Eva Gimeno

The effects of harvest and extraction methods on the antioxidant content (phenolics, α-tocopherol, and β-carotene) in virgin olive oil

We studied the effects of harvesting and two processing systems (two-phase centrifugation and three-phase centrifugation) on olive oil quality. Oils extracted from high quality olives do not differ in free acidity, peroxide value and ultraviolet light absorption. Nor was the fatty acid composition affected. However, the antioxidant content of the oil was higher from green olives than from ripe olives. On the other hand, we determined that neither extraction method affects the presence of α-tocopherol and β-carotene, however, the phenolic content is higher in the two-phase method due to the addition of lukewarm water that is used to dilute the olive paste.

Rapid determination of vitamin E in vegetable oils by reversed-phase high-performance liquid chromatography

A quick and direct method for measuring tocopherols (alpha, beta+gamma and delta) in vegetable oils has been developed using RP-HPLC with UV detection. Previous extraction of tocopherols is not required. The oil is diluted in hexane and an aliquot is mixed with ethanol containing an internal standard (alpha-tocopherol acetate). The chromatographic system consists of an ODS-2 column with a methanol-water mobile phase. Tocopherols are detected at 292 nm in less than 5 min after injection. The method is precise (RSD=2.69%) and has a high mean recovery (98.14%).

Effect of ingestion of virgin olive oil on human low-density lipoprotein composition

Objective: To measure the incorporation of oleic acid and antioxidants (phenols and vitamin E) to low density lipoprotein (LDL) after acute and short-term ingestion of virgin olive oil. To study whether this incorporation contributes to an increase in LDL resistance to oxidation.Setting: Department of Food and Nutrition, University of Barcelona, Spain and Department of Lipids and Cardiovascular Epidemiology, IMIM, Barcelona, Spain.Subjects: Sixteen healthy volunteers aged 25–65 y.Design and interventions: To observe the change in the fatty acid profile, vitamin E, phenolic compounds and LDL oxidation-related variables after the postprandial phase and after daily ingestion of olive oil for one week.Results: Few changes were observed in the postprandial phase. However, after a week of olive oil consumption there was an increase in oleic acid (P=0.015), vitamin E (P=0.047), phenolics (P=0.021) and lag time (P=0.000), and a decrease in the maximum amount of dienes (P=0.045) and oxidation rate (P=0.05).Conclusion: After ingestion of virgin olive oil, an increase in antioxidants and oleic acid in LDL was observed as well as an improvement of LDL resistance to oxidation. Our results support the idea that daily ingestion of virgin olive oil could protect LDL from oxidation.Sponsorship: This study was supported by a research grant from Spain (ALI 97-1607-C02-02).

Simultaneous determination of α-tocopherol and β-carotene in olive oil by reversed-phase high-performance liquid chromatography

Abstract A reversed-phase high-performance liquid chromatographic method was developed for the determination, in one run, of α-tocopherol and β-carotene in virgin olive oil. The method involved a rapid saponification and a later extraction with a mixture of hexane–ethyl acetate. The chromatographic system consists of an ODS-2 column with a mobile phase of methanol–water–butanol and a diode-array detector. Linearity, precision, recovery and sensitivity were satisfactory. The main advantage of the proposed method is the speed and simultaneous determination of both compounds at the same time.

Postprandial and short-term effects of dietary virgin olive oil on oxidant/antioxidant status

It is generally believed that virgin olive oil consumption has beneficial effects, but little is known about its effects postprandially on oxidant/antioxidant status. The aim of this study was to determine changes in oxidative stress biomarkers and lipid profile after a single dose of virgin olive oil and after 1 wk of daily consumption. Sixteen subjects (9 men, 7 women) ingested 50 mL of virgin olive oil in a single dose. Blood samples were collected from 0 to 24 h. Thereafter, 14 participants (8 men, 6 women) followed a 1-wk 25 mg/d virgin olive oil dietary intervention. Blood samples were collected at the end of this period. Serum TAG (P=0.016), plasma FA (P<0.001) and lipid peroxidation products in plasma (P<0.001) and VLDL (P=0.007) increased, reaching a peak at 4–6 h, and returning to baseline values at 24 h after oil ingestion. The opposite changes were observed in plasma glutathione peroxidase (P=0.001) and glutathione reductase (GR) (P=0.042). No changes in LDL lipid peroxidation or resistance to oxidation were observed postprandially. At 24 h, plasma oleic acid remained increased (P<0.05) and resistance of LDL to oxidation improved (P<0.05). After 1 wk of virgin olive oil consumption, plasma oleic acid (P=0.031), resistance of LDL to oxidation (P<0.05), and plasma GR activity (P=0.005) increased. These results indicate that changes in oxidant/antioxidant status occur after oral virgin olive oil. Virgin olive oil consumption could provide short-term benefits for LDL resistance to oxidation and in glutathione-related enzyme activities.

Changes in the phenolic content of low density lipoprotein after olive oil consumption in men. A randomized crossover controlled trial.

Olive oil decreases the risk of CVD. This effect may be due to the fatty acid profile of the oil, but it may also be due to its antioxidant content which differs depending on the type of olive oil. In this study, the concentrations of oleic acid and antioxidants (phenolic compounds and vitamin E) in plasma and LDL were compared after consumption of three similar olive oils, but with differences in their phenolic content. Thirty healthy volunteers participated in a placebo-controlled, double-blind, crossover, randomized supplementation trial. Virgin, common, and refined olive oils were administered during three periods of 3 weeks separated by a 2-week washout period. Participants were requested to ingest a daily dose of 25 ml raw olive oil, distributed over the three meals of the day, during intervention periods. All three olive oils caused an increase in plasma and LDL oleic acid (P < 0.05) content. Olive oils rich in phenolic compounds led to an increase in phenolic compounds in LDL (P < 0.005). The concentration of phenolic compounds in LDL was directly correlated with the phenolic concentration in the olive oils. The increase in the phenolic content of LDL could account for the increase of the resistance of LDL to oxidation, and the decrease of the in vivo oxidized LDL, observed in the frame of this trial. Our results support the hypothesis that a daily intake of virgin olive oil promotes protective LDL changes ahead of its oxidation.

Rapid high-performance liquid chromatographic method for the simultaneous determination of retinol, α-tocopherol and β-carotene in human plasma and low-density lipoproteins

A reversed-phase HPLC method with diode-array detection was used to simultaneously determine retinol, α-tocopherol and β-carotene in human plasma and low-density lipoproteins. An aliquot of sample was de-proteinized with ethanol containing α-tocopherol acetate as internal standard, and the analytes were extracted twice with hexane. The solvent was evaporated to dryness under a stream of nitrogen and the residue was redissolved in methanol to be injected directly into the HPLC system. A multiple solvent system based on methanol, butanol and water at a flow-rate of 2 ml/min and held at 45°C provided clear separation of these compounds in only 8 min. The method showed good linearity, precision and accuracy for all compounds. Owing to its simplicity, this method may be useful in routine clinical and epidemiological work.

Interaction of Olive Oil Phenol Antioxidant Components with Low-density Lipoprotein

Phenolic compounds have shown to inhibit LDL oxidation in vitro and ex vivo; however, they are hydrosoluble compounds while LDL is a lipoprotein. Analysis of phenolic compounds in LDLs by HPLC is necessary to demonstrate their binding capacity to lipoproteins. We developed and validated a solid phase extraction method (SPE) that allowed us the purification of LDL samples and their analysis by HPLC. This methodology allowed us to demonstrate the in vitro binding capacity of tyrosol, one of the main phenolic compounds in olive oil, to LDL. In the intervention dietary study with volunteers, food rich in phenolic compounds affected LDL composition. Changes in LDL phenolics composition are not observed after the short-term ingestion of food rich in phenolic compounds. However, after one week of olive oil consumption and Mediterranean diet there was an increase in phenolics (p=0.021). An accumulative effect seems necessary to observe significative differences in LDL phenolic composition.