Oxymyoglobin oxidation and membranal lipid peroxidation initiated by iron redox cycle.

Oxymyoglobin is the main pigment in muscle tissues, responsible for the bright red color of fresh meat. Oxidation of the heme iron from the ferrous to the ferric metmyoglobin produces the brownish color that consumers find undesirable in fresh meat. The aim of this study was to elucidate the mechanism of oxymyoglobin oxidation in muscle tissues by using a model system containing oxymyoglobin and muscle membranes oxidized by an iron redox cycle. Oxidation of oxymyoglobin was determined from the decrease in absorption of the solution measured by a spectrophotometer at 582 nm. Lipid peroxidation was determined by accumulation of TBARS and conjugated dienes. The higher rates of oxidation of oxymyoglobin (20 microM) and lipid oxidation were achieved by using ferric iron and ascorbic acid at concentrations of 50 and 200 microM, respectively. Increasing the concentration of ascorbic acid to 2000 microM switched its effect to antioxidative. Increasing the concentration of oxymyoglobin from 20 to 80 microM inhibited lipid peroxidation by >90% and partially prevented oxymyoglobin oxidation.     

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.     

旱作褐土中氧化铁的厌氧还原与光合型亚铁氧化特征

土壤中铁的氧还过程与碳氮转化及自净能力关系密切,已还原亚铁的氧化受土壤性质的影响。采用室内恒温培养试验研究了旱作褐土中铁还原氧化过程、及其与水溶性碳、NO3-、SO42-的关系。结果表明旱作褐土中铁氧化物在厌氧光照条件下可先被还原后被再次氧化,其再氧化量介于1.46~3.00 mg g-1之间,平均2.09 mg g-1;再氧化速率常数介于0.23~0.80 d-1之间,平均0.48 d-1。再氧化量与土壤无定形铁、水溶性硫酸盐含量、阳离子交换量显著负相关,与土壤总氮、总磷显著正相关;再氧化速率常数与土壤有机碳显著负相关,与黏粒含量极显著正相关。厌氧光照培养可使旱作褐土水溶性无机碳平均降低52.74%,水溶性NO3-降低92.15%,水溶性SO42-增加55.38%。研究结果为深入理解旱作土壤潜在的微生物铁循环转化方式提供理论支持。     

Lipid peroxidation by "free" iron ions and myoglobin as affected by dietary antioxidants in simulated gastric fluids

Grilled red turkey muscle (Doner Kabab) is a real "fast food" containing approximately 200 microM hydroperoxides, homogenized in simulated gastric fluid and oxidized more rapidly at pH 3.0 than at pH 5.0, after 180 min, producing 1200 and 600 microM hydroperoxides, respectively. The effects of "free" iron ions and metmyoglobin, two potential catalyzers of lipid peroxidation in muscle foods, were evaluated for linoleic acid peroxidation at pH 3.0 of simulated gastric fluid. The prooxidant effects of free iron ions on linoleic acid peroxidation in simulated gastric fluid was evaluated in the presence of ascorbic acid. At low concentrations of ascorbic acid, the effects were prooxidative, which was reversed at high concentrations. In the presence of metmyoglobin, ascorbic acid with or without free iron enhanced the antioxidative effect. Lipid peroxidation by an iron-ascorbic acid system was inhibited totally by 250-500 microM catechin at pH 3.0. The catechin antioxidant effect was determined also in the iron-ascorbic acid system containing metmyoglobin. In this system, catechin totally inhibited lipid peroxidation at a concentration 20-fold lower than without metmyoglobin. The ability of catechin to inhibit lipid peroxidation was also determined at a low pH with beta-carotene as a sensitive target molecule for oxidation. The results show that a significant protection was achieved only with almost 100-fold higher antioxidant concentration. Polyphenols from different groups were determined for the antioxidant activity at pH 3.0. The results show a high antioxidant activity of polyphenols with orthodihydroxylated groups at the B ring, unsaturation, and the presence of a 4-oxo group in the heterocyclic ring, as demonstrated by quercetin.     

Inhibition of lipid peroxidation by Lactobacillus acidophilus and Bifidobacterium longum.

The inhibition of lipid peroxidation by Lactobacillus acidophilus and Bifidobacterium longum was investigated using two lipid model systems. All eight strains, including six strains of L. acidophilus and two strains of B. longum, demonstrated an inhibitory effect on linoleic acid peroxidation. The inhibitory rates on linoleic acid peroxidation ranged from 33 to 46% when 1 mL of intracellular cell-free extract was tested. In the second model system, the cell membrane of osteoblast was used as the source for biological lipid. The results indicated that all strains were able to protect biological lipids from oxidation. The inhibition rates on cell membrane lipid peroxidation ranged from 22 to 37%. The effect of L. acidophilus and B. longum on inhibition of fluorescent tissue pigment accumulation was also obtained for osteoblastic cells. The inhibition rates on fluorescent tissue pigment accumulation ranged from 20 to 39%. The antioxidative effect of each milliliter of intracellular cell-free extract of L. acidophilus and B. longum was equivalent to 104-172 ppm of butylated hydroxytoluene (BHT). These results indicated that all strains demonstrated high antioxidative activity. The scavenging ability of lipid peroxidation products, tert-butyl hydroperoxide and malondialdehyde, was also evaluated. The results showed that L. acidophilus and B. longum were not able to scavenge the tert-butyl hydroperoxide. Nevertheless, malondialdehyde was scavenged well by these strains.     

Model studies on the degradation of phenylalanine initiated by lipid hydroperoxides and their secondary and tertiary oxidation products

The reaction of methyl 13-hydroperoxyoctadeca-9,11-dienoate (MeLOOH), methyl 13-hydroperoxyoctadeca-9,11,15-trienoate (MeLnOOH), methyl 13-hydroxyoctadeca-9,11-dienoate (MeLOH), methyl 13-oxooctadeca-9,11-dienoate (MeLCO), methyl 9,10-epoxy-13-hydroxy-11-octadecenoate (MeLEPOH), and methyl 9,10-epoxy-13-oxo-11-octadecenoate (MeLEPCO) with phenylalanine was studied to determine the comparative reactivity of primary, secondary, and tertiary lipid oxidation products in the Strecker degradation of amino acids. All assayed lipids were able to degrade the amino acid to a high extent, although the lipid reactivity decreased slightly in the following order: MeLEPCO > or = MeLCO > MeLEPOH > or = MeLOH > MeLOOH approximately = MeLnOOH. These data confirmed the ability of many lipid oxidation products to degrade amino acids by a Strecker-type mechanism and suggested that, once the lipid oxidation is produced, a significant Strecker degradation of surrounding amino acids should be expected. The contribution of different competitive mechanisms to this degradation is proposed, among which the conversion of the different lipid oxidation products assayed into the most reactive MeLEPCO and the fractionation of long-chain primary and secondary lipid oxidation products into short-chain aldehydes are likely to play a major role.     

水稻土中铁氧化还原循环的光照水分效应

水稻土中铁的氧化还原循环与CO2和CH4排放关系密切。采用恒温厌氧培养试验分别在黑暗、光照条件下研究了不同水分状况对水稻土中铁氧化还原过程、水溶性碳含量及CO2和CH4排放的影响。结果表明,水分和光照是调控土壤铁氧化还原过程及其耦合的碳转化过程的关键环境因子。避光时增加含水量缩短铁还原最大速率出现的时间,促进CH4排放。光照条件下含水量小于50%时增加含水量可促进亚铁的再氧化,大于50%时则抑制了亚铁的再氧化。避光时增加含水量可增加体系的水溶性无机碳含量(WSIC),WSIC与CH4的排放存在显著正相关关系。光照可显著降低体系的WSIC,降低幅度随含水量的增加而增大。在含水量25%～200%范围内,光照可使CO2和CH4排放量分别降低95.80%和96.08%。     

水分条件对豌豆保护酶活性及膜脂过氧化的影响

为探讨不同水分条件对豌豆保护酶系统和膜脂过氧化的影响,采用盆栽人工控水试验方法,模拟干旱胁迫及复水条件,研究了不同水分处理对花荚期豌豆叶片超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)活性以及过氧化产物丙二醛(MDA)含量和脂膜相对透性(RC)的影响,并对花荚期豌豆抗氧化能力进行了综合评价.结果表明:不同程度干旱胁迫历时5 d时并未影响豌豆叶片SOD、CAT活性,但有明显的滞后效应.重度干旱胁迫历时10 d可显著降低豌豆叶片SOD、CAT活性,显著提高MDA含量.不同程度的干旱胁迫均导致豌豆叶片POD活性提高,膜脂相对透性加大.复水可对干旱胁迫所造成的CAT、POD活性变化产生显著补偿作用,对SOD活性变化产生超补偿作用.同时,可显著降低MDA含量和脂膜相对透性;干旱胁迫历时10 d内和复水历时10 d内,豌豆有较强的抗氧化能力,仅在重度胁迫10 d后复水历时达到10 d时抗氧化能力趋弱.     

铝对花生根系膜脂过氧化和保护酶活性的影响

研究了铝对耐铝性不同的两个花生品种根系膜脂过氧化和保护酶活性的影响,结果表明,铝胁迫下,桂花21根系的超氧化物歧化酶(SOD)活性变化不大,而桂花23的SOD活性呈下降趋势;两个品种的过氧化物酶(POD)活性呈上升趋势,桂花21上升的幅度大于桂花23的;桂花21根系的过氧化氢酶(CAT)活性先升高后下降,桂花23的则下降;两个品种的脯氨酸和超氧阴离子自由基(O2-.)的含量均增加,但与对照相比,桂花21的脯氨酸升高的量大于桂花23的,桂花21 O2-.升高的量小于桂花23的;桂花23的丙二醛含量显著增加,而桂花21没有明显变化;两个品种根系电解质渗漏率均升高,桂花23上升的量大于桂花21的。     

低磷胁迫对番茄叶片膜脂过氧化及保护酶活性的影响

许多土壤全磷量很高,但植物可吸收的有效磷却很低,因此作物表现缺磷.番茄是对缺磷敏感的作物,缺磷时,植株矮小,产量品质下降.目前,植物在逆境条件下的膜脂过氧化反应和保护酶系统超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性的变化己广泛用于植物对逆境机理的研究[1].     

镉与酸雨交叉胁迫对大豆种子萌发过程中膜脂过氧化的影响

<正>酸雨(AR)和重金属污染是国内外广为关注的重要环境问题[1]。镉(Cd)是污染环境的重金属之一,农作物可从土壤和大气中吸收Cd,生长发育受到抑制,表现为生长缓慢、植株矮小、褪绿等中毒症状,产量大幅度降低[2]。酸雨可造成土壤中Cd2+淋溶加强,解析量升高,生物可利用性增加[3],因此可加重Cd     

Ionizing radiation and antioxidants affect volatile sulfur compounds, lipid oxidation, and color of ready-to-eat Turkey bologna

Bologna was processed from ground turkey breast meats containing one of four antioxidant treatments (none, rosemary extract, sodium erythorbate, and sodium nitrite). After it was cooked, the bologna was sliced, sealed in gas impermeable bags, exposed to 0, 1.5, and 3.0 kGy gamma-radiation, and then stored at 5 degrees C for up to 8 weeks. Thiobarbuturic acid reactive substances (TBARS), color, and volatile sulfur compounds were measured every 2 weeks during storage. Irradiation had no consistent effect on TBARS values. The rosemary extract and sodium nitrite inhibited, while erythorbate increased, TBARS values, independent of radiation dose or storage time. Irradiation promoted redness and reduced yellowness of the control (no antioxidant) bologna at weeks 0 and 2. The use of nitrite and rosemary extract inhibited the changes in color due to irradiation. Several volatile sulfur compounds (hydrogen sulfide, methanethiol, methyl sulfide, and dimethyl disulfide), measured using a pulsed flame photometric detector, increased with radiation dose. However, none of the antioxidants had any substantial effect on volatile sulfur compounds induced by irradiation. Our results suggest that antioxidants did not consistently affect irradiation-induced volatile sulfur compounds of turkey bologna although they did significantly impact color and lipid oxidation.     

Effects of released iron, lipid peroxides, and ascorbate in trout hemoglobin-mediated lipid oxidation of washed cod muscle

Approximately 7% of the iron associated with hemoglobin was released from the heme protein during 2 degrees C storage in washed cod muscle. EDTA (2.2 mM) neither accelerated nor inhibited hemoglobin-mediated lipid oxidation based on the formation of lipid peroxides and TBARS. This suggested that low molecular weight iron was a minor contributor to hemoglobin-mediated lipid oxidation in washed cod muscle. Ascorbate (2.2 mM) was a modest to highly effective inhibitor of hemoglobin-mediated lipid oxidation depending on which washed cod preparation was assessed. Experimental evidence suggested that the ability of residual ascorbate to breakdown accumulating lipid hydroperoxides to reactive lipid radicals can explain the shift of ascorbate from an antioxidant to a pro-oxidant. Increasing the lipid peroxide content in washed cod muscle accelerated hemoglobin-mediated lipid oxidation and decreased the ability of ascorbate to inhibit lipid oxidation. Preformed lipid peroxide content in cod muscle was highly variable from fish to fish.     

Comparison of quercetin and a non-orthohydroxy flavonol as antioxidants by competing in vitro oxidation reactions.

Two structurally related flavonols, quercetin and morin, along with protocatechuic acid (PA), beta-resorcylic acid (DHBA), and phloroglucinol carboxylic acid (PCA), which represent quercetin and morin degradation products, were assessed with respect to their antioxidant potency by chemical comparisons in competing oxidation reactions. The measurement of the antioxidant capacity was performed with the beta-carotene bleaching method, and the compounds were also tested with respect to their abilities to prevent lipid, protein, and DNA oxidation. The effect of concentration was also considered. The results obtained strongly suggested that quercetin is a powerful antioxidant in every system used, whereas morin is a much weaker antioxidant and in some cases may also have pro-oxidant action. PA and PCA were always inferior antioxidants compared to the parent molecule quercetin; DHBA and PCA exhibited activities comparable to that of morin in reaction comparisons.     

Role of lipid oxidation, chelating agents, and antioxidants in metallic flavor development in the oral cavity

This study investigated the production of metallic flavor, which is a combination of taste and retronasal odor. Chemical reactions in the oral cavity and saliva of healthy subjects were investigated after ingesting iron and copper solutions above and near threshold levels. Significant increase in lipid oxidation (p < 0.001) occurred after metal ingestion, detected as TBARS values. Ferrous ion caused the greatest flavor sensation and lipid oxidation, followed by cupric and cuprous ions. Ferric ion did not cause metallic sensation. Occurrence of oxidation was supported by damage to salivary proteins, detected as protein-carbonyls, and by a significant increase of odorous lipid oxidation related aldehydes. Sensory evaluation demonstrated that antioxidants (vitamins E and C) minimally reduced metallic flavor but that chelating agents (EDTA and lactoferrin) removed the metallic flavor. The role of lipid oxidation is essential for the production of a metallic flavor from ingestion of ferrous, cupric, and cuprous ions.     

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。     

The relationship between the physicochemical properties of antioxidants and their ability to inhibit lipid oxidation in bulk oil and oil-in-water emulsions

Chain-breaking antioxidants differ in their effectiveness at inhibiting lipid oxidation because of their chemical properties and physical location within a food. Our objective was how the physicochemical properties of four structurally related lipid-soluble antioxidants were related to their antioxidant activity. Antioxidants differed in the number of methyl (alpha-tocopherol and delta-tocopherol) or hydroxyl (butylated hydroxytoluene (BHT) and 4-hydroxymethyl-2,6-ditertiarybutylphenol) groups. Surface activity of the antioxidants was in the order of delta-tocopherol > alpha-tocopherol approximately 4-hydroxymethyl-2,6-ditertiarybutylphenol > BHT. Free-radical scavenging activity was similar between alpha-tocopherol and delta-tocopherol as well as BHT and 4-hydroxymethyl-2,6-ditertiarybutylphenol. In bulk menhaden oil, BHT was a more effective antioxidant than 4-hydroxymethyl-2,6-ditertiarybutylphenol while alpha-tocopherol was more effective than delta-tocopherol. In menhaden oil-in-water emulsions, BHT was a more effective antioxidant than 4-hydroxymethyl-2,6-ditertiarybutylphenol while delta-tocopherol was more effective than alpha-tocopherol. These results indicate that the surface activity and polarity of lipid-soluble antioxidants were not the only determinants of their antioxidant effectiveness in food lipids.     

Lipid oxidation in emulsions as affected by charge status of antioxidants and emulsion droplets

The influence of charge status of both lipid emulsion droplets and phenolic antioxidants on lipid oxidation rates was evaluated using anionic sodium dodecyl sulfate (SDS) and nonionic polyoxyethylene 10 lauryl ether (Brij)-stabilized emulsion droplets and the structurally similar phenolic antioxidants gallamide, methyl gallate, and gallic acid. In nonionic, Brij-stabilized salmon oil emulsions at pH 7.0, gallyol derivatives (5 and 500 microM) inhibited lipid oxidation with methyl gallate > gallamide > gallic acid. In the Brij-stabilized salmon oil emulsions at pH 3.0, low concentrations of the galloyl derivatives were prooxidative or ineffective while high concentrations were antioxidative. In SDS-stabilized salmon oil emulsions, oxidation rates were faster and the galloyl derivatives were less effective compared to the Brij-stabilized emulsions. Differences in antioxidant activity were related to differences in the ability of the galloyl derivatives to partition into emulsion droplets and to increase the prooxidant activity of iron at low pH.