Effect of Extraction Conditions on the Antioxidant Activity of Olive Wood Extracts (original) (raw)
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Journal of Chemistry and Biochemistry, 2016
Olive leaves are being used in the last decades as a potential source of beneficial compounds in medicines, cosmetics, and food industry. In this work a comparison between Palestinian wild and cultivated olive leaves extracts obtained using different solvent systems under different conditions was performed. The crude extracts were studied for their total phenol and oleuropein content, in addition to their antioxidant activity which was evaluated using DPPH free radical scavenging method and by studying their effect in stabilization of olive oil samples towards oxidation. The stability of olive oil samples enriched with extract additives was estimated by measuring peroxide values, absorption coefficients K270 and K232. The results showed that olive oil stabilizing effect of crude extract was higher than that of commonly used synthetic antioxidants such as BHT. The wild leaves extracts exhibited higher levels of DPPH inhibition than cultivated. The metabolic extract of cultivated olive leaves at pH 7 has higher total phenol content and exhibits better oil stabilizing effect in comparison to other extracts. The identification and quantization of the major phenol component of these extracts (oleuropein) was performed using TLC and HPLC. It was shown that wild olive leaves have higher oleuropein content (23.9%) than cultivated which have oleuropein content of (6.8%). The highest oleuropein content was found in wild olive leaves extract by using methanol-water 80:20 at pH = 3 and 48 h.
Composition of the olive tree bark: Richness in oleuropein
The types and quantities of phenolics, considered as a main group of natural antioxidants, vary in different olive matrices (leaves, fruit, stones, seeds, bark, and paste). However, comparative studies of different extracted amounts of such material are scarce in literature. This manuscript deals with the partition of extracted phenolic compounds mainly oleuropein in olive leaf and bark through hydrodistillation experiments. The analysis of the extracted compounds was performed using HPLC techniques. We notice that the olive bark contains a considerable amount of oleuropein, exceeding twice the amount that was extracted from the leaves.
Agronomy
Leaves from Olea europaea represent one of the main by-products of the olive oil industry, containing a plethora of bioactive compounds with several promising activities for human health. An organic solvent-free extraction method was developed for the recovery of olive leaf phenols, which obtained an extract containing oleuropein in high amounts. A comparison of various extraction media is reported, together with the total phenolic content, DPPH (2,2-Diphenyl-1-picrylhydrazyl) content, ORAC (oxygen radical absorbance capacity), and polyphenol oxidase activity of the corresponding extracts. The polyphenol profiles and content of the most representative extracts have also been studied. Extraction solvent and temperature significantly influenced the phenolic content and antioxidant activity of the extracts, with hot water representing the solvent of election for the extraction of bioactive compounds from this matrix. All the extracts obtained showed reasonably high total phenol content...
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.
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.
Composition and Antioxidant Activity of Olive Leaf Extracts from Greek Olive Cultivars
Journal of the American Oil Chemists' Society, 2010
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.
Chemico-biological Interactions, 2008
Oleuropein-rich extracts from olive leaves and their enzymatic and acid hydrolysates, respectively rich in oleuropein aglycone and hydroxytyrosol, were prepared under optimal conditions. The antioxidant activities of these extracts were examined by a series of models in vitro. In this study the lipid-lowering and the antioxidative activities of oleuropein, oleuropein aglycone and hydroxytyrosol-rich extracts in rats fed a cholesterol-rich diet were tested. Wistar rats fed a standard laboratory diet or cholesterol-rich diets for 16 weeks were used. The serum lipid levels, the thiobarbituric acid reactive substances (TBARS) level, as indicator of lipid peroxidation, and the activities of liver antioxidant enzymes (superoxide dismutase (SOD) and catalase (CAT)) were examined. The cholesterol-rich diet induced hyperlipidemia resulting in the elevation of total cholesterol (TC), triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C). Administration of polyphenol-rich olive leaf extracts significantly lowered the serum levels of TC, TG and LDL-C and increased the serum level of high-density lipoprotein cholesterol (HDL-C). Furthermore, the content of TBARS in liver, heart, kidneys and aorta decreased significantly after oral administration of polyphenol-rich olive leaf extracts compared with those of rats fed a cholesterol-rich diet. In addition, these extracts increased the serum antioxidant potential and the hepatic CAT and SOD activities. These results suggested that the hypocholesterolemic effect of oleuropein, oleuropein aglycone and hydroxytyrosol-rich extracts might be due to their abilities to lower serum TC, TG and LDL-C levels as well as slowing the lipid peroxidation process and enhancing antioxidant enzyme activity.
Isolation and identification of radical scavengers in olive tree (Olea europaea) wood
Journal of Chromatography A, 2006
Several extracts of Olea europaea wood (Picual olive cultivar) were obtained with solvents of different polarity and their antioxidant activities determined. The active compounds were detected in fractions of an ethyl acetate extract using HPLC with on-line radical scavenging detection. After applying different separation techniques, hydroxytyrosol, tyrosol, cycloolivil, 7-deoxyloganic acid, oleuropein and ligustroside were isolated and characterized. Hydroxytyrosol showed a higher activity than the natural antioxidant rosmarinic acid in scavenging the DPPH model radical. Cycloolivil and oleuropein showed stronger activities than the synthetic antioxidant BHT against the same radical. Ligustroside, tyrosol and 7-deoxyloganic acid showed little activity. The latter compound has not been previously identified in the genus Olea.
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.