Composition and Antioxidant Activity of Olive Leaf Extracts from Greek Olive Cultivars

• Published in: Journal of the American Oil Chemists' Society Vol. 87; no. 4; pp. 369 - 376
• Main Authors: Kiritsakis, Kostas, Kontominas, M. G, Kontogiorgis, C, Hadjipavlou-Litina, D, Moustakas, A, Kiritsakis, A
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Berlin/Heidelberg : Springer-Verlag 01.04.2010; Springer-Verlag; Springer; Springer Nature B.V
• Subjects: Agriculture; Antioxidant activity; Antioxidants; Biological and medical sciences; Biomaterials; Biotechnology; chemical analysis; chemical constituents of plants; Chemistry; Chemistry and Materials Science; Cultivars; DPPH; enzyme inhibition; Fat industries; Food industries; Food Science; Free radical scavenging; Fruit trees; Fundamental and applied biological sciences. Psychology; Industrial Chemistry/Chemical Engineering; Leaves; lipoxygenase; Lipoxygenase activity; Methanol; Oils & fats; Olea europaea; Olive leaves; Olive oil; olives; Original Paper; oxidative stability; Phenolic components; phenolic compounds; Phenols; Plant extracts; Polarity; Solvents; Soybeans; Studies; Temperature; Greece; Free radical scavenging; Lipoxygenase activity; DPPH; Phenolic components; Antioxidant activity; Olive leaves; Olive leavens; Oleaceae; Olea europaea; Enzyme; Extract; Plant leaf; Antioxidant; Free radical; Oils and fats industry; Olive; Dicotyledones; Angiospermae; Phenols; Spermatophyta; Chemical composition; Oxidoreductases; Lipoxygenase
• ISSN: 0003-021X; 1558-9331
• DOI: 10.1007/s11746-009-1517-x

The olive leaf phenolic composition of the Greek cultivars koroneiki, megaritiki and kalamon was determined using LC/MS. Furthermore, the antioxidant activity of olive leaf extracts from the above three cultivars, using solvents of increasing polarity (petroleum ether, dichloromethane, methanol and methanol/water: 60/40) was evaluated using the stable free radical diphenylpicrylhydrazyl (DPPH) test. Furthermore the oxidative stability index (OSI) was compared to that of the synthetic antioxidant TBHQ and commercial oleoresin (rosemary extract). The ability of phenolic compounds to inhibit the lipoxygenase (LOX) activity was also investigated. The ten main components determined in the olive tree leaf extracts for the cultivars koroneiki and kalamon were: secologanoside, dimethyloleuropein, oleuropein diglucoside, luteolin-7-O-glucoside, rutin, oleuropein, oleuroside, quercetin, ligstroside and verbascoside. Respective compounds for the cultivar megaritiki were: secologanoside, dimethyloleuropein, oleuropein diglucoside, luteolin7-O-glucoside, oleuropein, oleuroside, quercetin and ligstroside. In all three cultivars, oleuropein represented the main phenolic component. The solvent polarity influenced the total amount of the phenolic compounds determined. When methanol/water (60/40) was used, as solvent, more phenolic compounds were determined. The total amounts of phenols determined in the extracts, obtained by successive extractions using the above solvents, were 6,094, 5,579 and 6,196 mg/kg (mg gallic acid/kg dried olive leaves) for the cultivars megaritiki, kalamon and koroneiki, respectively. Among all extracts, methanol/water extracts exhibited the highest antioxidant activity as shown through the application of the DPPH and OSI methods. The OSI antioxidant activity followed the sequence: synthetic antioxidant TBHQ > commercial oleoresin > olive tree leaf extracts > control. Likewise, methanol/water olive leaf extracts significantly inhibited soybean lipoxygenase, although some small differences in the activity among the olive leaf extracts of the different cultivars were observed. The solvent polarity as well as the amount of the extract influenced the inhibitory activity. A positive correlation was shown between the antioxidant activity of leaf extracts and the total phenol content.