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1.
Analysis of free and esterified sterols in vegetable oils 总被引:2,自引:6,他引:2
T. Verleyen M. Forcades R. Verhe K. Dewettinck A. Huyghebaert W. De Greyt 《Journal of the American Oil Chemists' Society》2002,79(2):117-122
In vegetable oils, phytosterols occur as free sterols or as steryl esters. Few analytical methods report the quantification
of esterified and free sterols in vegetable oils. In this study, esterified and free sterols were separated by silica gel
column chromatography upon elution with n-hexane/ethyl acetate (90∶10 vol/vol) followed by n-hexane/diethyl ether/ethanol (25∶25∶50 by vol). Both fractions were saponified separately and the phytosterol content was
quantified by GC. The analytical method for the analysis of esterified and free sterols had a relative standard deviation
of 1.16% and an accuracy of 93.6–94.1%, which was comparable to the reference method for the total sterol analysis. A large
variation in the content and distribution of the sterol fraction between different vegetable oils can be observed. Corn and
rapeseed oils were very rich in phytosterols, which mainly occurred as steryl esters (56–60%), whereas the majority of the
other vegetable oils (soybean, sunflower, palm oil, etc.) contained a much lower esterified sterol content (25–40%). No difference
in the relative proportion of the individual sterols among crude and refined vegetable oils was observed. 相似文献
2.
M. Tasioula-Margari G. Márquez-Ruíz M. C. Dobarganes 《Journal of the American Oil Chemists' Society》1996,73(11):1579-1584
Precipitates enriched in oligomeric triacylglycerides were separated from thermally oxidized olive residue oil, conventional
and high-oleic sunflower oils, and soybean oil by solvent fractionation in methanol/acetone at 4–5°C for 16 h. Different fractionation
conditions were evaluated in an effort to isolate the oligomeric triacylglycerides (OTG). OTG, formed in frying oils upon
heating at low concentations, were not detectable with conventional methods to determine polymeric compounds. The best conditions
found from the different assays were the following: (i) weight of oil sample-to-solvent volume ratio of 1∶20; and (ii) solvent
system methanol/acetone 10∶90 (vol/vol) for monounsaturated oils and 15∶85 (vol/vol) for polyunsaturated oils. Precipitates,
enriched in oligomers, were formed when heated oils and used frying oils contained more than 27% polar compounds, a value
which is widely accepted as the upper limit for use of frying oils. 相似文献
3.
E. Molina Grima A. Robles Medina A. Giménez Giménez J. A. Sánchez Pérez F. Garcia Camacho J. L. García Sánchez 《Journal of the American Oil Chemists' Society》1994,71(9):955-959
Seven solvent mixtures have been used to extract the lipid fraction of lyophilized biomass ofIsochrysis galbana. Six of them were composed of biocompatible solvents. Each method was carried out under relaxed operating conditions (i.e.,
one hour at room temperature) with extraction in a nitrogen atmosphere to prevent autooxidation and degradation of polyunsaturated
fatty acids (PUFAs). Apart from the well-established Bligh and Dyer method [Can. J. Biochem. Physiol. 37:911 (1959)] (Cl3CH/MeOH/H2O, 1∶2∶0.8, vol/vol/vol), which rendered the highest yield of lipids (93.8%), ethanol (96%) and hexane/ethanol (96%), 1∶2.5
vol/vol produced the best results (84.4 and 79.6%, respectively). To obtain free fatty acids, KOH was added to the solvent
mixtures used to extract the total lipids, except for Cl3CH/MeOH/H2O, and direct saponification was carried out at 60°C for 1 h or at room temperature for 8 h. The highest yields obtained by
direct saponicification were 81% with hexane/ethanol (96%), 1∶2.5, vol/vol and 79.8% with ethanol (96%). Partial yields of
the mainn-3 PUFAs found inI. galbana, stearidonic acid (SA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), were calculated for both extraction methods.
For lipid extraction with ethanol (96%), yields of 91, 82 and 83% were obtained for SA, EPA and DHA, respectively. When direct
saponification was used, hexane/ethanol (96%; 1∶2.5, vol/vol) produced the best yields of (91, 79 and 69% for SA, EPA and
DHA, respectively). 相似文献
4.
We have designed a rapid method for the separation of polyunsaturated fatty acids (PUFA, ≥trienes) from non-PUFA, and for
estimation of total amounts of PUFA in lipids of aquatic organisms. Lipids from thirty-one species, including marine and fresh
water fishes, shell fishes, marine algae, and other aquatic animals, and from terrestrial organisms, were transesterified
with sodium methoxide in methanol. The resulting fatty acid methyl esters were separated by thin-layer chromatography on commercially
available plain silica gel plates with a developing solvent ofn-hexane/ethyl ether/acetic acid (95∶5∶1, by vol). All of the methyl esters from aquatic organisms tested separated into two
spots, whereas those from terrestrial sources, except for linseed oil, showed a single unresolved spot. The upper and lower
spots were scraped separately from the plate, and their fatty acid compositions were determined by gas-liquid chromatography.
The lower spot was composed of PUFA having more than two double bonds, whereas components of the upper spot were saturated,
monoenoic, and the greater part of the dienoic fatty acids. When the spots on the silica gel plate were stained with Coomassie
brilliant blue, the amounts of PUFA in aquatic organisms could be estimated satisfactorily using a scanning densitometer.
Presented in Japanese at the general Meeting of JSSF held in Mie University, Tsu-city, Japan, October 1994. 相似文献
5.
This study reports a facile identification of the molecular species of enantiomeric diacylglycerols by combining chiral phase
high-performance liquid chromatography with positive chemical ionization mass spectrometry. For this purpose the 3,5-dinitrophenylurethane
(DNPU) derivatives ofsn-1,2(2,3)-diacylglycerols are separated on an (R+)-naphthylethylamine polymer column (25 cm × 0.46 cm ID) using an isocratic
solvent system made up of hexane/dichloroethane/acetonitrile (85∶10∶5, by vol) or isooctane/tert-butyl methyl ether/acetonitrile/isopropanol (80∶10∶5∶5, by vol). About 1% of the column effluent (1 mL/min) was admitted
to a quadrupole mass spectrometer (Hewlett-Packard, Palo Alto, CA)via direct liquid inlet interface, and positive chemical ionization spectra were recorded over the range of 200–900 mass units.
The DNPU derivatives of diacylglycerols yield characteristic [M-DNPU]+ and [RCO+74]+ ions for each diacylglycerol species from which the molecular weight and exact pairing of fatty acids can be unequivocally
obtained. The characteristic ions appear to be generated in nearly correct mass proportions as indicated by preliminary quantitative
comparisons.
The abbreviations 14∶0, 16∶1, 18∶2, etc. represent normal chain fatty acids of 14, 16, 18, etc. acyl carbons and 0, 1, 2,
etc. double bonds, respectively; 16∶0–18∶1, etc. represent diacylglycerols containing 16∶0 and 18∶1 fatty acids of unspecified
positional distribution;sn indicates stereospecific numbering of glycerol carbons;sn-1,2-diacylglycerols andsn-2,3-diacylglycerols are enantiomeric diacylglycerols of unspecified fatty acid composition;rac-1,2-diacylglycerols are racemic diacylglycerols representing equal amounts ofsn-1,2-andsn-2,3-enantiomers;sn-1,2(2,3)-diacylglycerols are a mixture ofsn-1,2-andsn-2,3-diacylglycerols of unspecified proportion of enantiomers and unspecified fatty acid compisition and positional distribution;
X-1,3-diacylglycerols are diacylglycerols of unspecified fatty acid composition and reverse isomer content. 相似文献
6.
In the present study we have used statistical experimental design and multivariate optimization to formally optimize a reversed-phase
high-performance liquid chromatography method for the analysis of triacylglycerol molecular species of natural oils. The optimal
conditions found were, on an octadecylsilan-column, from acetonitrile/isooctane (90∶10, vol/vol) to acetonitrile/ethanol/isooctane
(40∶35∶25, by vol), at a column temperature of 50°C and a flowrate of 1.5mL/min using a negative exponential gradient profile.
Several examples of separations of natural seed and animal oils,i.e., soybean oil, rapeseed oil, palm oil, linseed oil, tallow and fish oil, are given. A version of the equivalent carbon number
concept, utilizing the Snyder polarity index, was used to identity the molecular species. 相似文献
7.
A simple, high-performance liquid chromatographic method is described for the separation of tetraenoic, trienoic and dienoic
conjugated fatty acids on a Zorbax ODS reversed-phase column using acetonitrile/tetrahydrofuran (95∶5, vol/vol) at a flow
rate of 1.2 mL/min as mobile phase. Also described is the separation of the isomeric conjugated fatty acids with acetonitrile/water/tetrahydrofuran
(90∶90∶1, by vol) as mobile phase. The simultaneous detection and identification of the separated geometrical isomers in the
eluant was accomplished using photodiode array detection. 相似文献
8.
Milan Čertík Peter Andráši Ján Šajbidor 《Journal of the American Oil Chemists' Society》1996,73(3):357-365
The effect of extraction procedures on the lipid yield and fatty acid composition of total lipid and main lipid structures
(phospholipids, diacylglycerols, triacylglycerols, free fatty acids, and sterol esters) of fungal biomass (Mucor mucedo CCF-1384) containing γ-linolenic acid (GLA) was investigated. Seventeen extraction methods, divided into three groups, were
tested: six with chloroform/methanol, five with hexane/alcohols, and six with common solvents or mixtures. The chloroform/methanol
procedure (2∶1) was selected as standard, where lipid yield (TL/DCW, total lipid per dry cell weight) was 17.8%, considered
to be 100% of lipids present. All chloroform/methanol extractions yielded more than 83% recorvey of lipids. Use of hexane/isopropanol
solvent systems led to a maximum of 75% recovery. The best lipid yield was achieved by a two-step extraction with ethanol
and hexane (120%). Extraction efficiency of the other solvent systems reached a maximum of 73%. Triacylglycerols were the
main structures of lipid isolated; only methanol-extracted lipid contained 58.5% phospholipids. The fatty acid content of
total recovered lipid was variable and depended on both the lipid class composition and the solvent system. GLA concentrations
in total lipids isolated by hexane/alcohol procedures (7.3–10.7%) are comparable with classical chloroform/methanol systems
(6.5–10.0%). The maximal GLA yield was obtained with chloroform/methanol/n-butanol/water/0.1 M ethylenediaminetetraacetic acid (EDTA) (2∶1∶1∶1∶0.1, by vol) and after two-step extraction with ethanol
and hexane (14.3 and 13.7 g GLA/kg DCW, respectively). The highest GLA content was analyzed in the phospholipid fraction (16.1%)
after using chloroform/methanol/n-butanol/water/0.1 M EDTA (2∶1∶1∶1∶0.1, by vol). Remarkably low concentrations of polyunsaturated fatty acids were determined
in the free fatty acid fraction. 相似文献
9.
Glycolipids from edible plant sources were accurately quantified by silica-based, normal-phase high-performance liquid chromatography
using an evaporative light-scattering detector. Five major glycolipid classes (acylated steryl glucoside, steryl glucoside,
ceramide monohexoside, monogalactosyldiacylglycerol, and digalactosyldiacylglycerol) were separated and determined with a
binary gradient system consisting of chloroform and methanol/water (95∶5, vol/vol) without any interference from other lipid
classes and pigments. The described method was applied to 48 edible plants available in Japan including cereals, legumes,
vegetables, and fruits. Examined plant species contained glycolipids in wide concentration ranges, such as 5–645 mg/100 g
tissue. 相似文献
10.
A rapid method for the separation of the individual phospholipid classes phosphatidylcholine (PC), phosphatidylethanolamine
(PE), phosphatidylserine (PS) and phosphatidylinositol (PI) by a single solid-phase extraction was developed. PC, PE, PS and
PI were sequentially eluted from aminopropyl bonded silica with acetonitrile/n-propanol (2∶1, vol/vol), methanol, isopropanol/methanolic HCl (4∶1, vol/vol) and methanol/methanolic HCl (9∶1, vol/vol).
Standard recoveries were over 95% for PC and PE and over 85% for PS and PI with undistorted fatty acid composition. The separation
of complex lipid mixtures on aminopropyl minicolumns can be refined to the level of individual phospholipid classes. 相似文献
11.
Niger (Guizotia abyssinica) seed was ground and then defatted with hexane. The meal remaining after oil extraction was tested as a source of antioxidants.
Three solvent systems, A [80∶20 (vol/vol) ethanol/water], B [80∶20 (vol/vol) acetone/water], and C (water) were evaluated
as extraction media. Crude extracts were examined for their antioxidant activity in a β-carotene-linoleate and a meat model
system. Extract A exhibited superior antioxidant activity, compared to extracts B and C, and its composition was studied further
by using column chromatography and HPLC. Four fractions (I–IV) were obtained, of which fractions III and IV showed activity
in the β-carotene-linoleate model system. Fraction IV was also highly effective in scavenging the 2,2-diphenyl-1-picrylhydrazyl
radical but was less active when used in a bulk oil model system. Preparative TLC showed fraction IV as consisting of two
components. UV spectroscopy suggested that the major active component pressent was a chlorogenic acid-related compound. Furthermore,
HPLC analysis established that chlorogenic acid was dominant in the free phenolics fraction (2.6 mg/g). Upon hydrolysis, however,
a substantial amount of caffeic acid (42.8 mg/g) was released, presumably from esterified and glycosylated chlorogenic acid.
Thus, niger extracts derive their antioxidant activity, at least in part, from the chlorogenic acid-related compounds. 相似文献
12.
Concentrations of synthetic antioxidants butylated hydroxyanisole, butylated hydroxytoluene, and tert-butyl hydroquinone were quantified using a high-performance liquid chromatograph with spectrofluorometric detector. The antioxidants
were separated and eluted on a reversed-phase column by gradient of a mixture of H2O/acetonitrile/acetic acid (66.5: 28.5∶5, by vol) and a mixture of acetonitrile/acetic acid (95∶5, vol/vol). The eluants were
monitored at emission and excitation wavelengths of 310 and 280 nm, respectively. Calibration curves obtained using peak areas
against concentration showed ligh coefficients of multiple determination (R
2>0.99) for all antioxidants. Known concentrations of added antioxidant standards were recoverable within 98–99% from oils
and over 93% from mouse blood. This method requires minimum sample extraction and purification before analysis and provides
a relatively high percentage recovery. The method has been applied successfully for the measurement of antioxidant concentrations
in oils, dried foods, and biological fluids. 相似文献
13.
Using a new solvent (methyl acetate/n-propanol/chloroform/methanol/0.25% aqueous KCl, 25∶20∶20∶20∶17, v/v) and high performance silica gel thin layer chromatographic
plates, all common gangliosides found in brain can be easily separated with 1 hr. This system is reproducible and “tailing”
is negligible compared with previous solvents. When such a system is applied to separate the gangliosides found during the
development of the rat cerebellum, a considerable heterogeneity is observed. Data are presented (using rechromatography experiments,
fractionation on DEAE-Sephadex, treatment with neuraminidase or alkaline medium and carbohydrate analysis) suggesting that
the complex profiles obtained with this chromatographic system are not due to chromatographic artifacts but result from the
high resolving power of the system. After separation by ion-exchange chromatography, 28 gangliosides can be detected. 相似文献
14.
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
15.
Cholesterol and cholesteryl esters were separated according to their carbon number and number of double bonds by high performance
reversed-phase chromatography (HPRC) using acetonitrile/chloroform/methanol (1∶1∶1, v/v) as a mobile phase. It was found that
within the same equivalent carbon number (ECN) category, cholesterol esters with the highest number of double bonds eluted
ahead of those with a lower number of double bonds, and with thecis isomers eluting ahead of theirtrans partners. Thus, cholesteryl oleate (C27-18∶1c) elutes ahead of cholesteryl palmitate (C27-16∶0) and ahead of cholesteryl elaidate (C27-18∶1t). Human lipoprotein, as well as rat liver cholesteryl esters, were separated using this technique. 相似文献
16.
Dennis J. O’Brien Gerard E. Senske 《Journal of the American Oil Chemists' Society》1994,71(9):947-950
Utilization of lipids containing eicosapentaenoic acid (EPA) produced by microorganisms requires processes for their efficient
recovery from microbial cells. Recovery of EPA from mycelia of the fungusPythium irregulare by solvent extraction with hexane-isopropanol (HIP) in a pilot-plant colloid mill was investigated. Extraction efficiencies
of 96% for lipid and EPA were achieved with a 3∶2 (vol/vol) HIP mixture by milling wet, filtered mycelia for 5 min at a solvent/dry
solids ratio of 100 L/kg. The process yielded a crude extract that contained up to 96% lipid and an EPA content as high as
24% (with no selectivity for EPA). 相似文献
17.
Lida T Nakamori R Yabuta R Yada S Takagi Y Mano N Ikegawa S Goto J Nambara T 《Lipids》2002,37(1):101-110
A facile and efficient synthesis of the carboxyl-linked glucosides of bile acids is described. Direct esterification of unprotected
bile acids with 2,3,4,6-tetra-O-benzyl-d-glucopyranose in pyridine in the presence of 2-chloro-1,3,5-trinitrobenzene as a coupling agent afforded a mixture of the
α- and β-anomers (ca. 1∶3) of the 1-O-acyl-d-glucoside benzyl ethers of bile acids, which was separated effectively on a C18 reversedphase chromatography column (isolated yields of α- and β-anomers are 4–9% and 12–19%, respectively). Subsequent hydrogenolysis
of the α- and β-acyl glucoside benzyl ethers on a 10% Pd−C catalyst in acetic acid/methanol/EtOAc (1∶2∶2, by vol) at 35°C
under atmospheric pressure gave the corresponding free esters in good yields (79–89%). Chemical specificities such as facile
hydrolysis and transesterification of the acyl glucosides in various solvents were also discussed. 相似文献
18.
Determination of squalene in olive oil using fractional crystallization for sample preparation 总被引:1,自引:0,他引:1
A simple, rapid method for the determination of squalene in virgin olive oil was developed using RP-HPLC with detection at
208 nm. Fractional crystallization from methanol/acetone (7∶3, vol/vol) was applied to obtain squalene in the liquid fraction
of the oil prior to HPLC. Elution of squalene was then carried out isocratically with acetone/acetonitrile (40∶60 vol/vol)
within 11 min. The detection limit was 23 mg/kg, and the limit of quantification 79 mg/kg. The precision of the crystallization
procedure (CV%=3.76, n=7) and the mean recovery (92.5 and 81.5% for the 7,000 and 700 mg/kg levels of addition, respectively) were satisfactory.
The method is easily applicable to fulfill future needs for nutrition labeling. 相似文献
19.
Cottonseed extraction with mixtures of acetone and hexane 总被引:3,自引:0,他引:3
Cottonseed flakes were extracted with mixtures of n-hexane and acetone, with the concentration of acetone varying between 10 and 75%. Adding small amounts of acetone (≤25%)
to n-hexane significantly increased the extraction of free and total gossypol from cottonseed flakes. Sensory testing detected
no difference in the odor of cottonseed meals produced either by extraction with 100% n-hexane or by extraction with a 10∶90 (vol/vol) mixture of acetone/hexane. More than 80% of the free gossypol was removed
by the 10∶90 mixture of acetone/hexane, whereas pure n-hexane extracted about 47% of the free gossypol from cottonseed flakes. A solvent mixture containing 25% acetone removed
nearly 90% of the free gossypol that was removable by extraction with pure acetone; the residual meal had only a minimal increase
in odor. In contrast, cottonseed meals produced by extraction with pure acetone had a much higher odor intensity. The composition
of the cottonseed crude oil was insignificantly affected by the acetone concentration of the extraction solvent. The results
indicate that mixtures of acetone and n-hexane can be used as extraction solvents to produce cottonseed crude oil without the concomitant development of odorous
meals. 相似文献
20.
Robert H. McCluer James E. Evans Marcia Williams Ann L. Griffith Nicholas Catsimpoolas 《Lipids》1987,22(4):229-235
Feline omental lipid extracts, previously reported to be angiogenic in the cornea of rabbits, were fractionated and the major
lipid components characterized. Approximately 97% of the chloroform/methanol extract consisted of triglycerides containing
primarily 16∶0, 18∶0, 18∶1 and 18∶2 fatty acids. Trace quantities of free fatty acids, cholesterol, di- and monoglycerides
were also detected. The phospholipid fraction, obtained by solvent partition and Unisil column chromatography and characterized
by high performance liquid chromatography (HPLC)-mass spectrometry, was found to consist of phosphatidylcholine, sphingomyelin,
phosphatidylethanolamine and phosphatidylserine. The neutral glycolipids, isolated by solvent partition and Unisil column
chromatography and identified by high performance thin layer chromatography and HPLC of their perbenzoylated derivatives,
were found to consist of glucosyl- and galactosylceramides, galabiosylceramide, lactosylceramide, globotriaosylceramide and
globotetraosylceramide. The complex glycolipid fraction, obtained from Folch upper phase solvent partition, was found to consist
primarily of Forssman glycolipid and gangliosides GM3 and GD3. Smaller amounts of GM1 and other unidentified gangliosides were also present.
The ganglioside nomenclature is according to the system of Svennerholm (J. Neurochem. 10, 613–623, 1963) 相似文献