Metabolite profiling and dereplication of different Olea europaea organs by UHPLC-DAD and HPLC-HRMS

Abstract

The olive tree (Olea europaea L., Oleaceae) is one of the most important tree crops in the Mediterranean basin, and virgin olive oil is consumed all over the world for its nutritional and medicinal values. Several studies have shown that consumption of olive oil is correlated with decreased risk of cardiovascular disease, obesity, metabolic syndrome and type-2 diabetes [1]. These biological effects have been mainly attributed to phenylethanols, secoiridoids, flavonoids and lignans found in olive fruits [2 – 3]. The chemical composition of olive fruits, olive oil and olive by-products has been extensively studied, while other plant parts like stems, roots and seeds have received little attention up to now. We here investigated the secondary metabolites in various plant parts of two olive tree varieties (Koroneiki from Greece, and Chetoui from Tunisia), in order to obtain a better understanding on the metabolite profiles, and to identify new phytochemicals with potentially useful biological properties. Olive extracts (leaf, stem, root and seed) were obtained by Accelerated Solvent Extraction and profiled by UHPLC-DAD/FLD. Aiming at a rapid identification of constituents, a dereplication strategy using HPLC-DAD-HRMS and MS/MS Orbitrap was applied. Based on chromatographic and spectrophotometric features (Rt, UV, accurate m/z, proposed elemental composition, ring double bond equivalents), chemotaxonomic data and HRMS/MS spectra, a total of 90 compounds belonging to various chemical classes were identified. The two olive varieties showed similar metabolite profiles with some minor, mainly quantitative, differences. The DPPH radical scavenging activity of extracts was assessed and was found to correlate with the oleuropein content.