Investigating the bioavailability and bioactivity of black carrot polyphenols in an in-vitro epithelial-endothelial co-culture model

It has attracted attention to consume polyphenol rich fruits and vegetables and utilise their byproducts recently. Black carrot is one of those foods that is rich in polyphenols especially in anthocyanins. These compounds have numerous health benefits to living organisms including protection to neurodegenerative diseases, cancer and cardiovascular diseases. In order to have these health benefits polphenols should be bioavailable to the organism. This study was performed to test bioavailability and bioactivity of black carrot anthocyanins. Besides raw black carrot samples, pomace and peel samples were also studied. In order to simulate absorption and bioactivity of polyphenols in black carrot, pomace and peel, in vitro cell models were used. Transport experiments were carried out with Caco-2 cells and co-culture experiments were designed with both Caco-2 and Eahy926 cell lines. Results were monitored with HPLC-DAD. In co-culture experiments nitric oxide assay (NO), intracellular reactive oxygen species assay (ROS) were used, as well as enzyme-linked immunosorbent assays (ELISA) to evaluate the anti-inflammatory effect of black carrot anthocyanins. Both in transport and co-culture experiments, digested samples gave better results than undigested samples. In bioavailability experiments digested samples were found to have a basal recovery between 1.3 – 5.3 % of initial anthocyanin concentration whereas undigested samples were found between 0.8 – 2.7 % of initial values. A similar result was seen in transport of phenolic acids. No cytotoxic effect was observed after 24 hours prior to treatment (TEER values were found between 74-93 % of initial values after 24 hours). The anti-inflammatory effect was determined in cells treated with black carrot, pomace and peel samples by using MCP-1, VEGF, ICAM-1 and IL-8 markers. In these experiments, black carrot anthocyanins were found to have anti-inflammatory effect with decrease of these markers up to 92 %. This co-culture model was found to be applicable for bioavailability and bioactivity studies.