Biosynthesis of iso-fatty acids in myxobacteria

The fatty acid (FA) profiles of the myxobacteria Stigmatella aurantiaca and Myxococcus xanthus were investigated by acidic methanolysis of total cell extracts and GC or GC-MS analysis. The main components were 13-methyltetradecanoic acid (iso-15:0) and (Z)-hexadec-11-enoic acid (16:1, omega-5 cis). The biosynthesis of iso-FAs was investigated in several feeding experiments. Feeding of isovaleric acid (IVA) to a mutant impaired in the degradation of leucine to isovaleryl-CoA (IV-CoA)(bkd mutant) of M. xanthus only increased the amount of iso-odd FAs, whereas feeding of isobutyric acid (IBA) gave increased amounts only of iso-even FAs. In contrast, a bkd mutant of S. aurantiaca gave increased amounts of iso-odd and iso-even fatty acids in both experiments. We assumed that in S. aurantiacaalpha-oxidation takes place. [D(7)]-15-Methylhexadecanoic acid was synthesised and fed to S. aurantiaca as well as [D(10)]leucine and [D(8)]valine to elucidate this pathway in more detail. The iso-fatty acid was degraded by alpha- and beta-oxidation steps. [D(10)]Leucine was strongly incorporated into iso-odd and iso-even fatty acids, whereas the incorporation rates for [D(8)]valine into both types of fatty acids were low. Thus alpha-oxidation plays an important role in the biosynthesis of iso-fatty acids in S. aurantiaca. The incorporation rates observed after feeding of [D(10)]leucine and [D(8)]valine are the highest for iso-17:0 compared to the other acids. This indicates the central role of iso-17:0 in the biosynthesis of iso-FAs. The shorter homologues seem to be formed mainly by alpha-oxidation and beta-oxidation of this acid. After feeding of traces of unsaturated counterparts of this labelled FA occurred in the extracts indicating that desaturases are active in the biosynthesis of unsaturated fatty acids in S. aurantiaca.     

Extraction of dissolved fatty acids from sea water

Summary During a cruise in the Baltic Sea in March/April 1991, dissolved lipids were concentrated from acidified sea water by adsorption on reversed phase material; the free fatty acids in the lipids were isolated. Titration of the acids with 0.01 mol/l methanolic KOH resulted in a very poor titration curve; assessing total concentration of organic acids in sea water by base titration appears to be impractical. After derivatization with p-phenylphenacyl bromide under crown ether catalysis the fatty acids were analyzed by micro-bore HPLC with UV-detection and comparison with standard reference substances. Some unknown fatty acids were characterized by GC/MS. Total concentrations were in the range from 1 to 4.5 nmol/l. They were the same in parallel samples liquid/liquid extracted with dichloromethane. The HPLC spectra of the fatty acids in both kinds of samples were also quite similar. This confirms earlier observations that adsorptive concentration of dissolved fatty acids and non-polar lipids from sea water is as effective as liquid/liquid extraction. Higher amounts of fatty acids can be concentrated by adsorption from large water volumes, thus lowering detection limits. Palmitic acid had by far the highest concentration in every sample followed by myristic acid, lauric acid, and stearic acid. Palmitoleic acid and oleic acid were the most abundant unsaturated acids. The other saturated and unsaturated acids had medium to low concentrations.     

Gas chromatography of fatty acids.

Lipids in foods contain a wide variety of fatty acids differing in chain length, degree of unsaturation, position and configuration of double bonds and the presence of special functional groups. Modern capillary gas chromatography offers excellent separation of fatty acids. Fused-silica capillary columns with stationary phases of medium polarity and non-polar methylsilicone stationary phases successfully separate most of the natural fatty acids. Special applications, such as the separation of complex cis-trans fatty acid mixtures and cyclic fatty acids, required particular chromatographic conditions, including the use of very long capillary columns or more polar stationary phases. The derivatization methods for the preparation of fatty acid esters also need to be optimized to obtain accurate quantitative results. This paper reviews the derivatization techniques, capillary columns and stationary phases commonly used in the gas chromatography of fatty acids in food.     

植物油中脂肪酸不同定量方法的比较分析

比较峰面积归一化法与标准曲线法两种方法分析植物油中脂肪酸百分比含量的差异.利用气相色谱-质谱联用仪(GC-MS)检测10种市售食用植物油中的8种主要脂肪酸,峰面积归一化法和标准曲线法计算脂肪酸的百分比含量.结果表明,标准曲线法与峰面积归一化法相比,肉豆蔻酸、棕榈酸、十七烷酸、硬脂酸和棕榈油酸所占的百分比升高,而油酸、亚...     

Heterogeneous modification of various celluloses with fatty acids

Heterogeneous modification of various types of cellulose (microcrystalline cellulose, cellulose whiskers and regenerated cellulose) was performed with long-chain fatty acids by an esterification reaction. The differences in reactivity between the celluloses were studied as well as the influences of the chain length and double bond content of the fatty acids. The success of the modification reaction and the structure of modified samples were studied with diverse characterization methods. Surface modification changed the thermal stability of cellulose by decreasing the degradation temperature but also made the pyrolysis curve two-stepped due to the double bonds in the fatty acid chain. It was observed that the nature of the fatty acid affected the degree of substitution (DS). The longer the fatty acid chain was, the lower was the DS. Fatty acids with increased double bond content gave decreased DS. Regenerated cellulose seemed to have the highest surface reactivity due to the distinct morphological structure, which also led to a much lower quantity of fatty acids attached to the structure than for other modified cellulose particles. The mixture of tall oil fatty acids behaved in the same manner as the commercial fatty acids, proving to be an excellent “green” choice for this kind of application.     

GC-MS法快速测定茶叶中脂肪酸

建立了气相色谱-质谱联用技术(GC-MS)快速分析茶叶脂肪酸的新方法.对23批茶叶样品进行GC-MS分析,结合NIST 05谱库检索鉴定茶叶脂肪酸种类,并用峰面积归一化法测定其相对含量,比较不同加工方式的茶叶脂肪酸含量.结果表明,所有茶样中亚麻酸、亚油酸和棕榈酸含量最高,但绿茶和青茶脂肪酸含量高于发酵处理的红茶和黑茶.方法可以用于分析各种茶叶的脂肪酸,反映不同种类茶叶的性质差异.     

Antioxidant activity and fatty acids quantification in Sicilian purslane germplasm

Abstract

Portulaca oleracea is an annual succulent herb in the family Portulacaceae. It is a nutritious vegetable with high antioxidant properties and, it is among the richest plant source of ω-3 fatty acids, as well as a rich source of ω-6 fatty acids, ascorbic acid, tocopherols and beta-carotene. In the present study, three purslane populations under different Mediterranean environmental conditions for two years, for future valorization as novel food sources of omega-3 fatty acids, were evaluated. In particular, biomorphological characteristics, total phenols and fatty acids content were determined. The antioxidant activities were evaluated using 2,2-diphenyl-1-picrylhydrazyl assay. The population “Cas” appears to have higher antioxidant activity than the other two populations (“Cal” and “S. Ven”).The saturated fatty acid content is influenced only by the year of collection, while the polyunsaturated fatty acid by the populations. The most abundant unsatured fatty acids are linoleic and linolenic acids and “Cas” attained the highest contents.     

Analysis of tissue free fatty acids isolated by aminopropyl bonded-phase columns

Gas chromatographic analysis revealed that polyunsaturated fatty acids such as arachidonic acid and total tissue free fatty acids isolated from an aminopropyl bonded-phase column yield a two- to three-fold higher recovery of arachidonic acid as compared to those isolated from thin-layer chromatographic plates. This method was further improved by packing the aminopropyl bonded phase in glass columns, since the glass column significantly eliminated the other contaminants (from polypropylene columns) coeluting with fatty acids in both a neutral lipid thin-layer chromatographic system and on a 5% DEGS-PS column of gas chromatographic analysis. In aminopropyl bonded-phase columns, the standard triglycerides and phospholipids were completely separated from free fatty acids as judged by gas chromatographic analysis. These results warrant the use of an aminopropyl bonded-phase column for the isolation of free fatty acids to obtain better recovery of polyunsaturated fatty acids.     

Synthesis of benzophenone-containing fatty acids

Syntheses of new benzophenone-containing fatty acids (FABPs) 1, 5, and 6 and a new route to FABP 3 are described. Combined with the known 2 and 4, these FABPs comprise a set of photoactivatable fatty acid analogues with the crosslinking site at defined distances from the carboxylic acid hydroxyl group oxygen atoms ranging from 7.9 to 25.0 A.     

Conjugated ketonic fatty acids from Pleurocybella porrigens

Three novel conjugated long-chain fatty acids (1-3) were obtained from aqueous methanol extracts of Pleurocybella porrigens together with nine known constituents including (8E,10E)-7,12-dioxo-8,10-octadecadienoic acid (ostopanic acid) (4). The structures of the new fatty acids were characterized as (14RS)-(10E,12E)-14-hydroxy-9-oxo-10,12-octadecadienoic acid (1), (12RS)-(8E,10E)-12-hydroxy-7-oxo-8,10-octadecadienoic acid (2), and (10E,12E)-9,14-dioxo-10,12-octadecadienoic acid (3) by spectroscopic methods.     

扁桃油中脂肪酸组成的GC-MS法分析

以正己烷为提取剂,采用超声法提取油脂,经KOH-甲醇甲酯化处理后,以气相色谱-质谱(GC-MS)联用技术鉴定出陕西蒲城3个品种扁桃油中的脂肪酸主要组成为:油酸、亚油酸、9-十六碳烯酸、硬脂酸、棕榈酸,其中不饱和脂肪酸总量占91.4%以上,主要成分油酸占73.3%以上。     

DNA-bound lipids: computer modeling of DNA interaction with stearic acid and unsaturated fatty acids

It was shown for the first time by computer experiments that fatty acids are strongly bound to DNA. This is consistent with the presence of free fatty acids in the specimens of DNA-bound lipids isolated from various cells. Binding of all fatty acids to the DNA minor groove is stronger than to the major groove, which is correlated with the presence of two pools of free fatty acids isolated from DNA specimens by biochemical methods. Since DNA polymerase is also bound to the DNA minor groove, fatty acids can play an important role in the regulation mechanism of DNA replication and signal transmission. The energy of interaction of fatty acids with DNA depends on both the number of double bonds and the geometric configuration of the fatty acid and the nucleotide composition of DNA. Dependence on the bond energy in the DNA—fatty acid complex on the nucleotide composition attests to the possibility of site-specific binding of lipids to DNA. On passing from a saturated fatty acid to unsaturated acids containing one, two, or three double trans-bonds, the bond energy of DNA with the fatty acid gradually decreases. The presence of one or three double cis-bonds results in weakening of the strength of the DNA—fatty acid complexes compared to those with the saturated acid. The strongest binding between DNA and fatty acid was found for the unsaturated acid with two double cis-bonds (linoleic). This can be explained by the fact that the bent (boomerang) shape of the molecule of this acid follows the curve of the DNA helix. The pattern of variation of the energy of DNA complexes with stearic, linoleic, oleic, and linolenic acids correlates with experimental data on the melting points of these complexes: the more stable the DNA—fatty acid complex, the lower the melting point of DNA.     

Mixed Langmuir monolayers of cholesterol and `essential' fatty acids

Langmuir monolayers of cholesterol and various fatty acids, such as stearic, oleic, linoleic, α-linolenic, and arachidonic acids, spread at the air/water interface are investigated. The system of cholesterol and stearic acid is found to be immiscible, with only one collapse, occurring at the same surface pressure for all composition range. However, surface pressure (π) – area (A) isotherms of cholesterol/unsaturated fatty acids show a characteristic course with two collapse states. The pressure of the first collapse varies with the proportion of the components in the mixture, while the second collapse, occurring at the surface pressure characteristic of cholesterol alone, is independent of mole fraction of the investigated fatty acid. The application of the surface phase rule indicates that the unsaturated fatty acids/cholesterol mixtures are miscible up to the surface pressure corresponding to the first collapse. Negative values of the excess free energy of mixing in all composition ranges prove that the mixtures are stable. The interactions existing in mixtures of cholesterol and unsaturated fatty acids possessing even numbers of double bonds are strongest in the lower region of fatty acid proportion, and the results are consistent with the minimum values of the excess free energy of mixing, indicating the most stable mixtures. For cholesterol and unsaturated fatty acids with odd numbers of double bonds the behavior is different, and the strongest interactions occur in both low and high regions of mole fraction of an acid. Received: 2 May 2000 Accepted: 26 October 2000     

Gas chromatographic analysis of infant formulas for total fatty acids, including trans fatty acids

Twelve powdered and 13 liquid infant formulas were analyzed by using an extension of AOAC Official Method 996.01 for fat analysis in cereal products. Samples were hydrolyzed with 8 N HCl and extracted with ethyl and petroleum ethers. Fatty acid methyl esters were prepared by refluxing the mixed ether extracts with methanolic sodium hydroxide in the presence of 14% boron trifluoride in methanol. The extracts were analyzed by gas chromatography. In powdered formulas, saturated fatty acid (SFA) content (mean +/- SD; n = 12) was 41.05 +/- 3.94%, monounsaturated fatty acid (MUFA) content was 36.97 +/- 3.38%, polyunsaturated fatty acid (PUFA) content was 20.07 +/- 3.08%, and total trans fatty acid content was 1.30 +/- 1.27%. In liquid formulas, SFA content (mean +/- SD; n = 13) was 42.29 +/- 2.98%, MUFA content was 36.05 +/- 2.47%, PUFA content was 20.65 +/- 2.40%, and total trans fatty acid content was 0.88 +/- 0.54%. Total fat content in powdered formulas ranged from 4.4 to 5.5 g/100 kcal and linoleic acid content ranged from 868 to 1166 mg/100 kcal. In liquid formulas, total fat content ranged from 4.1 to 5.1 g/100 kcal and linoleic acid content ranged from 820 to 1100 mg/100 kcal. There were no significant differences between powdered and liquid infant formulas in concentrations of total fat, SFA, MUFA, PUFA, or trans fatty acids.     

Separation and quantitation of fatty acids by high-performance liquid chromatography

To facilitate the determination of the fatty acid composition of tissues and the investigation of fatty acid metabolism, we developed a method for the rapid separation by high-performance liquid chromatography and quantitation (by ultraviolet light absorption) of p-bromophenyl esters of fatty acids which vary in chain length from 10 to 22 carbon atoms. The utility of the method was demonstrated by evaluating the fatty acid composition of human uterine decidua vera tissue and human endometrial stromal cells that are maintained in monolayer culture.     

Analysis of fatty acids in mouse cells using reversed-phase high-performance liquid chromatography

Summary A reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed to analyze various fatty acids in recombinant mouse L cells. These fatty acids were the metabolites of oleic acid. A process was developed to extract fatty acids from the cell samples before RP-HPLC analysis. The samples were first saponified with 0.5 M NaOH in 96% ethanol then extracted with acidified ethyl acetate. After extraction, the sample was dried and dissolved in HPLC-grade methanol. After centrifugation to remove insoluble impurities, the sample was applied to a C₁₈RP-HPLC column using a gradient of acetonitrile (ACN)-H₂O. The eluted fatty acids were monitored by ultraviolet (UV) absorption at 195 nm and identified by retention time and adsorption spectrum comparison. This method successfully resolved various fatty acids and provided a tool for the elucidation of the fatty acid metabolic pathway in the cells.     

Dual inhibition of mycobacterial fatty acid biosynthesis and degradation by 2-alkynoic acids

2-Hexadecynoic acid and 2-octadecynoic acid have cidal activity against Mycobacterium smegmatis and Mycobacterium bovis BCG. At subinhibitory concentrations, M. smegmatis rapidly transformed [1-(14)C]-2-hexadecynoic acid into endogenous fatty acids and elongated them into mycolic acids. Toxic concentrations of 2-hexadecynoic acid resulted in accumulation of 3-ketohexadecanoic acid, which blocked fatty acid biosynthesis, and 3-hexadecynoic acid, an inhibitor of fatty acid degradation. The combination of these two metabolites is necessary to achieve the inhibition of M. smegmatis. We conclude that 2- and 3-hexa/octadecynoic acids inhibit mycolic acid biosynthesis, fatty acid biosynthesis, and fatty acid degradation, pathways of significant importance for mycobacteria.     

气相色谱法测定中华绒螯蟹中脂肪酸组成与含量

中华绒螯蟹中脂肪酸组成与含量的测定对评估其营养价值与品质具有重要意义,但面对种类繁多的脂肪酸提取试剂和甲酯化试剂,测定结果参差不齐,很难对中华绒螯蟹中丰富的脂肪酸准确定量。研究通过比较4种常见的脂肪提取试剂、2种脂肪酸甲酯化试剂,确定以氯仿-甲醇(1∶1, v/v)为提取试剂,含2%硫酸的甲醇溶液为甲酯化试剂,建立了测定中华绒螯蟹肌肉中脂肪酸组成与含量的气相色谱分析方法。实验按照程序升温的条件,采用DM-2560毛细管色谱柱(100 m×0.25 mm×0.20 μm)分离37种脂肪酸,氢火焰离子化检测器(FID)检测,外标法定量。37种脂肪酸在0.5~100.0 μg/mL范围内线性关系良好,其相关系数(R²)为0.9981~0.9999,检出限(LOD)与定量限(LOQ)分别为0.01~0.02 mg/100 g和0.04~0.06 mg/100 g;以棕榈酸和硬脂酸进行加标回收验证,在1、2、10 mg/100 g 3个加标水平下的加标回收率为76.0%~97.5%,相对标准偏差(RSD, n=5)为3.31%~7.90%。该方法应用于中华绒螯蟹肌肉中脂肪酸组成与含量的测定,肌肉中共测得31种脂肪酸,碳链长度为12~24,脂肪酸总含量为281.03 mg/100 g,其中油酸、二十二碳六烯酸、二十碳五烯酸等为中华绒螯蟹肌肉中主要脂肪酸。该方法操作简便,试剂、样品用量少,且定性可靠,定量准确,能检测较多的脂肪酸种类,适用于中华绒螯蟹肌肉中脂肪酸组成与含量的快速检测。     

Self-assembly of fatty acids and hydroxyl derivative salts

We report the dispersions of a fatty acid and hydroxyl derivative salts in aqueous solutions that were further used to produce foams and emulsions. The tetrabutyl-ammonium salts of palmitic acid, 12-hydroxy stearic acid, and omega-hydroxy palmitic acid formed isotropic solutions of micelles, whereas the ethanolamine salts of the same acids formed turbid birefringent lamellar solutions. The structure and dimension of those phases were confirmed by small-angle neutron scattering and NMR. Micelles exhibited a surprisingly small radius of about 20 A, even for hydroxyl fatty acids, suggesting the formation of hydrogen bonds between lipids in the core of the micelles. In the case of ethanolamine salts of palmitic and 12-hydroxy stearic acids, the lipids were arranged in bilayers, with a phase transition from gel to fluid upon heating, whereas for omega-hydroxy palmitic acid, monolayers formed in accordance with the bola shape of this lipid. Foams and emulsions produced from ethanolamine salt solutions were more stable than those obtained from tetrabutyl-ammonium salt solutions. We discuss these results in terms of counterion size, lipid molecular shape, and membrane curvature.     

Impact of PAMAM G2 and G6 dendrimers on bovine serum albumin (fatty acids free and loaded with different fatty acids)

Dendrimers are a new class of nanotechnological polymers suitable for drug targeting, microarray systems or detoxication. The present study is devoted to a detailed analysis of binding between PAMAM dendrimers and bovine serum albumin (fatty acid free or loaded with oleic, linoleic, oleic+linoleic or oleic+linoleic+arachodonic acids) by measuring zeta-potential, fluorescence quenching, fluorescence anisotropy and electron paramagnetic resonance. Addition of PAMAM G2 and G6 dendrimers to protein solutions resulted in attachment to the protein molecule. The PAMAM dendrimers also competed with BSA for fatty acids if two or three fatty acids were loaded per protein. This can lead to the extraction of fatty acids from BSA to the PAMAM dendrimer.