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1.
Fenton reactions in lipid phases   总被引:2,自引:0,他引:2  
K. M. Schaich  D. C. Borg 《Lipids》1988,23(6):570-579
Metal catalysis of membrane lipid oxidation has been thought to occur only at cell surfaces. However, conflicting observations of the pro-oxidant activity of ferric (Fe3+) vs ferrous (Fe2+) forms of various chelates have raised questions regarding this dogma. This paper suggests that the solubilities of iron complexes in lipid phases and the corresponding abilities to initiate lipid oxidation there, either directly or via Fenton-like production of reactive hydroxyl radicals, are critical determinants of initial catalytic effectiveness. Partitioning of Fe3+ and Fe2+ complexes and chelates into bulk phases of purified lipids was quantified by atomic absorption spectroscopy. mM solutions of iron salts partitioned into oleic acid at levels of about micromolar. Ethylenediamine tetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) chelates were somewhat less soluble, while adenosine diphosphate (ADP) chelates, and ferrioxamine were soluble as chelates at greater than 10−5 M. Solubilities of all iron compounds in methyl linoleate were 10- to 100-fold lower. To determine whether Fenton-like reactions occur in lipid phases, H2O2 and either Fe2+ or Fe3+ and a reducing agent were partitioned into the lipid along with the spintrap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), and free radical adducts were recorded by electron paramagnetic resonance (EPR). Hydroxyl radicals (OH.) adducts were observed in oleic acid, but in lipid esters secondary peroxyl radicals predominated, and the presence of OH. adducts was uncertain. Presented at the symposium “Free Radicals, Antioxidants, Skin Cancer and Related Diseases” at the 78th AOCS Annual Meeting in New Orleans, LA, May 1987  相似文献   

2.
A lipase secreted by the anaerobePropionibacterium acidipropionici was purified 52-fold with 27% recovery by employing a three-step purification protocol. The enzyme has a small molecular mass (Mr = 6000–8000) as determined by gel filtration and ultracentrifugation. It hydrolyzed palm oil, coconut oil, castor oil, olive oil, groundnut oil and tributyrin. Enzyme activity was inhibited by Ni2+, Ba2+, Mg2+, Cu2+, ethylenediaminetetraacetic acid, iodoacetamide, N-acetylimidazole and nonidet P-40 but stimulated by Ca2+, Co2+, K+, Fe2+, sodium dodecyl sulfate and N-bromosuccinamide. The enzyme showed substrate inhibition for both tributyrin andp-nitrophenyl acetate.  相似文献   

3.
A modified Selected Ion Flow Tube Mass Spectrometry Total Oxyradical Scavenging (SIFT-MS-TOSC) assay has been used to assess the antioxidants present in olive oil samples. The assay compares antioxidants in emulsified olive oil competing with added 2-keto-4-methylthiobutanoic acid (KMBA) for peroxyl radicals formed from thermal decomposition of 2,2′-azobis (2-amidinopropane) hydrochloride. No solvent extraction from the oil is required. The assay reaction is monitored by analysis of ethene, a break down product of KMBA, from attack by peroxyl radicals. A new simpler modification to the TOSC assay was found to produce reliable results requiring measurements of just a single concentration of emulsion. The results of the SIFT-MS-TOSC assay show correlation with results from the Folin Ciocalteu assay of total phenol content and HPLC analysis of several standard antioxidants. The use of hydroxyl radicals generated by the Fenton reaction of Fe3+ with ascorbic acid was also investigated, but with less repeatable results. A wide range of antioxidant levels differing by more than a factor of 10 were found in 20 different olive oils examined.  相似文献   

4.
Poly(acrylic acid‐co‐acrylamide) (PAAAM) hydrogels have been prepared from partly neutralized acrylic acid (AA) and acrylamide (AM) by solution polymerization, and their absorbency and adsorption in both CuCl2 and FeCl3 solutions have been investigated. PAAAM hydrogels and their complexes with Cu2+ or Fe3+ have been characterized by FTIR. The absorbency of PAAAM in both CuCl2 and FeCl3 solutions increases initially and then decreases as the absorbing time increases. The adsorption of PAAAM in both CuCl2 and FeCl3 solutions can be described by the pseudo‐second order chemisorption kinetics proposed by Ho and McKay, and the equilibrium uptake of Cu2+ on PAAAM can well be fit with the Langmuir adsorption isotherm. However, the equilibrium uptake of Fe3+ on PAAAM increases as the initial Fe3+ concentration increases for Fe3+ concentration smaller than 5.625 × 10?3 mol/L, and then decreases with Fe3+ concentration. The largest uptakes for Cu2+ and Fe3+ are 247 and 173 mg/g, respectively. The results also show that the uptake of Cu2+ and Fe3+ on PAAAM increases remarkably when pH of the solution is changed from 2.3 to 4.2 and from 1.0 and 2.1, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007  相似文献   

5.
The oxidation of ferrous ions in acidic sulfate solutions in the presence of cupric ions at elevated air pressures was investigated in a high-intensity gas–liquid contactor. The study was required for the design of the regeneration steps of the novel Vitrisol® desulphurization process. The effects of the Fe2+ concentration, Cu2+ concentration, Fe3+ concentration, initial H2SO4 concentration, and partial oxygen pressure on the reaction rate were determined at three different temperatures, i.e., T?=?50?°C, 70?°C, and 90?°C. Most of the experiments were determined to be affected by the mass transfer of oxygen, and therefore true intrinsic kinetics could not be fully determined. An increase in Fe2+ and Cu2+ concentrations, as well as the partial pressure of oxygen and temperature, increased the Fe2+ oxidation rate. H2SO4 did not influence the Fe2+ oxidation rate. An increase in Fe3+ concentration decreased the Fe2+ oxidation rate. Although determined from experiments partially affected by mass transfer, a first order of reaction in Fe2+ was observed, fractional orders in both Cu2+ and O2 were measured, a zero order in H2SO4 was determined, and a negative, fractional order in Fe3+ was obtained. The activation energy was estimated to be 31.3?kJ/mol.  相似文献   

6.
A poly(vinyl alcohol) membrane (PVA) was modified by radiation graft copolymerization of acrylic acid/styrene (AAc/Sty) comonomers. The Cu and Fe ion‐transport properties of these membranes were investigated using a diaphragm dialysis cell. In the feed solution containing CuCl2 or a mixture of CuCl2 and FeCl3, the PVA‐g‐P(AAc/Sty) membranes showed high degrees of permselectivity toward Cu2+ rather than toward Fe3+. The permeation of Cu2+ ions through the membranes was found to increase with decrease in the grafting yield. However, as the content of Cu2+ ions in the Cu/Fe binary mixture feed solutions decreased, the rate and the amount of transported Cu2+ through the grafted membrane decreased, with no appreciable permselectivity toward Fe3+. When Fe2+ ions were used instead of Fe3+ ions in the feed solution containing Cu2+, the transport of both Cu2+ and Fe2+ through the membrane was observed. The rate of transport of Fe2+ was higher than that of Cu2+. In addition, it was found that the selective transport of ions was significantly influenced by the pH difference between both sides of the membranes. As the pH of the feed or the received solution decreased, both Cu2+ and Fe3+ passed through the membrane and were transported to the received solution. The role of carboxylic acid and the hydroxyl groups of the grafted membranes in the transportation process of ions is discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 125–132, 2000  相似文献   

7.
Analysis of the polar fraction from virgin olive oil and pressed hazelnut oil by high-performance liquid chromatography showed marked differences in the chromatograms of the polar components in the two oils. Six commercial samples of pressed hazelnut oil and 12 samples of virgin olive oil (or blended olive oil including virgin olive oil) were analyzed. The phenolic content of the pressed hazelnut oil samples was 161±6 mg·kg−1. Inspection of the chromatograms showed that the pressed hazelnut oil extracts contained a component that eluted in a region of the chromatogram that was clear in the olive oil samples, and consequently this component could be used to detect adulteration of virgin olive oil by pressed hazelnut oil. The component had a relative retention time of 0.9 relative to 4-hydroxybenzoic acid added to the oil as an internal standard. The ultraviolet spectrum of the component showed a maximum at 293.8 nm, but the component could not be identified. Analysis of blends of oils showed that adulteration of virgin olive oil by commercial pressed hazelnut oil could be detected at a level of about 2.5%.  相似文献   

8.
The redox interactions of iron, manganese, and copper ion pairs including absorption characteristics in a multicomponent soda-lime-silica glass, were investigated. Glasses containing 11–19 mol % Na2O were melted under an air atmosphere in an electric furnace at 1450°C for 8 h. The results of chemical analysis indicated that the redox pairs of Fe2+/Fe3+, Mn2+/Mn3+, and Cu+/Cu2+ shift to more oxidized states as a function of increasing glass basicity. The redox interactions of individual pairs, e.g., Fe2+/Fe3+-Mn2+/Mn3+, Fe2+/Fe3+-Cu+/Cu2+, and Mn2+/Mn3+-Cu+/Cu2+, were not strong but changed with glass basicity. For the three redox pairs, Fe2+/Fe3+-Mn2+/Mn3+-Cu+/Cu2+, both Mn3+ and Cu2+ ions simultaneously and proportionally oxidized Fe2+ to Fe3+ and did not affect one another. The reaction constants log Q 2 of Fe2+/Fe3+-Mn2+/Mn3+ and Mn2+/Mn3+-Cu+/Cu2+ redox pairs decreased while the Fe2+/Fe3+-Cu+/Cu2+ and three redox pairs systems changed markedly with increasing the glass basicity. The oxidizing and reducing powers of each ion changed only slightly in the present of one another, and the absorption spectra of all the single polyvalent elements confirmed to the Lambert-Beer law. The spectra depended directly on the concentrations of each absorbing ion. While the spectra of glass doped with more than one element confirmed the direction of the equilibrium shift, they were used only to predict the degree of interaction. These investigations gave consistent results. The text was submitted by the authors in English.  相似文献   

9.
In this work, a boron-doped diamond (BDD) electrode was evaluated for the electroanalytical determination of millimolar concentrations of Cu2+, Fe2+ and Fe3+ using chronoamperometry. The interfering role that each ion plays on the quantitative determination of other metal ion concentrations was also assessed. No interference from other metal ions was observed when Fe3+ and Fe2+ were analysed. By contrast, reduction of Fe3+ took place at the same potential where [Cu2+] was measured causing a minor interference to the Cu2+ signal. A multiple linear regression (MLR) calibration model was made for each analyte using real bioleaching samples, which demonstrated high coefficients of determination and adequate standard errors. The methods developed were used to monitor bioleaching of chalcopyrite for 4 months. The electroanalytical methods are particularly well-suited for analysing Cu2+, Fe3+ and Fe2+ concentration in acidic mine drainage (AMD) and bioleaching environments.  相似文献   

10.
In this study, changes in an extra virgin olive oil treated with lycopene during storage were analyzed. Pure lycopene (0.5 and 1.0 mg) obtained from tomato was added to two separate bottles, each containing 100 mL of extra virgin olive oil, while another bottle containing the same oil was stored without any treatment. Samples enriched with pure lycopene showed PV remarkably lower than the sample without lycopene, and the total phenol contents were higher in treated oil samples than in the reference sample. In addition, a good correlation (r 2=0.969) between total phenol content and antioxidant power calculated as Trolox Equivalent Antioxidant Capacity (TEAC) was observed. The concentration of added lycopene decreased very slowly; after about 8 mon its residual value was over 60% with respect to the initial concentration.  相似文献   

11.
13C Nuclear magnetic resonance (NMR) spectra of 104 oil samples were obtained and analyzed in order to study the use of this technique for routine screening of virgin olive oils. The oils studied included the following: virgin olive oils from different cultivars and regions of Europe and north Africa, and refined olive, “lampante” olive, refined olive pomace, high-oleic sunflower, hazelnut, sunflower, corn, soybean, rapeseed, grapeseed, and peanut oils, as well as mixtures of virgin olive oils from different geographical origins and mixtures of 5–50% hazelnut oil in virgin olive oil. The analysis of the spectra allowed us to distinguish among virgin olive oils, oils with a high content of oleic acid, and oils with a high content of linoleic acid, by using stepwise discriminant analysis. This parametric method gave 97.1% correct validated classifications for the oils. In addition, it classified correctly all the hazelnut oil samples and the mixtures of hazelnut oil in virgin olive oil assayed. All of these results suggested that 13C NMR may be used satisfactorily for discriminating some specific groups of oils, but to obtain 100% correct classifications for the different oils and mixtures, more information than that obtained from the direct spectra of the oils is needed.  相似文献   

12.
Poly(acrylamide-co-itaconic acid) (AAm/IA) and poly(acrylamide-co-monomethoxyethyl itaconate) (AAm/MEI) hydrogels (HGs) synthesized at different molar ratios were used to study the adsorption of some metal ions as Cu2+, Ni2+, Pb2+, Cd2+, and Fe3+ in aqueous solutions at different concentration: 10, 50, 100, 500, and 1000 mg L−1. Statistical analysis was performed and the effect of the metal ion, ion concentration, and hydrogel (HG) composition, on adsorption and adsorption efficiency, was evaluated for both HGs studied (AAm/IA and AAm/MEI) and each factor gave rise to significant differences (P ≤ 0.05). The adsorption depends on the type of ion, its concentration, and also influenced by the type and composition of the HGs. For each system the adsorption efficiencies for all ions were similar with exception of Fe3+, which showed the highest adsorption efficiency in AAm/MEI HG, but the less for the AAm/IA. For both systems, the maximum adsorption efficiency was observed when the molar ratio AAm/IA or AAm/MEI is 80/20. When the adsorption was carried out with individual ions, AAm/MEI HG was more efficient than AAm/IA. For a multielement sample of Cu2+, Ni2+, Pb2+, and Cd2+, both HGs could adsorb all the ions and their behavioral trend was the same in both cases, in which the adsorption efficiency was Pb2+ > Cu2+ > Cd2+ > Ni2+. The results of the statistical analysis evidence the advantage of its use in this type of studies. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46999  相似文献   

13.
Thermal oxidation of oleic acid at high temperatures was studied using combination of electron spin resonance (ESR) spin-trapping technique and solid phase microextraction (SPME)-Gas chromatography-mass spectrometry-mass spectrometry (GC–MS/MS). Dimethyl pyridine N-oxide (DMPO) was applied as the spin trap. Alkyl, alkoxyl, and oxidized DMPO adducts were identified in the experimental spectra. At 140 °C, the alkyl radical adduct was the major component, accounting for 63.89% of the total radical adducts. However, the alkoxyl radical adduct was the main radical adduct in the temperature range of 120 to 135 °C. The total amount of spins, a parameter to indicate radical concentrations, detected at 140 °C was nearly three times higher than that at 135 °C. And, the total amount of alkyl radical adducts was higher than that of alkoxyl radical adducts at 140 °C, which indicated a higher alkyl radical formation rate. Besides, a larger amount (10.30%) of oleic acid degraded at 140 °C than that at 135 °C with the detection of GC. More (E)-2-Decenal (plastic) and (E)-2-undecenal (herbaceous) formed affect the flavor of frying.  相似文献   

14.
Four kinds of phthalocyanines with 4-fluorophenoxy group (H2Pc, CuPc, Li2Pc, and FePc) are synthesized by the microwave-assisted method under 15 min. The synthesized phthalocyanines have good solubility in aprotic polar solvents and do not form any new aggregation state with a concentration increase. The phthalocyanine coordinated with Li+ ion has a more stable and stronger absorption property in aprotic polar solvents than the phthalocyanine with Cu2+ or Fe2+ ion. The phthalocyanine coordinated with Fe2+ ion is more subject to H-aggregation than other phthalocyanines, especially in polar solvents.  相似文献   

15.
Ultraviolet/visible (UV/vis) spectroscopy was used to determine qualitatively and quantitatively Cu2+, Co2+, Co3+, and Fe3+ in oxidized Cu–Co ore leachates. The mineralogical and chemical characteristics of the three oxidized Cu–Co ore samples considered were determined using Fourier transform infrared spectroscopy (FTIR), X-ray powder diffractometry (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and X-ray fluorescence spectrometry (XRF). The results showed that Cu and Co in the samples were in the form of carrollite (Co2CuS4), malachite (Cu2CO3(OH)2, and heterogenite (CoO(OH)). The samples contained (2.73% Cu and 0.19% Co), (2.82% Cu and 0.07% Co), and (0.03% Cu and 0.05% Co), respectively. Gangues were mainly constituted of quartz, goethite, and hematite. The ultraviolet/visible (UV/vis) results indicated that the wavelengths of absorbance of the metal ions in dilute ethylenediaminetetraacetic acid aqueous solution (pH ≈ 3.5) were Fe3+ (293 nm), Cu2+ (821 nm), Co3+ (344 nm), and Co2+ (512 nm). The molar concentrations of the metal ions obtained using the UV/vis method compared well with the results obtained using the atomic absorption spectroscopy (AAS) method. UV/vis spectroscopy was also used to monitor the conversion of Co3+ into Co2+ using different reducing agents. The results showed that the molar concentration of Co2+ in the aqueous solutions increased with the addition of reducing agents, of about 80.95% (copper foil), 61.22% (ferrous sulfate), and 20.35% (sodium sulfite), respectively.  相似文献   

16.
Two novel tetraester- and PAMAM-branched perylene diimides were synthesized and configured as “fluorophore-spacer-receptor” systems based on photoinduced electron transfer. Due to their long alkylester and alkylamine terminal groups the examined compounds were well soluble in organic solvents. Photophysical characteristics of the dyes were investigated in DMF and water/DMF (1:1, v/v) solution. The ability of the synthesized perylene diimides to detect cations was evaluated by the changes in their fluorescence intensity in the presence of metal ions (Zn2+, Co2+, Cu2+, Fe3+, Pb2+, Hg2+, Ag+ and Ni2+) and protons. The dyes under study displayed “off-on” switching in its fluorescence as a function of pH, which is attributed to disallowing photoinduced electron transfer from the receptor moiety to the fluorophore. PAMAM-branched dye displayed a good pH sensor activity (FE = 6.4), however the pH sensing ability of tetraester was substantially higher (FE = 184). In the presence of Cu2+ and Pb2+ ions tetraester quenched its fluorescence intensity (FQ = 22 and 12 respectively), while PAMAM-branched dye enhanced its fluorescence intensity with pronounced selectivity to Cu2+ and Fe3+ (FE = 3.2 and 4.9, respectively). The results obtained indicate the potential of the novel compounds as fluorescent detectors for metal ions with pronounced selectivity towards Cu2+, Pb2+ and Fe3+ ions and highly efficient “off-on” pH switches, especially a tetraester-branched perylene diimide.  相似文献   

17.
The induction period (IP), determined using accelerated methods such as the Rancimat test, is a parameter that has been used to predict the shelf life of virgin olive oil. The oxygen radical absorbance capacity (ORAC) has recently been proposed as a quality index of virgin olive oil because it measures the efficiency of phenolic compounds in the protection against peroxyl radicals. This study aims to investigate relationships between the ORAC and IP values and proposes ORAC as a new parameter of virgin olive oil stability. The concentrations of phenolics, o-diphenols, tocopherol, β-carotene, lutein, and ORAC and IP values were determined in 33 virgin olive oils. Regression analyses showed that both ORAC and IP values correlate with total phenols and o-diphenols with highly significant indices, whereas the correlations of both ORAC and IP with tocopherols, β-carotene, and lutein were not significant. The ORAC values correlate with the IP values with low but significant indices (R=0.42; P<0.02). The results confirm the key role of phenolic compounds in accounting for the shelf life of virgin olive oil and suggest that the ORAC parameter may be used as a new index of quality and stability.  相似文献   

18.
A novel hydroxytyrosol-based polyacrylate polymer material (pAcHTy) endowed with metal ion adsorption ability was obtained by free radical polymerization of a monomer containing a hydroxytyrosol precursor (tyrosol). Hydroxytyrosol (HTy) is the main natural polyphenolic compound with antioxidant activity occurring in virgin olive oil and in olive oil wastewaters. pAcHTy showed a good chelating activity with respect to Cu2+ ions, especially at pH 6 where short equilibrium times and high adsorption capacity were observed (146 mg/g). From thermodynamic parameters, it has been found that the sorption process was spontaneous at low temperature and exothermic in nature. The adsorption process has been studied by employing three simplified kinetic models, including a pseudo-first-order equation, pseudo-second-order equation, and intraparticle diffusion equation. Kinetic parameters, rate constants, equilibrium sorption capacities, and related correlation coefficients, for each kinetic model, were calculated and discussed. It was shown that the adsorption of Cu2+ ions could be described by the pseudo-second-order equation, suggesting that the adsorption process is presumable a chemisorption. The pAcHTy polymer could find an important application in the medical field, particularly in chelation therapy as well as in the wastewater and drinking water treatment plants.  相似文献   

19.
The effects of water-soluble polymers on the concentration and separation of the aqueous solutions of the metal ions have been studied. The separation of metal ions can be possible by ultrafiltration-complexation process. The effect of Dextran, which is a water-soluble polymer, on the concentration and separation of metal ions (Cu2+, Ni2+, Fe3+) have been investigated by using EC-PEG 4000 alloy membranes. The permeability of these membranes for metal ions has been rrecorded at constant pressure but different pH values. It has been notices that the highest water-permeable membrane is also permeable towards Cu2+ and Ni2+, but has shown a considerable retention for Fe3+ as a result of the hydrolysis of Fe3+. The retentions of metallic ions and metallic-ion-Dextran couples have been determined at constant pressure but different pH and polymer concentration values. It has been shown that Fe3+/Ni2+ and Fe3+/Cu2+ couples can be separated by using Dextran. © 1995 John Wiley & Sons, Inc.  相似文献   

20.
ABSTRACT

The levels of 15 + 1 EU priority polycyclic aromatic hydrocarbons (15 + 1 EU PAHs) have been determined in different edible oils (extra virgin olive oil, virgin olive oil, sunflower oil, corn oil, and soybean oil) available in the Syrian market. The samples have been prepared by donor–acceptor complex chromatography and subsequently characterized by high-pressure liquid chromatography coupled with fluorescence and ultraviolet detection for quantification purposes. Variable levels of contamination have been found within different kinds of edible oil samples, and only chrysene has been detected in all the studied samples. Moreover, the mean total sum of 15 + 1 EU PAHs has shown variation from 29.8 µg/kg (corn oil) to 63.7 µg/kg (virgin olive oil). A total of 11 samples out of 38 samples (28.9%) have not fulfilled the European Union (EU) food law requirements. Nine samples have exceeded the EU legislation limit of benzo[a]pyrene (BaP) (2 µg/kg) and only two samples have exceeded the EU legislation limit of PAH4 (10 µg/kg) and had acceptable level of BaP. Finally, the mean and maximum dietary exposures of PAHs through consumption of edible oils have been estimated.  相似文献   

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