Stability and biological activity of wild blueberry (Vaccinium angustifolium) polyphenols during simulated in vitro gastrointestinal digestion

Wild blueberries are rich in polyphenols and have several potential health benefits. Understanding the factors that affect the bioaccessibility and bioavailability of polyphenols is important for evaluating their biological significance and efficacy as functional food ingredients. Since the bioavailability of polyphenols such as anthocyanins is generally low, it has been proposed that metabolites resulting during colonic fermentation may be the components that exert health benefits. In this study, an in vitro gastrointestinal model comprising sequential chemostat fermentation steps that simulate digestive conditions in the stomach, small intestine and colon was used to investigate the breakdown of blueberry polyphenols. The catabolic products were isolated and biological effects tested using a normal human colonic epithelial cell line (CRL 1790) and a human colorectal cancer cell line (HT 29). The results showed a high stability of total polyphenols and anthocyanins during simulated gastric digestion step with approximately 93% and 99% of recovery, respectively. Intestinal digestion decreased polyphenol- and anthocyanin- contents by 49% and 15%, respectively, by comparison to the non-digested samples. During chemostat fermentation that simulates colonic digestion, the complex polyphenol mixture was degraded to a limited number of phenolic compounds such as syringic, cinnamic, caffeic, and protocatechuic acids. Only acetylated anthocyanins were detected in low amounts after chemostat fermentation. The catabolites showed lowered antioxidant activity and cell growth inhibition potential. Results suggest that colonic fermentation may alter the biological activity of blueberry polyphenols.