: Edible oil is oxidized during processing and storage via autoxidation and photosensitized oxidation, in which triplet oxygen (3O2) and singlet oxygen (1O2) react with the oil, respectively. Autoxidation of oils requires radical forms of acylglycerols, whereas photosensitized oxidation does not require lipid radicals since 1O2 reacts directly with double bonds. Lipid hydroperoxides formed by 3O2 are conjugated dienes, whereas 1O2 produces both conjugated and nonconjugated dienes. The hydroperoxides are decomposed to produce off-flavor compounds and the oil quality decreases. Autoxidation of oil is accelerated by the presence of free fatty acids, mono- and diacylglycerols, metals such as iron, and thermally oxidized compounds. Chlorophylls and phenolic compounds decrease the autoxidation of oil in the dark, and carotenoids, tocopherols, and phospholipids demonstrate both antioxidant and prooxidant activity depending on the oil system. In photosensitized oxidation chlorophyll acts as a photosensitizer for the formation of 1O2; however, carotenoids and tocopherols decrease the oxidation through 1O2 quenching. Temperature, light, oxygen concentration, oil processing, and fatty acid composition also affect the oxidative stability of edible oil.

Mechanisms and Factors for Edible Oil Oxidation

Phenolics in Food and Nutraceuticals is the first single-source compendium of essential information concerning food phenolics. This unique book reports the classification and nomenclature of phenolics, their occurrence in food and nutraceuticals, chemistry and applications, and nutritional and health effects. In addition, it describes antioxidant activity of phenolics in food and nutraceuticals as well as methods for analysis and quantification. Each chapter concludes with an extensive bibliography for further reading. Food scientists, nutritionists, chemists, biochemists, and health professionals will find this book valuable.

Phenolics in food and nutraceuticals

Dietary polyphenols represent a wide variety of compounds that occur in fruits, vegetables, wine, tea, extra virgin olive oil, chocolate and other cocoa products. They are mostly derivatives and/or isomers of flavones, isoflavones, flavonols, catechins and phenolic acids, and possess diverse biological properties such as antioxidant, antiapoptosis, anti-aging, anticarcinogen, anti-inflammation, anti-atherosclerosis, cardiovascular protection, improvement of the endothelial function, as well as inhibition of angiogenesis and cell proliferation activity. Most of these biological actions have been attributed to their intrinsic reducing capabilities. They may also offer indirect protection by activating endogenous defense systems and by modulating cellular signaling processes such as nuclear factor-kappa B (NF-κB) activation, activator protein-1(AP-1) DNA binding, glutathione biosynthesis, phosphoinositide 3 (PI3)-kinase/protein kinase B (Akt) pathway, mitogen-activated protein kinase (MAPK) proteins [extracellular signal-regulated protein kinase (ERK), c-jun N-terminal kinase (JNK) and P38 ] activation, and the translocation into the nucleus of nuclear factor erythroid 2 related factor 2 (Nrf2). This paper covers the most recent literature on the subject, and describes the biological mechanisms of action and protective effects of dietary polyphenols.

/pdf/dietary-polyphenols-and-their-biological-significance-216gryq5fb.pdf

Dietary Polyphenols and Their Biological Significance

Phenolic compounds are well-known phytochemicals found in all plants. They consist of simple phenols, benzoic and cinnamic acid, coumarins, tannins, lignins, lignans and flavonoids. Substantial developments in research focused on the extraction, identification and quantification of phenolic compounds as medicinal and/or dietary molecules have occurred over the last 25 years. Organic solvent extraction is the main method used to extract phenolics. Chemical procedures are used to detect the presence of total phenolics, while spectrophotometric and chromatographic techniques are utilized to identify and quantify individual phenolic compounds. This review addresses the application of different methodologies utilized in the analysis of phenolic compounds in plant-based products, including recent technical developments in the quantification of phenolics.

/pdf/techniques-for-analysis-of-plant-phenolic-compounds-3co9l3slyg.pdf

Techniques for analysis of plant phenolic compounds.

A status review on the medicinal properties of essential oils

Volatile compounds in virgin olive oil: occurrence and their relationship with the quality

Hydrophilic phenols are the most abundant natural antioxidants of virgin olive oil (VOO), in which, however, tocopherols and carotens are also present. The prevalent classes of hydrophilic phenols found in VOO are phenolic alcohols, phenolic acids, flavonoids, lignans and secoiridoids. Secoiridoids including aglycon derivatives of oleuropein, demethyloleuropein and ligstroside, that are present in olive fruit, are the most abundant phenolic antioxidants of VOO. In this paper, the phenolic composition of VOO as well as the agronomic and technological parameters that affect their concentration in the oil are discussed. The olive cultivar and the ripening stage of fruit, in fact, have always been the most studied agronomic aspects that affect phenolic concentration in VOO. However, the malaxation conditions and the extraction systems used to separate oil from olive pastes (i.e. pressure three-phases and two-phases centrifugation systems) are also of great importance.

Contribution of phenolic compounds to virgin olive oil quality

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.

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

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.

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

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 nuzhenide 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, nuzhenide was exclusively present in the seeds of all the cultivars at all ripening stages studied.

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

GianFrancesco Montedoro

Papers

Volatile compounds in virgin olive oil: occurrence and their relationship with the quality

Contribution of phenolic compounds to virgin olive oil quality

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

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

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