Establishing the Phenolic Composition of Olea europaea L. Leaves from Cultivars Grown in Morocco as a Crucial Step Towards Their Subsequent Exploitation

Abstract

In Morocco, the recovery of olive agro-industrial by-products as potential sources of high-added value substances has been underestimated so far. A comprehensive quantitative characterization of olive leaves’ bioactive compounds is crucial for any attempt to change this situation and to implement the valorization concept in emerging countries. Thus, the phenolic fraction of olive leaves of 11 varieties (‘Arbequina’, ‘Hojiblanca’, ‘Frantoio’, ‘Koroneiki’, ‘Lechín’, ‘Lucque’, ‘Manzanilla’, ‘Picholine de Languedoc’, ‘Picholine Marocaine’, ‘Picual’ and ‘Verdal’), cultivated in the Moroccan Meknès region, was investigated. Thirty eight phenolic or related compounds (including 16 secoiridoids, nine flavonoids in their aglycone form, seven flavonoids in glycosylated form, four simple phenols, one phenolic acid and one lignan) were determined in a total of 55 samples by using ultrasonic-assisted extraction and liquid chromatography coupled to electrospray ionization-ion trap mass spectrometry (LC-ESI-IT MS). Very remarkable quantitative differences were observed among the profiles of the studied cultivars. ‘Picholine Marocaine’ variety exhibited the highest total phenolic content (around 44 g/kg dry weight (DW)), and logically showed the highest concentration in terms of various individual compounds. In addition, chemometrics (principal components analysis (PCA) and stepwise-linear discriminant analysis (s-LDA)) were applied to the quantitative phenolic compound data, allowing good discrimination of the selected samples according to their varietal origin.

Evaluation of Phytochemical and Antioxidant Properties of 15 Italian Olea europaea L. Cultivar Leaves

“…The most abundant compounds were quinic acid (about 6–25 g/kg −1 DW), luteolin 7- O glucoside (about 8–40 g/kg −1 DW), oleuropein (about 7–30 g/kg −1 DW), 2-methoxy oleuropein (about 2–22 g/kg −1 DW), and hydroxytyrosol glucoside (in the range 1–17 g/kg −1 DW, except for the cultivar Cellina di Nardò which was about three-fold higher). These results agree with previous studies concerning olive leaves grown in Greece, Tunisia, and Morocco [29,30,31,32].…”

Addition of Olive Leaf Extract (OLE) for Producing Fortified Fresh Pasteurized Milk with An Extended Shelf Life

“…A series of hydroxycinnamic acids (peaks 4, 5, 7, 8 and their close derivative verbascoside, peak 6) were also found to belong to the secondary metabolic pool of OLE, even in small amounts Olive leaves composition may vary depending on environmental and genetic factors such as cultivar [23,24]; extraction solvent also play a pivotal role, together with extraction time and temperature [25]. Nevertheless, oleuropein as most abundant compound seems to be a recurrent data in literature, as reported by Edziri and co-workers for Tunisian O. europaea varieties [26], by Olmo-Garcia et al for olive leaves collected in Morocco [27] and by Romani and others for olive leaves obtained in Italy (Tuscany, Latium, Apulia) [28]. The findings here reported, which are rather different from those of the cultivar “Biancolilla” previously studied in our laboratories, further support literature data.…”

Target and Suspect HRMS Metabolomics for the Determination of Functional Ingredients in 13 Varieties of Olive Leaves and Drupes from Greece

“…The vast majority of the extraction protocols that have been reported for the determination of phenolic compounds in olive organs use mainly solid–liquid extraction (SLE) [ 1 , 7 , 8 , 21 , 26 , 27 , 30 , 31 , 32 , 33 , 34 ]. Solvents such as ethanol [ 14 , 19 , 35 , 36 ], water [ 14 , 19 , 28 , 36 , 37 ], acetone [ 28 ], ethyl acetate [ 13 , 36 ] and mixtures of ethanol:water [ 5 , 38 , 39 ] have been used for the extraction of biophenols in olives and leaves. However, the solvents mainly used are methanol [ 13 , 15 , 29 , 32 , 37 ] and mixtures of methanol:water (80:20, v / v ) [ 1 , 8 , 31 , 33 , 34 ].…”