Improved identification of monomethyl paraffin chain branching (close to the methyl end) of long-chain compounds by gas chromatography and mass spectrometry

Occurrence of ceramide digalactoside as the main glycosphingolipid in the marine sponge Halichondria japonica

The main glycosphingolipid of the sponge Halichondria japonica was isolated and its structure was determined to be ceramide digalactoside, Gal alpha 1----4Gal beta 1----1Cer, using FAB/MS, IR, 1H-NMR and chemical methods such as permethylation analysis and degradation techniques. The ceramide moiety was composed mainly of 4-hydroxy-iso-octadecasphinganine and 2-hydroxy-docosanoic acid. Interestingly, the branched long-chain bases were comprised of 70% total long-chain bases and 17.5% 4-hydroxy-anteiso-nonadecasphinganine. Ceramide monohexoside, consisting of galactosyl ceramide (81%) and glucosyl ceramide (19%), was also isolated as a minor component. The composition of the ceramide moiety was nearly the same as that of ceramide digalactoside.

Identification of meibomian gland lipids by gas chromatography-mass spectrometry: application to the meibomian lipids of the mouse

Methods are described for the structural determination of the constituent alcohols, steroids and fatty acids from meibomian gland esters. The compounds, obtained from hydrolysed extracts, were separated and quantified as trimethylsilyl and methyl ester-trimethylsilyl derivatives by fused-silica capillary column gas chromatography. Structural information relating to the position of chain branching and the position of double bonds in the aliphatic chains of the acids and alcohols was obtained from the mass spectra of a number of other derivatives. Thus pyrrolidide-trimethylsilyl and picolinyl ester-trimethylsilyl derivatives provided information on both branching and unsaturation. The double-bond position in unsaturated fatty acids was also examined by use of trimethylsilyl derivatives of the derived glycols. The positions of chain branching of the alcohols were determined by the spectra of their acetate and nicotinate derivatives and by their gas-liquid chromatographic retention times. In meibomian gland lipids from the mouse, cholesterol was the major constituent; alcohols from the n-, iso-, anteiso- and unsaturated series were present with iso-C26 and anteiso-C27 being the most abundant. Mono-unsaturated fatty acids belonged mainly to the omega 9 series and saturated acids belonged to the iso-, anteiso- and n-series. Several 1,2-diols were also identified. The most abundant of these had iso-C16 and iso-C20 chains. GC-MS studies on the intact wax esters showed them to be composed of the branched-chain alcohols and both branched-chain and unsaturated acids.

Characterization of cerebroside (monoglycosylceramide) from the sea anemone, Metridium senile. Identification of the major long-chain base as an unusual dienic base with a methyl branch at a double bond

1. Cerebroside of the sea anemone, Metridium senile, has been isolated (0.6 mg/g dry tissue weight) and structurally characterized. 2. The structure was shown by mass spectrometry, NMR spectroscopy and degradative studies as beta-glucopyranosylceramide. The major fatty acids were 16 : 0 and 20 : 0 D-2-hydroxy fatty acids. The major base was a novel base, D-erythro-1,3-dihydroxy-2-amino-9-methyl-trans-4, trans-8-octadecadiene. 3. Some unusual fatty acids of marine origin are suggested to originate in this long-chain base by metabolic conversion. 4. The implication of the methyl branch position of the base on our current view of sphingolipid function in the plasma membrane is discussed.

Fatty acid and aldehyde composition of major phospholipids in salt gland of marine birds and spiny dogfish

The lipophilic components of choline phosphoglycerides and ethanolamine phosphoglycerides obtained from the salt gland of herring gull and eider duck and from the rectal gland of spiny dogfish were investigated by means of thin-layer chromatography, gas chromatography, and gas chromatography-mass spectrometry. All phospholipids analyzed were shown to contain small amounts of plasmalogens, and mainly C16, C18, and C18:1 aldehyde was detected. The fatty acids were composed of saturated, unsaturated, straight chain, and branched chain types, ranging between 14-22 carbon atoms. The lipophilic composition of the rectal gland phospholipids showed a higher degree of unsaturation and the presence of more branched chain fatty acids than that of the birds, possibly related to body temperature.