Release of wheat gluten exorphins A5 and C5 during in vitro gastrointestinal digestion of bread and pasta and their absorption through an in vitro model of intestinal epithelium

Pasta and bread provide energy and nutrients, but they also may represent a potential source of dietary bioactive substances. In this regard, attention has been paid to the physiological and pathological role of the gluten-derived peptides known as exorphins (GEs). To date the available studies refer to the presence of GEs in biological fluids, whereas no data are present concerning the occurrence and fate of GEs during in vitro digestion of real wheat-based foods. Moreover, no studies ascertained the absorption of GEs through the in vitro models of human intestinal epithelium. To understand the release of wheat GEs A5, A4, B5, B4, C5, Gd-7 and dGd-7 during gastrointestinal digestion (GID), bread and pasta samples were subjected to the in vitro static GID, and the obtained digesta were assessed for the presence of these peptides by means of UPLC/ESI-HRMS. Among the GEs, only the peptides A5 and C5 were detected at the end of GID. Levels of GEs A5 and C5 were in the range 0.747–2.192 mg kg-1 and 3.201–6.689 mg kg-1, respectively. The absorption behavior of GEs A5 and C5 was studied in detail using a Caco-2/HT-29 (70/30) co-culture model in vitro. The two peptides were susceptible to the action of the co-culture peptidases, and less than 3% of intact A5 and C5 crossed the co-culture layer after 120 min. Several hydrolytic fragments of both GEs crossed the co-culture layer as well. For the first time, these results demonstrate that GEs are released during in vitro GID of real wheat-derived foods and highlight the possibility of transport of the GEs A5 and C5 across the human intestinal mucosa.