Influence of alkyl ether chain length of acetyl glyceryl ether phosphorylcholine and its ethanolamine analog on biological activity toward rabbit platelets

The preparation of the potent new lipid chemical mediator, 1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (AGEPC), through a facile semisynthetic procedure utilizing the vinyl ether-containing lecithins (plasmalogens) of bovine heart muscle as the starting material results in a derivative with mixed chain alkyl residues. In order to focus more closely on the importance of the various components of AGEPC relative to its biological activity, it was of importance to develop a method for isolation of molecules rich in a specific chain length of the alkyl residue. In the current study it was found that a simple thin-layer chromatographic technique, using a solvent system of methanol water (2:1, v v), afforded an excellent separation of semisynthetic AGEPC into two species, one containing over 95 mol% 16:0 and the other 95 mol% 18:0 alkyl chain species. The same procedure allowed a comparable separation of the species of 1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphorylethanolamine (AGEPE) prepared from AGEPC by phospholipase D action. On the basis of their effectiveness in releasing serotonin from washed rabbit platelets, the 16:0-rich derivatives of AGEPC and AGEPE exhibited significantly higher specific activities, from three to six-fold, on a molar basis, respectively, than the corresponding 18:0-rich derivatives. These findings are discussed in relation to the importance of the chain length of the alkyl ether group in expression of the biological activity of AGEPC.