Evaluation of phenolic composition and antioxidant activity changes in olive flowers during development using HPLC/DAD and LC-MS/MS.

Olive fruit and leaves have been extensively studied for their chemical compositions and biological activities. However, less attention has been given to its flowers. The present research was achieved on Tunisian olive flowers. It aimed at studying the effects of flower development on phenolic compounds and antioxidant activity. The extracts were analyzed using high performance liquid chromatography coupled to diode array detection (HPLC/DAD) and coupled to mass spectrometry (LC-MS/MS). The HPLC/DAD analysis indicated that oleuropein aglycon (from 1.158 to 3.746 g/kg), followed by hydroxytyrosol (from 0.168 to 1.581 g/kg) and oleoside (from 0.143 to 1.325 g/kg) were the predominant phenolics in olive flowers extracts during development stages. Twenty compounds have been identified, revealing the complex profile of olive flowers, composed, in order of abundance, by secoiridoids, phenolic alcohols, lignans, flavonoids and phenolic acids. Total phenolic contents increased from 2.455 to 8.541 g/kg Gallic acid equivalent per kg of fresh flowers during all steps of the flower development. A correlation between antioxidant activity and total phenolic contents was determined.

Rekik O ，Ben Mansour A ，Bouaziz M 《-》

RP-HPLC-DAD-ESI-QTOF-MS based metabolic profiling of the potential Olea europaea by-product "wood" and its comparison with leaf counterpart.

Olea europaea L. organs such as leaves, stems and roots have been associated with numerous in vivo and in vitro biological activities and used for traditional medicinal purposes. However, tree wood is an untapped resource with little information about their chemical composition. That is why, the objective of this study is to increase the knowledge about phytochemicals from 'Chemlali' olive wood by means of mass spectrometry-based analyses. Its comparison with by-products derived from leaves was also studied. Hydromethanol extracts from wood and leaves with stems of 'Chemlali' olive cultivar were analysed using reversed-phase (RP) high-performance liquid chromatography (HPLC) coupled to two detection systems: diode-array detection (DAD) and quadrupole time-of-flight (QTOF) mass spectrometry (MS) in negative ion mode. Tandem MS experiments were performed to establish the chemical structure of olive phytochemicals. A total of 85 compounds were characterised in the studied olive parts and classified as: sugars (3), organic acids (5), one phenolic aldehyde, simple phenolic acids (6), simple phenylethanoids (5), flavonoids (14), coumarins (3), caffeoyl phenylethanoid derivatives (6), iridoids (5), secoiridoids (32), and lignans (5). To our knowledge, the major part of these metabolites was not previously reported in olive tree wood, and 10 olive chemical constituents were identified for the first time in the Oleaceae family. The results presented here demonstrated the usefulness of the methodology proposed, based on RP-HPLC-DAD-ESI-QTOF-MS and MS/MS, to develop an exhaustive metabolic profiling and to recover new biologically active compounds in olive wood with pharmacologic and cosmetic potential. Copyright © 2017 John Wiley & Sons, Ltd.

Ammar S ，Contreras MDM ，Gargouri B ，Segura-Carretero A ，Bouaziz M ... -  《-》

Changes in phenolic composition in olive tree parts according to development stage.

The aim of this study was to investigate the changes in the phenolic profile in different organs (buds, flowers, fruits and leaves) from Chemlali olive variety cultivated in the Center of Tunisia according to development stage. Phenolics recovery was carried out using aqueous methanol from freeze-dried powdered tissues. The extracts were then analyzed by using high performance liquid chromatography coupled to time of flight and ion trap mass spectrometry detectors. Qualitatively, secoiridoids, flavonoids, simple phenols, cinnamic acid derivatives and lignans were identified in the analyzed extracts. Quantitatively, floral buds showed the highest phenolic contents compared to the other tissues under study. The highest content of secoiridoids was observed for unripe fruit extract, whereas the highest content of flavonoids was registered for floral buds.

Abaza L ，Taamalli A ，Arráez-Román D ，Segura-Carretero A ，Fernández-Gutierrérez A ，Zarrouk M ，Youssef NB ... -  《-》

Characterisation of phenolic compounds by HPLC-TOF/IT/MS in buds and open flowers of 'Chemlali' olive cultivar.

Plant phenolics are secondary metabolites that constitute one of the most widely occurring groups of phytochemicals that play several important functions in plants. In olive (Olea europaea L), there is not enough information about the occurrence of these compounds in buds and flowers. To conduct a comprehensive characterisation of buds and open flowers from the olive cultivar 'Chemlali'. The polar fraction of buds and open flowers was extracted using solid-liquid extraction with hydro-alcoholic solvent. Then extracts were analysed using high performance liquid chromatography (HPLC) coupled to electrospray ionisation time-of-flight mass spectrometry (ESI/TOF/MS) and electrospray ionisation ion-trap tandem mass spectrometry (ESI/IT/MS²) operating in negative ion mode. Phenolic compounds from different classes including secoiridoids, flavonoids, simple phenols, cinnamic acid derivatives and lignans were tentatively identified in both extracts. Qualitatively, no significant difference was observed between flower buds and open flowers extracts. However, quantitatively the secoiridoids presented higher percentage of total phenols in open flowers (41.7%) than in flower buds (30.5%) in contrast to flavonoids, which decreased slightly from 38.1 to 26.7%. Cinnamic acid derivatives and simple phenols did not show any change. Lignans presented the lowest percentage in both extracts with an increase during the development of the flower bud to open flower. The HPLC-TOF/IT/MS allowed the characterisation, for the first time, of the phenolic profile of extracts of 'Chemlali' olive buds and open flowers, proving to be a very useful technique for the characterisation and structure elucidation of phenolic compounds.

Taamalli A ，Abaza L ，Arráez Román D ，Segura Carretero A ，Fernández Gutiérrez A ，Zarrouk M ，Nabil BY ... -  《-》

Comparative study on phenolic content and antioxidant activity during maturation of the olive cultivar Chemlali from Tunisia.

Bouaziz M ，Chamkha M ，Sayadi S 《JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY》