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1.
Vitamin E isomers are important antioxidants, but their variation is poorly documented in pseduocereal grains such as amaranths.
Using normal-phase, high-performance liquid chromatography with fluorescence detection, seeds of thirteen amaranth (Amaranthus cruentus L.,A. hypochondriacus L.) accessions were surveyed for the composition of tocols. The most common tocols found were α-tocopherol (2.97 to 15.65
mg/kg seed) and β-tocotrienol (5.92 to 11.47 mg/kg seed) and γ-tocotrienol (0.95 to 8.69 mg/kg seed), while someA. cruentus accessions contained δ-tocotrienol (0.01 to 0.42 mg/kg seed). This is the first report of tocotrienols in amaranths.Amaranthus cruentus grain-types of Mesoamerican origin had significantly (P≤0.01) greater levels of four tocols than didA. cruentus African vegetable-types. Unlike many cereal grains, amaranths have significant amounts of both β- and γ-tocotrienols; however,
β-tocopherol was not detected in any of the amaranths. Using multiple linear regressions, α-tocopherol variation of both species
and types was consistently explained by variation in tocols other than α-tocopherol. On the whole, fresh amaranth samples
of both species tended to have higher levels of tocotrienols than samples stored for two years. Storage effects on amaranth
tocol composition are suspected. 相似文献
2.
Chunyang Wang Jing Ning Padmanaban G. Krishnan Duane P. Matthees 《Journal of the American Oil Chemists' Society》1998,75(5):609-613
Vitamin E is a natural antioxidant that plays significant roles in food preservation and disease prevention. There are eight
naturally occurring vitamin E isomers (tocols): α-, β-, γ-, and δ-tocopherols and α-, β-, γ-, and δ-tocotrienols. Corn oil
is a major source of vitamin E. Most of the corn oil produced in the United States is a co-product of corn wet-milling. There
is limited knowledge about the effects of corn wet-milling on the retention of these vitamin E isomers. A high-performance
liquid chromatography method was developed for simultaneous determinations of tocols in steeped corn samples. Effects of steeping
conditions (steeping time and SO2 concentration) on retention of tocols in corn were investigated. α-Tocopherol, γ-tocopherol, α-tocotrienol, and γ-tocotrienol
are the predominant vitamin E isomers in the corn variety used in the study. Steeping conditions had little effect on the
concentration of α-tocopherol and α-tocotrienol. However, a higher concentration of SO2 and a shorter steeping time gave a slightly higher γ-tocotrienol content and lower γ-tocopherol content. Corn kernels steeped
in a vitamin C solution had a much higher concentration of the tocols than those steeped in SO2 solution. 相似文献
3.
Tocopherols can exhibit opposite effects in aqueous media on linoleic acid autoxidation rate. The effect which was observed
depended on tocopherol concentration and on the tocopherol itself. At 0.05 mole of tocopherol per mole of linoleic acid, α-tocopherol
was prooxidant while in similar conditions, δ-tocopherol was anti-oxidant as well as γ-tocopherol. However, this latter one
exhibited a slight antioxidant activity. When tocopherol concentration decreased (twice as weak), α-tocopherol still exhibited
the same pro-oxidant activity, while the antioxidant effect of γ and δ tocopherols was increased. The study of tocopherol
stability by HPLC has shown that tocopherol oxidation increased in order δ < γ < α. There was a relationship between the ability
for a tocopherol to be easily oxidized by air and its prooxidant activity. Tocopherol oxidation would enhance the formation
of a perhydroxyl radical ([·OOH] or one of this type [O20=, ·OH]) which was responsible for the prooxidant effect. 相似文献
4.
J. P. Koskas J. Cillard P. Cillard 《Journal of the American Oil Chemists' Society》1984,61(9):1466-1469
The autoxidation of linoleic acid dispersed in an aqueous media and the effect of α-, γ- and δ-tocopherols were studied. The
quantitative analysis of the hydroperoxide isomers (13-cis,trans; 13-trans,trans; 9-trans,cis; 9-trans,trans) by direct high-performance liquid chromatography exhibited a prooxidant activity of α-tocopherol at high concentration (3.8%
by weight of linoleic acid). On the other hand, α-tocopherol at lower concentrations (0.38 and 0.038%) and γ- and δ-tocopherols
at high concentration (3.8%) were antioxidant. Furthermore, the addition of tocopherols modified the distribution of the geometrical
isomers. The formation of thetrans,trans hydroperoxide isomers was completely inhibited by the highest concentration of the three tocopherols independently of their
antioxidant or prooxidant activity and only delayed by the lower concentrations of α-tocopherol. The addition of tocopherols
to hydroperoxide isomers reduced the decomposition rate of these isomers in the order α-tocopherol < γ-tocopherol < δ-tocopherol
for thecis,trans hydroperoxide isomer and α-tocopherol ≪ γ-tocopherol ⋍ δ-tocopherol for thetrans,trans hydroperoxide isomer. With these hydroperoxides, as during linoleic acid autoxidation, α-tocopherol was completely oxidized
whatever its initial concentration, while γ-tocopherol underwent partial oxidation and δ-tocopherol was practically unchanged. 相似文献
5.
The biologic availability of two kinds of tocomonoenols, marine-derived tocopherol (MDT) and α-tocomonoenol, was investigated
in ICR mice. Vitamin E-deficient ICR mice were fed MDT and α-tocomonoenol together with α-tocopherol, β-tocopherol, γ-tocopherol,
and δ-tocopherol, and storage in liver, spleen, lung, and brain was quantified using reverse-phase high-performance liquid
chromatography. The vitamin E relative biologic availability (VE-RBA) in liver was 100 for α-tocopherol, 26 ± 3 for β-tocopherol,
4 ± 2 for γ-tocopherol, not detected for δ-tocopherol, 49 ± 6 for MDT, and 30 ± 7 for α-tocomonoenol. The VE-RBA in brain
was 100 for α-tocopherol, 5 ± 2 for β-tocopherol, not detected for γ-tocopherol and δ-tocopherol, 8 ± 1 for MDT, and 4 ± 1
for α-tocomonoenol. Tocopherols and tocomonoenols did not accumulate in the spleen or lung. MDT and α-tocomonoenol had high
VE-RBA values. The VE-RBA value for MDT was much higher than that for β-tocopherol. 相似文献
6.
Tocopherols were found to be the principal natural antioxidants in biodiesel grade fatty acid methyl esters. The stabilising
effect of α-, γ- and δ- tocopherols from 250 to 2,000 mg/kg was evaluated by thermal and accelerated storage induction times
based on rapid viscosity increase, in sunflower (SME), recycled vegetable oil (RVOME), rapeseed (RME) and tallow (TME) methyl
esters. Both induction times showed that stabilising effect is of the order of δ- > γ- > α-tocopherol, and that the stabilising
effect increased with concentration. The correlation between the two induction times however was poor, which is probably due
to the fact that the time they correspond to two different stages of oxidation. Tocopherols were found to stabilise methyl
esters by reducing the rate of peroxide formation while present. The deactivation rates of tocopherols increased with unsaturation
of the particular methyl ester and in the present work they were of the order of SME > RME > RVOME > TME. While α-tocopherol
was found to be a relatively weak antioxidants, both γ- and δ- tocopherols increased induction times significantly and should
be added to methyl esters without natural antioxidants. 相似文献
7.
The prooxidant property of inorganic chromium compounds was determined in methyl linoleate free from natural antioxidants
and metals. Prooxidant properties of inorganic chromium compounds appeared in order of sodium chromate > chromium (VI)-oxide
> chromium chloride > potassium chromate > chromium (III)-oxide > potassium dichomate. In comparison with the control, additions
of chromium compounds induced different amounts of autoxidation products derived from methyl linoleate, such as small amounts
of hydroperoxides and conjugated dienes and large amounts of hydroxy groups,α,β,γ,δ-unsaturated carbonyls, isolatedtrans double bonds, polymers, and free radicals. From these analytical data, the catalysis of chromium compounds in the autoxidation
of methyl linoleate seemed to be based on their abilities of abstracting a hydrogen from methyl linoleate and decomposing
hydroperoxides derived from the autoxidation of methyl linoleate. 相似文献
8.
Antioxidant effects of d-tocopherols at different concentrations in oils during microwave heating 总被引:1,自引:0,他引:1
Hiromi Yoshida Goro Kajimoto Shiuji Emura 《Journal of the American Oil Chemists' Society》1993,70(10):989-995
The effects of d-tocopherols at different concentrations (50 to 1000 ppm) on the oxidative stability of ethyl linoleate and
tocopherol-stripped oils were investigated under microwave heating conditions. Purified substrate oils were prepared by aluminum
oxide column chromatography. After the addition of tocopherols (α-, β-, γ- or δ-) to the oils, peroxide, carbonyl andp-anisidine values were measured in the samples after heating in a microwave oven. Further, the residual amount of tocopherol
homologues in the oils after heating was determined by high-performance liquid chromatography for evaluation of their effects
at different concentrations on oxidative deterioration. Microwave heating resulted in some acceleration in the oxidation of
the purified substrate oils. Optimum concentrations of tocopherols required to increase oxidative stability were 100 ppm for
α-, 150–200 ppm for β- or γ- and 500 ppm for δ-tocopherol, respectively. The antioxidant effect of tocopherols decreased in
the order α>β ≒ γ>δ at each level, in all substrates. Therefore, α-tocopherol was consumed first, followed by β- or γ-tocopherol,
and δ-tocopherol was consumed more slowly. The tocopherols had no further significant antioxidant activity (P>0.05) at concentrations higher than 500 ppm. 相似文献
9.
Antiproliferative and apoptotic effects of tocopherols and tocotrienols on normal mouse mammary epithelial cells 总被引:4,自引:3,他引:1
Studies were conducted to determine the comparative effects of tocopherols and tocotrienols on normal mammary epithelial cell
growth and viability. Cells isolated from midpregnant BALB/c mice were grown within collagen gels and maintained on serum-free
media. Treatment with 0–120 μM α-and γ-tocopherol had no effect, whereas 12.5–100 m μM tocotrienol-rich fraction of palm oil
(TRF), 100–120 μM δ-tocopherol, 50–60 μM α-tocotrienol, and 8–14 μM γ- or δ-tocotrienol significantly inhibited cell growth
in a dose-responsive manner. In acute studies, 24-h exposure to 0–250 μM α-, γ-, and δ-tocopherol had no effect, whereas similar
treatment with 100–250 μM TRF, 140–250 μM α-, 25–100 μM γ- or δ-tocotrienol significantly reduced cell viability. Growth-inhibitory
doses of TRF, δ-tocopherol, and a-, γ-, and δ-tocotrienol were shown to induce apoptosis in these cells, as indicated by DNA
fragmentation. Results also showed that mammary epithelial cells more easily or preferentially took up tocotrienols as compared
to tocopherols, suggesting that at least part of the reason tocotrienols display greater biopotency than tocopherols is because
of greater cellular accumulation. In summary, these findings suggest that the highly biopotent γ- and δ-tocotrienol isoforms
may play a physiological role in modulating normal mammary gland growth, function, and remodeling. 相似文献
10.
O. Podlaha Å. Eriksson B. Toregård 《Journal of the American Oil Chemists' Society》1978,55(6):530-532
The polarographic behavior of α-, γ-, and δ-tocopherols was studied according to the proposed official IUPAC method for tocopherol
determination in vegetable oils and fats. Each of the tocopherols had a different polarographic response; however, the tocotrienols
had the same half-wave potentials and probably also the same polarographic response as the corresponding tocopherols. Additives
previously investigated plus several others were examined for possible interference. The results by polarography and a new
high performance liquid chromatography (HPLC) method were compared. The analysis by t-test at 99% significance level showed
no differences for the determinations of α-tocopherol, but the results for three of the γ-tocopherol results were less consistent
under the same conditions. The results for the determination of δ-tocopherol were below the detection limit for polarography
and could not be statistically evaluated. The polarographic method investigated was found to be uncomplicated and therefore
suitable for routine work. However, when using the method, one has to take into account possible interference by additives
and the limitations due to the lack of separation of β- from γ-tocopherol and/or the interference of tocotrienols with the corresponding tocopherol peaks. From this aspect the HPLC
method gives better resolution. 相似文献
11.
Marina Heinonen Katri Haila Anna-Maija Lampi Vieno Piironen 《Journal of the American Oil Chemists' Society》1997,74(9):1047-1052
The effects of low concentrations of β-carotene, α-, and γ-tocopherol were evaluated on autoxidation of 10% oil-in-water emulsions
of rapeseed oil triacylglycerols. At concentrations of 0.45, 2, and 20 μg/g, β-carotene was a prooxidant, based on the formation
of lipid hydroperoxides, hexanal, or 2-heptenal. In this emulsion, 1.5, 3, and 30 μg/g of γ-tocopherol, as well as 1.5 μg/g
of α-tocopherol, acted as antioxidants and inhibited both the formation and decomposition of lipid hydroperoxides. Moreover,
at a level of 1.5 μg/g, γ-tocopherol was more effective as an antioxidant than α-tocopherol. At levels of 0.5 μg/g, both α-
and γ-tocopherol significantly inhibited the formation of hexanal but not the formation of lipid hydroperoxides. Oxidation
was effectively retarded by combinations of 2 μg/g β-carotene and 1.5 μg/g γ- or α-tocopherol. The combination of β-carotene
and α-tocopherol was significantly better in retarding oxidation than α-tocopherol alone. While γ-tocopherol was an effective
antioxidant, a synergistic effect between β-carotene and γ-tocopherol could not be shown. The results indicate that there
is a need to protect β-carotene from oxidative destruction by employing antioxidants, such as α- and γ-tocopherol, should
β-carotene be used in fat emulsions. 相似文献
12.
John K. G. Kramer Lisa Blais Robert C. Fouchard Roman A. Melnyk Krishna M. R. Kallury 《Lipids》1997,32(3):323-330
This paper describes a simple method for the analysis of tocopherols in tissues by which frozen tissues −70°C were pulverized
at dry ice temperatures (−70°C) and immediately extracted with hexane. There was no need to remove the coeluting lipids from
tissues by saponification, since at that level of neutral lipids in the sample, there was no reduction in fluorescence response.
For the analysis of oil, in which large amounts of neutral lipids were coextracted, a 20% reduction of fluorescence response
was observed, but the response was equal for all tocopherol forms, and was appropriately corrected. Saponification was used
only when tocopherol esters were present, and only after an initial hexane extraction to remove the free tocopherols in order
to avoid their loss by saponification, particularly non α-tocopherol and tocotrienols. All the tocopherols and tocotrienols
were separated on a normal-phase diol (epoxide) column that gave consistent and reproducible results, without the disadvantages
of nonreproducibility with silica columns, or the lack of separation with reversed-phase columns. The tocopherols were quantitated
by using a tocopherol form not present in the sample as an internal tocopherol standard, or using an external tocopherol standard
if all forms were present, or when the sample was saponified. Piglet heart and liver samples showed the presence of mainly
α-tocopherol, with minor amounts of β- and γ-tocopherol and α-tocotrienol, but no δ-tocopherol. Only small amounts of tocopherol
esters were present in the liver but not in the heart. 相似文献
13.
James C. Ewing John P. Cosgrove David H. Giamalva Daniel F. Church William A. Pryor 《Lipids》1989,24(7):609-615
Allylbenzene ozonide (ABO), a model for polyunsaturated fatty acid (PUFA) ozonides, initiates the autoxidation of methyl linoleate
(18∶2 ME) at 37°C under 760 torr of oxygen. This process is inhibited by d-α-tocopherol (α-T) and 2,6-di-ert-butyl-4-methylphenol (BHT). The autoxidation was followed by the appearance of conjugated diene (CD), as well as by oxygen-uptake.
The rates of autoxidation are proportional to the square root of ABO concentration, implying that the usual free radical autoxidation
rate law is obeyed. Activation parameters for the thermal decomposition of ABO were determined under N2 in the presence of radical scavengers and found to be Ea=28.2 ±0.3 kcal mol−1 and log A=13.6±0.2; kd (37°C) is calculated to be (5.1±0.3)×10−7 sec−1. Autoxidation data are also reported for ozonides of 18∶2 ME and methyl oleate (18∶1 ME). 相似文献
14.
Rapid method for the quantitative determination of individual tocopherols in oils and fats 总被引:1,自引:0,他引:1
Wolfgang Müller-Mulot 《Journal of the American Oil Chemists' Society》1976,53(12):732-736
Oils and fats are frozen two times from acetone solution at -80 C under protection by ascorbyl palmitate. Tocopherols (T)
and tocotrienols (T3) present in the filtered extract are separated into their homologues by one-dimensional thin layer chromatography on precoated
silica gel plates in the n-hexane/ethyl acetate system 92.5:7.5. Complete separation of the positional isomers β-T and γ-T
is accomplished as well, whereas β-T3 and γ-T are assumed to form identical bands. Suitable spray- and detection systems including new found coloring ones are
described for the qualitative estimation of the chromatograms. The content of individual tocopherols (T and T3) of 24 commercial vegetable oils is quantitatively determined using the Emmerie-Engel procedure. 相似文献
15.
Previous reports showed that vitamin E in palm oil consists of various isomers of tocopherols and tocotrienols [α-tocopherol
(α−T), α-tocotrienol, γ-tocopherol, γ-tocotrienol, and δ-tocotrienol), and this is normally analyzed using silica column HPLC
with fluorescence detection. In this study, an HPLC-fluorescence method using a C30 silica stationary phase was developed to separate and analyze the vitamin E isomers present in palm oil. In addition, an
α-tocomonoenol (α−T1) isomer was quantified and characterized by MS and NMR. α−T1 constitutes about 3–4% (40±5 ppm) of vitamin E in crude palm oil (CPO) and is found in the phytonutrient concentrate (350±10
ppm) from palm oil, whereas its concentration in palm fiber oil (PFO) is about 11% (430±6 ppm). The relative content of each
individual vitamin E isomer before and after interesterification/transesterification of CPO to CPO methyl esters, followed
by vacuum distillation of CPO methyl esters to yield the residue, remained the same except for α−T and γ−T3. Whereas α−T constitutes about 36% of the total vitamin E in CPO, it is present at a level of 10% in the phytonutrient concentrate.
On the other hand, the composition of γ−T3 increases from 31% in CPO to 60% in the phytonutrient concentrate. Vitamin is present at 1160±43 ppm, and its concentrations
in PFO and the phytonutrient concentrate are 4,040±41 and 13,780±65 ppm, respectively. The separation and quantification of
α−T1 in palm oil will lead to more in-depth knowledge of the occurrence of vitamin E in palm oil. 相似文献
16.
The chemistry and antioxidant properties of tocopherols and tocotrienols 总被引:36,自引:3,他引:36
This article is a review of the fundamental chemistry of the tocopherols and tocotrienols relevant to their antioxidant action.
Despite the general agreement that α-tocopherol is the most efficient antioxidant and vitamin E homologuein vivo, there was always a considerable discrepancy in its “absolute” and “relative” antioxidant effectivenessin vitro, especially when compared to γ-tocopherol. Many chemical, physical, biochemical, physicochemical, and other factors seem
responsible for the observed discrepancy between the relative antioxidant potencies of the tocopherolsin vivo andin vitro. This paper aims at highlighting some possible reasons for the observed differences between the tocopherols (α-, β-, γ-,
and δ-) in relation to their interactions with the important chemical species involved in lipid peroxidation, specifically
trace metal ions, singlet oxygen, nitrogen oxides, and antioxidant synergists. Although literature reports related to the
chemistry of the tocotrienols are quite meager, they also were included in the discussion in virtue of their structural and
functional resemblance to the tocopherols. 相似文献
17.
α-Tocopherol and methyl (9Z, 11E)-(S)-13-hydroperoxy-9, 11-octadecadienoate (13-MeLOOH) were allowed to stand at 100°C in bulk phase. The products were isolated
and identified as methyl 13-hydroxyoctadecadienoate (1), stereoisomers of methyl 9,11,13-octadecatrienoate (2), methyl 13-oxo-9, 11-octadecadienoate (3), epoxy dimers of methyl linoleate with an ether bond (4), a mixture of methyl (E)-12, 13-epoxy-9-(α-tocopheroxy)-10-octadecenoates and methyl (E)-12, 13-epoxy-9-(α-tocopheroxy)-11-(α-tocopheroxy)-9-octadecenoates (5), a mixture of methyl 9-(α-tocopheroxy)-10,12-octadecadienoates and methyl 13-(α-tocopheroxy)-9, 11-octadecadienoates (6), α-tocopherol spirodiene dimer (7), and α-tocopherol trimer (8). α-Tocopherol and 13-MeLOOH were dissolved in methyl myristate, and the thermal decomposition rate and the distributions
of reaction products formed from α-tocopherol and 13-MeLOOH were analyzed. α-Tocopherol disappeared during the first 20 min,
and the main products of α-tocopherol were 5 and 6 with the accumulation of 1–4 which were the products of 13-MeLOOH. The results indicate that the alkyl and alkoxyl radicals from the thermal decomposition
of 13-MeLOOH could be trapped by α-tocopherol to produce 5 and 6. The reaction products of α-tocopherol during the thermal oxidation of methyl linoleate were compounds 6 and 7. Since the radical flux during the autoxidation might be low, the excess α-tocopheroxyl radical reacted with each other to
form 7. 相似文献
18.
Nucleic acids acted as synergists with tocopherols in inhibiting the oxidation of methyl linoleate. DNA and RNA enhanced the
activity of tocopherols to different extents in the order α->γ->δ-tocopherol. Nucleic acids decreased the rates of consumption
of tocopherol in the presence of oxi-dizing methyl linoleate. Nucleic acids also decreased the rate of oxidation of tocopherols
by PbO2. The synergistic effect of nucleic acids seemed to be caused by hydrogen bond formation with tocopherols which protected
toco-pherols from direct air oxidation. 相似文献
19.
α-Tocopherol was reacted with alkyl and alkylperoxyl radicals at 37°C in bulk phase. The lipid-free radicals were generated
by the reaction of methyl linoleate with the free radical initiator, 2,2′-azobis(2,4-dimethylvaleronitrile) (AMVN) under air-insufficient conditions. The products were isolated by high-performance liquid
chromatography. Their structures were identified as 2-(α-tocopheroxy)-2,4-dimethylvaleronitrile (1), a mixture of methyl 9-(8a-peroxy-α-tocopherone)-10(E),12(Z)-octadecadienoate and methyl 13-(8a-peroxy-α-tocopherone)-9(Z),11(E)-octadecadienoate (2), methyl 9-(α-tocopheroxy)-10(E),12(Z)-octadecadienoate (3a), methyl 13-(α-tocopheroxy)-9(Z),11(E)-octadecadienoate (3b), α-tocopherol spirodiene dimer (4) and α-tocopherol trimer (5). When methyl linoleate containing α-tocopherol
was oxidized with AMVN under airsufficient conditions, the main products were 8a-alkyl-peroxy-α-tocopherones (2). In addition
to these compounds, 6-O-alkyl-α-tocopherols (1, 3a and 3b) were formed when the reaction was carried out under air-insufficient conditions. The results
indicate that α-tocopherol can react with both alkyl and alkylperoxyl radicals during the autoxidation of polyunsaturated
lipids. 相似文献
20.
S. H. Goh N. F. Hew A. S. H. Ong Y. M. Choo S. Brumby 《Journal of the American Oil Chemists' Society》1990,67(4):250-254
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. 相似文献