热处理对轻度加工葡萄膜脂过氧化作用的影响

为探索热处理对轻度加工葡萄衰老软化及贮藏保鲜效果的影响，以红地球葡萄为试验材料,研究了50℃ 10 min、50℃ 15 min、 55℃ 5 min、55℃ 10 min热空气处理对其衰老过程中膜脂过氧化作用及贮藏效果的影响。结果表明，55℃ 5 min和10 min处理与对照相比，能抑制过氧化物酶(POD)、过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性的下降，降低丙二醛(MDA)含量的积累和果肉组织的相对电导率，从而抑制轻度加工葡萄的衰老软化。而50℃ 10 min和15 min热处理对延缓轻度加工葡萄衰老软化无明显作用。     

Assessment of radical scavenging capacity and lipid peroxidation inhibiting capacity of antioxidant

The role of radical scavenging antioxidants against oxidative stress has received much attention, and the antioxidant capacity has been assessed by various methods. Among them, a method that measures the effect of antioxidant on decay of the probe is one of the most widely used methods. The present study was performed to compare the two methods to assess the antioxidant capacity, one to follow the decay of the probe and the other to measure lipid peroxidation products in human plasma. It was shown that the method following probe decay was suitable for assessment of radical scavenging capacity of antioxidant, but not for the capacity to inhibit lipid peroxidation in plasma. This is true whether a hydrophilic or lipophilic probe is used. Such different results arise from the fact that the efficacy of inhibition of lipid peroxidation by antioxidants depends on the fate of antioxidant-derived radical and interaction between antioxidants as well as the capacity of free radical scavenging. Thus, the capacity of antioxidants for inhibition of lipid peroxidation should be assessed from the effect on the extent of oxidation, not from the effect on probe decay.     

Far-infrared radiation increases the antioxidant properties of rice hull extract in cooked turkey meat

To determine the antioxidant effects of rice hull extract exposed to far-infrared radiation, the added extracts were compared with sesamol in cooked turkey breast. Rice hull extract showed antioxidant properties in cooked turkey breast by reducing lipid oxidation and volatile aldehydes. Far-infrared radiation increased significantly the antioxidant activities of rice hull extracts. Rice hull extract irradiated by far-infrared (FRH) had lower TBARS values and fewer volatile aldehydes (hexanal, pentanal, and propanal) than a non-irradiated extract (IRH) during the 3 days of aerobic storage. Addition of FRH at 0.2% (w/w) in turkey meat could reduce the amounts of volatile hexanal to 18-47% of the control during the storage. However, the antioxidant activities of rice hull extracts did not last as long as those of pure sesamol due to the relatively low concentration of phenolics, and the extracts had some peculiar odor. Addition of rice hull extracts also increased both a and b values of the samples due to its brown intensity.     

Determination of total lipid and lipid subclasses in meat and meat products

Current interest in physiological and nutritional activities of the sterol, polyunsaturated fatty acid, and polar lipid fractions of meats and other foods indicates that analytical methods for lipids should be evaluated on their ability to recover and quantitate these classes. Current methods of lipid isolation furnish an extract that is dependent on the solvent(s) used, the type of food material, the temperature of extraction, and the relative proportions of the lipid classes present. Extraction with ethers or other relatively nonpolar solvents removes principally the neutral fats and nonpolar lipids. For an approximation of the crude fat content, such extraction is often sufficient, because the nonpolar fraction generally constitutes over 90% of the total lipids present. The polar lipids include the biochemically important (omega-3) and (omega-6) polyunsaturated fatty acid classes; thus, the method of lipid extraction of food products becomes relevant for a more complete and valuable characterization of their nutritional value. The various methods of lipid determination for meat products are examined for their total recovery of these important lipid groups. A sequential extraction in conjunction with subsequent analytical methods is recommended.     

Mechanism of inhibition of lipid peroxidation by gamma-terpinene,an unusual and potentially useful hydrocarbon antioxidant

gamma-Terpinene (TH), a monoterpene hydrocarbon present in essential oils, retards the peroxidation of linoleic acid (LH). The peroxidation of TH has been shown to yield p-cymene as the only organic product in a chain reaction in which the chain carrier is the hydroperoxyl radical, HOO(.). The peroxidation of LH is well-known to be a chain reaction in which the chains are carried by linoleylperoxyl radicals, LOO., and the products are linoleyl hydroperoxides. The retardation of LH peroxidation by TH has been found to be due to rapid chain termination via a very fast cross-reaction between HOO. and LOO. radicals. This antioxidant mechanism is completely different from the mechanism of antioxidant action of vitamin E. Since vitamin E becomes a prooxidant at high concentrations, the addition of essential oils containing TH to edible lipids may provide an alternative or supplementary strategy for obtaining large increases in their oxidative stability and shelf life, something that cannot be achieved by simply adding more and more vitamin E.     

盐胁迫条件下硒对小白菜抗氧化活性及膜脂过氧化作用的影响

采用土培试验的方法研究了盐胁迫条件下硒对小白菜抗氧化活性及膜脂过氧化作用的影响。结果表明,盐胁迫条件下,硒对小白菜的生物量没有显著影响。硒能显著提高小白菜叶片的谷胱甘肽过氧化物酶、过氧化氢酶、过氧化物酶、超氧化物歧化酶的活性以及还原型谷胱甘肽的含量和硒含量,抗氧化活性显著增强。硒显著降低小白菜体内氧自由基和丙二醛的含量;降低了膜脂过氧化作用,抑制小白菜质膜透性的升高。土壤施硒0.9 mg/kg,可提高小白菜对盐分胁迫的适应能力。     

Detection of lipid peroxidation catalyzed by chelated iron and measurement of antioxidant activity in wine by a chemiluminescence analyzer.

We measured directly the reactive oxygen generated from a peroxide-free reaction system when a ferrous complex with nitrilotriacetic acid was oxidized to the ferric complex. Further, it was observed by a measurement of chemiluminescence that peroxidation of a lipid substrate added in the system is initiated by the Fe(3+)-type of reactive oxygen generated. Antioxidant activity can be estimated by contrasting the reaction rates of lipid peroxidation between the systems with and without a putative antioxidant sample. By this method, the antioxidant activity, expressed as catechin equivalent, of red wines for linoleic acid peroxidation was shown to be higher than those of rosé and white wines (189-311, 84, and 37 microM for red, rosé, and white wines, respectively) because of a higher concentration of polyphenols such as flavanol and anthocyanin in red wines. The chemiluminescence measurement would be a promising method for evaluating the antioxidant potential because of its highly specific and sensitive detection of the hydroperoxide and for monitoring in situ peroxidation reaction.     

Relative inhibition of lipid peroxidation, cyclooxygenase enzymes, and human tumor cell proliferation by natural food colors

The most abundant water soluble natural food colors are betacyanins and anthocyanins. Similarly, lycopene, bixin, beta-carotene, and chlorophyll are water insoluble colors. Pure betanin, bixin, lycopene, chlorophyll, beta-carotene, and cyanidin-3-O-glucoside were isolated from Beta vulgaris, Bixa orellana,Lycopersicum esculentum, Spinacia oleracea, Daucus carrota, and Prunus cerasus, respectively. These natural pigments, alone and in combination, were evaluated for their relative potencies against cyclooxygenase enzymes and tumor cell growth inhibition by using MCF-7 (breast), HCT-116 (colon), AGS (stomach), CNS (central nervous system), and NCI-H460 (lung) tumor cell lines. Among the colors tested, betanin, cyanidin-3-O-glucoside, lycopene, and beta-carotene inhibited lipid peroxidation. However, all pigments tested gave COX-1 and COX-2 inhibition and showed a dose-dependent growth inhibition against breast, colon, stomach, central nervous system, and lung tumor cells, respectively. The mixtures of these pigments were also evaluated for their synergistic effects and chemical interactions at various concentrations. The mixture of anthocyanin and betanin negated their efficacy in the cell growth inhibitory assay and did not enhance the COX enzyme inhibitory activity. This is the first report of a comparative evaluation and the impact on biological activities of these pigments alone and in combination.     

高温和CO2浓度倍增对华北落叶松幼苗抗氧化酶及脂质过氧化的影响

在35℃高温和CO2浓度700μmol/mol的人工模拟复合处理下,研究了华北落叶松幼苗抗氧化酶活性及膜脂过氧化的变化。结果表明,高温胁迫下华北落叶松幼苗超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性呈下降趋势,而在CO2倍增和其与温度复合胁迫下上述酶活性增强;丙二醛(MDA)含量在高温胁迫下提高,在CO2倍增及与温度复合胁迫下降低。表明CO2倍增可以通过提高体内抗氧化酶活性,有效地提高华北落叶松幼苗对高温胁迫的防御能力。     

不同浓度镉胁迫对玉米幼苗光合作用、脂质过氧化和抗氧化酶活性的影响

以玉米为材料,通过营养液培养试验,研究浓度为5~100 μmol/L的镉胁迫后不同时间内,植株体内活性氧代谢及其抗氧化酶活性的变化特征,探讨镉胁迫导致植物体内活性氧自由基累积的原因及不同程度镉胁迫对植物体内活性氧代谢的影响。随着加镉量的增加,玉米地上部生物量明显降低,而根部生物量未表现出差异。镉处理降低了叶片光合作用速率,高镉处理的影响较早。镉处理4d后,5、20、和100 mol/L Cd2+浓度处理玉米叶片Fv/Fm减小,PSII系统的原初光能转换效率下降,但比光合作用速率下降的时间要晚;镉处理7d的叶片中丙二醛（MDA）含量还没有受到明显影响,但20和100 μmol/L Cd2+处理4d后,根系膜质过氧化增强,MDA含量升高。随着镉浓度升高,处理时间延长,活性氧酶清除系统包括超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）和谷胱甘肽还原酶（GR）等酶活性明显增加,受到镉胁迫诱导,高浓度镉处理该现象出现更早。本文试验结果表明,镉胁迫下植物体内活性氧形成增多,诱导活性氧酶清除系统活性升高,其中一个重要原因是与CO2同化受到限制有关。     

Ameliorative influence of sesame lignans on lipid profile and lipid peroxidation in induced diabetic rats

Sesame lignans are working as antioxidants in various physiological functions. In the present study, the antioxidative effect of sesame lignans is examined in chemically induced diabetes mellitus (DM) in rats against lipid profile and lipid peroxidations. DM was induced in four groups of rats by injection of alloxan. The control groups (non-diabetic and diabetic) received a diet containing sunflower oil while the rest of the three experimental diabetic groups received a diet containing 0.25% alpha-tocopherol (D-Toc), 0.5% sesame lignan (D-SL), and 0.25% alpha-tocopherol+0.25% sesame lignan (D-Toc-SL) in sunflower oil for 4 weeks. Lipid profile and lipid peroxidations of plasma, erythrocyte membrane (EM), and liver tissues were measured. The total cholesterol, non-HDL cholesterol, plasma lipid peroxidation, and also LDL-peroxidation decreased, and HDL cholesterol increased significantly (P<0.05) in all the experimental groups as compared to the control diabetic sunflower oil group. The triacylglycerol (TAG) level in plasma decreased significantly in the D-SL and D-Toc-SL groups as compared to control diabetic group. Significant decrease in TAG level was observed in the D-SL group as compared to the D-Toc group. LDL peroxidation also decreased significantly in the D-Toc-SL group as compared to the D-Toc group. EM lipid peroxidation and liver lipid peroxidation decreased significantly in the D-Toc, D-SL, and D-Toc-SL groups as compared to the control diabetic group. Liver TAG level decreased more significantly in the D-SL and D-Toc-SL groups than in the control diabetic group. So, sesame lignans at 0.5% level and sesame lignan + alpha-tocopherol significantly ameliorate the alteration in lipid profile and the adverse free radical generative influence of DM induced by alloxan.     

Rubus fruit juices affect lipid peroxidation in a Drosophila melanogaster model in vivo

The antioxidant capacity of red cloudberry (Rubus chamaemorus) juice correlates well with its phenolic content. The red berries have a markedly higher content of anthocyanins, particularly cyanidin and pelargonidin derivatives, than that found in the more common yellow fruit. Conversely, the yellow juice has higher ellagitannin content. A feeding study was conducted to show the in vivo effects of the juices on lipid peroxidation in a sensitive Drosophila melanogaster stock. In young female flies there were significant (P < 0.01) effects of cloudberry juice on lipid peroxidation. In young male flies significant (P < 0.05) effects were found on primary products (hydroxyperoxides) with yellow juice and on secondary products (ketodienes) with red juice. With the red juice, a significant (P < 0.05) decrease in ketodienes was found in both young and old males. This study demonstrates that the effects of berry antioxidants on lipid peroxidation are easily and rapidly tested in vivo with the sensitive Drosophila model.     

Studies on antioxidant activity of pomegranate (Punica granatum) peel extract using in vivo models

Pomegranate (Punica granatum) peel extracts have been shown to possess significant antioxidant activity in various in vitro models. Dried pomegranate peels were powdered and extracted with methanol for 4 h. The dried methanolic extract was fed to albino rats of the Wistar strain, followed by carbon tetrachloride (CCl4), and the levels of various enzymes, such as catalase, peroxidase, and superoxide dismutase (SOD), and lipid peroxidation were studied. Treatment of rats with a single dose of CCl4 at 2.0 g/kg of body weight decreases the levels of catalase, SOD, and peroxidase by 81, 49, and 89% respectively, whereas the lipid peroxidation value increased nearly 3-fold. Pretreatment of the rats with a methanolic extract of pomegranate peel at 50 mg/kg (in terms of catechin equivalents) followed by CCl4 treatment causes preservation of catalase, peroxidase, and SOD to values comparable with control values, wheres lipid peroxidation was brought back by 54% as compared to control. Histopathological studies of the liver were also carried out to determine the hepatoprotection effect exhibited by the pomegranate peel extract against the toxic effects of CCl4. Histopathological studies of the liver of different groups also support the protective effects exhibited by the MeOH extract of pomegranate peel by restoring the normal hepatic architecture.     

Fractionation of orange peel phenols in ultrafiltered molasses and mass balance studies of their antioxidant levels

Orange peel molasses, a byproduct of juice production, contains high concentrations of phenols, including numerous flavanone and flavone glycosides, polymethoxylated flavones, hydroxycinnamates, and other miscellaneous phenolic glycosides and amines. Extensive fractionation of these phenols was achieved by adsorption, ion exchange, and size exclusion chromatography. Size exclusion chromatography effectively separated the different classes of flavonoids in ultrafiltered molasses, including the polymethoxylated flavones, flavanone-O-trisaccharides, flavanone- and flavone-O-disaccharides, and, finally, flavone-C-glycosides. Mass spectral analysis of the early-eluting flavonoid fractions off the size exclusion column revealed a broad collection of minor-occurring flavone glycosides, which included, in part, glycosides of limocitrin, limocitrol, and chrysoeriol. Most hydroxycinnamates in the molasses were recovered by ion exchange chromatography, which also facilitated the recovery of fractions containing many other miscellaneous phenols. Total antioxidant levels and total phenolic contents were measured for the separate categories of phenols in the molasses. Inhibition of the superoxide anion reduction of nitroblue tetrazolium showed that a significant amount of the total antioxidant activity in orange peel molasses was attributable to minor-occurring flavones. The miscellaneous phenolic-containing fractions, in which a large portion of the total phenolic content in molasses occurred, also constituted a major portion of the total antioxidants in ultrafiltered molasses.     

Changes in oxygen-scavenging systems and membrane lipid peroxidation during maturation and ripening in blackberry

Maturation and ripening of blackberry (Rubus sp.) fruit was accompanied by decreased activities of oxygen-scavenging enzymes [superoxide dismutase (EC 1.15.1.1), glutathione-peroxidase (EC 1.11.1.9), catalase (EC 1.11.1.6)] and enzymes in the ascorbate-glutathione cycle [ascorbate peroxidase (EC 1.11.1.11), monodehydroascorbate reductase (EC 1.6.5.4), dehydroascorbate reductase (EC 1.8.5.1), and glutathione reductase (EC 1.6.4.2)]. Nonenzyme components in the ascorbate-glutathione cycle such as ascorbate (AsA), dehydroascorbate (DHAsA), glutathione (GSH), and oxidized glutathione (GSSG) and the ratios of AsA/DHAsA, GSH/GSSG were also decreased. These decreases in antioxidant capacity were correlated with increases in the ratios of saturated to unsaturated fatty acid of polar lipids and free sterols to phospholipids, thus contributing to decreased fluidity, enhanced lipid peroxidation, and membrane deterioration, which may be associated with ripening and senescence in blackberry fruit.     

Evaluation of red chicory extract as a natural antioxidant by pure lipid oxidation and yeast oxidative stress response as model systems

The search for renewable and abundant sources of antioxidants has recently focused on agricultural byproducts, especially promising due to their natural origins and low costs. In particular, plant raw materials are sources of important compounds such as dietary fiber, carotenoids, tocopherols, and polyphenolics, which are mostly discarded during harvesting and processing. Among these vegetal crops, red chicory is attractive because of the large quantity of its byproducts (residues as leaves and stems); moreover, there is no information on its role as a food and feed ingredient. In this study, red chicory leaf residue was evaluated as a natural substitute for synthetic antioxidants for the food and feed industry. After lyophilization, a red chicory extract (RC) was characterized for its phenolic profile and its oxidative stability as compared to BHT. RC was shown to reduce lipid peroxidation of different oils in the Rancimat test. In addition, the antioxidant property of RC was studied in a model system by evaluating the Saccharomyces cerevisiae response to oxidative stress by means of gene expression. In this analysis, the RC extract, added to the yeast culture prior to oxidative stress induction, exhibited a pleiotropic protective effect on stress responsive genes.     

A role for sediments in retarding the acidification of headwater lakes

Experiments conducted on selected minerals and headwater lake sediments showed that major acid neutralization reactions above pH 4.5 were reactions releasing Ca²⁺ and Mg²⁺ from the sediments. Analysis of the sediments and water from 97 headwater lakes in northern Ontario showed a predictable decrease in the exchangeable Ca⁺ Mg²⁺ of the sediments with decreasing lakewater pH. Estimates of the total potential buffering capacity for the sediments above PH 4.5 and for water in these headwater lakes were made, and it was found that, even when only the top 1 cm of sediment is considered, a substantial sediment buffering reserve is available.     

枣果皮中酚类物质提取工艺优化及抗氧化活性分析

为提高枣果皮中的酚类物质的提取效率,该文以马牙枣为试验材料,对枣果皮中酚类物质提取条件进行了优化,同时通过测定酚类物质清除2,2’-二苯基-1-间三硝苯基联肼(DPPH),2,2'-连氮基双(3-乙基苯并噻唑啉)-6-磺酸(ABTS)自由基和铁还原能力,分析了枣果皮提取物中酚类物质的抗氧化活性。结果显示,枣果皮中酚类物质提取的最优条件是采用70%(V/V)的甲醇、在40℃下,以1∶60的料液比浸提4h,重复浸提2次。枣果皮中酚类物质具有很强的抗氧化能力,与合成抗氧化剂2,6-二叔丁基对甲酚(BHT)相比,虽然果皮中酚类物质清除ABTS·+自由基能力略低于BHT,但其清除DPPH自由基和铁还原能力与之相当。研究结果表明枣果皮中酚类物质具有很强的抗氧化能力,在一定程度上可以取代合成抗氧化剂BHT,应用于食品加工业。     

Effect of plant phenolics on protein and lipid oxidation in cooked pork meat patties

Rapeseed and pine bark are rich sources of phenolic compounds that have in previous studies been shown to exhibit antioxidant and anti-inflammatory properties. In this study, the antioxidant effect of rapeseed and pine bark phenolics in inhibiting the oxidation of lipids and proteins in meat was tested as a possible functional food application. The cooked pork meat with added plant material was oxidized for 9 days at 5 degrees C under light. The suitable level of plant material addition was first screened by following lipid oxidation only. For further investigations plant materials were added at a level preventing lipid oxidation by >80%. The oxidation was followed by measuring the formation of hexanal by headspace gas chromatography and the formation of protein carbonyls by converting them to 2,4-dinitrophenylhydrazones and measured by spectrophotometer. It was shown that rapeseed and pine bark were excellent antioxidants toward protein oxidation (inhibitions between 42 and 64%). These results indicate that rapeseed and pine bark could be potential sources of antioxidants in meat products.