Comparison of the phenolic-dependent antioxidant properties of coconut oil extracted under cold and hot conditions

The antioxidant activities of coconut oil extracted under hot and cold conditions were compared. The coconut oil extracted under hot conditions (HECO) contained more phenolic substances than the coconut oil extracted under cold conditions (CECO). The antioxidant potential of HECO was higher than that of CECO as demonstrated by DPPH assay, deoxyribose assay and in vivo assay of serum antioxidant capacity. It is the common belief that virgin coconut oil extracted under cold conditions preserves several thermally unstable antioxidants and, as a result, better beneficial qualities can be expected for virgin coconut oil. However, high temperatures used in the hot extraction of coconut oil favour the incorporation of more thermally stable phenolic antioxidants into coconut oil. Therefore, the consumption of HECO may result in the better improvement of antioxidant related health benefits compared with the consumption of CECO.     

空心钛硅分子筛在二甲基硫醚液相氧化反应中的催化性能

在以过氧化氢为氧化剂的二甲基硫醚液相氧化反应体系中,对空心钛硅分子筛（HTS）的催化性能进行了系统研究,详细考察了催化剂存在与否以及催化剂用量、反应时间、反应物料配比及溶剂用量等不同反应条件变化对二甲基硫醚温和液相氧化反应的影响。研究发现,在温和反应条件下,HTS催化二甲基硫醚氧化反应中主要产物是二甲基亚砜和二甲基砜。经优化后,能够获得较好的氧化二甲基硫醚制备二甲基亚砜的反应效果,在二甲基硫醚转化率超过99%的情况下,二甲基亚砜选择性可达95%以上。     

New hydrogels based on maleilated collagen with potential applications in tissue engineering

New hydrogels based on maleic anhydride (MA) modified collagen were prepared with the aim of overcoming the high degradation rate displayed by collagen that is not otherwise chemically crosslinked. Semi-interpenetrated matrices were obtained by free radical polymerization of maleilated collagen (CM) and 2-hydroxyethyl methacrylate (HEMA) in the presence of ammonium persulfate (APS) and N,N,N′,N′-tetramethylethylenediamine (TEMED) as initiating system. The resulting matrices (CMH) had a sharp decrease in degradation, when compared to pure collagen. FTIR and H¹ NMR spectroscopies were used to confirm the incorporation of MA on the collagen peptide chains. The final composition of CMH was found to be strongly dependent by the concentration of maleilated collagen. The morphology of the hydrogels was studied by Scanning electron microscopy (SEM) and the macro-gel structure was confirmed. Water uptake of the synthetised hydrogels is influenced by both composition and the porosity of the matrices.     

大米支链淀粉在二甲亚砜溶液中的分子构象

从糯米、籼米和粳米3种类型大米中分离提取支链淀粉,采用特征黏度法和激光光散射法研究支链淀粉在二甲亚砜(DMSO)纯溶液和DMSO水溶液中的分子构象。结果表明：籼米、粳米支链淀粉的分子特性较为相似,均与糯米支链淀粉的分子特性有较大差异。以糯米支链淀粉的重均分子质量和旋转半径最大,分支度最高,交点质量浓度最小,分子链更易伸展。大米支链淀粉在DMSO中的分子构象与DMSO水溶液的体积分数以及自身的重均分子质量、分支度和质量浓度有关。在DMSO纯溶液中,大米支链淀粉的分子构象接近球形。在DMSO水溶液中,籼米和粳米支链淀粉的分子构象几乎不受自身质量浓度影响,均接近星形;而糯米支链淀粉分子构象受自身质量浓度影响较大,在极低质量浓度条件下表现为硬球结构,稍高质量浓度条件下表现为柔性球结构。     

复合固体酸SO4^2-／Fe2O3-TiO2催化合成环己酮缩乙二醇

以复合固体酸SO4^2-／Fe2O3-TiO2为多相催化剂,通过环己酮和乙二醇反应合成了环己酮缩乙二醇。探讨SO4^2-／Fe2O3-TiO2对缩酮反应的催化活性,较系统地研究了酮醇物质的量比,催化剂用量,反应时间诸因素对产品收率的影响。实验表明：SO4^2-／Fe2O3-TiO2是合成环己酮缩乙二醇的良好催化剂,在酮醇物质的量比为1：1．5,催化剂用量为反应物料总质量的2％,带水剂选用环己烷,反应时间1．5h的条件下,环己酮缩乙二醇的收率可达92．7％。     

O-邻氟苯甲基羟胺盐酸盐的合成

以丙酮肟和邻氟氯苄为原料合成了O-2-氟苯甲基丙酮肟醚,再用盐酸水解得到了O-2-氟苯甲基羟胺盐酸盐。文章系统研究了反应温度、不同溶剂、溶剂含水量等各种实验因素对O-2-氟苯甲基丙酮肟醚的影响,研究了盐酸浓度、水解温度等因素对O-2-氟苯甲基丙酮肟醚水解工艺的影响。两步收率最高分别为92.3%和87.3%。并用核磁等对产品及中间体进行了表征。     

A phenolic antioxidant from the Pacific oyster (Crassostrea gigas) inhibits oxidation of cultured human hepatocytes mediated by diphenyl-1-pyrenylphosphine

3,5-Dihydroxy-4-methoxybenzyl alcohol (DHMBA), an antioxidant isolated from the Pacific oyster (Crassostrea gigas), was studied in a cell-based fluorometric antioxidant assay using human hepatocyte-derived cells (C3A) and diphenyl-1-pyrenylphosphine (DPPP) as a fluorescent probe. In comparison with two hydrophilic antioxidants, DHMBA showed the stronger inhibition of DPPP-mediated fluorescence than chlorogenic acid and l-ascorbic acid: at a concentration of 320 μM of DPPP, the inhibition was 26.4 ± 2.6%, 11.1 ± 1.2%, and 0 ± 2.0% for DHMBA, chlorogenic acid, and l-ascorbic acid, respectively (mean ± SD, n = 4). Their relative oxygen radical absorbance capacities (ORAC) were dissociated with their cell-based antioxidant activities: 1.47 ± 0.40, 4.57 ± 0.30, and 0.53 ± 0.13 μmol TE/μmol for DHMBA, chlorogenic acid, and l-ascorbic acid, respectively (mean ± SD, n = 4). The amphiphilicity of DHMBA was better than chlorogenic acid and l-ascorbic acid might underlie this dissociation. Since the C3A cells are human hepatoma-derived cells, DHMBA might be useful in the prevention and treatment of liver diseases by involving an oxidation process.     

Neriifolin S, a dimeric serine protease from Euphorbia neriifolia Linn.: Purification and biochemical characterisation

A dimeric serine protease Neriifolin S of molecular mass 94 kDa with milk clotting activity has been purified from the latex of Euphorbia neriifolia by anion exchange and size-exclusion chromatography. It hydrolyses peptidyl substrates l-Ala-pNA with highest affinity (K_m of 0.195 mM) and physiological efficiency (K_cat/K_m of 144.5 mM s). Enzyme belongs to the class of neutral proteases with pI value of 6.8, optimal proteolytic activity displayed at pH 9.5 and temperature 45 °C. Its proteolytic activity is strongly stimulated in the presence of Ca⁺² ions and exclusively inhibited by serine protease inhibitors. Enzyme is fairly stable toward chemical denaturants, pH and temperature. The apparent T_m, was found to be 65 °C. Thermal inactivation follow first order kinetics with activation energy (Ea), activation enthalpy (ΔH∗), free energy change (ΔG∗) and entropy (ΔS∗) of 27.54 kJ mol⁻¹, 24.89 kJ mol⁻¹, −82.34 kJ mol⁻¹ and 337.20 J mol⁻¹ K⁻¹.     

Silicate-based polymer-nanocomposite membranes for polymer electrolyte membrane fuel cells

Proton-exchange membrane fuel cells have emerged as a promising emission free technology to fulfill the existing power requirements of the 21st century. Nafion^® is the most widely accepted and commercialized membrane to date and possesses excellent electrochemical properties below 80 °C, under highly humidified conditions. However, a decrease in the proton conductivity of Nafion^® above 80 °C and lower humidity along with high membrane cost has prompted the development of new membranes and techniques. Addition of inorganic fillers, especially silicate-based nanomaterials, to the polymer membrane was utilized to partially overcome the aforementioned limitations. This is because of the lower cost, easy availability, high hydrophilicity and higher thermal stability of the inorganic silicates. Addition of silicates to the polymer membrane has also improved the mechanical, thermal and barrier properties, along with water uptake of the composite membranes, resulting in superior performance at higher temperature compared to that of the virgin membrane. However, the degrees of dispersion and interaction between the organic polymer and inorganic silicates play vital roles in improving the key properties of the membranes. Hence, different techniques and solvent media were used to improve the degrees of nanofiller dispersion and the physico-chemical properties of the membranes. This review focuses mainly on the techniques of silicate-based nanocomposite fabrication and the resulting impact on the membrane properties.     

凹凸棒负载型SO4^2-／TiO2光催化降解茜素红染料的实验研究

凹凸棒负载型SO4^2-／TiO2固体超强酸对茜素红染料进行光催化降解反应,考察了体系pH、固体超强酸加量、紫外灯照射时间、强度及染料初始浓度对光催化降解过程的影响,确定了最佳实验条件：固体超强酸催化剂加量2．0g／L,光照距离12em,茜素红溶液初始浓度60mg／L,反应时间2．5h。