Lyso platelet activating factor (LysoPAF) and its enantiomer. Total synthesis and carbon-13 NMR spectroscopy

Safety assessment of alkyl glyceryl ethers as used in cosmetics

Alkyl glyceryl ethers function mostly as skin-conditioning agents in cosmetic products applied to the skin and hair. The Cosmetic Ingredient Review expert panel reviewed the available animal toxicity and clinical data, including the low dermal absorption, and concluded that the alkyl glyceryl ethers are safe in the present practices of use and concentration described in this safety assessment.

Synthesis and biological properties of the fluorescent ether lipid precursor 1-O-[9'-(1''-pyrenyl)]nonyl-sn-glycerol

The synthesis of an omega-pyrene-labeled 1-O-alkyl-sn-glycerol was performed using a chirospecific method starting from R-(-)-2,3-O-isopropylidene-sn-glycerol. The product, 1-O-[9'-(1''-pyrenyl)]nonyl-sn-glycerol (pAG), is a fluorescent ether lipid that has a pyrene moiety covalently attached at the alkyl chain terminus. pAG was taken into CHO-K1 cells and a plasmalogen-deficient variant of CHO-K1, NRel-4. This variant is defective in dihydroxyacetonephosphate acyltransferase, which catalyzes the first step in plasmenylethanolamine (PlsEtn) biosynthesis. pAG was incorporated primarily into ethanolamine and choline phospholipids as well as a neutral lipid fraction tentatively identified as alkyldiacylglycerol. NRel-4 accumulated more fluorescence in the phospholipid fraction than CHO-K1, specifically in the ethanolamine phospholipids. Analysis of the fluorescent lipids showed that 93% of the pAG was incorporated into glycerolipids with the ether bond intact. Although the addition of 20 microM 1-O-hexadecyl-sn-glycerol to the medium fully restored PlsEtn biosynthesis in NRel-4 cells, pAG only partially restored PlsEtn synthesis. Incubation of cells with pAG followed by irradiation with long-wavelength (>300 nm) ultraviolet light resulted in cytotoxicity. NRel-4 cells displayed an increased sensitivity to this treatment compared with CHO-K1 cells. This photodynamic cytotoxicity approach could be used to select for mutants that are defective in downstream steps in ether lipid biosynthesis.

Alk-1-enylacyl, alkylacyl, and diacyl subclasses of native ethanolamine and choline glycerophospholipids can be quantified directly by phosphorus-31 NMR in solution

We show that phosphorus-31 nuclear magnetic resonance spectroscopy can be used to distinguish and to quantify the alk-1-enylacyl, alkylacyl, and diacyl glycerophosphoethanolamine (GPE) subclasses, and the respective glycerophosphocholine (GPC) subclasses, in their native form without prior degradation or derivatization, provided the phospholipids are observed in the nonaggregated state. Monomeric phospholipid distribution is ascertained by recording the spectra, after removal of metal ions, on CDCl3/CD3OD/D2O (50:50:15, by vol) solutions. The utility of this approach is exemplified for the ethanolamine glycerophospholipids (EPL) from bovine brain and the choline glycerophospholipids (CPL) from bovine heart. Sharp and well-resolved resonances are obtained for alkylacylGPE (+0.395 ppm; re 1% H3PO4), alkenylacylGPE (+0.353 ppm), and diacylGPE (+0.315 ppm), and for alkylacylGPC (-0.383 ppm), alkenyl-acylGPC (-0.436 ppm) and diacylGPC (-0.451 ppm). Integrated peak areas are shown to closely correlate with dose. Accurate quantitation of EPL and CPL subclasses at submicromolar levels can further be facilitated by use of synthetic dialkylGPE (+0.602 ppm) and dialkylGPC (-0.196 ppm) as internal standards. The method is simple, rapid, sensitive and reproducible, and permits the complete resolution and direct quantitation of all ethanolamine and choline glycerophospholipid subclasses quite independent of fatty chain length and degree of unsaturation.

On the synthesis of platelet-activating factor via acetylation of 1-alkyl-sn-glycero-3-phosphocholine. Formation of structural isomer of PAF in the presence of bases

It has been shown that platelet-activating factor (PAF) specimens prepared via acetylation of 1-alkyl-sn-glycero-3-phosphocholine (lyso-PF) with acetic anhydride are heterogeneous. The contaminated compound was isolated and identified to be the structural isomer of PAF, 1-alkyl-3-acetyl-sn-glycero-2-phosphocholine (iso-PAF). It appeared, that iso-PAF is formed when performing the reaction in the presence of organic bases,but not under acid catalysis. The mechanism of iso-PAF formation is discussed.

Alkyl glycerol monoethers in the marine sponge Desmapsamma anchorata

1-O-Hexadecylglycerol (chimyl alcohol), 1-O-heptadecylglycerol and 1-O-octadecylglycerol (batyl alcohol) have been identified as the major native constituents of a mixture of free alkyl glycerol ethers isolated from the contained water and the methanolic extract of the sponge Desmapsamma anchorata. Minor components were the free C14, C15, C19, C20 and C21 alkyl glycerol monoethers. The alkyl glycerol monoethers were analyzed and identified by gas chromatography/mass spectrometry of their isopropylidene derivatives. This is the first report on the occurrence of free C15, C19, C20 and C21 alkyl glycerol monoethers in a sponge.

Synthesis of 1-palmitoyl-2-hexadecyl-sn-glycero-3-phosphocholine (PHPC)

A general method for the chirospecific synthesis of 1-acyl-2-alkyl-sn-glycero-3-phosphocholines is described. 1-Palmitoyl-2-hexadecyl-sn-glycero-3-phosphocholine (PHPC) was synthesized in 18% overall yield in ten steps via five new synthetic intermediates, and 1-acetyl-2-hexadecyl-sn-glycero-3- phosphocholine (AHPC) was also synthesized. 1-Acyl-2-alkyl-sn-glycero-3-phosphocholines, which have not been found to exist in nature, are ether lipid analogs of 1,2-diacyl-sn-glycero-3-phosphocholines, which are important components of cell membranes. Biophysical studies of hydrated bilayers of PHPC will be of interest in probing the critical importance of the central region of these amphiphilic molecules to the molecular assemblies that are formed.