Positions Of Triacylglycerols Research Articles

Enrichment of pinolenic acid at the sn-2 position of triacylglycerol molecules through lipase-catalyzed reaction

Reports have shown that ∆-5 polyunsaturated fatty acids (∆-5 PUFA) are enriched at sn-1,3 positions of triacylglycerols (TAG) in pine (Pinus koraiensis) nut oil (Pn). As a major ∆-5 PUFA, pinolenic acid (Pi) is about 14.2% in the oil, while the percentage of Pi at the sn-1 and/or sn-3 positions in TAG was found more than 20%. In this current study, the enhancement of Pi at the sn-2 position has been achieved by acyl migration during the lipase-catalyzed inter-esterification between Pn and palm stearin (Ps). After reaction, the proportion of Pi increased at sn-2 positional fatty acid even is similar to that in total fatty acid; for example, in the inter-esterified product of 50:50 (Pn:Ps), the same amount of Pi (7.1%) present was detected both at the sn-2 and sn-1,3 positions. However, the reduction of phytosterols and tocopherols are observed in the inter-esterified products.

Ratios of Regioisomers of Triacylglycerols Containing Dihydroxy Fatty Acids in Castor Oil by Mass Spectrometry

AbstractThe triacylglycerols (TAG) containing dihydroxy fatty acids have been recently identified by mass spectrometry in castor oil. These new dihydroxy fatty acids were proposed as 11,12‐dihydroxy‐9‐octadecenoic acid (diOH18:1), 11,12‐dihydroxy‐9,13‐octadecadienoic acid (diOH18:2) and 11,12‐dihydroxyoctadecanoic acid (diOH18:0). The ratios of regioisomers of the TAG were estimated by fragment ions from the loss of fatty acids at the sn‐2 position as α,β‐unsaturated fatty acids by electro spray ionization‐mass spectrometry of the lithium adducts (MS3). The content of regioisomeric diOH18:1‐OH18:1‐diOH18:1 (ABA, with two different fatty acids) was about 92% in the total of stereoisomeric diOH18:1‐OH18:1‐diOH18:1, OH18:1‐diOH18:1‐diOH18:1 and diOH18:1‐diOH18:1‐OH18:1 combined. The approximate contents of other regioisomers were as follows: diOH18:1‐OH18:1‐OH18:1 (92%), diOH18:1‐diOH18:0‐diOH18:1 (91%), diOH18:2‐OH18:1‐OH18:1 (80%) and diOH18:0‐OH18:1‐OH18:1 (96%). The ratios of regioisomers of TAG (ABC) containing three different fatty acids were estimated as about 7:1:2 (OH18:1:diOH18:1:diOH18:2) and about 7:2:1 (OH18:1:diOH18:0:diOH18:1). Ricinoleate (OH18:1) was predominately at the sn‐2 position of TAG (both AAB and ABC) containing dihydroxy fatty acids and ricinoleate. Dihydroxy fatty acids were mainly at the sn‐1,3 positions of TAG containing dihydroxy fatty acids and ricinoleate in castor oil. The ratios of the three regioisomers of TAG (ABC) containing three different fatty acids by mass spectrometry are first reported here.

The role of stereospecific saturated fatty acid positions on lipid nutrition.

The saturated fatty acids in the sn-1 and -3 position of triacylglycerols can exhibit different metabolic patterns due to their low absorptivity. This means that dietary fats containing saturated fats primarily in sn-1 and -3 positions (e.g., cocoa butter, coconut oil, and palm oil) can have very different biological consequences than those fats in which the saturated fats are primarily in the sn-2 position (e.g., milk fat and lard). Differences in stereospecific fatty acid location should therefore be an important consideration in the design and interpretation of lipid nutrition studies and in the production of specialty food products.

Effects of Rice Bran Oil Enriched with n‐3 PUFA on Liver and Serum Lipids in Rats

Lipase-catalyzed interesterification was used to prepare different structured lipids (SL) from rice bran oil (RBO) by replacing some of the fatty acids with alpha-linolenic acid (ALA) from linseed oil (LSO) and n-3 long chain polyunsaturated fatty acids (PUFA) from cod liver oil (CLO). In one SL, the ALA content was 20% whereas in another the long chain n-3 PUFA content was 10%. Most of the n-3 PUFA were incorporated into the sn-1 and sn-3 positions of triacylglycerol. The influence of SL with RBO rich in ALA and EPA + DHA was studied on various lipid parameters in experimental animals. Rats fed RBO showed a decrease in total serum cholesterol by 10% when compared to groundnut oil (GNO). Similarly structured lipids with CLO and LSO significantly decreased total serum cholesterol by 19 and 22% respectively compared to rice bran oil. The serum TAGs level of rats fed SLs and blended oils were also significantly decreased by 14 and 17% respectively compared to RBO. Feeding of an n-3 PUFA rich diet resulted in the accumulation of long chain n-3 PUFA in various tissues and a reduction in the long chain n-6 PUFA. These studies indicate that the incorporation of ALA and EPA + DHA into RBO can offer health benefits.

Synthesis and Structural Analysis of Structured Triacylglycerols with CLA Isomers in the sn‐2‐ Position

AbstractThe present research deals with the chemical esterification of the sn‐2‐ position of sn‐1,3‐diacylglycerol (sn‐1,3‐DAG) with 9cis,11trans (c9,t11) and 10trans,12cis (t10,c12) conjugated linoleic acid (CLA) isomers to obtain structured triacylglycerols (TAG); the sn‐1,3‐DAG substrates were produced from extra virgin olive oil by means of enzymatic reactions while CLA isomers were obtained using a three‐step procedure based on alkaline hydrolysis of sunflower oil, urea purification of linoleic acid (LA) and alkaline isomerization of LA. The results showed good levels of CLA incorporation in structured TAG at the tested temperatures: 37.5% at 4 °C and 39.1% at 14 °C. To evaluate the incorporation of CLA isomers in sn‐2‐ position of sn‐1,3‐DAG structural analysis of the newly synthesized TAG was carried out using an enzymatic and a chemical method. The results of the structural analysis also showed up the occurrence of acyl migration. The pancreatic lipase method allowed the direct determination of the fatty acid composition of TAG sn‐2‐ position but this enzymatic method showed different results (p < 0.05) in respect to the chemical one; this occurrence could be due to an acylic specificity of the lipase. High incorporation of CLA isomers in sn‐2‐ position of TAG was observed, 77.0% at 4 °C and 81.5% at 14 °C, considering the results of the chemical procedure.

Docosahexaenoic Acid is More Stable to Oxidation when Located at the sn‐2 Position of Triacylglycerol Compared to sn‐1(3)

AbstractRegio‐isomeric effects on the oxidative stability of triacylglycerols (TAG) containing docosahexaenoic acid (DHA) were investigated using two pairs of regio‐isomerically pure TAG, namely 1,3‐dihexadecanoyl‐2‐(4,7,10,13,16,19‐docosahexaenoyl)glycerol (PDP)/1,2‐dihexadecanoyl‐3‐(4,7,10,13,16,19‐docosahexaenoyl)glycerol (PPD) and 1,3‐dioctadecenoyl‐2‐(4,7,10,13,16,19‐docosahexaenoyl)glycerol (ODO)/1,2‐dioctadecenoyl‐3‐(4,7,10,13,16,19‐docosahexaenoyl)glycerol (OOD) where P, O, and D represent palmitic acid, oleic acid, and DHA respectively. Each pair of regio‐isomers was subjected to accelerated auto‐oxidation (at 40 or 50 °C inside a dark oven). In each case, the TAG oxidized more slowly when DHA was located at the sn‐2 position (PDP and ODO) compared to the sn‐1(3) position (PPD and OOD), as evidenced by slower development of peroxide value, slower depletion of DHA, and slower generation of secondary oxidation products propanal and trans, trans‐2,4‐heptadienal. The positional effect on auto‐oxidation was more pronounced when DHA occurred in combination with oleic acid than with palmitic acid.

Original Normal-Phase High-Performance Liquid Chromatographic Separation of Monoacylglycerol Classes from Extra Virgin Olive Oil Triacylglycerols for Their Stereospecific Analysis

An innovative procedure to separate the 3 isomeric sn-monoacylglycerols (MAG) classes (sn-1-, sn-2-, sn-3-MAG) is described. MAGs, obtained by chemical deacylation of triacylglycerols (TAGs), have been derivatized with (S)-(+)-1-(1-naphtyl)ethyl-isocyanate, and the resulting urethane derivatives have been separated by normal-phase high-performance liquid chromatography. This procedure allows resolution as diasteroisomers of the 2 enantiomeric classes (sn-1-MAG and sn-3-MAG), without the need of a chiral column, and to separate also the isomeric sn-2-MAG class; moreover, by introducing a chromophoric moiety, this reagent makes possible the ultraviolet detection of the analyte molecules. This procedure has been used to obtain the stereospecific analysis of the TAG fraction of extra virgin olive oil samples. The use of a nondestructive detector permitted the collection of the individual urethane classes; the fatty acid composition of each was determined by high-resolution gas chromatography, obtaining directly from the data the fatty acid distribution within each sn- position of TAGs. To validate this new method, the results have been compared with those obtained by 2 other procedures for TAG stereospecific analysis, and the obtained results were satisfactory since the proposed method gave data very similar to the other procedures.

Regiospecific Analysis of Diricinoleoylacylglycerols in Castor (Ricinus communis L.) Oil by Electrospray Ionization−Mass Spectrometry

HPLC fractions of diricinoleoylacylglycerols containing one non-ricinoleoyl chain from castor oil were used to identify the regiospecific location of this non-ricinoleoyl chain on the glycerol backbone using electrospray ionization-MS3 of lithium adducts. The regiospecific ions used were from the loss of alpha,beta-unsaturated fatty acid specific at the sn-2 position. The content of 1,3-diricinoleoyl-2-oleoyl-sn-glycerols (ROR) among the three stereospecific isomers, RRO, ROR and ORR, was about 91%. The contents of other 1,3-diricinoleoyl-2-acyl-glycerols among the three stereospecific isomers were as follows: 1,3-diricinoleoyl-2-linoleoyl-sn-glycerol, 95%; 1,3-diricinoleoyl-2-linolenoyl-sn-glycerol, 96%; 1,3-diricinoleoyl-2-stearoyl-sn-glycerol, 96%; 1,3-diricinoleoyl-2-palmitoyl-sn-glycerol, 78%; and 1,3-diricinoleoyl-2-lesqueroloyl-sn-glycerol, 31%. These non-hydroxyl fatty acids were mostly at the sn-2 position of triacylglycerols in castor oil. These results suggest that phospholipase A2 hydrolysis of phosphatidylcholine (PC) containing non-hydroxyl fatty acid at the sn-2 position is either blocked or partially blocked in vivo. Phospholipase A2 hydrolysis of 2-lesqueroloyl-PC is not blocked and is similar to that of 2-ricinoleoyl-PC. Transgenic inhibition of phospholipase C hydrolysis of PC might be used to block the incorporation of non-hydroxyl fatty acids into triacylglycerols, thus increasing the content of ricinoleate in seed oil.

Effects of stereospecific positioning of fatty acids in triacylglycerol structures in native and randomized fats: a review of their nutritional implications.

Most studies on lipid lowering diets have focused on the total content of saturated, polyunsaturated and monounsaturated fatty acids. However, the distribution of these fatty acids on the triacylglycerol (TAG) molecule and the molecular TAG species generated by this stereospecificity are characteristic for various native dietary TAGs. Fat randomization or interesterification is a process involving the positional redistribution of fatty acids, which leads to the generation of new TAG molecular species. A comparison between native and randomized TAGs is the subject of this review with regards to the role of stereospecificity of fatty acids in metabolic processing and effects on fasting lipids and postprandial lipemia. The positioning of unsaturated versus saturated fatty acids in the sn-2 position of TAGs indicate differences in early metabolic processing and postprandial clearance, which may explain modulatory effects on atherogenecity and thrombogenecity. Both human and animal studies are discussed with implications for human health.

Conjugated fatty acids accumulate to high levels in phospholipids of metabolically engineered soybean and Arabidopsis seeds

Expression of Δ 12-oleic acid desaturase-related fatty acid conjugases from Calendula officinalis, Momordica charantia, and Vernicia fordii in seeds of soybean ( Glycine max) or an Arabidopsis thaliana fad3/fae1 mutant was accompanied by the accumulation of the conjugated fatty acids calendic acid or α-eleostearic acid to amounts as high as 20% of the total fatty acids. Conjugated fatty acids, which are synthesized from phosphatidylcholine (PC)-linked substrates, accumulated in PC and phosphatidylethanolamine, and relative amounts of these fatty acids were higher in PC than in triacylglycerol (TAG) in the transgenic seeds. The highest relative amounts of conjugated fatty acids were detected in PC from seeds of soybean and A. thaliana that expressed the C. officinalis and M. charantia conjugases, where they accounted for nearly 25% of the fatty acids of this lipid class. In these seeds, >85% of the conjugated fatty acids in PC were detected in the sn-2 position, and these fatty acids were also enriched in the sn-2 position of TAG. In marked contrast to the transgenic seeds, conjugated fatty acids composed <1.5% of the fatty acids in PC from seeds of five unrelated species that naturally synthesize a variety of conjugated fatty acid isomers, including seeds that accumulate conjugated fatty acids to >80% of the total fatty acids. These results suggest that soybean and A. thaliana seeds are deficient in their metabolic capacity to selectively catalyze the flux of conjugated fatty acids from their site of synthesis on PC to storage in TAG.

Distribution of unusual fatty acids in the triacylglycerols of sea buckthorn mesocarp oil

The structure of unusual fatty acid (FA) components of triacylglycerols (TAGs) of mature sea buckthorn (Hippophae rhamnoides L.) mesocarp oil was determined by GLC and MS, and the positional-species composition (PSC) of these TAGs was estimated using the methods of TAG chemical deacylation, TLC, GLC, and computer calculation. It was shown that the unusual FAs comprised n-cis-Δ9-hexadecenoic, n-cis-Δ9,12-hexadecadienoic (palmitolinoleic), and n-cis-Δ11-octadecenoic (cis-vaccenic) acids. The hexadecenoic acid predominated in the oil, and in its distribution in TAGs, it was similar to the total FAs differing from them only in some prevalence in the triunsaturated TAGs and in the TAGs with a shorter acyl chain, as well as in the sn-2 position of TAGs. Palmitolinoleic (16:2) acid comprised only 5% of total FAs, and it was exclusively concentrated in the sn-2 position of TAGs. As regards its distribution between various positional types and forms of TAGs, the 16:2 acid was similar to oleate and total FAs. As compared to the total TAGs, the TAGs with 16:2 acid were characterized by a lower FA chain length as well as by a highest unsaturation. The TAGs with vaccenic acid (V-TAGs) considerably exceeded O-TAGs, i.e., the TAGs containing oleic acid, another 18:1 positional isomer, both in their content in the total TAGs and in their unsaturation. In the composition of positional types and fractions of various unsaturation, O-TAGs were similar to the total TAGs, while V-TAGs were characterized by a very unusual structure, viz., a very high triunsaturated TAG level and an extremely low concentration of 1,3-disaturated-2-monounsaturated TAGs. In addition, oleic acid, like most other unsaturated FAs, was incorporated predominantly in the sn-2 position of TAGs, while vaccenic acid, being also unsaturated, was nevertheless by 90% concentrated in the sn-1,3 positions of V-TAGs. Unusual FAs were related to each other in the mechanism of their biosynthesis. In fact, hexadecenoic acid biosynthesis produced by palmitic acid desaturation, was, on the one hand, further desaturated forming palmitolinoleic acid, and, on the other hand, converted to vaccenic acid via C2 elongation.

Triacylglycerol Fatty Acid Positional Distribution and Postprandial Lipid Metabolism

Triacylglycerol (TAG) structure affects the biochemical properties of fat. According to studies with animals and infants, absorption of palmitic and stearic acids is inferior from the stereospecifically numbered (sn) positions sn-1 and sn-3 compared with from the sn-2 position of TAGs, and saturated fatty acids in the sn-2 position, delay the clearance of chylomicron remnants. Medium chain fatty acids are transported both in lymph and in portal blood, lymphatic absorption being more efficient from the sn-2 position.Recently, new information has arisen on the variation in TAG composition within the postprandial period and on differences in the TAG structure-dependent formation and clearance of chylomicron and very low density lipoprotein TAGs. This article reviews the metabolism of TAG fatty acids in different sn positions.

STRUCTURED TRIACYLGLYCEROLS CONTAINING BEHENIC ACID: PREPARATION AND PROPERTIES

ABSTRACT Low‐calorie structured lipids (SL) containing behenic and oleic acids were prepared using interesterification of olive oil with hydrogenated high erucic acid rapeseed oil and acidolysis of olive oil with behenic acid. The reactions were catalyzed by the Lipozyme RM IM enzyme. Triacylglycerols (TAGs), obtained by interesterification (TAG SLHE ), contained 20.9 and 45.3% of behenic and oleic acids, respectively, whereas those obtained by acidolysis (TAG SLB ) contained 34.6 and 49.6% of these acids, respectively. In both cases, behenic acid was mainly incorporated in the sn‐1,3 positions of the TAG molecules (∼93%). The distribution of oleic acid in the individual positions was different for each product. The content of oleic acid in the sn‐2 position of TAG was 50.2 and 80.3% for TAGSLHEand TAGSLB, respectively. The melting temperature of TAGSLHE(45.5%) was higher than that of TAGSLB(37.5%). Because of the suitable solid fat content characteristics of TAGSLBas a function of temperature, it is possible to use TAGSLBin bakery and in confectionery industries for production of margarines and blends, among others.

Effects of Rhodium Heterogeneous Catalyst and Isomerization Conditions on Linoleic Acid Conjugation of Soybean Oil

Rhodium heterogeneous catalyst was used to catalyze isomerization of linoleic acid in soybean oil to conjugated linoleic acid (CLA). A central composite rotatable design with five levels of three variables, namely, reaction temperature, stirring speed, and reaction time, was used to determine the maximum CLA yield. The formation of CLA during isomerization was greatly dependent on the reaction temperature and time. The CLA content of soybean oil increased from 0.63 to 202.42 mg/g oil when isomerization was done at 200 degrees C, with a stirring speed of 200 rpm for 49 min. Analysis of triacylglycerol positions showed that linoleic acid at any position in a triacylglyceride could possibly be isomerized to CLA.

The Effect of Eicosapentaenoic Acid on Rat Lymphocyte Proliferation Depends Upon Its Position in Dietary Triacylglycerols

Animal and human studies have shown that greatly increasing the amount of fish oil [rich in long-chain (n-3) PUFA] in the diet can decrease lymphocyte functions. The effects of a more modest provision of long-chain (n-3) PUFA and whether eicosapentaenoic acid (20:5) and docosahexaenoic acid (22:6) have the same effects as one another are unclear. Whether the position of 20:5 or 22:6 in dietary triacylglycerols (TAG) influences their incorporation into immune cells and their subsequent functional effects is not known. In this study, male weanling rats were fed for 6 wk one of 9 diets that contained 178 g lipid/kg and that differed in the type of (n-3) PUFA and in the position of these in dietary TAG. The control diet contained 4.4 g alpha-linolenic acid (18:3)/100 g total fatty acids. In the other diets, 20:5 or 22:6 replaced a portion (50 or 100%) of 18:3, and were in the sn-2 or the sn-1(3) position of dietary TAG. There were significant dose-dependent increases in the proportion of 20:5 or 22:6 in spleen mononuclear cell phospholipids when 20:5 or 22:6 was fed. These increases were at the expense of arachidonic acid and were largely independent of the position of 20:5 or 22:6 in dietary TAG. Spleen lymphocyte proliferation increased dose dependently when 20:5 was fed in the sn-1(3) position of dietary TAG. There were no significant differences in interleukin-2, interferon-gamma or interleukin-10 production among spleen cells from rats fed the different diets. Prostaglandin E(2) production by spleen mononuclear cells was decreased by inclusion of either 20:5 or 22:6 in the diet in the sn-1(3) position. Thus, incorporation of 20:5 or 22:6 into spleen mononuclear cell phospholipids is not influenced by the position in dietary TAG. However, the pattern of incorporation may be influenced, and there are some differential functional effects of the position of long-chain (n-3) PUFA in dietary TAG. A moderate increase in the intake of 20:5 at the sn-1(3) position of dietary TAG increases lymphocyte proliferation.

The effect of feeding structured triacylglycerols enriched in eicosapentaenoic or docosahexaenoic acids on murine splenocyte fatty acid composition and leucocyte phagocytosis.

The effects of altering the type of n-3 polyunsaturated fatty acid (PUFA) in the mouse diet on the ability of monocytes and neutrophils to perform phagocytosis were investigated. Male weanling mice were fed for 7 d on one of nine diets which contained 178 g lipid/kg and which differed in the type of n-3 PUFA and in the position of these in dietary triacylglycerol (TAG). The control diet contained 4.4 g alpha-linolenic acid/100 g total fatty acids. In the other diets, eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) replaced a proportion (50 or 100 %) of the alpha-linolenic acid, and were in the sn-2 or the sn-1(3) position of dietary TAG. There were significant increases in the content of n-3 PUFA in spleen-cell phospholipids when EPA or DHA was fed. These increases were largely independent of the position of EPA or DHA in dietary TAG except when EPA was fed at the highest level, when the incorporation was greater when it was fed in the sn-2 than in the sn-1(3) position. There was no significant effect of dietary DHA on monocyte or neutrophil phagocytic activity. Dietary EPA dose-dependently decreased the number of monocytes and neutrophils performing phagocytosis. However, when EPA was fed in the sn-2 position, the ability of active monocytes or neutrophils to engulf bacteria was increased in a dose-dependent fashion. This did not occur when EPA was fed in the sn-1(3) position. Thus, there appears to be an influence of the position of EPA, but not of DHA, in dietary TAG on its incorporation into cell phospholipids and on the activity of phagocytic cells.

Heterologous expression of a fatty acid hydroxylase gene in developing seeds of Arabidopsis thaliana.

Expression of a cDNA encoding the castor bean ( Ricinus communis L.) oleate Delta12-hydroxylase in the developing seeds of Arabidopsis thaliana (L.) Heynh. results in the synthesis of four novel hydroxy fatty acids. These have been previously identified as ricinoleic acid (12-hydroxy-octadec- cis-9-enoic acid: 18:1-OH), densipolic acid (12-hydroxy-octadec- cis-9,15-enoic acid: 18:2-OH), lesquerolic acid (14-hydroxy-eicos- cis-11-enoic acid: 20:1-OH) and auricolic acid (14-hydroxy-eicos- cis-11,17-enoic acid: 20:2-OH). Using mutant lines of Arabidopsis that lack the activity of the FAE1 condensing enzyme or FAD3 ER Delta-15-desaturase, we have shown that these enzymes are required for the synthesis of C20 hydroxy fatty acids and polyunsaturated hydroxy fatty acids, respectively. Analysis of the seed fatty acid composition of transformed plants demonstrated a dramatic increase in oleic acid (18:1) levels and a decrease in linoleic acid (18:2) content correlating to the levels of hydroxy fatty acid present in the seed. Plants in which FAD2 (ER Delta12-desaturase) activity was absent showed a decrease in 18:1 content and a slight increase in 18:2 levels corresponding to hydroxy fatty acid content. Expression of the castor hydroxylase protein in yeast indicates that this enzyme has a low level of fatty acid Delta12-desaturase activity. Lipase catalysed 1,3-specific lipolysis of triacylglycerol from transformed plants demonstrated that ricinoleic acid is not excluded from the sn-2 position of triacylglycerol, but is the only hydroxy fatty acid present at this position.

Regiospecific distribution of fatty acids in triacylglycerols of Artemiafranciscana nauplii enriched with fatty acid ethyl esters

This paper reports the positional distribution of fatty acids in triacylglycerols (TAG) of Artemia franciscana nauplii enriched with each of palmitic (16:0), oleic (18:1n-9), linoleic (18:2n-6), linolenic (18:3n-3), eicosapentaenoic (20:5n-3), and docosahexaenoic (22:6n-3) acid ethyl esters. TAG extracted from the enriched and unenriched nauplii were subjected to regiospecific analysis to determine the fatty acid compositions of the sn-1(3) and sn-2 positions of TAG. In the unenriched nauplii, 16:0, 18:1n-9, and 18:2n-6 were preferentially located in the sn-1(3) position followed by the sn-2 position [i.e. sn-1(3)> sn-2], whereas 18:3n-3 was concentrated in the sn-2 position [i.e. sn-2> sn-1(3)]. Contents of 20:5n-3 and 22:6n-3 were low. After the nauplii were enriched with each of the ethyl esters for 18 h, fatty acid fed to the nauplii showed higher content in the sn-1(3) position than in the sn-2 position [i.e. sn-1(3)> sn-2]. Distribution pattern of 18:3n-3 changed from sn-2> sn-1(3) to sn-1(3)> sn-2 during the enrichment with 18:3n-3 ethyl ester. Increases in all of the fatty acids in TAG were attributed to that in the sn-1(3) position much more than that in the sn-2 position. Artemia nauplii appear to be characterized by preferential incorporation of exogenous fatty acids into the sn-1(3) position of TAG, even though endogenous fatty acids are esterified in the opposite position.

In vitro effects of cuticular lipids of the aphids Sitobion avenae, Hyalopterus pruni and Brevicoryne brassicae on growth and sporulation of the Paecilomyces fumosoroseus and Beauveria bassiana

The exoskeleton lipids of three dangerous pests, Sitobion avenae, Hyalopterus pruni and Brevicoryne brassicae were identified by GC/MS studies. The main components found were triacylglycerols with one hexanoyl group. Fatty acid composition and position of triacylglycerols were determined from mass spectra. There was a trace of triacylglycerol with the E,E-2,4- hexadienoyl group in the extract of Brevicoryne brassicae. A series of hydrocarbons and free fatty acids were identified. Single components of straight chain aldehyde (C30) and alcohol (C32) were detected in the lipids of H. pruni, B. brassicae. Free fatty acids, including these found in the aphid lipids, were subjected to fungi-insect ecological studies. A homologous series of acids were added individually into media used to evaluate the mycelia growth and sporulation tests of the fungi, Beauveria bassiana and Paecilomyces fumosoroseus. The tests were performed in vitro and linear mycelial growth and sporulation of fungi after 14 days were measured. For both fungi, complete inhibition was observed with pentanoic and sorbic (E,E-2,4-hexadienoic) acids at a concentration as low as 0.02% w/v in both tests. Growth stimulation effects were only observed for B. bassiana with tetradecanoic and eicosanoic acid. Inhibitions were noticed for both fungi and the strongest effects were for dodecanoic (B. b.) and eicosanoic acid (P. f.). Beside free fatty acids, no other group of chemical compounds was found in the lipids which could be involved in aphids resistance to entomopathogenic fungi.

Regiospecific analysis of conifer seed triacylglycerols by gas-liquid chromatography with particular emphasis on delta5-olefinic acids.

Dibutyroyl derivatives of monoacylglycerols (DBMAG) from conifer seed oil triacylglycerols (TAG) were prepared by partial deacylation of TAG with ethylmagnesium bromide followed by diesterification with n-butyryl chloride. The resulting mixtures were analyzed by gas-liquid chromatography (GLC) with a 65% phenylmethyl silicon open tubular fused-silica capillary column operated under optimal conditions and separated according to both their fatty acid structures and their regiospecific distribution. Seed oils of 18 species from 5 conifer families (Pinaceae, Taxaceae, Cupressaceae, Cephalotaxaceae, and Podocarpaceae) were analyzed. The chromatograms showed a satisfactory resolution of DBMAG containing palmitic (16:0), stearic (18:0), taxoleic (cis-5,cis-9 18:2), oleic (cis-9 18:1), cis-vaccenic (cis-11 18:1), pinolenic (cis-5,cis-9,cis-12 18:3), linoleic (cis-9,cis-12 18:2), alpha-linolenic (cis-9,cis-12,cis-15 18:3), and an almost baseline resolution of DBMAG containing gondoic (cis-11 20:1), cis-5,cis-11 20:2, sciadonic (cis-5,cis-11,cis-14 20:3), dihomolinoleic (cis-11,cis-14 20:2), juniperonic (cis-5,cis-11,cis-14,cis-17 20:4), and dihomo-alphalinolenic (cis-11,cis-14,cis-17 20:3) acids. We have observed that results for Pinus pinaster and P. koraiensis seed oils obtained with this new simple method compared favorably with literature data established with other usual regiospecific analytical techniques. Delta5-olefinic acids are esterified mainly at the external positions of the glycerol backbone in all cases, in agreement with data obtained by other methodologies allowing validation of the GLC regiospecific method. To date, 45 gymnosperm species (mostly Coniferophytes) from 21 genera belonging to 9 families have been analyzed, all of them showing a definite enrichment of delta5-olefinic acids in the external positions of TAG. These fatty acids (FA), with one exception only, represent between approximately 2 and 8% of FA esterified to the internal positions. For some species, i.e., P. koraiensis and P. pinaster, this asymmetrical distribution was established by at least three analytical procedures and confirmed by stereospecific analysis of their seed TAG.