Structures,practical sources (gymnosperm seeds), gas‐liquid chromatographic data (equivalent chain lengths), and mass spectrometric characteristics of all‐cis Δ5‐olefinic acids

In view of the increasing interest of lipid researchers in the biological effects of all‐cis Δ5‐unsaturated polymethylene‐interrupted fatty acids (Δ5‐UPIFA) from vegetable origin, this paper is concerned with their occurrence in practical sources (gymnosperm seeds), structures, and identification by gas‐liquid chromatography (GLC) and mass spectrometry (MS). The use of equivalent chain lengths (ECL) determined by calculations based on available standards, in close agreement with data determined with easily available commercial gymnosperm seeds specific for each Δ5‐UPIFA, allows identification of all Δ5‐UPIFA. These tentative identifications are supported by GLC‐MS of the appropriate (4, 4‐dimethyloxazoline and picolinyl ester) derivatives. ECL are particularly useful to identify Δ5‐UPIFA in tissue lipids from animals experimentally fed oils containing these acids, with no interference with polyunsaturated fatty acids of endogenous origin.     

Identification of nine acetylenic fatty acids, 9-hydroxystearic acid and 9,10-epoxystearic acid in the seed oil ofJodina rhombifolia hook et arn. (Santalaceae)

In addition to some usual fatty acids, the seed oil ofJodina rhombifolia (Santalaceae) contains nine acetylenic fatty acids [9-octadecynoic acid (stearolic acid) (1.1%),trans-10-heptadecen-8-ynoic acid (pyrulic acid) (20.1%), 7-hydroxy-trans-10-heptadecen-8-ynoic acid (2.3%),trans-10,16-heptadecadien-8-ynoic acid (0.7%), 7-hydroxy-trans-10,16-heptadecadien-8-ynoic acid (0.1%),trans-11-octadecen-9-ynoic acid (ximenynic acid) (20.3%), 8-hydroxy-trans-11-octadecen-9-ynoic acid (12.2%),trans-11,17-octadecadien-9-ynoic acid (1.5%), 8-hydroxy-trans-11,17-octadecadien-9-ynoic acid (1.3%), 9-hydroxystearic acid (<0.1%) and 9,10-epoxystearic acid (0.7%)]. The fatty acids have been analyzed by gas chromatography/mass spectrometry of their methyl ester and 4,4-dimethyloxazoline derivatives. The hydroxy fatty acid methyl esters have been examined also as trimethyl-silyl ethers. Furthermore, the fatty acid methyl esters (FAME) have been fractionated according to their polarity (FAME-A: nonhydroxy; FAME-B: hydroxy fatty acids) and to their degree of unsaturation (FAME-A1/A2; FAME-B1/B2) by preparative thin-layer chromatography and argentation chromatography, respectively. All of these fractions have been analyzed by ultraviolet and infrared spectroscopy, and the fractions FAME-A and FAME-B have been analyzed further by nuclear magnetic resonance (¹H,¹³C, 2D H/C, attached proton test) spectroscopy and gas chromatography/mass spectrometry. This work is dedicated to the 65th birthday of Prof. Dr. K. Pfeilsticker, Institut of Food Science, University Bonn (Germany).     

Unusual gas chromatographic properties of fatty acid pyrrolidides

Fatty acid pyrrolidides have been found to have unusual gas chromatographic properties on a polar stationary phase of the Carbowax type. In particular, exceptional resolution of positional isomers was achieved, and in contrast to methyl esters, unsaturated isomers with double bonds in position 5 or earlier eluted before the corresponding saturated fatty acid derivative.     

A gas chromatography‐mass spectrometry method for the detection of adipocere in grave soils

Adipocere refers to a decomposition product, which forms due to the post‐mortem conversion of adipose tissue into a lipid mixture. During the conversion process, triglycerides present in the adipose tissue convert to free fatty acids via hydrolysis. Under the right conditions, hydrogenation of the free fatty acids will yield adipocere, which is chiefly comprised of saturated fatty acids. In a burial environment, adipocere may form macroscopically on the decomposing remains, but may also leach into the surrounding soil. This paper describes the development of a gas chromatography‐mass spectrometry method which allows for the quantitative analysis of trace levels of adipocere in grave soils.     

Quantification of linolenic acid isomers by gas chromatography‐mass spectrometry and deconvolution of overlapping chromatographic peaks

The use of a technique for deconvolution of overlapping chromatographic peaks, Gentle, has been evaluated for quantification of alpha linolenic acid isomers analysed by gas chromatography‐mass spectrometry. Mixtures containing varying amounts of linolenic acid methyl ester isomers with two or three trans double bonds were analysed by two different temperature programs. Overlapping chromatographic peaks were resolved by Gentle, and the areas of the resolved peaks were compared with reference values calculated by use of internal standards. The results show that the small differences that exist between the mass spectra of the analysed isomers are sufficient to achieve deconvolution of severely overlapping peaks. The errors were larger than seen for quantification of chromatographically resolved peaks. Especially for small peaks in a peak cluster, the errors relative to the peak size were large.     

Precombustion of fatty acids and esters of biodiesel. A possible explanation for differing cetane numbers

Fatty acids of C₁₈ chainlength as well as their methyl, ethyl, n-propyl, and n-butyl esters were injected into a constant-volume combustion apparatus suitable for collecting material from the fuel spray prior to the onset of ignition. The collected material from this precombustion phase of the injection event was analyzed by gas chromatography-mass spectrometry. Compounds identified as forming during the precombustion phase were straight-chain and branched alkanes, alkenes, and cyclic hydrocarbons, as well as aldehydes, ketones, esters, substituted benzenes, and other species, such as furans. Some of the compounds formed during precombustion have low cetane numbers (CN). Low-cetane aromatic compounds were found more prominently for more unsaturated fatty compounds. Thus, the low CN of the intermediary precombustion species may constitute a possible partial explanation why some compounds, for example the more unsaturated fatty compounds, have relatively low CN. Presented in part at the 88th AOCS Annual Meeting, Seattle, Washington, May 1997.     

Confirmatory mass-spectral data for cyclic fatty acid monomers

Cyclic fatty acid monomers (CFAM) are degradation products found in heat-abused edible oils. This study confirms previously published data and reports the structural elucidation of hydrogenated and deuterated monocyclic and bicyclic CFAM prepared from the corresponding unsaturated species that were previously isolated from heated flaxseed (linseed) oil. CFAM structures were determined as 2-alkyl-4,4-dimethyloxazoline derivatives by using gas chromatography-electron ionization mass spectrometry. The observed retention times for the deuterated CFAM were about 0.1 min shorter than those of the corresponding hydrogenated species. For two minor six-membered ring CFAM components, an increase in the mass of the unsaturated ring by eight mass units upon deuteration indicated the addition of four deuterium atoms to two double bonds in that ring. These data unequivocally confirmed the identity of cyclohexadienyl CFAM species in the original CFAM mixture that was isolated from heated linseed oil. The observed electron ionization mass spectrometic data for minor hydrogenated and deuterated CFAM species, which correspond to the last two eluting monounsaturated species, were consistent with CFAM having bicyclic (fused 5- and 6-membered rings) structures. The location of the ring along the fatty acid chain was also confirmed for all saturated CFAM mixture components. The presence of a pair of deuterium atoms on two adjacent carbon atoms further confirmed the previously determined double-bond position along the fatty acid chain of the corresponding parent (unsaturated) compound. This work was presented in part at the 85th AOCS Annual Meeting in Atlanta, Georgia, May 8–12, 1994.     

Determination of fatty acids and some undesirable fatty acid isomers in selected Turkish margarines

The fatty acid composition and total trans fatty acid content in 10 margarines produced in Turkey were determined by capillary gas chromatography and Fourier transform‐infrared spectroscopy (FT‐IR) spectroscopy. The fatty acid composition ranged as follows: saturated fatty acids, C16:0 (palmitic) 11.3 to 31.8% and C18:0 (stearic) 5.7 to 8.7%, monounsaturated fatty acids, C18:1 (oleic) 21.8 to 35.7% and C18:1 trans isomers 0.4 to 27.4%, polyunsaturated fatty acid, C18:2 linoleic acid 5.2 to 40.2%. Some positional isomers of C18:1 as cis‐11‐octadecenoic acid varied from 0.7 to 4.6% and cis‐13 trace to 2.4%. The total trans fatty acid contents were between 0.9 and 32.0% when measured with capillary gas chromatography and between 0 and 30.2% with FT‐IR spectroscopy. Some of the margarines analyzed contained trace amount of trans fatty acids which could not be detected by FT‐IR spectroscopy.     

Profiling and Imaging of Phospholipids in Brains of Abcd1‐Deficient Mice

ABCD1 is a gene responsible for X‐linked adrenoleukodystrophy (X‐ALD), and is critical for the transport of very long‐chain fatty acids (VLCFA) into peroxisomes and subsequent β‐oxidation. VLCFA‐containing lipids accumulate in X‐ALD patients, although the effect of ABCD1‐deficiency on each lipid species in the central nervous system has not been fully characterized. In this study, each phospholipid and lysophospholipid species in Abcd1‐deficient mice brains were profiled by liquid chromatography‐mass spectrometry. Among the phospholipid and lysophospholipid species that are significantly more enriched in Abcd1‐deficient mice brains, VLCFA were present in 75, 15, 5, 4, and 1 species of phosphatidylcholine, phosphatidylethanolamine, sphingomyelin, lysophosphatidylcholine, and lysophosphatidylethanolamine, respectively. Most VLCFA were incorporated at the sn‐1 position of phosphatidylcholine and phosphatidylethanolamine. Among the phospholipid species that are significantly less enriched in Abcd1‐deficient mice brains, odd‐numbered saturated or mono‐unsaturated fatty acyl moieties are contained in all phosphatidylcholine species. In addition, a number of phosphatidylglycerol, phosphatidylinositol, and phosphatidylserine species contained highly unsaturated fatty acyl moieties. Intriguingly, 44:1 phosphatidylcholine with VLCFA was mainly distributed in the gray matter, such as the cortex, but not in the white matter in the cerebrum and cerebellum. These results show that ABCD1‐deficiency causes metabolic alternation of long‐chain fatty acids and VLCFA. Moreover, our results imply a molecular mechanism for the incorporation of saturated or monounsaturated VLCFA into the sn‐1 position of phospholipids, and also indicate that the distribution of phospholipids with VLCFA may correlate with the development of X‐ALD.     

Modelling lipase‐catalysed transesterification of fats containing n‐3 fatty acids monitored by their solid fat content

Transesterification of fat blends rich in n‐3 polyunsaturated fatty acids (n‐3 PUFA), catalysed by a commercial immobilised thermostable lipase from Thermomyces lanuginosa, was carried out batch‐wise. Experiments were performed, following central composite rotatable designs (CCRDs) as a function of reaction time, temperature and media formulation. Mixtures of palm stearin, palm kernel oil and a commercial concentrate of triacylglycerols rich in n‐3 PUFA (“EPAX 2050TG” in CCRD‐1 and “EPAX 4510TG” in CCRD‐2) were used. The time‐course of transesterification was indirectly followed by the solid fat content (SFC) values of the blend at 10 °C, 20 °C, 30 °C and 35 °C. A decrease in all SFC values of the blends at 10 °C, 20 °C, 30 °C and 35°C was observed upon transesterification. The SFC_{10 °C} and SFC_{20 °C} of transesterified blends varied between 18 and 48 and SFC_{35 °C} between 6 and 24. These values fulfil the technological requirements for the production of margarines. Under our conditions, lipid oxidation may be neglected. However, the accumulation up to 8.3% free fatty acids in reaction media is a problem to overcome. The development of response surface models, describing both the final SFC value and the SFC decrease, will allow predicting results for novel proportions of fats and oils and/or a novel combination time‐temperature.     

N‐3 fatty acids and conjugated linoleic acids of longissimus muscle in beef cattle

The objective of the experiment with cattle was to produce high quality beef under different feeding conditions and to increase the concentration of essential fatty acids in muscle. In total 10 German Simmental (GS) bulls and 9 German Holstein (GH) steers were kept either on pasture (grass feeding) or in stable (concentrate feeding). Despite biohydrogenation in the rumen, linolenic acid (C18:3n‐3) contained in grass was absorbed and deposited into the lipids of muscle. This led to a significantly (p ≤ 0.05) higher content of n‐3 fatty acids in the muscle lipids of grazing cattle. The relative amount of total n‐3 fatty acids increased from 1.4 g/100 g fatty acid methyl ester (%FAME) in the intensively fed Simmental bulls to 5.5 %FAME in grass fed cattle. The n‐6/n‐3 ratio of pasture grazing GS bulls was 1.3 in contrast to 13.7 of the animals kept in the byre. The total n‐3 fatty acid concentration in beef muscle increased from 24.6 mg (concentrate) to 108.6 mg/100 g wet weight (grazing). In GH steers the total n‐3 fatty acid concentration was significantly (p ≤ 0.05) increased up to 86.3 mg/100 g wet weight in pasture grazing steers compared to 28.8 mg/100 g wet weight in animals fed the concentrate. The relative content (%FAME) of CLAcis‐9, trans‐11 (0.6 vs 0.56 %FAME in GS; 0.55 vs 0.52 %FAME in GH) in muscle was not significantly increased by grazing on pasture in comparison to concentrate feeding neither in GS bulls nor in GH steers, respectively.     

Geometrical isomerisation of double bonds in acid‐catalysed preparation of fatty acid methyl esters

Acid‐catalysed methylation is frequently applied for the preparation of fatty acid methyl esters used for gas chromatographic analysis of fatty acids. A series of artefacts were observed in hydrochloric acid‐catalysed direct methylation of herring (Clupea harengus L.) muscle. The artefacts were identified as trans isomers of eicosapentaenoic and docosahexaenoic acid, and their levels increased with reaction time. The isomers were not found after methylation of a lipid extract of the herring muscle, even after extreme reaction times. In general, the trans isomers are only observed after methylation of certain marine tissues, indicating catalytic activity in these samples. Based on these results, it is recommended that direct methylation procedures are thoroughly validated with each matrix type analysed, and that reaction times should not be longer than necessary to complete the methylation.     

Fatty fish intake,n‐3 fatty acids and self‐rated health in middle‐aged adults

Background – Since n‐3 fatty acids, abundant in fatty fish, may improve health, we raised the question whether self‐reported intake frequency of fatty fish (FF) might be related to the percentage of n‐3 fatty acids in serum phospholipids (PL‐n‐3), and also to self‐rated health (H). Design – The study followed a cross‐sectional design. Methods – In the cross‐sectional Oslo Health Study, PL‐n‐3 were determined in 121 middle‐aged ethnic Norwegians and 102 immigrants from the Indian subcontinent and correlated with FF and H. Logistic regression was used to study the relationship between PL‐n‐3 and H (dichotomized, i.e. Poor vs. Good health). Results – FF correlated positively with PL20:5n‐3 (PL‐EPA, r = 0.467, p <0.001) and PL22:6n‐3 (PL‐DHA, r = 0.499, p <0.001), and negatively with PL20:4n‐6 (PL‐AA, r = –0.350, p = 0.001). H was positively associated with PL‐EPA (r = 0.321, p <0.001) and PL‐DHA (r = 0.275; p <0.001), but negatively with PL‐AA (r = –0.220, p = 0.001). The odds ratio for reporting Poor vs. Good health was significantly higher in subjects with low levels of PL‐EPA (OR = 1.49; 95% confidence interval = 1.17–1.89, p = 0.001), persisting after adjusting for sex, physical activity, ethnicity and length of education. Conclusion – The intake frequency of fatty fish is related to n‐3 fatty acids in the serum phospholipids, and to self‐rated health.     

高效液相色谱法检测氨基酸表面活性剂中脂肪酸的含量

建立了一种快速检测氨基酸表面活性剂中脂肪酸残留的高效液相色谱分析方法。采用Welch Ultimate AQ-C18色谱柱(250 mm×4.6 mm,5μm)分离,以乙腈-0.1%甲酸水溶液为流动相进行梯度洗脱,样品经过酸化、衍生化处理后用紫外可见可变波长检测器(VWD)检测。结果表明,该方法的线性范围为5~500 mg/L,相关系数均大于0.999,平均回收率为93.2%~103.0%,检出限为0.03%,定量限为0.1%。方法耗时短、操作简单、准确度高、通用性强,适用于氨基酸表面活性剂产品的脂肪酸残留检测。     

Transition‐metal trifluoromethane‐sulphonates‐recyclable catalysts for the synthesis of branched fatty derivatives by Diels‐Alder reactions at unsaturated fatty esters

Diels‐Alder reactions of conjugated linoleic acid ethyl ester (1) with different quinones and with a variety of α/βunsaturated aldehydes and ketones are described in this paper. Using Sc(OTf)₃ or Cu(OTf)₂ as catalysts the reactions can be carried out at 25—40 °C with good yields. For the first time in oleochemistry it is possible to prepare Diels‐Alder cycloadditions with catalyst concentrations of 10 mol‐% instead of stoichiometric amounts of Lewis acids. Furthermore, the reaction time was partly shortened drastically. The catalyst Sc(OTf)₃ can be removed by a simple extraction of the organic layer with water. After evaporation of the aqueous phase to dryness the catalyst can be reused without loss of yield.     

Synthesis of regioisomerically pure triacylglycerols containing n‐3 very long‐chain polyunsaturated fatty acids

There is growing scientific evidence that consumption of n‐3 very long‐chain polyunsaturated fatty acids (n‐3 VLC‐PUFA) helps in brain and eye development, and protects against a range of common degenerative diseases. This has provided the impetus to the scientists to develop new and renewable sources for these important fatty acids so that the food industry is able to produce and market products fortified with n‐3 VLC‐PUFA. The bioactive efficacy and stability of food products containing n‐3 VLC‐PUFA may be determined not only by the amount of n‐3 VLC‐PUFA present but also by the positional distribution of these acids within the triacylglycerol (TAG) molecules (regiopurity). Studies of the effects of positional distribution on the functionality of n‐3 VLC‐PUFA containing oils have been hampered by a general lack of pure TAG regioisomers for experimentation. This paper reviews methods that have been used for the synthesis of TAG regioisomers containing n‐3 VLC‐PUFA, with special reference to those in which one n‐3 VLC‐PUFA occurs in combination with two long‐chain saturated acids.     

13‐Phenyltridec‐9‐enoic and 15‐phenylpentadec‐9‐enoic acids in Arum maculatum seed oil

The seed oil of Arum maculatum has been found to contain 13‐phenyltridec‐9‐enoic (0.4%) and 15‐phenyl‐pentadec‐9‐enoic (1%) acids, detected by gas chromatographymass spectrometry of the picolinyl ester and related derivatives.     

Estimating the content of free fatty acids in high‐oleic sunflower seeds by near‐infrared spectroscopy

The content of free fatty acids (FFA) in vegetable oils represents an important quality factor in oil crops. The objective of the investigation was to develop a near‐infrared (NIR) calibration for estimating the FFA content in high‐oleic sunflower seeds. A sample set of different varieties from the harvest of 2004 as well as of 2005 from two locations in Germany was used; additionally seeds from 2003 were stored under unsuitable conditions to obtain samples utilised for calibration with an extended FFA range. A direct titration method for FFA determination was developed and adjusted to the official AOCS method. The modified method is sufficiently reliable, much faster than the AOCS method and therefore suitable for use in the calibration of NIR spectrometers. The developed NIR spectroscopy (NIRS) calibration was calculated with a modified partial least square algorithm, standard normal variate and detrend scatter correction and the 2^nd derivative of the spectra of ground sunflower seeds. The standard error of prediction of the validated calibration was 0.20, and the multiple coefficient of determination (RSQ_val) reached 0.94. The obtained results demonstrated clearly the efficiency and how cost effective the NIRS method is for the estimation of FFA content in sunflower seeds.     

The production of n‐3 long‐chain polyunsaturated fatty acids in transgenic plants

Long‐chain polyunsaturated fatty acids (LC‐PUFA) now have a proven role in human health and nutrition, including the n‐3 forms normally found in fish oils. Unfortunately, global fish stocks are now more than ever subject to over‐fishing and environmental pollution, indicating the need for an alternative source of fish oils. Recent efforts have focussed on the production of LC‐PUFA in transgenic plants to provide a sustainable and clean source of fish oils. The current progress in this area is considered, as well as the bottlenecks that remain to be overcome.     

Composition of neutral lipid classes and content of fatty acids throughout sourdough breadmaking

Broa is an example of bread that is a good candidate for inclusion in functional diets, so it deserves further in‐depth study of its chemical composition—namely with regard to evolution of the lipid profile throughout breadmaking, in order to assess whether mixing, fermentation, or baking affect its nutritional value (in terms of unsaturated fatty acids, UFA) based on the assumption that neutral lipids (NL) can be protein‐ or carbohydrate‐bound. Hence, constituent fatty acids in NL of maize (Zea mays) and rye flour (Secale cereale), and in sourdough and final broa manufactured from a mixture therefrom were quantitated. Methodologies of esterification of fatty acids, as well as of transesterification of acyl lipids and sterol esters (SE) were improved. The n‐hydrocarbons containing between 4 and 24 carbon atoms were then resolved and identified by gas–liquid chromatography. Regarding total neutral lipids (TNL) in all samples, 79–89% were TAGs, and 87–93% were TAGs and DAGs in the case of free lipids (FL). Furthermore, 73–85% of TNL in bound lipids (BL) and 65–80% of TNL in starch lipids (SL) were TAG and free fatty acids (FFA). Conversely, only 4–5%, 6–16%, and 7–10% of TNL in FL, BL, and SL, respectively, were SE and MAGs. TAGs and DAGs underwent partial hydrolysis during fermentation and baking; palmitic, oleic, and linoleic acids were dominant as products released. The nutritional value of broa lipids was apparent owing to their proportions of SE (4%) and DAG (9%), coupled with 52% of linoleic acid in all samples—as well as to the high contents of polyunsaturated versus monounsaturated or saturated fatty acids, and to the general dominance of UFA.