Postparturition changes in the triacylglycerols of cow colostrum

The changes in the triacylglycerol (TAG) composition of colostrum fat of three cows were studied. In addition to the determination of fatty acid composition by gas chromatography, the distribution of TAG according to the acyl carbon number (ACN) and molecular weight was analyzed utilizing both supercritical fluid chromatography (SFC) and ammonia negative-ion chemical ionization mass spectrometry (MS). Colostrum TAG contained substantially less stearic and oleic acids and more myristic and palmitic acids than the normal Finnish milk fat. The major trends in the changes of fatty acids and TAG were similar for each cow, although clear differences between individuals were found. During the first week of parturition, the proportions of short-chain fatty acids (C₄–C₁₀) typically increased as well as those of stearic and oleic acids, whereas the relative amounts of C₁₂–C₁₆ acids decreased, especially those of myristic and palmitic acids. Distinct changes occurred also in TAG distributions: the proportions of molecules with ACN 38–40 increased and those with ACN 44–48 decreased. Although there were distinct differences between individuals shortly after delivery, both the fatty acid compositions and TAG distributions of the milk samples of the cows started to resemble each other after one week. The theoretical profiles of colostrum TAG calculated based on the fatty acid compositions differed clearly from the ACN distributions analyzed by SFC and MS. Thus, the analysis of TAG is essential, because the changes in molecular species composition of colostrum TAG cannot be estimated according to the fatty acid analysis alone.     

Regioisomers of octanoic acid-containing structured triacylglycerols analyzed by tandem mass spectrometry using ammonia negative ion chemical ionization

Tandem mass spectrometry based on ammonia negative ion chemical ionization and sample introduction via direct exposure probe was applied to analysis of regioisomeric structures of octanoic acid containing structured triacylglycerols (TAG) of type MML, MLM, MLL, and LML (M, medium-chain fatty acid; L, long-chain fatty acid). Collision-induced dissociation of deprotonated parent TAG with argon was used to produce daughter ion spectra with appropriate fragmentation patterns for structure determination. Fatty acids constituting the TAG molecule were identified according to [RCO₂]⁻ ions in the daughter ion spectra. With the standard curve for ratios of [M-H-RCO₂H-100]⁻ ions corresponding to each [RCO₂]⁻ ion, determined with known mixtures of sn-1/3 and sn-2 regioisomers of structured TAG, it was possible to determine the proportions of different regioisomers in unknown samples. The method enabled quantification of MML- and MLM-type structured TAG. In the case of MLL- and LML-type TAG, it was possible to determine the most abundant regioisomer in the unknown mixture and estimate the proportions of regioisomers when there were more than 50% MLL-type isomers in the mixture.     

Pilot batch production of specific-structured lipids by lipase-catalyzed interesterification: Preliminary study on incorporation and acyl migration

Effects of water content, reaction time, and their relationships in the production of two types of specific-structured lipids (sn-MLM- and sn-LML-types: L-long chain fatty acids; M-medium chain fatty acids) by lipase-catalyzed interesterification in a solvent-free system were studied. The biocatalyst used was Lipozyme IM (commercial immobilized lipase). The substrates used for sn-MLM-type were fish oil and capric acid, and medium chain triacylglycerols and sunflower free fatty acids for sn-LML-type. The observed incorporation with the time course agrees well with the Michaelis-Menten equation, while the acyl migration is proportional to time within the range of 20 mol% acyl migration (MLM-type: M _f =0.2225 T, R²=0.98; LML-type: M _f =0.5618 T, R²=0.99). As water content (wt%, on the enzyme basis) increased from 3.0 to 11.6% for MLM-type and from 3.0 to 7.2% for LML-type in the solvent-free systems, the incorporation rates in the first 5 h increased from 3.34 to 10.30%/h, and from 7.29 to 11.12%/h, respectively. However, the acyl migration rates also increased from 0.22 to 1.12%/h and from 0.56 to 1.37%/h, respectively. Different effects in the production of two totally position-opposed lipids can be observed. Presumably these are caused by the different chain length of the fatty acids. The relationships between reaction time and water content are inverse and give a quantitative prediction of incorporation and acyl migration in selected reaction conditions and vice versa. The acyl migration can not be totally avoided in present systems, but can be reduced to a relatively low level. Acyl migration during the downstream processing has also been observed and other factors influencing the acyl migration are briefly discussed.     

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.     

Milk fat structure of a patient with type 1 hyperlipidemia

Structural analyses were performed on milk fat samples obtained 3–10 days postpartum from a lactating patient with primary Type 1 hyperlipidemia. The milk triacylglycerols contained 3–7% C₁₀, 14–21% C₁₂, 20–30% C₁₄, 22–26% C₁₆ and 20–30% C₁₈ (largely oleic) acids. Gas liquid chromatographic (GLC) analyses of the X-1,3- and X-1,2-diacylglycerols on polar siloxane columns showed a markedly non-random association of acyl chains. Stereospecific analyses indicated that the short chain length fatty acids were confined essentially to the sn-3-position of the triacylglycerol molecule. Furthermore, these acids were largely absent from the phosphatidylcholines and the endogenous sn-1,2-diacylglycerols of the milk fat. It is concluded that the short chain fatty acids are incorporated into the milk triacylglycerols during the final stage of biosynthesis via the phosphatidic acid pathway, and that the overall fatty acid distribution is consistent with the 1-random 2-random 3-random hypothesis.     

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.     

Capillary supercritical fluid chromatography-atmospheric pressure chemical ionization mass spectrometry of γ- and α-linolenic acid containing triacylglycerols in berry oils

The effect of the γ-linolenic acid (18:3n-6) residue on the elution of triacylglycerols on a 25% cyanopropyl-25% phenyl-50% methylpolysiloxane stationary phase was confirmed by using capillary supercritical fluid chromatography-atmospheric pressure chemical ionization mass spectrometry [cSFC-(APCI)MS]. The general elution rule on this stationary phase is that triacylglycerols having the same ACN+2n value coeluted (ACN-acyl carbon number and n=combined number of double bonds in the acyl chains). The different effect of γ- and α-linolenic acid residues on the retention of triacylglycerols and the use of cSFC-(APCI)MS allowed the study of the number of different linolenic acid residue isomer combinations in triacylglycerols with an identical ACN and degree of unsaturation. Stearidonic acid (18:4n-3) residue was found to have a similar effect on the retention behavior of triacylglycerols as that of γ-linolenic acid residue. The abundance of the [M-RCOO]⁺ ion, formed by the loss of one fatty acid moiety of a triacylglycerol, was found to be clearly higher in the case of γ-isomer of the linolenic acid than that of α-isomer in the identical regiospecific position. This indicates that the distance of the double bonds from the glycerol backbone in the acyl chain affects the stability of a triacylglycerol molecule in the (APCI)MS system. The triacylglycerol composition and the fatty acid combinations of triacylglycerols were found to be almost identical in black currant (Ribes nigrum) and alpine currant (R. alpinum) seed oils.     

Triacylglycerols of winter butterfat containing configurational isomers of monoenoic fatty acyl residues. I. Disaturated monoenoic triacylglycerols

The triacylglycerols of winter butterfat were fractionated according to the type and degree of unsaturation into six fractions by silver ion high-performance liquid chromatography (Ag-HPLC). The acyl carbon number distribution of the triacylglycerols in each fraction was elucidated by reversed-phase HPLC and mass spectrometry (MS). The MS analysis of each fraction gave deprotonated triacylglycerol [M - H]⁻ ions which were produced by chemical ionization with ammonia. The daughter spectrum of each of the [M - H]⁻ ions provided information on its fatty acid constituents. Successful fractionation of triacylglycerols differing in the configuration of one fatty acyl residue by Ag-HPLC was important because geometrical isomers could not be distinguished by the MS system used. In addition to the fatty acid compositions, reversed-phase HPLC analysis demonstrated the purity of the collected fractions: molecules having acis-trans difference were separated nearly to the baseline. Triacylglycerols differing in the configuration of one fatty acyl residue were not equally distributed in relation to their acyl carbon numbers. This indicates that during the biosynthesis of triacylglycerols,cis- andtrans-fatty acids are processed differently. Although the fatty acid compositions of the corresponding molecular weight species of disaturatedtrans- and disaturatedcis-monoenoic triacylglycerols were similar, there may be differences in the amounts of different fatty acid combinations or in the distribution of fatty acids between the primary and secondary glycerol positions. In addition to the main components, it was possible to analyze minor triacylglycerols, such as molecules containing one odd-chain fatty acid, by the MS system used.     

Two-step enzymatic synthesis of docosahexaenoic acid-rich symmetrically structured triacylglycerols via 2-monoacylglycerols

Symmetrically structured triacylglycerols (TG) rich in docosahexaenoic acid (DHA) with caprylic acid (CA) at the outer positions were synthesized enzymatically form bonito oil in a two-step process: (i) ethanolysis of bonito oil TG to 2-monoacylglycerols (2-MG) and fatty acid ethyl esters, and (ii) reesterification of 2-MG with ethyl caprylate. Ethanolysis catalyzed by immobilized Candida antarctica lipase (Novozym 435) yielded 92.5% 2-MG with 43.5% DHA content in 2 h. The 2-MG formed were reesterified with ethyl caprylate by immobilized Rhizomucor miehei lipase (Lipozyme IM) to give structured TG with 44.9% DHA content [based on fatty acid composition with caprylic acid (CA) excluded] in 1 h. The final structured lipids comprised 85.3% TG with two CA residues and one original fatty acid residue, 13% TG with one CA residue and two original fatty acid residues, and 1.7% tricaprylolglycerol (weight percent). The amount of TG with two CA residues and one C₂₂ residue (22∶6=DHA, 22∶5, and 22∶4) was 51 wt%. The 1,3-dicapryloyl-2-docosahexaenoylglycerol to 1,2(2,3)-dicapryloyl-3 (1)-docosahexaenoylglycerol ratio (based on high-performance liquid chromatography peak area percentages) was greater than 50∶1. The recovery of TG as structured lipids after silica gel column purification was approximately 71%. Ethyl esters and 2-MG formed at 2 h of ethanolysis could be used to determine the positional distribution of fatty acids in the intial TG owing to the high 1,3-regiospecificity of Novozym 435 and the reduced acyl migration in the system.     

Comparative study of the molecular species of chloropropanediol diesters and triacylglycerols in milk fat

In an effort to establish the origin of the fatty acid esters of 3-chloropropanediol, which recently have been isolated in small amounts from goat milk, we compared the molecular species composition of the chlorohydrin diesters and of goat milk triacylglycerols. The chloropropanediol diesters were found to be composed of molecular species containing C₁₀−C₁₈ fatty acids and corresponded closely in carbon number to those calculated for the long chain sn-1,2-diacyl-glycerol moieties of goat milk triacylglycerols. The molecular species of goat milk total triacylglycerols contained C₄−C₁₈ fatty acids. It is suggested that triacylglycerols and chloropropanediol diesters are derived from the same pool of long chain fatty acids. A molecular distillate of bovine milk fat did not contain chloropropanediol diesters, while the available samples of human milk fat were shown to contain alkyldiacylglycerols as the major components of a neutral lipid fraction corresponding in polarity to the chloropropanediol diesters.     

Stereospecific analysis of triacylglycerols and major phosphoglycerides fromLipomyces lipoferus

The stereospecific distribution of fatty acids in triacylglycerols, phosphatidylcholines and phosphatidylethanolamines ofLipomyces lipoferus was determined. Position sn-1 of the triacylglycerols had a predominance of unsaturated fatty acids of which C_18∶1 (61%) was the major component. Position sn-2 of the triacylglycerols contained 88% C_18∶1 and was more unsaturated than position sn-1 by 24.6%. Position sn-3 had equal proportions of saturated and unsaturated fatty acids. Phosphatidylcholine had a quantitatively distinctive fatty acid distribution in that position sn-2 was 26.7% more unsaturated than position sn-1. In phosphatidylethanolamine, position sn-2 was 10.8% more unsaturated than position sn-1. Positions sn-1 and sn-2 of these phosphoglycerides had a different fatty acid profile from positions sn-1 and sn-2 of the triacylglycerols. These results suggest a nonrandom distribution of fatty acids in the triacylglycerols and phosphoglycerides. Because triacylglycerols and phosphoglycerides are both derived from 1,2-diacylglycerols, these data suggest two possibilities: some selectivity in utilization of species of diacylglycerols to form triacylglycerols and phosphoglycerides or modification of the triacylglycerols and phosphoglycerides after they are formed or both. This study is the first of its kind in a yeast. Presented in part at the AOCS Fall Meeting, Ottawa, Canada, September 1972.     

Synthesis, purification, and characterization of structured lipids produced from chicken fat

A structured lipid (SL) was synthesized enzymatically from chicken fat by incorporating a medium-chain length fatty acid (caprylic acid) into chicken fat triacylglycerols. Carica papaya latex was used as the biocatalyst. The optimal substrate mole ratio found was 1∶2 (chicken fat fatty acids/caprylic acid). At this ratio of reactants, the incorporation of caprylic acid (C_8∶0) at 65°C was 23.4 mol%, whereas at 55°C the incorporation of caprylic acid was 17.6 mol%. A packed-bed column bioreactor was designed for the synthesis of SL from chicken fat. In using ground crude C. papaya latex (a _w <0.1), 7.1 mol% of caprylic acid was incorporated into the chicken fat triacylglycerols after 117 min of reactor residence time. After purification of the SL, the acyl positional distribution of fatty acids on the glycerol backbone was determined by ¹³C nuclear magnetic resonance (NMR) spectroscopy. From the NMR spectrum of the SL, it was determined that saturated fatty acyl residues at the 1,3-positions of the SL triacylglycerols increased to 62% over that of the starting chicken fat triacylglycerols, suggesting that caprylic acid was preferentially incorporated at the 1,3-positions. In addition, differential scanning calorimetry thermograms were obtained to compare the crystallization characteristics of the starting chicken fat with the SL prepared from it. This work was presented at the Biocatalysis Symposium in April 2000, held at the 91st Annual Meeting and Expo of the American Oil Chemists Society, San Diego, CA.     

A cross-species comparison of neutral lipid composition of milk fat of prosimian primates

The fatty acid composition of milk fat is known to be affected by dietary and genetic differences, while the milk triacylglycerol structure is believed to be attuned to the needs of the subsequent lipolysis during gastrointestinal passage. The availability of milk samples from eight species of prosimian primates, whose milk triacylglycerol structure had not been analyzed, offered an opportunity to further assess these ideas. The milk samples were collected by manual expression and the lipids extracted with chloroform/methanol (2∶1, vol/vol). The lipid classes were resolved by thin-layer chromatography, and the neutral lipids subjected to detailed analyses by capillary gas-liquid chromatography of fatty acids and molecular species of triacylglycerols using nonpolar and polarizable liquid phases. The milk samples were found to differ greatly in total fat content (4–73%) and in the composition of the neutral liqid classes and molecular species. The concentration of triacylglycerols ranged from 88–95%, free fatty acids from 0.5–10%, alkyldiacylglycerols from 0.5–5.0%, and diacylglycerols, monoacylglycerols and free and esterified cholesterol made up the remainder. The fatty acid chain length ranged from C₈−C₂₄, with palmitic (16–31%) and oleic (13–40%) acids being the major components in most of the species. In all instances, the molecular association of the fatty acids differed from random distribution by a higher proportion of the monoacid (trioleoyl) and diacid (dipalmitoyloleoyl) glycerols. The phylogenetic influences on neutral milk lipid composition, however, remained unclear, as some of the differences between closely related species were greater than those between more distantly related ones. Triacylglycerol structures are abbreviated by listing their three constituent fatty acids in sequence, e.g., PPP, LaOL.     

Characterization of α- and γ-linolenic acid oils by reversed-phase high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

Triacylglycerols of oils rich in α- and/or γ-linolenic acids were analyzed by reversed-phase high-performance liquid chromatography (HPLC) coupled with atmospheric pressure chemical ionization mass spectrometry [(APCI)MS]. The (APCI)MS spectra of most triacylglycerols exhibited [M + H]⁺ and [M - RCOO]⁺ ions, which defined the molecular weight and the molecular association of fatty acyl residues, respectively. Reversed-phase HPLC resulted in, at least, partial separation of triacylglycerols containing α- and/or γ-linolenic acid moieties. Molecules containing α-linolenic acid residues exhibited a relatively weaker retention by the stationary phase than the corresponding molecules containing γ-linolenic acid residues. Good separation of triacylglycerols of cloudberry seed oil, evening primrose oil, borage oil, and black-currant seed oil was achieved. The molecular species identification of separated components was based on the (APCI)MS data as well as on the elution properties of triacylglycerols on reversed-phase HPLC. This study demonstrated the efficiency of HPLC-(APCI)MS in determining the molecular species compositions of triacylglycerols in complex natural mixtures. Good quality mass spectra could be extracted even from minor chromatographic peaks representing 0.2% or less of the total triacylglycerols.     

Molecular species and fatty acid distributions of triacylglycerols from germinating soybean cotyledons

Molecular species and fatty acid distributions of triacylglycerols obtained from cotyledons of soybean seedlings were investigated. Changes observed in triacylglycerol content were closely related to levels of total lipids present in the cotyledons. At day 12 of seedling growth, ca. 85% of triacylglycerols had been consumed. Immediately after the beginning of imbibition the oil consisted of triacylglycerols with even carbon numbers (from C-50 to C-60) based on the combined length of the fatty acyl chains present in a triacylglycerol. The dominant components throughout germination were C-52 and C-54 triacylglycerols. Fourteen molecular species of triacylglycerols were identified in the cotyledons. As soybean seedlings grew, the percentages of triacylglycerols decreased to 0.9–36.2% during the 12 days. Triacylglycerols containing one or more saturated fatty acids were hydrolyzed slightly faster than other species. Unsaturated fatty acids were dominant in the 2-position throughout germination. These results suggest the mechanism of initial triacylglycerol hydrolysis may be different in various molecular species.     

High-performance liquid chromatography with light-scattering detection and desorption chemical-ionization tandem mass spectrometry of milk fat triacylglycerols

The utility of reverse-phase high-performance liquid chromatography (HPLC), desorption chemical-ionization mass spectrometry (DCI-MS) and tandem mass spectrometry (MS/MS) for the characterization of triacylglycerols in complex mixtures has been further explored. Triacylglycerols of anhydrous bovine milk fat were separated by using two reversephase C₁₈ HPLC columns, and eluents were monitored with an evaporative light-scattering detector. Fifty-eight fractions were resolved and analyzed by positive ion isobutane DCI-MS. The formation of protonated molecules and of major fragments corresponding to the random loss of any one of the constituent fatty acids readily identified acyl carbon numbers and the number of double bonds within each fatty acid. MS/MS was only required when the original mass spectra indicated the presence of more than one triacylglycerol or of impurities in a fraction. Protonated molecules produced by DCI were fragmented using high energy collisional activation, and the resulting ions were detected by MS/MS. Odd-chain triacylglycerols were also readily distinguished using this methodology. The positive ion DCI and MS/MS techniques described here demonstrate the usefulness of this approach for the characterization of triacylglycerols in complex mixtures.     

Purification of specific structured lipids by distillation: Effects on acyl migration

The cause and effects of acyl migration during the purification of specific structured lipids by distillation were studied in a conventional batch deodorizer with stripping steam. The mixture of specific structured lipids produced by lipase-catalyzed acidolysis between rapeseed oil and capric acid contained a large amount of free fatty acids and a small amount of partial acylglycerols besides triacylglycerols. Therefore, the effect of steam, free fatty acids, diacylglycerols, and monoacyl-glycerols on acyl migration was studied in a palm oil midfraction model. The results showed that all these factors influenced the rate of acyl migration, and their combinations made the effect more severe. However, diacylglycerols were found to be the main reason for acyl migration. In the distillation of the specific structured lipid product mixture, distillation temperature and time were the main factors to determine the degree of acyl migration and the extent of separation of free fatty acids. The results indicate that more efficient separation technology should be used to improve the quality of the purified structured lipids. In order to reduce the distillation temperature, vacuum should be made as low as possible with more effective pumps. To reduce the distillation time, thin-film principle in a packed column should be used, or other more efficient distillation techniques such as molecular distillation or short-path distillation should be exploited.     

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.     

1-O-alkyl-2,3-diacylglycerols in the skin surface lipids of the hairless mouse

A neutral lipid class was isolated by thin-layer chromatography from the skin surface lipids of the hairless mouse. The fraction migrated faster than triglycerides and had a migration rate similar to that of diacyl alkanediols (diester wax). Upon deacylation, however, the long-chain diols were identified as 1-alkylglycerol ethers based on their chromatographic properties and on the mass spectra of their nicotinylidene derivatives. Thus, the skin lipid fraction was identified as 1-O-alkyl-diacylglycerol. The alkyl moieties were all saturated and even-numbered and ranged in chainlength from C₁₆ to C₂₂ with 1-O-hexadecylglycerol amounting to 34% of the total glycerol ether moieties. The fatty acids derived from this lipid fraction were mostly monoenoic with chainlengths ranging from C₁₆ to C₂₄. The major acyl component was eicosenoic acid (20∶1) representing 61% of the total fatty acids.     

The steryl ester and phospholipid fatty acids of the spongeAgelas conifera from the Colombian Caribbean

The steryl ester and phospholipid fractions of the marine spongeAgelas conifera were isolated and analyzed. The fatty acyl components of the steryl ester and phospholipid fractions as determined by gas chromatography and gas chromatography/mass spectrometry were very similar and consisted of 56.8 and 62.7% of C₁₄−C₂₀ acids (normal; branched, especiallyiso andanteiso; and monounsaturated, particularly Δ⁹ and Δ¹¹ acids) and of 43.1 and 35.5% of C₂₄−C₂₆ acids (Δ^5,9 diunsaturated acids), respectively. The major constituent fatty acids detected were 13-methyltetradecanoic,n-hexadecanoic, 10-methylhexadecanoic, 11-octadecenoic, 12-methyloctadecanoic, 5,9-pentacosadienoic and 5,9-hexacosadienoic acids. The phospholipids isolated were identified as phosphatidylcholine (37%), phosphatidylserine (34%), phosphatidylethanolamine (16%) and phosphatidylinositol (11%). The distribution of fatty acids within the phospholipid classes was also determined.