Increased Α-tocopherol Content Research Articles

Novel milk fat fractions for health and functionality obtained by short-path distillation

Medium-chain fatty acids (MCFA) are associated with various health benefits, such as enhanced insulin sensitivity and reduced appetite. The study explored the potential of combining dry or solvent fractionation with short-path distillation (SPD) to obtain milk fat (MF) fractions enriched in MCFA. By using only SPD, a 2-fold increase in MCFA and an 18-fold increase in α-tocopherol in distillates was obtained compared to native MF. The distillate has a lower melting temperature than does MF. Pre-fractionation processes before SPD did not lead to an additional increase in MCFA. The study demonstrates the potential of SPD to produce MF fraction (distillate) with significant enrichment in MCFA, differed thermal behavior, and increased α-tocopherol content while keeping the FA composition and thermal properties of the remaining fraction (retentate) similar to MF as only 10% of the milk fat have been removed.

Genetic Variability of Tocol Content in a Genebank Collection of Temperate Maize Inbred Lines from Southeastern Europe

Maize is considered a promising candidate for biofortification through breeding, given its widespread cultivation and significance as a food crop. This cost-effective and sustainable approach could be used to increase the content of different tocol compounds, i.e., vitamin E, in maize grain due to the well-documented genetic variability. In the present study, an evaluation of the content of nine different tocol traits was performed in a genebank collection of 88 inbred lines of temperate maize grown at two locations in Croatia in 2019. A large genotypic variability within the studied material was observed for α-tocopherol, γ-tocopherol, δ-tocopherol, total tocopherols, α-/γ-tocopherol ratio, α-tocotrienol, γ-tocotrienol, total tocotrienols and total tocols with corresponding coefficients of variation of 52, 61, 51, 45, 106, 24, 54, 33 and 38%, respectively. Heritability estimates ranged from 0.66 for α-tocotrienol to 0.95 for δ-tocopherol. The content of α-tocopherol, which has the highest vitamin E activity and is therefore most interesting for selection, was not significantly correlated with either grain color or grain type. Comparison of the effects of simulated selection with an intensity of 20% on increased α-tocopherol content using the two selection criteria, absolute α-tocopherol content and α-/γ-tocopherol ratio, showed that the highest absolute α-tocopherol content was a better selection criterion. Indeed, simulated selection based on the absolute α-tocopherol content resulted in a 64% increase in this compound without significantly affecting the total tocopherols, the total tocotrienols, and the α-/γ-tocopherol ratio.

Fillet Quality in Rainbow Trout (Oncorhynchus mykiss) Raised on Different Dietary Oils Over a Long-Term Feeding Trial

ABSTRACT Effects of dietary fish oil replacement with vegetable oils on physical and sensorial qualities and shelf life of rainbow fillet were investigated. Color did not change in red muscle, while white muscle was redder (a* 0.88) in hazelnut oil-fed fish. Red muscles from fish oil-fed fish had higher lipid peroxidation in all cases, while dietary hazelnut oil decreased lipid peroxidation and increased α-tocopherol content. General acceptance by consumers did not change among treatments. Overall, fish oil replacement did not cause any remarkable inconvenience in sensory attributes, on the contrary, dietary vegetable oils, especially hazelnut oil, increased oxidative stability during storage.

Milk biofortification through dietary supplementation of combined selenium, vitamin E and sunflower oil

• dietary sunflower oil and antioxidants increased selenium and alpha-tocopherol levels in milk from Jersey cows. • milk biofortification achieved by dietary supplements of antioxidants and sunflower oil. • increased selenium and alpha-tocopherol levels in milk increase nutritional value for humans. The aim of this study was to verify the effect of selenium and vitamin E (antioxidants) and sunflower oil added to the diet of lactating cows to improve the milk nutrient profile. The trial had a completely randomized block design carried out with 32 Jersey cows distributed into four treatments: Control; Antioxidants (3.5 mg of organic selenium/ kg in dry matter (DM) + 2000 IU of vitamin E/day); Sunflower oil (SFO, 4% of sunflower oil/kg in DM); Antioxidants + SFO (3.5 mg of organic selenium/ kg in DM + 2000 IU of Vit. E /day + 4% of sunflower oil/ kg in DM, for 76 days. Antioxidants additives added to the diet of cows tended to decrease energy intake and increase selenium and vitamin E intake. SFO increased the ether extract intake and tended to decrease the protein content in milk. The selenium content in milk and serum selenium ratio was increased with the addition of antioxidants and tended to decrease with the addition of SFO. SFO increased α-tocopherol content in serum and tended to decrease it in milk. SFO increased cholesterol, HDL, and LDL in the serum of cows. Milk with the most desirable nutritional profile for human nutrition and health was produced by cows supplemented with antioxidants and sunflower oil, with higher selenium and alpha-tocopherol levels compared to milk commonly produced, without affecting animal productivity.

Valorization of Winery Waste: Prokupac Grape Seed as a Source of Nutritionally Valuable Oil

Valorization of winery waste is a promising solution for waste management with additional benefit of bioactive compounds isolation. The aim of this study was to analyze the nutritional and bioactive potential of oil derived from Serbian autochthonous grape seed variety Prokupac and to compare it with known international grape varieties. Additionally, two extraction methods (ultrasound assisted extraction and cold pressing) were used in order to determine their influence on physico-chemical and nutritive characteristics of grape seed oil. Different methods, including determination of physicochemical properties, content of bioactive compounds, oxidative stability and antioxidative capacity were used for the characterization of grape seed oils. Results indicated that the higher yield was obtained by ultrasound assisted extraction compared to cold pressing. The application of ultrasound assisted extraction resulted in increased α-tocopherol content and better antioxidant capacity and oxidative stability of oil. Significant differences in bioactive composition were observed for Prokupac seed oil compared to the other grape varieties. Oil extracted from Prokupac grape seed had the lowest content of polyunsaturated and the highest content of saturated fatty acids, the highest content of α-tocopherol and consequently, the best antioxidative capacity. Prokupac grape seed has a great potential for isolation of nutritive and bioactive valuable oil.

Increasing the α-tocopherol content and lipid oxidative stability of meat through dietary Cistus ladanifer L. in lamb fed increasing levels of polyunsaturated fatty acid rich vegetable oils

The aim of this study was to evaluate the effect of the dietary inclusion of Cistus ladanifer L. and vegetable oils on intramuscular fat composition, muscle antioxidant status and lipid oxidative stability, and explore the mechanism by which dietary Cistus ladanifer limits the lipid oxidation. Lambs were assigned 9 diets, corresponding to 3 levels of Cistus ladanifer (50, 100 and 200 g/kg DM) and 3 levels of oil (0, 40 and 80 g/kg DM). Oil supplementation increased highly peroxidizable fatty acid content and the peroxidizability index (P < .05). Muscle phenolic content, reducing ability and radical scavenging ability were not affected by Cistus ladanifer (P > .05). The highest level of Cistus ladanifer enhanced muscle resistance to lipid oxidation (P = .006) and increased α-tocopherol content (P = .005), reducing meat lipid oxidation over 7 days of storage (P < .001). Results showed that Cistus ladanifer has a protective effect against lipid oxidation through increasing α-tocopherol concentration in the muscle.

Vitamin E in Plants: Biosynthesis, Transport, and Function.

Vitamin E, which includes both tocopherols and tocotrienols, comprises lipid-soluble antioxidants that modulate lipid peroxidation. Recently, significant advances have been made in our understanding of vitamin E biosynthesis, transport, and function. The phytyl moiety from chlorophyll degradation is used for tocopherol biosynthesis. An α-tocopherol-binding protein (TBP) has been identified in tomato (SlTBP) serving in intraorganellar vitamin E transport in plants. Moreover, α-tocopherol not only scavenges free radicals through flip-flop movements in the lipid bilayer, but may also contribute to fine-tuning the transmission of specific signals outside chloroplasts. Vitamin E, and α-tocopherol in particular, appear to be essential for plant development and help to provide the most suitable response to a number of environmental stresses.

Roles of microbes and lipolytic enzymes in changing the fatty acid profile, α-tocopherol and β-carotene of whole-crop oat silages during ensiling and after exposure to air

The aim of present study is to clarify the roles of microbes, lipase and lipoxygenase in changes of fatty acids (FA) profile, α-tocopherol and β-carotene of whole-crop oat silages treated without (Control) or with Lactobacillus plantarum (LP) and propionic acid additive (PA) during ensiling and aerobic exposure. Whole-crop oat was harvested from the 8 fields (1000 m2 per field) and mixed as a pile which was then separated into 12 piles in the laboratory. The 12 piles (630 g per pile) were randomly ensiled with above additive treatments. Four piles per additive treatment were separately filled into 4 experimental silos (polyvinyl chloride bottle, 1 L), immediately. After ensiling for 65 d at room temperature, a part of silages (200 g) was sampled and the others (420 g) were exposed to air for 4 d. The increase of palmitic acid, reduction of linoleic acid and α-linolenic acid, and β-carotene loss occurred in the control silage because of bio-hydrogenation of lactic acid bacteria, lipase responsible for degrading lipid into FA, and lipoxygenase in charge of degrading β-carotene, linoleic acid and α-linolenic acid after ensiling. Compared with the control silage, an increase in linoleic acid content was found in LP-treated silage because LP increased the activity of lipase; Moreover, higher activity of lipoxygenase resulted in big losses of α-linolenic acid and β-carotene in LP-treated silage. In PA-treated silage, effects of lipase and lipoxygenase on changing the contents of linoleic acid and α-linolenic acid were not found, and slight loss of β-carotene was observed. During aerobic exposure for 4 d, multiplication of aerobic bacteria and yeasts resulted in most of FA and β-carotene loss and increased α-tocopherol content in all treatments. Compared with the control and LP-treated silages, PA relieved loss of β-carotene and reductions of linoleic acid and α-linolenic acid, because PA restrained the multiplication of aerobic bacteria and yeasts. In conclusion, lipase had a contribution in increasing contents of palmitic acid and linoleic acid during ensiling, and microbes played a potential role in increasing α-tocopherol content before aerobic deterioration in the present study.

Overexpression of Medicago sativa TMT elevates the α-tocopherol content in Arabidopsis seeds, alfalfa leaves, and delays dark-induced leaf senescence

Alfalfa (Medicago sativa L.) is a major forage legume for livestock and a target for improving their dietary quality. Vitamin E is an essential vitamin that animals must obtain from their diet for proper growth and development. γ-tocopherol methyltransferase (γ-TMT), which catalyzes the conversion of δ- and γ-tocopherols (or tocotrienols) to β- and α-tocopherols (or tocotrienols), respectively, is the final enzyme involved in the vitamin E biosynthetic pathway. The overexpression of M. sativa L.’s γ-TMT (MsTMT) increased the α-tocopherol content 10–15 fold above that of wild type Arabidopsis seeds without altering the total content of vitamin E. Additionally, in response to osmotic stress, the biomass and the expression levels of several osmotic marker genes were significantly higher in the transgenic lines compared with wild type. Overexpression of MsTMT in alfalfa led to a modest, albeit significant, increase in α-tocopherol in leaves and was also responsible for a delayed leaf senescence phenotype. Additionally, the crude protein content was increased, while the acid and neutral detergent fiber contents were unchanged in these transgenic lines. Thus, increased α-tocopherol content occurred in transgenic alfalfa without compromising the nutritional qualities. The targeted metabolic engineering of vitamin E biosynthesis through MsTMT overexpression provides a promising approach to improve the α-tocopherol content of forage crops.

Effect of feeding Aspergillus awamori and canola seed on the growth performance and muscle fatty acid profile in broiler chicken.

The aim of this study was to examine effects of dietary supplementation with Aspergillus awamori and feeding canola seed on the growth and fatty acid profile in broilers. Twenty-eight chicks (15 days old) were assigned to the following groups: (1) control, fed a basal diet; (2) awamori, fed the basal diet supplemented with 0.05% A. awamori; (3) canola, fed a diet containing 5% canola seed; and (4) canola + awamori, fed the canola diet supplemented with A. awamori (seven birds/group). Body weight gain was increased by A. awamori but not influenced by canola seed. Breast muscle weight was increased in either awamori or canola groups. Although plasma triglyceride and cholesterol were decreased by feeding A. awamori or canola seed, fat content in the breast muscle were increased, accompanied by decrease in saturated fatty acids and increase in unsaturated fatty acids. Moreover, decreased thiobarbituric acid reactive substance and increased α-tocopherol content in the breast muscle was observed in all experimental groups. In conclusion, these results suggested that feeding canola seed and A. awamori might improve growth performance, and modified muscle fatty acid profile and α-tocopherol content, suggesting that they may improve meat quality.

Modulation of antioxidant machinery in α-tocopherol-enriched transgenic Brassica juncea plants tolerant to abiotic stress conditions

The antioxidant machinery in plants consists of several components with unique or overlapping functions that combat the deleterious production of reactive oxygen species (ROS) induced by stress conditions. Tocopherols are a group of powerful antioxidants having additional roles in signaling and gene expression, with α-tocopherol being the most potent form. In the present study, we used wild-type (WT) and α-tocopherol-enriched transgenic (TR) Brassica juncea plants grown under salt, heavy metal, and osmotic stress to compare their relative tolerance to these stresses and to assess the effects of increased α-tocopherol content on the other antioxidative enzymes and molecules. The oxidative damage caused by induced stress was lower in TR plants compared to WT plants as assessed by their higher relative water content and lower electrolyte leakage, malondialdehyde content as well as H(2)O(2) accumulation. Lesser superoxide and H(2)O(2) accumulation was also observed by histochemical staining in TR seedlings exposed to stress. Though no significant differences were evident under normal growth conditions, TR plants showed higher activities and transcript levels of antioxidant enzymes superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase than WT plants under similar stress conditions. A decrease in ascorbate and glutathione content with marginally higher reductive ratios of these compounds was also observed in TR plants under the stress conditions. Our findings implicate the role of higher α-tocopherol levels in conferring better tolerance against salt, heavy metal, and osmotic stresses and also establish the existence of interplay between this lipid-soluble antioxidant and other water-soluble components of plant antioxidant defense.

Expression of γ-tocopherol methyltransferase gene from Brassica napus increased α-tocopherol content in soybean seed

A cDNA encoding &gamma;-tocopherol methyltransferase from Brassica napus (BnTMT) was overexpressed in soybean [Glycine max (L.) Merr.] under the control of seed-specific promoter of Arabidopsis fatty acid elongase 1 (FAE1) or soybean glycinin G1. Two and three transgenic plants were selected, respectively, after Agrobacterium-mediated transformation. Polymerase chain reaction (PCR) and Southern blots confirmed that BnTMT was single-copy integrated into the genome of transgenic plants. RT-PCR analysis showed that the expression of BnTMT was higher in the immature cotyledons than in the mature cotyledons, while no expression was detected in the leaves. Moreover, the expression level under the control of FAE1 was higher than that of G1. HPLC analysis indicated that the seed-specific expression of BnTMT resulted in 11.1-fold and 18.9-fold increase in &alpha;- and &beta;-tocopherol content, respectively, in T2 seed. These results suggested that introducing BnTMT into soybean can be used to increase the vitamin E composition in seeds.

Dietary lipoic acid influences antioxidant capability and oxidative status of broilers.

The effects of lipoic acid (LA) on the antioxidant status of broilers were investigated. Birds (1 day old) were randomly assigned to four groups and fed corn-soybean diets supplemented with 0, 100, 200, 300 mg/kg LA, respectively. The feeding program included a starter diet from 1 to 21 days of age and a grower diet from 22 to 42 days of age. Serum, liver and muscle samples were collected at 42 days of age. For antioxidant enzymes, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity in serum, liver and breast muscle significantly increased in chickens fed with LA. The concentration of malondiadehyde (MDA), an indicator of lipid peroxidation, was significantly lower in serum, liver and leg muscle in birds that received LA than in the control group. Treatments with LA significantly increased glutathione (GSH) content in liver and increased α-tocopherol content in leg muscle as compared to the control. These results indicate that dietary supplementation with 300 mg/kg LA may enhance antioxidant capability and depress oxidative stress in broilers.

Expression of γ-tocopherol methyltransferase gene from Brassica napus increased α-tocopherol content in soybean seed

Expression of γ-tocopherol methyltransferase gene from Brassica napus increased α-tocopherol content in soybean seed

Administration of RRR-α-tocopherol to pregnant mares stimulates maternal IgG and IgM production in colostrum and enhances vitamin E and IgM status in foals

This study assessed the effect of a vitamin E supplement given to pregnant mares on immunoglobulins (Ig) levels in foals. In addition, the fatty acid (FA) content and composition of the mares' milk was assessed. Milk α-tocopherol concentrations were compared between pregnant Danish Warmblood mares (n = 17) given a daily oral supplement of 2500 international units (IU) RRR-α-tocopherol in the last 4 weeks of pregnancy and a group of unsupplemented mares (n = 17) receiving 170-320 IU vitamin E daily originating from the feed. Milk α-tocopherol was higher in supplemented mares (36.7, 12.4 and 9.8 μmol/l respectively) in relation to control mares (13.1, 6.4 and 5.8 μmol/l on days 1, 2 and 3 respectively; p < 0.001). Milk IgG was higher on days 2 and 3 post-partum (PP) in supplemented mares (1.03 and 0.73 mg/ml respectively) in relation to control mares (0.79 and 0.56 mg/ml respectively; p < 0.05). Milk IgM was higher on days 2 and 3 post-partum (PP) in supplemented mares (0.19 and 0.17 mg/ml) in relation to control mares (0.13 and 0.11 mg/ml respectively; p < 0.05). Plasma α-tocopherol in foals was higher from supplemented mares on days 1, 2 and 3 (5.7, 14.8 and 19.2 μmol/l respectively) in relation to foals from control mares (3.6, 6.1 and 7.6 respectively; p < 0.001). Foal plasma IgM was higher from supplemented mares on day 3 (0.50 mg/ml) in relation to foals from control mares (0.32 mg/ml; p < 0.001). The total FA content in milk was highest on day 1 (21.6 g FA/kg milk) in relation to days 2 and 3 (13.6 and 13.5 g FA/kg milk respectively; p < 0.001). In conclusion, a daily oral supplement of 2500 IU RRR-α-tocopherol increased α-tocopherol content in mare milk and foal plasma, IgG and IgM in mare milk and IgM in foal plasma.

Antioxidant value addition in human diets: genetic transformation of Brassica juncea with γ-TMT gene for increased α-tocopherol content

Alpha-tocopherol, the most biologically active form of vitamin E, is implicated in decreasing the risk of several types of cancers, coronary heart disease and a number of degenerative human conditions, when taken in excess of the recommended daily allowance. Natural alpha-tocopherol has twice the bioavailability of the synthetic isomer. This study describes a successful attempt at fortifying human diets with natural alpha-tocopherol by taking recourse to genetic engineering of an important oilseed crop, Brassica juncea. Gamma-tocopherol methyl transferase cDNA from Arabidopsis thaliana, coding for the enzyme catalysing the conversion of the large gamma-tocopherol pool to alpha-tocopherol, was overexpressed in B. juncea plants. The successful integration of the transgene was confirmed by PCR and Southern blot analysis, while the enhanced transcript level was evident in the northern blot analysis. HPLC analysis of the seeds of the T1 transgenic lines showed a shift in tocopherol profile with the highest over-expressors having alpha-tocopherol levels as high as sixfold over the non-transgenic controls. This study discusses the production of a transgenic oilseed crop with high alpha-tocopherol levels, which can provide a feasible, innocuous, and inexpensive way of taking the beneficial effects of high alpha-tocopherol intake to the masses.

Increased α-tocopherol content in soybean seed overexpressing the Perilla frutescens γ-tocopherol methyltransferase gene

Tocopherols, with antioxidant properties, are synthesized by photosynthetic organisms and play important roles in human and animal nutrition. In soybean, gamma-tocopherol, the biosynthetic precursor to alpha-tocopherol, is the predominant form found in the seed, whereas alpha-tocopherol is the most bioactive component. This suggests that the final step of the alpha-tocopherol biosynthetic pathway catalyzed by gamma-tocopherol methyltransferase (gamma-TMT) is limiting in soybean seed. Soybean oil is the major edible vegetable oil consumed, so manipulating the tocopherol biosynthetic pathway in soybean seed to convert tocopherols into more active alpha-tocopherol form could have significant health benefits. In order to increase the soybean seed alpha-tocopherol content, the gamma-TMT gene isolated from Perilla frutescens was overexpressed in soybean using a seed-specific promoter. One transgenic plant was recovered and the progeny was analyzed for two generations. Our results demonstrated that the seed-specific expression of the P. frutescens gamma-TMT gene resulted in a 10.4-fold increase in the alpha-tocopherol content and a 14.9-fold increase in the beta-tocopherol content in T2 seed. Given the relative contributions of different tocopherols to vitamin E activity, the activity in T2 seed was calculated to be 4.8-fold higher than in wild-type seed. In addition, the data obtained on lipid peroxidation indicates that alpha-tocopherol may have a role in preventing oxidative damage to lipid components during seed storage and seed germination. The increase in the alpha-tocopherol content in the soybean seed could have a potential to significantly increase the dietary intake of vitamin E.

Expressivity of tocopherol mutations in sunflower

SUMMARY Influences of genetic background, ontogenesis and environment on tocopherol mutations in sunflower were estimated in this study. The content of α/βtocopherols varied from 40/60 to 60/40% in seeds of different inbred lines containing the tph1 gene. The lines containing the tph2 gene ranged widely in α/γtocopherols, from 0/100 to 80/20%. A double mutation showed variability in different inbred lines in α/β/γ/δ-tocopherol contents from maximum expressivity of 0/0/60/40 to minimum 40/25/25/10%, due to incomplete expressivity of tph2. Seed maturation from 10 to 38 DAF influenced tocopherol composition in both normal and mutant genotypes by increasing the α-tocopherol content. The content varied from 81 to 97% in a normal genotype, from 33 to 50% in tph1 mutation and from 0 to 6% in tph2 mutation. Tocopherol mutations were shown to express their phenotype in different parts of a plant. All roots, hypocotyls, leaves, pollen and callus from the seeds, hypocotyls and leaves had normal, tph1, tph2 and double mutation tocopherol profiles depending on the genotype. The only exception was the absence of tph1 expressivity in the green tissue of the leaves. The experiment with day/night temperatures varying during seed development from 20/18 to 30/26°C showed an increased α-tocopherol content from 39 to 48% in tph1 mutation. Both a normal genotype (about 97% of α-tocopherol) and tph2 mutation (about 98% of γ-tocopherol) were constant in these two temperature regimes. Genetic background was the main factor that influenced the expressivity of tph2 in sunflower.

Evolution of fatty acids from intramuscular lipid fractions during ripening of Iberian hams as affected by α-tocopheryl acetate supplementation in diet

The influence of feeding Iberian pigs with and without α-tocopheryl acetate (α-TAc) on fatty acid composition of intramuscular lipids, throughout dry-cured ham maturation was investigated. Supranutritional levels of α-TAc (100 mg α-TAc/kg) increased α-tocopherol content in m. Semimembranosus in comparison to a basal diet containing 5 mg α-TAc/kg (Control: 6.38 vs. E-supplemented: 10.31 μg/g muscle dry matter). Fatty acid composition of lipids in the raw hams was similar whatever the level of vitamin E in the diet. Fatty acid composition of neutral lipids did not change much during ham maturation. In contrast, fatty acid content of polar lipids decreased considerably (∼90%) after 700 days of maturation. At the end of ripening (700 days), the contents of polyunsaturated fatty acids from neutral and polar lipids were significantly higher in hams from Iberian pigs fed on α-TAc-enriched diet than those fed with a basal diet. This result indicates that α-tocopherol-enriched diets maintain polyunsaturated fatty acids in neutral and polar lipid fractions of intramuscular fat in dry-cured hams from Iberian pigs.

Effect of oxidative stress during imbibition of soybean embryonic axes

SynopsisBoth respiration and generation by soybean embryonic axes showed a sharp increase upon germination, leading to a significant increase in the steady-state concentration of and H2O2 after 6 h of imbibition. An assay was developed to assess in vivo generation of reactive oxygen species, based upon DCFH-DA oxidation. Fluorescence of the external medium was dependent on reaction time and axes number and was inhibited by catalase.α-Tocopherol content declined significantly after 24 h of incubation, as compared to the content at the onset of germination. Incubation in the presence of redox cycling agent paraquat (4 mM) for 24 h increased α-tocopherol content to 1.9±0.2 nmol per axis from 1.0 ± 0.1 nmol per axis in the absence of paraquat. Supplementation of the incubation medium with 500 μM Fe-EDTA increased α-tocopherol content to 1.8±0.1 nmol/axis and DCFH-DA oxidation by two-fold.The data presented here showed that active metabolism at the onset of germination increased steady-state concentration of oxygen active species and suggest that cellular content of α-tocopherol is physiologically adjusted as a response to conditions of oxidative stress.