acetylated glucosides of peonidin, petundin and malvidin were also identified. Anthocyanins with modified aglycones similar to vitisin A derivatives of delphinidin, peonidin, petunidin and malvidin were also identified. After the in vitro digestion procedure, only five anthocyanins could be detected in the IN (serum-available) and the OUT (colon-available) fractions, which were confirmed as malvidin-3-O-glucoside and the vitisin A adducts of malvidin-3-O-glucoside, malvidin-3-O-acetylglucoside, malvidin-3-O-coumaroylglucoside and peonidin-3-O-glucoside. Malvidin-3-O-glucoside was recovered at 0.2% in the IN fraction and 0.9% in the OUT fraction. However, the vitisin derivatives were much more stable to pancreatic digestion. Assuming that the vitisin A derivatives display similar biological properties to their parent anthocyanins, their enhanced gastrointestinal stability could lead to enhanced bioavailability and bio-effectiveness in vivo.