Inhibition of methyl linoleate autoxidation by phenolics and other related compounds under mild oxidative conditions

Methyl linoleate (MeLo) is a commercially available substrate widely used for studying the inhibitory properties of pure compounds and plant extracts against lipid oxidation. In this paper, 13 phenolic (benzoic and cinnamic acids, aldehydes and derivatives, and flavonoids) and other related compounds (butylated hydroxyanisole, butylated hydroxytoluene and tocopherols) as well as nine complex mixtures rich in phenolics (wines) or tocopherols (soybean oil extracts) were assayed for their inhibitory activity against MeLo autoxidation under mild conditions (40 °C, darkness and atmospheric pressure). Samples were also assayed for their free radical‐scavenging capacity against 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH^?). Protocatechuic aldehyde, a compound that has not been previously evaluated by either of the two methods, showed the highest antioxidant activity. Some variations in the antioxidant ranking for some compounds were found between our results and those obtained by other authors using accelerated conditions for MeLo oxidation. Antioxidant activity of wines and soybean oil extracts was related to their richness in phenolics and tocopherols respectively. Correlation between antioxidant capacity measured by the MeLo and DPPH^? methods was found for wines but not for the other samples studied. Therefore the measure of the free radical‐scavenging capacity of a compound is not always a reliable indicator of its lipid oxidation inhibitory ability. Copyright © 2004 Society of Chemical Industry     

固体超强酸SO_4~(2-)／SnO_2催化合成亚油酸乙酯

采用浸渍法制备了SO42-／SnO2固体超强酸多相催化剂,用XRD、TPD和FT-IR光谱法对SO42-／SnO2的结构和表面酸性进行了表征。并用于亚油酸与乙醇反应合成亚油酸乙酯,研究了催化剂制备过程中硫酸浸渍浓度、焙烧温度对亚油酸与乙醇酯化反应的影响规律。制备催化剂适宜的工艺条件为:硫酸浸渍浓度2．0 mol／L,浸渍时间4 h,焙烧温度500℃,焙烧时间4 h,制备的SO42-／SnO2催化剂对亚油酸的酯化率可达91．5％。     

离子液体催化合成亚油酸植物甾醇酯

研究了离子液体在亚油酸植物甾醇酯合成中的应用.从[ Bmim] BF4、[Bmim] CF3SO3ChCl·2SnCl2、ChCl·2ZnCl2、ChCl·2.5SnCl2和ChCl·2FeCl3中筛选ChCl·2SnCl2为实验的催化剂,并用吡啶探针法测定了各种离子液体的酸性.通过对酯化率和反应氧化程度的考察,确定最佳反应条件为:离子液体用量为植物甾醇质量的8％,酸醇摩尔比2∶1,反应温度160℃,反应时间4h,经3次平行实验测得平均酯化率为89.73％.合成反应后,离子液体与酯化产物成两相,而且离子液体ChCl·2SnCl2在重复使用5次后仍有较高催化活性.     

单亚油酸丙二醇酯的合成研究与性能评价

用甲苯作携水剂,亚油酸和1,3-丙二醇在氨基磺酸催化下反应合成单亚油酸丙二醇酯,采用红外光谱对其进行结构分析,通过高频往复摩擦试验机评价其抗磨效果并研究了其对加氢裂化柴油理化性质的影响。结果表明,目标产物的最佳合成工艺条件为:反应物料酸醇物质的量比1∶1. 1,反应时间9 h,反应温度145℃,催化剂用量为酸醇总质量的0. 8%。在最佳合成工艺条件下,酯化率达到95. 9%。合成产物具有较好的抗磨性能,其磨斑直径(WS1. 4)为388μm(添加量200μg/g)。得到的酯型产物单亚油酸丙二醇酯具有较低酸值(KOH),为0. 80 mg/g,其作为柴油抗磨剂使用时,主要性能指标均符合抗磨剂相关标准要求,将其加入到柴油中,柴油的各项理化性能亦不受影响。     

GC-MS测定不同采收期酸枣仁中脂肪油成分

利用气相色谱-质谱联用(gas chromatography-mass spectrometry,GC-MS)技术分析经甲酯化的不同采收期酸枣仁的脂肪油成分组成及相对质量分数的变化。结果表明:3个时期酸枣仁的脂肪油成分总含量增加,经过GC-MS分析共检测出29种脂肪油成分,包括不饱和脂肪酸类、饱和脂肪酸类、碳氢化合物和醇类化合物这4大类组分。3个时期酸枣仁中均有其特殊的脂肪油成分,同时各时期也有相同的脂肪油成分,其中亚油酸甲酯(33.01%~34.27%)和油酸甲酯(43.66%~45.43%)为各个时期中的主要脂肪油物质。     

Oxidation of Methyl Linoleate in Oil-in-Water Micro- and Nanoemulsion Systems

Oxidation of methyl linoleate in O/W emulsions having droplets of median diameters ranging from 17 nm to 8.0 μm was carried out at 40°C. The oxidation process was analyzed on the basis of a kinetic equation of the autocatalytic type. The induction period was found to be shorter and the oxidation rate constant lower for emulsions with smaller oil droplets. The stoichiometry between methyl linoleate and oxygen was observed to be independent of both the size of oil droplet and the type of the surfactant and was found to be unity during the early stage of the oxidation. However, more oxgen was consumed in the oxidation of the methyl linoleate in the later half of the oxidation process.     

产亚油酸异构酶菌株的诱变选育及其酶学性质研究

以保加利亚乳杆菌为出发菌株,经紫外诱变选育,获得2株高产酶突变株A1及A2,其酶活分别为30.1U/mL、32.1U/mL,酶活较出发菌株分别提高45%和54%.酶学性质研究表明,A2菌株产亚油酸异构酶的最适反应温度分别为40℃,最适pH 6.5,酶在低于40%时具有良好的热稳定性,pH 6.0～7.0时较稳定.以Lineweaver-Burk双倒数作图法求得亚油酸异构酶的Km为0.039 mmol/L,Vmax为0.24mmol/(h·mg).     

固体超强酸SO_4~(2-)/TiO_2催化合成亚油酸乙酯

用两相滴定沉淀法制备了SO2-4/TiO2固体超强酸催化剂,得到了适合亚油酸酯化的催化剂制备工艺条件:硫酸浸渍浓度0 75mol/L,浸渍时间4h,焙烧温度450℃,焙烧时间4h。首次将该催化剂用于亚油酸的酯化反应催化合成亚油酸乙酯,考察了物料比、反应时间、催化剂用量对亚油酸与乙醇酯化反应的影响规律,最佳反应条件为:n(无水乙醇)/n(亚油酸)=4,w(催化剂)=3%(相对于亚油酸),反应时间8h,亚油酸转化率可达93%。     

亚油酸异构酶高产菌株的选育及产酶条件的优化

共轭亚油酸是一种具有多种生理活性的天然脂肪酸.以嗜酸乳杆菌为出发菌株,经紫外诱变选育,获得1株共轭亚油酸高产菌株并对其发酵条件进行优化.紫外照射选择30 s为适宜的照射处理时间,诱变菌株酶活比原始菌株提高了1.51倍.对培养基的产酶条件进行优化,结果酶活是未优化前的1.1倍.     

Quantitation of Human Whole‐Body Synthesis‐Secretion Rates of Docosahexaenoic Acid and Eicosapentaenoate Acid from Circulating Unesterified α‐Linolenic Acid at Steady State

The rate at which dietary α‐linolenic acid (ALA) is desaturated and elongated to its longer‐chain n‐3 polyunsaturated fatty acid (PUFA) in humans is not agreed upon. In this study, we applied a methodology developed using rodents to investigate the whole‐body, presumably hepatic, synthesis‐secretion rates of esterified n‐3 PUFA from circulating unesterified ALA in 2 healthy overweight women after 10 weeks of low‐linoleate diet exposure. During continuous iv infusion of d5‐ALA, 17 arterial blood samples were collected from each subject at ?10, 0, 10, 20, 40, 60, 80, 100, 120, 150, 180, and 210 min, and at 4, 5, 6, 7, and 8 h after beginning infusion. Plasma esterified d5‐n‐3 PUFA concentrations were plotted against the infusion time and fit to a sigmoidal curve using nonlinear regression. These curves were used to estimate kinetic parameters using a kinetic analysis developed using rodents. Calculated synthesis‐secretion rates of esterified eicosapentaenoate, n‐3 docosapentaenoate, docosahexaenoic acid, tetracosapentaenate, and tetracosahexaenoate from circulating unesterified ALA were 2.1 and 2.7; 1.7 and 5.3; 0.47 and 0.27; 0.30 and 0.30; and 0.32 and 0.27 mg/day for subjects S01 and S02, respectively. This study provides new estimates of whole‐body synthesis‐secretion rates of esterified longer‐chain n‐3 PUFA from circulating unesterified ALA in human subjects. This method now can be extended to study factors that regulate human whole‐body PUFA synthesis‐secretion in health and disease.