The olive constituent oleuropein exhibits anti-ischemic, antioxidative, and hypolipidemic effects in anesthetized rabbits

Cardioprotective and neuroprotective roles of oleuropein in olive

Traditional diets of people living in the Mediterranean basin are, among other components, very rich in extra-virgin olive oil, the most typical source of visible fat. Olive is a priceless source of monounsaturated and di-unsaturated fatty acids, polyphenolic antioxidants and vitamins. Oleuropein is the main glycoside in olives and is responsible for the bitter taste of immature and unprocessed olives. Chemically, oleuropein is the ester of elenolic acid and 3,4-dihydroxyphenyl ethanol, which possesses beneficial effects on human health, such as antioxidant, antiatherogenic, anti-cancer, anti-inflammatory and antimicrobial properties. The phenolic fraction extracted from the leaves of the olive tree, which contains significant amounts of oleuropein, prevents lipoprotein oxidation. In addition, oleuropein has shown cardioprotective effect against acute adriamycin cardiotoxicity and an anti-ischemic and hypolipidemic activities. Recently, oleuropein has shown neuroprotection by forming a non-covalent complex with the Aβ peptide, which is a key hallmark of several degenerative diseases like Alzheimer and Parkinson. Thus, a large mass of research has been accumulating in the area of olive oil, in the attempt to provide evidence for the health benefits of olive oil consumption and to scientifically support the widespread adoption of traditional Mediterranean diet as a model of healthy eating. These results provide a molecular basis for some of the benefits potentially coming from oleuropein consumption and pave the way to further studies on the possible pharmacological use of oleuropein to prevent or to slow down the cardiovascular and neurodegenerative diseases.

Olive leaf extract attenuates cardiac, hepatic, and metabolic changes in high carbohydrate-, high fat-fed rats

Olive oil, an important component of the Mediterranean diet, produces cardioprotective effects, probably due to both oleic acid and the polyphenols such as oleuropein and hydroxytyrosol. Our aim in this study was to assess whether a polyphenol-enriched extract from the leaves of Olea europaea L. with oleuropein as the major component attenuated the cardiovascular, hepatic, and metabolic signs of a high-carbohydrate, high-fat (HCHF) diet (carbohydrate, 52%; fat, 24%, 25% fructose in drinking water) in rats. Male Wistar rats were fed either a cornstarch diet (CS) or a HCHF diet for a total of 16 wk. Diets of the treatment groups [CS+olive leaf extract (OLE) and HCHF+OLE] were supplemented with 3% OLE after 8 wk of being fed their respective CS or HCHF diets for a further 8 wk. After 16 wk, HCHF rats developed signs of metabolic syndrome, including elevated abdominal and hepatic fat deposition, collagen deposition in heart and liver, cardiac stiffness, and oxidative stress markers (plasma malondialdehyde and uric acid concentrations), with diminished aortic ring reactivity, abnormal plasma lipid profile, impaired glucose tolerance, and hypertension. Compared with HCHF rats, those in the HCHF+OLE group had improved or normalized cardiovascular, hepatic, and metabolic signs with the exception of elevated blood pressure. These results strongly suggest that an OLE containing polyphenols such as oleuropein and hydroxytyrosol reverses the chronic inflammation and oxidative stress that induces the cardiovascular, hepatic, and metabolic symptoms in this rat model of diet-induced obesity and diabetes without changing blood pressure.

Oleuropein in olive and its pharmacological effects

Olive from Olea europaea is native to the Mediterranean region and, both the oil and the fruit are some of the main components of the Mediterranean diet. The main active constituents of olive oil include oleic acid, phenolic constituents, and squalene. The main phenolic compounds, hydroxytyrosol and oleuropein, give extra-virgin olive oil its bitter, pungent taste. The present review focuses on recent works that have analyzed the relationship between the major phenolic compound oleuropein and its pharmacological activities including antioxidant, anti-inflammatory, anti-atherogenic, anti-cancer activities, antimicrobial activity, antiviral activity, hypolipidemic and hypoglycemic effect.

Olive leaf extract prevents spontaneous occurrence of non-alcoholic steatohepatitis in SHR/NDmcr-cp rats

AIMS

Oxidative stress may play an important role in the pathogenesis of non-alcoholic steatohepatitis (NASH). Oleuropein, the active constituent of olive leaf, possesses anti-oxidant, hypoglycaemic, and hypolipidaemic activities. We aimed to investigate the preventive effects of olive leaf extract on hepatic fat accumulation in a rat model of NASH.

METHODS

Spontaneously hypertensive/NIH-corpulent rats were fed a diet of AIN-93G with or without olive leaf extract (500, 1000, 2000 mg/kg diet, and control; 5 rats each) for 23 weeks. Serological and histopathological findings, anti-oxidative activity, and the alteration of fatty acid synthesis in the liver were evaluated.

RESULTS

Histopathologically, a diet of AIN-93G containing more than 1000 mg/kg olive leaf extract had a preventive effect for the occurrence of NASH. Thioredoxin-1 expression in the liver was more evident in rats fed this diet, and 4-hydroxynonenal expression in the liver was less evident in these rats. There were no significant differences in the activities of hepatic carnitine palmitoyltransferase, fatty acid synthase, malic enzyme, and phosphatidic acid phosphohydrolase among the groups.

CONCLUSIONS

Our data suggest that olive leaf extract may help prevent NASH, presumably through its anti-oxidative activity.

Identification of Throuba Thassos, a traditional Greek table olive variety, as a nutritional rich source of oleuropein

The content of polyphenols in table olives is highly influenced by the olive variety and the debittering process applied on the fruits. Nine commercial types of Greek table olives were examined for their content in oleuropein and hydroxytyrosol. A very simple extraction procedure and a chromatographic methodology were applied for the simultaneous quantitation of oleuropein (OE) and hydroxytyrosol (HT) in drupes, using boiling water extraction followed by direct HPLC analysis. Hydroxytyrosol was found in all the types of olives that were studied. Kalamata olives and Green "tsakistes" of the variety Megaritiki contained the highest quantity of hydroxytyrosol (1.8-2.0 mg/fruit) followed by Greek-style "chondrolies" with quantity 1.0 mg/fruit. Oleuropein was found in small quantities in two cases, but in the case of Throuba Thassos which is processed by dry salt in a traditional Greek way, oleuropein was found in important quantities (1.2 mg/fruit) recorded over a 4-year period. This is the most important finding of this study showing that this particular table olive type is a nutritional rich source of oleuropein. Additionally, assuming a usual consumption of 20 olive fruits per day, an approximate quantity of 25 mg of oleuropein per day can be considered as safe for human use, since it can be found in the usual diet.

Stability of oleuropein in the human proximal gut

Objectives

We aimed to assess the intralumenal stability of oleuropein in human gastric and small intestinal contents. We additionally aimed to assess the stability characteristics of oleuropein in media simulating the intralumenal conditions.

Methods

The intralumenal stability of oleuropein was assessed in aspirates from the stomach and the upper small intestine of healthy volunteers collected under both fasted and fed state conditions and in media simulating the intralumenal environment.

Key findings

Oleuropein degraded in aspirates collected in the fasted state. When the initial concentration was about 50 μg/ml (close to expected intragastric concentration after single dose of commercially available products of oleuropein) the mean zero-order half-life of oleuropein in aspirates collected from the fasted small intestine was estimated to be 3.14 ± 0.08 h at 37°C (i.e. after oral administration in the fasted state, a substantial fraction of oleuropein degrades before reaching the intestinal mucosa). In contrast, oleuropein was stable in aspirates collected from the fed stomach; in small intestinal contents aspirated in the fed state the estimated zero-order degradation half-life was at least 12 h.

Conclusions

These data suggest that oleuropein should not have substantial intralumenal stability problems when administered in the fed state. Data collected in media simulating the intragastric and intraintestinal environment suggest that pH affects the stability of oleuropein only at low pH values (of about 2). At higher pHs degradation characteristics are at least partly affected by the presence of other scavengers of reactive oxygen species in the medium.

Olive leaf extract and its main component oleuropein prevent chronic ultraviolet B radiation-induced skin damage and carcinogenesis in hairless mice

Chronic exposure to solar UV radiation damages skin, increasing its thickness and reducing its elasticity, and causes skin cancer. Our aim in this study was to examine the effects of an olive leaf extract and its component oleuropein on skin damage and the incidence of skin tumors caused by long-term UVB irradiation in hairless mice. Male hairless mice (5 wk old) were divided into 6 groups, including a non-UVB group, a vehicle-treated UVB group (control), 2 olive leaf extract-treated UVB groups, and 2 oleuropein-treated UVB groups. Five groups were UVB irradiated (36-180 mJ/cm(2)) 3 times each week for 30 wk and skin thickness and elasticity after UVB irradiation were measured every week. Olive leaf extract (300 and 1000 mg/kg) and oleuropein (10 and 25 mg/kg) were administered orally twice daily every day for 30 wk. The extract and oleuropein significantly inhibited increases in skin thickness and reductions in skin elasticity, and skin carcinogenesis and tumor growth. Furthermore, they prevented increases in the expression of matrix metalloproteinase (MMP)-2, MMP-9, and MMP-13 as well as in levels of vascular endothelial growth factor (VEGF) and cyclooxygenase-2 (COX-2) in the skin. Based on histological evaluation, they prevented increases in the expression of Ki-67 and CD31-positive cells induced by the irradiation. These results suggest that the preventative effects of the olive leaf extract and oleuropein on chronic UVB-induced skin damage and carcinogenesis and tumor growth may be due to inhibition of the expression of VEGF, MMP-2, MMP-9, and MMP-13 through a reduction in COX-2 levels.

Metabonomic identification of novel biomarkers in doxorubicin cardiotoxicity and protective effect of the natural antioxidant oleuropein

Doxorubicin (DXR) is a commonly used antineoplastic agent; however, its use is limited due to cardiotoxicity. Oxidative stress and consequent alterations of cardiac energetics are involved in the development of DXR toxicity. Oleuropein (Oleu) is a phenolic antioxidant, present in olive tree, reported to confer protection against DXR cardiotoxicity. In this study, NMR based-metabonomics was applied to characterize the metabolic profile of the acute DXR cardiotoxicity in rats and to evaluate the metabolic alterations conferred by co-treatment with Oleu. Wistar rats were divided into six groups and treated as follows: control group with a single injection of 2 mL normal saline intraperitoneally (i.p.), DXR group with a single dose of 20 mg/kg, i.p and DXR plus Oleu groups with 20mg/kg DXR i.p., and 100 or 200 mg/kg/BW of Oleu i.p. for 5 or 3 consecutive days starting either 2 days before or on the day of DXR administration. Hearts were excised 72 h after DXR treatment and (1)H-NMR spectra of aqueous myocardium extracts were recorded. Principal Component Analysis (PCA) and Partial Least Square Discriminant Analysis (PLS-DA) revealed differences in the metabolic profile between control and DXR attributed to several metabolites. A number of them were quantified by integration of the NMR spectra. Myocardial levels of acetate and succinate were increased in DXR compared to controls, while branched amino acids were decreased. These results correlate with nonenzymatic conversion of pyruvate to acetate and of alpha-ketoglutarate to succinate by DXR free radicals. Oleu completely restored the changes of metabolites to the normal levels. Acetate and succinate constitute novel biomarkers related to DXR, and Oleu treatment aids the compensation of distressed energy metabolic pathways.

Antihyperglycemic effects of fruits of privet (Ligustrum obtusifolium) in streptozotocin-induced diabetic rats fed a high fat diet

The protective effects of freeze-dried privet (Ligustrum obtusifolium) fruits (PFs) were observed in streptozotocin (STZ)-induced diabetic rats on a high fat diet by measuring levels of blood glucose, serum insulin, fructosamine, and hepatic reactive oxygen species generating and scavenging enzyme activities. A PF-supplemented diet was prepared by mixing an AIN-76 diet with powdered PF (final concentration, 1% or 2%). It was fed to STZ-induced diabetic rats on a high fat diet for 6 weeks. Diabetic animals receiving the PF-supplemented diet showed a significant increase in body weight, feed efficiency ratio, liver, kidney, and heart weight, and serum glucose, insulin, and fructosamine levels compared with high fat diet-fed diabetic animals. The treatment with PF showed improved hepatic glutathione S-transferase, superoxide dismutase, and xanthine oxidase activities as well as glutathione and lipid peroxide levels in the diabetic animals. Intracellular swelling and vacuole formation in diabetic pancreatic beta- and delta-cells were ameliorated by the PF-supplemented diet. Furthermore, necrosis of tubular epithelial cells and dilatation of luminal space in diabetic kidneys exhibited near-noninjured condition. This is the first time an antihyperglycemic effect of L. obtusifolium fruit in STZ-induced diabetic rats has been identified.

An extra-virgin olive oil rich in polyphenolic compounds has antioxidant effects in OF1 mice

Extra-virgin olive oil (OO) is becoming more important in daily diets due to its beneficial effects on health, most of which are because of its antioxidant content. We studied the antioxidant activity and mechanisms of an extra-virgin OO that is rich in phenolics on pancreatic islets and liver in control mice (CTL) fed a nonpurified diet and in mice supplemented with 50 microL/d sunflower oil (SO) or 50 microL/d extra-virgin OO for 4 d. Plasma hydroxytyrosol concentration was determined by HPLC-diode array detector. Plasma antioxidant capacity, enzymatic activities, and lipid peroxidation were measured by spectrophotometry. Islet function was studied by measuring insulin release. Islet cell gene expression was examined using quantitative RT-PCR. The plasma hydroxytyrosol concentration was greater in OO mice than in CTL or SO mice (P < 0.05) and was greater in SO mice than in CTL mice. The ratio of reduced:oxidized glutathione and the antioxidant capacity in plasma was greater in OO mice than in CTL or SO mice (P < 0.05) and higher in SO mice than in CTL mice. Glucose-stimulated insulin secretion was greater in OO mice than in CTL or SO mice (P < 0.05) and was also higher in SO mice than in CTL mice. Protection against liver cell and beta cell membrane lipid peroxidation was greater in OO mice than in CTL or SO mice (P < 0.05) and was greater in SO mice than in CTL mice. Catalase (CAT) expression in the islet of Langerhans was higher in OO mice than in CTL mice and SO mice (P < 0.05). The CAT and glutathione peroxidase 1 activities in the islet of Langerhans were 25% greater in OO mice than in CTL mice and higher than in SO mice (P < 0.05) and they were greater in SO mice than in CTL mice. These results indicate that, in metabolic tissues, protection by extra-virgin OO against oxidative stress occurs primarily through a direct antioxidant effect as well as through an indirect mechanism that involves greater expression and activity of certain enzymes with antioxidant activities.

Retention and distribution of polyphenols after pan-frying of French fries in oils enriched with olive leaf extract

Palm oil, olive oil, and sunflower oil were supplemented with an extract rich in polyphenols obtained from olive tree (Olea europaea) leaves at levels of 120 and 240 mg total polyphenols per kilogram of oil. Pan-frying of potatoes was performed in both the enriched and the nonsupplemented oils under domestic frying conditions. Total polyphenol content was estimated by the Folin-Ciocalteau assay, oleuropein was determined by HPLC analysis, while other individual polyphenols by GC/MS analysis. Fourteen polyphenol species were identified in the olive leaf extract, among which oleuropein predominated (1.25 g/kg olive leaves). All the enriched oils contained oleuropein before and after frying. Oleuropein as well as other polyphenol species were detected in all French fries cooked in enriched oils. Polyphenol intake by consuming French fries pan-fried in the enriched oils was calculated to be 6 to 31 times higher than that in the case of French fries fried in commercial oils, being dependent on the frying oil type.

Effects of Levosimendan on circulating markers of oxidative and nitrosative stress in patients with advanced heart failure

BACKGROUND

Oxidative stress is associated with maladaptive cardiac remodeling and vascular dysfunction and may be an important contributor to chronic heart failure (CHF) deterioration. We sought to investigate if the calcium sensitizer levosimendan beneficially modulates circulating markers of oxidative and nitrosative stress thus lessening their deleterious effects in patients with advanced CHF.

METHODS

Thirty-nine patients with advanced CHF (mean NYHA 3.5+/-0.4; ischemic/dilated: 23/16; mean left ventricular ejection fraction: 26+/-7%) who were hospitalized due to syndrome worsening, were randomized (2:1) to receive either a 24-h levosimendan infusion of 0.1 microg/(kg min) (n=26) or placebo (n=13). Plasma b-type natriuretic peptide (BNP), circulating markers of oxidative [protein carbonyls, malondialdehyde (MDA)] and nitrosative (nitrotyrosine) stress, and cyclic GMP (cGMP) were measured at baseline and 48 h after each treatment.

RESULTS

Baseline characteristics and medications were well balanced in the two treatment groups. A significant improvement in left ventricular ejection fraction (P<0.01), NYHA class (P<0.01), and plasma BNP (P<0.01) was observed post-treatment only in the levosimendan group. Markers such as MDA, protein carbonyls and nitrotyrosine remained stable in the levosimendan-treated group, but significantly increased (P<0.05) in the placebo-treated patients. Neither therapeutic intervention changed the levels of circulating cGMP.

CONCLUSION

Levosimendan does not increase markers of oxidative and nitrosative stress in contrast to the placebo treatment, thus, exerting cardioprotective effects in advanced CHF patients. Moreover, levosimendan may exert its biologic action through non-cGMP-dependent biochemical pathways.

Encapsulation of olive leaf extract in beta-cyclodextrin

Olive leaf extract, rich in oleuropein, formed an inclusion complex with beta-cyclodextrin (beta-CD) upon mixing of the components in aqueous media and subsequent freeze-drying. Inclusion complex formation was confirmed by differential scanning calorimetry (DSC). DSC thermograms indicated that the endothermic peaks of both the olive leaf extract and the physical mixture of olive leaf extract with beta-CD, attributed to the melting of crystals of the extract, were absent in DSC thermogram of inclusion complex. Moreover, DSC studies under oxidative conditions indicated that the complex of olive leaf extract with beta-CD was protected against oxidation, since it remained intact at temperatures where the free olive leaf extract was oxidized. Phase solubility studies afforded A L type diagrams, 1:1 complex stoichiometry, a moderate binding constant ( approximately 300 M (-1)), and an increase of the aqueous solubility by approximately 50%. The formation of the inclusion complex was also confirmed by nuclear magnetic resonance (NMR) studies of beta-CD solutions in the presence of both pure oleuropein and olive leaf extract. The NMR data have established the formation of a 1:1 complex with beta-CD that involves deep insertion of the dihydroxyphenethyl moiety inside the cavity from its secondary side.

The olive constituent oleuropein exhibits proteasome stimulatory properties in vitro and confers life span extension of human embryonic fibroblasts

Normal human fibroblasts undergo replicative senescence due to both genetic and environmental factors. Senescence and aging can be further accelerated by exposure of cells to a variety of oxidative agents that contribute among other effects to the accumulation of damaged proteins. The proteasome, a multicatalytic nonlysosomal protease, has impaired function during aging, while its increased expression delays senescence in human fibroblasts. The aim of this study was to identify natural compounds that enhance proteasome activity and exhibit antiaging properties. We demonstrate that oleuropein, the major constituent of Olea europea leaf extract, olive oil and olives, enhances the proteasome activities in vitro stronger than other known chemical activators, possibly through conformational changes of the proteasome. Moreover, continuous treatment of early passage human embryonic fibroblasts with oleuropein decreases the intracellular levels of reactive oxygen species (ROS), reduces the amount of oxidized proteins through increased proteasome-mediated degradation rates and retains proteasome function during replicative senescence. Importantly, oleuropein-treated cultures exhibit a delay in the appearance of senescence morphology and their life span is extended by approximately 15%. In summary, these data demonstrate the beneficial effect of oleuropein on human fibroblasts undergoing replicative senescence and provide new insights towards enhancement of cellular antioxidant mechanisms by natural compounds that can be easily up-taken through normal diet.

Application of NMR-based metabonomics in the investigation of myocardial ischemia-reperfusion, ischemic preconditioning and antioxidant intervention in rabbits

NMR based metabonomics was applied in rabbit plasma samples during myocardial ischemia-reperfusion injury, with the following interventions: (1) Control (no intervention); (2) ischemic preconditioning (IpC); (3) administration of melatonin; (4) IpC+administration of melatonin; (5) treatment of the indole derivative C6458. The (1)H NMR signal intensity ratio of lactate/glucose was found to increase in Control samples during reperfusion compared to baseline, while lactate+alanine/acetate was decreased suggesting impairment of aerobic glycolysis and concomitant lipid utilization. In contrast, after IpC or treatment with C6458, the lactate/glucose ratio was similar to baseline in accordance with the previously reported decrease in infarct size. Multivariate statistical methods such as Principal Component Analysis (PCA), and Discriminant Analysis (DA) were used for the discrimination of samples. The use of ANOVA variable preselection prior to PCA was advantageous in producing adequate models. PCA could classify the Control group in three clusters according to the condition of the heart (baseline-ischemia-reperfusion) while in the IpC groups no classification was evident. PCA discrimination upon treatment with melatonin and C6458 provided further evidence of their effect on the metabolic profile. The supervised DA resulted in fine discrimination between the different subgroups. Plasma NMR spectra in combination with pattern recognition techniques proved to be an efficient and simple method to depict the metabolic changes produced upon ischemia-reperfusion of the myocardium.

1H NMR Monitoring of the Canine Metabolic Profile after Oral Administration of Xenobiotics Using Multivariate Statistics

This study describes a chemometric analysis of 1H NMR spectra of canine plasma following oral single dose administrations of two food components (lycopene and oleuropein) and of two drug products, Fungoral (ketoconazole) and Adalat (nifedipine). Due to the high interday physiological variation, 1H NMR plasma data were first filtered (by applying orthogonal signal correction) and then subjected to principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA). A distinct discrimination was achieved between samples obtained with and without administration of xenobiotics using both techniques. According to distance to model criterion and as shown by the Cooman's plots there was no overlap between the four models which proved to be specific for each xenobiotic. Moreover, it was shown that this approach has the potential to recognize subtle variations in the metabolic profile even if the administered xenobiotic itself could not be detected in the canine plasma by conventional HPLC methods.