Characterization of astaxanthin esters in Haematococcus pluvialis by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

After first being analyzed by HPLC, 4 free carotenoids, 15 astaxanthin monoesters, 12 astaxanthin diesters, and 3 astacin monoesters in Haematococcus pluvialis were identified by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry (LC-(APCI)MS). Identification of each compound was based on the characteristic fragment ions of the positive ion mode, negative ion mode, and MS(2). Astaxanthin esters were identified based on the loss of one or two fatty acids. In a positive ion mode, astaxanthin monoesters had characteristic fragment ions at m/z 597 [M+H-fatty acid](+) and m/z 579 and 561 that resulted from a continuous loss of water. The relative intensity of m/z 579 in MS(2) amounted to more than 80% of that of the molecular ion. In astaxanthin diesters, the intensity of m/z 561 occasionally was equal to that of m/z 579, but in general the former, amounting to 50 to 60% or more of the molecular ion, was stronger than the latter, which decreased to 20 to 30% of the molecular ion. In addition, a set of compounds with maximum absorbance at 400 nm, detected by high-performance liquid chromatography-diode array detector (HPLC-DAD), had strong characteristic fragment ions at m/z 871 and 593 in the positive ion mode MS(2). They were presumed to be linolenic acid or an isomer of omega-6-gamma-linolenic acid esters of astacin.     

Chemical analysis of and degradation studies on the cell wall lipopolysaccharide of Rhodopseudomonas capsulata

A lipopolysaccharide (LPS) has been isolated from the gram-negative photosynthetic bacterium Rhodopseudomonas capsulata. Chemical analysis revealed the presence of d-glucose, d-galactose, l-rhamnose, 3-O-methyl-l-rhamnose (l-acofriose), d-glucosamine, 2-keto-3-deoxyoctonate, and neuraminic acid. The LPS does not contain l-glycero-d-mannoheptose, a typical component of the LPS of enteric bacteria. Fatty acid analysis showed that, apart from lauric acid, two hydroxy fatty acids (hydroxycaproic and hydroxymyristic acids) are the main components. By hydrolysis in weak acid, the LPS has been separated into a polysaccharide part (degraded polysaccharide) and a lipid part (lipid A). Presumably the lipid A contains a glucosamine backbone. Whereas the OH-groups of glucosamine are esterified with lauric and hydroxycaproic acids, hydroxymyristic acid is linked to the amino group of the sugar. By separation of the degraded polysaccharide by gel filtration, a fraction has been isolated which inhibited hemagglutination in a system containing antiserum, obtained by immunization of rabbits with whole cells, and isolated LPS. This fraction, which includes the determinant group, contains the sugars glucose, rhamnose, and acofriose. A second fraction obtained in this way was found to be serologically inactive and is composed of glucose, galactose, neuraminic acid, and phosphate.     

Gas chromatographic-mass spectrometric detection of 2- and 3-hydroxy fatty acids as methyl esters from soil,sediment and biofilm

Hydroxy fatty acids (OH-FAs) can be used in the characterization of microbial communities, especially Gram-negative bacteria. We prepared methyl esters of 2- and 3-OH-FAs from the lipid extraction residue of soil, sediment, and biofilm samples without further purification or derivatization of hydroxyl groups. OH-FA methyl esters were analyzed using a gas chromatograph equipped with a mass selective detector (GC-MS). The ions followed in MS were m/z 103 for 3-OH-FAs and m/z 90 and M-59 for 2-OH-FAs. The rapid determination of 3- and 2-OH-FAs concomitantly with phospholipid fatty acids provided more detailed information on the microbial communities present in soil, sediment, and drinking water biofilm.     

Analysis of polyunsaturated aminophospholipid molecular species using isotope-tagged derivatives and tandem mass spectrometry/mass spectrometry/mass spectrometry

When aminophospholipids with only saturated and monounsaturated fatty acids esterified to the glycerol backbone were labeled with isotopically enriched N-methylpiperazine acetic acid N-hydroxysuccinimide ester reagents, it was found that they could be readily detected as N-methylpiperazine-amide-tagged aminophospholipids using a precursor scan of the stable isotope reporter ion (m/z 114-117) formed by tandem mass spectrometry/mass spectrometry. However, it was found in the current study that these precursor ion scans are not useful in determining the changes of aminophospholipids with polyunsaturated fatty acids (PUFAs) esterified to the glycerol backbone due to the presence of interfering ions in the reporter ion region. Therefore, a method was developed using tandem mass spectrometry/mass spectrometry/mass spectrometry (MS(3)) to obtain reporter ion ratios that were not distorted by interfering ions present in the collision-induced dissociation spectra of nontagged aminophospholipids with PUFAs. This new MS(3) method for N-methylpiperazine- amide-tagged aminophospholipids was used to examine the fate of diacyl, ether, or plasmalogen glycerophosphoethanolamine (GPEtn) species after exposure of human polymorphonuclear leukocytes to A23187 and granulocyte macrophage-colony-stimulating factor/formyl-methionyl-leucyl-phenylalanine stimuli, which can induce eicosanoid biosynthesis, to follow those GPEtn molecular species which were the source of arachidonic acid released. Upon stimulation of the human polymorphonuclear leukocyte, it was found that the abundant arachidonoyl GPEtn plasmalogen molecular species were uniquely reduced in relative content compared to ether or diacyl species and this subclass of GPEtn may be a source of the arachidonic acid converted to leukotrienes by the 5-lipoxygenase pathway activated in this cell.     

Liquid ionization mass spectrometry of phospholipids

Several phosphatidylcholines (PC) and a phosphatidylethanolamine (PE) were subjected to liquid ionization (LI) mass spectrometry, in which a sample is ionized through energy transfer from metastable argon atoms under atmospheric pressure. Commercially available and synthesized, saturated or unsaturated fatty acid containing phospholipids and their mixtures were studied. A sample either as a concentrated chloroform-methanol solution or with glycerol (matrix) gave characteristic peaks such as MH+ and four fragment ions. One of the fragment ions (e.g., m/z 551 of PC 16:0, 16:0) containing both fatty acid residues has been commonly observed with other ionization methods such as CI, FD, and FAB, but the other fragment ions have not been observed in other mass spectra with one exception on desorption CI. Ions b and d (e.g., m/z 464 and 328, respectively, for PC 16:0, 16:0) contain one fatty acyl residue and the other ion containing the phosphorylcholine moiety appears at m/z 196 for PC. Thus the masses of the MH+ ion and these fragment ions provide useful structural information even in the case of a mixture. The ion b (e.g., m/z 488 of PC 18:0, 18:2) observed during an early period of heating was formed mainly by the loss of one acyl group at sn-1 of the glycerol backbone and thus may be used to differentiate the positional specificities of the constituent fatty acids. The temperature of the sample, however, should be controlled precisely, because it has a significant effect on the mass spectrum. The present method (LI) also provided useful information for a mixture of PC and PE.     

Identification of carotenoid pigments and their fatty acid esters in an avian integument combining HPLC-DAD and LC-MS analyses

Yellow-orange-red ornaments present in the integuments (feathers, bare parts) of birds are often produced by carotenoid pigments and may serve to signal the quality of the bearer. Although carotenoid esterification in tissues is a common phenomenon, most of the work on avian carotenoids has been focused on the identification of free forms or have been done after sample saponification. Here we determined free and esterified carotenoid composition in a bird species with red ornaments: the red-legged partridge (Alectoris rufa). Carotenoids from leg integument were extracted and processed by TLC to separate three major carotenoid groups (free form, mono- and diesters with fatty acids), whereas saponified extracts gave only free forms of carotenoids. TLC fractions were then analyzed by HPLC-DAD with C18 phase column for a preliminary identification of carotenoid groups. The final characterization of free carotenoids and its esters with fatty acids was performed with direct extracts analyzed by LC-MS and LC-MS/MS with a C30 phase, always with a system coupled to DAD. The main carotenoid (λ(max) 478 nm and [M+H](+) at m/z 597.2) was identified as astaxanthin by comparison with standards. A second carotenoid (λ(max) between 440 and 480 nm and [M+H](+) at m/z 581.3) was not identified among any of the commercially available carotenoid standards, although it could correspond to pectenolone according to its fragmentation pattern. Both the unidentified carotenoid and astaxanthin formed monoesters with fatty acids, but only astaxanthin was in its diesterified form. Monoesters were mainly formed with palmitic, stearic, oleic and linoleic acids. Complementary analyses of fatty acid composition in partridge integument by GC-MS revealed high amounts of these and other fatty acids, such as myristic, arachidic and docosanoic acids. The combination of HPLC-DAD and LC-MS/MS spectra was especially useful to identify the carotenoids present in the esterified forms and the probable masses of the fatty acids included in them, respectively.     

Characterization of linoleic acid nitration in human blood plasma by mass spectrometry

Nitric oxide (*NO) is a pervasive free radical species that concentrates in lipophilic compartments to serve as a potent inhibitor of lipid and low-density lipoprotein oxidation processes. In this study, we synthesized, characterized, and detected nitrated derivatives of linoleic acid (18:2) in human blood plasma using high-pressure liquid chromatography coupled with electrospray ionization tandem mass spectrometry. While the reaction of nitronium tetrafluoroborate with 18:2 presented ions with a mass/charge (m/z) ratio of 324 in the negative ion mode, characteristic of nitrolinoleate (LNO(2)), the reaction of nitrite (NO(2)(-)) with linoleic acid hydroperoxide yielded nitrohydroxylinoleate (LNO(2)OH, m/z 340). Further analysis by MS/MS gave a major fragment at m/z 46, characteristic of a nitro group (-NO(2)) present in the parent ion. This was confirmed by using [(15)N]O(2), which gave products of m/z 325 and 341, that after fragmentation yielded a daughter ion at m/z 47. Moreover, a C-NO(2) structure was also demonstrated in LNO(2)OH by nuclear magnetic resonance spectroscopy ((15)N NMR, delta 375.9), as well as by infrared analysis in both LNO(2)OH (nu(max) = 3427, 1553, and 1374 cm(-1)) and LNO(2) (nu(max) = 1552 and 1373 cm(-1)). Stable products with m/z of 324 and 340, which possessed the same chromatographic characteristics and fragmentation pattern as synthesized standards, were found in human plasma of normolipidemic and hyperlipidemic donors. The presence of these novel nitrogen-containing oxidized lipid adducts in human plasma could represent "footprints" of the antioxidant action of *NO on lipid oxidation and/or a pro-oxidant and nitrating action of *NO-derived species.     

Application of electrospray ionization MS/MS and matrix-assisted laser desorption/ionization-time of flight mass spectrometry to structural analysis of the glycosyl-phosphatidylinositol-anchored protein.

We applied the improved sensitivity and soft ionization characteristics of electrospray Ionization (ESI)-MS/MS and matrix-assisted laser desorption/ionization(MALDI)-time of flight (TOF) mass spectrometry (MS) to analysis of the GPI-anchored C-terminal peptide derived from 5'-nucleotidase. ESI-MS/MS analysis was applied to the core structure (MW, 2,743). In the collision-induced dissociation (CID) spectrum, single-charged ions such as m/z 162 (glucosamine), 286 (mannose-phosphate-ethanolamine), and 447 ([mannose-phosphate-ethanolamine]-glucosamine) were clearly detected as characteristic fragment ions of the GPI-anchored peptide. On MALDI-TOF-MS analysis, heterogeneous peaks of GPI-anchored peptides were detected as single-charged ions in the positive mode. Product ions were obtained by post-source decay (PSD) of m/z 2,905 using curved field reflectron of TOF-MS. Most of the expected product ions derived from the GPI-anchored peptide, containing the core structure and an additional mannose side chain, were successively obtained. Thus, ESI-MS/MS and MALDI-TOF-PSD-MS proved to be effective and sensitive methods for analyzing the GPI-anchored peptide structure with less than 10 pmol of sample. These characteristic fragments or fragmentation patterns seem to be very useful for identification of GPI-anchored C-terminal peptides derived from any kind of GPI-anchored protein.     

Purification and structural determination of nontoxic lipid A obtained from the lipopolysaccharide of Salmonella typhimurium

Endotoxin extracted from the heptose-less mutant of Salmonella typhimurium was hydrolyzed in 0.1 N HCl in methanol/water (1:1, v/v) at 100 degrees C to yield lipid A, which was then fractionated on a Sephadex LH-20 column to yield a major monophosphoryl lipid A fraction. The monophosphoryl lipid A was further fractionated by preparative thin layer chromatography. This process yielded three major bands (TLC-1, -3, and -5) and two minor bands (TLC-7 and -9). The purity of these fractions was established by ion exchange and reverse phase high performance liquid chromatography. The thin layer fractions were analyzed by fast atom bombardment mass spectrometry. TLC-1 and -3 gave molecular ions (M-H)- at m/e 1730 and 1716, respectively. Both of these fractions contained beta-hydroxymyristic, lauric, and 3-myristoxymyristic acids in O-acyl linkages. The molecular formula and Mr of TLC-1 are C95H179O22N2P and 1731.16; those of TLC-3 are C94H177O22N2P and 1717.15. TLC-1 was a methyl homolog of TLC-3. The major component of TLC-5 (C80H151O22N2P and Mr = 1506.99) gave a molecular ion at m/e 1506 and contained two beta-hydroxymyristic acids and a lauric acid in the O-acyl linkages. The major component of TLC-7 (C66H125O19N2P and Mr = 1280.83) and the single component of TLC-9 gave molecular ions at m/e 1280 and 1098, respectively. TLC-7 contained lauric and beta-hydroxymyristic acids in the O-acyl linkages. TLC-9 (C54H103O18N2P and Mr = 1098.69) contained a single O-acylated beta-hydroxymyristate group. TLC-1 and -3 were nontoxic in the chick embryo lethality test and regressed established tumors in the syngeneic guinea pigs.     

Effects of two different medium-chain triglycerides (tri C8:O and tri C12:O) on liver lipids in the growing rat.

Results presented in this study emphasize the long-term effects of dietary fatty acid chain length on some biochemical parameters of the liver in the growing rat. High levels of medium-chain fatty acids feeding (C8:O and C12:O) from 40 to 340 g of body weight induced liver growth and lipid contents intermediary between values recorded with a lipid-free diet and with a diet containing long-chain fatty acids. No steatosis was recorded but neutral lipid contents appeared to be correlated with the dietary fatty acid chain length while phospholipid contents remained much more stable. In the four tested nutritional conditions, only dodecano?c or lauric acid (C12:O) feeding induced important alterations in the fatty acid pattern of liver neutral lipids. Medium-chain fatty acids, and even lauric acid which was intensely esterified in adipose tissue triglycerides, did not appreciably modify the fatty acid composition of liver phospholipids and were not esterified in it.     

Determination of double bond positions of unsaturated fatty acids by a chemical ionization mass spectrometry computer system

After stereospecific oxidation, trimethylsilylated methyl esters of mono- and diunsaturated fatty acids were analyzed by combined gas-liquid chromatography-chemical ionization mass spectrometry. The positions of original double bonds were deduced from the fragment ions produced by the cleavage of the carbon-carbon bond between two trimethylsilyl ethers. These fragment ions were recorded at m/e 187 and 259 in the case of 16:1(n-7), at m/e 187 and 287 in the case of 18:1(n-7), at m/e 215 and 259 in the case of 18:1(n-9), and at m/e 172 and 259 in the case of 18:2(n-6), respectively. The diastereoisomers of monounsaturated fatty acids can be discriminated by comparing the intensities of the fragment ions at m/e 253 and 285 in the case of 16:1 and at m/e 281 and 313 in the case of 18:1. The diastereosiomers of diunsaturated fatty acids may also be distinguished from each other by comparing the intensities of the fragment ions formed by the loss of trimethylsilyl function from the characteristic ions. Mono- and diunsaturated fatty acids in liver may be dominantly in cis- 18:1(n-1) and cis-cis-18:2(n-6) as determined by a mass chromatographic technique.     

The structure of the lipid A component of Sphaerotilus natans

The lipopolysaccharide of Sphaerotilus natans afforded a ladder-like pattern of bands in sodium deoxycholate-polyacrylamide gel electrophoresis, indicating the presence of a S-form lipopolysaccharide. The chemical analysis showed neutral sugars (rhamnose, glucose, l-glycero-d-manno-heptose), 3-deoxy-octulosonic acid (Kdo), amino compounds (glucosamine, glucosamine phosphate, ethanolamine and ethanolamine phosphate), and phosphorus. The lipid A fraction contained saturated and unsaturated capric, lauric, and myristic acids, and 3-hydroxy capric acid (3-OH-10:0). Its chemical structure was consisting of a glucosamine disaccharide, glycosidically substituted by a phosphomonoester, and substituted at C-4 by a pyrophosphodiester esterified with ethanolamine. The amino groups of both glucosamines are acylated by 3-hydroxy capric acids and these in turn are substituted by saturated and unsaturated capric, lauric, and myristic acids. Hydroxyl groups of the backbone disaccharide at C-3 and C-3 were also esterified by 3-hydroxy capric acid, those at C-4 and C-6 were unsubstituted. The latter provides the attachment site for Kdo.Abbreviations Kdo 3-deoxy-d-manno-octulosonic acid - 3-OH-10:0 3-hydroxy capric acid - DOC-PAGE deoxycholate-polyacrylamide gel electrophoresis - GC-MS gas chromatography/mass spectrometry - LD-MS laser desorption mass spectrometry - LPS lipopolysaccharide - PS polysaccharide     

A machine learning approach to explore the spectra intensity pattern of peptides using tandem mass spectrometry data

Background  

A better understanding of the mechanisms involved in gas-phase fragmentation of peptides is essential for the development of more reliable algorithms for high-throughput protein identification using mass spectrometry (MS). Current methodologies depend predominantly on the use of derived m/z values of fragment ions, and, the knowledge provided by the intensity information present in MS/MS spectra has not been fully exploited. Indeed spectrum intensity information is very rarely utilized in the algorithms currently in use for high-throughput protein identification.     

Beta-oxidation of medium chain (C8-C14) fatty acids studied in isolated liver cells

The beta-oxidation and esterification of medium-chain fatty acids were studied in hepatocytes from fasted, fed and fructose-refed rats. The beta-oxidation of lauric acid (12:0) was less inhibited by fructose refeeding and by (+)-decanoyl-carnitine than the oxidation of oleic acid was, suggesting a peroxisomal beta-oxidation of lauric acid. Little lauric acid was esterified in triacylglycerol fraction, except at high substrate concentrations or in the fructose-refed state. With [1-14C]myristic acid (14:0), [1-14C]lauric acid (12:0), [1-14C]octanoic acid (8:0) and [2-14C]adrenic acid (22:4(n - 6] as substrate for hepatocytes from carbohydrate-refed rats, a large fraction of the 14C-labelled esterified fatty acids consisted of newly synthesized palmitic acid (16:0), stearic acid (18:0) and oleic acid (18:1) while intact [1-14C]oleic acid substrate was esterified directly. With [9,10-3H]myristic acid as the substrate, small amounts of shortened 3H-labelled beta-oxidation intermediates were found. With [U-14C]palmitic acid, no shortened fatty acids were detected. It was concluded that when the mitochondrial fatty acid oxidation is down-regulated such as in the carbohydrate-refed state, medium-chain fatty acids can partly be retailored to long-chain fatty acids by peroxisomal beta-oxidation followed by synthesis of C16 and C16 fatty acids which can then stored as triacylglycerol.     

Rapid characterization of the fatty acyl composition of complex lipids by collision-induced dissociation time-of-flight mass spectrometry

Profiling of leaf extracts from mutants of Arabidopsis with defects in lipid desaturation demonstrates the utility of collision-induced dissociation time-of-flight mass spectrometry (CID-TOF MS) for screening biological samples for fatty acid compositional alterations. CID-TOF MS uses the collision cell of a quadrupole time-of-flight mass spectrometer to simultaneously fragment all of the ions produced by an ionization source. Electrospray ionization CID-TOF MS in the negative mode can be used to analyze fatty acyl anions derived from complex lipids as well as free fatty acids. Although acyl anion yield is shown to be a function of the lipid class and the position on the glycerol backbone, acyl compositional profiles can be determined, and the TOF detector provides resolution of nominally isobaric acyl species in the profiles. Good precision is obtained when data are acquired for approximately 1 min per sample.     

Structural characterization of the lipid A component of Sinorhizobium sp. NGR234 rough and smooth form lipopolysaccharide. Demonstration that the distal amide-linked acyloxyacyl residue containing the long chain fatty acid is conserved in rhizobium and Sinorhizobium sp

A broad-host-range endosymbiont, Sinorhizobium sp. NGR234 is a component of several legume-symbiont model systems; however, there is little structural information on the cell surface glycoconjugates. NGR234 cells in free-living culture produce a major rough lipopolysaccharide (LPS, lacking O-chain) and a minor smooth LPS (containing O-chain), and the structure of the lipid A components was investigated by chemical analyses, mass spectrometry, and NMR spectroscopy of the underivatized lipids A. The lipid A from rough LPS is heterogeneous and consists of six major bisphosphorylated species that differ in acylation. Pentaacyl species (52%) are acylated at positions 2, 3, 2', and 3', and tetraacyl species (46%) lack an acyl group at C-3 of the proximal glucosamine. In contrast to Rhizobium etli and Rhizobium leguminosarum, the NGR234 lipid A contains a bisphosphorylated beta-(1' --> 6)-glucosamine disaccharide, typical of enterobacterial lipid A. However, NGR234 lipid A retains the unusual acylation pattern of R. etli lipid A, including the presence of a distal, amide-linked acyloxyacyl residue containing a long chain fatty acid (LCFA) (e.g. 29-hydroxytriacontanoate) attached as the secondary fatty acid. As in R. etli, a 4-carbon fatty acid, beta-hydroxybutyrate, is esterified to (omega - 1) of the LCFA forming an acyloxyacyl residue at that location. The NGR234 lipid A lacks all other ester-linked acyloxyacyl residues and shows extensive heterogeneity of the amide-linked fatty acids. The N-acyl heterogeneity, including unsaturation, is localized mainly to the proximal glucosamine. The lipid A from smooth LPS contains unique triacyl species (20%) that lack ester-linked fatty acids but retain bisphosphorylation and the LCFA-acyloxyacyl moiety. The unusual structural features shared with R. etli/R. leguminosarum lipid A may be essential for symbiosis.     

Structural study on the free lipid A isolated from lipopolysaccharide of Porphyromonas gingivalis.

The chemical structure of lipid A isolated from Porphyromonas gingivalis lipopolysaccharide was elucidated by compositional analysis, mass spectrometry, and nuclear magnetic resonance spectroscopy. The hydrophilic backbone of free lipid A was found to consisted of beta(1,6)-linked D-glucosamine disaccharide 1-phosphate. (R)-3-Hydroxy-15-methylhexadecanoic acid and (R)-3-hydroxyhexadecanoic acid are attached at positions 2 and 3 of the reducing terminal residue, respectively, and positions 2' and 3' of the nonreducing terminal unit are acylated with (R)-3-O-(hexadecanoyl)-15-methylhexadecanoic acid and (R)-3-hydroxy-13-methyltetradecanoic acid, respectively. The hydroxyl group at position 4' is partially replaced by another phosphate group, and the hydroxyl groups at positions 4 and 6' are unsubstituted. Considerable heterogeneity in the fatty acid chain length and the degree of acylation and phosphorylation was detected by liquid secondary ion-mass spectrometry (LSI-MS). A significant pseudomolecular ion of lipid A at m/z 1,769.6 [M-H]- corresponding to a diphosphorylated GlcN backbone bearing five acyl groups described above was detected in the negative mode of LSI-MS. Predominant ions, however, were observed at m/z 1,434.9 [M-H]- and m/z 1,449.0 [M-H]-, each representing monophosphoryl lipid A lacking (R)-3-hydroxyhexadecanoic and (R)-3-hydroxy-13-methyltetradecanoic acids, respectively. The presence of mono- and diphosphorylated lipid A species was also confirmed by LSI-MS of de-O-acylated lipid A (m/z 955.3 and 1,035.2, respectively).     

Effect of hydroxylamine hydrochloride on lipopolysaccharide fatty acid composition in Shigella dysenteriae 1

Changes in the fatty acid composition of S. dysenteriae 1 lipid A after the treatment of lipopolysaccharide (LPS) with hydrosylamine hydrochloride (HH) and 4 degrees C, 37 degrees C and 56 degrees C were studied with the use of gas-liquid chromatographicmass-spectrometry. The treatment with HH led to a decrease in the toxicity of LPS, but produced no changes in the content of the main fatty acid components of lipid A (lauric, myristic, oxymyristic and palmitic acids). At the same time the total number of minor fatty acid derivatives decreased from 11 (in the original LPS) to 5 in LPS treated with HH at 56 degrees C.     

Lipid and sterol composition of the pollen of the west african oilpalm, Elaeis guineensis

The lipid classes, fatty acid methyl esters and the sterols of oilpalm pollen were analysed. The neutral lipid fraction consisted of triglycerides, esterified and free sterols and trace amounts of hydrocarbons. Monogalactosyl and digalactosyl diglycerides, phosphatidyl choline, phosphatidyl inositol and phosphatidyl ethanolamine represented the polar lipids. The major fatty acids were linoleic, palmitic and linolenic acids together with small to trace amounts of oleic, stearic, arachidic, myristic, lauric, palmitoleic and margaric acids. Unsaturated fatty acids predominated over saturated ones in the ratio of 3:2. The 4-desmethyl sterols were the major phytosterols in the free form but they constituted a lower proportion of the sterols in the esterified state. 28-Isofucosterol was isolated and characterized as the principal sterol.