Simple method for the analysis of glycerol enol ethers derived from plasmalogens in complex lipid mixtures and subsequent determination of the aldehydic components by gas chromatography-mass spectrometry

Gas chromatographic-electron impact mass spectrometric screening procedure for unknown hydroxyaldehydic lipid peroxidation products after pentafluorobenzyloxime derivatization

Aldehydic lipid peroxidation products can be detected after transformation to pentafluorobenzyloxime derivatives by GC-MS screening using characteristic ion traces. Thus the rather unstable unsaturated hydroxyaldehyde, 6-hydroxy-2,4-undecadienal, was identified as autoxidation product of linoleic acid. Its structure was unambiguously confirmed by comparison with an authentic sample. After Fe(2+)-ascorbate induced lipid peroxidation of oleic acid several 4-hydroxy-2-alkenals and 4-hydroxyalkanals were detected. These represent previously unknown secondary oxidation products of lipid peroxidation of oleic acid. Nevertheless oleic acid proved about 1000 times more stable against peroxidation than linoleic or higher unsaturated acids.

Epoxidation of plasmalogens: source for long-chain alpha-hydroxyaldehydes in subcellular fractions of bovine liver

1. Masked long-chain alpha-hydroxyaldehydes were trapped in all subcellular fractions of bovine liver by application of pentafluorbenzyloxime derivatization [van Kuijk, Thomas, Stephens and Dratz (1986) Biochem. Biophys. Res. Commun. 139, 144-149] and quantified via GLC/MS using characteristic ion traces. 2. The chain-length profile of long-chain 2-hydroxyalkanales clearly indicates their relationship to plasmalogens as precursor molecules. 3. The previously postulated existence of alpha-acyloxyplasmalogens as precursor molecules of masked long-chain alpha-hydroxyaldehydes in bovine tissue lipids [Lutz and Spiteller (1991) Liebigs Ann. Chem. 1991, 563-567] was excluded. 4. The constant oxidation rate of plasmalogens in all subcellular fractions provides conclusive evidence for a non-enzymic plasmalogen epoxidation process (probably via hydroperoxy radicals). 5. The high reactivity of alpha-hydroxyaldehydes sheds some doubt on the postulation that plasmalogens protect mammalian cells against oxidative stress as postulated previously [Morand, Zoeller and Raetz (1988) J. Biol. Chem. 263, 11590-11596; Morand, Zoeller and Raetz (1988) J. Biol. Chem. 263, 11597-11606].

Plasmalogen oxidation in human serum lipoproteins

The content of plasmalogens in lipoproteins--very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL)--in human serum was determined and compared with that after oxidation of the lipoproteins. Similarly, the content of alpha-hydroxyaldehydes produced from plasmalogens via their epoxids during lipidperoxidation (LPO) was studied. Incubation with Fe+ +/ascorbate results in a dramatic decrease in plasmalogens that correlates with an appropriate increase in alpha-hydroxyaldehydes. VLDL and LDL plasmalogens were oxidized to a greater extend (99% decrease) compared to HDL plasmalogens (35%). This finding is discussed with respect to atherogenesis and the recently postulated protective qualities of plasmalogens.

(S)-2-amino-1,3-propanediol-3-phosphate-carrying diradylglyceroglycolipids. Novel major membrane lipids of Clostridium innocuum

Two novel aminophosphoglycolipids (I, II) were isolated from Clostridium innocuum which constitute 51% (I) and 15% (II) of total polar membrane lipids. The structures, established by quantitative and methylation analyses, fast-atom-bombardment mass spectrometry, and one- and two-dimensional NMR spectroscopy, are (I) S-2-amino-1,3-propanediol-3-phospho-6-alpha-D-galactopyranosyl(1-2)alpha -D- glucopyranosyl(1-3)diradylglycerol and (II) an acylated derivative of (I) that carries an additional fatty acid ester on O6 of the glucosyl moiety. The stereochemical configuration of the 2-amino-1,3-propanediol 3-phosphate residue was elucidated by conversion to N-acetylserine 3-phosphate, with subsequent release and identification of L-serine by HPLC. In addition to diacylglycerol species, both aminophosphoglycolipids contain 15-32% 1-O-(alk-1-enyl)-2-O-acyl-glycerol species in which C14, C16, and C18 vinyl ether are combined predominantly with unsaturated C16 and C18 fatty acid ester. Hydrogenation of the vinyl ether was required to desorb the alkyl, acyl-substituted species in fast-atom-bombardment mass spectrometry. Hydrogenation made it further possible to release the alkyl glycerols by acid hydrolysis and to locate the ether bond at O1 of the glycerol moiety. In contrast to the glycerophosphoglycolipids of other Gram-positive bacteria, the aminophosphoglycolipids are metabolically not related to the lipoteichoic acid of C. innocuum and serve, therefore, exclusively as major membrane components. Their large abundance among membrane lipids suggests bilayer-forming physicochemical properties.