In vitro bioaccessibility, transepithelial transport and antioxidant activity of Urtica dioica L. phenolic compounds in nettle based food products

Nettle (Urtica dioica L.) is a well-known plant with a wide historical background use of stems, roots and leaves. Nettle leaves are an excellent source of phenolic compounds, principally 3-caffeoylquinic acid (3-CQA), caffeoylmalic acid (CMA) and rutin. The aim of this work was to evaluate the bioaccessibility (BAC), the bioavailability (BAV) and the antioxidant activity of nettle phenolic compounds present in foods and supplements. The BAC of nettle phenolics was evaluated with an in vitro dynamic digestion of real food matrices: the type of food matrix and chemical characteristic affected the kinetics of release and solubilization, with the highest BAC after duodenal digestion. A study of duodenal trans epithelial transport evidenced low bioavailability of native forms of 3-CQA, CMA and rutin. Simulation of colonic metabolism confirmed that phenolic compounds are fermented by gut microflora, confirming the need for further investigations on the impact of phenolic compounds at the large intestine level. Photochemiluminescence assay of the simulated digestion fluids demonstrated that ingestion of Urtica based foods contributes to create an antioxidant environment against superoxide anion radicals in the entire gastrointestinal tract (GIT).