Abstract

A high dietary intake of fruits and vegetables is associated with a reduced disease risk. The fruits and vegetables contain fibers, vitamins, phytosterols, sulfur compounds, carotenoids, and organic acids, which all provide beneficial effects on health, but they also contain a variety of polyphenols. Recently, polyphenols have received considerable attention because of their various physiological effects, including anti-oxidative, anti-inflammatory and anti-carcinogenic effects. In addition, experimental evidence demonstrates that some polyphenols participate in regulation of intestinal tight junction (TJ) barrier. The TJ, a multiple-protein complex, regulates the paracellular permeability between the epithelial cells and the dysfunction is implicated with the pathogenesis of intestinal and systemic diseases. Among polyphenols investigated, quercetin, kaempferol, myricetin, morin, hesperetin, naringenin and daidzein have been reported to enhance the basal TJ integrity in intestinal cells. In most cases, the enhancements are accompanied by increases in the expression and/or cytoskeletal association of TJ proteins, such as occludin, claudins and zonula occludens. Genistein, epigallocatechin- 3-gallate and curcumin present protective effects on the TJ integrity against harmful substances, such as oxidative stress and pro-inflammatory cytokines. Chrysin increases the intestinal permeability through decreased expression and cytoskeletal association of TJ proteins. Based on these evidences, the regulation of intestinal TJ barrier by polyphenols could be therapeutic and preventive approaches for intestinal barrier defect-associated diseases.

Keywords: Flavonoid, intestinal barrier, intestine, polyphenol, tight junction.