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1.
Three groups of double-muscled Belgian Blue young bulls were fed during different stages of production diets differing in the proportions of linolenic and linoleic acid by including linseed in the concentrate or giving grass silage as main linolenic acid suppliers. Samples of rumen and abomasal contents and of the longissimus thoracis, subcutaneous fat, and liver were taken to analyze the fatty acid pattern with emphasis on the individual trans (t) C18:1 fatty acids and cis-9,trans-11 conjugated linoleic acid (c9t11CLA). Trans C18:1 isomers represented up to 20 g/100 g of total fatty acids in rumen and abomasal contents, whereas the accumulation of c9t11CLA was limited. Total trans C18:1 content in subcutaneous fat and intramuscular fat of the longissimus thoracis comprised 8.4 and 5.2 g/100 g of total fatty acids, respectively, with t11C18:1 being the most abundant one. Compared to rumen contents, subcutaneous and intramuscular fat were enriched in c9t11CLA and contained fewer tC18:1 isomers, resulting in a higher c9t11CLA/t11C18:1 ratio (0.04, 0.22, and 0.22, respectively). This result suggests that the endogenous synthesis of c9t11CLA in adipose tissue by the Delta(9)-desaturase was more important than its ruminal production.  相似文献   

2.
Photoirradiation of soy oil with UV/visible light has been shown to produce significant amounts of trans,trans conjugated linoleic acid (CLA) isomers through conversion of various synthesized intermediate cis,trans isomers. The objective of this study was to determine the kinetics of CLA isomers synthesis to better understand the production of various isomers. Soy oil was irradiated with UV/visible light for 144 h in the presence of an iodine catalyst and CLA isomers analyzed by gas chromatography (GC). Arrhenius plots were developed for the conversion of soy oil linoleic acid (A) to form cis-, trans/trans-, cis-CLA (B), conversion of cis-, trans/trans-, cis-CLA to form trans,trans-CLA (C) with respect to B, and formation of trans,trans-CLA isomers with respect to C. The kinetics of consumption of linoleic acid (LA) to form cis-, trans/trans-, cis-CLA was found to be of second-order with a rate constant of 9.01 x 10-7 L/mol s. The rate of formation of cis-, trans/trans-, cis-CLA isomers depends on the rate of formation from LA and its rate of consumption to form trans,trans-CLA isomers. The conversion of cis-, trans/trans-, cis-CLA isomers to trans,trans-CLA isomers was found to be of first-order with a rate constant of 2.75 x 10-6 s-1. However, the formation of thermodynamically stable trans,trans-CLA isomers (C) with respect to C was found to be a zero-order reaction with a rate constant of 10.66 x 10-7 mol/L s. The consumption of LA was found to be the rate-determining step in the CLA isomers formation reaction mechanism. The findings provide a better understanding of the mechanism of CLA isomers synthesis by photoirradiation and the factors controlling the ratio of various isomers.  相似文献   

3.
Although studies have been performed to test whether conjugated linoleic acid (CLA) acts as an antioxidant, the results were not conclusive. In addition, the CLA widely used in previous research contains 43% cis-9,trans-11 isomer, 45% trans-10,cis-12 isomer, and 10 other minor isomers. The objective of this study was to investigate the antioxidant activity of cis-9,trans-11- and trans-10, cis-12-CLA isomers using high-purity CLA isomers (>98%) by total oxyradical scavenging capacity assay (Winston, G. W.; Regoli, F.; Dugas, Jr., A. J.; Fong, J. H.; Blanchard, K. A. Free Radical Biol. Med. 1998, 24, 480-493). At all concentrations (2-200 microM), t10, c12-CLA performed as an antioxidant with a 15-min lag phase, which was more effective than c9,t11-CLA and alpha-tocopherol at lower concentrations (2 and 20 microM). On the other hand, c9,t11-CLA possessed weak antioxidant activity at 2 and 20 microM, whereas at 200 microM it acted as a strong pro-oxidant, which suggests that discrepancies of the results of the previous studies on the antioxidant properties of CLA may be due to the balance of the antioxidant properties of t10,c12-CLA and the pro-oxidant properties of c9,t11-CLA in different oxidation conditions.  相似文献   

4.
The protective effect of c9,t11-conjugated linoleic acid (CLA) on the inhibition of gap junctional intercellular communication (GJIC) was examined in a human mammary epithelial cell line (MCF-10A) treated with 12-O-tetradecanoylphorbol-13-acetate (TPA), relative to t10,c12-CLA isomer. TPA inhibited GJIC in a dose-dependent and reversible manner and was associated with connexin 43 phosphorylation. Pretreatment of 20 μM c9,t11-CLA for 24 h prior to 60 nM TPA for 1 h prevented the inhibition of GJIC by reducing the phosphorylation of connexin 43 via suppressing extracellular signal-regulated kinases (ERK1/2) activation. Reactive oxygen species (ROS) accumulation by TPA was attenuated by c9,t11-CLA. The efficacy of c9,t11-CLA in protecting inhibition of GJIC, connexin 43 phosphorylation, and ROS production was superior to that of t10,c12-CLA. These results suggest that c9,t11-CLA, including t10,c12-CLA, prevents the carcinogenesis of MCF-10A cells by protecting down-regulation of GJIC during the cancer promotion stage, and lack of their toxicities could be an excellent indicator for the chemoprevention of breast cancer.  相似文献   

5.
Silkworms with conjugated linoleic acid (CLA) incorporated into their lipids (designated CLA silkworms) were produced to enhance the quality of silkworms having a synergistic effect with CLA functions by dietary synthetic CLA. Silkworm larvae were fed fresh mulberry leaves (control diet) until the third instar stage and were then subjected to various levels (0%, 0.1%, 1%, 5%, and 10%) of CLA-sprayed mulberry leaves (designated CLA diet) beginning on the first day of the fourth instar stage and continuing to the third day of the fifth instar stage. CLA contents in CLA silkworms increased proportionally with increasing CLA levels of CLA diets. CLA silkworms on a 1% CLA diet contained 2.2 g CLA/100 g lipid without body weight reduction, whereas CLA silkworms on a 10% CLA diet contained 14.8 g CLA/100 g lipid with a significant reduction of body weight, relative to the control silkworms. The CLA content in the lipids of CLA silkworms on a 10% CLA diet was significantly higher than that of CLA silkworms on a 5% CLA diet. A 0.1% CLA diet was not sufficient to accumulate CLA in the silkworms. Most of the CLA (approximately 99%) of silkworm lipids was present in triglyceride (TG) with a similar ratio of c9,t11 and t10,c12 CLA isomers. These results suggest that a 1% CLA diet was suitable for the production of CLA silkworms.  相似文献   

6.
The incorporation pattern of conjugated linoleic acids (CLA) isomers into the egg yolk of hens in relation to that in the diet was studied. Silver-ion high-performance liquid chromatography (Ag-HPLC) was used to separate individual CLA isomers. It was found that the isomeric distribution pattern in the egg yolk lipids was different from that in the dietary fat. Total cis/trans isomers accounted for 81.2% of total CLA incorporated into the egg yolk, which was in contrast to the value of 92.0% of total CLA in the diet. Total cis/cis isomers accounted for 3.8% total CLA in the diet but they were 6.6% of the total CLA in the egg yolk lipids. In contrast, total trans/trans isomers were 12.2% of the total CLA isomers in the egg yolk lipids, whereas they were only 4.2% of total CLA in the diet. The results showed that total trans/trans-CLA was preferentially incorporated into the egg yolk, whereas the incorporation of total cis/trans-CLA isomers was partially discriminated. Within each group, the incorporation of individual isomers into the egg yolk lipids was also selective. cis-9,trans-11/trans-9,cis-11 and cis-10,trans-12/trans-10,cis-12 were the two major isomers in the diet. Ag-HPLC analysis showed that the former was preferentially transferred into the egg yolk compared with the latter. It was observed that supplementation of CLA in the diet of laying hens decreased the concentration of oleic acid (18:1n-9), arachidonic acid (20:4n-6), and docosahexaenoic acid (22:6n-3) but increased that of linolenic acid (18:3n-3), stearic acid (18:0), and palmitic acid (16:0) in the egg yolk, suggesting that CLA may inhibit Delta6 and Delta9 desaturases.  相似文献   

7.
Data from a number of researchers have shown that conjugated linoleic acid (CLA) has some beneficial health activities in animal models. Because inflammatory responses are associated with pathophysiology of many diseases, the aim of this study is to explore the effect and mechanism of CLA in the regulation of lipopolysaccharide (LPS)-induced inflammatory responses in RAW 264.7 macrophages. The addition of increasing levels of CLA proportionally augmented the incorporation of CLA in cultures. CLA diminished LPS-induced mRNA and protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX2) as well as subsequent production of nitric oxide and prostaglandin E(2), respectively. We further examined the effect of CLA on LPS-induced NF-kappaB activation by Western blot and the electrophoretic mobility shift assay. The addition of CLA at 200 microM significantly diminished LPS-induced protein expression of the cytoplasmic phosphorylated inhibitor kappaBalpha and nuclear p65 as well as NF-kappaB nuclear protein-DNA binding affinity. In conclusion, our data suggest that CLA may inhibit LPS-induced inflammatory events in RAW 264.7 macrophages and this inhibitory activity of CLA, at least in part, occurs through CLA modulating the NF-kappaB activation and therefore negatively regulating expression of inflammatory mediators.  相似文献   

8.
A conjugated linoleic acid (CLA)-rich soy oil has been produced by photoisomerization of soy oil linoleic acid. Nutritional studies have shown that CLA possesses health benefits in terms of reducing certain heart disease and diabetes risk factors. Potato chips are snacks that are readily produced in the CLA-rich soy oil containing CLA levels similar to those of the oil used for frying. The objective of this study was to develop an FTIR method to rapidly determine the CLA content of oil in potato chips. Photoirradiated soy oil samples with ～25% total CLA were mixed with control soy oil, and 100 soy oil samples with total CLA levels ranging from 0.89 to 24.4% were made. Potato chips were fried using each of these 300 g CLA rich soy oil mixtures at 175 °C for approximately 3 min. Duplicate GC-FID fatty acid analyses were conducted on oil extracted from each batch of potato chips. The chip samples were ground and then scanned using ATR-FTIR spectroscopy with the aid of a high-pressure clamp, and duplicate spectra of each sample were averaged to obtain an average spectrum. Calibration models were developed using PLS regression analysis. These correlated the CLA isomer concentrations of potato chips obtained by GC-FID fatty acid analysis with their corresponding FTIR spectral features. The calibration models were fully cross validated and tested using samples that were not used in the calibration sample set. Calibrations for total CLA, trans,trans CLA, trans-10,cis-12 CLA, trans-9,cis-11 CLA, cis-10,trans-12 CLA, and cis-9,trans-11 CLA had coefficients of determinations (R2v) between 0.91 and 0.96 and corresponding root-mean-square error of prediction (RMSEP) ranging from 0.005 to 1.44. The ATR-FTIR technique showed potential as a method for the determination of the CLA levels in unknown potato chip samples.  相似文献   

9.
Butyrivibrio fibrisolvens A38, one of the most active rumen bacteria in conjugated linoleic acid (CLA) production, was characterized in vitro. Previous findings that some inhibitory levels of substrate for biohydrogenation (BH) by B. fibrisolvens A38 resulted in more CLA accumulation led to a prediction that partial inhibition of BH could increase ruminal CLA production. The inhibitory conditions for bacterial growth were less effective on the isomerization step than on the following reduction step. Linoleic acid (LA) was inhibitory not only to cell growth but also to LA hydrogenation, and this effect was greater at high concentrations. The reduction step, converting CLA to hydrogenated products (trans-C18:1 and C18:0), was significantly inhibited, and more CLA accumulated during aerobic incubation when LA was added along with a glycolytic inhibitor, iodoacetate (IAA), to cells that were pre-adapted to LA (1 g/OD at 600 nm/L, P < 0.05). Monensin was more inhibitory than IAA to cell growth but less effective for CLA accumulation. Rumen fluid in the culture medium appeared to activate BH even in an aerobic condition, resulting in a lower CLA level than the control group (P < 0.05). Because the isomerization and reduction steps are coupled reactions in BH of most hydrogenating bacteria including B. fibrisolvens A38 cells, both positive and negative modulations of the reduction steps could be key determinants for CLA accumulation in the rumen.  相似文献   

10.
Three levels (0%, 1%, and 2%) of conjugated linoleic acid (CLA) were combined with two levels (low and high) of monounsaturated fatty acids (MUFA) for pig feeding. The activity of neutral lipase (NL), acid lipase (AL), phospholipase (PL), neutral esterase (NE), and acid esterase (AE) was measured in extracts from muscle and subcutaneous adipose tissues. The addition of CLA in the diet only affected the lipolytic activity in muscle, whereas differences in MUFA content of pig diets were mainly responsible for the lipolytic enzyme modifications observed in adipose tissue. Nevertheless, a significant effect of the interaction CLA x MUFA on the activity of several lipolytic enzymes was observed in both tissues. The effect of either linoleic acid (LA) or CLA on the activity of muscle and adipose lipolytic enzymes was determined by in vitro assays. Remarkable inhibitory or activation effects were detected depending on the enzyme and kind of tissue.  相似文献   

11.
The collective term "conjugated linoleic acid" or "CLA" generally refers to a mixture of conjugated positional and geometric isomers of linoleic (cis-9,cis-12-octodecadienoic) acid. In nature, these isomers are mainly formed in the rumen by biohydrogenation of polyunsaturated fatty acids. This study concerns a first trial of CLA determination in cow's milk fat by Raman spectroscopy. The spectra of pure cis-9-oleic, cis-9,cis-12-linoleic, cis-9,trans-11-linoleic, and trans-10,cis-12-linoleic acids have been examined in comparison with the spectra of selected milk-fat samples containing between 0 and 3% of CLA. The trial of CLA determination by Raman spectroscopy on cow milk fat has reached its objective with the two following results. First, the examination of the Raman spectra allows to identify three specific Raman signals of the chemical bonds associated to the cis,trans conjugated C=C in the rumenic and trans-10,cis-12-octodecadienoic acids at 1652, 1438, and 3006 cm(-1). Second, the calibration of Raman spectrometer for the CLA determination has indicated that these three specific signals suit very well for the accurate and reliable measurement of CLA concentration in milk fat. To our knowledge, the present study is the first successful attempt to determine the CLA content of milk fat by a spectrophotometric method.  相似文献   

12.
Mixtures of t,t conjugated linoleic acid methylester (t,t CLA-Me) isomers were prepared from synthetic CLA, consisting of 47.8% t10,c12 CLA; 45.5% c9,t11 CLA; 2.0% t,t CLA; and 4.7% others, by methylation with BF(3)/methanol (designated TT-TC/CT) in conjunction with purification at -68 degrees C for 24 h. The amount or composition of the TT-TC/CT was greatly affected by the concentration of BF(3) in methanol and the duration of methylation. The methylation of 50 mg of synthetic CLA for 30 min with 1 mL of 7.0% BF(3)/methanol produced a TT-TC/CT (21.54 mg) with the composition of 1.3% t12,t14; 5.9% t11,t13; 42.7% t10,t12; 44.0% t9,t11; 5.0% t8,t10; and 1.1% t 7,t9 CLA, whereas the methylation for 60 min with 14.0% BF(3)/methanol produced a TT-TC/CT (28.62 mg) with the composition of t,t CLA isomers different from that of TT-TC/CT by methylation for 30 min with 7.0% BF(3)/methanol. A large quantity of TT-TC/CT (14.15 g) with the composition similar to that of TT-TC/CT prepared from 50 mg of synthetic CLA was also prepared from 25 g of synthetic CLA. The purity of TT-TC/CT samples was greater than 98%. These results suggest that TT-TC/CT with a purity greater than 98% was easily prepared from synthetic CLA by BF(3)-catalyzed methylation, and the amount and composition of t,t CLA isomers of TT-TC/CT samples could be controlled by methylation conditions.  相似文献   

13.
Lipoxygenases are a family of non-heme enzyme dioxygenases. The role of lipoxygenases is synthesis of hydroperoxides of fatty acids, which perform signaling functions in the body. Studies on conjugated linoleic acids (CLAs) as fatty acids with a potential anti-atherosclerotic function have recently been initiated. The aim of the study was to test the effect of CLAs and linoleic acid on 5- and 15-lipoxygenase (5-LO, 15-LO-1) enzyme activity, their mRNA expression, and concentration in the cells. It was also desired to determine whether the CLAs are substrates for the enzymes. For the experiments monocytic cell line (THP-1) and monocytes obtained from human venous blood were used. Monocytes were differentiated to macrophages: THP-1 (CD14+) by PMA administration (100 nM for 24 h) and monocytes from blood (CD14+) by 7-day cultivation with the autologous serum (10%). After differentiation, macrophages were cultured with 30 microM CLAs or linoleic acid for 48 h. The 15- and 5-lipoxygenase products were measured by HPLC method. mRNA expression and protein content were analyzed by real-time PCR and Western blot analysis. The in vitro studies proved that both CLA isomers are not substrates for 15-LO-1; in ex vivo studies hydroxydecadienoic acid (HODE) concentration was significantly reduced (p = 0.019). The trans-10,cis-12 CLA isomer reduced HODE concentration by 28% (p = 0.046) and the cis-9,trans-11 CLA isomer by 35% (p = 0.028). In macrophages obtained from THP-1 fatty acids did not change significantly mRNA expression of the majority of the investigated genes. CLAs did not change the content of 5-LO and 15-LO-1 proteins in macrophages obtained from peripheral blood. Linoleic acid induced 15-LO-1 expression (2.6 times, p < 0.05). CLAs may perform the function of an inhibitor of lipoxygenase 15-LO-1 activity in macrophages.  相似文献   

14.
Conjugated linoleic acid (CLA) isomers were investigated for free radical scavenging properties against the stable 2,2-diphenyl-1-picryhydrazyl radical (DPPH(*)) by electron spin resonance (ESR) spectrometry and spectrophotometric methods. ESR measurements confirmed that both c9,t11-CLA and t10,c12-CLA directly reacted with and quenched DPPH radicals, whereas spectrophotometric analysis demonstrated that c9,t11-CLA and t10,c12-CLA differed in their kinetic and thermodynamic properties in reacting with DPPH radicals. t10,c12-CLA was shown to exhibit a greater initial velocity in CLA-DPPH radical reactions at levels of 2.5-80 mg/mL, and c9,t11-CLA scavenged more DPPH radicals at steady state. Similar dose and time relationships were observed for both isomers. In addition, a mixture of c9,t11- and t10,c12-CLA isomers demonstrated a greater initial velocity in quenching DPPH radicals than either isomer alone on the same concentration basis, suggesting that a synergistic effect between CLA isomers existed in their reactions with DPPH radicals. These results support the conclusion that individual CLA isomers differ in their biological actions and indicate that interaction(s) between isomers may contribute to their beneficial effects.  相似文献   

15.
This study examined the effects of feeding diets rich in either n-3 or n-6 polyunsaturated fatty acids (PUFA) on the fatty acid composition of longissimus muscle in beef bulls. Thirty-three German Holstein bulls were randomly allocated to either an indoor concentrate system or periods of pasture feeding (160 days) followed by a finishing period on a concentrate containing linseed to enhance the contents of n-3 PUFA and conjugated linoleic acids (CLA) in beef muscle. The relative proportion and concentration (mg/100 g fresh muscle) of n-3 fatty acids in the phospholipid and triglyceride fractions were significantly increased (p < or = 0.05) in muscle lipids of pasture-fed bulls. The pasture feeding affected the distribution of individual CLA isomers in the muscle lipids. The proportion of the most prominent isomer, CLA cis-9,trans-11, was decreased from 73.5 to 65.0% of total CLA in bulls fed on concentrate as compared to pasture. The second most abundant CLA isomers were CLA trans-7,cis-9 and CLA trans-11,cis-13 in bulls fed on concentrate and pasture, respectively. Diet had no effect on the concentration of C18:1 trans-11. In contrast, the concentration of the C18:1 trans-13/14, trans-15, and trans-16 isomers in the muscle lipids was up to two times higher in pasture-fed as compared to concentrate-fed bulls. Pasture feeding enhanced the concentration of n-3 fatty acids, but the diet had no effect on the concentration of CLA cis-9,trans-11.  相似文献   

16.
The objective of this study was to determine whether two of the major conjugated linoleic acid (CLA) isomers, cis-9,trans-11 (c9,t11) and trans-10,cis-12 (t10,c12), are possible substrates for pulmonary 15-lipoxygenase-1 (15-LOX-1) and, therefore, they are also involved in the production of 13(S)-hydroxyoctadecadienoic acid [13(S)-HODE] in biological systems. 13(S)-HODE, a major bioactive metabolite of linoleic acid, is an important intracellular signal agent and is involved in cell proliferation and differentiation in various biological systems. Nordihydroguaiaretic acid (NDGA), a known LOX inhibitor, was used as a control for measuring 15-LOX-1 enzyme activity. It was found that c9,t11-CLA was 25% as active as linoleic acid as a substrate for 15-LOX-1; however, t10,c12-CLA was not a substrate for 15-LOX-1 as measured by 13(S)-HODE production. The authenticity of the production of 13(S)-HODE from c9,t11 as a substrate was established by isolation and cochromatography with pure standard on HPLC using non-radioactive and [14C]-c9,t11-CLA.  相似文献   

17.
Conjugated linoleic acids (CLAs) are a group of octadecadienoic acids (18:2) that are naturally present in food products and may have beneficial health effects. Liposomes and ethanol solutions were prepared by mixing synthetic phosphatidylcholines (PCs) with c9,t11-CLA, t10,c12-CLA, and linoleic acid (LA) in the sn-2 position into natural PCs from soybean, egg yolk, rat brain, and rat heart at 5 mol %. The oxygen diffusion-concentration products were measured using electron spin resonance spin-label oximetry methods. Individual synthetic PCs, the phospholipid matrix, and the tested lipid systems all exhibited influence on oxygen diffusion-concentration products during lipid peroxidation. Incorporating 5 mol % PC(c9,t11-CLA) into soy and egg yolk PC increased oxygen consumption in liposome suspensions while it was decreased in rat heart and brain PCs. On the other hand, PC(t10,c12-CLA) increased oxygen consumption in mixtures with egg yolk and rat heart PC but decreased it in soybean and rat brain PC. By comparison, PC(LA) decreased oxygen consumption in every case. In ethanol solutions, all of the synthetic PCs suppressed the capacity to generate peroxide radicals in the order of LA > c9,t11-CLA > t10,c12-CLA. In addition, PCs containing individual CLA isomers and LA differed in their capacities to react with and quench DPPH radicals in both ethanol solution and liposome, suggesting differences between CLA isomers and LA in DPPH radical-fatty acid interactions. Incorporation of CLA isomers and LA into dimyristyl-PC reduced the phase transition temperature from 23.6 to 23.1 and 23.3 degrees C, respectively. The results of this study provide evidence that the behavior of CLA isomers differs in the microenvironment of membranes possibly due to structural differences that affect the permeability of membranes to oxygen and lipid peroxidation.  相似文献   

18.
Conjugated linoleic acid (CLA)-rich soy oil can be produced by photoisomerization of soy oil linoleic acid to produce a soy oil with up to 20% CLA. Recent studies indicate that mixed soy tocopherols added to refined bleached deodorized (RBD) oil produced significant increase in soy CLA yield during soy oil linoleic acid photoisomerization. However, the effect of common synthetic free radical scavenging antioxidants and specific tocopherols on CLA yield and its oxidative stability is not known. Therefore, this investigation evaluated the effects of various antioxidant systems on soy oil CLA yield and oxidative stability. Soy oil with added antioxidants consisting of combinations of mixed tocopherols (MT), ascorbyl palmitate (AP), butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ) was photoisomerized to produce CLA- rich soy oil. The CLA content was determined by GC-FID analysis and oxidative stability by peroxide value (PV). The soy oil in the presence of TBHQ, MT alone and MT with 500 ppm of AP produced significantly greater CLA yields and improved oxidative stability compared to a control without added antioxidants (p < 0.05). However, added mixed tocopherols produced the greatest CLA yield and also reduced PV relative to the control. Tocopherols in the form of α-, γ- and δ-tocopherols were then each examined as to their relative effect on CLA yields and PV. The largest increase in CLA yield was obtained with 1800 ppm of γ-tocopherols with reduced PV. Mixed tocopherols, TBHQ and γ-tocopherols can be used to increase CLA yield and reduce PV of soy oil during linoleic acid photoisomerization.  相似文献   

19.
Dietary conjugated linoleic acid (CLA; 0-2.0%) increased CLA concentrations in liver microsomes and skeletal muscle homogenates from rats. Dietary CLA decreased oleic and arachadonic acid concentrations in both liver microsomes and skeletal muscle. The presence of CLA in liver microsomes had no impact on linoleic acid, arachadonic acid, and alpha-tocopherol oxidation rates. Dietary CLA (2.0%) also did not alter alpha-tocopherol oxidation rates in liver microsomes or muscle homogenates. Formation of malonaldehyde (MDA) in oxidizing liver microsomes decreased with increasing CLA concentration as determined by measurement of thiobarbituric acid-MDA complexes by HPLC. The ability of CLA to decrease MDA formation without impacting other lipid oxidation markers such as the disappearance of fatty acid and alpha-tocopherol suggests that decreased MDA concentration was the result of CLA's ability to lower polyenoic fatty acids such as arachadonic acid. While CLA does not appear to act as an antioxidant, its ability to decrease polyenoic fatty acid concentrations could decrease the formation of highly cytotoxic lipid oxidation products such as MDA.  相似文献   

20.
The feasibility of Raman spectroscopy in combination with partial least-squares (PLS) regression for the determination of individual or grouped trans-monounsaturated fatty acids (trans-MUFA) and conjugated linoleic acids (CLA) in milk fat is demonstrated using spectra obtained at two temperature conditions: room temperature and after freezing at -80 °C. The PLS results displayed capability for direct semiroutine quantification of several individual CLA (cis-9,trans-11 and trans-10,cis-12 C18:2) and trans-MUFA (trans-4-15 C18:1) in minor concentrations (below 1.0 g/100 g of milk fat). Calibration models were based on reference data cross-correlation or determined by specific scattering signals in the Raman spectra. Distinct bands for trans-MUFA (1674 cm(-1)) and CLA (1653 cm(-1)) from the trans isolated and cis,trans conjugated C ═ C bonds were identified, as well as original evidence for the temperature effect (new bands, peak shifts, and higher intensities) on the Raman spectra of fatty acid methyl ester and triacylglyceride standards, are supplied.  相似文献   

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