Antioxidant Effect of Phenolic Components of Virgin Olive Oil and their Bioavailability in Human
D. Caruso, B. Berra, A. Bonanome, N. Cortesi, E. Fedeli, F. Giavarini, A. Pagnan and G. Galli.
Istituto di Scienze Farmacologiche, Universita' di Milano, Milano, Italy
Substantial evidences suggest that oxidative modification of low density lipoprotein (LDL) critically contribute to the pathogenesis and progress of human atherosclerosis. Oxidised LDL (oxLDL) are present in atheromas and contain oxysterols that exhibit a variety of adverse biological activities. Antioxidants have also been shown to prevent LDL oxidative modification. Epidemiological studies have linked the Mediterranean diet with a low incidence of cardiovascular disease, and olive oil is a major fat component of this diet. This nutrient posses antioxidant properties that are also related to their content in phenolic components, such as hydroxytyrosol and oleuropein. For this reason we tested the in vitro activity of different concentration of virgin olive oil phenolic extract (PCO), their pure component (tyrosol, oleuropein) and probucol, a widely used antioxidant drug, on the formation of cholesterol oxides and changes in apoB electrophoretic mobility as marker of human LDL oxidation induced by UV light exposure. The results demonstrated that PCO are much more potent in preventing cholesterol oxides formation and apoproteic moiety modification than their pure components and probucol. However, their bioavailability has not been so far ascertained. Data from eight healthy volunteers, after virgin olive oil consumption, showed that LDL and HDL contain simple phenolic compounds such as tyrosol (TYR) and hydroxytyrosol (OHTYR) which reached a peak at 60-120 min. Moreover PCO seem to exhert a significant antioxidant effect in vivo, evaluated as plasma antioxidant capacity, which is detectable in the postprandial phase. From these results it can be assumed that the unique phenolic constituents of virgin olive oil may contribute to the beneficial effect of the Mediterranean diet.