Changes to the phenolic composition and antioxidant activity of pigmented cereal grain extracts following simulated in vitro digestion and Caco-2 cellular transport

Grain polyphenol extracts are believed to have disease preventive properties, however their bioactivity associated with bioavailability warrants investigation. The current study assessed the in vitro bioavailability of polyphenolic extracts derived from pigmented grains using a simulated in vitro digestion and intestinal absorption model. Purple rice, purple barley, purple wheat, and blue wheat extracts were subjected to gastric and intestinal phase digestion followed by Caco-2 cellular transport. Phenolic profiling and antioxidant activity was analysed using benchtop assays and an UHPLC-Online ABTS system. Results showed a significant decrease in total phenolic content among extracts after digestion, with purple rice extract retaining the greatest phenolic content (79%) and ABTS antioxidant activity (31%). Antioxidant activity was retained the most in the gastric phase, but dominant antioxidant compounds were undetected after intestinal digestion. Digestion of extracts lead to the emergence of new compounds and altered antioxidant activity, indicating a significant impact on phenolic composition and radical scavenging activity. The Caco-2 cellular transport assay revealed that compounds transported across included protocatechuic acid, vanillic acid, apigenin and chrysoeriol. Findings from this study highlight the potential bioavailability and antioxidant activity of pigmented grain polyphenols, thus, promoting the value of these pigmented grains as sources of functional food ingredients.