Ecological variability of the phenolic compounds of Olea europaea L. leaves from natural habitats and cultivated conditions

Abstract

Many compounds from the phenolic group, flavonoids in particular, are well-known antioxidants, although their role in plant response to stress is debatable. The aim of this study was to determine the variability of the phenolic content and the antioxidant activity of Olea europaea leaf samples from different habitats. The determination included measurement of the total quantity of phenolics, the flavonoid content, as well as the antioxidant activity of the two types of methanolic leaf extracts of O. europaea from several natural habitats in the Mediterranean region (Tunisia, Malta and Montenegro) and from cultivated conditions (France and Serbia). The results showed that both the total quantity of phenols and flavonoids as well as the intensity of antioxidant activity in the two types of extracts largely depended on the type of habitat. The total quantity of phenols and flavonoids was greater in the samples from cultivated plants which demonstrated the significance of certain conditions in terms of the correlation between the intensity of primary and secondary metabolism. However, the values of antioxidant activity in both types of extract were higher in the samples from natural habitats. The results showed that plants from natural habitats contain secondary metabolites with high biological activity. It could be speculated that these active substances play an important role in the adaptation of plants to the stress caused by arid conditions.