High-performance liquid chromatography and spectroscopic studies on fish oil oxidation products extracted from frozen atlantic mackerel

The formation of stable hydroxy derivatives from hydroperoxides produced during the oxidation of linoleic acid methyl ester and fish oil were studied by reverse-phase high-performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS) and ¹³C nuclear magnetic resonance (NMR) spectroscopy. The oxidation products identified were mixtures of four isomeric hydroxy derivatives: 13-hydroxy-9-cis,11-trans-octadecadienoic, 13-hydroxy-9-trans,11-trans-octadecadienoic, 9-hydroxy-10-trans,12-cis-octadecadienoic, and 9-hydroxy-10-trans,12-trans-octadecadienoic acids. The presence of hydroxy compounds was confirmed by ¹³C NMR, which gave rise to a hydroxy carbon peak at 87 ppm, and by GC-MS, which showed three peaks corresponding to isomeric mixtures of trimethylsilyl ethers of the oxidized linoleic acid methyl ester. The mass spectra scans of the three peaks showed that they represent isomers of molecular weight 382 and are consistent with the molecular formula C₂₂H₄₂O₃Si. In oil extracted from stored frozen mackerel, 13-hydroxy-9-cis,11-trans-octadecadienoic acid was more prominent compared to the model lipid systems. HPLC offered a sensitive means of detection of hydroxy compounds produced both in the initiation and latter stages of oxidation. The effect of antioxidants added to the fish mince prior to storage can also be monitored by HPLC. Thus, the monitoring of lipid oxidation hydroxy derivatives by HPLC is of practical value in the efficient processing and quality control of fish, fish oils, and other fatty foodstuffs in order to enhance the acceptability, nutritional, and safety aspects.     

Evaluation of antioxidant property of extract and fractions obtained from a red alga, Polysiphonia urceolata

Antioxidant activity (AA), total phenolic content, and reducing power of the crude extract, fractions, and subfractions derived from a red alga, Polysiphonia urceolata, were evaluated and determined. The antioxidative activity was measured using the α,α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging assay and the β-carotene–linoleate assay systems, and compared with that of butylated hydroxytoluene (BHT), gallic acid (GA), and ascorbic acid (AscA). The results showed that the crude extract and the ethyl acetate-soluble fraction exhibited higher AA than BHT in the DPPH assay model, at all of four concentration levels tested (from 0.4 to 50 μg/ml), while, in the β-carotene–linoleate assay system, the crude extract and the ethyl acetate-soluble fraction exhibited similar or, in most cases, higher AA than GA and AscA at the same concentrations (from 10 to 200 μg/ml). The ethyl acetate-soluble fraction was further fractionated into seven subfractions F1–F7 by silica gel vacuum liquid chromatography. F1 was found to be the most effective subfraction in both assay systems. The total phenolic content and reducing power were determined using the Folin–Ciocalteu and the potassium ferricyanide reduction methods, respectively. Statistical analysis indicated a significant association between the antioxidant potency and total phenolic content as well as between the antioxidant potency and reducing power.     

6-O glucose linoleate supports in vitro human hair growth and lipid synthesis

The hair follicle is a very active organ with a complex structure, which produces a hair fibre at a rate of 0.3 mm a day. Accordingly, the hair follicle is highly demanding in energy source, as the hair bulb matrix cells are endowed with one of the highest rates of proliferation in the human body. Moreover, recent data have shown the involvement of lipids in hair follicle function. As in vitro-grown hair follicle keeps producing a hair fibre that closely resembles the natural hair fibre, we decided to use this model to investigate the role of a new of glucose linoleate derivative (6-O-linoleyl-d-glucose: 6-O-GL) as a lipid precursor and energy provider. Our results demonstrated that 6-O-GL was (i) quite stable and surprisingly resistant to oxidative degradation, and (ii) readily taken up and metabolized by the hair follicle into various lipids, namely neutral lipids, ceramides and polar lipids. Moreover, it supported hair follicle growth and survival in a glucose- and linoleic-acid free medium. 6-O-GL thus appeared to be a bi-functional nutrient, ensuring both proper fibre quality and production by the hair follicle.     

基于气相色谱法的油酸甲酯和亚油酸甲酯热氧化降解特性研究

利用气相色谱法分别测定油酸甲酯和亚油酸甲酯在不同温度下的氧化曲线,同时采用微分法和积分法对热氧化降解反应方程的参数进行了计算,进而确定了反映油酸甲酯和亚油酸甲酯热氧化降解历程的宏观反应动力学方程。微分法动力学分析结果表明:油酸甲酯热氧化降解反应的平均反应级数为1.37,活化能为5.48 k J/mol,反应动力学模型为rA=-dcA/dt=7.06exp(-5.48/RT)c1.37A;亚油酸甲酯热氧化降解反应的平均反应级数为2.49,活化能为392.73 k J/mol,反应动力学模型为rA=-dcA/dt=1.13×1047exp(-392.73/RT)c2.49A。积分法动力学分析结果表明:当反应级数n=1时,油酸甲酯热氧化降解反应的活化能为27.68 k J/mol,反应动力学模型为rA=-dcA/dt=1 690.55exp(-27.68/RT)cA,亚油酸甲酯热氧化降解反应的活化能为107.04 k J/mol,反应动力学模型为rA=-dcA/dt=2.20×1013exp(-107.04/RT)cA;当反应级数n≠1时,油酸甲酯热氧化降解反应的平均反应级数为1.45,活化能为31.29 k J/mol,反应动力学模型为rA=-dcA/dt=369.19exp(-31.29/RT)c1.45A,亚油酸甲酯热氧化降解反应的平均反应级数为1.60,活化能为108.90 k J/mol,反应动力学模型为rA=-dcA/dt=9.27×1013exp(-108.90/RT)c1.60A。积分法得到的活化能数值更为接近,因此更适合研究油酸甲酯和亚油酸甲酯的热氧化降解反应动力学。     

麦角甾醇酯的酶促合成及对非酒精性脂肪肝的预防作用

探究了麦角甾醇亚油酸酯（简称麦角甾醇酯）的酶促合成及对非酒精性脂肪肝的预防作用。将30只雄性昆明小鼠分为四组：空白组（n=6）、高脂组（n=8）、麦角甾醇组（n=8）和麦角甾醇亚油酸酯组（n=8）,持续喂养6周。测定血浆总胆固醇（TC）、甘油三酯（TG）、低密度脂蛋白胆固醇（LDL-C）和高密度脂蛋白胆固醇（HDL-C）水平,计算LDL-C/HDL-C比值,检测肝脏和粪便脂质水平,并分析肝脏脂肪变性程度。结果显示,以Candida sp. 99-125脂肪酶为催化剂可以成功合成麦角甾醇亚油酸酯。麦角甾醇酯使得肝脏总脂肪酸含量降低35.3%（P<0.05）,可以有效预防高脂膳食诱导肝脏脂肪变性,并导致粪便总脂肪酸水平增加74.8%（P<0.05）。同时,麦角甾醇酯降低了血浆LDL-C水平和LDL-C/HDL-C比值分别为24.3%（P<0.05）和36.5%（P<0.05）,引起血浆HDL-C水平提高52.0%（P<0.05）。以上结果表明,麦角甾醇酯能够有效预防高脂膳食诱导的非酒精性脂肪肝。该文为非酒精性脂肪肝的预防提供了一种新的干预策略。     

New manganese-based catalyst systems for alkyd paint drying

The autoxidation and oligomerisation of ethyl linoleate (EL) catalyzed by manganese salts in combination with several Schiff-base ligands has been studied making use of time-resolved FT-IR spectroscopy. The results indicate that several of the combinations exhibit relatively high catalytic activity for the autoxidation of EL. One of the catalyst systems was studied in more detail. The reaction between MnCl₂·2H₂O and the Schiff-base ligand (L4) formed by the condensation of 2-pyridinealdehyde and 2-aminopyridine has been studied to clarify the catalytic reaction process. It was found that the Schiff-base ligand L4 reacts with water and the tridentate ligand (2-pyridyl)(2-pyridylamino)methanol (HOL4) is formed. A single crystal structure of [Mn^III(OL4)₂]Cl·3H₂O has been determined by X-ray diffraction methods.     

Effect of Spray-Dried Flavonoid Microparticles on Oxidative Stability of Methyl Linoleate as Lipid Model System

Microencapsulated quercetin (Q) and epicatechin (E) were prepared by spray-drying using inulin (IN) as encapsulating agent (Q–IN and E–IN) as well as with Capsul (C) as channelizing agent (Q–IN–C and E–IN–C). Microparticles were added to methyl linoleate (ML) and results showed that Q microparticles markedly improved its oxidative stability by increasing the induction period values and delaying the formation of oxidation compounds, as determined by high-performance size-exclusion chromatography, with respect to E microparticles, thus suggesting the importance of flavonoid C-ring substitution. Remaining levels of Q in the lipid system throughout oxidation of ML added with Q microparticles seemed to show two releasing zones: the first one corresponds to the equilibrium zone, when Q released from microparticles replaces Q that is being degraded; the second zone corresponds to the degradation of Q, when the release rate of the encapsulated Q is slower than its degradation rate. In contrast, E microparticles showed only one zone corresponding to the release of surface E. The end of the induction period was in line with the exhaustion of Q and E and the initiation of formation of advanced oxidation products (polymers). In conclusion, Q microparticles have a potential application to extend the shelf-life of lipid matrixes.     

复合催化剂在油酸豆甾醇酯合成中的应用

以油酸和豆甾醇为原料,研究了以硫酸氢钾-金属氧化物为组合的复合催化剂在酯化合成中的应用。首先,通过与其他硫酸盐的酯化效果进行比较,筛选出KHSO4是适用于酯化合成中高效且安全的催化剂,并将其和不同的金属氧化物进行组合作为复合催化剂进一步探究酯化效果。通过实验结果比较,得到KHSO4-Zn O作催化剂的酯化率最高。然后,将KHSO4-Zn O作为复合催化剂,针对催化剂用量、反应温度、反应时间、酸醇摩尔比等因素进行考察,探究油酸和豆甾醇的最佳酯化条件。得到最佳工艺条件为:在通高纯氮气条件下,选用3.0%KHSO4+1.0%Zn O(以豆甾醇的质量分数计)为催化剂,油酸和豆甾醇的摩尔比为1.8:1,反应的温度为150℃,反应的时间为7 h,酯化率达到92.17%。本工艺利用KHSO4-Zn O作为复合催化剂,得到较高的酯化率,实现了一条合成油酸豆甾醇酯的新工艺路线。