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PubMed2004

Olive oil consumption and reduced incidence of hypertension: the SUN study.

Olive oil, a major component of the Mediterranean diet, has been associated in some small clinical trials and cross-sectional studies with a reduction in blood pressure. The objective of this study was to assess the association of olive oil consumption with the incidence of hypertension in an epidemiologic cohort, the Seguimiento Universidad de Navarra (SUN) study. The SUN Project is a prospective cohort study whose members are all university graduates. The recruitment and follow-up of participants is made using mailed questionnaires. Diet was assessed using a semiquantitative food frequency questionnaire previously validated in Spain, with 136 items. Outcomes of interest were newly diagnosed cases of hypertension, as reported by participants in the follow-up questionnaires. Logistic regression models were fit to assess the risk of hypertension associated with olive oil consumption. For the present analysis, we have taken in consideration the first 6,863 participants, with at least 2 yr of follow-up. After a median follow-up time of 28.5 mon, the cumulative incidence of hypertension was 4.7% in men and 1.7% in women. A lower risk of hypertension was observed among participants with a higher olive oil consumption at baseline, but the results were not statistically significant (P = 0.13 for the linear trend test in the multivariate model). However, among men, the adjusted odds ratios (OR) (95% confidence intervals) of hypertension for the second to fifth quintiles of olive oil consumption, compared with the first quintile, were 0.55 (0.28-1.10), 0.75 (0.39-1.43), 0.32 (0.15-0.70), and 0.46 (0.23-0.94), respectively (P = 0.02 for linear trend). No association was found between olive oil consumption and the risk of hypertension among women. In conclusion, in a Mediterranean population, we found olive oil consumption to be associated with a reduced risk of hypertension only among men. The lack of association observed among women might be attributed to the overall lower incidence of hypertension found among females and the resulting lower statistical power.

Adult↗
PubMed2002

Stability of virgin olive oil. 1. Autoxidation studies.

Virgin olive oil samples with similar oxidative stabilities and fatty acid compositions were stored for 24 months. Changes in the lipid substrate were followed by peroxide value and K(232) measurements. HPLC was used to evaluate changes in the alpha-tocopherol, pigment, and squalene contents. Total polar phenol content was measured colorimetrically. The loss of alpha-tocopherol and carotenoids was comparable with that of polar phenol content, suggesting an active participation in autoxidation. The limited role of squalene in autoxidation was further confirmed using an olive oil model and in the presence of alpha-tocopherol. Pheophytin a degradation was high, although spectrometric estimation of chlorophyll content did not indicate so. Evaluation of pheophytin a activity at three different levels of addition on the oil model indicated a concentration-dependent antioxidant role more pronounced at elevated temperatures, which could be partially due to the activity of certain degradation products.

Carotenoids↗
PubMed1995

Inhibition of platelet aggregation and eicosanoid production by phenolic components of olive oil.

This study was designed to investigate the in vitro effects of phenolic compounds extracted from olive oil and from olive derived fractions. More specifically, we investigated the effects on platelets of 2-(3,4-di-hydroxyphenyl)-ethanol (DHPE), a phenol component of extra-virgin olive oil with potent antioxidant properties. The following variables were studied: aggregation of platelet rich plasma (PRP) induced by ADP or collagen, and thromboxane B2 production by collagen or thrombin-stimulated PRP. In addition, thromboxane B2 and 12-hydroxyeicosatetraenoic acid (12-HETE) produced during blood clotting were measured in serum. Preincubation of PRP with DHPE for at least 10 min resulted in maximal inhibition of the various measured variables. The IC50s (concentration resulting in 50% inhibition) of DHPE for ADP or collagen-induced PRP aggregations were 23 and 67 microM, respectively. At 400 microM DHPE, a concentration which completely inhibited collagen-induced PRP aggregation, TxB2 production by collagen- or thrombin-stimulated PRP was inhibited by over 80 percent. At the same DHPE concentration, the accumulation of TxB2 and 12-HETE in serum was reduced by over 90 and 50 percent, respectively. We also tested the effects of PRP aggregation of oleuropein, another typical olive oil phenol, and of selected flavnoids (luteolin, apigenin, quercetin) and found them to be much less active. On the other hand a partially characterized phenol-enriched extract obtained from aqueous waste from olive oil showed rather potent activities. Our results are the first evidence that components of the phenolic fraction of olive oil can inhibit platelet function and eicosanoid formation in vitro, and that other, partially characterized, olive derivatives share these biological activities.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed2001

Co-combustion of waste from olive oil production with coal in a fluidised bed.

Waste from olive oil production was co-fired with coal in a fluidised bed combustor to study the feasibility of using this waste as an energy source. The combustion efficiency and CO emission were investigated and compared to those of burning 100% of coal. Olive oil waste with up to 20% mass concentration can be co-fired with coal in a fluidised bed combustor designed for coal combustion with a maximum drop of efficiency of 5%. A 10% olive oil waste concentration gave a lower CO emission than 100% coal firing due to improved combustion in the freeboard region. A 20% olive oil waste mixture gave a higher CO emission than both 100% coal firing and 10% olive oil waste mixture, but the combustion efficiency was higher than the 10% olive oil waste mixture due to lower elutriation from the bed.

Carbon Monoxide↗
PubMed2000

Consumption of olive oil has opposite effects on plasma total cholesterol and sphingomyelin concentrations in rats.

The hypothesis that olive-oil consumption alters plasma sphingomyelin concentrations and hepatic sphingomyelin metabolism was tested. Rats were fed on purified, high-cholesterol diets with either coconut fat or olive-oil (180 g/kg). In accordance with previous work, olive-oil v. coconut-fat consumption significantly elevated hepatic and total plasma cholesterol concentrations. During the course of the experiment, the concentration of plasma sphingomyelin rose in the coconut-fat group and remained constant in the olive-oil group. When compared with the coconut-fat-fed group, the plasma sphingomyelin levels were significantly lower in the olive-oil-fed group after 14 and 21 d of treatment. Dietary olive oil raised the amounts of cholesterol and sphingomyelin in the VLDL density region, and this change was associated with a reduction in the cholesterol and sphingomyelin contents of the LDL and HDL density ranges. Olive-oil consumption reduced the activity of serine palmitoyltransferase, while the activities of phosphatidylcholine:ceramide cholinephosphotransferase and phosphatidylethanolamine:ceramide ethanolaminephosphotransferase were left unchanged. Dietary olive oil also enhanced the activity of acidic sphingomyelinase, but not that of neutral sphingomyelinase. The present data indicate that dietary olive oil v. coconut fat has opposite effects on total plasma cholesterol and sphingomyelin concentrations. The lower plasma sphingomyelin levels observed in olive-oil-fed, as compared with coconut-fat-fed rats, may be explained by a simultaneous elevation and reduction in sphingomyelin catabolism and synthesis respectively, as based on the measured enzyme activities.

Animals↗
PubMed2001

Capillary gas chromatography-mass spectrometry quantitative determination of hydroxytyrosol and tyrosol in human urine after olive oil intake.

Recent in vitro studies have demonstrated antioxidant properties of some virgin olive oil phenolic compounds. One of the prerequisites to extrapolate these data to an in vivo situation is the knowledge of their bioavailability in humans. In the present work we describe an analytical method which enables us to perform hydroxytyrosol and tyrosol quantitative determinations in human urine. This method was successfully used in bioavailability studies of both phenolic compounds after acute olive oil administration. Virgin olive oil was administered to healthy volunteers after a low phenolic diet. The dose administered of both phenolic compounds was estimated in reference to free forms of hydroxytyrosol and tyrosol present in virgin olive oil extracts before and after being submitted to hydrolytic conditions. These conditions mimic those occurring during digestion. Urine samples were collected before and after acute olive oil intake and analyzed by capillary gas chromatography-mass spectrometry. Hydroxytyrosol and tyrosol urinary recovery increased in response to olive oil administration, obtaining maximal values in the first 4 h. Our results further indicate that hydroxytyrosol and tyrosol are mainly excreted in conjugated form, since only 5.9 +/- 1.4% (hydroxytyrosol) and 13.8 +/- 5.4% (tyrosol) of the total amounts excreted in urine were in free form.

Adult↗
PubMed2005

In vivo antiatherogenic properties of olive oil and its constituent lipid classes in hyperlipidemic rabbits.

BACKGROUND AND AIM: The consumption of olive oil has been associated with lower incidence of cardiovascular disease in the Mediterranean countries. This may be due in part to the action of platelet-activating factor (PAF) antagonists which we have previously demonstrated to be present in olive oil. In order to assess the in vivo effects of olive oil lipids and PAF in the development of atherosclerosis, the effects of diet supplementation with olive oil (OO), olive oil polar lipid extract (OOPLE) and olive oil neutral lipid extract (OONLE) were studied in rabbits fed a cholesterol-enriched diet. METHODS AND RESULTS: Rabbits were fed for 45 days with atherogenic diet (Group A) supplemented with OO (Group B), OOPLE (Group C) or OONLE (Group D). Lipoprotein profiles, plasma in vitro oxidation, blood PAF levels, PAF-induced platelet aggregation and PAF-acetylhydrolase (PAF-AH) activity, were measured on day 0 and 45. Atherosclerotic lesions formed in the aortic wall and wall elasticity were assessed on day 45. Changes in lipid profile were in accordance with previous studies. Blood PAF levels were higher in group A and decreased in group D on day 45. In rabbits fed an atherogenic diet (Group A) blood PAF and PAF-AH increased, atherosclerotic lesions formed and the elasticity of vessel walls declined. In animals fed olive oil (Group B) or OOPLE (Group C) blood PAF-AH increased, platelet aggregation was attenuated, less oxidation occurred in plasma, lesion thickness was reduced and vessel walls retained elasticity. Most of these beneficial changes were not seen in animals fed OONLE (Group D) although blood PAF and plasma oxidation were lower. CONCLUSIONS: The antiatherogenic effects of OO result from OOPLE. The beneficial effect of these factors is linked to PAF metabolism and proaggregant activity.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed2006

Antioxidant evaluation and oxidative stability of structured lipids from extravirgin olive oil and conjugated linoleic acid.

Structured lipid (SL) was synthesized from extravirgin olive oil (EVOO) and conjugated linoleic acid (CLA) via a lipase-catalyzed reaction. CLA provides a variety of health benefits, but it is not consumed in free fatty acid form. The synthesized SL olive oil contained 42.5 mol % CLA isomers, and the major isomers were cis-9,trans-11-CLA (16.9 mol %) and trans-10,cis-12-CLA (24.2 mol %). The antioxidant activity determined by the radical scavenging capacity with the 2,2-diphenyl-1-picrylhydrazyl radical was lower in SL olive oil than in EVOO. The oxidative stability was also lower in SL olive oil since it had a higher peroxide value, rho-anisidine value, and 2-thiobarbituric acid reactive substances values during 20 days of storage at 60 degrees C. This observation could be due to the reduction in the natural phenolic compounds (97%) and tocopherols (56%), and the incorporated CLA with two conjugated double bonds in the SL olive oil. The oxidative stability of SL olive oil was increased by added rosemary extracts at concentrations of 100, 200, and 300 ppm. The present study suggests that the SL olive oil may be a suitable way to incorporate or deliver CLA into human diets. However, the addition of a proper antioxidant would be required for improving its oxidative stability.

Antioxidants↗
PubMed2001

Effect of olive oil- and corn oil-enriched diets on the tissue mineral content in mice.

The mineral content (zinc, iron, magnesium, and calcium) in the liver, spleen, and thymus of male Balb/C mice was analyzed. Animals were fed, over 21 d, diets enriched with corn oil (FCO diet) or olive oil (FOO diet) (5% addition to standard pellet, w/w). Olive oil with predominant oleic acid (C18:1, n-9) had a quite different composition than corn oil, in which linoleic acid (C18:2, n-6) prevails. The zinc and magnesium tissue concentrations were not changed in either group. The calcium concentration in liver as well as the calcium concentration in spleen increased in mice fed both the FCO and FOO diets. Furthermore, mice fed both the FOO and FCO diets had increased spleen iron concentration. Mice fed the FCO diet had increased thymus calcium concentration compared to controls. The results show the effect of diets with unsaturated, particularly polyunsaturated fatty acids, on the calcium and iron concentration in some organs.

Animals↗
PubMed1996

Dietary non-tocopherol antioxidants present in extra virgin olive oil increase the resistance of low density lipoproteins to oxidation in rabbits.

Consumption of a range of dietary antioxidants may be beneficial in protecting low density lipoprotein (LDL) against oxidative modification, as studies have demonstrated that antioxidants other than vitamin E may also function against oxidation of LDL in vitro. In the present study, the effect of polyphenol antioxidants on the susceptibility of LDL to copper-mediated oxidation was investigated after feeding semi-purified diets to 3 groups of New Zealand white (NZW) rabbits. All diets comprised 40% energy as fat with 17% energy as oleic acid. Dietary fatty acid compositions were identical. Oils with different polyphenol contents were used to provide the dietary source of oleic acid-refined olive oil, extra virgin olive oil and Trisun high oleic sunflower seed oil. Polyphenolic compounds (hydroxytyrosol and p-tyrosol) could only be detected in the extra virgin olive oil. Vitamin E was equalised in all diets. LDL oxidizability in vitro was determined by continuously monitoring the copper-induced formation of conjugated dienes after 6 weeks of experimental diet feeding. The lag phase before demonstrable oxidation occurred was significantly increased in the high polyphenol, extra virgin olive oil group (P < 0.05) when compared with combined results from the low polyphenol group (refined olive oil and Trisun), even though the LDL vitamin E concentration in the high polyphenol group was significantly lower. The rate of conjugated diene formation was not influenced by the presence of dietary polyphenols. Results demonstrate that antioxidants, possibly phenolic compounds which are present only in extra virgin olive oil, may contribute to the endogenous antioxidant capacity of LDL, resulting in an increased resistance to oxidation as determined in vitro.

Animals↗
PubMed2006

Biosensor measurements of polar phenolics for the assessment of the bitterness and pungency of virgin olive oil.

Bitterness and pungency, sensory quality attributes of virgin olive oil, are related to the presence of phenolic compounds. Fast and reliable alternatives for the evaluation of sensory attributes and phenolic content are desirable, as sensory and traditional analytical methods are time-consuming and expensive. In this study, two amperometric enzyme-based biosensors (employing tyrosinase or peroxidase) for rapid measurement of polar phenolics of olive oil were tested. The biosensor was constructed using disposable screen-printed carbon electrodes with the enzyme as biorecognition element. The sensor was coupled with a simple extraction procedure and optimized for use in flow injection analysis. The performance of the biosensor was assessed by measuring a set of virgin olive oils and comparing the results with data obtained by the reference HPLC method and sensory scores. The correlations between the tyrosinase- and peroxidase-based biosensors and phenolic content in the samples were high (r = 0.82 and 0.87, respectively), which, together with a good repeatability (rsd = 6%), suggests that these biosensors may represent a promising tool in the analysis of the total content of phenolics in virgin olive oils. The correlation with sensory quality attributes of virgin olive oil was lower, which illustrates the complexity of sensory perception. The two biosensors possessed different specificities toward different groups of phenolics, affecting bitterness and pungency prediction. The peroxidase-based biosensor showed a significant correlation (r = 0.66) with pungency.

Biosensing Techniques↗
PubMed1998

Free radical-scavenging properties of olive oil polyphenols.

Plants in the Mediterranean basin, such as vine and olive trees, have developed an array of antioxidant defences to protect themselves from environmental stress. Accordingly, the incidence of coronary heart disease and certain cancers is lower in the Mediterranean area, where olive oil is the dietary fat of choice. As opposed to other vegetable oils, extra virgin olive oil, which is obtained by physical pressure from a whole fruit, is rich in phenolic components that are responsible for the particular stability of the oil. We have investigated the scavenging actions of some olive oil phenolics, namely hydroxytyrosol and oleuropein, with respect to superoxide anion generation, neutrophils respiratory burst, and hypochlorous acid. The low EC50S indicate that both compounds are potent scavengers of superoxide radicals and inhibitors of neutrophils respiratory burst: whenever demonstrated in vivo, these properties may partially explain the observed lower incidence of CHD and cancer associated with the Mediterranean diet.

Antioxidants↗
PubMed2002

Extra virgin olive oil phenols and markers of oxidation in Greek smokers: a randomized cross-over study.

OBJECTIVE: To examine the effect of a low phenol olive oil and high phenol olive oil on markers of oxidation and plasma susceptibility to oxidation in normolipaemic smokers. DESIGN: Randomized single-blind cross-over trial with two intervention periods. SETTING: The Medical School and University Hospital of the University of Crete, Heraklion, Crete, Greece. SUBJECTS: Twenty-five healthy males and females completed the study. INTERVENTIONS: Each intervention was of three weeks duration and intervention periods were separated by a two week washout. Seventy grams of extra virgin olive oil was supplied to each subject per day in the intervention periods. The olive oils supplied differed in their phenol content by 18.6 mg/day. Two fasting venous blood samples were taken at the end of each intervention period. RESULTS: The markers of antioxidant capacity measured in fasting plasma samples (total plasma resistance to oxidation, concentrations of protein carbonyl as a marker of protein oxidation, malondialdehyde and lipid hydroperoxides as markers of lipid oxidation and the ferric reducing ability of plasma) did not differ significantly between the low and high phenol olive oil diets. CONCLUSIONS: No effect of olive oil phenols on markers of oxidation in smokers was detected. It may be that the natural concentrations of phenols in olive oil are too low to produce an effect in the post-absorptive phase. Possible reasons for period effects and interactions between diet and administration period need attention to aid further cross-over trials of this kind. SPONSORSHIP: Unilever Research Vlaardingen, The Netherlands.

Adult↗
PubMed2004

Effects of differing phenolic content in dietary olive oils on lipids and LDL oxidation--a randomized controlled trial.

BACKGROUND: Evidence from in vitro studies suggests that antioxidant olive oil phenolic compounds can prevent LDL oxidation. However, in vivo evidence in support of this hypothesis is sparse. AIM OF THE STUDY: to establish the antioxidant effect of olive oils with differences in their phenolic compounds content in humans METHODS: A controlled, double blind, cross-over, randomized, clinical trial using three similar olive oils with increasing phenolic concentration (from 0 to 150 mg/Kg) was conducted in 30 healthy volunteers. Olive oils were administered over three periods of 3 weeks preceded by two-week washout periods. RESULTS: Urinary tyrosol and hydroxytyrosol increased (p < 0.020), in vivo plasma oxidized LDL decreased (p = 0.006), and ex vivo resistance of LDL to oxidation increased (p = 0.012) with the phenolic content of the olive oil administered. After virgin olive oil administration, an increase (p = 0.029) was observed in HDL cholesterol levels. CONCLUSIONS: Sustained consumption of virgin olive oil with the high phenolic content was more effective in protecting LDL from oxidation and in rising HDL cholesterol levels than that of other type of olive oils. Dose-dependent changes in oxidative stress markers, and phenolic compounds in urine, were observed with the phenolic content of the olive oil administered. Our results support the hypothesis that virgin olive oil consumption could provide benefits in the prevention of oxidative processes.

Antioxidants↗
PubMed1995

Antibacterial polyphenols from olive oil mill waste waters.

Olive oil vegetation waters (VW) were highly toxic to both phytopathogenic Pseudomonas syringae (Smith, Yung et al.) pv. savastanoi (Gram-negative) and Corynebacterium michiganense (Gram-positive) and showed bactericidal activity in their original concentration (in raw form). Among the main polyphenols, present in the waste waters, methylcatechol proved to be the most toxic to Ps. savastanoi at 10(-4) mol l-1, and also demonstrated bactericidal activity, while on Coryne. michiganense it was only slightly active; catechol and hydroxytyrosol were less active on Ps. savastanoi, but inactive on Coryne. michiganense; tyrosol and its synthetic isomers 1,2- and 1,3-tyrosol were completely inactive on both bacteria. Among the derivatives of VW polyphenols considered, acetylcatechol and guaiacol were selectively toxic for Ps. savastanoi, while o-quinone was strongly toxic for both bacteria. The minor carboxylic polyphenols of VW at 10(-4) mol l-1 were all inactive on the bacteria. VW, catechol, 4-methylcatechol and the less abundant carboxylic polyphenols proved to be toxic on Hep2 human cells. Finally the possibility of using the active polyphenols in agriculture in an integrated pest management program for the protection of the olive plant is discussed.

Anti-Bacterial Agents↗
PubMed2003

Rapid quantitative assessment of the adulteration of virgin olive oils with hazelnut oils using Raman spectroscopy and chemometrics.

The authentication of extra virgin olive oil and its adulteration with lower-priced oils are serious problems in the olive oil industry. In addition to the obvious effect on producer profits, adulteration can also cause severe health and safety problems. A number of techniques, including chromatographic and spectroscopic methods, have recently been employed to assess the purity of olive oils. In this study Raman spectroscopy together with multivariate and evolutionary computational-based methods have been employed to assess the ability of Raman spectroscopy to discriminate between chemically very closely related oils. Additionally, the levels of hazelnut oils used to adulterate extra virgin olive oil were successfully quantified using partial least squares and genetic programming.

Corylus↗
PubMed2004

Effect of olive ripening degree on the oxidative stability and organoleptic properties of cv. Nostrana di Brisighella extra virgin olive oil.

The evaluation of the influence of olive ripening degree on the stability of extra virgin olive oils by the determination of the oxidative stability index, the DPPH(*) radical test, and the quali-quantitative analysis of phenolic compounds, as well as the study of the variation of their sensory profiles, plays a key role in the assessment of the overall olive oil quality. Olives of the cv. Nostrana di Brisighella grown in the north-central Italian region of Emilia-Romagna were picked at four different stages of ripeness and immediately processed in an experimental mill. The polar extracts of oil samples were submitted to spectrophotometric analysis of total phenols and o-diphenols and to liquid chromatographic determination of their quali-quantitative profile (HPLC-DAD/MSD). To attain a complete description of oil samples, fatty acid composition, ultraviolet indices (K(232), K(270), and deltaK), free acidity degree, and peroxide value were also determined according to the European Union methods stated in Regulation 2568/91 (1, Off. J. Eur. Communities 1991, L248, 1-82). Sensory quantitative descriptive analysis (QDA) and triangular tests were performed to establish the influence of olive ripening degree on the resulting oil's organoleptic properties. The evolution of the analytical parameters studied shows that the ripeness stage of Nostrana di Brisighella olives that yields the best oil corresponds to a Jaén index value between 2.5 and 3.5. Oils produced from olives harvested within this time frame present a superior sensory profile accompanied by the highest possible chemical and nutritional properties.

Chromatography, High Pressure Liquid↗
PubMed2001

Effects of minor constituents (non-glyceride compounds) of virgin olive oil on plasma lipid concentrations in male Wistar rats.

We aimed to assess the effects of minor constituents (MC) from virgin olive oil upon the plasma lipid profile of experimental animals. Therefore, 32 Wistar rats were fed for 6 weeks with one of four different diets with a similar fatty acid composition but different MC: high-oleic sunflower oil (HOSO), virgin olive oil (VOO), 400%-MC enriched olive oil (EOO) and MC poor (impoverished) olive oil (IOO). At the end of the week 6 of dietary treatment, blood samples were obtained for analysis of lipid composition. A statistically significant influence was observed upon both total HDL (1.593+/-0.4, 1.204+/-0.212, 0.991+/-0.244 and 0.827+/-0.279 mmol/L for EOO, HOSO, VOO and IOO, respectively, Kruskal-Wallis test, P<0.05) and HDL(2)cholesterol levels (1.16+/-0.26, 0.576+/-0.191, 0.585+/-0.216 and 0.583+/-0.207 mmol/L for EOO, HOSO, VOO and IOO, respectively, Kruskal-Wallis test, P<0.05). No statistically significant effect was observed upon LDL-cholesterol or triglycerides. Thus, MC supplementation has beneficial effects on HDL concentrations in Wistar rats.

Animals↗