Oxidation of tartronic acid and dihydroxyacetone to sodium mesoxalate mediated by TEMPO

Using catalytic TEMPO with bleach as regenerating oxidant in water tartronic acid (TA) and dihydroxyacetone (DHA) are converted to mesoxalic (ketomalonic) acid. The DHA oxidation results in partial degradation of the reaction product, while conversion of tartronic acid is complete providing another viable chemical route to a potent hypoglycemic agent starting from relevant commercial products.     

Syntheses of some polyunsaturated sulfur- and oxygen-containing fatty acids related to eicosapentaenoic and docosahexaenoic acids.

With the aim of enhancing selectively the beneficial biological effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) a number of polyunsaturated fatty acids containing sulfur or oxygen atoms in the chain has been synthesized starting from EPA and DHA, respectively. Oxidative degradation of these acids led to the corresponding aldehydes all-(Z)-3,6,9,12-pentadecatetraenal and all-(Z)-3,6,9,12,15-octadecapentaenal. Reactions with DBU converted these aldehydes quantitatively into the conjugated isomers (2E,6Z,9Z,12Z)-pentadecatetraenal and (2E,6Z,9Z,12Z,15Z)-octadecapentaenal, respectively. The four aldehydes were transformed by a sequence of reactions comprising reduction to the alcohols, halogenation and substitution with mercapto esters into the corresponding sulfur containing polyunsaturated fatty acid esters. The oxygen containing esters were prepared from the respective alcohol by boron trifluoride catalysed reaction with ethyl diazoacetate.     

中性溶液中抗坏血酸在六氰合亚铁酸钴铜膜修饰铂电极上现场红外光谱电化学研究

抗坏血酸 ( AA)是生物化学和生物医学中的一种重要生理物质 ,因而在电催化和电化学传感器领域得到了广泛的研究 .对抗坏血酸的研究主要集中在两个方面 :一方面是研究 AA在各种电极上的电氧化机理、动力学参数及电催化机理 [1,2 ] ;另一方面是为了监测各种生物化学和生物医学中 AA的浓度发展起来的 AA传感器 .利用碳电极的各种预处理方法 [3,4 ]以及利用各种化学修饰电极 [5,6 ]来促进AA的电氧化动力学过程及解决 AA与各种共存物如多巴胺及脲酸等之间的相互干扰问题 .六氰合亚铁酸钴铜修饰电极 ( Co Cu HCF/Pt) [7] 在中性溶液中十分…     

mPEG-PLA共聚物胶束对DHA的增溶及光保护作用

以聚乙二醇单甲醚(mPEG)和外消旋丙交酯(D,L-LA)为原料,采用开环聚合法合成聚乙二醇单甲醚-聚乳酸(mPEG-PLA)共聚物,并用溶剂挥发法制备包载双氢青蒿素(DHA)的共聚物胶束(DHA/mPEG-PLA)。利用红外光谱(FT-IR)、核磁共振氢谱(1 H-NMR)和接触角测量仪研究了共聚物的结构和性质;利用激光粒度分析仪和扫描电镜(SEM)研究了胶束的粒径和形貌。结果表明mPEG-PLA共聚物的临界胶束浓度(CMC)为7.71mg/L。DHA/mPEG-PLA共聚物胶束呈球形,平均粒径(118.1±1.9)nm,载药量和包封率分别为(2.7±0.1)%和(77.1±0.3)%。胶束对DHA的水相表观溶解度增大约1.5倍。紫外光光照39h,纯DHA在混悬液中降解率达37%且持续增长,胶束中DHA降解率达到10%后基本保持不变。     

Aalysis of the fatty acid composition of the lipid classes in human blood serum under normal diet and when supplemented with fish oil

Total lipids have been extracted from human serum with chloroform–methanol 2:1 (v/v) and separated into individual classes by TLC. After transesterification the fatty acid methyl esters were analyzed by capillary gas chromatography on an FFAP column. The quantitation of ω-3 fatty acids has been performed using internal and external standards. Internal lipid standards for each lipid class were carried throughout the entire analytical procedure. Under normal diet eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are incorporated into the lipid classes to different extents: cholesterol esters; EPA, 6.5 ± 1.9 γ/ml serum; DHA, 4.3 ± 1.9 μg/ml: phospholipids; EPA, 5.9 ± 2.7 μg/ml; DHA, 31.8 ± 8.1 μg/ml. Fish oil supplementation leads to a 4 to 6-fold rise in EPA and to an approximately 2-fold rise in DHA.     

毛细管气相色谱法测定深海鱼油中的EPA和DHA含量

用氢氧化钾－甲醇酯化法将深海鱼油中的脂肪酸快速、有效地转化成脂肪酸甲酯,然后进行毛细管气相色谱法测定,以二十二碳饱和脂肪酸甲酯为内标物,建立了5,8,11,14,17－二十碳五烯酸（EPA）和4,7,10,13,16,19－二十二碳六烯酸（DHA）的定量分析方法,并用于实际样品分析。该方法对EPA和DHA定量分析的相对标准偏差分别为4．6％和5．0％,回收率分别为99．7％和99．4％。     

Isolation and structural analysis of the cyclic fatty acid monomers formed from eicosapentaenoic and docosahexaenoic acids during fish oil deodorization

Long-chain polyunsaturated fatty acids (LC-PUFAs) present in fish oils are thermolabile molecules. Among the degradation reactions encountered, thermal cyclization occurs during refining or other heat treatments. Numerous studies have been carried out in the past to quantify and determine the structures of cyclic fatty acid monomers (CFAMs) formed from oleic, linoleic and linolenic acids in heated vegetable oils. Recently, much attention have been given to LC-PUFAs due to their potential health benefits. However, data on quantification of CFAMs formed from these fatty acids, such as eicosapentaenoic acid (EPA, cis-5, cis-8, cis-11, cis-14, cis-17 20:5) and docosahexaenoic acid (DHA, cis-4, cis-7, cis-10, cis-13, cis-16, cis-19 22:6), the two main LC-PUFAs in fish oils, are scarce. In the present study, structural analyses of CFAMs formed from EPA and DHA during the deodorization of fish oil are presented. Fish oil sample was deodorized at 250 degrees C for 3 h under a pressure of 1.5 mbar in a laboratory deodorizer. The CFAMs formed during heat treatment of fish oil were isolated by a combination of saponification, esterification, urea fractionations and column chromatography. Structural analyses of C20- and C22-CFAMs were achieved by gas-chromatography electronic-ionization mass-spectrometry (GC-EI-MS) of their 4,4-dimethyloxazoline (DMOX) derivatives. We identified seven out of 13 possible structures of hydrogenated CFAMs formed from EPA, and nine out of 16 possible structures of CFAM formed from DHA. Major CFAMs from both EPA and DHA were cyclohexyl isomers. All possible cyclohexyl isomers were found but only nine out of 18 of the cyclopentyl isomers were present in concentration sufficient for identification. Chemical mechanisms involved in the formation of polyunsaturated LC-PUFAs have been investigated. The results have shown that general principle involved in the cyclization of LC-PUFAs is same as that for the thermal cyclization of oleic, linoleic and alpha-linolenic acids.     

Polyunsaturated docosahexaenoic vs docosapentaenoic acid-differences in lipid matrix properties from the loss of one double bond

Insufficient supply to the developing brain of docosahexaenoic acid (22:6n3, DHA), or its omega-3 fatty acid precursors, results in replacement of DHA with docosapentaenoic acid (22:5n6, DPA), an omega-6 fatty acid that is lacking a double bond near the chain's methyl end. We investigated membranes of 1-stearoyl(d(35))-2-docosahexaenoyl-sn-glycero-3-phosphocholine and 1-stearoyl(d(35))-2-docosapentaenoyl-sn-glycero-3-phosphocholine by solid-state NMR, X-ray diffraction, and molecular dynamics simulations to determine if the loss of this double bond alters membrane physical properties. The low order parameters of polyunsaturated chains and the NMR relaxation data indicate that both DHA and DPA undergo rapid conformational transitions with correlation times of the order of nanoseconds at carbon atom C(2) and of picoseconds near the terminal methyl group. However, there are important differences between DHA- and DPA-containing lipids: the DHA chain with one additional double bond is more flexible at the methyl end and isomerizes with shorter correlation times. Furthermore, the stearic acid paired with the DHA in mixed-chain lipids has lower order, in particular in the middle of the chain near carbons C(10)(-)(12), indicating differences in the packing of hydrocarbon chains. Such differences are also reflected in the electron density profiles of the bilayers and in the simulation results. The DHA chain has a higher density near the lipid-water interface, whereas the density of the stearic acid chain is higher in the bilayer center. The loss of a single double bond from DHA to DPA results in a more even distribution of chain densities along the bilayer normal. We propose that the function of integral membrane proteins such as rhodopsin is sensitive to such a redistribution.     

Morphology dependent electrocatalytic activity of Au nanoparticles

The electrocatalytic activity of spherical shape Au particles chemically grown on a sol–gel derived 3D silicate network modified conducting surface has been studied using ascorbate as a model. The nanostructured Au particles show morphology dependent electrocatalytic activity towards ascorbate. Unusual voltammetric behavior for ascorbate has been observed. Unlike the polycrystalline Au electrode, the nanostructured electrode shows two well defined voltammetric peaks for ascorbate at 0 and 0.3 V in neutral and alkaline pHs. These voltammetric peaks are assigned for the oxidation of ascorbate to dehydroascorbate (DHA) and the further oxidation of 2,3-diketogluonic acid (DKG), the hydrolyzed product of DHA. The voltammetric peak corresponding to the oxidation of DKG is very sensitive to the supporting electrolyte anions and solution pH. Voltammetric behavior of DHA has been investigated to support the oxidation pathway of ascorbate on the nanostructured electrode. Surface morphology of the particle controls the electrocatalytic activity.     

Analysis of polyunsaturated fatty acids in blood serum after fish oil administration.

Free and total fatty acids in the blood serum of patients with hyperlipoproteinemia have been analysed as their methyl esters by capillary gas chromatography using an FFAP column. In one-step reactions the free fatty acids in serum react with methanol-acetyl chloride (50:1, v/v) at 25 degrees C, the total fatty acids (free plus esterified) are transesterified with methanol-toluene-acetyl chloride (8:2:1, v/v) at 100 degrees C. The quantification of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is based on an internal standard (13,16,19-docosatrienoic acid) and on calibration standards. Under normal diet the concentrations of EPA and DHA are as follows (mean +/- S.D., n = 27): free EPA, 0.2 +/- 0.1 mg/dl; free DHA, 0.6 +/- 0.2 mg/dl; total EPA, 3.6 +/- 2.1 mg/dl; total DHA 11.4 +/- 3.1 mg/dl. Under a fish oil intake of 9 g per day, free and total EPA concentrations rise by ca. five- to six-fold, and free and total DHA concentrations by ca. two-fold.     

Effects of Dietary α-Linolenic Acid Treatment and the Efficiency of Its Conversion to Eicosapentaenoic and Docosahexaenoic Acids in Obesity and Related Diseases

The essential fatty acid alpha-linolenic acid (ALA) is present in high amounts in oils such as flaxseed, soy, hemp, rapeseed, chia, and perilla, while stearidonic acid is abundant in echium oil. ALA is metabolized to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) by desaturases and elongases in humans. The conversion of ALA to EPA and DHA is limited, and these long-chain n−3 polyunsaturated fatty acids (PUFAs) are mainly provided from dietary sources (fish and seafood). This review provides an overview of studies that explored the effects of dietary supplementation with ALA in obesity and related diseases. The obesity-associated changes of desaturase and elongase activities are summarized, as they could influence the metabolic conversion of ALA. Generally, supplementation with ALA or ALA-rich oils leads to an increase in EPA levels and has no effect on DHA or omega-3 index. According to the literature data, stearidonic acid could enhance conversion of ALA to long-chain n−3 PUFA in obesity. Recent studies confirm that EPA and DHA intake should be considered as a primary dietary treatment strategy for improving the omega-3 index in obesity and related diseases.     

甲鱼油脂肪酸组成的研究

用热提取方法抽取出甲鱼油，用ＫＯＨ－ＣＨ３ＯＨ酯交换法甲酯化处理，以色谱／质谱方法测定脂肪酸的组成。共鉴定出２１种脂肪酸，其中以棕榈酸、棕榈油酸、硬脂酸、油酸、亚油酸、二十碳五烯酸（ＥＰＡ）、二十二碳五烯酸（ＤＨＡ）为主     

Electrochemical Sensor Based on Oxidation of 2,8‐Dihydroxyadenine to Monitor DNA Damage in Calf Thymus DNA

A novel and reliable direct electrochemical method has been established to monitor DNA damage in acid hydrolyzed calf thymus DNA, based on the determination of 2,8‐dihydroxyadenine (2,8‐DHA). A single‐wall carbon nanotubes (SWCNT) modified edge plane pyrolytic graphite electrode (EPPGE) has been used as a sensor to monitor the DNA damage. 2,8‐DHA the main in vivo adenine oxidation product undergoes oxidation at ～395 mV at SWCNT modified EPPGE using square wave voltammetry (SWV). The sensor exhibits potent and persistent electron‐mediating behavior. A well‐defined oxidation peak for the oxidation of 2,8‐DHA was observed at modified electrode with lowering of peak potential and increase in peak current as compared to bare EPPGE. At optimal experimental conditions, the catalytic oxidative peak current was responsive with the 2,8‐DHA concentrations ranging from 0.05 nM to 100 nM. The detection limit was 3.8×10^?11 M and limit of quantification was 1.27×10^?10 M. The modified electrode exhibited high stability and reproducibility.     

Chromophores from hexeneuronic acids: chemical behavior under peroxide bleaching conditions

Hexeneuronic acids (HexA) are a major cause of discoloration (yellowing/brightness reversion) in pulps from xylan-containing wood, being generated from the xylan’s 4-O-methylglucuronic acid residues. The HexA-derived chromophores, whose identification and structure confirmation have been described in the previous part of this series (Rosenau et al. in Cellulose, 2017), were subject to conditions of peroxide bleaching, i.e. treatment with hydrogen peroxide in alkaline medium. These chromophores, ladder-type oligomers of mixed aromatic-quinoid and mixed furanoid-benzoid character, are degraded relatively quickly to one major product, 2,5-dihydroxy-[1,4]-benzoquinone (DHBQ), and a minor component, 2,5-dihydroxyacetophenone (DHA). These two compounds, which have already been identified as two of the three key chromophores (besides 5,8-dihydroxy-[1,4]-naphthoquinone, DHNQ) in aged cellulosics, are potent chromophores themselves and are subsequently more slowly degraded to non-colored degradation products, according to pathways already described in previous parts of this series. The occurrence of DHBQ and DHA in the bleaching treatment of the HexA-derived chromophores establishes the link between HexA chemistry and the key chromophore classes of residual chromophores found in aged cellulosic materials.     

Study on fluorescent property of degrading products of piperacillin and its analytical application

The fluorimetric property of the degrading products of piperacillin has been studied in detail. The studies on degrading pH, degrading time, detection alkalinity and other corresponding analytical parameters of acid degradation have been made. Then fluorometry of piperacillin was established by producing its stable fluorescent products. The detection limit for acid degradation analytical method is 2.34 ng/ml, the linear range is 7.80-4.0 x 10(2) ppb. The analytical sensitivity, precision and stability of degrading products of acid degradation are satisfactory, which has been used for the determination of the trace piperacillin in human serum and urine with satisfactory results.     

Control Mechanism for Carbon‐Chain Length in Polyunsaturated Fatty‐Acid Synthases

Polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are essential fatty acids. PUFA synthases are composed of three to four subunits and each create a specific PUFA without undesirable byproducts. However, detailed biosynthetic mechanisms for controlling final product profiles have been obscure. Here, the bacterial DHA and EPA synthases were carefully dissected by in vivo and in vitro experiments. In vitro analysis with two KS domains (KS_A and KS_C) and acyl‐acyl carrier protein (ACP) substrates showed that KS_A accepted short‐ to medium‐chain substrates while KS_C accepted medium‐ to long‐chain substrates. Unexpectedly, condensation from C₁₈ to C₂₀, the last elongation step in EPA biosynthesis, was catalyzed by KS_A domains in both EPA and DHA synthases. Conversely, condensation from C₂₀ to C₂₂, the last elongation step for DHA biosynthesis, was catalyzed by the KS_C domain in DHA synthase. KS_C domains therefore determine the chain lengths.     

Biocompatible hydrogel for cartilage repair with adjustable properties

Synthesis of hydrogel at mild conditions is considered one most important challenge, especially if the hydrogel will be used for hosting bioactive materials or drugs. The procedure of hydrogel preparation should have no effect on the properties of the hosted materials. Hyaluronic acid (HA) was modified by adding dialdehyde groups to its structure to facilitate formation of hydrogel at very mild conditions. Dialdehyde HA (DHA) was prepared through oxidation of HA using sodium metaperiodate as oxidizing agent. The prepared DHA was characterized by Fourier‐transform infrared (FTIR) spectroscopy and X‐ray diffraction (XRD) and aldehyde content. A hydrogel was prepared using different chitosan/DHA molar ratio and fixed amount of glutaraldehyde at 25°C. The prepared hydrogel has tunable properties and pores size depending on the chitosan/DHA molar ratio. Sodium diclofenac was loaded on the hydrogel as a model drug. The hydrogel was characterized by FTIR spectroscopy, swelling rate, gel fraction, drug release profile, and cytotoxicity. The results obtained indicated that the properties of the prepared hydrogel, including gelling time, gel fraction, swelling, pores size, and drug release profile are highly tuned depending on the chitosan/DHA molar ratio. The drug loading efficiency was in the range of 70% to 85%. The cytotoxicity results reveal that the prepared hydrogel has a very low toxicity in presence and absence of sodium diclofenac.     

Measurement of nitric oxide by 4,5-diaminofluorescein without interferences

The fluorescent reagent 4,5-diaminofluorescein (DAF-2) has been widely used for specific and quantitative measurements of nitric oxide (NO) in biological tissues. Recently it was reported that dehydroascorbic acid (DHA) and ascorbic acid (AA) interfere with the measurement of NO using DAF-2. A new method of assaying NO using DAF-2 eliminates these interferences; when frozen on dry ice, the NO in the original solution still diffuses and can react with an adjacent frozen block of DAF-2, but the confounding compounds such as DHA do not. Thus, placing the microliter-volume frozen blocks of solutions containing NO and the solutions of DAF-2 adjacent to each other for 30 min results in the concentration dependent formation of fluorescent product (DAF-2T) from the reaction of NO with DAF-2. The product has been characterized and the method validated using both fluorescence spectroscopy and capillary electrophoresis with laser induced fluorescence detection. With this approach, the presence of DHA and AA does not interfere with NO measurements, and product formation is inhibited in the presence of NO scavengers added to either of the solutions before freezing. The contactless DAF-2 method successfully assays NO in nitric oxide synthase-positive vertebrate and invertebrate tissues. This method allows nondestructive NO detection in biological samples that can subsequently be used for morphological and/or biochemical studies.     

In Vitro and In Vivo Digestibility of Soybean,Fish, and Microalgal Oils,and Their Influences on Fatty Acid Distribution in Tissue Lipid of Mice

The digestion rates of microalgal (docosahexaenoic acid, DHA, 56.8%; palmitic acid, 22.4%), fish (DHA, 10.8%; eicosapentaenoic acid, EPA, 16.2%), and soybean oils (oleic, 21.7%; linoleic acid, 54.6%) were compared by coupling the in vitro multi-step and in vivo apparent digestion models using mice. The in vitro digestion rate estimated based on the released free fatty acids content was remarkably higher in soybean and fish oils than in microalgal oil in 30 min; however, microalgal and fish oils had similar digestion rates at longer digestion. The in vivo digestibility of microalgal oil (91.49%) was lower than those of soybean (96.50%) and fish oils (96.99%). Among the constituent fatty acids of the diet oils, docosapentaenoic acid (DPA) exhibited the highest digestibility, followed by EPA, DHA, palmitoleic, oleic, palmitic, and stearic acid, demonstrating increased digestibility with reduced chain length and increased unsaturation degree of fatty acid. The diet oils affected the deposition of fatty acids in mouse tissues, and DHA concentrations were high in epididymal fat, liver, and brain of mice fed microalgal oil. In the present study, microalgal oil showed lower in vitro and in vivo digestibility, despite adequate DHA incorporation into major mouse organs, such as the brain and liver.     

Vesicles from docosahexaenoic acid

In dilute aqueous solution and at room temperature, cis-4,7,10,13,16,19-docosahexaenoic acid (DHA) self-assembles into vesicles (self-closed bilayers), if the molar ratio of the neutral form of DHA to anionic DHA is kept between 1:1 and 1:3 (corresponding to a bulk pH between 8.5 and 9.2 for a system with 10 mM DHA). By using polycarbonate membrane extrusion, stable unilamellar DHA vesicles with an average diameter of 80 nm can be prepared at pH 8.8. Cryo-transmission electron microscopy indicates that the width of the DHA bilayers in the vesicles is clearly below twice the length of an extended DHA molecule, indicating a high conformational flexibility of DHA within the vesicle bilayer. These DHA bilayers have a similar thickness like bilayers of vesicles prepared at pH 8.5 from oleic acid (cis-9-octadecenoic acid). Using calcein as fluorescent reference compound, it is shown that water-soluble molecules can be encapsulated inside DHA vesicles which may make them interesting for medical or food applications.