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Isolation and evaluation of antioxidants from leaves of a Tunisian cultivar olive tree
Author(s) -
Bouaziz Mohamed,
Sayadi Sami
Publication year - 2005
Publication title -
european journal of lipid science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.614
H-Index - 94
eISSN - 1438-9312
pISSN - 1438-7697
DOI - 10.1002/ejlt.200501166
Subject(s) - oleuropein , hydroxytyrosol , chemistry , luteolin , olea , chromatography , rutin , high performance liquid chromatography , apigenin , phenols , column chromatography , polyphenol , food science , antioxidant , flavonoid , botany , organic chemistry , biology
Abstract Quantitative and qualitative determinations of phenolic compounds were carried out on Chemlali olive leaves, a by‐product of olive tree pruning. The evolution of the amount of the major phenolic compound was monitored from July 2003 to March 2004. Quantitative analysis was performed by high‐performance liquid chromatography (HPLC), which revealed that oleuropein was always the major compound. Its concentration reached 6.8 g per 100 g of fresh olive leaves, while monomeric phenols were the minor compounds. Beside oleuropein, six flavonoids (luteolin 7‐ O ‐glucoside, luteolin 7‐ O ‐rutinoside, apigenin 7‐ O ‐glucoside, rutin, luteolin and apigenin) were identified. The identification was based on separation by HPLC equipped with a diode array detector, followed by liquid chromatography‐mass spectrometry analysis. A relative high amount of purified hydroxytyrosol (2.3 g per 100 g of fresh olive leaves) was obtained in short time by a simple hydrolysis reaction of Olea europaea leaf extract and by purification using a C‐18 silica gel column. The antioxidant activities of the extracts and the purified compounds were evaluated by measuring the radical‐scavenging effect on 1,1‐diphenyl‐2‐picrylhydrazyl and by using the β‐carotene linoleate model assay. Hydroxytyrosol and hydrolysate products have the highest antioxidant activities.