Development and Validation of a Simple Reversed‐Phase HPLC‐UV Method for Determination of Malondialdehyde in Olive Oil

A simple, precise, accurate and selective method was developed and validated for determination of malondialdehyde (MDA) in olive oil. Separation was achieved on a reversed‐phase C₈ column using a mobile phase consisting of methanol/0.8 % phosphoric acid (10:90, v/v), at a flow rate of 1.0 ml/min and UV detection at 220 nm. This method was validated according to the requirements for new methods, which include accuracy, precision, selectivity, robustness, a limit of detection, limit of quantitation (LOQ), linearity and range. The current method demonstrated good linearity over the range of 0.5–1000 ppm of MDA with r² greater than 0.999. The recovery of MDA in olive oil ranged from 97.1 to 99.1 %. The method was selective where MDA was distinctly separated from other compounds of the oil with good resolution. The method was also precise where the RSD of the peak areas of replicate injections of MDA standard solution were less than 1 %. The degree of reproducibility of the results obtained as a result of small deliberate variations in the method parameters and by changing the analytical operators proved that the method is robust and rugged. The low LOQ of MDA (0.5 ppm) using this method enables quantitation of MDA at low concentration.     

Influence of edible coating on quality of plum (<Emphasis Type="Italic">Prunus salicina</Emphasis> Lindl. cv. ‘Sapphire’)

Edible coating may enhance the boundary layer resistance resulting in enhanced shelf life of fruits. Plums (Prunus salicina Lindl. cv. ‘Sapphire’) were treated with coating material based on carbohydrate (Versasheen) with sorbitol as plasticizer and stored at 20 °C and 85% RH. The influence of coating on the gas transmission rates was estimated using a carrier of 100% cellulose paper. Coating treatment reduced the transmission rate of CO₂, O₂, and H₂O. Changes in fruit weight, fruit flesh firmness, color parameters (L*, a*, and hue angle), soluble solids content, pH, titratable acidity, ethylene, CO₂, malondialdehyde (MDA), and VIS/NIR fruit reflectance spectrum were recorded in 2-day interval. Edible coating was effective in delaying the increase of pH and the loss of firmness, titratable acidity, L*, hue angle, and MDA. The incorporation of sorbitol showed beneficial effects on decreasing the weight loss, CO₂, and ethylene exchange. In the room temperature storage period, not only fruit ripening was measurable in the VIS (350–750 nm) and NIR (750–1,400 nm) wavelength ranges due to the decrease in the fruit chlorophyll absorption but also water loss, respectively. After 5-day room temperature storage the chlorophyll absorption peak in the spectra was already beyond the detection limit in all treatments, while after 3-day storage, the coating effect on the spectral intensities was feasible to separate control from coated plums.     

大豆异黄酮抗大鼠T细胞衰老及抗氧化作用研究

为研究大豆异黄酮抗大鼠T细胞衰老和抗氧化作用，选用老龄SD大鼠，观察大豆异黄酮对T细胞CD28表达水平及肝脏氧化应激水平的影响。实验设立青年对照组、老龄对照组和大豆异黄酮0．33、0．99g／kgBW剂量组，其中剂量组按剂量灌胃给予大豆异黄酮，对照组灌胃给予等量纯净水。4周后，分别制备肝细胞匀浆和肝单细胞悬液，用硫代巴比妥酸（TBA）比色法测定肝匀浆中丙二醛（MDA）含量，分光光度法测定超氧化物歧化酶（SOD）活力，用流式细胞仪结合双氢罗丹明123（Rh123）和双氢-乙酰乙酸二氯荧光黄（82DCFDA）染色法分别检测肝细胞线粒体膜电位（MMP）及活性氧（ROS）水平；另取外周血测定T淋巴细胞表面CD8／CD28表达情况。结果显示：青年对照组及大豆异黄酮剂量组的肝组织MDA含量均较老年对照组低，而SOD活力及肝细胞MMP水平均较老年对照组高（P〈0．05）；大豆异黄酮剂量组肝细胞内的ROS水平较老年对照组低（P〈0．01）。老年对照组大鼠外周血CD28^＋和CD28^＋／CD8^＋T细胞比例低于青年对照组，而CD28^-／CD8^＋T细胞比例高于青年对照组，给予大豆异黄酮样品组三者比例均介于两对照组之间。提示衰老大鼠外周血T细胞CD28表达降低，肝细胞线粒体膜稳定性下降，氧自由基清除能力下降，过氧化脂质分解的终产物增多；大豆异黄酮可提高老龄大鼠T细胞CD28表达水平，增加肝细胞抗氧化酶活性，稳定线粒体膜电位，减少活性氧产生。     

Effect of diet and fat content on the functional properties of thawed beef

The effect of animal diet (pasture versus grain) and fat content (1, 15 and 25%) on the functional properties and quality of beef stored for 8 months at −20 °C was determined. After storage, pasture-finished beef had significantly (P<0.001) less malondialdehyde than grain-finished. Grain-finished beef had a more vivid red colour than pasture-finished (P<0.01). The remaining functional properties determined in this study were not affected by diet. Protein solubility, emulsion activity index, and cooked batter torsion strain decreased and hue angle increased with increasing fat content. The solubility of total and sarcoplasmic proteins and cooked batter torsion stress and strain decreased (P<0.001) and hue angle increased (P<0.001) with storage time regardless of diet and fat content. It is concluded that there is not much difference in the functional properties of beef finished on pasture or grain. However, pasture-finished beef is more stable to lipid oxidation than the grain-finished, and hence may be more amenable to further processing.     

不同叶龄鸭跖草对咪唑乙烟酸的耐药性差异及生理基础研究

应用盆栽的方法,比较了不同叶龄鸭跖草对咪唑乙烟酸的耐药性。结果表明,随着叶龄的增大,施药后鸭跖草叶中丙二醛（MDA）含量变化量下降,而叶绿素含量、光合速率及气孔导度恢复越快。由于3叶期开始鸭跖草耐药性迅速增强,因此,3叶以前是鸭跖草施药的最佳时期。     

白细胞介素-6对荷瘤小鼠正常组织的辐射保护效应

以受全身照射的S180肉瘤荷瘤小鼠为研究对象,利用化学比色法测定荷瘤鼠肝脏、脾脏、肾脏、心脏、肺、脑和骨髓组织的活性氧(ROS)、丙二醛(MDA)水平和谷胱苷肽过氧化物酶(GSH-Px)、过氧化氢酶(CAT)活性,探讨白细胞介素-6(IL-6)对荷瘤机体正常组织辐射防护效应及机理。结果显示：荷瘤鼠受照射后其肝脏、肾脏、脾脏、骨髓、脑、肺组织匀浆中ROS、MDA含量明显升高,而GSH-Px和CAT活性明显降低,其机制是电离辐射造成抗氧化酶的损伤及机体内自由基含量上升。IL-6能够显著降低受照射荷瘤小鼠肝脏、脾脏、骨髓、脑组织匀浆中活性氧(ROS)、丙二醛(MDA)水平,提高谷胱苷肽过氧化物酶(GSH-Px)和过氧化氢酶(CAT)活性。对肾脏、肺组织匀浆中ROS、MDA含量和GSH-Px、CAT活性无明显影响。本实验提示IL-6通过清除ROS和保护抗氧化酶的损伤起辐射保护作用,IL-6对不同组织细胞辐射保护作用程度不同。是由于机体细胞中IL-6R的数量、亲和力及IL-6信号传导途径存在差异。     

Investigation of the in vivo antioxidative activity of Cynara scolymus (artichoke) leaf extract in the streptozotocin‐induced diabetic rat

The in vivo antioxidant activity of a quantified leaf extract of Cynara scolymus (artichoke) was studied. The aqueous artichoke leaf extract (ALE), containing 1.5% caffeoylquinic acid with chlorogenic acid being most abundant (0.30%), and luteolin‐7‐O‐glucoside as major flavonoid (0.15%), was investigated by evaluating the effect on different oxidative stress biomarkers, after 3 wk oral supplementation in the streptozotocin‐induced diabetic rat model. Apart from two test groups (0.2 g ALE/kg BW/day and 1 g ALE/kg BW/day, where BW is body weight), a healthy control group, untreated oxidative stress group, and vitamin E treated group (positive control) were included. A 0.2 g/kg BW/day of ALE decreased oxidative stress: malondialdehyde and 8‐hydroxydeoxyguanosine levels significantly diminished, whereas erythrocyte glutathione levels significantly increased. A 1.0 g/kg BW/day ALE did not show higher antioxidant activity.     

Comparison of methods for determining malondialdehyde in dry sausage by HPLC and the classic TBA test

A reproducible and sensitive HPLC assay with fluorometric detection for measuring malondialdehyde as an index of lipid peroxidation in dry sausage (salami) has been developed. Following the homogenisation of dry sausage in water, a solution of 5% ice-cooled trichloroacetic acid led to the precipitation of the proteins. The addition of thiobarbituric acid (TBA) (0.02 M) to the filtered mixture and its corresponding incubation (35 min, 100 °C) completed the method. High correlation coefficients (r>0.977), with regard to the distillative TBA test, were obtained. Ratios between the HPLC and the distillation method of 2.23 were found. Also, the effect of the antioxidant BHT and an examination of the distillative classic TBA test have been done. Results indicate that this HPLC method, on account of its simplicity, sensitivity and specificity, may be preferred over the classic TBA test for estimating the rancidity of dry sausage.     

Muscle lipids, vitamins E and A, and lipid oxidation as affected by diet and RN genotype in female and castrated male Hampshire crossbreed pigs

The objectives of this study were to investigate the polar and neutral lipid fatty acid composition, content of retinol, -tocopherol, γ-tocopherol and level of oxidation of the pig muscle (M. longissimus dorsi). Female and castrated male Hampshire crossbreeds were produced in two systems. One group was raised indoors with a more polyunsaturated diet and the other raised outdoors with a more saturated diet. The level of polyunsaturated fatty acids in muscle was higher in the indoor females compared with the outdoor females, indoor castrated males and outdoor castrated males. The increased level of polyunsaturated fatty acids in the muscle, which was accompanied by a relatively low content of -tocopherol, increased the susceptibility to lipid oxidation in the form of MDA (malondialdehyde) in the indoor female pigs. Finally, the level of polyunsaturated fatty acids in the polar lipids was affected by the RN genotype, and this difference was dependent on sex. In conclusion, diet has a major effect on the fatty acid composition and oxidation stability in pork muscle, but additional factors such as sex and RN genotype might also contribute.     

A critical examination of some experimental variables in the 2-thiobarbituric acid (TBA) test for lipid oxidation in meat products

By comparison of various procedures for the determination of TBARS (2-thiobarbituric-acid-reactive substances) in non-cured meat samples, it was found that a direct extraction procedure with trichloroacetic acid gave significantly higher reaction yields than a rapid Kjeltec steam distillation procedure (50 ml distillate in 2.5 min). When optimizing the distillation procedure with regard to distillation principle (heating by thermal conductivity or steam injection) and rate, the reaction yield was more affected by changes in distillation principle than by changes in distillation rate. Simple distillation (conduction heating) yielded significantly higher TBA values than steam distillation at the same distillation rate. The reproducibility of the distillation procedure was found to be about 5–10 times poorer than of the extraction procedure and, because of the high reaction yields and robustness of the extraction procedure, the use of the extraction procedure is recommended with food matrices such as non-cured meat samples with less than 14–18% fat and no artificial colorants.