Evaluation of antioxidant activities of phenolic compounds from two extra virgin olive oils

The aim of this work was to investigate the antioxidant properties of two varieties of olive oil (Chétoui and Chemlali), and to study the protective effect of phenolic extract (PE) from these varieties against low density lipoprotein (LDL) oxidation in vitro. Antioxidant activities were examined as well, using different radical scavenging assays: radical scavenging activity by DPPH, and total antioxidant status by ABTS. The antioxidant effect of the oils on human LDL was evaluated by measuring levels of conjugated dienes and polyunsaturated fatty acids. Chemlali oil was less rich in total phenols (158 mg/kg) than Chétoui oil (395 mg/kg) (p < 0.05). The highest antioxidant activity was attributed to Chétoui oil (78.56% vs. 37.23% of DPPH and 2.42 vs. 0.61 mmol Trolox/kg; p < 0.05). Chétoui PE had a significantly greater inhibitory effect on LDL oxidation than Chemlali PE (lag time = 116 ± 6.05 min vs. 64 ± 11.31 min at 0.3 mg/l of PE respectively; p < 0.05). The differences in quantity and quality of the studied oils influenced their biological activities and they could provide beneficial effects in cardiovascular disease by inhibiting LDL oxidation.