Simultaneous separation and purification of flavonoids and oleuropein from Olea europaea L. (olive) leaves using macroporous resin

BACKGROUND: This study developed a feasible process to simultaneously separate and purify polyphenols, including flavonoids and oleuropein, from the leaves of Olea europaea L. Macroporous resins were used as the separation and purification materials. The performance and separation capabilities of eight resins (D101, DM130, HPD450, LSA‐21, LSA‐40, 07C, LSD001 and HPD600) were systematically evaluated. The contents of target polyphenols in different extracts were determined using ultraviolet (for flavonoids) and high‐performance liquid chromatographic (for oleuropein) methods. The static adsorption and desorption results showed that resin LSA‐21 had better adsorption properties among the eight resins. Influential factors such as extraction method, pH value of feeding solution, desorption solution, adsorption kinetics and adsorption isotherm, etc. to the extraction and purification of these polyphenols were successively investigated on resin LSA‐21. RESULTS: The target flavonoids and oleuropein were selectively purified using resin LSA‐21. Compared with the contents in raw leaves, the contents of total flavonoids and oleuropein in the final purified products were increased 13.2‐fold (from 16 to 211 g kg^?1) and 7.5‐fold (from 120 to 902 g kg^?1) with recovery yields of 87.9% and 85.6%, respectively. CONCLUSION: This extraction and purification method could be used in the large‐scale enrichment or purification of flavonoids, oleuropein and other polyphenols from O. europaea L. leaves or other herbal materials in industrial, food processing and medical manufacture. Copyright © 2011 Society of Chemical Industry     

Human absorption and metabolism of oleuropein and hydroxytyrosol ingested as olive (Olea europaea L.) leaf extract

Phenolic compounds derived from the olive plant (Olea europaea L.), particularly hydroxytyrosol and oleuropein, have many beneficial effects in vitro. Olive leaves are the richest source of olive phenolic compounds, and olive leaf extract (OLE) is now a popular nutraceutical taken either as liquid or capsules. To quantify the bioavailability and metabolism of oleuropein and hydroxytyrosol when taken as OLE, nine volunteers (five males) aged 42.8 ± 7.4 years were randomized to receive either capsulated or liquid OLE as a single lower (51.1 mg oleuropein, 9.7 mg hydroxytyrosol) or higher (76.6 mg oleuropein, 14.5 mg hydroxytyrosol) dose, and then the opposite strength (but same formulation) a week later. Plasma and urine samples were collected at fixed intervals for 24 h post‐ingestion. Phenolic content was analyzed by LC‐ESI‐MS/MS. Conjugated metabolites of hydroxytyrosol were the primary metabolites recovered in plasma and urine after OLE ingestion. Peak oleuropein concentrations in plasma were greater following ingestion of liquid than capsule preparations (0.47 versus 2.74 ng/mL; p = 0.004), but no such effect was observed for peak concentrations of conjugated (sulfated and glucuronidated) hydroxytyrosol (p = 0.94). However, the latter peak was reached earlier with liquid preparation (93 versus 64 min; p = 0.031). There was a gender effect on the bioavailability of phenolic compounds, with males displaying greater plasma area under the curve for conjugated hydroxytyrosol (11 600 versus 2550 ng/mL; p = 0.048). All conjugated hydroxytyrosol metabolites were recovered in the urine within 8 h. There was wide inter‐individual variation. OLE effectively delivers oleuropein and hydroxytrosol metabolites to plasma in humans.     

Comparison of microwave,ultrasonic and conventional techniques for extraction of bioactive compounds from olive leaves (Olea europaea L.)

The aim of this study was to evaluate the effects of different extraction parameters on total phenolic (TP) compounds and antioxidant activity (AA) from olive leaves (Olea europaea L.) using microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE) and maceration. The study also emphasized on the optimization of MAE and UAE conditions, and on the potential benefits of using MAE as a pretreatment to UAE. It was demonstrated that olive leaves were a good source of phenolic compounds with high antioxidant activity. MAE at a higher temperature (86 °C) was more efficient in terms of TP yield, with short extraction time (3 min). MAE performed with water as a solvent was effective in disrupting the olive leaf cells thereby promoting the release of the compounds. Under this condition, the TP yield was increased by 82% when compared to maceration. In addition, it was demonstrated that MAE used as a pretreatment to UAE was more efficient.Industrial relevanceOlive leaves are usually considered as a residue with huge potential for value addition. High added-value compounds can be obtained by recovering phytochemicals from olive leaves for valorization through food products. The extraction of the bioactive compounds requires efficient techniques, but only a few studies show good extraction yields using clean techniques. Microwave-assisted extraction is a method for the extraction of bioactive compounds, which utilizes microwave energy to produce voluminous heating and the reduction of extraction time is one of the most attractive advantages of the system. In addition, the potential benefit of using microwave-assisted extraction as a pretreatment to ultrasound-assisted extraction to improve the recovery of bioactive compounds was reported and can be used as a means of intensifying the extraction process.     

Flavonoids in three olive (Olea europaea) fruit varieties during maturation

The objective of the present paper was the characterisation of olive fruit varieties through the formation and variation during maturation of their flavonols, flavones and anthocyanins. An olive variety with a constant cyanidin-3-rutinoside:cyanidin-3-glucoside ratio of 1 exhibited lower contents of luteolin-7-glucoside and quercetin-3-rutinoside than varieties in which the only anthocyanin detected was cyanidin-3-rutinoside.     

Sugar and polyol compositions of some European olive fruit varieties (Olea europaea L.) suitable for table olive purposes

An experimental investigation was carried out on olive fruits of Douro, Hojiblanca, Cassanese, Taggiasca and Thasos cultivars, to assess free sugar and polyol compositions and their changes during ripening and processing. TMS ethers of sugars from olive pulp were analysed by GC and GC–MS and identification of each sugar component was obtained by comparison of retention times and mass spectra with those of authentic compounds. Quantitation of sugars was performed on mixture whose tautomeric equilibria were stable. Glucose, fructose and galactose were the main sugars found in olive pulp. Appreciable quantities of mannitol were also present. Sucrose and inositol were present in very low concentrations. A significant correlation (r=0.941) between mannitol and oil contents was found. Sugar content decreased from green to cherry and black colour, according to the stage of ripeness of fruits. In processed olive-fruits, sugar contents varied among olive cultivars according to processing conditions.     

Effect of ripening on the mechanical properties of Portuguese and Spanish varieties of olive (Olea europaea L)

The mechanical properties of the table olive, Hojiblanca and Douro varieties from Spain and Portugal respectively, were determined. The results showed that in a tensile test the skin was stronger and stiffer than the flesh. This was also reflected by the strain at failure of the two tissues, the skin being less deformable than the flesh. During ripening, the strength of both skin and flesh of Hojiblanca decreased, whereas the skin and flesh of Douro increased and decreased in strength respectively. In general, Hojiblanca tissues were stronger than Douro tissues. A softening phenomenon was detected during ripening in the flesh of both varieties. The stiffness of the skin of Hojiblanca decreased significantly during ripening, whereas that of the skin of Douro increased but to a lesser extent. However, in general, the skin and flesh of Hojiblanca were stiffer than those of Douro. A cutting test enabled the determination of skin and flesh toughness. However, it is suggested that the flesh contributed to the measurement of skin toughness in the early stages of ripening, as reported for other commodities. The flesh of Hojiblanca was tougher than that of Douro, with both decreasing in toughness during ripening. © 2001 Society of Chemical Industry     

Preliminary studies by visible and near‐infrared reflectance spectroscopy of juvenile and adult olive (Olea europaea L.) leaves

The spectral properties of olive leaves were studied by visible and near‐infrared spectroscopy to discriminate between the juvenile and adult origin of leaf samples. Spectral data from 400 to 2500 nm were recorded on 18 leaf samples from juvenile (6) and adult (12) seedling plants using four different sample presentations to the instrument. Spectra of leaves were remarkably similar owing to dominant features related to absorption by photosynthetic pigments (visible) and water (near‐infrared), although high variability was observed for all the sample presentations tested. The fibre‐optic probe presentation provided the best procedure as it maximised (in relative terms) the spectral variability attributable to differences between seedlings and minimised that arising from the sampling procedure. Principal component analysis (PCA) performed with average values per seedling showed that two groups can be clearly observed according to the origin (juvenile or adult) of the samples. This method could provide a rapid screening technique useful as a selection tool in olive breeding programmes. Copyright © 2006 Society of Chemical Industry     

Antioxidant properties of various solvent extracts of mulberry (Morus indica L.) leaves

The antioxidant properties and total phenolic contents of methanol, acetone and water extracts of mulberry (Morus indica L.) leaves were examined. Various experimental models including iron (III) reducing capacity, total antioxidant capacity, DPPH radical scavenging activity and in vitro inhibition of ferrous sulphate-induced oxidation of lipid system were used for characterization of antioxidant activity of extracts. The three extracts showed varying degrees of efficacy in each assay in a dose-dependent manner. Methanolic extract with the highest amount of total phenolics, was the most potent antioxidant in all the assays used. In addition, the effect of temperature (50 °C and 100 °C), pH (3, 5, 7, 9 and 11) and storage (5 °C) on the antioxidant activity of methanolic extract was investigated. The antioxidant activity of the extract remained unchanged at 50 °C and was maximum at neutral pH. The extract stored at 5 °C in the dark was stable for 30 days after which the antioxidant activity decreased (p ? 0.05) gradually. On the basis of the results obtained, mulberry leaves were found to serve as a potential source of natural antioxidants due to their marked antioxidant activity.     

Olive tree (Olea europaea L.) leaf as a waste by‐product of table olive and olive oil industry: a review

Research into finding new uses for by‐products of table olive and olive oil industry are of great value not only to the economy but also to the environment where olives are grown and to the human health. Since leaves represent around 10% of the total weight of olives arriving at the mill, it is worth obtaining high added‐value compounds from those materials for the preparation of dietary supplements, nutraceuticals, functional food ingredients or cosmeceuticals. In this review article, olive tree (Olea europaea L.) leaf is reviewed as being a potential inexpensive, renewable and abundant source of biophenols. The importance of this agricultural and industrial waste is emphasised by means of describing its availability, nutritional and therapeutic effects and studies conducted on this field. © 2017 Society of Chemical Industry     

Polyphenol oxidase activity of two olive (Olea europaea L.) cultivars as an early criterion of Mn toxicity

BACKGROUND: The time course of polyphenol oxidase (PPO) activity in the leaves of two olive cultivars (Picual and FS‐17) irrigated with nutrient solutions differing in Mn concentration (0, 2 and 1280 µmol L^?1) was studied under hydroponic conditions to determine whether PPO activity could be used as an early criterion of Mn status of olive plants, and to elucidate whether genotypic differences exist between the two olive cultivars studied, concerning the effect of Mn concentration on PPO activity. RESULTS: In all the Mn treatments, PPO activity was greater in Picual than in FS‐17. Under excess Mn (1280 µmol L^?1), PPO activity gradually increased with time, starting from day 30 of the experiment in both cultivars, and this increase preceded the appearance of Mn toxicity symptoms. In contrast, in the other two Mn treatments (0 and 2 µmol L^?1) PPO activity increased and afterwards decreased during the experiment, but the trend was not clear. In the 1280 µmol L^?1 treatment, PPO activity linearly increased (R = 0.8836 for Picual and 0.943 for FS‐17) with the increase of Mn concentration in the leaves of both cultivars. In the 1280 µmol L^?1 Mn treatment, PPO activity was negatively related with Fe and Zn concentrations in the leaves, and positively in the 0 and 2 µmol L^?1 Mn treatments with the Ca, Mg and K concentrations. CONCLUSION: From the differential time course of PPO activity in the three Mn treatments (0, 2 and 1280 µmol L^?1), it is concluded that periodic measurements of PPO activity in the leaves of the olive cultivars Picual and FS‐17 can be used for the early detection of Mn toxicity (before the appearance of symptoms). Copyright © 2010 Society of Chemical Industry     

Composition and organoleptic characteristics of oil from Arbequina olive (Olea europaea L) trees under deficit irrigation

This study evaluated the effects of different regulated deficit irrigation (RDI) strategies applied to olive (Arbequina cultivar) trees on the qualitative and quantitative parameters of the resulting oil during the maximum evaporative demand period for three consecutive crop seasons. Quality indices, fatty acid composition, pigments, colour, α‐tocopherol and phenolic contents, bitter index, oxidative stability and organoleptic properties of the oil were determined. Irrigation did not affect those parameters used as criteria for classifying olive oil in its commercial grades. Only polyphenol and o‐diphenol contents and, consequently, the bitter index and oxidative stability were affected by the RDI strategy, with increasing values as the water applied decreased. Regulated deficit irrigation resulted in important savings in irrigation requirements without detriment to oil quality. © 2002 Society of Chemical Industry     

Microcomponents of olive oil. Part II: Digalactosyldiacylglycerols from Olea europaea

Two galactolipids, 1 and 2, were isolated and identified both in olive fruits and in olive oil. They are characterized by a low polarity, despite the presence of a diglycosidic unit, giving, in water, micelles. Because of this characteristic, compounds 1 and 2 could be responsible for the stability of the light emulsion typical of freshly produced olive oil. The presence of hydrophilic ortho-diphenolic compounds enhances the antioxidant properties of this oil, particularly in the first period after the production. In addition, the functions present in 1 and 2 are susceptible to hydrolysis and may be easily modified in the alkaline treatment used for the olive oil refining process. For this reason, their presence in olive oil may be a very useful indication of the untreated food product.     

Effect of dietary olive leaves (Olea europaea L.) on lipid and protein oxidation of refrigerated stored n‐3‐enriched pork

The objective of this study was to evaluate the effect of dietary olive leaves versus α‐tocopheryl acetate on lipid and protein oxidation of raw and cooked longissimus dorsi muscle from pigs fed diets supplemented with fish oil. Enrichment of pork with the very long chain n‐3 fatty acids increased (P ≤ 0.05) lipid oxidation in both raw and cooked chops during refrigerated storage, and decreased (P ≤ 0.05) the sensory attributes of the cooked chops, but had no effect (P > 0.05) on protein oxidation of both raw and cooked chops. Dietary olive leaves or α‐tocopheryl acetate had no effect (P > 0.05) on the fatty acid composition but decreased (P ≤ 0.05) lipid oxidation while exerting no effect (P > 0.05) on protein oxidation in both raw and cooked chops during refrigerated storage. In addition, dietary olive leaves at 10 g kg^?1 feed and α‐tocopheryl acetate at 200 mg kg^?1 feed exerted (P ≤ 0.05) a beneficial effect on the sensory attributes of cooked n‐3‐enriched chops.     

DNA diversity in olive (Olea europaea L.) and its relationships with fatty acid,biophenol and sensory profiles of extra virgin olive oils

Olive (Olea europaea L.) is gaining importance worldwide primarily for the production of virgin olive oil (VOO), the main lipid source of the Mediterranean diet.We evaluated the genetic diversity of 20 traditional varieties of Southern Italy using 10 SSR markers. We also produced 382 monovarietal extra virgin olive oils (EVOOs) from the same varieties and studied their chemical profiles by analysing 13 fatty acids (FAs) and 6 olive biophenols (OBPs). In addition, the sensory profile of EVOOs was also assessed.Significant differences among the 20 varieties were found in terms of DNA polymorphism, chemical composition and sensory profile of the EVOOs, highlighting that the genetic variability in olive is detected also in different EVOO features. The chemical variation of EVOOs throughout different years suggested a genotype-specific level of environmental stability and adaptation. The comparison of pairwise distances between varieties obtained by genetic, chemical and sensory data indicated a significant correlation of sensory attributes with the other parameters.The genetic and EVOO composition data underlined the significant diversity present in the varieties under investigation, suggesting that traditional varieties specialized to particular environmental conditions have distinctive, unexplored features. Our work also shows the efficacy of establishing integrated compositional databases as a means to make evident differences among VOOs from traditional varieties. This multidisciplinary information is highly useful to differentiate origin-linked products from others of the same category.     

油橄榄叶提取物中橄榄苦苷稳定性及对亚铁离子的螯合作用

研究了不同光源、pH、温度和时间对油橄榄叶提取物(OLE)中橄榄苦苷稳定性的影响及对亚铁离子的螯合作用实验结果表明,橄榄苦苷对光较稳定,与酸性环境相比,在碱性条件下易降解;通过TG-DSC图分析可知,在温度为232.3℃下,橄榄苦苷开始发生分解,且分解过程是一个放热过程 橄榄苦苷随着时间的延长,降解率逐渐增大;25℃27d,橄榄苦苷的降解率达95.24％,4℃ 27d,橄榄苦苷降解率为38.1％,这些降解原因与其含有的β-葡萄糖苷酶有关在提取液沸腾5min灭酶后,橄榄苦苷在30d内没有降解此外,通过亚铁离子的螯合实验可知,油橄榄叶提取物对亚铁离子的螯合作用较强,在浓度为1.2mg/mL时,螯合率约为20％,明显低于EDTA (95.24％)的螯合作用.     

油橄榄叶提取物中橄榄苦苷稳定性及对亚铁离子的螯合作用

研究了不同光源、pH、温度和时间对油橄榄叶提取物（OLE）中橄榄苦苷稳定性的影响及对亚铁离子的螯合作用。实验结果表明,橄榄苦苷对光较稳定,与酸性环境相比,在碱性条件下易降解;通过TG-DSC图分析可知,在温度为232.3℃下,橄榄苦苷开始发生分解,且分解过程是一个放热过程。橄榄苦苷随着时间的延长,降解率逐渐增大;25℃27d,橄榄苦苷的降解率达95.24%,4℃27d,橄榄苦苷降解率为38.1%,这些降解原因与其含有的β-葡萄糖苷酶有关。在提取液沸腾5min灭酶后,橄榄苦苷在30d内没有降解。此外,通过亚铁离子的螯合实验可知,油橄榄叶提取物对亚铁离子的螯合作用较强,在浓度为1.2mg/mL时,螯合率约为20%,明显低于EDTA（95.24%）的螯合作用。