Unsaturated fatty acids in alkane solution: adsorption to steel surfaces

The adsorption of the unsaturated fatty acids oleic, linoleic, and linolenic acid on steel surfaces has been investigated by means of a quartz crystal microbalance (QCM). Two different solvents were used, n-hexadecane and its highly branched isomer, viz., 2,2,4,4,6,8,8-heptamethylnonane. The area occupied per molecule of oleic acid at 1 wt % corresponds to what is needed for adsorption parallel to the surface. At the same concentration, the adsorbed amount of linoleic acid and linolenic acid indicates that they adsorb in multilayers. The chemisorbed amount estimated from static secondary ion mass spectroscopy (SIMS) measurements was found to be similar for the three unsaturated fatty acids. In the case of linolenic acid, it was found that the presence of water significantly alters the adsorption, most likely because of the precipitation of fatty acid/water aggregates. Furthermore, static SIMS results indicate that the amount of water used here inhibits the chemisorption of linolenic acid.     

Characterization of Jamaican agro-industrial wastes. Part II, fatty acid profiling using HPLC: precolumn derivatization with phenacyl bromide

This paper describes the determination of fatty acid composition of coffee, citrus and rum distillery wastes using reversed-phase high-performance liquid chromatography (RP-HPLC). Lipid extracts of the waste samples are derivatized with phenacyl bromide and their phenacyl esters are separated on a C8 reversed-phase column by using continuous gradient elution with water and acetonitrile. The presence of saturated and unsaturated fatty acids in quantifiable amounts in the examined wastes, as well as the high percentage recoveries, are clear indications that these wastes have potential value as inexpensive sources of lipids. The HPLC procedures described here could be adopted for further analysis of materials of this nature.     

Rapid and Sensitive LC–MS/MS Analysis of Fatty Acids in Clinical Samples

Free fatty acids (FFAs), major cellular metabolites, play an important role during tumor pathogenesis. Enhanced de novo fatty acid synthesis in tissues is a characteristic feature of cancer. Therefore, measurement of FFA concentration in biological samples is beneficial for cancer research and clinical diagnosis. Herein, a rapid, stable, and sensitive detection methodology was established to simultaneously quantify 22 FFAs using high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI–MS/MS). The HPLC–MS/MS system was run in negative ion mode for 15 min using multiple reaction monitoring. The lipids were extracted from colon tissues of colon cancer patients and then injected into the HPLC–MS/MS system for analysis. Colon samples were analyzed by inter-day repeatability and intra-day repeatability, with less than 5 % deviation for most fatty acids. This approach is successful to determine low picogram concentrations of each FFA molecule using milligrams of tissue, and provides a promising method for FFA microanalysis in clinical samples.

     

Determination of cuticular and internal fatty acids of Chorthippus brunneus males and females using HPLC‐LLSD and GC–MS

Insects are of growing significance in veterinary medicine and human healthcare; therefore, an understanding of their biology is very important. The cuticular and internal fatty acid compositions of Chorthippus brunneus males and females have been studied for the first time. The lipids of males and females were separated into classes of compounds using high‐performance liquid chromatography with a laser light scattering detector. The free fatty acid (FFA) fractions obtained by HPLC were silylated and then analyzed by GC–MS. The cuticular lipids of males contained 15 saturated, four unsaturated with even‐numbered and two unsaturated with odd‐numbered carbon chains, FFAs ranging from C8 to C25. The major free fatty acids in males were C16 (20.8%), C18:2 (8.5%), C18:1 (32.9%) and C18 (24.4%). The cuticular lipids of females contained 17 saturated, four monounsaturated and two diunsaturated free fatty acids ranging from C8 to C30. The major cuticular fatty acids in females were C16 (25.1%), C18:2 (6.2%), C18:1 (23.7%) and C18:0 (33.2%). The internal FFAs of males consisted of 20 compounds ranging from C8 to C26. Four of these compounds were detected as major compounds: C16 (14.1%), C18:2 (21.6%), C18:1 (38.0%) and C18 (22.5%). Among 18 internal free fatty acids of females, C16 (22.3%), C18:2 (10.9%), C18:1 (40.2%) and C18 (20.5%) were the most abundant compounds. The following cuticular fatty acids present in the lipids of females were absent in the lipids of males: C26, C27 and C30. On the other hand, only C24 was absent from the cuticular lipids of females. Only C10 and C24 internal fatty acids present in the lipids of males were absent in the lipids of females. Copyright © 2016 John Wiley & Sons, Ltd.     

Quantitation of phenacyl esters of retinal fatty acids by high-performance liquid chromatography.

A high-performance liquid chromatographic (HPLC) method for the separation and quantitation of retinal fatty acids containing long-chain polyunsaturated fatty acids is described. Fatty acids from frog retinal lipids were converted to the corresponding phenacyl derivatives which were separated on a C18 reversed-phase column and detected at 242 nm. Molar absorptivities (peak area units/nmol) of up to seventeen fatty acid phenacyl derivatives were determined and used for quantitation of fatty acids separated by HPLC. Compared with gas chromatography, the HPLC method gave a similar molar percent distribution of the fatty acids and was twenty to fifty times more sensitive. This HPLC method provides a useful means for the study of chemistry and metabolism of long-chain polyunsaturated fatty acids in retina and other tissues where amounts of material may be limited or recovery of individual components desirable.     

Wettability of calcite and mica modified by different long-chain fatty acids (C18 acids)

The effect of long-chain fatty acid adsorption on the wetting states of calcite and mica powders is investigated. The selected long-chain fatty acids are saturated or unsaturated aliphatic acids (stearic acid and oleic acid, respectively) and naphthenic acids with saturated or unsaturated aromatic rings (18-cyclohexyloctadecanoic acid and 18-phenoloctadecanoic acid, respectively). The amount of irreversibly adsorbed acid is determined by thermogravimetric analysis. The affinity of water and n-decane for these samples before and after modification is deduced from their adsorption isotherm and microcalorimetry. Thermodynamic analysis of surface pressure and spreading tension are performed based on adsorption isotherms. The enthalpy versus coverage curve for water adsorption and its comparison to liquefaction enthalpy is shown to be a meaningful method for characterizing the wettability of a surface. The naphthenic acid with unsaturated aromatic ring deeply modifies the calcite to an oil-wet state. The mica powder was not as strongly modified as calcite by these acid molecules.     

深黄被孢霉催化转化十八醇合成不饱和脂肪酸

深黄被孢霉催化转化十八醇合成不饱和脂肪酸在优化转化条件下所得产物分析表明,干细胞中含油脂47.5%,蛋白质31.5%,碳水化合物28.9%.十八醇转化率为67.2%,油脂选择性为30.6%,产率20.6%.油脂中脂肪酸的选择性为:棕榈酸4.00%,棕榈油酸0.81%,硬脂酸0.95%,油酸20.75%,亚油酸1.95%,亚麻酸2.19%.催化转化条件下的研究表明,底物浓度越低,油脂和不饱和脂肪酸的选择性越好,当十八醇质量分数为0.5%时,油脂和不饱和脂肪酸的选择性达到最大值;培养基pH为中性时,获得了最大的油脂选择性和收率;33℃时醇转化率达最大值88%,23℃油脂产率达最大值9.7%.Mg²⁺对不饱和脂肪酸的生成有显著影响,当培养基中[Mg²⁺]=25mmol/L时,获得了最大的油脂选择性(25.7%)和产率(17.6%).     

Simultaneous separation and sensitive determination of free fatty acids in blood plasma by high-performance liquid chromatography

The quantitative determination of saturated and unsaturated fatty acids (ranging from acetic acid to lignoceric acid) in biological samples is presented. The secondary amine group of 5-(dimethylamino)-1-naphthalenesulponyl-semipiperazide (dansyl-semipiperazide) reacts with the carboxyl group of the fatty acids to form an amide linkage in order to obtain fluorescent derivatives of the acids. The fluorescent derivatives are analysed by high-performance liquid chromatography (HPLC) using an internal standard.     

Study of the inhibitory effect of ferulic acid on short-chain fatty acids in milk samples by dispersive liquid–liquid micro-extraction in combination with fluorescence derivatization

A sensitive high-performance liquid chromatography (HPLC) method was developed to study the influence of ferulic acid on the formation of volatile fatty acids and lactic acid in milk and soybean milk samples. Volatile fatty acids were extracted by liquid–liquid micro-extraction using chloroform and acetonitrile as the extraction and disperser solvents, respectively. The analytes were derivatized with 2-(5-benzoacridine)ethyl-p-toluenesulfonate that showed excellent fluorescence property and made the sensitive HPLC analysis of short-chain fatty acids become possible. The optimized HPLC sensitivity was in the range of 1.1–1.9?µg?L^?1. Ferulic acid was added in milk and soybean milk samples to study its preservative effect. The results indicated that ferulic acid with concentration of 0.2% (m/v) could effectively reduce the formation of short-chain fatty acids.     

Quantitative determination of the fatty acid composition of human serum lipids by high-performance liquid chromatography

A high-performance liquid chromatographic method for the analysis of the fatty acid composition of human serum lipids with fluorescence detection was examined. Both free and total fatty acids extracted from serum were derivatized with 9-anthryldiazomethane and were analysed using methanol-water (94.7:5.3) as mobile phase. Twelve kinds of fatty acid were detected, both in the free and total fatty acids, and were well separated. Concentrations of individual fatty acids of serum lipids were estimated from an internal standard, heptadecanoic acid. The results correlated well with those from two other quantitative analyses. These results indicate that the high-performance liquid chromatographic analysis of fatty acids is a reliable method for determining individual fatty acids of human serum lipids. The compositions of free fatty acids and total fatty acids of serum lipids were analysed and compared in 27 normal subjects, 27 diabetics, and 20 angina pectoris patients by this method.     

Regiospecific analysis of neutral ether lipids by liquid chromatography/electrospray ionization/single quadrupole mass spectrometry: validation with synthetic compounds.

A reversed-phase high-performance liquid chromatography (HPLC) method with on-line electrospray ionization/collision-induced dissociation/mass spectrometry (ESI/CID/MS) is presented for the regiospecific analysis of synthetic reference compounds of neutral ether lipids. The reference compounds were characterized by chromatographic retention times, full mass spectra, and fragmentation patterns as an aid to clarify the regiospecificity of ether lipids from natural sources. The results clearly show that single quadrupole mass spectroscopic analysis may elucidate the regiospecific structure of neutral ether lipids. Ether lipid reference compounds were characterized by five to six major ions in the positive ion mode. The 1-O-alkyl-sn-glycerols were analyzed as the diacetoyl derivative, and showed the [M - acetoyl](+) ion as an important diagnostic ion. The diagnostic ions of directly analyzed 1-O-alkyl-2-acyl-sn-glycerols and 1-O-alkyl-3-acyl-sn-glycerols were the [M - alkyl](+), [M + H - H(2)O](+) and [M + H](+) ions. Regiospecific characterization of the fatty acid position was evident from the relative ion intensities, as the sn-2 species had relatively high [M + H](+) ion intensities compared with [M + H - H(2)O](+), whereas the reverse situation characterized the sn-3 species. Furthermore, corresponding sn-2 and sn-3 species were separated by the chromatographic system. However, loss of water was promoted as fatty acid unsaturation was raised, which may complicate interpretation of the mass spectra. The diagnostic ions of directly analyzed 1-O-alkyl-2,3-diacyl-sn-glycerols were the [M - alkyl](+), [M - sn-2-acyl](+) and [M - sn-3-acyl](+) ions. Regiospecific characterization of the fatty acid identity and position was evident from the relative ion intensities, as fragmentation of the sn-2 fatty acids was preferred to the sn-3 fatty acids; however, loss of fatty acids was also promoted by higher degrees of unsaturation. Therefore, both structural and positional effects of the fatty acids affect the spectra of the neutral ether lipids. Fragmentation patterns and optimal capillary exit voltages are suggested for each neutral ether lipid class. The present study demonstrates that reversed-phase HPLC and positive ion ESI/CID/MS provide direct and unambiguous information about the configuration and identity of molecular species in neutral 1-O-alkyl-sn-glycerol classes.     

Fatty acid profiles of sebaceous triglycerides by capillary gas chromatography with mass-selective detection

Fatty acid methyl esters prepared from the triglyceride fraction of skin surface lipids from six adult human males were chromatographed on a 50-m fused-silica column coated with the highly polar cyanopropylpolysiloxane phase. This permitted the resolution of double-bond positional and geometric isomers. By means of mass-selective detection, 33 saturated and 14 unsaturated fatty acid chain types were analysed. Interpretation of the mass spectra combined with precise calculation of equivalent chain length values permitted the identification of 22 saturated and all of the unsaturated chain types. Quantification by integration of total-ion and selected-ion chromatograms revealed marked variation in the triglyceride fatty acid composition between different subjects. The greatest variation was observed in the concentrations of even-carbon-numbered iso-branched acids, which ranged from 1.5 to 11% of the saturated and from 1.9 to 12.7% of the monounsaturated acids. The anteiso chain structures constituted 4-9% of the saturated and 3-6% of the unsaturated members. Fatty acids with 4-methyl branch showed the least variation, in the range 5.7-7.4%. Other methyl-branched acids made up 4-10% of the saturated group, but were not detected in the unsaturated acids fraction. Two 18:1 fatty acids were identified (a delta 8 and a delta 9), which possibly have different anatomical origins. Similarly, two 18:2 fatty acids (linoleic and a 2,3-dimethyl derivative) were identified. A 2-methyl C17 acid, probably of bacterial origin, was detected.     

Antioxidant properties of natural substances in irradiated fresh poultry

This study was undertaken to determine if a combined treatment (marinating in natural plant extracts or vacuum) with irradiation could have a synergistic effect, in order to prevent the lipid oxidation resulting in the development of undesirable flavours. The fresh chicken legs were irradiated at 0,3 and 5 kGy. The fatty acids composition of lipids was identified using gas liquid chromatography. The effect of irradiation treatment combined with a pre-treatment on the fatty acids composition was followed. The day after irradiation, ten panallists were asked to evaluate, using the instruction scaling, the overall appearance, the odor, the flavor and the overall acceptability of the samples. The major fatty acids identified in lipids were oleic acid, palmitic acid, palmitoleic acid and stearic acid. Pre-treatments have a significant effect on linoleic acid (C18:2) and higher fatty acids. The unsaturated fatty acids derived from phospholipids appeared to be more affected by the irradiation dose: however, marinating have better protection on C18:2 derived from phospholipids. The results of sensory evaluation have shown a significant better odor and flavor for the irradiated chicken at 5 kGy than the control. No significant difference have been found between the marinated chicken, the chicken irradiated under vacuum and the control.     

Precipitation and Solubility of Calcium Soaps in Basic Aqueous Media

Measurements of the surface tension of aqueous media containing calcium salts of different fatty acids, whose structure only varied by the number of C=C unsaturations along their aliphatic chains, showed that their solubility increased as a function of this parameter going from near zero for calcium stearate to 4x10(-4) mol l(-1) for the linolenate homologue. The solubility product of the calcium soap corresponding to each tested fatty acid was estimated by using the anionic fatty acids adsorption isotherms in order to obtain the amount of dissolved ionic fatty acid at increasing concentration of calcium ions. These findings are discussed in terms of their serious repercussions on the operations related to flotation deinking in waste paper recycling. Copyright 2001 Academic Press.     

Kinetic study of adsorption of some biocompounds at the oil/water interface

The adsorption kinetics of some local anesthetics, like dibucaine and tetracaine, and of stearic acid from bulk solutions at the oil/water interface was studied by using the pendent drop and ring methods. The anesthetics were dissolved in aqueous solutions (pH 2), and the fatty acid was dissolved in benzene, each biocompound at several different concentrations in bulk solutions. Kinetic equations for Langmuir mechanism of adsorption at oil/water interface were tested. The kinetic analysis shows that Langmuir kinetic approach describes the dynamic interfacial pressures within the limits of the experimental errors over a wide range of time and for different surfactant concentrations in bulk solutions. It is also concluded that this approach allows the calculation of the ratio of the adsorption and desorption rate constants of these biocompounds at the oil/water interface. Obtained results are in substantial agreement with earlier reported data for the surfactant adsorption as, well as with their molecular structure.     

Separation and determination of dissolved and particulate humic substances in river water

Distribution of humic and fulvic acids in participate or dissolved form is studied by using simple leaching and sorption techniques. After filtration of water sample (100–200 ml), the filter along with suspended particles is treated with 5 ml of chloroform and 3 ml of 0.1 mol/l sodium hydroxide solution. The filter dissolves completely in the organic phase, while the suspended particles remain in the aqueous phase enabling a leaching of humic substances. The leaching is repeated once more with 2 ml of 0.1 mol/l sodium hydroxide solution. The humic and fulvic acids in the combined solution are fractionated at pH l by filtration, where the membrane filter is preliminarily coated with sodium dodecyl sulfate. On the other hand, dissolved humic substances are concentrated from a 50-ml filtered sample by sorption on a DEAE-cellulose column. They are desorbed with 5 ml of 0.1 mol/l sodium hydroxide solution and fractionated at pH 1. The spectrophotometric analysis of river water reveals that fulvic acid is predominant in suspended particles as well as in filtered samples. The concentration of dissolved humic and fulvic acids is approximately ten times that of suspended particles.     

Docosahexaenoic acid and eicosapentaenoic acid induce changes in the physical properties of a lipid bilayer model membrane

We investigated the effect of fatty acids such as stearic acid (SA, 18:0), oleic acid (OA, 18:1), eicosapentaenoic acid (EPA, 20:5), and docosahexaenoic acid (DHA, 22:6) on a dipalmitoylphosphatidylcholine (DPPC) bilayer by determining the phase transition temperature, fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH), and detergent insolubility. Treatment with unsaturated fatty acid broadened and shifted the phase transitions of the DPPC bilayer to a lower temperature. The phase transition temperature and the value of fluorescence anisotropy of DPH at 37 degrees C decreased progressively with increasing treatment amounts of unsaturated fatty acid. A large amount of the DPPC bilayer treated with unsaturated fatty acid was dissolved in Triton X-100, obtaining a low level of detergent insolubility. These modifications of the bilayer physical properties were most pronounced with DHA and EPA treatment. These data show that unsaturated fatty acids, particularly DHA and EPA, induce a marked change in the lipid bilayer structure. The composition of fatty acids in the DPPC bilayer was similar after treatment with various unsaturated fatty acids, suggesting that the different actions of unsaturated fatty acids are attributed to change in the molecular structure (e.g., kinked conformation by double bonds). We further explored the change in physical properties induced by fatty acids dispersed in a water-in-oil-in-water multiple emulsion and found that unsaturated fatty acids acted efficiently on the DPPC bilayer, even when incorporated in emulsion form.     

Fatty acid composition of the lipids of whitefish of the Ob basin. II. Influence of localization on the composition of total and neutral lipids

The composition of methyl esters of the fatty acids of the total and neutral lipids from the viscera, dark muscles, and brain of pelyads from the water bodies of the Ob basin have been studied by gas-liquid chromatography in comparison with the fatty acid composition of the total lipids of the light muscles. In all the lipids, 29 acids were detected and 27 were identified, six of which made up 75 to 79% of the total. It has been shown that the uniqueness of the total lipids of the viscera and dark muscles is due to a high content of eicosapentaenoic acid, while the brain lipids are distinguished by a high palmitic acid content. In the neutral lipids, regardless of their localization, the concentration of polyenes falls and the concentration of monoenes rises.     

Adsorption and reversed-phase high-performance liquid chromatography of p-nitrobenzyl esters of monohydroxy fatty acids

To enhance the UV detectability of hydroxy fatty acids, p-nitrobenzyl (PNB) esters of twenty-two different monohydroxy fatty acids of various chain-lengths (C16-C22) and differing positional isomers were formed using O-(p-nitrobenzyl)-N,N-(diisopropyl)-isourea (PNBDI) as alkylating agent. Reversed-phase and adsorption high-performance liquid chromatography (HPLC) of the twenty-two monohydroxy fatty acid PNB esters were studied. The PNB group did not dominate the chromatographic properties of monohydroxy fatty acids and it did not interfere with the HPLC separation of positional isomers. PNBDI was, however, found to be less than ideal for formation of PNB derivatives of monohydroxy fatty acids because UV absorbing contaminants of PNBDI interfered with the HPLC analyses.     

Chemistry and Biochemistry of Unsaturated Fatty Acids

Although unsaturated fatty acids have long been known to accompany saturated fatty acids in most lipids, qualitative and quantitative determination of fatty acid patterns only became possible with the advent of modern analytical methods. Present day knowledge of the chemical structure, physical properties, and metabolism of unsaturated fatty acids provides the basis for the development of new concepts of their function. Thus unsaturated fatty acids crucially determine the properties of biological membranes. Moreover, essential fatty acids are precursors of prostaglandins.