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1.
Biocatalysis of linoleic acid to conjugated linoleic acid 总被引:2,自引:1,他引:1
CLA refers to a group of geometrical and positional isomers of linoleic acid (LA) with conjugated double bonds. CLA has been
reported to have diverse health benefits and biological properties. Traditional organic synthesis is highly capital-intensive
and results in an isomeric mixture of CLA isomers. Biotechnology presents new alternatives to traditional lipid manufacturing
methods. The objective of this study was to examine the effect of protein isolation procedures on linoleate isomerase (LAI)
recovery from microbial cells and biocatalysis of LA to CLA. Protein isolation experiments were carried out using Lactobacillus acidophilus L1 and two strains of Lactobacillus reuteri (ATCC 23272 and ATCC 55739). Under the same assay conditions, ATCC 55739 had the highest LAI activity among the microbial
cultures examined in this study. Efficiency of cell lysis methods, which included various combinations of lysozyme and mutanolysin
treatments in combination with sonication and osmotic rupture of cells with liquid nitrogen, was very low. Although treatment
of cell material with a detergent (octylthioglucoyranoside) freed a significant amount of LAI activity into the solution,
it was not sufficient to recover all the LAI activity from the residual cells. Crude LAI preparations produced mainly the
cis-9,trans-11 CLA isomer. Time and substrate/protein ratio had a significant effect on biocatalysis of LA to CLA. It appears that the
mechanism and kinetics of enzymatic conversion of LA to CLA are quite complex and requires further research using pure LAI
preparations.
Published with approval of the Director, Oklahoma Agricultural Experiment Station. 相似文献
2.
The effect of conjugated linoleic acid on plasma lipoproteins and tissue fatty acid composition in humans 总被引:3,自引:10,他引:3
Conjugated linoleic acid (CLA) has been suggested by some animal studies to possess antiatherogenic properties. To determine,
in humans, the effect of dietary CLA on blood lipids, lipoproteins, and tissue fatty acid composition, we conducted a 93-d
study with 17 healthy female volunteers at the Metabolic Research Unit of the Western Human Nutrition Research Center. Throughout
the study, subjects were fed a low-fat diet [30 energy percent (en%) fat, 19 en% protein, and 51 en% carbohydrate] that consisted
of natural foods with the recommended dietary allowances for all known nutrients. After a 30-d stabilization period, subjects
were randomly assigned to either an intervention group (n=10) supplemented daily with capsules containing 3.9 g of CLA or a control group (n=7) that received an equivalent amount of sunflower oil. The CIA capsules (CLA 65%) contained four major cis/trans geometric isomers (11.4% 9 cis-,11 trans-18∶2; 10.8% 8 trans-,10 cis-18∶2; 15.3% 11 cis-,13 trans-18∶2; and 14.7% 10 trans-, 12 cis-18∶2) and their corresponding cis/cis (6.74% total) and trans/trans (5.99% total) varieties in smaller amounts. Fasting blood was drawn on study days 30 (end of the stabilization period), 60
(midpoint of the intervention period), and 93 (end of the intervention period). Adipose tissue samples were taken on days
30 and 93. CLA supplementation for 63 d did not change the levels of plasma cholesterol, low density lipoprotein cholesterol,
high density lipoprotein cholesterol, and triglycerides. The weight percentage of CLA in plasma increased from 0.28±0.06 to
1.09±0.31 (n=10, P<0.05) after the supplementation. The 9 cis-,11 trans-isomer was the most prominent variety followed by the 11 cis-,13 trans- and 10 trans-,12 cis-isomers in lesser amounts. CLA in adipose tissue was not influenced by the supplementation (0.79±0.18 to 0.83±0.19 wt%) (n=10) and the 9 cis-,11 trans-variety was the only isomer present. Thus, contrary to findings from some animal studies, CLA does not seem to offer health
benefits, in the short term, regarding the prevention of atherosclerosis in humans. CLA supplementation for 2 mon did not
alter the blood cholesterol or lipoprotein levels of healthy, normolipidemic subjects. The supplementation did increase CLA
in the plasma but only 4.23% of the ingested CLA was present in the plasma at any given time. No adverse effect of CLA supplementation
was detected in this study. 相似文献
3.
共轭亚油酸粉末化微胶囊的制备 总被引:1,自引:0,他引:1
研究了喷雾干燥法制备共轭亚油酸微胶囊的工艺参数及配比条件。结果表明,最佳的工艺参数及配比条件为:乳液80℃热处理60 m in,乳化剂蔗糖酯加入量为水液的1%~1.5%,大豆分离蛋白与麦芽糊精质量比为1∶4,壁材中玉米糖浆含量38.5%,固形物含量16.7%,共轭亚油酸理论含量16%左右,进风温度130~150℃,进料流量(2.5~3.5)×150 mL/h,进料温度35℃,进风流量1.1 m3/m in左右,喷嘴压力180 kPa。制备出的共轭亚油酸微胶囊有较好的产品质量。 相似文献
4.
Isomers in commercial samples of conjugated linoleic acid 总被引:10,自引:0,他引:10
5.
The amounts of Δ9,Δ11-conjugated linoleic acid (CLA) isomers were determined in loin-associated fat samples of bulls (n=6) and steers (n=7) by capillary gas chromatography of fatty acid methyl ester (FAME) derivatives. The main CLA-isomer—18:2 c9,t11—provided approximately 0.76 ± 0.15% and 0.86 ± 0.15% of total FAME in bulls and steers, respectively. No differences (P>0.05) were observed between the CLA isomer distribution of bulls (t9,c11, 0.026 ± 0.014%; c9,c11, 0.015 ± 0.008%; and t9,t11, 0.029 ± 0.003%) and steers (t9,c11, 0.027 ± 0.014%; c9,c11, 0.015 ± 0.005%; and t9,t11, 0.030 ± 0.007%). 相似文献
6.
Marcel S. F. Lie Ken Jie Corey N. W. Lam Janette C. M. Ho Maureen M. L. Lau 《European Journal of Lipid Science and Technology》2003,105(8):391-396
Epoxidation of methyl (9Z, 11E)‐octadecadienoate ( 1 ) with various epoxidizing agents viz. m‐chloroperoxybenzoic acid, dimethyl dioxirane, methyltrioxorhenium/hydrogen peroxide, potassium peroxomonosulfate (Oxone, 2KHSO5 · KHSO4 · K2SO4)/tetrahydrothiopyran‐4‐one, and Novozyme 435/hydrogen peroxide is described. The reactions furnished the corresponding mono‐epoxy [methyl (11, 12E)‐epoxy‐(9Z)‐octadecenoate ( 2 ) and methyl (9, 10Z)‐epoxy‐(11E)‐octadecenoate ( 3 )] and a mixture of diastereomers of syn‐ and anti‐diepoxy‐stearate [methyl (9, 10Z;11, 12E)‐diepoxystearate ( 4a‐4d )], which were identified by a combination of spectroscopic and spectrometric analyses. 相似文献
7.
Lipase-catalyzed fractionation of conjugated linoleic acid isomers 总被引:14,自引:0,他引:14
Haas MJ Kramer JK McNeill G Scott K Foglia TA Sehat N Fritsche J Mossoba MM Yurawecz MP 《Lipids》1999,34(9):979-987
The abilities of lipases produced by the fungus Geotrichum candidum to selectively fractionate mixtures of conjugated linoleic acid (CLA) isomers during esterification of mixed CLA free fatty
acids and during hydrolysis of mixed CLA methyl esters were examined. The enzymes were highly selective for cis-9,trans-11–18∶2. A commercial CLA methyl ester preparation, containing at least 12 species representing four positional CLA isomers,
was incubated in aqueous solution with either a commercial G. candidum lipase preparation (Amano GC-4) or lipase produced from a cloned high-selectivity G. candidum lipase B gene. In both instances selective hydrolysis of the cis-9,trans-11–18∶2 methyl ester occurred, with negligible hydrolysis of other CLA isomers. The content of cis-9,trans-11–18∶2 in the resulting free fatty acid fraction was between 94 (lipase B reaction) and 77% (GC-4 reaction). The commercial
CLA mixture contained only trace amounts of trans-9,cis-11–18∶2, and there was no evidence that this isomer was hydrolyzed by the enzyme. Analogous results were obtained with these
enzymes in the esterification in organic solvent of a commercial preparation of CLA free fatty acids containing at least 12
CLA isomers. In this case, G. candidum lipase B generated a methyl ester fraction that contained >98% cis-9,trans-11–18∶2. Geotrichum candidum lipases B and GC-4 also demonstrated high selectivity in the esterification of CLA with ethanol, generating ethyl ester fractions
containing 96 and 80%, respectively, of the cis-9,trans-11 isomer. In a second set of experiments, CLA synthesized from pure linoleic acid, composed essentially of two isomers,
cis-9,trans-11 and trans-10,cis-12, was utilized. This was subjected to esterification with octanol in an aqueous reaction system using Amano GC-4 lipase
as catalyst. The resulting ester fraction contained up to 97% of the cis-9,trans-11 isomer. After adjustment of the reaction conditions, a concentration of 85% trans-10,cis-12–18∶2 could be obtained in the unreacted free fatty acid fraction. These lipase-catalyzed reactions provide a means for
the preparative-scale production of high-purity cis-9,trans-11–18∶2, and a corresponding CLA fraction depleted of this isomer. 相似文献
8.
Gaofeng Yuan Haiyan Sun Andrew J. Sinclair Duo Li 《European Journal of Lipid Science and Technology》2009,111(6):537-545
The effects of two isomers of conjugated linolenic acid (CLnA), α‐eleostearic acid (α‐ESA) and punicic acid (PA), on body fat and lipid metabolism were investigated, compared with a conjugated linoleic acid (CLA) mixture (primarily cis9,trans11‐ and trans10,cis12‐18:2) and α‐linolenic acid (ALA), a non‐conjugated octadecatrienoic acid, in the present study. ICR mice were fed either a control diet or one of four experimental diets supplemented with 1% α‐ESA, 1% PA, 1% CLA mixture and 1% ALA in the form of triacylglycerols (TAG) for 6 weeks. The weights of perirenal and epididymal adipose tissues were significantly decreased while the liver weight was significantly increased in mice fed CLA, compared with the control. In contrast to CLA, the tissue weights in α—ESA‐, PA‐ and ALA‐fed mice were not affected. No significant differences were observed in TAG, total cholesterol, high‐density lipoprotein and low‐density lipoprotein cholesterol levels among the five groups. The liver TAG level was significantly decreased in mice fed α‐ESA and PA while it was significantly increased in mice fed the CLA mixture. These results indicate that CLnA and CLA have differential effects on body fat mass and liver TAG levels in mice. 相似文献
9.
10.
通过利用共轭亚油酸的弱酸性质,将共轭亚油酸制成盐,以期生理功能的改变,本文利用具有生物功能活性的共轭亚油酸,先与氢氧化钠反应得到共轭亚油酸的钠盐溶液,再加入氯化锌溶液得到共轭亚油酸锌盐,平均收率为67%。为共轭亚油酸锌制成制剂的进一步研究提供了原料。 相似文献
11.
Jesper R. Gttsche Ellen M. Straarup 《European Journal of Lipid Science and Technology》2006,108(6):468-478
The incorporation of vaccenic acid (VA, 0.5 and 1.2%), conjugated linoleic acid (CLA, mixture of primarily c9,t11‐ and t10,c12‐CLA, 1.2%), linoleic acid (LA, 1.2%) and oleic acid (OA, 1.2%) into different tissues of mice was examined. The effects on the fatty acid composition of triacylglycerols (TAG) and phospholipids (PL) in kidney, spleen, liver and adipose tissue were investigated. VA and CLA (c9,t11‐ and t10,c12‐CLA) were primarily found in TAG, especially in kidney and adipose tissue, respectively. Conversion of VA to c9,t11‐CLA was indicated by our results, as both fatty acids were incorporated into all the analyzed tissues when a diet containing VA but not c9,t11‐CLA was fed. Most of the observed effects on the fatty acid profiles were seen in the CLA group, whereas only minor effects were observed in the VA groups compared with the OA group. Thus, CLA increased n‐3 polyunsaturated fatty acids (PUFA) in PL from kidney and spleen and lowered the ratio of n‐6/n‐3 PUFA in these tissues. Furthermore, CLA increased C22 PUFA in the PL fraction of kidney, spleen and liver, but reduced the level of arachidonic acid in PL of liver and spleen and lowered the Δ9‐desaturation indexes in all analyzed tissue TAG. 相似文献
12.
Lu-Te Chuang Amanda E. Leonard Jim-Wen Liu Pradip Mukerji Tammy M. Bray Yung-Sheng Huang 《Lipids》2001,36(10):1099-1103
Conjugated linoleic acid (CLA; 18∶2) refers to a group of positional and geometric isomers derived from linoleic acid (LA; Δ9, 12–18∶2). Using a growing baker's yeast (Saccharomyces cerevisiae) transformed with human elongase gene, we examined the inhibitory effect of CLA at various concentrations (10, 25, 50, and 100 μM) on elongation of LA (25 μM) to eicosadienoic acid (EDA; Δ11,14–20∶2). Among four available individual CLA isomers, only c9,t11- and t10,c12-isomers inhibited elongation of LA to EDA. The extent of inhibition (ranging from 20 to 60%) was related to the concentration of CLA added to the medium. In the meantime, only these two isomers, when added at 50 μM to the media, were elongated to conjugated EDA (c11,t13- and t12,c14–20∶2) by the same recombinant elongase at the rate of 28 and 24%, respectively. The inhibitory effect of CLA on LA elongation is possibly due to competition between CLA isomers and LA for the recombinant elongase. Thus, results from this study and a previous study suggest that the biological effect of CLA is exerted through its inhibitory effect on Δ6-desaturation as well as elongation of LA which results in a decrease in long-chain n−6 fatty acids and consequently the eicosanoid synthesis. 相似文献
13.
Despite extensive research on conjugated linoleic acid (CLA) showing multiple beneficial effects in animal models, little
is known about the role of dietary CLA in human health. To investigate if the beneficial effects of CLA seen in animal models
are relevant to humans, we conducted a study with 17 healthy female volunteers who lived in the Metabolic Research Unit of
the Western Human Nutrition Research Center for 93 d. This paper reports only the results from this study that are related
to the effects of CLA supplementation on blood coagulation, platelet function, and platelet fatty acid composition. Throughout
the study, the subjects were fed a low-fat diet (30 en% fat, 19 en% protein, and 51 en% carbohydrate) consisting of natural
foods with the recommended dietary allowances for all known nutrients. After a 30-d stabilization period, subjects were randomly
assigned to either an intervention group (n=10) whose diet was supplemented with 3.9 g/d of CLA or a control group (n=7) who received an equivalent amount of sunflower oil consisting of 72.6% linoleic acid with no detectable CLA. Platelet
aggregation was measured in platelet-rich plasma using adenosine diphosphate, collagen, and arachidonic acid agonists. No
statistical difference was detected between the amount of agonist required to produce 50% aggregation of platelet-rich plasma
before and after the subjects consumed the CLA, with the exception of a decrease in response to collagen. This decrease was
found in both control and intervention groups with no significant difference between the groups, suggesting that both linoleic
acid (sunflower oil) and CLA might have similar effects on platelet function. The prothrombin time, activated partial thromboplastin
time, and the antithrombin III levels in the subjects were determined. Again, there was no statistically significant difference
in these three parameters when pre-and post-CLA consumption values were compared. The in vivo bleeding times were also unaffected by CLA supplementation (10.4+2.8 min pre- and 10.2+1.6 min postconsumption). Platelet
fatty acid composition was not markedly influenced by the consumption of dietary CLA, although there was a small increase
in the amount of the 9 cis, 11 trans-18∶2 isomer normally present in platelets after feeding CLA for 63 days. In addition, small amounts of the 8 trans, 10 cis-18∶2 and the 10 trans, 12 cis-18∶2 isomers were detected in the platelets along with traces of some of the other isomers. Thus, when compared to sunflower 相似文献
14.
Preparation of conjugated linoleic acid from safflower oil 总被引:5,自引:0,他引:5
David W. L. Ma Antoni A. Wierzbicki Catherine J. Field Michael T. Clandinin 《Journal of the American Oil Chemists' Society》1999,76(6):729-730
Synthetically prepared mixtures of conjugated linoleic acid (CLA) are widely used in animal and cell culture studies to investigate
the potential effects of the Δ9c, 11t-18:2 isomer found in food products from ruminant animals. Alkali isomerization of linoleic acid is a common method used in
the synthesis of a mixture of CLA isomers containing predominantly the Δ9c, 11t-18:2 and Δ10t, 12c-18:2 isomers. Some biological activity might also be mediated by the Δ10t, 12c-18:2 isomer. Currently few published methodologies exist describing procedures for the enrichment of these two isomers. A
method is described herein to take advantage of an inexpensive oil, safflower oil, for use in synthesis of CLA and a procedure
to enrich the Δ10t, 12c-18:2 isomer. 相似文献
15.
In-Hwan Kim Chil-Surk Yoon Soo-Hee Cho Kwang-Won Lee Soo-Hyun Chung Beom-Seok Tae 《Journal of the American Oil Chemists' Society》2001,78(5):547-551
Three commercially available immobilized lipases, Novozym 435 from Candida antarctica, Lipozyme IM from Rhizomucor miehei, and Lipase PS-C from Pseudomonas cepacia, were used as biocatalysts for the interesterification of conjugated linoleic acid (CLA) ethyl ester and tricaprylin. The
reactions were carried out in hexane, and the products were analyzed by gas-liquid chromatography. The effects of molar ratio,
enzyme load, incubation time, and temperature on CLA incorporation were investigated. Novozym 435, as compared to Lipozyme
IM and Lipase PC-C, showed the highest degree of CLA incorporation into tricaprylin. By hydrolysis with pancreatic lipase,
it was found that Lipozyme IM and Lipase PS-C exhibited high selectivity for the sn-1,3 position of the triacylglycerol early in the interesterification, with small extents of incorporation of CLA into the
sn-2 position, probably due to acyl migration, at later reaction times. A small extent of sn-1,3 selectivity during interesterification by Novozym 435 was observed. 相似文献
16.
Adrian Hernandez‐Mendoza Arnoldo Lopez‐Hernandez Charles G Hill Hugo S Garcia 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2009,84(2):180-185
BACKGROUND: Lactobacillus reuteri was grown in De Man/Rogosa/Sharpe (MRS) broth (initial pH 6.5) supplemented with free linoleic acid (LA) at different concentrations (5, 10, 20 and 30 mg mL?1) and incubated aerobically at different temperatures (4, 10, 16, 22 and 30 °C) in order to test its ability to accomplish the bioconversion of LA to conjugated linoleic acid (CLA). Temperatures and LA concentrations producing the highest conversion of LA to CLA in the initial trials were tested further using micro‐anaerobic conditions and a lower initial pH (5.5). RESULTS: Data showed that production of CLA exhibited variations with regard to the fermentation conditions used. The highest production of CLA (0.108 mg mL?1) was measured in a broth containing 20 mg mL?1 free LA that was incubated aerobically at 10 °C for 30 h. When the initial pH of the reaction medium was reduced from 6.5 to 5.5, CLA production decreased. Micro‐aerobic conditions reduced the ability of Lb. reuteri to produce CLA, since production of CLA under aerobic conditions was at least 1.4 times greater. CONCLUSION: Production of CLA by Lb. reuteri at low temperatures and relatively high substrate concentrations provides novel opportunities for the development of functional foods with the benefits of enrichment in CLA and probiotic bacteria. Copyright © 2008 Society of Chemical Industry 相似文献
17.
Effect of conjugated linoleic acid on body composition in mice 总被引:55,自引:7,他引:55
Yeonhwa Park Karen J. Albright Wei Liu Jayne M. Storkson Mark E. Cook Michael W. Pariza 《Lipids》1997,32(8):853-858
The effects of conjugated linoleic acid (CLA) on body composition were investigated. ICR mice were fed a control diet containing
5.5% corn oil or a CLA-supplemented diet (5.0% corn oil plus 0.5% CLA). Mice fed CLA-supplemented diet exhibited 57% and 60%
lower body fat and 5% and 14% increased lean body mass relative to controls (P<0.05). Total carnitine palmitoyltransferase activity was increased by dietary CLA supplementation in both fat pad and skeletal
muscle; the differences were significant for fat pad of fed mice and skeletal muscle of fasted mice. In cultured 3T3-L1 adipocytes
CLA treatment (1×10−4 M) significantly reduced heparin-releasable lipoprotein lipase activity (−66%) and the intracellular concentrations of triacylglyceride
(−8%) and glycerol (−15%), but significantly increased free glycerol in the culture medium (+22%) compared to control (P<0.05). The effects of CLA on body composition appear to be due in part to reduced fat deposition and increased lipolysis
in adipocytes, possibly coupled with enhanced fatty acid oxidation in both muscle cells and adipocytes. 相似文献
18.
Frdric Destaillats Paul Angers 《European Journal of Lipid Science and Technology》2005,107(3):167-172
Chemical pathways responsible of the conjugation of linoleic acid during heat treatments such as refining (deodorization), frying or cooking processes have been investigated. For this purpose, methyl linoleate was submitted to oxidative and non‐oxidative thermal conditions. The resulting degradation products were mainly composed of geometrical and conjugated fatty acid isomers. Oxidative conditions were obtained using tert‐butyl hydroperoxide under inert atmosphere, and air. The obtained results from both thermal oxidative conditions were compared to non‐oxidative thermal treatment. Higher levels of conjugated linoleic acid were found when linoleate was heated under oxidative conditions. Two distinct mechanisms responsible for the formation of CLA isomers are proposed and discussed. Evidence of formation of 9,11‐C18:2 and 10,12‐C18:2 acids from 9,12‐C18:2 by a free‐radical chain reaction is provided. The first step consists in the formation of a free radical by abstraction of an active bis‐allylic hydrogen. By delocalization of the initial free radical, two allylic free radicals were stabilized and converted into the corresponding CLA isomers via the abstraction of a hydrogen radical from other linoleic acid or oxygenated species. Kinetic observations confirmed the significance of the bimolecular mechanism. Moreover, the proposed mechanism is supported by several pieces of information from the literature on peroxidation of linoleic acid. Under pure thermal conditions and/or for diluted samples, a second pathway to the formation of CLA from heat‐treated linoleic acid is proposed via an intramolecular rearrangement of the pentadienyl structure. This thermal [1,3]‐sigmatropic rearrangement results in a mixture of 9,11 and 10,12 CLA isomers. The formed cis/trans CLA isomers were readily rearranged by a [1,5]‐sigmatropic shift to yield trans‐8,cis‐10 and cis‐11,trans‐13 CLA isomers, respectively. 相似文献
19.
Jan Fritsche Sonja Fritsche M. B. Solomon M. M. Mossoba M. P. Yurawecz K. Morehouse Y. Ku 《European Journal of Lipid Science and Technology》2000,102(11):667-672
The amounts of 14 conjugated linoleic acid (CLA) isomers (t12t14, t11t13, t10t12, t9t11, t8t10, t7t9, t6t8; 12,14 c/t, t11c13, c11t13, t10c12, 9,11 c/t, t8c10, t7c9‐18:2) in 20 beef samples were determined by triple‐column silver‐ion high‐performance liquid chromatography (Ag+‐HPLC). Quantitation was performed using an external CLA reference standard consisting of cis9,trans11‐18:2,trans9,trans11‐18:2 and cis9,cis11‐18: 2. Linearity was checked as being r > 0.9999 between 0.02 × 10‐3 to 2 mg/ml. The determination limit (5‐fold signal/noise ratio) of the CLA reference was estimated to be 0.25, 0.50, 1.0 ng/injection for the cis/trans, trans,trans and cis,cis isomers, respectively. As expected, cis9,trans11‐18:2 was the predominant isomer (1.95 ± 0.54 mg/g fat) in beef, followed by trans7,cis9‐18:2 (0.19 ± 0.04 mg/g fat); cis,cis isomers were below the determination limit in most beef samples. Total CLA amounts determined by Ag+‐HPLC were compared to total CLAs determined by gas chromatography (GC, 100 m CPSilTM 88 column). The amounts obtained by GC were generally higher than those determined by Ag+ ‐HPLC due to co‐eluting compounds. 相似文献
20.
Despite repeated suggestions that antioxidant activity of conjugated linoleic acid (CLA), a collective of conjugated dienoic
isomers of linoleic acid, underlies its reported anticarcinogenic and antiatherosclerotic effects, the antioxidant properties
of CLA remain ill-defined. Therefore, this study was undertaken to gain more insight into the mechanism of potential CLA antioxidant
activity. It was tested whether CLA could protect membranes composed of 1-palmitoyl-2-linoleoyl phosphatidylcholine (PLPC)
from oxidative modification under conditions of metal ion-dependent or-independent oxidative stress. Progress of oxidation
was determined by direct spectrophotometric measurement of conjugated diene formation and by gas chromatographic/mass spectrometric
analysis of fatty acids. The oxidative susceptibility of CLA was higher than that of linoleic acid, and comparable to arachidonic
acid. When oxidation of PLPC (1.0 mM) was initiated using the lipid-soluble 2,2′-azobis(2,4-dimethylvaleronitrile) or the water-soluble 2,2′-azobis(2-amidinopropane) hydrochloride, the radical scavengers vitamin E and butylated hydroxytoluene (BHT) at 0.75 μM efficiently
inhibited PLPC oxidation, as evident from a clear lagphase. In contrast, 0.75 μM CLA did not have any significant effect on PLPC oxidation. Inhibition of PLPC oxidation by higher concentrations
of CLA appeared due to competition, not to an antioxidant effect. When oxidation of PLPC was initiated by hydrogen peroxide/Fe2+ (500 μM/0.05–20 μM), both vitamin E (1 μM) and ethylene glycol-bis(aminoethyl ether) tetraacetic acid (50 μM) efficiently inhibited PLPC oxidation. However, CLA (1–50 μM) did not show a clear
protective effect under any of the conditions tested. We conclude that CLA, under these test conditions, does not act as an
efficient radical scavenger in any way comparable to vitamin E or BHT. CLA also does not appear to be converted into a metal
chelator under metal-ion dependent oxidative stress, as had previously been suggested. On the basis of our observations, a
role for CLA as an antioxidant does not seem plausible. 相似文献