Electron spin resonance spectra of the chromanoxyl radicals derived from tocopherols (vitamin E) and their related compounds

The well resolved electron spin resonance (ESR) of the tocopheroxyl and chromanoxyl radicals derived from α-, β-, γ- and δ-tocopherols (vitamin E), 5,7-dimethyltocol, tocol and their model compounds in degassed toluene by treatment with 2,2-diphenyl-1-picrylhydrazyl were recorded. Their hyperfine coupling constants were determined and assigned using spectrum simulation. Their g-factors were also measured. On the basis of these parameters, the α-tocopheroxyl radical is similar to the 2,2,5,7,8-pentamethylchroman-6-oxyl, 5,7-dimethyltocoxyl and 2,2,5,7-tetramethylchroman-6-oxyl radicals. This suggests that the presence of methyl groups at C-5 and C-7 in tocopherols and chroman-6-ols is of great importance to their antioxidant action. The ESR parameters obtained here are very useful for the identification and quantification of a variety of tocopheroxyl radicals. TMIG-I No. 43     

Microsomal lipid peroxidation: Effect of vitamin E and its functional interaction with phospholipid hydroperoxide glutathione peroxidase

The role of vitamin E in the protection against iron dependent lipid peroxidation was studied in rat liver microsomes and Triton-dispersed microsomal lipid micelles. In these systems, an antioxidant effect of vitamin E at a physiological ratio to phospholipids could be observed only in the presence of phospholipid hydroperoxide glutathione peroxidase (PHGPX) and glutathione. The rationale of this cooperation is discussed on the basis of the hydroperoxyl radical scavenging capacity of vitamin E and the reduction of membrane hydroperoxides by PHGPX. The scavenging of lipid hydroperoxyl radicals by vitamin E, although inhibiting propagation of the peroxidative chain, produces lipid hydroperoxides from which ferrous iron generates alkoxyl radicals that react with vitamin E almost as fast as with fatty acids. Therefore, only if membrane hydroperoxides are continuously reduced by this specific peroxidase does the scavenging of hydroperoxyl radicals by vitamin E lead to an effective inhibition of lipid peroxidation.     

Antioxidant and prooxidant effects of α‐tocopherol in a linoleic acid‐copper(II)‐ascorbate system

The peroxidation of linoleic acid (LA) in the absence and presence of either Cu(II) ions alone or Cu(II)‐ascorbate combination was investigated in aerated and incubated emulsions at 37°C and pH 7. LA peroxidation induced by either copper(II) or copper(II)‐ascorbic acid system followed pseudo‐first order kinetics with respect to primary (hydroperoxides) and secondary (aldehydes‐ and ketones‐like) oxidation products, detected by ferric‐thiocyanate and TBARS tests, respectively. α‐Tocopherol showed both antioxidant and prooxidant effects depending on concentration and also on the simultaneous presence of Cu(II) and ascorbate. Copper(II)‐ascorbate combinations generally led to distinct antioxidant behavior at low concentrations of α‐tocopherol and slight prooxidant behavior at high concentrations of α‐tocopherol, probably associated with the recycling of tocopherol by ascorbate through reaction with tocopheroxyl radical, while the scavenging effect of α‐tocopherol on lipid peroxidation was maintained as long as ascorbate was present. On the other hand, in Cu(II) solutions without ascorbate, the antioxidant behavior of tocopherol required higher concentrations of this compound because there was no ascorbate to regenerate it. Practical applications: Linoleic acid (LA) peroxidation induced by either copper(II) or copper(II)‐ascorbic acid system followed pseudo‐first order kinetics with respect to primary (hydroperoxides) and secondary (e.g., aldehydes and ketones) oxidation products. α‐Tocopherol showed both antioxidant and prooxidant effects depending on concentration and also on the simultaneous presence of Cu(II) and ascorbate. The findings of this study are believed to be useful to better understand the actual role of α‐tocopherol in the preservation of heterogenous food samples such as lipid emulsions. Since α‐tocopherol (vitamin E) is considered to be physiologically the most important lipid‐soluble chain‐breaking antioxidant of human cell membranes, the results can be extended to in vivo protection of lipid oxidation.     

Empfehlungen zur Aufnahme von Vitamin E — heutiger Stand und Ausblick

Recommendations for the intake of vitamin E. Today's RDA values for vitamin E are based on their protective action for unsaturated fatty acids taken up on our food. In recent years, it has been shown that vitamin E has also important functions in our body especially concerning the scavenging of free radicals, and for this action the vitamin E requirement is somewhat higher. Epidemiological data with respect to the prevention of cardiovascular disease indicate that an uptake of more than 30 mg α-tocopherol equivalents is necessary. This amount, however, cannot be taken up by a balanced low fat food as recommended today. It is therefore proposed to include more food fortified with vitamin E in our daily nutrition.     

Thin-layer chromatographic separation of dimethylphosphatidates derived from lecithins

The separation of lecithin derivatives based on their fatty acid substituents has been investigated. Several synthetic and natural lecithins were converted to their corresponding dimethylphosphatidates by hydrolysis with phospholipase D (phosphatidylcholine phospholipase D (phosphatidylcholine phosphatidohydrolase, EC 3.1.4.4) and methylation of the resulting phosphatidic acids with diazomethane. These dimethylphosphatidates were separated into fractions by reversed-phase thin-layer chromatography. Separations were dependent on the total number of methylene groups and double bonds in the two fatty acid chains. Fractionated dimethylphosphatidates were extracted from the plates and fatty acids were determined.     

Einige Aspekte der Bioverfügbarkeit von α-Tocopherol

Some Aspects of α-Tocopherol Bioavailability The bioavailability of α-tocopherol depends on various factors. The ingested esterified form is almost completely hydrolyzed in intestinal tract by esterases prior to absorption. Bile and pancreatic juice are necessary for optimal hydrolyzation, emulgation and absorption of vitamin E. An acid pH- value is required for tocopherol-absorption. Polyunsaturated longchain fatty acids in the diet inhibit whereas medium-chain triglycerides (MCT) enhance the absorption. Moreover, consumption of polyunsaturated fatty acids increases the requirement for antioxidants. Therefore long time consumption of polyunsaturated fatty acids (e. g. fish oil) shouldn't be used without an adequate compensation with antioxidants as well as control of α-tocopherol status. The dosis dependant absorption rate (average = 40%) can't be improved significantly by emulsifiers like Tween 80 or lecithin. Lipoprotein fractions are responsible for transport and distribution oif α-tocopherol with different efficiency: LDL 64%, VLDL 8%, HDL 24%. Vitamin E is rapidely taken up by tissues especially in liver, muscle, adrenal glands and adipose tissue. Beside free α-tocopherol as the typical storage from α-tocopheryl acetate is also detectable. The bioavailability of intravenous administered dl-α-tocopheryl acetate is good. The vitamin E-ester is rapidely eliminated and mainly hydrolyzed. This can be confirmed by a significant increase in the content of free α-tocopherol in plasma.     

Dietary fish oils and long-term malaria protection in mice

Previous studies indicate a suppressive influence of fish oils on rodent malaria. The present work was carried out to study (i) the dose-effect relation between dietary fish oils and lethality of primary malaria infection in mice; (iii) the modifying influence of vitamin E; and (iii) the effect of previous fish oil feeding on parasitemia and lethality of a rechallenge infection. For two or four weeks, groups of weanling male mice were fed a standard laboratory diet or one of eight purified diets containing various amounts of fish oil (providing 6–21% of energy). The diets were prepared with and without vitamin E. After the two-or four-week feeding period, the mice were injected intraperitoneally withPlasmodium yoelii yoelii-infected erythrocytes. Six months after the primary infection (four months after discontinuing fish oil feeding), the surviving mice were again injected intraperitoneally with parasitized red blood cells (or even better—erythrocytes, erythrocytes are used elsewhere). Primary malaria infection was lethal in mice fed standard diet alone or with fish oil and vitamin E added. In contrast, feeding a fish oil-based diet without vitamin E improved survival to at least 70% if the mice had been fed these diets for four weeks. Protection against malaria did not seem to be related to the fish oil dose used. Regardless of the previous fish oil dose, all the mice surviving the primary infection survived the rechallenge infection with low parasitaemias. The results suggest that the prooxidant nature of highly unsaturated fatty acids in fish oils may beneficially influence malaria infection, and may also increase the resistance against reinfection for some time after discontinuing fish oil intake.     

Vitamin E-Bedarf bei Zufuhr von Polyenfettsäuren

Polyunsaturated Fatty Acids and Requirements of Vitamin E The major function of vitamin E is believed to be the protection of cellular membrane lipids against oxygen free-radical attack. In animals, high intakes of polyunsaturated fatty acids without proper antioxidant protection rapidly lead to vitamin E deficiency. Since the peroxidizability of fats increases with the amount and the degree of fatty acid unsaturation, the need for vitamin E increases respectively. Foods high in polyunsaturated fatty acids require, in addition to antioxidant protection to prevent rancidity during storage (technical protection against oxidation. The exact requirements of vitamin E needed for compensating the elevated demand caused by polyunsaturated fatty acids can only be estimated from data in the literature. There are no systematic studies in humans, and the requirements depend on the particular parameter chosen to establish vitamin E deficiency. For humans, a reference value of 0.9 mg IU vitamin E per gram linoleic acid may safely be assumed. For polyunsaturated fatty acids of higher degree of unsaturation and mixtures thereof, the minimum elevated vitamin E demand can be calculated by a formula.     

Antioxidant activity of green teas in different lipid systems

Different commercial green teas from Japan, China, and India, were compared in different lipid systems. Green teas were active antioxidants in bulk corn oil oxidized at 50°C but were prooxidant in the corresponding oil-in-water emulsions. Green teas also were active antioxidants in soybean lecithin liposomes oxidized at 37°C in the presence of cupric acetate as catalyst. At 50°C, however, three of the samples of green tea were active antioxidants in the absence of copper catalyst, and two samples showed prooxidant activity in the presence of copper catalyst. The marked variation in activity among green tea samples may be due partly to differences in their relative partition between phases in different lipid systems. The improved antioxidant activity observed for green teas in lecithin liposomes compared to corn oil emulsions can be explained by the greater affinity of the polar tea catechin gallates for the polar surface of the lecithin bilayers, thus affording better protection against oxidation. Liposomes may thus be appropriate lipid models to evaluate antioxidants for foods containing phospholipids.     

Low doses of eicosapentaenoic acid, docosahexaenoic acid, and hypolipidemic eicosapentaenoic acid derivatives have no effect on lipid peroxidation in plasma

It was of interest to investigate the influence of both high doses of eicosapentaenoic acid (EPA) and low doses of 2-or 3-methylated EPA on the antioxidant status, as they all cause hypolipidemia, but the dose required is quite different. We fed low doses (250 mg/d/kg body wt) of different EPA derivatives or high doses (1500 mg/d/kg body wt) of EPA and DHA to rats for 5 and 7 d, respectively. The most potent hypolipidemic EPA derivative, 2,2-dimethyl-EPA, did not change the malondialdehyde content in liver or plasma. Plasma vitamin E decreased only after supplementation of those EPA derivatives that caused the greatest increase in the fatty acyl-CoA oxidase activity. Fatty acyl-CoA oxidase activity increased after administration of both EPA and DHA at high doses. High doses of EPA and DHA decreased plasma vitamin E content, whereas only DHA elevated lipid peroxidation. In liver, however, both EPA and DHA increased lipid peroxidation, but the hepatic level of vitamin E was unchanged. The glutathione-requiring enzymes and the glutathione level were unaffected, and no significant changes in the activities of xanthine oxidase and superoxide dismutase were observed in either low-or high-dose experiments. In conclusion, increased peroxisomal β-oxidation in combination with high amounts of polyunsaturated fatty acids caused elevated lipid peroxidation. At low doses of polyunsaturated fatty acids, lipid peroxidation was unchanged, in spite of increased peroxisomal β-oxidation, indicating that polyunsaturation is the most important factor for lipid peroxidation.     

Tocotrienols from palm oil: Electron spin resonance spectra of tocotrienoxyl radicals

The major vitamin E components present in palm oil, viz. α-tocopherol, α⁻, ψ-and δ-tocotrienols, have been isolated and their structures verified by the NMR spectra of their acetate and succinate derivatives. Oxidation of γ-and δ-tocotrienols with alkaline K₃Fe(CN)₆ gave isolable dimeric species, which were studied by¹³C NMR. Free radicals generated from the monomeric and dimeric tocotrienols were investigated using ESR spectroscopy. The distinction between antioxidant activity and antioxidant capacity of vitamin E isomers is discussed.     

Vitamin E bei rheumatischen Erkrankungen,immunologische und klinische Wirkungen

Effects of vitamin E on immune and inflammatory responses in rheumatic diseases. In rheumatic diseases immune and inflammatory responses result in the damage of the involved tissue. The immune response is mediated by cells of the immune system, which are activated and stimulated by vitamin E, eventually resulting in an enhanced immune reaction. The inflammatory response is associated with formation of free oxygen radicals, leading to activation of the eicosanoid cascade and the cytokine system. Liberation of arachidonic acid from membrane lipids, and its oxidative transformation to eicosanoids are inhibited by vitamin E, resulting in amelioration of the inflammatory response. Moreover, vitamin E has been shown to decrease formation of adhesion molecules, and to diminish proinflammatory signaling to the nucleus of the cell. These findings demonstrate several antiinflammatory properties of Vitamin E. Free oxygen radicals are also involved in cartilage and bone destruction in rheumatoid arthritis. Findings from animal experiments argue for an osteoprotective effect of vitamin E. Some short-term clinical studies have demonstrated an amelioration of laboratory findings and clinical symptoms in patients with rheumatic diseases during supplementation with vitamin E. Studies over prolonged periods of time are needed to evaluate the effect of vitamin E on immune and inflammatory responses, on osteodestruction and on clinical symptoms in rheumatic diseases, especially with regard to the interactions with the other antioxidants of the redox chain.     

纳能托[注]超微载体系统的透皮性能研究

研究了质量分数为 2 %维生素E醋酸酯分别在纳能托[注 ] 超微载体系统、超小脂质体系统以及辛酸 /癸酸甘油三酯溶液中的体外活皮肤渗透性能。精确测定了皮肤不同深度层面区间中总维生素E以及纯维生素E的含量。研究发现 :含有维生素E醋酸酯的纳能托[注 ] 超微载体—天来达[注 ] E能够以其超小的体积 (d平均 <3 0nm )和紧密的结构有效通过人体皮肤的角质层屏障到达表皮层、真皮层、皮下组织以及深达 12 5 0 μm的皮肤脂肪层 ,并能够在皮肤中活性酶的作用下大量转化成为具有活性的纯维生素E (即维生素E醇 ) ,从而有效营养皮肤 ,防止皮肤细胞质的氧化及紫外线引起的自由基老化等     

The biological consequences of feeding polyunsaturated fatty acids to antioxidant-deficient animals

The addition of polyunsaturated fatty acids (PUFA) to diets deficient in vitamin E and other effective antioxidants results in a variety of symptoms in animals. For example, the feeding of such diets to rats results in muscular dystrophy, testis degeneration, dental depigmentation, brown discoloration of the fat and and uterus and creatinuria Similar diets fed to rabbits and ruminants results in muscular dystrophy. In chickens the symptoms observed are encephalomalacia, lowered egg production, and poor hatchability. The addition of PUFA to diets is known to result in the destruction of vitamin E in the diet or in the tissues of animals as a result of free radicals produced during the autooxidation of the PUFA. However, in several studies, this possible explanation for the development of vitamin E deficiency symptoms has been made untenable. In such studies the more likely explanation for development of symptoms is thein vivo peroxidation of PUFA in the tissues of animals following incorporation of large amounts of PUFA in lipid structures and depletion from the tissues of vitamin E and other biologically effective antioxidants.     

Enzymatic hydrolysis of oat and soya lecithin: Effects on functional properties

Enzymatic hydrolysis of oat and soy lecithins and its effects on the functional properties of lecithins were investigated. The phospholipase used was most efficient at low enzyme and substrate concentrations. More fatty acids were released from soy lecithin than from oat lecithin. The maximum degree of hydrolysis was 760 μmol free fatty acids per gram soy lecithin and 170 μmol free fatty acids per gram oat lecithin. On the basis of the total carbohydrate and phosphorus contents in the polar fractions of the lecithins, oat lecithin contained more glycolipids and less phospholipids than soy lecithin. With regard to functional properties, the stability of oil-in-water emulsions was enhanced by hydrolyzed soy lecithin and by crude and hydrolyzed oat lecithins, but only hydrolyzed soy lecithin prevented the recrystallization of barley starch. The dissociation enthalpy of amylose-lipid-complex (AML-complex) was significantly higher when hydrolyzed soy lecithin was present. Hydrolyzed oat lecithin slightly affected the dissociation enthalpy of AML-complex. The other lecithins had no effect on recrystallization or dissociation enthalpies in the barley-starch matrix.     

The effect of a moderately thermoxidized dietary fat on the vitamin E status,the fatty acid composition of tissue lipids,and the susceptibility of low-density lipoproteins to lipid peroxidation in rats

Several studies demonstrated that dietary oxidized oils markedly affect the vitamin E status and alter the fatty acid composition of tissue lipids in animals. It must however be emphasized that highly oxidized oils reduce the feed intake of animals, which makes it difficult to interpret the results. Therefore, the present study used a moderately thermoxidized soybean oil (peroxide value: 75 mEq O₂/kg), having a similar fatty acid composition as fresh soybean oil (peroxide value: 9.5 mEq O₂/kg) which was used as control. Moreover, according to a bifactorial design, two different vitamin E supplementary levels (11 vs. 511 mg α-to-copherol equivalents per kg diet) were used. The experiment was conducted with male Sprague-Dawley rats. The feeding period lasted for 40 days. In order to assess the vitamin E status, the vitamin E concentrations in plasma, liver, heart, kidney, and adipose tissue were determined. The vitamin E supply had a pronounced effect on the vitamin E concentrations of those tissues whereas the type of fat had only a slight effect. The fatty acid composition of total lipids from liver, erythrocytes, and low-density lipoproteins was also only slightly influenced by the oxidized fat. The osmotic fragility of erythrocytes was even reduced by feeding the oxidized oil. With a low vitamin E supply, the in vitro susceptibility of low-density lipoproteins to lipid peroxidation was slightly increased by feeding the oxidized oil. In contrast, with a high vitamin E supply, there was no adverse effect of the dietary oxidized oil on the susceptibility of low-density lipoproteins to lipid peroxidation. Feeding the oxidized oil, however, increased the concentrations of malondialdehyde in low-density lipoproteins suggesting an increased in vivo lipid peroxidation. Therefore, it cannot be ruled out that moderately oxidized dietary fats increase the atherogenicity of low-density lipoproteins. In contrast, a moderately oxidized oil scarcely affected the vitamin E status and the fatty acid composition of tissue lipids.     

Esterification effect on the recovery of vitamin E from palm oil refining residues by molecular distillation

Waste edible oils are an alternative source of high-value natural compounds. Vitamin E can be recovered from palm oil refining residues by molecular distillation. However, the presence of other lipophilic molecules compromises the selective separation of vitamin E. Esterification of the free fatty acids can enhance the selective separation of vitamin E by molecular distillation, but the conditions for carrying out the reaction need to be investigated to simultaneously ensure the conversion of free fatty acids and the reduction of vitamin E losses. Thus, this study investigated the effect of the esterification of the industrial waste on the recovery of vitamin E by molecular distillation. Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and analysis for fats and oils preconized by the American Oil Chemists' Society (AOCS) were used in the characterization of the industrial waste. Determination of the best condition to carry out the reaction was obtained by a central composite rotational design (CCRD) using the response surface methodology (RSM) and the desirability profile. The results showed that the best condition for the esterification was at 64°C, 213 min, 2 wt.% sulphuric acid, and a 10/1 methanol/free fatty acids molar ratio. This reaction condition achieved 97.9% conversion of free fatty acids and less than 3% of vitamin E loss. The esterification promoted concentration of vitamin E in the residue stream (145.4%) and reduction in the distillate stream (87.8%). Therefore, the obtained results presented a suitable route to obtaining vitamin E concentrate and adding value to an industrial residue.     

Effect of dietary vitamin E levels on fatty acid profiles and nonenzymatic lipid peroxidation in the guinea pig liver

Guinea pigs were fed for five weeks with three diets containing different levels of vitamin E: LOW (but nondeficient, 15 mg of vitamin E/kg diet), MEDIUM (150 mg/kg diet), and HIGH (1,500 mg/kg diet). Dietary vitamin E supplementation did not change oxidative stress indicators in the hydrophilic compartment but increased liver α-tocopherol in a dose-dependent way and strongly decreased sensitivity to nonenzymaticin vitro liver lipid peroxidation. This last effect was already observed in group MEDIUM, and no further decrease inin vitro lipid peroxidation occurred from group MEDIUM to group HIGH. The protective effect of vitamin E againstin vitro lipid peroxidation was observed even though an optimum dietary concentration of vitamin C for this animal model was present in the three different vitamin E diets. Both HIGH and LOW vitamin E decreased percentage fatty acid unsaturation in all phospholipid fractions from membrane origin in relation to group MEDIUM. The results, together with previous information, show that both vitamin E and vitamin C at intermediate concentrations are needed for optimal protection against lipid peroxidation and loss of fatty acid unsaturation even in normal nonstressful conditions. These protective concentrations are higher than those needed to avoid deficiency syndromes.     

Metabolic effects of selenium as related to vitamin E

Trace amounts of dietary selenium, which prevent certain vitamin E deficiency symptoms, have been found to affect the composition of chick tissues. Both selenium and vitamin E increased liver coenzyme A levels to normal when cystine was omitted from the diet. Liver and plasma total fatty acids were unaltered by selenium but vitamin E increased the arachidonic acid content slightly. There was no effect of either selenium or vitamin E on total lipid, cholesterol, phopholipid or coenzyme Q in liver. Low dietary levels of either selenium or vitamin E, which were insufficient in preventing deficiency symptoms, completely eliminated mortality from toxic amounts of a dietary antioxidant. The ability of dietary selenium to reducein vitro lipid peroxidation in chick liver homogenates was not demonstrable with rat liver. Presented at the AOCS meeting in Toronto, Canada, 1962.     

Einfluß der Vitamin E-Supplementierung auf den antioxidativen Stoffwechsel des Ferkels bei unterschiedlicher Linolsäureversorgung

Influence of Vitamin E Supplementation on the Antioxidative Metabolism of Young Pigs at Different Intakes of Linoleic Acid To characterize the antioxidative metabolism of young pigs influenced by different vitamin E and linoleic acid concentrations in the diet, the in vitro pentane production of the liver microsomes, the α-tocopherol concentration in total liver and liver microsomes, and the fatty acid content of the liver microsomes were investigated. Increased vitamin E concentrations in the diet resulted in decreased pentane production, increased α-tocopherol concentration of total liver and microsomes and reduced absolute content of total fatty acids of the microsomes. However, the n-6-fatty acids decreased to a smaller degree than the saturated fatty acids. Increased supplementation with linoleic acid resulted in an elevated pentane production when the vitamin E concentration of the diet was low. The α-tocopherol concentration of total liver and microsomes were not influenced by increased supplementation of linoleic acid, however, the monoenoic fatty acid content of the microsomes was reduced.