Seasonal variations in antioxidant compounds of <i>Olea europaea</i> leaves collected from different Italian cultivars




Olea europaea leaves, antioxidant activity, oleuropein, hydroxytyrosol, HPLC-DAD


The objectives of this research were to study the best conditions for phenol extraction from olive tree leaves and to evaluate the content of phenolics and the antioxidant activity by in vitro assays in olive leaves harvested in different periods from four different Italian cultivars. The results showed that leaves/solvent ratio and temperature showed a significant and positive correlation with phenol extraction yield. In all harvesting periods the phenol content of Dolce Agogia samples was higher (P ≤ 0.05) with respect to Moraiolo, Leccino and Frantoio samples. The results of analysis by high-performance liquid chromatography coupled with diode array detector (HPLC-DAD) showed that Dolce Agogia had the highest concentrations of hydroxytyrosol and oleuropein. Moreover the highest contents of bioactives have been found in olive leaves harvested in December and March. In these months, corresponding to olive harvest and pruning of olive trees, leaves represent a waste product and this interesting result could be useful in the production of nutraceuticals.