Antioxidant Activity of the Leaf Volatile Oil and Extracts of Olea europaea L.cv. Chetoui from Northern Tunisia

This study is designed to examine the chemical composition and the in vitro antioxidant activity of the volatile oil and the extracts (polar and non-polar sub-fractions) of the methanol extract of Olea europea L. (cv) chetoui. GC and GC–MS analyses of the volatile oil from the dried leaves of the variety chetoui resulted in the identification of 32 compounds, representing 92.1% of the oil; alcohols (39.5%), aldehydes (19.1%) and ketones (12.2%) were the main groups of volatiles in the studied cultivar, comprising 70.8% of the total oil. Antioxidant activities of the samples were determined by the test system namely DPPH. The weakest radical scavenging activity was exhibited by the volatile oil (49.92%). Antioxidant activity of the non-polar sub-fraction of methanol extract was superior to the all samples tested with an inhibition of the free radical DPPH value of 64.31%. Total phenolic content of the polar and non-polar sub-fractions was 65.35 and 69.17 mg/100 g DW, respectively. In fact, the results showed no significant differences in the levels of polyphenols between sub-fractions of the methanol extract of Olea europea L. Furthermore, the amount of the total orthodiphenols was highest in the non-polar sub-fraction (219.66 mg /100 g DW). A positive correlation was observed between the antioxidant activity potential and total flavonoids content of the extracts.