Evaluation of antioxidant activities of phenolic compounds from two extra virgin olive oils

The aim of this work was to investigate the antioxidant properties of two varieties of olive oil (Chétoui and Chemlali), and to study the protective effect of phenolic extract (PE) from these varieties against low density lipoprotein (LDL) oxidation in vitro. Antioxidant activities were examined as well, using different radical scavenging assays: radical scavenging activity by DPPH, and total antioxidant status by ABTS. The antioxidant effect of the oils on human LDL was evaluated by measuring levels of conjugated dienes and polyunsaturated fatty acids. Chemlali oil was less rich in total phenols (158 mg/kg) than Chétoui oil (395 mg/kg) (p < 0.05). The highest antioxidant activity was attributed to Chétoui oil (78.56% vs. 37.23% of DPPH and 2.42 vs. 0.61 mmol Trolox/kg; p < 0.05). Chétoui PE had a significantly greater inhibitory effect on LDL oxidation than Chemlali PE (lag time = 116 ± 6.05 min vs. 64 ± 11.31 min at 0.3 mg/l of PE respectively; p < 0.05). The differences in quantity and quality of the studied oils influenced their biological activities and they could provide beneficial effects in cardiovascular disease by inhibiting LDL oxidation.     

Effect of olive cultivar on bioaccessibility and antioxidant activity of phenolic fraction of virgin olive oil

Aim

This study aims to characterize the phenolic profile and antioxidant capacity of seven monovarietal virgin olive oils (VOOs) and evaluate their in vitro gastrointestinal stability.

Methods

‘Picual’, ‘Blanqueta’, ‘Sevillana’, ‘Habichuelero’, and ‘Chetoui’ olive cultivars were selected for VOO extraction. The oils were subjected to in vitro digestion. The recovery index (RI) of phenolic compounds after each digestion step and the bioaccessibility index (BI) were evaluated. In addition, the antioxidant activity of the bioaccessible fraction (BF) of VOOs was determined by DPPH, ABTS, and ORAC assays, as well as by studying the intracellular reactive oxygen species in Caco-2 cells.

Results

Differences were found in the composition of phenolic compounds in VOOs depending on cultivars. During the digestive process, important losses of phenolic compounds were observed between the buccal and duodenal steps, unlike HTy and Ty, which presented increased recovery due to the hydrolysis of secoiridoid derivatives. Differences in the bioaccessibility of phenolic compounds were found between varieties of VOOs. ‘Sevillana’ VOO had the highest total bioaccessibility (36%), followed by the ‘Picual’ (19%), ‘Chetoui’ (17%), ‘Habichuelero’ (10%), and ‘Blanqueta’ (8%) varieties. The BF of all the varieties of VOO showed similar radical ABTS scavenging capacity, ‘Chetoui’, and ‘Blanqueta’-BF having the highest radical DPPH scavenging capacity, and ‘Habichuelero’ and ‘Picual’-BF showing protective effects against the peroxyl radical measured by ORAC_FL assay. All VOO-BFs presented decreases in ROS levels in Caco-2 cells.

Conclusions

Our results suggest differences in the bioaccessibility of phenolics from diverse VOO varieties, which could lead to different biological properties. Therefore, this study represents a first step toward the development of novel dietary strategies focusing on the phenolic supplementation of different VOOs to preserve human health.

     

Differential anti-inflammatory effects of phenolic compounds from extra virgin olive oil identified in human whole blood cultures

OBJECTIVE: The olive oil-rich Mediterranean diet protects against cardiovascular disease, which involves inflammatory processes. This study investigated the effects of phenolic compounds found in extra virgin olive oil on inflammatory mediator production by human mononuclear cells. METHODS: Diluted human blood cultures were stimulated with lipopolysaccharide in the presence of phenolics (vanillic, p-coumaric, syringic, homovanillic and caffeic acids, kaempferol, oleuropein glycoside, and tyrosol) at concentrations of 10(-7) to 10(-4) M. Concentrations of the inflammatory cytokines tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6 and of the inflammatory eicosanoid prostaglandin E2 were measured by enzyme-linked immunosorbent assay. RESULTS: Oleuropein glycoside and caffeic acid decreased the concentration of interleukin-1beta. At a concentration of 10(-4) M, oleuropein glycoside inhibited interleukin-1beta production by 80%, whereas caffeic acid inhibited production by 40%. Kaempferol decreased the concentration of prostaglandin E2. At a concentration of 10(-4) M, kaempferol inhibited prostaglandin E2 production by 95%. No effects were seen on concentrations of interleukin-6 or tumor necrosis factor-alpha and there were no effects of the other phenolic compounds. CONCLUSIONS: Some, but not all, phenolic compounds derived from extra virgin olive oil decrease inflammatory mediator production by human whole blood cultures. This may contribute to the antiatherogenic properties ascribed to extra virgin olive oil.     

Effect of phenol-rich extra virgin olive oil on markers of oxidation in healthy volunteers

OBJECTIVE: We studied whether consumption of phenol-rich extra virgin olive oil affects the susceptibility of low density lipoproteins (LDL) to oxidation and other markers of oxidation in humans. DESIGN: Randomized cross-over intervention trial, stratified according to sex, age and energy intake. SETTING: Division of Human Nutrition and Epidemiology, Wageningen University, The Netherlands. SUBJECTS: Forty-six healthy men and women completed the study. INTERVENTION: Subjects consumed two diets supplying 69 g per day of extra virgin olive oil either rich or poor in phenols for 3 weeks each. The mean difference in phenol intake between the treatments was 18 mg per day. Vitamin E intake was low during the whole study. Fasting blood samples were taken twice at the end of each period. RESULTS: Resistance of LDL and high density lipoprotein (HDL) to oxidation was not affected by treatment. The mean lag time of copper-induced formation of conjugated dienes was 1.6 min shorter in LDL and 0.4 min longer in HDL after the high phenol diet. Other markers of antioxidant capacity in plasma were also not affected: mean lipid hydroperoxides were 0.07 micromol/l higher, mean malondialdehydes were 0.001 micromol/l higher, mean protein carbonyls were 0.001 nmol/mg protein lower, and the mean ferric reducing ability of plasma (FRAP) was 0.006 mmol/l higher after the high phenol diet. All 95% confidence intervals enclosed zero. Serum cholesterol concentrations were not affected by the treatment. CONCLUSION: Consumption of 18 mg per day of phenols from extra virgin olive oil for 3 weeks did not affect LDL or HDL oxidation or other markers of antioxidant capacity in fasting plasma samples.     

Dietary enrichment of apolipoprotein E-deficient mice with extra virgin olive oil in combination with seal oil inhibits atherogenesis

Background  

In this study we investigated the antiatherogenic effect of dietary enrichment of a combination of extra virgin olive oil (EVO) and seal oil on apolipoprotein E-deficient (apoE^-/-).     

Influence of extra virgin olive oil diet enriched with hydroxytyrosol in a chronic DSS colitis model

Purpose

Recent epidemiological studies have shown that habitual consumption of extra virgin olive oil (EVOO), the characteristic culinary fat of the Mediterranean area, is effective in the prevention of diverse types of digestive disorders such as inflammatory bowel disease. Many of these benefits are, in addition to its high proportion of oleic acid, due to the high content of phenolic compounds.

Methods

Six-week-old mice were randomized into three dietary groups: standard, EVOO and hydroxytyrosol-enriched EVOO. After 30?days, mice that were exposed to 3% DSS for 5?days developed acute colitis that progressed to severe chronic inflammation during a regime of 21?days of water.

Results

Diets enriched with EVOO significantly attenuated the clinical and histological signs of damage, improving results from disease activity index and reducing about 50% the mortality caused by DSS. Moreover, hydroxytyrosol supplement showed better results. Cytokines study showed that TNF-α was maintained near to sham control and IL-10 levels were significantly improved in EVOO and EVOO plus hydroxytyrosol diet-DSS groups. In the same way, COX-2 and iNOS were downregulated, and the activation of p38 MAPK was reduced. We also observed a higher significant reduction in iNOS in hydroxytyrosol-enriched EVOO compared with EVOO alone.

Conclusions

EVOO diets exerted a noteworthy beneficial effect in chronic DSS-induced colitis by cytokine modulation and COX-2 and iNOS reduction via downregulation of p38 MAPK. In addition to the beneficial effect by EVOO, supplementation of the diet with hydroxytyrosol may improve chronic colitis through iNOS downregulation plus its antioxidant capacity.     

Phenolic compounds and antioxidant activity of Spanish commercial grape juices

Evaluation of the antioxidant activity of components of the diet is important in order to establish healthy consumption patterns. Data are reported here on the antioxidant activity (FRAP and ABTS), of 20 commercial grape juices and 10 typical Spanish wines and on their content of total phenolic compounds, anthocyanins, flavonoids and 10 individual phenolic compounds (flavanols, benzoic acids and cinnamic acids, measured by HPLC-UV). Red grape juices had a significantly higher (p < 0.05) concentration of total phenols (1177 vs. 744 mg gallic acid/L), flavonoids (98 vs. 63 mg catechin/L) and a higher antioxidant activity (9.16 vs. 2.83 meq Trolox/L) in comparison to white grape juices. In comparison to the white wines, white grape juices contained more total phenols (744 vs. 286 mg gallic acid/L) and flavonoids (63 vs. 29 mg catechin/L) and evidenced higher antioxidant activity (p < 0.05). In comparison to the red wines, a lower content of total phenols (286 vs. 2358 mg gallic acid/L) and flavonoids (228 vs. 29 mg catechin/L) and an absence of anthocyanins were observed in the white wines, which are therefore less antioxidant. Although a two-fold higher concentration of antioxidant compounds was found in red wines than in red grape juices, the latter may be a good option for all age groups because of the absence of alcohol and the potentially beneficial health effects of their phenolic composition and elevated antioxidant activity.     

Dietary exchange of an olive oil and sunflower oil blend for extra virgin olive oil decreases the estimate cardiovascular risk and LDL and apolipoprotein AII concentrations in postmenopausal women

BACKGROUND: Dietary supplementation with Virgin olive oil is considered cardioprotective. Decreasing LDL and apolipoprotein (apo) AII-lipoproteins is also appropriate for CHD protection and treatment. AIM: To study the effects of an 8%En dietary exchange of linoleic acid for oleic acid on serum and lipoprotein levels and serum and LDL-TBARS in postmenopausal women consuming a diet rich in fat (46%En; saturated/monounsaturated/polyunsaturated profile: 1.1/1.9/1). EXPERIMENTAL DESIGN: 14 postmenopausal women (63 +/- 11 years) were assigned to exchange during 28-day dietary period the culinary oil used for years consisting in a blend of olive oil plus sunflower oil (SO) for extra virgin olive oil (EVOO). SO and EVOO represented 62% of the total lipid intake. DETERMINATIONS: Dietary intakes, serum Lp(a), and cholesterol, triglycerides, phospholipids, protein, apolipoproteins AI, AII, B were determined in serum and lipoproteins. RESULTS: The dietary intervention decreased serum total cholesterol (TC), phospholipids, apo AII (all, p < 0.001) and apo B (p < 0.01). Except for triglycerides, all components of the LDL fraction decreased (at least, p < 0.05). HDL-cholesterol was not affected but HDL-phospholipids and HDL-lipids decreased (at least, p < 0.01). VLDL-apo B and VLDL-proteins decreased (all, p < 0.001). Serum Lp(a), TBARS and LDL-TBARS were not affected by the dietary exchange. The estimate of 10-year cardiovascular risk decreased (p < 0.05). Apo AII (p = 0.061) and LDL-cholesterol (p < 0.05) underwent greater modifications in normocholesterolemics, while LDL-phospholipids (p = 0.094), experienced greater alterations in hypercholesterolemics. No significant interaction was observed between dietary exchange and age (> or <65 yrs). CONCLUSIONS: These findings suggest that the dietary exchange of an olive oil and sunflower oil blend for extra virgin olive decreases LDL and apo AII levels, and the estimate of 10-year cardiovascular risk.     

Hypolipidimic and antioxidant activities of virgin olive oil and its fractions in 2,4-diclorophenoxyacetic acid-treated rats

Objective

We examined the effects of extra virgin olive oil (EVOO) and its hydrophilic and lipophilic fractions on serum lipids, oxidative stress, and morphologic and functional liver damages induced by 2,4-diclorophenoxyacetic acid (2,4-D).

Methods

Male Wistar rats were divided randomly into eight groups: control; 2,4-D at a dose of 5 mg/kg of body weight (2,4-D); 2,4-D plus EVOO (2,4-D/EVOO); 2,4-D plus the hydrophilic fraction (2,4-D/OOHF); 2,4-D plus the lipophilic fraction (2,4-D/OOLF); only EVOO (EVOO); only the hydrophilic fraction (OOHF); and only the lipophilic fraction (OOLF). These components were administered daily by gavage for 4 wk.

Results

A hepatic architecture aberration, increased activities of aspartate and alanine aminotransferase enzymes, total and low-density lipoprotein cholesterol, and malondialdehyde (MDA) level, and a decreased antioxidant defense system were observed in the 2,4-D group. The administration of EVOO restored the damage caused by 2,4-D by a significant decrease of plasma total and low-density lipoprotein levels and a moderate increase of high-density lipoprotein cholesterol. The 2,4-D/OOHF group exhibited a pronounced enhancement of the antioxidant defense system by an increase of superoxide dismutase, catalase, and glutathione peroxidase levels and a decrease of plasma and liver MDA levels. However, less improvement in the liver histoarchitecture and antioxidant status was observed in rats supplemented with OOLF diet, despite its richness in α-tocopherol.

Conclusion

Extra virgin olive oil may be a potential functional food source of antioxidants than can decrease the frequency of cardiovascular diseases and liver damage.     

Phenolic compounds,carotenoids and antioxidant activity of three tropical fruits

Major compounds (i.e. phenolic compounds and carotenoids) were analysed in the extracts of the edible part of three tropical fruits: the Andean blackberry, the naranjilla and the tree tomato. Ellagitannins and anthocyanins were predominant in blackberries and phenolic composition can be used to differentiate the two species studied. Similar phenolic composition occurred in red and yellow tree tomato except for anthocyanins which were absent in the yellow tree tomato. Phenolic acids were detected in the naranjilla pulp. Carotenoids were analysed in the fruits. The composition in carotenoids was similar in the two varieties of tree tomato and their vitamin A activity was calculated. Carotenol fatty acid esters were predominant. β-Cryptoxanthin esters and β-carotene were the major carotenoids. The carotenoid content was high compared to literature data, providing an important high vitamin A activity. In blackberries and naranjilla, this class of compounds was found only at trace level. Finally, ORAC values were estimated in different solvent extracts and results were compared with published data in common fruits.     

Virgin Olive Oil Study (VOLOS): vasoprotective potential of extra virgin olive oil in mildly dyslipidemic patients

Summary Background In vitro, olive phenols exert potent antioxidant and enzyme-modulating activities. Aim of the study We comparatively evaluate, in mildly dyslipidemic patients, the vasoprotective potential of extra virgin olive oil. Methods 22 patients were administered 40 mL/day of either extra-virgin, i. e. phenol rich, or refined, i. e. phenol poor, olive oils (EVOO or ROO, respectively, with nearly identical fatty acid composition), with a crossover design. Each treatment was carried out for seven weeks, with four weeks of washout in between. Plasma antioxidant capacity, serum thromboxane B₂ (TXB₂) formation, and urinary isoprostane excretion were evaluated as surrogate markers of cardioprotective potential and vascular function. Results No effects on plasma lipid/lipoprotein profile were observed. Conversely, EVOO consumption was associated with favorable effects on circulating markers. Namely, decreased serum TXB₂ production and increased plasma antioxidant capacity were observed when EVOO was administered in both treatment arms. Neither treatment had any significant effect on isoprostane excretion. Conclusions EVOO consumption by mildly dyslipidemic patients is associated with favorable changes in circulating markers of cardiovascular condition. Based on current knowledge, these effects may be associated with cardioprotection.     

Levels of lipochromes and other bioactives in virgin olive oil from new olive germplasm

The composition of virgin olive oils from three new olive cultivars, such as Arno, Tevere and Basento, has been investigated in this work. Our attention was focused on chlorophylls, carotenes, xanthophylls and other major bioactives, as well as on some analytical indices related to functionality, quality and typicality of the new products. Our analytical study showed how the new oil kinds, especially Arno oil, had an interesting qualitative-quantitative composition of the pigment fraction. Pheophytin a (within the chlorophyll subfraction) and lutein (within the carotenoid subfraction) were found to be the major natural pigments occurring in the new products. Interesting were also the concentrations of biophenols, tocopherols, and tocotrienols detected in the three new oil varieties, as well as the values of the remarkable ratio fatty acids ω₆/fatty acids ω₃ and biophenols/polyunsaturated fatty acids (PUFA) (and those of the analytical variables endurance and susceptibility to autoxidation). The chemometric analyses showed how different multivariate methods were effective in discriminating between oil varieties. Thus, these chemometrics can effectively be used for traceability or authentication of the new products. We concluded how the three new olive cultivars can actually lead to new advances in the olive growing sector.     

Bioavailability and antioxidant effects of olive oil phenolic compounds in humans: a review

Olive oil, the main source of fat in the Mediterranean diet, is a functional food which besides having a high level of monounsaturated fatty acid contains several minor components with biological properties. For some olive oil minor components, such as the antioxidant phenolic compounds, a large body of studies, mainly experimental or in animal models, have been performed. Randomized, controlled, clinical trials in humans are required to provide evidence that olive phenolic compounds contribute significantly to health benefits in order to give recommendations at population level. Here, we summarize the state of the art of the body of knowledge, and to which extent we have evidence, of the bioavailability and of the antioxidant benefits of olive oil phenolic compounds in humans.     

Administration of minor polar compound-enriched extra virgin olive oil decreases platelet aggregation and the plasma concentration of reduced homocysteine in rats

We investigated the effect of extra virgin olive oil (EVOO) on platelet aggregation and plasma concentrations of homocysteine (Hcy) redox forms in rats in relation to the minor polar compound (MPC) concentration of EVOO. We used 3 olive oil samples with similar fatty acid but different MPC concentrations: refined olive oil (RF) with traces of MPC (control oil), native EVOO with low MPC concentration (LC), and EVOO with high MPC concentration (HC) enriching LC with its own MPC. Oil samples were administered to rats by gavage (1.25 mL/kg body weight) using 2 experimental designs: acute (24-h food deprivation and killed 1 h after EVOO administration) and subacute (12-d treatment, a daily dose of oil for 12 d, and killed after 24 h of food deprivation). Platelet aggregation was induced by ADP (ex vivo tests) and a reduction in platelet reactivity occurred in cells from rats given LC in the subacute study and in cells from rats administered HC in both studies as indicated by an increase in the agonist half maximal effective concentration. HC inhibited platelet aggregation induced by low ADP doses (reversible aggregation) in cells of rats in both the acute and subacute studies, whereas LC had this effect only in the subacute experiment. Moreover, in rats administered HC in both experiments, the plasma concentration of free reduced Hcy (rHcy) was lower and Hcy bound to protein by disulfide bonds (bHcy) was greater than in RF-treated rats. bHcy was also greater in rats given LC than in RF-treated rats in the subacute experiment. Plasma free-oxidized Hcy was greater in rats given LC and HC than in those administered RF only in the subacute experiment. In conclusion, these results show that MPC in EVOO inhibit platelet aggregation and reduce the plasma rHcy concentration, effects that may be associated with cardiovascular protection.     

Serum lipid profile and inflammatory markers in the aorta of cholesterol-fed rats supplemented with extra virgin olive oil,sunflower oils and oil-products

Abstract

Extra virgin olive oil (EVOO) major and minor component anti-inflammatory effect on aorta was evaluated; Wistar rats were fed (9 weeks) on either a high-cholesterol diet (HCD) or a HCD supplemented with oils, i.e. EVOO, sunflower oil (SO), high-oleic sunflower oil (HOSO), or oil-products modified to their phenolic content, i.e. phenolics deprived-EVOO [EVOO(?)], SO enriched with the EVOO phenolics [SO(+)], HOSO enriched with the EVOO phenolics [HOSO(+)]. HCD induced dyslipidemia and resulted in higher aorta adhesion molecules levels at euthanasia. Groups receiving EVOO, EVOO(?), HOSO, HOSO(+) presented higher serum TC and LDL-c levels compared to cholesterol-fed rats; attenuation of aorta E-selectin levels was also observed. In EVOO/EVOO(?) groups, aorta vascular endothelial adhesion molecule-1 (VCAM-1) was lower compared to HCD animals. SO/SO(+) diets had no effect on endothelial dysfunction amelioration. Overall, our results suggest that major and/or minor EVOO constituents improve aorta E-selectin and VCAM-1, while serum lipids do not benefit.     

Effect of virgin olive oil and thyme phenolic compounds on blood lipid profile: implications of human gut microbiota

Purpose

To investigate the effect of virgin olive oil phenolic compounds (PC) alone or in combination with thyme PC on blood lipid profile from hypercholesterolemic humans, and whether the changes generated are related with changes in gut microbiota populations and activities.

Methods

A randomized, controlled, double-blind, crossover human trial (n = 12) was carried out. Participants ingested 25 mL/day for 3 weeks, preceded by 2-week washout periods, three raw virgin olive oils differing in the concentration and origin of PC: (1) a virgin olive oil (OO) naturally containing 80 mg PC/kg, (VOO), (2) a PC-enriched virgin olive oil containing 500 mg PC/kg, from OO (FVOO), and (3) a PC-enriched virgin olive oil containing a mixture of 500 mg PC/kg from OO and thyme, 1:1 (FVOOT). Blood lipid values and faecal quantitative changes in microbial populations, short chain fatty acids, cholesterol microbial metabolites, bile acids, and phenolic metabolites were analysed.

Results

FVOOT decreased seric ox-LDL concentrations compared with pre-FVOOT, and increased numbers of bifidobacteria and the levels of the phenolic metabolite protocatechuic acid compared to VOO (P < 0.05). FVOO did not lead to changes in blood lipid profile nor quantitative changes in the microbial populations analysed, but increased the coprostanone compared to FVOOT (P < 0.05), and the levels of the faecal hydroxytyrosol and dihydroxyphenylacetic acids, compared with pre-intervention values and to VOO, respectively (P < 0.05).

Conclusion

The ingestion of a PC-enriched virgin olive oil, containing a mixture of olive oil and thyme PC for 3 weeks, decreases blood ox-LDL in hypercholesterolemic humans. This cardio-protective effect could be mediated by the increases in populations of bifidobacteria together with increases in PC microbial metabolites with antioxidant activities.