The fate of olive oil polyphenols in the gastrointestinal tract: implications of gastric and colonic microflora-dependent biotransformation

We have conducted a detailed investigation into the absorption, metabolism and microflora-dependent transformation of hydroxytyrosol ( HT), tyrosol (TYR) and their conjugated forms, such as oleuropein (OL). Conjugated forms underwent rapid hydrolysis under gastric conditions, resulting in significant increases in the amount of free HT and TYR entering the small intestine. Both HT and TYR transferred across human Caco-2 cell monolayers and rat segments of jejunum and ileum and were subject to classic phase I/II biotransformation. The major metabolites identified were an O-methylated derivative of HT, glucuronides of HT and TYR and a novel glutathionylated conjugate of HT. In contrast, there was no absorption of OL in either model. However, OL was rapidly degraded by the colonic microflora resulting in the formation of HT. Our study provides additional information regarding the breakdown of complex olive oil polyphenols in the GI tract, in particular the stomach and the large intestine.

Extra virgin olive oil phenolics: absorption, metabolism, and biological activities in the GI tract

Olive oil, a typical ingredient of the Mediterranean diet, possesses many beneficial health effects. The biological activities ascribed to olive oil consumption are associated in part to its phenolics constituents, and mainly linked to the direct or indirect antioxidant activity of olive oil phenolics and their metabolites, which are exerted more efficiently in the gastrointestinal (GI) tract, where dietary phenolics are more concentrated when compared to other organs. In this regard, we present a brief overview of the metabolism, biological activities, and anticancer properties of olive oil phenolics in the GI tract. Toxicology and Industrial Health 2009; 25: 285-293.

Inhibition of p38/CREB phosphorylation and COX-2 expression by olive oil polyphenols underlies their anti-proliferative effects

We investigated the anti-proliferative effects of an olive oil polyphenolic extract on human colon adenocarcinoma cells. Analysis indicated that the extract contained hydroxytyrosol, tyrosol and the various secoiridoid derivatives, including oleuropein. This extract exerted a strong inhibitory effect on cancer cell proliferation, which was linked to the induction of a G2/M phase cell cycle block. Following treatment with the extract (50 mu g/ml) the number of cells in the G2/M phase increased to 51.82 +/- 2.69% relative to control cells (15.1 +/- 2.5%). This G2/M block was mediated by the ability of olive oil polyphenols (50 mu g/ml) to exert rapid inhibition of p38 (38.7 +/- 4.7%) and CREB (28.6 +/- 5.5%) phosphorylation which led to a downstream reduction in COX-2 expression (56.9 +/- 9.3%). Our data suggest that olive oil polyphenols may exert chemo preventative effects in the large intestine by interacting with signalling pathways responsible for colorectal cancer development. (c) 2007 Elsevier Inc. All rights reserved.

Evaluation by volatile profile of the synergistic antioxidant effect between bovine serum albumin and virgin olive oil phenolic compounds in an oil-in-water emulsion

THE OXIDATIVE STABILITY OF OIL-IN-WATER EMULSIONS, CONTAINING BOVINE SERUM ALBUMIN (BSA) AND VIRGIN OLIVE OIL PHENOLIC COMPOUNDS, WAS STUDIED BY THE DETERMINATION OF THE FORMATION OF VOLATILE OXIDATION PRODUCTS. FOUR OIL-IN-WATER EMULSIONS WITH AND WITHOUT PHENOLS ISOLATED FROM VIRGIN OLIVE OIL AND BSA WERE PREPARED. THESE MODEL SYSTEMS WERE STORED AT 60 degrees C TO ACCELERATE LIPID OXIDATION. VOLATILE OXIDATION PRODUCTS WERE MONITORED EVERY THREE DAYS BY HEADSPACE SOLID-PHASE MICROEXTRACTION COUPLED WITH GAS CHROMATOGRAPHY. ALTHOUGH INDIVIDUALLY OLIVE OIL PHENOLIC COMPOUNDS AND BSA SHOWED A SIGNIFICANT ANTIOXIDANT ACTIVITY, THE COMBINATION OF THESE COMPONENTS SHOWED A VERY GOOD SYNERGY, QUANTIFIED AS 127%. IN FACT, THE EMULSION CONTAINING BOTH PHENOLIC COMPOUNDS AND BSA SHOWED A VERY LOW LEVEL OF OXIDATIVE DETERIORATION AFTER 45 DAYS STORAGE.

Bovine serum albumin produces a synergistic increase in the antioxidant activity of virgin olive oil phenolic compounds in oil-in-water emulsions

Virgin olive oil is valued for its flavor, but unacceptable off-flavors may develop on storage in food products containing this oil due to oxidation. The oxidative stability of oil-in-water emulsions containing bovine serum albumin (BSA) and virgin olive oil phenolic compounds was studied. Four oil-in-water emulsions with and without BSA and phenols isolated from virgin olive oil were prepared. These model systems were stored at 60 degrees C to speed up lipid oxidation. Primary and secondary oxidation products were monitored every three days. Peroxide values and conjugated diene contents were determined as measures of the primary oxidation products. p-Anisidine values and volatile compounds were determined as measures of the secondary oxidation products. This latter determination was carried out by headspace solid-phase microextraction coupled with gas chromatography. Although olive oil phenolic compounds and BSA contributed some antioxidant activity when present as individual additives, the combination of BSA with phenols in an emulsion showed 58-127% synergy, depending on which analytical method was used in the calculation. The emulsion containing phenolic compounds and BSA showed a low level of deterioration after 45 days of storage at 60 degrees C.

Influence of harvest date and crop yield on the fatty acid composition of virgin olive oils from cv. Picual

In this study was analyzed the effect of crop year and harvesting time on the fatty acid composition of cv. Picual virgin olive oil. The study was carried out during the fruit ripening period for three crop seasons. The mean fatty acid composition of Picual oils was determined. The oils contained palmitic acid (11.9%), oleic acid (79.3%), and linoleic acid (2.95%). The content of palmitic acid and saturated fatty acids decreased during fruit ripening while oleic and linoleic acids increased. The amount of stearic and linolenic acids decreased. The amount of saturated acids, palmitic and stearic, and the polyunsaturated acids linoleic and linolenic was dependent on the time of harvest, whereas the amount of oleic acid varied with the crop year. The differences observed between crop years for both palmitic and linoleic acid may be explained by the differences in the temperature during oil biosynthesis and by the amount of summer rainfall for oleic acid content. A significant relationship was observed between the MUFA/PUFA ratio and the oxidative stability measured by the Rancimat method.

Seasonal changes in olive fruit characteristics and oil accumulation during ripening process

Olive fruits of three of the most important Spanish and Italian cultivars, 'Picual', `Hojiblanca' and 'Frantoio', were harvested at bi-weekly periods during three crop seasons to study their development and ripening process. Fresh and dry weights and ripening index were determined for fruit, while dry matter, oil and moisture contents were determined in both fruit and pulp (flesh). Fruit growth rate and oil accumulation were calculated. Each olive cultivar showed a different ripening pattern, 'Hojiblanca' being the last one to maturate. Fruit weight increased, decreasing its growth rate from the middle of November. Dry matter and moisture contents decreased during ripening in pulp and fruit, 'Hojiblanca' showing the highest values for both. Oil content, when expressed on a fresh weight basis, increased in all cultivars, although for the last time period showed variations due to climatic conditions. During ripening, oil content on a dry weight basis increased in fruit, but oil biosynthesis in flesh ceased from November. Olive fruits presented lower oil and higher dry matter contents in the year of lowest rainfall. Therefore fruit harvesting should be carried out from the middle of November in order to obtain the highest oil yield and avoid natural fruit drop. (C) 2004 Society of Chemical Industry.

Influence of fruit ripening process on the natural antioxidant content of Hojiblanca virgin olive oils

The effect of fruit ripeness on the antioxidant content of 'Hojiblanca' virgin olive oils was studied. Seasonal changes were monitored at bi-weekly intervals for three consecutive crop years. Phenolic content, tocopherol composition, bitterness index, carotenoid and chlorophyllic pigments and oxidative stability were analysed. In general, the antioxidants and the related parameters decreased as olive fruit ripened. The phenolics and bitterness, closely related parameters, did not present significant differences among years. Although in general, the tocopherols decreased during olive ripening gamma-tocopherol increased. Differences between crop years were found only for total tocopherols and alpha-tocopherol, which showed higher content in low rainfall year oils. The pigment content decreased during ripening, chlorophyll changing faster. For low rainfall years, the level of pigments was higher, reaching significant differences between yields. Significant differences among years were found for oil oxidative stability; higher values were obtained for drought years. A highly significant prediction model for oxidative stability has been obtained. (C) 2004 Elsevier Ltd. All rights reserved.

Characterisation of virgin olive oil of Italian olive cultivars: 'Frantoio' and 'Leccino', grown in Andalusia

Work was carried out on the characterisation of virgin olive oils from the main Italian cultivars, 'Frantoio' and 'Leccino', grown in two different locations in Andalusia: Mengibar (Jaen) and Cabra (Cordoba), with important differences in altitude. The study was carried out during the crop years 1999/2000 and 2001/2002. There were significant differences between the oils from both cultivars when grown in the different environments, Cabra close to the hills and Mengibar in the open at 280 m height. At higher altitude, the oils showed a greater content of oleic acid and higher stability, while in the open the oils had higher tocopherol and linoleic acid contents. For the phenolic compounds, the environment influenced each cultivar in different ways. Sensorial characteristics, showed significant differences between the oils from each cultivar and location. In general, the oils from Andalusia had higher levels of natural antioxidants, greater oxidative stability and more marked sensorial characters. (C) 2004 Elsevier Ltd. All rights reserved.

Olive oil increases the number of triacylglycerol-rich chylomicron particles compared with other oils: an effect retained when a second standard meal is fed

Background: Compared with the postprandial events after a single meal, different events occur when a second meal is ingested 4–6 h after a first meal. There is a rapid appearance of chylomicrons in the circulation carrying fat ingested with the first meal, with a peak 1 h after the second meal. Objective: Our goal was to examine whether different dietary oils have effects on the storage of triacylglycerol as a result of differences in their digestion, absorption, and incorporation into chylomicrons. Design: A single-blind, randomized, within-subject crossover design was used to study the effects of palm oil, safflower oil, a mixture of fish and safflower oil, and olive oil on postprandial apolipoprotein (apo) B-48, retinyl ester, and triacylglycerol in the Sf > 400 fraction with the use of a sequential meal protocol. Results: For triacylglycerol, retinyl ester, and apo B-48, the time to reach peak concentration was significantly earlier after the second meal than after the first meal (P < 0.005). This was apparent with each of the dietary oils. The pattern of the apo B-48 response differed significantly among the dietary oils, with olive oil resulting in higher concentrations after both meals (P = 0.003). The ratio of triacylglycerol to apo B-48 was significantly lower after olive oil feeding than after feeding with the other oils (P = 0.02). Conclusions: The rapid entry of chylomicrons after the ingestion of a second meal 5 h after a first meal was seen with all of the oils investigated. The short-term ingestion of olive oil produced more chylomicrons than did the other dietary oils, which may have been due to differences in the metabolic handling of olive oil within the gut.

Effect of long-term olive oil dietary intervention on postprandial triacylglycerol and factor VII metabolism

Although the beneficial effects of Mediterranean-type diets, which are rich in olive oil, a good source of monounsaturated fatty acids (MUFAs), are generally accepted, little is known about the effects of long-term dietary MUFA intake on postprandial lipoprotein metabolism and hemostasis. This study used a single-blind, randomized, crossover design to investigate the relative effects of a long-term dietary olive oil intervention and a control [saturated fatty acid (SFA)-enriched] diet on postprandial triacylglycerol metabolism and factor VII activity. The postprandial response to a standard test meal was investigated in 23 healthy men who adhered to both diets for 8 wk. cis-MUFAs were successfully substituted for SFAs in the MUFA diet without affecting total dietary fat or energy intakes. The long-term dietary MUFA intervention significantly reduced plasma and LDL-cholesterol concentrations (P = 0.01). Postprandial triacylglycerol concentrations were significantly greater in the early postprandial period after the MUFA diet (P = 0.003). Postprandial factor VII activation and the concentration of the factor VII antigen were significantly lower after the MUFA diet (P = 0.04 and P = 0 006, respectively). This study showed that isoenergetic substitution of MUFAs for SFAs reduces plasma cholesterol and reduces the degree of postprandial factor VII activation. The alterations in the postprandial triacylglycerol response suggest a greater rate of dietary fat absorption and postprandial triacylglycerol metabolism after a diet rich in MUFAs. This study presents new insights into the biochemical basis of the beneficial effects associated with long-term dietary MUFA consumption, which may explain the lower rates of coronary mortality in Mediterranean regions.

Effect of olive oil on immune function in middle-aged men

Consumption of diets rich in monounsaturated fatty acids (MUFAs) has been linked with a low prevalence of atherosclerosis and there has been great interest in the effects of MUFAs on lipoprotein metabolism. Less attention has been paid to the effects of MUFAs on the immune system, yet cells of the immune system are an inherent part of the inflammatory events involved in atherosclerosis and several animal studies showed that olive oil has some potent immunomodulatory actions. We therefore considered it important to investigate the effects of chronic consumption of MUFAs on several immune cell functions in healthy humans. Healthy middle-aged males entered a doubleblind, randomized, controlled trial in which they consumed either a MUFA diet or a control diet for 2 mo. There was a significant decrease in the expression of intercellular adhesion molecule 1 by peripheral blood mononuclear cells from subjects consuming the MUFA diet. Consumption of the MUFA diet did not affect natural killer cell activity or proliferation of mitogen-stimulated leukocytes. The effects of a MUFA-rich diet on adhesion molecule expression may have implications for the influence of dietary fat on inflammatory diseases, including atherosclerosis.