Occurrence of wax esters and 1-O-alkyl-2,3-diacylglycerols in goat epididymal sperm plasma membrane

Two unusual lipid classes were detected by thin-layer chromatography in the neutral lipids derived from goat cauda-epididymal sperm plasma membrane. The lipids were identified as wax esters and 1-O-alkyl-2,3-diacylglycerols based on chromatographic properties, identity of their hydrolysis products, and infrared/¹H nuclear magnetic resonance spectral evidence. The membrane containedca. 3 and 5 μg/mg protein of wax esters and alkyldiacylglycerols, respectively. The relative proportions of wax esters and alkyldiacylglycerols in the total neutral lipids were 1.5% and 2.4%, respectively. The lipids contained fatty acids with chain lengths of C₁₄ to C₂₂. The major fatty acids of the wax esters were 14∶0, 16∶0, 16∶1ω7, 18∶0 and 18∶1ω9. The fatty acids in alkyldiacylglycerol were 16∶0, 18∶0, 22∶5ω3 and 22∶6ω3. Alkyldiacylglycerol was particularly rich in docosahexaenoic acid 22∶6ω3) representing 30% of the total fatty acids. The alcohols of wax ester were all saturated with C₂₀–C₂₉ carbon chains. The deacylated products derived from alkyldiacylglycerols were identified as hexadecyl, octadecyl and octadec-9′-enyl glycerol ethers.     

Methodology for the In Vivo Measurement of the Δ<Superscript>9</Superscript>-Desaturation of Myristic,Palmitic, and Stearic Acids in Lactating Dairy Cattle

There is limited methodology available to quantitatively assess the activity of the Δ⁹-desaturase enzyme in vivo without chemically inhibiting the enzyme or using radioactively labeled substrates. The objective of these experiments was to develop methodology to determine the incorporation and desaturation of ¹³C-labeled fatty acids into milk lipids. In a preliminary experiment, 3.7 g [1-¹³C]myristic acid ([1-¹³C]14:0), 19.5 g [1-¹³C]palmitic acid ([1-¹³C]16:0), 20.0 g [1-¹³C]stearic acid ([1-¹³C]18:0) were combined and infused into the duodenum of a cow over 24 h. In a following experiment, 5.0 g [1-¹³C]14:0, 40.0 g [1-¹³C]16:0, and 50.0 g [1-¹³C]18:0 were infused into the abomasums of separate cows as a bolus over 20 min or continuously over 24 h. Milk fat was extracted using chloroform:methanol. Fatty acids were methylated, and fatty acid methyl esters (FAME) were converted to dimethyl disulfide derivatives (DMDS). The FAME and DMDS were analyzed by gas chromatography mass spectrometry. In the preliminary experiment, ¹³C enrichment in 14:0 but not 16:0 or 18:0 was observed. When dosage amounts were increased in the following experiment, peak enrichments from the bolus infusion were observed at 8 h. Enrichments for continuous infusion peaked at 16 h for 14:0 and 18:0, and at 24 h for 16:0. The Δ⁹-desaturase products of these fatty acids were estimated to be 90% of cis-9 14:1, 50% of cis-9 16:1, and 59% of cis-9 18:1. This study demonstrates that ¹³C-labeled fatty acids may be utilized in vivo to measure the activity of the Δ⁹-desaturase enzyme.     

Fatty Acyl-CoA Reductase and Wax Synthase from <Emphasis Type="Italic">Euglena gracilis</Emphasis> in the Biosynthesis of Medium-Chain Wax Esters

Euglena gracilis, a unicellular phytoflagellate, can accumulate a large amount of medium-chain wax esters under anaerobic growth conditions. Here we report the identification and characterization of two genes involved in the biosynthesis of wax esters in E. gracilis. The first gene encodes a fatty acyl-CoA reductase (EgFAR) involved in the conversion of fatty acyl-CoAs to fatty alcohols and the second gene codes for a wax synthase (EgWS) catalyzing esterification of fatty acyl-CoAs and fatty alcohols, yielding wax esters. When expressed in yeast (Saccharomyces cerevisiae), EgFAR converted myristic acid (14:0) and palmitic acid (16:0) to their corresponding alcohols (14:0Alc and 16:0Alc) with myristic acid as the preferred substrate. EgWS utilized a broad range of fatty acyl-CoAs and fatty alcohols as substrates with the preference towards myristic acid and palmitoleyl alcohol. The wax biosynthetic pathway was reconstituted by co-expressing EgFAR and EgWS in yeast. When myristic acid was fed to the yeast, myristyl myristate (14:0–14:0), myristyl palmitoleate (14:0–16:1), myristyl palmitate (14:0–16:0) and palmityl myristate (16:0–14:0) were produced. These results indicate EgFAR and EgWS are likely the two enzymes involved in the biosynthesis of medium-chain wax esters in E. gracilis.     

Cuticular lipids of insects: V. Cuticular wax esters of secondary alcohols from the grasshoppersMelanoplus packardii andMelanoplus sanguinipes

Wax esters of secondary alcohols constitute 18–20% of the cuticular lipid extract ofMelanoplus packardii and 26–31% of the cuticular lipids ofMelanoplus sanguinipes. The total number of carbons in the wax esters range from 37–54 with 41 predominating in both species. The fatty acids ofM. packardii wax esters are 16∶0, 18∶0, 14∶0, 20∶0 and 12∶0 in decreasing quantity. The fatty acids ofM. sanguinipes wax esters are 18∶0, 20∶0, 16∶0 22∶0, 14∶0, 19∶0 and 17∶0 in decreasing quantity. The secondary alcohols from the wax esters ofM. packardii are C₂₅, C₂₃ and C₂₇ in decreasing quantity, and the secondary alcohols of theM. sanguinipes are C₂₃, C₂₅, C₂₁, C₂₇, C₂₄, C₂₂ and C₂₆ in decreasing quantity. Each secondary alcohol consists of two to four isomers with the hydroxyl group located near the center of the chain. Montana Agriculture Experiment Station, Journal Series No. 332.     

θ3 fatty acids in freshwater fish from south brazil

Lipid and fatty acid levels in the edible flesh of 17 freshwater fish from Brazil’s southern region were determined. Analyses of fatty acid methyl esters were performed by gas chromatography. Palmitic acid (C_16:0) was the predominant saturated fatty acid, accounting for 50–70% of total saturated acids. Oleic acid (C_18:1θ9) was the most abundant monounsaturated fatty acid. Linoleic acid (C_18:2θ6), linolenic acid (C_18:3θ3), and docosahexaenoic acid (C_22:6θ3) were the predominant polyunsaturated fatty acids (PUFA). The data revealed that species such as truta, barbado, and corvina were good sources of eicosapentaenoic acid (C_20:5θ3) and docosahexaenoic acid (C_22:6θ3), and that most freshwater fish examined were good sources of PUFA θ3.     

Fatty Acid Composition in Ergosteryl Esters and Triglycerides from the Fungus Ganoderma lucidum

Free and esterified ergosterols are detected almost solely in fungi and are often employed as a biomarker of living fungi. In this work, the fatty acid composition and δ¹³C values of major fatty acids in triglycerides and ergosteryl esters from the fungus Ganoderma lucidum were analyzed by gas chromatography–mass spectrometer and gas chromatography–isotopic ratio mass spectrometer, respectively. The results showed that the fatty acid profiles varied in triglycerides and ergosteryl esters. The percentage of saturated fatty acids in ergosteryl esters was remarkably higher than that in triglycerides, where C_18:1^Δ9c was the predominant fatty acid and constituted 61.26 % of the total fatty acids. In contrast, C_16:0 was the predominant fatty acid and constituted 71.88 % of the total fatty acids in ergosteryl esters. The study suggests that, after fungal death, free ergosterols in the cell membrane of the dead fungus were esterified with preferentially saturated fatty acids, mainly C_16:0, from triglycerides and then stored in lipid particles for a longer period while free ergosterol markedly decreased. The δ¹³C values of C_16:0, C_18:0, C_18:1 and C_18:2 in ergosteryl esters exhibit a pronounced depletion in ¹³C compared with that in triglycerides within the range of ?1.3 to ?0.9 ‰, supporting the above inference. It is again suggested that free ergosterol in the cell membrane should be used as an indicator of living fungi, and ergosteryl esters in the lipid particles should not be included in the measurement of living fungal biomass.     

Characterization of skin-surface lipids from the monkey (Macaca fascicularis)

Skin-surface lipids from the monkeyMacaca fascicularis are composed of sterol esters (38%), cholesterol (4%) and two types of wax diesters, identified as Type II (IIa and IIb, 17% and 40%, respectively). Type IIa contained diesters of 1,2-alkanediols esterified with two molecules of long-chain (C₁₄−C₃₄) fatty acids having straight and branched chains. In the diesters IIa, fatty acids shorter than C₁₉ predominated in position 1, and fatty acids longer than C₂₀ predominated in position 2. Type IIb contained diesters of 1,2-alkanediols esterified with C₄ and C₅ branched-chain fatty acids (predominantly isovaleric acid) at position 1 and long-chain (C₁₄−C₂₇) acids, having straight and branched chains, at position 2. The shortchain acids were converted to 2-nitrophenylhydrazides and analyzed by high-performance liquid chromatography (HPLC). Ammonia chemical ionization (CI)-gas chromatography (GC)-mass spectrometry (MS) resolved the intact diesters IIb into 12 peaks corresponding to molecular weights ranging from 597 to 748, and showed that the molecular species, such as C₂₁−C₁₆−C₅ (diol, fatty acid in position 2, fatty acid in position 1), C₂₂−C₁₆−C₅ and C₂₃−C₁₆−C₅, were prevalent. The fatty acids from both diesters were mostly (>98%) saturated. The 1,2-alkanediols from both diesters consisted of C₁₆−C₂₆ saturated straight- and branched-chain components. The acyl groups of sterol esters contained 86% C₁₄−C₃₄ branched-chain acids. The unsaturated fatty acids (5.4%) belonged to a straight-chain monoenoic series having extremely long chains (C₁₈−C₃₄). The branched-chain structures in the fatty acids and diols were iso and anteiso. These results show the species-specific profile for the skin-surface lipid synthesis.     

Chemical Composition and Nutritional Characteristics of the Seed Oil of Wild <Emphasis Type="Italic">Lathyrus</Emphasis>, <Emphasis Type="Italic">Lens</Emphasis> and <Emphasis Type="Italic">Pisum</Emphasis> Species from Southern Spain

The fatty acid composition of the seed oil of 19 wild legume species from southern Spain was analyzed by gas chromatography. The main seed oil fatty acids ranged from C_14:0 to C_20:0. Among unsaturated fatty acids, the most abundant were linoleic, oleic and linolenic acids, except for Lathyrus angulatus, L. aphaca, L. clymenum, L. sphaericus and L. nigricans where C_18:3 contents were higher than C_18:1 contents. Palmitic acid was the most abundant saturated acid in studied species, ranging from 11.6% in Lathyrus sativus to 19.3% in Lens nigricans. All studied species showed higher amounts of total unsaturated fatty acids than saturated ones. Among studied species, the ω6/ω3 ratio was variable, ranging from 2.0% in L. nigricans to 13.8% in L. sativus, there being eight species in which the ω6/ω3 ratio was below 5. The fatty acids observed in these plants supports the use of these plants as a source of important dietary lipids.     

13C nuclear magnetic resonance spectroscopic analysis of the triacylglycerol composition ofBiota orientalis and carrot seed oil

¹³C nuclear magnetic resonance (NMR) spectroscopic analysis of the whole oil (triacylglycerols) ofBiota orientalis seeds confirms the presence of oleate [18:1(9Z)], linoleate [18:2(9Z, 12Z)], linolenate [18:3((9Z, 12Z, 15Z)], 20:3 (5Z, 11Z, 14Z), 20:4(5Z, 11Z, 14Z, 17Z), and saturated fatty acids in the acyl groups by comparing the observed carbon shifts with previously established shift data for model triacylglycerols. This technique shows that the saturated, 20:3 and 20:4 fatty acids are distributed mainly in the α-acyl positions, whereas oleate, linoleate, and linolenate are randomly acylated to the α- and β-positions of the glycerol “backbone”. Stereospecific hydrolysis of theBiota oil with pancreatic lipase, followed by chromatographic analysis of fatty esters, reveals the presence of trace amounts of 16:0(0.7%), 18:0(0.5%), 20:3 (0.4%), and 20:4 (1.3%) in the β-position of the glycerol “backbone”, which are undetectable by¹³C NMR technique on the whole oil. Semiquantitative assessment of the¹³C NMR signal intensities gives the relative percentages of the fatty acid distribution as: saturated 16:0, 18:0 (12.0% α-acyl), oleate (7.7% α-acyl 8.7% β-acyl), total linoleate and linolenate (31.7% α-acyl; 24.2% βacyl), total 20:3 and 20:4 (15.7% α-acyl). The¹³C NMR spectroscopic analysis of carrot seed oil identifies the presence of saturated (18:0), 18:1(6Z), 18:1(9Z), and 18:2(9Z, 12Z). The saturated fatty acid is found in the α-acyl positions. Semi-quantitative assessment of the signal intensities gives the relative percentages of the fatty acids as: 18:0 (4.5% α-acyl), 18:1(6Z) (49.6% α-acyl; 19.7% β-acyl), oleate (6.5% α-acyl; 8.6% β-acyl) and linoleate (5.2% α-acyl; 6.9% β-acyl).     

Authenticating Production Origin of Gilthead Sea Bream (<Emphasis Type="Italic">Sparus aurata)</Emphasis> by Chemical and Isotopic Fingerprinting

Recent EU legislation (EC/2065/2001) requires that fish products, of wild and farmed origin, must provide consumer information that describes geographical origin and production method. The aim of the present study was to establish methods that could reliably differentiate between wild and farmed European gilthead sea bream (Sparus aurata). The methods that were chosen were based on chemical and stable isotopic analysis of the readily accessible lipid fraction. This study examined fatty acid profiles by capillary gas chromatography and the isotopic composition of fish oil (δ¹³C, δ¹⁸O), phospholipid choline nitrogen (δ¹⁵N) and compound specific analysis of fatty acids (δ¹³C) by isotope ratio mass spectroscopy as parameters that could reliably discriminate samples of wild and farmed sea bream. The sample set comprised of 15 farmed and 15 wild gilthead sea bream (Sparus aurata), obtained from Greece and Spain, respectively. Discrimination was achieved using fatty acid compositions, with linoleic acid (18:2n-6), arachidonic acid (20:4n-6), stearic acid (18:0), vaccenic acid (18:1n-7) and docosapentaenoic acid (22:5n-3) providing the highest contributions for discrimination. Principle components analysis of the data set highlighted good discrimination between wild and farmed fish. Factor 1 and 2 accounted for >70% of the variation in the data. The variables contributing to this discrimination were: the fatty acids 14:0, 16:0, 18:0, 18:1n-9, 18:1n-7, 22:1n-11, 18:2n-6 and 22:5n-3; δ¹³C of the fatty acids 16:0, 18:0, 16:1n-7, 18:1n-9, 20:5n-3 and 22:6n-3; Bulk oil fraction δ¹³C; glycerol/choline fraction bulk δ¹³C; δ¹⁵N; % N; % lipid.     

Linear, steroidal, and triterpene esters, and steryl glycosides from Festuca argentina

Ester waxes and steryl glycosides of the grass Festuca argentina were studied. Saponification of the waxes from the petroleum ether extract led to n-hexacosanol as the major single linear alcohol, along with pentacyclic triterpenols, such as β-amyrin, germanicol, isobaurenol, lupeol, hopenol-a and hopeol, and low amounts of sterols, such as cholesterol, campesterol, stigmasterol, sitosterol and dihydrositosterol, identified by gas chromatography/mass spectrometry (GC/MS). Fatty acids were identified as methyl esters as C_12∶0, C_14∶0, C_16∶0, C_18∶0, C_18∶2, and C_20∶0. The occurrence of a wide chainlength range of fatty acids and a single linear alcohol closely matched for other reports on the tribe Festuceae. On the contrary, pentacyclic triterpenols with a variety of skeletons, especially isobauerenol, are not usual as esters of fatty acids in the Gramineae. Low amounts of steryl glycosides were also obtained from the methylene chloride percolate of the methanol extract. Upon acetylation followed by hydrolysis, aglycones were identified by capillary gas-liquid chromatography (GLC) and GC/MS. As Δ⁷-cholesterol, campesterol, stigmasterol, sitosterol, dihydrositosterol, and the sugars as glucose, xylose, and arabinose by GLC of the respective alditol acetates. This is the first report on the linear, steryl, and triterpenyl esters of F. argentina. It is noteworthy that Δ⁷-steryl glycosides are rare, and steryl monoarabinosides have not been proviously reported on the family Gramineae.     

Effect of growth conditions on the fatty acid composition ofListeria monocytogenes and comparison with the fatty acids ofErysipelothrix andCorynebacterium

Six strains ofListeria monocytogenes belonging to four different serotypes all had similar fatty acid profiles when grown at 37 C, with C₁₅ and C₁₇ branched chain acids as major components. The proportion of 17∶0 br decreased markedly as the growth temperature was lowered from 37 C to 4 C, and a reduction of 18∶1 with increasing age of cultures was observed in cells harvested at different stages of the growth curve. The fatty acid composition was also affected by the nature of the culture medium. Two other genera of the family Corynebacteriaceae were analyzed for fatty acid composition. Strains ofErysipelothrix rhusiopathiae isolated from human, turkey, dog and pig had rather similar patterns, consisting mainly of straight chain, even-numbered fatty acids from C₁₀ to C₁₈. The three species ofCorynebacterum analyzed each had quite different fatty acid patterns.C. poinsettiae bore some resemblance toL. monocytogenes butC. pseudodiphtheriticum had much higher proportions of 16∶0 and 18∶1 andC. equi contained a rather complex mixture of fatty acids. Part of this work was carried out in the Collip Medical Research Laboratory.     

Isovaleric acid as a precursor of odd numbered iso fatty acids in Tetrahymena

Tris isovalerate-supplementedTetrahymena pyriformis W showed no qualitative change in fatty acid composition; however, an increase in polar lipids that contain odd numbered iso acids (C₁₃, C₁₅, C₁₇, C₁₉) occurred. This change was accompanied by a decrease in the proportional amount of even numbered normal acids (C₁₄, C₁₆, C₁₈). The neutral and polar lipids from cells incubated with [1-¹⁴C] isovaleric acid were found to contain radioactivity. The methyl esters of the saturated fatty acids obtained from the polar lipids by alkaline methanolysis were separated by reversed phase chromatography, the identities confirmed by gas chromatography-mass spectrometry, and the specific activities determined. Iso acids were found to be the most heavily labeled materials. In addition to ceramide, two sphingolipid components were detected. One yielded saturated fatty acids after acidic methanolysis, while the other contained >93% α-hydroxy fatty acids. Radioactivity was noted in the long chain base fraction derived from the sphingolipids. Progressive growth inhibition occurred as the isovalerate concentration was increased in the culture medium; however, the ciliates were morphologically indistinguishable from unsupplemented cells.     

Pathways for fatty acid elongation and desaturation in Neurospora crassa

Neurospora crassa incorporated exogenous deuterated palmitate (16∶0) and ¹⁴C-labeled oleate (18∶1^Δ9) into cell lipids. Of the exogenous 18∶1^Δ9 incorporated, 59% was desaturated to 18∶2^Δ9,12 and 18∶3^Δ9,12,15. Of the exogenous 16∶0 incorporated, 20% was elongated to 18∶0, while 37% was elongated and desaturated into 18∶1^Δ9, 18∶2^Δ9,12, and 18∶3^Δ9,12,15. The mass of unsaturated fatty acids in phospholipid and triacylglycerol is 12 times greater than the mass of 18∶0. Deuterium label incorporation in unsaturated fatty acids is only twofold greater than in 18∶0, indicating a sixfold preferential use of 16∶0 for saturated fatty acid synthesis. These results indicate that the release of 16∶0 from fatty acid synthase is a key control point that influences fatty acid composition in Neurospora.     

Conversion of palmitate to unsaturated fatty acids differs in a Neurospora crassa mutant with impaired fatty acid synthase activity

The Neurospora crassa cel (fatty acid chain elongation) mutant has impaired fatty acid synthase activity. The cel mutant requires exogenous 16:0 for growth and converts 16:0 to other fatty acids. In contrast to wild-type N. crassa, which converted only 42% of the exogenous [7,7,8,8-²H₄]16:0 that was incorporated into cell lipids to unsaturated fatty acids, cel converted 72%. In addition, cel contains higher levels of 18:3^δ9,12,15 than wild-type, and synthesizes two fatty acids, 20:2^δ11,14 and 20:3^δ11,14,17, found at only trace levels in wild-type. Thus, the Δ15-desaturase activity and elongation activity on 18-carbon polyunsaturated fatty acids are higher for cel than wild-type. This altered metabolism of exogenous 16:0 may be directly due to impaired flux through the endogenous fatty acid biosynthetic pathway, or may result from altered regulation of the synthesis of unsaturated fatty acids in the mutant.     

The high content of monoene fatty acids in the lipids of some midwater fishes: Family myctophidae

The total lipids of eleven species of Myctophids caught at depths between 20 and 700 m in the northern Pacific Ocean were analyzed using silicic acid column chromatography (lipid classes) and capillary gas chromatography (fatty acid and fatty alcohol composition). The major components in the lipid classes were triacylglycerols or wax esters; triacylglycerols were the dominant acyl neutral lipids (68.1–96.1%) in eight species, and wax esters were found as the dominant lipid (85.5–87.9%) in three species. The major fatty acids and alcohols contained in the was esters of the three fishes were 18:1n–9, 20:1n–9, 20:1n–11, and 22:1n–11 for fatty acids, and 16:0, 18:1, 20:1, and 22:1 for fatty alcohols. Fatty acids in the triacylglycerols ranging from C₁₄ to C₂₂ were predominantly of even chain length. The major components were 16:0, 16:1n–7, 18:1n–9, 20:1n–11, 22:1n–11, 20:5n–3 (icosapentaenoic acid), and 22:6n–3 (docosahexaenoic acid). In both the triacylglycerols and the wax esters, the major fatty components were monoenoic acids and alcohols. It is suggested from the lipid chemistry of the Myctophids that they may prey on the same organisms as the certain pelagic fishes such as saury and herring, because the large quantities of monoenoic fatty acids are similar to those of saury, herring, and sprats whose lipids originate from their prey organisms such as zooplanktons which are rich in monoenoic wax esters.     

Characterization of chilean hazelnut (Gevuina avellana mol) seed oil

The fatty acid composition, tocopherol and tocotrienol content, and oxidative stability of petroleum benzene-extracted Gevuina avellana Mol (Proteaceae) seed oil were determined. Positional isomers of monounsaturated fatty acids were elucidated by gas chromatography-electron impact mass spectrometry after 2-alkenyl-4,4-dimethyloxazoline derivatization. This stable oil (Rancimat induction period at 110°C: 20 h) is composed of more than 85% monounsaturated fatty acids and about equal amounts (6%) of saturated and polyunsaturated (principally linoleic) fatty acids. Unusual positional isomers of monounsaturated fatty acids, i.e., C_16:1 Δ¹¹, C_18:1 Δ¹², C_20:1 Δ¹¹, C_20:1 Δ¹⁵, C_22:1 Δ¹⁷, and presumably C_22:1 Δ¹⁹ were identified. The C_18:1 Δ¹² and C_22:1 Δ¹⁹ fatty acids are described for the first time in G. avellana seed oil. While only minute quantities of α-, γ-tocopherols and β-, γ- and δ-tocotrienols were found, the oil contained a substantial amount of α-tocotrienol (130 mg/kg). The potential nutritional value of G. avellana seed oil is discussed on the basis of its composition.     

Lipase-catalyzed monoesterification of 1-O-hexadecylglycerol in organic solvents

A simple method is presented to esterify 1-O-hexadecyl-rac-glycerol using lipases in different organic solvents. The following fatty acids were used: C_14∶0, C_16∶0, C_18∶0, C_18∶1, and C_18∶2. Monoesterification was achieved by using a limiting amount of the fatty acid. Both the 1-O-hexadecyl-3-O-acylglycerol and the 2-O-acylglycerol were obtained in a total yield of 75% and a ratio of 7∶1 in dichloromethane after 3 d. Chromatographic data for the monoesters, useful for the identification of the natural products, are given (gas-liquid chromatography, thin-layer chromatography, reverse-phase thin-layer chromatography). The structure was confirmed by a chemical synthesis of 1-O-hexadecyl-2-O-hexadecanoylglycerol. The 3-O-glyceride was also formed by acyl migration, as the minor component. The monoesters were separated by column chromatography and characterized by ¹H and ¹³C nuclear magnetic resonance spectra.     

Unsaturated fatty acids of mycobacteria

The double bond locations have been determined for the mono-unsaturated fatty acids, C₁₄ to C₂₆ ofM. smegmatis andM. bovis BCG. The 14∶1 and 16∶1 fatty acids fromM. smegmatis are principally Δ¹⁰, while the 17∶1, 18∶1 and 19∶1 fatty acids from both organisms are Δ⁹. In the case ofM. smegmatis, the 20∶1, 22∶1 and 24∶1 fatty acids are principally Δ¹¹, Δ¹³ and Δ¹⁵, respectively, while the 22∶1, 24∶1 and 26∶1 fatty acids of BCG are principally Δ¹³, Δ¹⁵ and Δ¹⁷, respectively.     

The effect of lyophilization on the solvent extraction of lipid classes,fatty acids and sterols from the oysterCrassostrea gigas

The lipid class compositions of adult Pacific oysters [Crassostrea gigas (Thunberg)] were examined using latroscan thin-layer chromatography/flame-ionization detection (TLC/FID), and fatty acid compositions determined by capillary gas chromatography and gas chromatography/mass spectrometry (GC/MS). The fatty acid methyl esters were separated using argentation TLC and also analyzed as their 4,4-dimethyloxazoline derivatives using GC/MS. Major esterified fatty acids inC. gigas were 16∶0, 20∶5n−3, and 22∶6n−3. C₂₀ and C₂₂ nonmethylene interrupted (NMI) fatty acids comprised 4.5 to 5.9% of the total fatty acids. The NMI trienoic fatty acid 22∶3(7,13,16) was also identified. Very little difference was found in the proportions of the various lipid classes, fatty acids or sterols between samples of adult oysters of two different sizes. However, significant differences in some of the lipid components were evident according to the method of sample preparation used prior to lipid extraction with solvents. Lyophilization (freeze drying) of samples led to a significant reduction in the amounts of triacylglycerols (TG) extracted by solvents in two separate experiments (7.0 and 52.5% extracted). Extracts from lyophilized samples had less 16∶0, C₁₈ unsaturated fatty acids, and 24-ethylcholest-5-en-3β-ol, while C₂₀ and C₂₂ unsaturated fatty acids comprised a higher proportion of the total fatty acids. There was no significant change in the amounts of polar lipids, total sterols, free fatty acids or hydrocarbons observed in extracts from lyophilized samples relative to extracts from nonlyophilized samples. Addition of water to the freezedried samples prior to lipid extraction greatly improved lipid yields and resulted in most of the TG being extracted.