Assessment of the anti-inflammatory, analgesic and sedative effects of oleuropein from Olea europaea L

More and more studies show that inflammation, pain and insomnia have become the main common diseases. Effective treatments of inflammation, pain and insomnia have become an issue of primary concern in clinical practice. Oleuropein (OLE), the main phenolic component of Mediterranean extra virgin olive oil, has shown many pharmacological properties. In the present study, the anti-inflammatory effect of OLE was firstly evaluated using RAW264.7 macrophages subjected to stimulation with lipopolysaccharide (LPSC). The results obtained revealed that OLE caused significant and dose-dependent downregulation of nitric (NO), COX-2, inducible NO synthase iNOS, and the inflammation-associated cytokines IL-6 and TNF-α. From the mechanism, the expression of COX-2, cytokines IL-6 and TNF-α OLE is closely related to analgesic and sedation effect. Further evaluations showed significant analgesic and sedative effects of OLE in tail-flick test and sedation test conducted in SD rats in vivo. All these results indicate that OLE has anti-inflammatory, analgesic and sedative effects both in vitro and in vivo.

The efficacy of oleuropein against non-steroidal anti-inflammatory drug induced toxicity in rat kidney

Indomethacin is generally used in clinical therapeutics as a non-steroidal anti-inflammatory drug. However, its use has been limited due to the gastrointestinal and renal toxic effects of this drug. These toxic effects were associated with not only the inhibition of prostaglandin synthesis but also drug-elevated oxidative stress. To ameliorate these toxicities, natural antioxidants can be used as an alternative and/or combination therapies. Therefore, the current study was conducted to assess the renoprotective effects of oleuropein against indomethacin-induced renal damages. Male Sprague-Dawley rats were pretreated with oleuropein (75, 150, and 300 mg/kg), and then treated with indomethacin (25 mg/kg). To evaluate kidney function, serum blood urea nitrogen, uric acid, and creatinine were measured. In addition, prostaglandin E₂ , tumor necrosis factor-alpha, endothelial nitric oxide synthase, caspase-3, oxidant/antioxidant status, and 8-Oxo-2'-deoxyguanosine levels were determined for the antioxidative and anti-inflammatory effects of oleuropein. Tissue sections were also histopathologically assessed. The biochemical and histopathological analysis proved the toxic effects of indomethacin on kidney. However, the pretreatment with oleuropein (300 mg/kg) protects kidney from indomethacin-induced damages. Our study proved that prior administration of oleuropein has renoprotective activity against indomethacin-associated toxicities.

Olive Biophenols Reduces Alzheimer's Pathology in SH-SY5Y Cells and APPswe Mice

Alzheimer's disease (AD) is a major neurodegenerative disease, associated with the hallmark proteinacious constituent called amyloid beta (Aβ) of senile plaques. Moreover, it is already established that metals (particularly copper, zinc and iron) have a key role in the pathogenesis of AD. In order to reduce the Aβ plaque burden and overcome the side effects from the synthetic inhibitors, the current study was designed to focus on direct inhibition of with or without metal-induced Aβ fibril formation and aggregation by using olive biophenols. Exposure of neuroblastoma (SH-SY5Y) cells with Aβ₄₂ resulted in decrease of cell viability and morphological changes might be due to severe increase in the reactive oxygen species (ROS). The pre-treated SH-SY5Y cells with olive biophenols were able to attenuate cell death caused by Aβ₄₂, copper- Aβ₄₂, and [laevodihydroxyphenylalanine (l-DOPA)] l-DOPA-Aβ₄₂-induced toxicity after 24 h of treatment. Oleuropein, verbascoside and rutin were the major anti-amyloidogenic compounds. Transgenic mice (APPswe/PS1dE9) received 50 mg/kg of oleuropein containing olive leaf extracts (OLE) or control diet from 7 to 23 weeks of age. Treatment mice (OLE) were showed significantly reduced amyloid plaque deposition (p < 0.001) in cortex and hippocampus as compared to control mice. Our findings provide a basis for considering natural and low cost biophenols from olive as a promising candidate drug against AD. Further studies warrant to validate and determine the anti-amyloid mechanism, bioavailability as well as permeability of olive biophenols against blood brain barrier in AD.

[Protective effect of picroside Ⅱ on the brain tissue through antioxidation in stroke rats]

Objective: To investigate the effect and mechanisms of picroside Ⅱ on the brain tissue after cerebral ischemia reperfusion(I/R) in rats. Methods: The middle cerebral artery occlusion(MCAO) rat model was established by inserting a monofilament into middle cerebral artery. The experimental rats were treated by injecting picroside Ⅱ intraperitoneally. The modified neurological severity score (mNSS) and body weight were determined before modeling and after reperfusion of 22 h. The cerebral infarct volume was measured by TTC staining and the cerebral water content was measured in rats. At the same time, ROS content and NADPH oxidase activity were detected. The structure of neurons was observed by electron microscope and the mRNA and protein levels of Rac-1 and Nox2 were detected by RT-PCR and Western blotting. Results: After modeling, the mNSS score was significantly increased (12.6±1.3 vs 0, P<0.001), while the body weight was lost (13.3%±2.5% vs 4.9%±0.8%, P<0.01). The cerebral infarct volume increased obviously (33.5%±3.4% vs 0, P<0.001), brain water content increased significantly (81.5%±0.9% vs 77.7%±0.9%, P<0.05) and the structure of neuron was damaged obviously. The protein and mRNA levels of Rac-1 and Nox2 were significantly increased (P<0.05). After treatment with picroside Ⅱ, mNSS score decreased significantly (7.9±0.8 vs 12.6±1.3, P<0.05) and the body weight increased obviously (9.3%±1.1% vs 13.3%±2.5%, P<0.05). The infarct volume of brain was significantly reduced (18.2%±1.9% vs 33.5%±3.4%, P<0.05), brain water content decreased obviously (79.1%±0.7% vs 81.5±0.9%, P<0.05), the morphological structures of neurons was restored, and the expressions of Rac-1 and Nox2 were significantly decreased (P<0.05). Conclusion: It is suggested that picroside Ⅱ could exert antioxidation to protect the brain tissue through inhibiting the expression of Rac-1 and Nox2.

Inhibitory effect of Ligustrum vulgare leaf extract on the development of neuropathic pain in a streptozotocin-induced rat model of diabetes

BACKGROUND

Chronic hyperalgesia and allodynia associated with progressive damage of peripheral neurons are the most prevalent complications of diabetes mellitus. Plants belonging to the family of Oleaceae were traditionally used in folk medicine for the management of diabetes.

HYPOTHESIS/PURPOSE

The aim of this study was to investigate whether an aqueous extract from the leaves of Ligustrum vulgare (common privet) could be useful to target neuropathic pain in a rat streptozotocin (STZ) model of diabetes.

METHODS

The chemical composition of the aqueous extract from privet leaf was characterized with the UHPLC-DAD-MS method and the analytical quantification of its constituents was performed with HPLC-DAD. Mechanical hyperalgesia and allodynia were evaluated with the Randall-Selitto and von Frey tests.

RESULTS

Our investigation revealed the presence of secoiridoids: oleacein (23.48 ± 0.87 mg/g), oleocanthal (8.44 ± 0.08 mg/g), oleuropein (1.50 ± 0.01 mg/g), as well as phenylpropanoids: echinacoside (6.46 ± 0.07 mg/g), verbascoside (4.03 ± 0.04 mg/g) and p-coumaroyl glucarates in the dried aqueous extract of privet leaves. Behavioral data indicated that chronic intraperitoneal administration of the extract (50-200 mg/kg) for 21 days resulted in a decrease in diabetes-induced hyperalgesia and allodynia. Blood glucose levels remained unaltered, while body weight and water intake decreased significantly.

CONCLUSION

The aqueous privet leaf extract could serve useful in facilitating treatment of painful diabetic neuropathy. Additionally, the study showed that the antihyperalgesic activity of Ligustrum vulgare leaf extract is not likely related to its antihyperglycemic properties.

Evaluation of Physicochemical and Antioxidant Properties of Yogurt Enriched by Olive Leaf Phenolics within Nanoliposomes

Olive leaf extract is a rich source of phenolic compounds and oleuropein which is well-known regarding its antioxidant and antimicrobial attributes. However, the mentioned phenolic compounds will lose their beneficial properties during storage and induce undesirable aftertaste in food products. In this study, olive leaf extract-bearing nanoliposomes were produced via the ethanol injection method and using phosphatidyl choline plus cholesterol as the reagents for the wall material. Later, the prepared nanocarriers were examined in regard to their zeta potential, stability, encapsulation efficiency, and particle size. Moreover, the prepared nanoliposome-loaded yogurt samples were examined considering syneresis, antioxidant activity, pH, acidity, color, and sensorial properties. The mean particle size of the fabricated nanoliposomes was in the range of 25-158 nm. Also, the entire formulation had a negative charge. The encapsulation efficiency was between 70.7 to 88.2%. Besides, the application of nanoliposomes in yogurt improved the antioxidant activity, and unlike the yogurt with nonencapsulated olive extract, no significant changes in color and sensorial attributes were observed and even the syneresis rate was minimized. To conclude, olive leaf phenolics can be entrapped within nanoliposomes with a considerable encapsulation efficiency for application in food products like yogurt to increase their nutritional value and public acceptance.

Insecticidal effects of the Olea europaea subsp. laperrinei extracts on the flour Pyralid Ephestia kuehniella

In the present study, the aerial parts of the Laperrine olive (Olea europaea subsp. Laperrinei) are subjected to acid extraction and the chemical composition of the extracts is determined by HPLC-DAD. The main compounds found in all of extracts are: hydroxytyrosol (30.45%), tyrosol (0.69%), oleuropein (32.76%), ferrulic acid (17.77%), quercetin (31.57%) and hesperetin (6.90%).The extracts obtained from the leafy stems of Laperrine olive tree are tested on the moth Ephestia kuehniella flour. Their administration by inhalation of newly exuviated chrysalises extends the duration of nymphalid development and disturbs the exuviated adults reproduction, by reducing the period in which the eggs are being laid. Thus, compared to the control insects, the number of eggs laid by treated females is significantly reduced after the treatment by extracts. Besides, the administration of different extracts of adult butterflies has a premature mortality effect.

Potential Herb-Drug Pharmacokinetic Interactions between African Wild Olive Leaf Extract and Selected Antihypertensive Drugs

The African wild olive (Olea europaea subsp. africana) is traditionally used as a hypotensive agent. Herb-drug interactions may result from the concurrent use of herbal medicines and conventional prescription drugs. This aspect was investigated by determining the effect of the extract on the in vitro intestinal epithelial permeation of selected hypotensive drugs using the Caco-2 cell culture model. The phytochemical profiles of leaf extracts of African wild olive from different localities in South Africa were compared, since efficacy is determined by the chemical composition. Extracts were analysed using ultra-performance liquid chromatography. The oleuropein concentration varied considerably from below the detection limit (4.94 µg/mL) to 59.4 mg/g dry weight. Chemometric models constructed from the aligned chromatographic data indicated only quantitative differences between the profiles. The leaf extract was found to increase the permeability of propranolol in the absorptive direction (P_app = 8.93 × 10^-6 cm/s) across Caco-2 cell monolayers, but considerably decreased transport in the secretory direction (P_app = 3.68 × 10^-6 cm/s). The permeation of diltiazem was enhanced by the extract in both the absorptive (P_app = 7.33 × 10^-6 cm/s) as well as in the secretory direction (P_app = 7.16 × 10^-6 cm/s), but a decrease in the efflux ratio was observed. The extract therefore caused a net increase in the transport of both drugs in the absorptive direction due to an inhibition effect on their efflux. This suggests a potential increase in the blood levels of these drugs when taken simultaneously with African wild olive leaf extract, indicating potential adverse effects that must be verified in vivo.

Oleuropein Curtails Pulmonary Inflammation and Tissue Destruction in Models of Experimental Asthma and Emphysema

Airway inflammation has been implicated in evoking progressive pulmonary disorders including chronic obstructive pulmonary disease (COPD) and asthma as a result of exposure to inhaled irritants, characterized by airway fibrosis, mucus hypersecretion, and loss of alveolar integrity. The current study examined whether oleuropein, a phenylethanoid found in olive leaves, inhibited pulmonary inflammation in experimental models of interleukin (IL)-4-exposed bronchial BEAS-2B epithelial cells and ovalbumin (OVA)- or cigarette smoke (CS)-exposed BALB/c mice. Nontoxic oleuropein at 1-20 μM diminished eotaxin-1-mediated induction of α-smooth muscle actin and mucin 5AC in epithelial cells stimulated by IL-4 at the transcriptional levels. Oral supplementation of 10-20 mg/kg oleuropein reduced the airway influx of eosinophils and lymphocytes as well as IL-4 secretion in lung promoted by OVA inhalation or CS. In addition, oleuropein suppressed infiltration of macrophages and neutrophils through blocking OVA inhalation- and CS-promoted induction of ICAM-1, F4/80, CD68, and CD11b in airways. OVA-exposed pulmonary fibrosis was detected, while alveolar emphysema was evident in CS-exposed mouse lungs. In alveolar epithelial A549 cells exposed to CS extracts, oleuropein attenuated apoptotic cell loss. Collectively, oleuropein inhibited pulmonary inflammation leading to asthmatic fibrosis and alveolar emphysema driven by influx of inflammatory cells in airways exposed OVA or CS. Therefore, oleuropein may be a promising anti-inflammatory agent for treating asthma and COPD.

Olive Oil Nutraceuticals in the Prevention and Management of Diabetes: From Molecules to Lifestyle

Lifestyle is the primary prevention of diabetes, especially type-2 diabetes (T2D). Nutritional intake of olive oil (OO), the key Mediterranean diet component has been associated with the prevention and management of many chronic diseases including T2D. Several OO bioactive compounds such as monounsaturated fatty acids, and key biophenols including hydroxytyrosol and oleuropein, have been associated with preventing inflammation and cytokine-induced oxidative damage, glucose lowering, reducing carbohydrate absorption, and increasing insulin sensitivity and related gene expression. However, research into the interaction of OO nutraceuticals with lifestyle components, especially physical activity, is lacking. Promising postprandial effects have been reported when OO or other similar monounsaturated fatty acids were the main dietary fat compared with other diets. Animal studies have shown a potential anabolic effect of oleuropein. Such effects could be further potentiated via exercise, especially strength training, which is an essential exercise prescription for individuals with T2D. There is also an evidence from in vitro, animal, and limited human studies for a dual preventative role of OO biophenols in diabetes and cancer, especially that they share similar risk factors. Putative antioxidative and anti-inflammatory mechanisms and associated gene expressions resulting from OO biophenols have produced paradoxical results, making suggested inferences from dual prevention T2D and cancer outcomes difficult. Well-designed human interventions and clinical trials are needed to decipher such a potential dual anticancer and antidiabetic effects of OO nutraceuticals. Exercise combined with OO consumption, individually or as part of a healthy diet is likely to induce reciprocal action for T2D prevention outcomes.

The Olive Biophenols Oleuropein and Hydroxytyrosol Selectively Reduce Proliferation, Influence the Cell Cycle, and Induce Apoptosis in Pancreatic Cancer Cells

Current chemotherapy drugs for pancreatic cancer only offer an increase in survival of up to six months. Additionally, they are highly toxic to normal tissues, drastically affecting the quality of life of patients. Therefore, the search for novel agents, which induce apoptosis in cancer cells while displaying limited toxicity towards normal cells, is paramount. The olive biophenols, oleuropein, hydroxytyrosol and tyrosol, have displayed cytotoxicity towards cancer cells without affecting non-tumorigenic cells in cancers of the breast and prostate. However, their activity in pancreatic cancer has not been investigated. Therefore, the aim of this study was to determine the anti-pancreatic cancer potential of oleuropein, hydroxytyrosol and tyrosol. Pancreatic cancer cells (MIA PaCa-2, BxPC-3, and CFPAC-1) and non-tumorigenic pancreas cells (HPDE) were treated with oleuropein, hydroxytyrosol and tyrosol to determine their effect on cell viability. Oleuropein displayed selective toxicity towards MIA PaCa-2 cells and hydroxytyrosol towards MIA PaCa-2 and HPDE cells. Subsequent analysis of Bcl-2 family proteins and caspase 3/7 activation determined that oleuropein and hydroxytyrosol induced apoptosis in MIA PaCa-2 cells, while oleuropein displayed a protective effect on HPDE cells. Gene expression analysis revealed putative mechanisms of action, which suggested that c-Jun and c-Fos are involved in oleuropein and hydroxytyrosol induced apoptosis of MIA PaCa-2 cells.

Expression of hydroxytyrosol and oleuropein biosynthetic genes are correlated with metabolite accumulation during fruit development in olive, Olea europaea, cv. Koroneiki

Olive tree is one of the most valuable crops cultivated for its oil that is rich in antioxidants. The beneficial effects of oleuropein and hydroxytyrosol (HT), the most abundant and the most powerful antioxidant respectively, as well as tyrosol, HT's precursor molecule, are well studied however their biosynthetic pathways are not yet clarified. The transcriptome analysis of the young olive fruit, cultivar "Koroneiki", revealed transcripts of all the enzymes used to reconstitute the biosynthetic pathway of tyrosol and HT in other organisms. We also identified transcripts of the genes that encode for enzymes involved in the secologanin biosynthesis, oleuropein's precursor molecule. Following the transcriptome analysis, the relative expression of the transcripts was monitored during fruit development and compared to the concentration of the 3 metabolites they synthesize at the same developmental stages. The highest expression levels, accompanied by the maximum concentration of the three metabolites, was found in the young olive fruit. The correlation between the expression profile and the metabolites' concentration indicates that the transcripts were correctly identified and the synthesis of the compounds is regulated at a transcriptional level. Interestingly, HT showed a sudden increment in the final developmental stage of the black mature fruit that is attributed to oleuropein catabolism.

The paradox of oleuropein increase in harvested olives (Olea europea L.)

Olives are non-climacteric fruit. In a previous article, oleuropein (OE) increased substantially in fresh green olives exposed to 20 °C for 7 d, but the increases were lower in preharvest treated fruit with an ethylene synthesis inhibitor. The present aim was to investigate whether phenolic compounds, including OE, were affected by ethylene treatment in green harvested olives. Postharvest treatments with the ethylene perception inhibitor, 1 -methylcyclopropene (1-MCP) at 1.5 μL L^-1 for 12 h, and/or ethylene at 1000 μL L^-1 at 20 °C for up to 10 d were applied to fruits of 'Konservolia' cultivar. The results showed that ethylene and/or 1-MCP had similar effects on total phenolics (TP), total antioxidant capacity (TAC) and OE and these results are revealed for the first time in olives. Ethylene had no effect on green loss, but 1-MCP prevented it slightly. In all treated fruit, but not in controls, TP and TAC were increased soon after harvest and remained almost stable throughout exposure, whereas OE increased in controls and all treated at later stages (as confirmed by HPLC-DAD-ESI-MS) independently of degreening. The present experiments could be applied to studies of ethylene perception and transcription related responses in these non- climacteric fruit. In practice, harvested olives do not lose their antioxidant capacity, but the OE elevation in short-stored olives at ambient temperature might have an impact on olive products quality.

Improving in vivo conversion of oleuropein into hydroxytyrosol by oral granules containing probiotic Lactobacillus plantarum 299v and an Olea europaea standardized extract

This study reports novel food-grade granules for co-delivery of L. plantarum 299v and a standardized extract of Olea europaea leaves (Phenolea®) as oral carrier of probiotics and hydroxytyrosol. Different granule formulations containing either L. plantarum 299v (Lac), or the olive leave extract (Phe) or their combination (Lac-Phe) have been successfully produced through wet granulation employing excipients generally regarded as safe as granulating/binding agents. L. plantarum cells withstood the manufacturing process and were stable upon storage at 4 °C for more than 6 months. In vitro dissolution studies in simulated gastro-intestinal fluids showed the capability of the granules to rapidly dissolve and deliver both olive leave phenols and living L. plantarum cells. In simulated digestion conditions, Lac and Lac-Phe granules protected L. plantarum against the harsh environment of the gastro-intestinal tract. Co-administration of Lac and Phe oral granules to healthy mice provided for higher amounts of hydroxytyrosol in urines as compared to Phe granules alone, suggesting that L. plantarum 299v boosted in vivo conversion of oleuropein to hydroxytyrosol. On the other hand, PCR-assisted profiling of the Lactobacillus population in faeces obtained from mice treated with Lac or Lac plus Phe confirmed that the probiotic arrived alive to colon and was there able to exert a sort of perturbing effect on the climax colonic microflora. Overall, these results pave the way towards the development of a nutraceutical useful for combined delivery of bioactive hydroxytyrosol and probiotics to colon site.

Quantitation of Oleuropein and Related Phenolics in Cured Spanish-Style Green, California-Style Black Ripe, and Greek-Style Natural Fermentation Olives

Oleuropein, ligstroside, and related hydrolysis products are key contributors to olive bitterness, and several of these phenolics are implicated in the prevention of lifestyle age-related diseases. While table olive processing methods are designed to reduce oleuropein, the impact of processing on ligstroside and related hydrolysis products (e.g., oleacein, oleocanthal, hydroxytyrosol glucoside, ligstroside aglycone, and oleuropein aglycone) is relatively unknown. Herein, levels of these compounds were measured in Spanish-style green (SP), Californian-style black ripe (CA), and Greek-style natural fermentation (GK) olives using rapid ultrahigh-performance liquid chromatography (UHPLC) tandem mass spectrometry (MS/MS). GK olives had the highest concentration of all compounds measured, with the exception of oleocanthal, which was highest in SP olives (0.081 mg kg^-1 wet weight (w.wt)). CA olives had the lowest levels of most compounds measured, including ligstroside (0.115 mg kg^-1 w.wt) and oleuropein (0.974 mg kg^-1 w.wt). Hydroxytyrosol was the predominate compound in all three styles of commercial olives, with similar concentrations observed for GK and SP olives (134.329 and 133.685 mg kg^-1 w.wt, respectively) and significantly lower concentrations observed for CA olives (19.981 mg kg^-1 w.wt).

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.

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.

Oleuropein shows copper complexing properties and noxious effect on cultured SH-SY5Y neuroblastoma cells depending on cell copper content

The secoiridoid oleuropein is a non-flavonoid polyphenol, found in the fruit, leaves and food derivatives from Olea europea. Like other polyphenols it shows a very low toxicity towards healthy tissues and a protective action against cancer or neurodegeneration, but its mechanism of action is not yet understood. In the present report we have used optical and ESR spectroscopy as well as molecular modelling to demonstrate that oleuropein forms a complex with the transition metal copper; the dysmetabolism of this metal is suspected to be involved in both cancer and neurodegeneration. Experiments carried out with the aglycon derivative of oleuropein, produced by β-glycosidase treatment of oleuropein glycoside, showed that also the aglycon forms copper-complexes, but with different spectroscopic features than the glycosidic form. Molecular modelling analysis confirmed that two oleuropein molecules (glycosidic or aglycon forms) can easily coordinate one copper ion. The relationship between oleuropein and copper was investigated in SH-SY5Y human neuroblastoma cells. When cells were depleted of copper by treatment with the copper chelator triethylenetetramine (Trien), that binds copper with higher affinity than oleuropein, oleuropein was less toxic than to copper-adequate cells. Conversely, incubation of SH-SY5Y cells with exogenous copper sulphate increased cell susceptibility to oleuropein. Furthermore SH-SY5Y cells differentiated by retinoic acid pre-treatment showed a lower level of copper, and were more resistant to oleuropein treatment. The oleuropein aglycon was not toxic towards SH-SY5Y cells. In conclusion, the copper-oleuropein complex may be involved in the toxicity of oleuropein towards tumour cells, depending on their copper level.

Impact of high-dose oleuropein on cisplatin-induced oxidative stress, genotoxicity and pathological changes in rat stomach and lung

The current systemic treatments of the various solid tumors involve Cisplatin (CIS)-based chemotherapy. Due to its cytotoxicity, this approach is limited. Moreover, the safety of CIS is only discussed especially in breast and stomach cancers. Therefore, we, for the first time, explored the restorative efficacy of oleuropein (OLE), in stomach and lung injuries induced by CIS. Sprague-Dawley rats were divided into eight groups: control CIS, OLE and CIS + OLE. Single dose of (7 mg/kg) CIS was administered intraperitoneally to CIS and CIS + OLE groups. After 24 h, 50, 100 and 200 mg/kg OLE was given for three consecutive days to OLE and CIS + OLE groups. The 8-OH-dG, total oxidative/antioxidant status (TOS/TAS) and malondialdehyde (MDA) levels were evaluated and histopathological analyses were performed on the studied tissues. The results indicated that CIS significantly increased 8-OH-dG, MDA and TOS levels and caused severe tissue damages. However, high dose of OLE induced a significant decrease in the 8-OH-dG, MDA levels, an increase in TAS levels and it restores CIS-induced tissue damages. We hope that the results of this study will provide an impetus for future studies on novel therapeutic strategies including the protective use of oleuropein in gastric and lung cancers due to chemotherapy.

Oleuropein improves glucose tolerance and lipid profile in rats with simultaneous renovascular hypertension and type 2 diabetes

Oleuropein mediates most of the beneficial effects of olive products. This study examined the role of oxidative stress in the effects of oleuropein on lipid profile and blood glucose in rats with simultaneous renovascular hypertension and type 2 diabetes. Eight groups (n = 7-9 each) of male Sprague-Dawley rats including a control, a type 2 diabetic, a renovascular hypertensive, a sham, a simultaneously hypertensive diabetic receiving vehicle, and 3 simultaneously hypertensive-diabetic receiving 20, 40, or 60 mg/kg/day oleuropein were used. Four weeks after treatment, blood glucose, lipid profile, and biomarkers of oxidative stress were measured, and glucose tolerance test (GTT) was performed. Simultaneously hypertensive diabetic rats had significantly higher blood pressure, blood glucose, and serum total cholesterol, low-density lipoprotein cholesterol (LDL-C), triglyceride and malondialdehyde. They also had lower serum high-density lipoprotein cholesterol, erythrocyte superoxide dismutase, and impaired glucose tolerance. Oleuropein significantly reduced blood pressure, blood glucose, and serum total cholesterol, LDL-C, triglyceride and malondoaldehyde. It also increased serum high-density lipoprotein cholesterol, erythrocyte superoxide dismutase, and improved glucose tolerance. The findings show that the model is associated with impaired glucose tolerance, and adverse lipid profile. They also show that oleuropein, partly by an antioxidant mechanism, improves glucose tolerance and changed lipid profile favorably.

Anticancer effects of oleuropein

Cancer cells exhibit enhanced proliferation rate and a resistance to apoptosis. Epidemiological studies suggest that olive oil intake is associated with a reduced risk of cancer. Olive oil, olives, and olive leaves contain many polyphenols, including oleuropein. Recently, several studies have demonstrated that oleuropein inhibits proliferation and induces apoptosis in different cancer cell lines. In addition, anticancer effects of oleuropein have been seen in animal studies. These effects are associated with oleuropein's ability to modulate gene expression and activity of a variety of different signaling proteins that play a role in proliferation and apoptosis. This article summarizes the existing in vitro and in vivo studies focusing on the anticancer effects of oleuropein and its effects on key signaling molecules. © 2017 BioFactors, 43(4):517-528, 2017.

The C-Domain of Oleuropein β-Glucosidase Assists in Protein Folding and Sequesters the Enzyme in Nucleus

Oleuropein, a terpene-derived glycosylated secoiridoid biosynthesized exclusively by members of the Oleaceae family, is involved in a two-component defense system comprising a β-glucosidase that activates oleuropein into a toxic glutaraldehyde-like structure. Oleuropein and its deglycosylated derivatives have high pharmaceutical interest. In this study we determined that the in planta heterologous expressed OeGLU, an oleuropein-specific β-glucosidase from olive (Olea europaea), had enzymatic kinetics similar to the olive native enzyme. The C terminus encompassing the nuclear localization signal sequesters the enzyme in the nucleus, and predetermines the protein-protein recognition and homodimerization. Biochemical analysis revealed that OeGLU is a homomultimer with high M_r In silico prediction modeling of the complex structure and bimolecular fluorescence complementation analyses revealed that the C terminus of OeGLU is essential for the proper assembly of an octameric form, a key conformational feature that determines the activity of the enzyme. Our results demonstrate that intrinsic characteristics of the OeGLU ensure separation from oleuropein and keep the dual-partner defensive system conditionally inactive. Upon cell destruction, the dual-partner defense system is activated and olive massively releases the arsenal of defense.

Bioactivity Improvement of Olea europaea Leaf Extract Biotransformed by Wickerhamomyces anomalus Enzymes

Olive leaves represent a quantitatively significant by-product of agroindustry. They are rich in phenols, mainly oleuropein, which can be hydrolyzed into several bioactive compounds, including hydroxytyrosol. In this study, water extract from olive leaves 'Biancolilla' was analyzed for polyphenol profile, DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity and protective effect on differentiated Caco-2 cells. The efficacy of two enzymatic treatments in promoting the release of bioactive phenols was investigated: a) enzymatic extract from Wickerhamomyces anomalus, characterized by β-glucosidase and esterase activities; b) commercial β-glucosidase. Composition and bioactivity of the resulting extracts were compared. The results showed that the yeast-treated extract presented hydroxytyrosol content and DPPH radical scavenging activity comparable to those obtained using commercial β-glucosidase; however, it was showed the additional presence of hydroxycinnamic acids. In experiments on Caco-2 cells, the leaf extracts promoted the recovery of cell membrane barrier at different minimum effective concentrations. The high specificity of W. anomalus enzymatic extract may represent an effective tool for the release of bioactive phenols from olive by-products.

Impact of phenolic-rich olive leaf extract on blood pressure, plasma lipids and inflammatory markers: a randomised controlled trial

PURPOSE

Dietary polyphenols have been demonstrated to favourably modify a number of cardiovascular risk markers such as blood pressure (BP), endothelial function and plasma lipids. We conducted a randomised, double-blind, controlled, crossover trial to investigate the effects of a phenolic-rich olive leaf extract (OLE) on BP and a number of associated vascular and metabolic measures.

METHODS

A total of 60 pre-hypertensive [systolic blood pressure (SBP): 121-140 mmHg; diastolic blood pressure (DBP): 81-90 mmHg] males [mean age 45 (±SD 12.7 years, BMI 26.7 (±3.21) kg/m2] consumed either OLE (136 mg oleuropein; 6 mg hydroxytyrosol) or a polyphenol-free control daily for 6 weeks before switching to the alternate arm after a 4-week washout.

RESULTS

Daytime [-3.95 (±SD 11.48) mmHg, p = 0.027] and 24-h SBP [-3.33 (±SD 10.81) mmHg, p = 0.045] and daytime and 24-h DBP [-3.00 (±SD 8.54) mmHg, p = 0.025; -2.42 (±SD 7.61) mmHg, p = 0.039] were all significantly lower following OLE intake, relative to the control. Reductions in plasma total cholesterol [-0.32 (±SD 0.70) mmol/L, p = 0.002], LDL cholesterol [-0.19 (±SD 0.56) mmol/L, p = 0.017] and triglycerides [-0.18 (±SD 0.48), p = 0.008] were also induced by OLE compared to control, whilst a reduction in interleukin-8 [-0.63 (±SD 1.13) pg/ml; p = 0.026] was also detected. Other markers of inflammation, vascular function and glucose metabolism were not affected.

CONCLUSION

Our data support previous research, suggesting that OLE intake engenders hypotensive and lipid-lowering effects in vivo.

Effect of light irradiation on the antioxidant stability of oleuropein

The stability of oleuropein, a natural antioxidant from Olea europaea, has been often studied in connection with thermal or enzymatic treatments, but very little is known about the effects of UV light. This work aimed at studying the UV-C effects on oleuropein standard solutions once dissolved in ethanol or water. During irradiation, aliquots were taken and analyzed by a flow injection system equipped with a multi-channel coulometric detector and a high-resolution mass spectrometer. The effects of irradiation were also studied by UV spectroscopy. The results show that oleuropein is relatively stable in water or ethanol, but that under UV-C light undergoes a series of fast decomposition reactions leading to hydroxytyrosol and elenolic acid. Overall, this study provides evidences that the degradation of oleuropein by UV-C light follows a mechanism dependent on the solvent used. Moreover, the solvent affects the resulting redox properties of the solution.