Phenolic compounds in olive oil: antioxidant, health and organoleptic activities according to their chemical structure.

Hydrophilic phenols are the most abundant natural antioxidants of virgin olive oil (VOO), in which, however, tocopherols and carotenes are also present. The prevalent classes of hydrophilic phenols found in VOO are phenolic alcohols and acids, flavonoids, lignans and secoiridoids. Among these substances the last two classes include the most concentrate phenols of VOO. Secoiridoids, like aglycone derivatives of oleuropein, demethyloleuropein and ligstroside, are present in olive fruit as most abundant VOO phenolic antioxidants. Several important biological properties (antioxidant, anti-inflammatory, chemopreventive and anti-cancer) and the characteristic pungent and bitter tasty properties have been attributed to VOO phenols. Relationships between polyphenols activities and their chemical structures are discussed in this paper.

Low density lipoprotein oxidation is inhibited in vitro by olive oil constituents.

Oxidation of low density lipoproteins maybe a factor in the development of atherosclerosis. The Mediterranean diet rich in vegetables, grains, legumes, fruits, and oils, mainly olive oil, has been suggested to reduce the incidence of coronary heart disease, because of its low saturated and high monounsaturated fatty acids content. It is also possible that the natural antioxidants in the oil help to prevent lipid oxidation, e.g. that of low density lipoproteins, thus retarding the formation of atherosclerotic plaques. First-pressed, extra-virgin olive oil contains appreciable amounts of polyphenolic compounds that prevent its autoxidation and are responsible for its high stability. We tested these compounds on low density lipoprotein oxidation and found an inhibitory effect, at low concentrations, on various indexes of lipid oxidation (vitamin E content, formation of thiobarbituric acid-reacting substances, lipid peroxides, levels of polyunsaturated fatty acids, protein modification, conjugated diene formation). Our data suggest that natural antioxidants could play a role in inhibiting the formation of cytotoxic products such as lipid peroxides thus retarding the onset of the atherosclerotic damage.

Cancer chemoprevention by hydroxytyrosol isolated from virgin olive oil through G1 cell cycle arrest and apoptosis.

Recent epidemiological evidence and animal studies suggest a relationship between the intake of olive oil and a reduced risk of several malignancies. The present study assesses the effect of hydroxytyrosol, a major antioxidant compound of virgin olive oil, on proliferation, apoptosis and cell cycle of tumour cells. Hydroxytyrosol inhibited proliferation of both human promyelocytic leukaemia cells HL60 and colon adenocarcinoma cells HT29 and HT29 clone 19A. The con-centrations of hydroxytyrosol which inhibited 50% of cell proliferation were approximately 50 and approximately 750 micromol/l for HL60 and both HT29 and HT29 clone 19A cells, respectively. At concentrations ranging from 50 to 100 micromol/l, hydroxytyrosol induced an appreciable apoptosis in HL60 cells after 24 h of incubation as evidenced by flow cytometry, fluorescence microscopy and internucleosomal DNA fragmentation. Interestingly, no effect on apoptosis was observed after similar treatment of freshly isolated human lymphocytes and polymorphonuclear cells. The DNA cell cycle analysis, quantified by flow cytometry, showed that the treatment of HL60 cells with hydroxytyrosol 50-100 micromol/l arrested the cells in the G0/G1 phase with a concomitant decrease in the cell percentage in the S and G2/M phases. These results support the hypothesis that hydroxytyrosol may exert a protective activity against cancer by arresting the cell cycle and inducing apoptosis in tumour cells, and suggest that hydroxytyrosol, an important component of virgin olive oil, may be responsible for its anticancer activity.

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.

Olive oil hydroxytyrosol protects human erythrocytes against oxidative damages.

Hydroxytyrosol, the major representative phenolic compound of virgin olive oil, is a dietary component. Its possible protective effect on hydrogen peroxide (H(2)O(2))-induced oxidative alterations was investigated in human erythrocytes. Cells were pretreated with micromolar hydroxytyrosol concentrations and then exposed to H(2)O(2) over different time intervals. Subsequently, erythrocytes were analyzed for oxidative hemolysis and lipid peroxidation. Our data demonstrate that hydroxytyrosol prevents both oxidative alterations, therefore, providing protection against peroxide-induced cytotoxicity in erythrocytes. The effect of oxidative stress on erythrocyte membrane transport systems, as well as the protective role of hydroxytyrosol, also were investigated in conditions of nonhemolytic mild H(2)O(2) treatment. Under these experimental conditions, a marked decrease in the energy-dependent methionine and leucine transport is observable; this alteration is quantitatively prevented by hydroxytyrosol pretreatment. On the other hand, the energy-independent glucose transport is not affected by the oxidative treatment. The reported data give new experimental support to the hypothesis of a protective role played by nonvitamin antioxidant components of virgin olive oil on oxidative stress in human systems.

Phenolic compounds of olive fruit: one- and two-dimensional nuclear magnetic resonance characterization of Nüzhenide and its distribution in the constitutive parts of fruit.

The phenolic composition of peel, pulp, and seed of the olive fruit was studied for several Italian cultivars used for oil extraction. The seed contained a compound never previously detected in peel and in pulp. The spectroscopic characterization of this compound proved, for the first time, the presence of nüzhenide in the olive seed. Study of the phenolic composition showed that oleuropein, demethyloleuropein, and verbascoside were present in all of the constitutive parts of the fruit; by contrast, nüzhenide was exclusively present in the seeds of all the cultivars at all ripening stages studied.

Effect of enzyme treatment during mechanical extraction of olive oil on phenolic compounds and polysaccharides.

The effect of the use of cell-wall-degrading-enzyme preparations during the mechanical extraction process of virgin olive oil on the phenolic compounds and polysaccharides was investigated. The use of the enzyme preparations increased the concentration of phenolic compounds in the paste, oil, and byproducts. Especially, the contents of secoiridiod derivatives such as the dialdehydic form of elenolic acid linked to 3,4-dihydroxyphenylethanol (3,4-DHPEA-EDA) and an isomer of oleuropein aglycon (3,4-DHPEA-EA), which have high antioxidant activities, increased significantly in the olive oil. Furthermore, the use of an N(2) flush during processing strongly increased the phenolic concentration. Analyses of the pectic polymers present in the paste showed that the use of pectinolytic enzyme preparations increased the yield of the buffer soluble pectins and the proportion of molecules with a lower molecular mass. Also, the content of uronic acids in the buffer soluble extract increased considerably due to the use of the enzyme preparations. Analysis of the polymeric carbohydrates in the vegetation waters showed the presence of mainly pectic polymers. The addition of commercial enzyme preparations increased the uronic acid content of the polysaccharides in the vegetation water substantially compared to the blank. This study showed that the addition of cell-wall-degrading enzymes did improve the olive oil quality; however, mechanisms remained unclear.

[Use of enzyme preparations in wine production (author's transl)]. / Impiego di preparazioni enzimatiche in enologia

The Author after having examined the present acquirements of the native enzymes of the grapes, summarizes the enologic uses of the enzyme preparations at various degrees of purity with the point of view of the influence on the organoleptic (color, aromatic composition) ad rheologic (yield, filtrability) characteristics of the musts and wines besides some microbiological implications. Subsequently the Author exposes the original results extrapolated from the pilot and industrial trials on the use of different hydrolases (pectinase, cellulase, hemicellulase, acid protease, xylanase) on the wine-making processes (traditional red wine-making, heating red-wine-making, white wine-making). From the comparison of the last data with those of the reference are drawed conclusive considerations on some aspects of the subject.

[Improvement of the concentration method of the "head space" above wine for direct gas chromatographic analysis by means of two absorbent polymers (author's transl)]. / Impiego di polimeri per la concentrazione di costituenti volatili dello "spazio di testa" dei vini e loro diretta analisi gas-cromatografica

It has been defined, in a previous work, a procedure for the "head space" gas chromatographic analysis. This method allowed the separation of 17 volatile constituents, utilizing Porapak Q, either as trap or chromatographic adsorbent. A series of new experiences have improved this precedure, adopting as trap two polymers (Porapak Q, copolymer of the ethyl-vinyl-benzene divinyl-benzene; Tenax GC porous polymer 2,6-diphenyl-p-phenilene oxide) and two different chromatographic phases. Furthermore, it has been entirely modified the introduction of the sample into the gas chromatographic column simplifying the handling and improving the operative conditions (times and temperature of desorption). The analysis of the "head space" carried out on wines of different aromatic compositions (Riesling) and on wines at different degree of ageing (Rubesco), besides having allowed the separation of 61 volatile components, 27 of which have identified, has put in evidence the sensitivity of this procedure.

[Differentiation of natural red wines from white wines blended with oenocyanine (author's transl)]. / Differenziazione dei vini rossi naturali da quelli ottenuti per addizione di enocianina ai vini bianchi

A method is proposed for the differentiation of natural red wines from those obtained by addition of oenocyanine to white wines. The procedure is based on the determination of tannin phenolics and nontannin phenolics by selective precipitation with methyl cellulose and subsequent estimation of the intensity of absorption at 450 nm and 520 nm. The sum of ratio: mg/1 non tannin phenolics/absorption at 450 nm X 1000 and mg/1 tannin phenolics/absorption at 520 nm X 1000, furnishes values which are in correlation with the origin of two wines and such as to consent their differentiation.

The effects of treatment with enzymatic preparations and tannin phenolic absorbent agents in extracting the olive oil by single pressure process on the oil yield, on the analytical characteristics of the oils of the vegetation waters and of the waste waters.

The vegetation waters of the must, the oils and the waste waters extracted from olive pastes, treated by enzymatic preparations (Cellulase, Hemicellulase, Polygalacturonase and Protease) and tannin phenolic adsorbent agents (Polyclar AT, Methylcellulose, Albumine) employed during crushing of olive were analysed:--the vegetation waters in order to justify some technological results (oil yields and extraction speed) obtained by the treatments;--the oils in order to examine the effects of the treatments on the same chemical characteristics and the stability to rancidity. --The waste waters to verify the possible influence of the treatments on the BOD. From the results relative to the vegetation waters, it has been suggested that the increase of the "detached oil" does occur by two different biochemical mechanisms which involve the constitutive lipoprotein of the oil drop membrane and colloidal constituents of the liquid and solid phase of the pastes. For what concerns the oils, the treatments induce the slight modification of the fatty acid composition and chromatic characteristics, a higher stability to rancidity, a qualitative and quantitative increase of the "headspace" violates constituents above oils. The waste waters obtained from the olive pastes show lower BOD5 values.