Natural table olives phenolic extract counteract the harmful effects of oxidative stress in human intestinal cells.

Abstract

Table olives are recognized as a valuable source of natural phenolic antioxidants. In this study we analyzed the ability of the phenolic fraction of a Sardinian cultivar of naturally fermented table olives, “Tonda di Cagliari”, to protect Caco-2 cell monolayers against oxidative stress and membrane disruption induced by tert-butil hydroperoxide (TBH). TBH exposure resulted in an alteration of cellular redox status, with an increase of ROS and a decrease of GSH intracellular level, which led over time to a loss of the epithelial integrity, as indicated by the decrease of the transepithelial electrical resistance (TEER) value. Pretreatment of Caco-2 cells with the olives phenolic extract at non-toxic concentrations (10 – 50 µg/mL) prevented ROS generation, GSH depletion and the loss of the epithelial integrity. The protective action of the extract is likely due to the ability of its main components, hydroxytyrosol, oleuropein and verbascoside, to scavenge TBH generated radicals or intermediate of reaction metabolites. Olives phenolic compounds concentrate in the intestinal lumen, where they may contribute, together with their metabolites, to protect the intestinal mucosa against the damage caused by oxidative species.