Isolation, structure elucidation and antioxidant potential of the major phenolic and flavonoid compounds in brined olive drupes (original) (raw)
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Journal of Agricultural and Food Chemistry, 2005
Increasing interest in phenolic compounds in olives is due to their antioxidant and health-enhancing properties. In this study the phenolics in fruits of the Tunisian olive cultivar Chemlali were extracted by methanol-water and fractionated using Sephadex LH-20 column chromatography. The identification of phenolic monomers and flavonoids was based on separation by high-performance liquid chromatography equipped with a diode array detector followed by liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry analysis. Oleuropein, a secoiridoid glycoside esterified with a phenolic acid, was the major compound. Eight phenolic monomers and 12 flavonoids were also identified in Chemlali olives. Five flavonoids were isolated and purified using Sephadex LH-20 column chromatography and preparative paper chromatography. The antioxidant activity of the extract and the purified compounds was evaluated by measuring the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl and by using the-carotene-linoleate model assay. Acid hydrolysis of the extract enhanced its antioxidant activity. Hydroxytyrosol and quercetin showed antioxidant activities similar to that of 2,6-di-tert-butyl-4-methylphenol. A hydroxyl group at the ortho position at 3′ on the B ring of the flavonoid nucleus could contribute to the antioxidant activity of the flavonoids.
Phenolic Compounds in Olive Leaf Extract as a Source of Useful Antioxidants
hrcak.srce.hr
Using electron paramagnetic resonance (EPR) spectroscopy, antioxidant properties of olive leaves extracts obtained of three autochthonous olive varieties grown in Istria, Buža, Istarska bjelica and Rosinjola have been investigated. The highest content of total phenolic compounds ((57.6 ± 0.1) mg quercetin equivalents/g of dry extract) was obtained for extract of Buža. The analysis of chemical composition of extracts was performed by HPLC/DAD and LC/MS method. Futhermore, Buža has shown the highest antioxidant activity in scavenging DPPH radical (AA=80.0 ± 3.0%), followed by extracts of Rosinjola and Istarska bjelica. In DPPH radical scavenging assay fi nal concentration of extracts in was 0.1 mg/mL. Antioxidant activity was in good correlation with total phenolics. It seems that these bioproducts could be useful in therapy of conditions related with oxidative stress. The results have indicated a high potential of application of olive leaf and olive leaf extract in foodstuff and food additive. Also, it can be used to improve the shelf life of foods and to develop functional foods.
Acta Horticulturae, 2011
Ten Greek olive cultivars, 'Koroneiki', 'Lianolia Kerkyras', 'Mastoidis', 'Arbequina', 'Adramytini', 'Megaritiki', 'Gaidourelia', 'Kalamon', 'Konservolia' and 'Chalkidiki', were studied in order to determine the phenolic profile, the phenolic content, and the antioxidant activity, both in leaves and drupes (green and black) in each cultivar. Total phenolic content, in new season leaves, ranged between 1.01 mg GAE/g ('Adramytini') and 2.06 mg GAE/g ('Konservolia'), while the antioxidant activity ranged between 157.64 ppm ('Konservolia') and 285.80 ppm ('Adramytini'). In green drupes, total phenolic content ranged between 0.59 mg GAE/g ('Megaritiki') and 1.98 mg GAE/g ('Mastoidis') while the antioxidant activity ranged between 119.66 ppm ('Lianolia Kerkyras') and 496.45 ppm ('Megaritiki'). Total phenolic content in black drupes ranged between 0.54 mg GAE/g ('Gaidourelia') and 0.99 mg GAE/g ('Lianolia Kerkyras'), while the antioxidant activity ranged between 284.23 ppm ('Lianolia Kerkyras') and 886.36 ppm ('Chalkidiki'). The HPLC analysis showed the presence of flavonoids, hydroxycinnamic derivatives and secoiridoids. In leaves the most abundant compounds were oleuropein, luteolin-7-o-glucoside and rutin while luteolin-4-o-glucoside, hydroxytyrosol and caffeic acid were detected in lower amounts. In drupes the most abundant compounds were verbascoside and oleuropein.
Journal of the American Oil Chemists' Society, 2009
Olive leaves are a very abundant vegetable material containing various phenolic compounds, such as secoiridoids and flavonoids, that are expected to exert strong antioxidant capacity. However, little is known about the variation of olive-leaf phenolic composition during maturation and its influence on antioxidant capacity. To answer this question, young and mature Olea Europaea L. leaves were submitted to successive extraction with dichloromethane, ethyl acetate, and methanol, then characterized by ESI-MS. It appeared that mature olive-leaf extracts contained higher levels of verbascoside isomers and glucosylated forms of luteolin, while young ones presented higher contents of oleuropein, ligstroside, and flavonoid aglycones. Moreover, antioxidant capacity evaluation using our newly developed conjugated autoxidizable triene assay showed that, in a lipid-based emulsified system, this phenolic composition variation leads to a change in the ability of extracts to counteract lipid oxidation. Mature olive-leaf extracts exhibit higher antioxidant capacity than young olive-leaf extracts. This result enables us to hypothesize that two main bioconversion scenarios may occur during maturation of olive leaves, which could explain changes observed in antioxidant capacity: (1) a bioconversion of oleuropein and ligstroside into verbascoside isomers and oleuroside, and (2) a bioconversion of flavonoid aglycones into glucosylated forms of luteolin. Finally, this study leads to a better understanding of the relationship between phenolic profile and antioxidant capacity of olive leaves.