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J Kowalczyk - One of the best experts on this subject based on the ideXlab platform.
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alkaline saponification results in decomposition of Tocopherols in milk and ovine blood plasma
Journal of Chromatography B, 2007Co-Authors: M Czauderna, J KowalczykAbstract:Alkaline saponification of entire sample matrixes for quantification of α-, γ-, δ-Tocopherols (α-T, γ-T, δ-T) and α-tocopherol acetate (α-TAc) was examined. High-performance liquid chromatography was used to measure α-T, γ-T, δ-T and α-TAc in tocopherol standard solutions, milk and ovine blood plasma. Saponification in the presence of vitamin C decreases the concentration of Tocopherols, especially α-T and γ-T. The poor recovery of Tocopherols is due to the decomposition of Tocopherols in saponified standard solutions, milk or plasma. Saponification of samples in the presence of 2,[6]-ditertbutyl-p-cresol or flushed only with a stream of Ar resulted in a major decrease in the concentrations of α-T, γ-T, δ-T and α-TAc in comparison with saponification in the presence of vitamin C.
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Alkaline saponification results in decomposition of Tocopherols in milk and ovine blood plasma.
Journal of chromatography. B Analytical technologies in the biomedical and life sciences, 2007Co-Authors: M Czauderna, J KowalczykAbstract:Alkaline saponification of entire sample matrixes for quantification of alpha-, gamma-, delta-Tocopherols (alpha-T, gamma-T, delta-T) and alpha-tocopherol acetate (alpha-TAc) was examined. High-performance liquid chromatography was used to measure alpha-T, gamma-T, delta-T and alpha-TAc in tocopherol standard solutions, milk and ovine blood plasma. Saponification in the presence of vitamin C decreases the concentration of Tocopherols, especially alpha-T and gamma-T. The poor recovery of Tocopherols is due to the decomposition of Tocopherols in saponified standard solutions, milk or plasma. Saponification of samples in the presence of 2,[6]-ditertbutyl-p-cresol or flushed only with a stream of Ar resulted in a major decrease in the concentrations of alpha-T, gamma-T, delta-T and alpha-TAc in comparison with saponification in the presence of vitamin C.
Afaf Kamaleldin - One of the best experts on this subject based on the ideXlab platform.
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comparison of reversed phase liquid chromatography mass spectrometry with electrospray and atmospheric pressure chemical ionization for analysis of dietary Tocopherols
Journal of Chromatography A, 2007Co-Authors: Svetlana A Lanina, Afaf Kamaleldin, Patricia Toledo, Sabine Sampels, Jelena JastrebovaAbstract:Abstract ESI and APCI ionization techniques in both negative and positive ion modes were evaluated for simultaneous LC–MS analysis of the four tocopherol homologues (α, β, γ and δ). The ESI and APCI ionization of Tocopherols in positive ion mode was not efficient and proceeded via two competitive mechanisms, with the formation of protonated pseudo-molecular ions and molecular ions, which adversely influenced the repeatability of MS signal. Ionization in negative ion mode in both ESI and APCI was more efficient as it only produced target deprotonated pseudo-molecular ions. The APCI in negative ion mode showed larger linearity range, lower detection limits and was less sensitive to the differences in chemical structure of analytes and nature of applied solvents than negative ion ESI. Negative ion APCI was, therefore, chosen for the development of LC–MS method for simultaneous determination of the four Tocopherols in foods. A baseline separation of the Tocopherols was achieved on novel pentafluorophenyl silica-based column Fluophase PFP. The use of methanol–water (95:5, v/v) as a mobile phase was preferable to the use of acetonitrile–water due to considerable gain in MS signal. The limits of quantifications were 9 ng/mL for α-tocopherol, 8 ng/mL for β- and γ- and 7.5 ng/mL for δ-tocopherol when 2 μL was injected. This method was successfully applied to determination of Tocopherols in sunflower oil and milk.
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effect of fatty acids and Tocopherols on the oxidative stability of vegetable oils
European Journal of Lipid Science and Technology, 2006Co-Authors: Afaf KamaleldinAbstract:The oxidative stability of vegetable oils is determined by their fatty acid composition and antioxidants, mainly Tocopherols but also other non-saponifiable constituents. The effect of fatty acids on stability depends mainly on their degree of unsaturation and, to a lesser degree, on the position of the unsaturated functions within the triacylglycerol molecule. Vegetable oils contain Tocopherols and tocotrienols, especially α- and γ-Tocopherols, as their main antioxidants. The antioxidant behavior of Tocopherols represents a complex phenomenon as they are efficient antioxidants at low concentrations but they gradually lose efficacy as their concentrations in the vegetable oils increase. The “loss of efficacy” of Tocopherols, sometimes referred to as a “pro-oxidant effect”, is witnessed by an increase in the rate of oxidation during the induction period, despite elongation of this phase. The phenomenon is much obvious for α-tocopherol, but is also evident for other Tocopherols. In agreement with nature's wisdom, the tocopherol levels in vegetable oils seem to be close to the optimal levels needed for the stabilization of these oils. The presence of other antioxidants in the oils, e.g. carotenoids, phenolic compounds, and Maillard reaction products, may synergize with Tocopherols and minimize this loss of efficacy.
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antioxidant activities of α and γ Tocopherols in the oxidation of rapeseed oil triacylglycerols
Journal of the American Oil Chemists' Society, 1999Co-Authors: Annamaija Lampi, Leena Kataja, Afaf Kamaleldin, Piironen VienoAbstract:Antioxidant properties of 5 to 500 µg/g levels of α-and γ-Tocopherols, in the oxidation of rapeseed oil triacylglycerols (RO TAG), were studied at 40°C in the dark. Each tocopherol alone and in a mixture was studied for its stability in oxidizing RO TAG. Also the effects of Tocopherols on the formation of primary and secondary oxidation products of RO TAG were investigated. Both Tocopherols significantly retarded the oxidation of RO TAG. At low levels (≤50 µg/g), α-tocopherol was more stable and was a more effective antioxidant than γ-tocopherol. At higher α-tocopherol levels (>100 µg/g), there was a relative increase in hydroperoxide formation parallel to consumption of α-tocopherol, which was not found with γ-tocopherol. Therefore, γ-tocopherol was a more effective antioxidant than α-tocopherol at levels above 100 µg/g. As long as there were Tocopherols present, the hydroperoxides were quite stable and no volatile aldehydes were formed. In a mixture, α-tocopherol protected γ-tocopherol from being oxidized at the addition levels of 5+5 and 10+10 µg/g but no synergism between the Tocopherols was found. α-Tocopherol was less stable in the 500+500 µg/g mixture than when added alone to the RO TAG. No prooxidant activity of either tocopherol or their mixture was found.
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effects of α and γ Tocopherols on the autooxidation of purified sunflower triacylglycerols
Lipids, 1998Co-Authors: M D Fuster, Annamaija Lampi, Anu Hopia, Afaf KamaleldinAbstract:The antioxidant effects of α- and γ-Tocopherols were evaluated in a model system based on the autooxidation of purified sunflower oil (p-SFO) triacylglycerols at 55°C for 7 d. Both Tocopherols were found to cause more than 90% reduction in peroxide value when present at concentrations >20 ppm. α-Tocopherol was a better antioxidant than γ-tocopherol at concentrations ≤40 ppm but a worse antioxidant at concentrations >200 ppm. Neither α- nor γ-tocopherol showed a prooxidant effect at concentrations as high as 2000 ppm. The amount of Tocopherols consumed during the course of oxidation was positively correlated to the initial concentration of Tocopherols, and the correlation was stronger for α- than for γ-tocopherol. This correlation suggested that, besides reactions with peroxyl radicals, destruction of Tocopherols may be attributed to unknown side reactions. Addition of FeSO4, as a prooxidant, caused a 12% increase in the peroxide value of p-SFO in the absence of Tocopherols. When Tocopherols were added together with FeSO4, some increase in peroxide value was observed for samples containing 200, 600 or 1000 ppm of α- but not γ-tocopherol. The addition of FeSO4, however, caused an increase in the amount of α- and γ-Tocopherols destroyed and led to stronger positive correlations between the amount of Tocopherols destroyed during oxidation and initial concentration of Tocopherols. No synergistic or antagonistic interaction was observed when α- and γ-Tocopherols were added together to autooxidizing p-SFO.
Dean Dellapenna - One of the best experts on this subject based on the ideXlab platform.
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Tocopherols protect synechocystis sp strain pcc 6803 from lipid peroxidation
Plant Physiology, 2005Co-Authors: Hiroshi Maeda, Yumiko Sakuragi, Donald A Bryant, Dean DellapennaAbstract:Tocopherols (vitamin E) are lipid-soluble antioxidants synthesized only by photosynthetic eukaryotes and some cyanobacteria, and have been assumed to play important roles in protecting photosynthetic membranes from oxidative stress. To test this hypothesis, tocopherol-deficient mutants of Synechocystis sp. strain PCC 6803 (slr1736 and slr1737 mutants) were challenged with a series of reactive oxygen species-generating and lipid peroxidation-inducing chemicals in combination with high-light (HL) intensity stress. The tocopherol-deficient mutants and wild type were indistinguishable in their growth responses to HL in the presence and absence of superoxide and singlet oxygen-generating chemicals. However, the mutants showed enhanced sensitivity to linoleic or linolenic acid treatments in combination with HL, consistent with Tocopherols playing a crucial role in protecting Synechocystis sp. strain PCC 6803 cells from lipid peroxidation. The tocopherol-deficient mutants were also more susceptible to HL treatment in the presence of sublethal levels of norflurazon, an inhibitor of carotenoid synthesis, suggesting carotenoids and Tocopherols functionally interact or have complementary or overlapping roles in protecting Synechocystis sp. strain PCC 6803 from lipid peroxidation and HL stress.
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vitamin e is essential for seed longevity and for preventing lipid peroxidation during germination
The Plant Cell, 2004Co-Authors: Scott E Sattler, Laura U Gilliland, Maria Magallaneslundback, Mike Pollard, Dean DellapennaAbstract:Tocopherols (vitamin E) are lipophilic antioxidants synthesized by all plants and are particularly abundant in seeds. Despite cloning of the complete suite of tocopherol biosynthetic enzymes and successful engineering of the tocopherol content and composition of Arabidopsis thaliana leaves and seeds, the functions of Tocopherols in plants have remained elusive. To address this issue, we have isolated and characterized two VITAMIN E loci (VTE1 and VTE2) in Arabidopsis that when mutated result in tocopherol deficiency in all tissues. vte1 disrupts tocopherol cyclase activity and accumulates a redox-active biosynthetic intermediate, whereas vte2 disrupts homogentisate phytyl transferase activity and does not accumulate pathway intermediates. Mutations at either locus cause significantly reduced seed longevity compared with the wild type, indicating a critical role for Tocopherols in maintaining viability during quiescence. However, only vte2 mutants exhibited severe seedling growth defects during germination and contained levels of lipid hydroperoxides and hydroxy fatty acids elevated up to 4- and 100-fold, respectively, relative to the wild type. These data demonstrate that a primary function of Tocopherols in plants is to limit nonenzymatic lipid oxidation during seed storage, germination, and early seedling development. The vte mutant phenotypes also explain the strong selection for retention of tocopherol biosynthesis during the evolution of seed-bearing plants.
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elevating the vitamin e content of plants through metabolic engineering
Science, 1998Co-Authors: David K Shintani, Dean DellapennaAbstract:α-Tocopherol (vitamin E) is a lipid-soluble antioxidant synthesized only by photosynthetic organisms. α-Tocopherol is an essential component of mammalian diets, and intakes in excess of the U.S. recommended daily allowance are correlated with decreased incidence of a number of degenerative human diseases. Plant oils, the main dietary source of Tocopherols, typically contain α-tocopherol as a minor component and high levels of its biosynthetic precursor, γ-tocopherol. A genomics-based approach was used to clone the final enzyme in α-tocopherol synthesis, γ-tocopherol methyltransferase. Overexpression of γ-tocopherol methyltransferase inArabidopsis seeds shifted oil compositions in favor of α-tocopherol. Similar increases in agricultural oil crops would increase vitamin E levels in the average U.S. diet.
M Czauderna - One of the best experts on this subject based on the ideXlab platform.
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alkaline saponification results in decomposition of Tocopherols in milk and ovine blood plasma
Journal of Chromatography B, 2007Co-Authors: M Czauderna, J KowalczykAbstract:Alkaline saponification of entire sample matrixes for quantification of α-, γ-, δ-Tocopherols (α-T, γ-T, δ-T) and α-tocopherol acetate (α-TAc) was examined. High-performance liquid chromatography was used to measure α-T, γ-T, δ-T and α-TAc in tocopherol standard solutions, milk and ovine blood plasma. Saponification in the presence of vitamin C decreases the concentration of Tocopherols, especially α-T and γ-T. The poor recovery of Tocopherols is due to the decomposition of Tocopherols in saponified standard solutions, milk or plasma. Saponification of samples in the presence of 2,[6]-ditertbutyl-p-cresol or flushed only with a stream of Ar resulted in a major decrease in the concentrations of α-T, γ-T, δ-T and α-TAc in comparison with saponification in the presence of vitamin C.
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Alkaline saponification results in decomposition of Tocopherols in milk and ovine blood plasma.
Journal of chromatography. B Analytical technologies in the biomedical and life sciences, 2007Co-Authors: M Czauderna, J KowalczykAbstract:Alkaline saponification of entire sample matrixes for quantification of alpha-, gamma-, delta-Tocopherols (alpha-T, gamma-T, delta-T) and alpha-tocopherol acetate (alpha-TAc) was examined. High-performance liquid chromatography was used to measure alpha-T, gamma-T, delta-T and alpha-TAc in tocopherol standard solutions, milk and ovine blood plasma. Saponification in the presence of vitamin C decreases the concentration of Tocopherols, especially alpha-T and gamma-T. The poor recovery of Tocopherols is due to the decomposition of Tocopherols in saponified standard solutions, milk or plasma. Saponification of samples in the presence of 2,[6]-ditertbutyl-p-cresol or flushed only with a stream of Ar resulted in a major decrease in the concentrations of alpha-T, gamma-T, delta-T and alpha-TAc in comparison with saponification in the presence of vitamin C.
Kathleen Warner - One of the best experts on this subject based on the ideXlab platform.
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effects on the flavor and oxidative stability of stripped soybean and sunflower oils with added pure Tocopherols
Journal of Agricultural and Food Chemistry, 2005Co-Authors: Kathleen WarnerAbstract:Effects of Tocopherols on the oxidative stability of stripped vegetable oils were studied by adding pure Tocopherolsα, β, γ, and δin their naturally occurring proportions in soybean and sunflower oils to the triacylglycerols (TAG) of soybean and sunflower oils. Soybean and sunflower oils were purified by stripping all minor constituents, leaving the triacylglycerols. Pure Tocopherols in the proportion typical of sunflower oilhigh α, low γ, and low δwere added to purified sunflower oil and to purified soybean oil. Pure Tocopherols in the proportion typical of soybean oillow α, high γ, and high δwere added to the purified oils. Oils were subjected to accelerated autoxidation using oven storage at 60 °C in the dark and accelerated photooxidation at 7500 lx light intensity at 30 °C. Oxidation levels of aged oils were measured by the formation of both peroxides and volatile compounds and by flavor analysis. Results from substituting the tocopherol profile from one oil type to another varied on the basis of whe...
