共查询到20条相似文献,搜索用时 15 毫秒
1.
During national and regional health surveys, done from 1984–1995 in Germany, consumption data for all drugs used by the participants—approximately
18,000 persons—in the last 7 d before the examination were monitored with a detailed drug-usage questionnaire. The groups
examined are representative for the national and regional German inhabitant population aged 25–69 yr. In serum samples of
subsamples of the study participants, all tocopherols were measured by isocratic high-performance liquid chromatography (Si
60 column, fluorescence detection). Consumption data for tocopherol-containing drugs showed that up to 5% of females and up
to 3% of males of the study population used those drugs. During the study period, the serum content of α-tocopherol (mean
values ± SD) rose from 7.5 ± 2.6 mg/L serum to 11.8 ± 2.8 mg/L serum for nonusers and from 11.9 ± 4.3 mg/L serum to 15.3 ±
4.9 mg/L serum in tocopherol-drug users. Throughout all studies, it could be shown that β- and γ-tocopherol were heavily reduced
in those persons taking daily doses ≥50 mg α-tocopherol. The reduction of the two tocopherols is dose-dependent and especially
pronounced in females using high-dose α-tocopherol drugs. Owing to the emerging evidence of the physiological importance concerning
the balance of the different tocopherols in biological systems, the possible benefits of using natural tocopherol mixtures
from plant origin instead of pure RRR-α-tocopherol, gained from permethylation procedures, as vitamin supplements in human nutrition should be considered. 相似文献
2.
G. William Chase Jr. Casimir C. Akoh Ronald R. Eitenmiller 《Journal of the American Oil Chemists' Society》1994,71(8):877-880
A comparison of the responses of an evaporative light-scattering detector (ELSD) and a fluorescence detector for tocopherols
in vegetable oils by high-performance liquid chromatography is presented. The tocopherols were separated from acylglycerols
by gel-permeation chromatography (GPC). The tocopherol fraction was collected off a set of four GPC columns with a mobile
phase of methylene chloride before separation on a normal-phase silica column with a mobile phase of hexane/isopropanol, 99.7∶0.3
(vol/vol). An internal standard of 5,7 dimethyltocol, which was detected by both the ELSD and fluorescence detector, was used
to obtain quantitative data. The fluorescence detector was ten times more sensitive than the ELSD. γ-Tocopherol was the major
tocopherol detected in the vegetable oils studied and ranged from 24.1–93.3 mg/100 g. The amounts of tocopherols found in
the vegetable oils agreed favorably with the literature values. 相似文献
3.
J. C. Evans D. R. Kodali P. B. Addis 《Journal of the American Oil Chemists' Society》2002,79(1):47-51
The optimal concentration for tocopherols to inhibit soybean oil oxidation was determined for individual tocopherols (α-,
γ-, and δ-tocopherol) and for the natural soybean oil tocopherol mixture (tocopherol ratio of 1∶13∶5 for α-, γ-, and δ-tocopherol,
respectively). The concentration of the individual tocopherols influenced oil oxidation rates, and the optimal concentrations
were unique for each tocopherol. For example, the optimal concentrations for α-tocopherol and γ-tocopherol were ∼100 and ∼300
ppm, respectively, whereas δ-tocopherol did not exhibit a distinct concentration optimum at the levels studied (P<0.05). The optimal concentration for the natural tocopherol mixture ranged between 340 and 660 ppm tocopherols (P<0.05). The antioxidant activity of the tocopherols diminished when the tocopherol levels exceeded their optimal concentrations.
Above their optimal concentrations, the individual tocopherols and the tocopherol mixture exhibited prooxidation behavior
that was more pronounced with increasing temperature from 40 to 60°C (P<0.05). A comparison of the antioxidant activity of the individual tocopherols at their optimal concentrations revealed that
α-tocopherol (∼100 ppm) was 3–5 times more potent than γ-tocopherol (∼300 ppm) and 16–32 times more potent than δ-tocopherol
(∼1900 ppm). 相似文献
4.
A method to analyze cholesterol and 10 of its oxidation products, ranging from the weakly polar cholest-4-ene-3,6-dione to
moderately polar cholest-5-ene-3β,7α-diol, in a single run is described. The separation was achieved by normal-phase gradient
high-performance liquid chromatography with an evaporative light-scattering detector. This universal mass detector does not
detect changes in solvent composition; this makes it possible to employ gradients, an essential technique whenever a wide
range of compounds with diverse characteristics is to be separated. Standards at concentrations from 0.1–1.0 μg were separated
within 37 min on an alumina/silica column with a gradient elution system that contained dichloromethane, acetonitrile, and
water. 相似文献
5.
Anna-Maija Lampi Leena Kataja Afaf Kamal-Eldin Piironen Vieno 《Journal of the American Oil Chemists' Society》1999,76(6):749-755
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. 相似文献
6.
Oxidation kinetics of β-carotene in oleic acid solvent with addition of an antioxidant, α-tocopherol
Shibasaki-Kitakawa Naomi Kato Hideto Takahashi Atsushi Yonemoto Toshikuni 《Journal of the American Oil Chemists' Society》2004,81(4):389-394
Oxidation experiments with β-carotene were performed in oleic acid solvent with addition of an antioxidant, α-tocopherol.
A kinetic model was proposed based on a reaction mechanism consisting of the oxidation of β-carotene, oleic acid, and α-tocopherol;
the antioxidation reactions of β-carotene and oleic acid by α-tocopherol; the cross-reaction of β-carotene and oleic acid;
and the radical-exchange reaction of β-carotene and α-tocopherol. The model quantitatively described the oxidation behavior
of β-carotene over a wide range of temperatures, oxygen compositions, and initial antioxidant concentrations. The model simulated
well the time over which β-carotene was almost totally consumed under practical storage conditions at room temperature in
air. 相似文献
7.
Kyoichi Osada Amir Ravandi Arnis Kuksis 《Journal of the American Oil Chemists' Society》1999,76(7):863-871
Extensive evidence of the deleterious biological effects of oxidized 5-cholesten-3β-ol (cholesterol) derivatives has led to
great interest in their detection. We observed that known oxidized cholesterol derivatives can be rapidly quantitated by combining
reversed-phase high-performance liquid chromatography (HPLC) with ultraviolet (UV) absorption and evaporative laser light-scattering
(ELSD) detection. Using a 20 × 0.46 cm C18 HPLC column and methanol/acetonitrile (60:40, vol/vol) as the mobile phase at 1.0
mL/min, 10 species of oxidized cholesterol derivative were measured by UV (205, 234, and 280 nm) while 5-cholestan-5α,6α-epoxy-3β-ol
(5α-epoxycholesterol), 5-cholestan-5β,6β-epoxy-3β-ol (5β-epoxycholesterol), and 5-cholestan-3β,5α,6β-triol (cholestanetriol)
were detected by only ELSD. The minimal limits of detection ranged from 100 to 500 ng depending on sterol and detector. The
response was linear in the range 0–1000 or 0–2000 ng depending on detector. These oxidized cholesterol derivatives were also
identified by HPLC/mass spectrometry analysis combined with UV detector. Heated tallow contained cholestanetriol, 5-cholesten-3β,7α-diol
(7α-hydroxycholesterol), 5-cholesten-3β,7β-diol (7β-hydroxycholesterol), 5-cholesten-3β-ol-7-one (7-ketocholesterol), 5α-
and 5β-epoxycholesterols under the developed analysis condition. Photooxidized cholesterol had cholestanetriol, 7α- and 7β-hydroxycholesterols
and 3,5-cholestadien-7-one. On the other hand, 7α- and 7β-hydroxycholesterols, 7-ketocholesterol, 5α- and 5β-epoxycholesterols
and 3,5-cholestadien-7-one were observed in copper-oxidized low-density lipoprotein. Thus, this developed HPLC analysis method
could be applied to identification of oxidized cholesterol derivatives in food and biological specimen. 相似文献
8.
R. Ap. Ferrari W. Esteves K. D. Mukherjee 《Journal of the American Oil Chemists' Society》1997,74(2):93-96
Steryl ester content of refined and interesterified corn, soybean, and rapeseed oils has been measured via clean-up on a short silica gel column, followed by high performance liquid chromatography with evaporative light-scattering
mass detector. Chemical interesterification, catalyzed by sodium methoxide, led to random positional distribution of fatty
acids in triacylglycerols and some increase in the steryl ester content of all three oils. Enzymatic interesterification,
catalyzed by the immobilized lipase from Rhizomucor miehei (Lipozyme), resulted in a distinct reduction in steryl ester content, but essentially no alteration in positional distribution
of fatty acids in triacylglycerols occurred. Formation of steryl esters during chemical and enzymatic interesterification
was also examined by radioactive tracer technique with [4-14C]β-sitosterol added as marker to refined rapeseed oil and measurement of the radioactive steryl esters formed. Chemical interesterification
of rapeseed oil resulted in moderate formation (10% of total radioactivity) of radioactive β-sitosteryl esters. Enzymatic
interesterification of the oil, catalyzed by Lipozyme, led to little formation of radioactive β-sitosteryl esters, whereas
with the lipase from Candida cylindracea high proportions (>90% of total radioactivity) of 14C-labeled β-sitosteryl esters were formed.
Part of doctoral thesis of Roseli Ap. Ferrari to be submitted to Faculdade de Engenharia de Alimentos, Universidade de Campinas,
Campinas, Brazil. 相似文献
9.
N. V. Yanishlieva E. M. Marinova V. G. Raneva V. Partali H. -R. Sliwka 《Journal of the American Oil Chemists' Society》2001,78(6):641-644
The oxidation kinetics of sunflower oil (SO) and pure triacylglycerols of sunflower oil (TGSO) in the presence of different
concentrations (0.0008–0.02%, 1.9–32.7×10−5 M) of β-apo-8′-carotenoic acid (CA), ethyl β-apo-8′-carotenoate (EC), and β-apo-8′-carotenoylglycerol (CG) were studied.
The process was performed at high (kinetic regime) and low (diffusion regime) oxygen concentrations at room temperature and
at 100°C and in the dark and in daylight. CA, EC, and CG were not antioxidants in TGSO systems. However, the carotenoid derivatives,
especially CA, increased the stability of tocopherol-containing SO at room temperature and in daylight. The stabilization
effect was more evident in a kinetic regime of oxidation. The synergism between the carotenoids and tocopherols was characterized
by the increase of the stabilization factor F and activity A. F and A were highest for CA (F=1.2–5.5, A=2.4–78.6), followed by EC (F=1.2–3.5, A=1.7–14.6) and CG (F=1.1–2.1, A=1.6–5.5) in the kinetic regime for SO exposed to daylight at room temperature.
Presented at the 91st AOCS Annual Meeting & Expo, April 25–28, 2000, San Diego, California. 相似文献
10.
The influence of carotenoids and tocopherols on the stability of safflower seed oil during heat-catalyzed oxidation 总被引:2,自引:2,他引:0
L. K. Henry G. L. Catignani S. J. Schwartz 《Journal of the American Oil Chemists' Society》1998,75(10):1399-1402
The stability and antioxidant effects of carotenoids and tocopherols in safflower seed oil were evaluated under thermal (75°C)
and oxidative conditions and the oxidative stability index (OSI) determined. The antioxidant capability of butylated hydroxytoluene
(BHT) was also compared with that of β-carotene in a model system. Lycopene and β-carotene (1 to 2000 ppm) were heated (75°C)
and exposed to air (2.5 psi) in an oxidative stability instrument. β-Carotene had no antioxidant effect at concentrations
below 500 ppm, because it did not alter the induction time. Lycopene increased the induction time only slightly at low concentrations.
However, at concentrations greater than 500 ppm, both β-carotene and lycopene acted as prooxidants, significantly decreasing
the induction period. At the highest concentration, 2000 ppm, lycopene was more prooxidative than β-carotene. α- and γ-Tocopherol
(concentration, 1000 ppm) delayed the induction time by 16 and 26 h, respectively. There was no cooperative interaction between
α-tocopherol and β-carotene in delaying the onset of oxidation. Furthermore, BHT was significantly more antioxidative than
β-carotene. Thus, under thermal and oxidative conditions, β-carotene could not delay the onset of oxidation. The tocopherols
and BHT were effective in suppressing the onset of oxidation, as determined by the oxidative stability measurement. 相似文献
11.
Ihsan Karabulut Ali Topcu Canan Akmil-Basar Yunus Onal Anna-Maija Lampi 《Journal of the American Oil Chemists' Society》2008,85(3):213-219
It is difficult to remove β-carotene from oils with alumina-column chromatography, because β-carotene is even less-polar than
triacylglycerols (TAGs) are. The objective of this study was to obtain butter oil TAGs free from β-carotene and antioxidants
via sequential treatments with activated carbon (AC) adsorption and alumina column chromatography. The AC used was prepared
from waste apricots. The effects of AC dosages, temperatures and time courses on β-carotene adsorption were studied. The Langmuir
and Freundlich isotherms were used to describe the adsorption of β-carotene onto AC, and it was found to be more consistent
with the Freundlich isotherm with a higher R
2 value (0.9784). Adsorption kinetics of β-carotene was analyzed by pseudo-first order and pseudo-second order models. The
pseudo-second order model was found to explain the kinetics of β-carotene adsorption more effectively (R
2 = 0.9882). The highest β-carotene reduction was achieved (from 31.9 to 1.84 mg/kg) at an AC dosage of 10 wt%, temperature
of 50 °C, and adsorption time of 240 min. A considerable amount of α-tocopherol was also adsorbed during the AC treatment.
Remaining portions of α-tocopherol were completely removed with alumina adsorption chromatography. The method described may
be used for purification of vegetable oil TAGs, which will be used as model compounds in model oxidation studies. 相似文献
12.
R. Przybylski D. Klensporf-Pawlik F. Anwar M. Rudzinska 《Journal of the American Oil Chemists' Society》2009,86(6):553-559
The content and composition of fatty acids, sterols, tocopherols, and γ-oryzanol in wild rice (Zizania palustris) grown in North America were compared with those in regular brown rice (Oryza sativa L.). The lipid content of wild rice ranged from 0.7 to 1.1%, compared with 2.7% in regular brown rice. The lipids of wild rice
comprised mainly linoleic (35–37%) and linolenic (20–31%) acids. Other fatty acids included palmitic (14.1–18.4%), stearic
(1.1–1.3%), and oleic (12.8–16.2%). Wild rice lipids contained very large amounts of sterols, ranging from 70 g/kg for a Saskatchewan
sample to 145 g/kg for Minnesota Naturally Grown Lake and River Rice. The main sterols found in an unsaponified fraction were:
campesterol (14–52%), β-sitosterol (19–33%), Δ5-avenasterol (5–12%), and cycloartenol (5–12%). Some of sterols, γ-oryzanols, were present as the phenolic acid esters; the
amount ranged from 459 to 730 mg/kg in wild rice lipids. The largest amounts of tocopherols and tocotrienols, 3682 and 9378 mg/kg,
were observed in North Western Ontario wild rice samples, whereas the lowest were 251 mg/kg in an Athabasca Alberta sample
and 224 mg/kg in regular long-grain brown rice. The α isomer was the most abundant among tocopherols and tocotrienols. The
results of this study showed that wild rice lipids contain large amounts of nutraceuticals with proven positive health effects. 相似文献
13.
There is little information available about phytosterols in canola (Brassica napa L.) oil and the effects of genotype and growing locations from Virginia and the mid-Atlantic region of the United States,
a potential area for the establishment of domestic production to provide edible oil. Our objectives were to characterize the
phytosterols, phospholipids, unsaponifiable matter, and FA in oil from Virginia-grown canola. Among 11 canola genotypes grown
at two locations during 1995–1996 significant variations existed for oil content and FA profiles, but not for contents of
phospholipids, unsaponifiable matter, total phytosterols, campesterol, stigmasterol, and β-sitosterol, Total phytosterol content
in the oil of Virginia-grown canola varied from 0.7 to 0.9% with a mean of 0.8%. This concentration compared favorably with
oil from Canadian canola, which typically contains 0.5 to 1.1% total phytosterols. The mean contents of brassicasterol, campesterol,
stigmasterol, β-sitosterol, Δ5-avenasterol, and Δ7-stigmatenol as percentages of total phytosterols in Virginia-grown canola were: 9.7, 32.0, 0.6, 49.3, 4.99, and 3.5%, respectively.
Growing location did not affect phytosterols in Virginia-grown canola oil but had significant effects on contents of phospholipids,
and saturated (myristic, stearic, and arachidic) and unsaturated (palmitoleic, linoleic, linolenic, eicosenoic, and erucic)
FA. 相似文献
14.
Although the structure of phytosterols is closely related to cholesterol, there is a gap in knowledge concerning the formation
and occurrence of oxidation products from phytosterols. The main objective of this study was to isolate and characterize some
side-chain oxidation products formed after autoxidation of stigmasterol. Another objective was to highlight the difficulties
in the analysis of phytosterol and a mixture of their oxidation products by GC. Pure stigmasterol was oxidized at 120°C for
72 h in an air-ventilated oven. Preparative TLC separated the oxidation products, and the products were characterized with
GC-MS and NMR. In addition to the common ring-structure oxidation compounds, three semipolar oxidation products—24-ethylcholest-5,22-dien-3β,25-diol,
24-ethylcholest-5,22-dien-3β,24-diol, and 24-ethyl-5,22-choladien-3β-ol-24-one—were characterized for the first time by TLC,
GC-MS, and NMR. Moreover, the results of the analysis of a large number of oxidation products from sitosterol, campesterol,
and stigmasterol by capillary column GC indicated that further efforts and optimization are required in this area. 相似文献
15.
Anna-Maija Lampi Afaf Kamal-Eldin 《Journal of the American Oil Chemists' Society》1998,75(12):1699-1703
The antipolymerization effects of α- and γ-tocopherols were compared in model systems composed of purified high-oleic sunflower
triacylglycerols at 180°C. γ-Tocopherol was much more effective as an antipolymerization inhibitor than α-tocopherol, partly
due to lower oxidizability/disappearance. Purified triacylglycerols of sunflower, rapeseed, and high-oleic sunflower oils
were less stable than their nonpurified forms containing tocopherols. Results confirmed that tocopherols per se can act as antipolymerization agents in high-oleic oils at frying temperatures. No synergism was observed when α- and γ-tocopherols
were present together although larger amounts of residuals were left for both tocols. Results suggested that high-oleic/high-γ-tocopherol
oils (such as high-oleic canola and high-oleic soybean oils) may provide better frying oils than high-oleic/high-α-tocopherol
oils (such as high-oleic sunflower oil). 相似文献
16.
Virgin olive oil was photooxidized at 2 and 40°C and at fluorescent light intensities of 0, 620, 2710, and 5340 lux. As expected,
higher fluorescent light intensities induced higher peroxide formation in the oil. The thiobarbituric acid reactive substances
(TBARS) were found to be good indicators of photooxidation during the early stage of the reaction. Pheophytin A and β-carotene
were light- and temperature-sensitive, whereas α-tocopherol and total polyphenols were mostly affected by light. Pheophytin
A functioned as a photosensitizer, resulting in rapid oxidation of the oil. β-Carotene was a strong natural inhibitor of photooxidation
for all light intensities at 2°C, suggesting quenching properties for singlet oxygen. However, β-carotene antioxidant activity
was reduced at 40°C because of its rapid destruction. 相似文献
17.
The effect of the N-linked glycans on structural features and physicochemical functions of soybean β-conglycinin homotrimers 总被引:2,自引:0,他引:2
Nobuyuki Maruyama Mohamad Ramlan Mohamed Salleh Koji Takahashi Kazuhiro Yagasaki Hideyuki Goto Naho Hontani Shuko Nakagawa Shigeru Utsumi 《Journal of the American Oil Chemists' Society》2002,79(2):139-144
β-Conglycinin is a trimeric protein consisting of three subunits, α,α′,and β, which are N-glycosylated. The α and α′ subunits
contain extension regions in addition to core regions common to all subunits. We purified homogeneous trimers consisting of
only α, α′, or β from mutant soybean cultivars containing β-conglycinin lacking one or two subunits: α homotrimers from an
α′-lacking mutant, α′ homotrimers from an α-lacking mutant, and β homotrimers from an α-and α′-lacking mutant. Structural
features and physicochemical functions of the three homotrimers were examined and compared with those of recombinant homotrimers
having no N-linked glycans. The native homotrimers have secondary structures very similar to those of the recombinant ones.
In analogy with the recombinant homotrimers, the native ones exhibit different thermal stabilities from one another (β>α′>α),
and the native α and α′ homotrimers exhibit better solubility, emulsifying ability, and heat-induced association than the
native β homotrimer. Further, the N-linked glycans contribute to solubilities of the three subunits at low ionic strength
(μ=0.08) and to the emulsifying ability of the native β homotrimer. N-Linked glycans also prevent heat-induced associations
of the native α and α′ homotrimers but do not contribute to the secondary structure and the thermal stability of β-conglycinin. 相似文献
18.
Oxidation of β-carotene in an inert solvent, n-decane, in the presence of various concentrations of the antioxidant α-tocopherol was studied. The progress of carotene oxidation
was suppressed as long as the tocopherol remained in the system. A rigorous kinetic model for carotene oxidation in the presence
of an antioxidant was proposed based on a reaction mechanism in which not only the antioxidation but also the co-oxidation
and radical-exchange reaction of tocopherol with carotene were incorporated. The model quantitatively described the oxidation
behavior of carotene over a wide range of temperatures, oxygen compositions, and initial antioxidant concentrations. 相似文献
19.
In this study, we found that transparent gels of β-lactoglobulin (β-LG) were formed by adding different concentrations of
sodium caprate to protein solutions at ambient temperature. We investigated changes in the dynamic viscoelasticity of the
mixture with time at 25°C and found that more than 12% β-LG induced the formation of a viscoelastic gel with a suitable amount
of sodium caprate (for example, 12% β-LG and 3.6% sodium caprate). Furthermore, we analyzed the changes in the secondary structure
of proteins during the gelation step by FHR spectroscopy. Dissociation of the β-LG dimer was first observed just after mixing
with sodium caprate. Furthermore, in the β-LG protein in which the original contents were predominantly β-sheets, intermolecular
β-sheets attributable to aggregation increased with a decrease in the content of intramolecular β-sheets. Sodium caprate-induced
gel was heated at 80°C for 30 min after the gel was formed, and a large increase in the intermolecular β-sheet bands was observed
by heat treatment. These results suggest that the formation of sodium caprate-induced gels of β-LG was accompanied by less
marked changes in the protein conformation than those in heat-induced gels. 相似文献
20.
Myung-Wan Kim Jong-Ho Kim Yoshihiro Sugi Gon Seo 《Korean Journal of Chemical Engineering》2000,17(4):480-483
An MCM-22 zeolite with an Si/Al ratio 13 was found to exhibit higher selectivity to β,β-diisopropylnaphthalene in the alkylation
of isopropylnaphthalene with isopropylalcohol, as compared with other zeolites such as mordenite, Y and beta having similar
Si/Al ratios. This high selectivity is ascribed to the specific pore shape of MCM-22 zeolite. The gradual increase in the
selectivity with reaction time is due to its pore modification by coke deposit. 相似文献