In vitro bioaccessibility and protective activity of an anthocyanin-rich extract from bilberry and blackcurrant against TNF-α-induced inflammation in intestinal epithelial cells

Epidemiological studies suggest that the consumption of food rich in anthocyanins is associated with a reduced risk of different diseases, and support their beneficial effects in various chronic inflammatory diseases, such as inflammatory bowel diseases (IBDs). Nevertheless, the bioavailability of these substances is reported to be very low, mainly due to poor stability during gastrointestinal digestion. Hence, the aim of this study was to evaluate, through a static in vitro digestion model, the bioaccessibility of an anthocyanin rich standardized extract (ACN) from bilberry and blackcurrant, as well as the bioactivity of this digested product in an in vitro model of intestinal inflammation based on Caco-2 cells exposed to TNF-α. The bioaccessibility results, obtained through HPLC-UV/Vis analysis, confirmed the high instability of anthocyanins in the mild alkaline environment of the small intestine, reporting a 13% of recovery index. This high loss in anthocyanins corresponded to the decrease in the reducing power observed by the FRAP assay. However, the Pearson’s correlation test evidenced a weak correlation between FRAP assay and total anthocyanins content of the GI digested, suggesting that newly formed metabolites could probably contribute to the antioxidant power. Moreover, although the high loss of anthocyanins, the digested product maintained part of its bioactivity in the in vitro Caco-2 model, proved by the inhibition of the NF-κB pathway induced by TNF-α, and by the activation of Nrf2 pathway. The present data demonstrated that anthocyanins exert in vitro intestinal protective effects against proinflammatory stimuli-induced cell damage. Interestingly, this effect was demonstrated at concentrations that are physiologically achievable following dietary supplementation, as demonstrated by the bioaccessibility findings. These data hence confirm that anthocyanins could provide a wide contribution to intestinal health when introduced through the diet or as a food supplement, and thus could represent a possible approach for the prevention of IBDs.