Isolation and identification of radical scavengers in olive tree (Olea europaea) wood (original) (raw)
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On-line HPLC–DAD–radical scavenging Oleuropein-3 00-methyl ether a b s t r a c t The woody portion of olive tree pruning is a source of natural antioxidants of potential interest for the food industry. This work deals with the isolation and identification of further antioxidants present in an ethyl acetate extract of olive (Olea europaea L.) wood. Thus, a new secoiridoid, oleuropein-3 00-methyl ether (1), together with six known secoiridoids, 7 00 S-hydroxyoleuropein (2), jaspolyanoside (3), ligustro-side 3 0-O-b-D-glucoside (4), jaspolyoside (5), isojaspolyoside A (6) and oleuropein 3 0-O-b-D-glucoside (7) were isolated by combining HPLC with fast on-line post-column radical scavenging activity evaluation. The structures of these compounds were determined by spectroscopic methods. The antioxidant activity of the pure compounds was determined by measuring the radical scavenging activity against 2,2-diphe-nyl-1-picrylhydrazyl radical (DPPH Å). Compounds 2, 5 and 7 displayed a higher antioxidative effect than the synthetic antioxidant BHT and lower than rosmarinic acid, whereas compounds 3 and 4 showed weak DPPH Å scavenging activity.
Effect of Extraction Conditions on the Antioxidant Activity of Olive Wood Extracts
An investigation to optimize the extraction yield and the radical scavenging activity from the agricultural by-product olive tree wood (Olea europaea L., cultivar Picual) using six different extraction protocols was carried out. Four olive wood samples from different geographical origin, and harvesting time have been used for comparison purposes. Among the fifty olive wood extracts obtained in this study, the most active ones were those prepared with ethyl acetate, either through direct extraction or by successive liquid-liquid partitioning procedures, the main components being the secoiridoids oleuropein and ligustroside. An acid hydrolysis pretreatment of olive wood samples before extractions did not improve the results. In the course of this study, two compounds were isolated from the ethanolic extracts of olive wood collected during the olives' harvesting season and identified as (7 R)-7ethoxyoleuropein (1) and (7 S)-7 -ethoxyoleuropein (2).
Journal of Agricultural and Food Chemistry, 2010
The contribution of flavonoids to the overall radical scavenging activity of olive leaf polar extracts, known to be good sources of oleuropein related compounds, was examined. Off line and on line HPLC-DPPH • assays were employed, whereas flavonoid content was estimated colorimetrically. Individual flavonoid composition was first assessed by RP-HPLC coupled with diode array and fluorescence detectors and verified by LC-MS detection system. Olive leaf was found a robust source of flavonoids regardless sampling parameters (olive cultivar, leaf age or sampling date). Total flavonoids accounted for the 13-27% of the total radical scavenging activity assessed using the on line protocol. Luteolin 7-O-glucoside was one of the dominant scavengers (8-25%). Taking into consideration frequency of appearance the contribution of luteolin (3-13%) was considered important, too. Our findings support that olive leaf, except for oleuropein and related compounds, is also a stable source of bioactive flavonoids.
Antioxidant activity of phenolics extracted from Olea europaea L. leaves
Food Chemistry, 2000
The purpose of this study was to identify the main phenolic compounds present in an olive leaf extract (OL) in order to delineate the dierential antioxidant activities of these compounds through the extent of their abilities to scavenge the ABTS + radical cation and to clarify the structural elements conferring antioxidant capacity in aqueous systems. The results show that the relative abilities of the¯avonoids from olive leaf to scavenge the ABTS + radical cation are in¯uenced by the presence of functional groups in their structure, mainly the B-ring catechol, the 3-hydroxyl group and the 2,3-double bond conjugated with the 4-oxo function. For the other phenolic compounds present in OL, their relative abilities to scavenge the ABTS + radical cation are mainly in¯uenced by the number and position of free hydroxyl groups in their structure. Also, both groups of compounds show synergic behaviour when mixed, as occurs in the OL. #
Journal of Food Science and Technology, 2018
The leaves of seventeen cultivars of olive growing in the north of Iran were investigated for total phenol content and antioxidant activity. The identification and quantification of main phenolic compounds were performed by reverse phase high performance liquid chromatography with diode array detector. The cultivars Kalamon, Gordal, and Coratina contained the highest concentration of phenolic compounds (190.65 ± 0.03, 184.72 ± 0.001, and 155.91 ± 0.06 mg GAE/g extract, respectively). The maximum radical scavenging activities were found in Gordal, Coratina, and Kalamon extracts (IC 50 20.66, 22.95, and 26.74 lg ml-1 , respectively). The extracts of Mishen, Fishomi, and Arbequina (1971.37 ± 0.007, 1794.57 ± 0.001, and 1760.57 ± 0.005 lmol Fe II/g dried extract, respectively) showed highest antioxidant activity in FRAP assay. The identification analysis demonstrated the present of vanillin, rutin, luteolin 7-O-glucoside, oleuropein, and quercetin. The highest oleuropein concentrations were detected in cultivars Mishen, Beleidi, Kalamon, and Roghani while it was not detected in cultivars Conservolea, Amigdalolia, Leccino, and Fishomi.
European Food Research and Technology, 2008
In this research, a phenol extract of high hydroxytyrosol (OLPE) content was obtained from olive leaves (Olea europaea L.), and subsequently tested under different contexts. The method used to obtain the OLPE basically involved two steps: the use of strongly-acid aqueous steam, generated from 10% HCl (v/v) at 100°C, to directly hydrolyse the native complex phenols from integral olive leaves, and OLPE recovery by liquid–liquid extraction with ethyl acetate. Hydrolysis time was 1 h. Finally, the dried extract was dissolved in distilled water. The OLPE total phenols were determined by Folin–Ciocalteu’s method and by HPLC analysis. Hydroxytyrosol was about 92% of the total phenols present in OLPE, and the yield was about 0.2% on fresh leaves. OLPE showed antioxidant effects on different food lipids and did not inhibit lactic acid bacteria growth; however, it showed cytotoxicity on NIH/3T3 fibroblasts and human umbilical vein endothelial cells at concentrations higher than 0.32 mM (as hydroxytyrosol).
Antioxidant activities and phenolic composition of Olive (Olea europaea) leaves
The present study compares the antioxidant activities of leaves of eight cultivars of olive. The aqueous extracts of leaves showed inhibition against thiobarbituric acid reactive species (TBARS) induced by pro-oxidant (10 μM FeSO 4) in mice liver. The order of the antioxidant activity among cultivars on lipid peroxidation assay is Gemlik > Frantio > Doleca-Agogia > Moriolo > Mission > Uslu > Leccino > Carotina. Different varieties of olive showed good antioxidant properties, IC 50 values ranged between 22.46 to 198 μg/ml on 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The major phenolic acids, some flavonoid aglycone and glycosides were identified in leaves by high performance liquid chromatography. Ellagic acid (29.80 ± 0.02 mg/g), caffeic acid (15.73 ± 0.01mg/g), gallic acid (15.69 ± 0.01 mg/g), rutin (34.56 ± 0.03 mg/g), quercetin (16.41 ± 0.01 mg/g), epicatechin (11.04 ± 0.01 mg/g) and quercitrin (15.32 ± 0.03 mg/g) were predominant in infusion of olive.
Journal of Food and Nutrition Research, 2018
We here investigate the effects of the application of methyl jasmonate to olive trees on antioxidant composition of olive fruits. Two cultivars (ie, Arbequina and Picual) were evaluated in our study. As a result, the total phenol content increased significantly with the treatment in Arbequina (from 155.89 to 434.22 mg gallic acid kg-1) whereas decreases were observed in Picual (from 338.27 to 127.71 mg gallic acid kg-1). Similarly, decreases in phenolic acid content were measured in Arbequina whilst no effect was observed in Picual olives. However, the contents of oleuropein and hydroxytyrosol did not increase with the pre-harvest methyl jasmonate for both Arbequina and Picual. Also for both cultivars the treatment of the olive trees increased the free radical scavenging activity of the olive fruits (IC 50 from 514.36 to 1125.46 µg/mL in Arbequina and from 611.98 to 114.55 µg/mL in Picual). The results here found are deeply discussed.