Biological activities and metabolic fate of olive oil phenols

We have been studying the biological activities of olive oil phenols in vitro and in vivo including the bioavailability of phenols and their effects in animals and humans. In vitro, ortho-diphenolic (catecholic) compounds such as oleuropein and hydroxytyrosol exert potent antioxidant activities, such as inhibition of low density lipoproteins oxidation and free radical scavenging. They modify pathophysiological processes at cellular level favorably, e.g. by inhibiting not only the production of superoxide anions and the respiratory burst of neutrophils, but also platelet aggregation and the production of thromboxane and leukotriene B-4 by neutrophils. Finally, oleuropein stimulates the release of nitric oxide by macrophages. Most important, recent data demonstrate that oleuropein and hydroxytyrosol, active at concentrations in the low muM range, are dose-dependently absorbed by humans and rats and, at very low doses, maintain their antioxidant activities in vivo. This is indicated by the increase in plasma antioxidant capacity and the reduced excretion of isoprostanes in humans and in sidestream smoke-exposed rats. To this end, our studies demonstrated that high quality, phenol-rich olive oil provides bioactive compounds that exert salubrious effects in humans and thus may contribute to the beneficial properties of the Mediterranean diet.