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

Abstract

Olive leaf extracts are of special interest due to their proven therapeutic effects. However, they are still considered a by-product of the table olive and the oil industries. In order to learn possible ways of exploiting this waste for health purposes, we investigated the phytochemical profiles and antioxidant activities in the leaves of 15 Italian Olea europaea L. cultivars grown in the same pedoclimatic conditions. The phenolic profiles and amounts of their seven representative compounds were analyzed using HPLC ESI/MS-TOF. The antioxidant activities were determined using three different antioxidant assays (DPPH, ORAC, and superoxide anion scavenging assay). Wide ranges of total phenolic content (11.39–48.62 g GAE kg−1 dry weight) and antioxidant activities (DPPH values: 8.67–29.89 µmol TE mg−1 dry weight, ORAC values: 0.81–4.25 µmol TE mg−1 dry weight, superoxide anion scavenging activity values: 27.66–48.92 µmol TE mg−1 dry weight) were found in the cultivars. In particular, the cultivars Itrana, Apollo, and Maurino, showed a high amount of total phenols and antioxidant activity, and therefore represent a suitable natural source of biological compounds for use in terms of health benefits.

Potential Inhibitor of COVID-19 Main Protease (M^pro) From Several Medicinal Plant Compounds by Molecular Docking Study

“…Kaempferol Spinach Spinacia oleracea [26] Cabbage Brassica oleracea [26] Dill Anethum graveolens [26] Chinese cabbage Brassica rapa [26] Katuk Sauropus androgynus [27] Quercetin Dill Anethum graveolens [26] Fennel leaves Foeniculum vulgare [26] Onion Allium cepa [26] Oregano Oregano vulgare [26] Chili pepper Capsicum annum [26] Luteolin-7-glucoside Olive Olea Europaea L [28][29][30] Star fruit Averrhoa belimbi [31] Chili pepper Capsicum annum [31] Welsh onion / Demethoxycurcumine Turmeric Curcuma longa [32,33] Curcuma Curcuma xanthorriza [32,33] Naringenin Citrus fruit Citrus sinensis [34] Apigenine-7-glucoside Star fruit Averrhoa belimbi [31] Goji berries Lycium chinense [31] Celery Apium graveolens [31] Olive Olea Europaea L [28,29] Oleuropein Olive Olea Europaea L [28][29][30] Catechin Green tea Camellia sinesis [35][36][37] Curcumin Turmeric Curcuma longa [38][39][40][41] Curcuma Curcuma xanthorriza [32], [33] Epicatechin gallate Green tea Camellia sinesis [35][36][37] Zingerol Ginger Zingiber officiale [42]…”

Biochemical Changes in Leaves of Vitis vinifera cv. Sangiovese Infected by Bois Noir Phytoplasma

“…The phenolic characterization and quantification on leaf extracts (see Section 2.3) were performed using an Agilent 1200 High Performance Liquid Chromatography (HPLC) System (Agilent Technologies, Palo Alto, CA, USA) equipped with a standard autosampler and an Agilent Zorbax Extend-C18 analytical column (5 × 2.1 cm, 1.8 µm), as reported by [28,36]. The HPLC system was coupled to an Agilent diode-array detector (wavelength 280 nm) and an Agilent 6320 TOF mass spectrometer equipped with a dual ESI interface (Agilent Technologies) operating in negative ion mode.…”

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

“…Olive leaves are by-products of olive tree cultivation (pruning) and olive oil production [ 5 , 6 , 7 , 8 ]. The leaves of O. europaea L. are rich in phenols, characterized as “biophenols” since they present several therapeutic properties [ 6 , 7 ]. It is worth mentioning that the water extract of olive leaves has been widely used in traditional medicine to cure fever and treat several diseases such as hypertension, inflammation and diabetes as well [ 9 ].…”

“…Based on previous reports, the most abundant functional compounds in olive leaves are oleuropein, tyrosol and hydroxytyrosol [ 16 ]. Even though oleuropein is mainly concentrated in olive leaves, it is also found in drupes [ 7 ]. Oleuropein is the major secoiridoid of the olive fruit [ 13 ], and its concentration decreases during fruit ripening, giving rise to hydroxytyrosol, which is the main product of oleuropein degradation, and to other simple phenols such as tyrosol [ 4 , 17 , 18 ].…”

“…However, the complete characterization of the phenolic profile of olive leaves still remains uninvestigated [ 13 ]. Only a few reports are available concerning the determination of phenolic compounds in Italian [ 7 ], Tunisian [ 8 , 26 ] and Ιranian O. europaea leaves [ 27 ]. As for the Greek olive leaves and drupes, limited data are available about minor constituents’ determination in Greek O. europea organs, olive oil, leaves and drupes, while there are no comparative studies investigating this topic [ 10 , 13 , 28 , 29 ].…”