No abstract

No abstract

of phosphorus were removed at intervals, and the lysolecithin formed was separated from the unreacted lecithin on a preparative silica-gel thin-layer chromatoplate, using chloroform-methanol-water (65:25:4, by vol) as the developing solvent. The fatty acids of the lysolecithin were transmethylated according to the procedure of Bowyer et al.,2) and the esters were analyzed by gas-liquid chromatography using a hydrogen-flame ionization detector. The positional distribution of fatty acids in the lecithin was determined by employing snake venom, which is known to release those fatty suits showed that the fatty acid composition of the lecithin was 85.1% saturated acids (a large amount of palmitic acid and a small amount of stearic position. The total amount of the saturated acids of the lecithin was 58.0%, while that of the unsaturated acids was 42.0%.Each experiment was run more than three times. ent, the fatty acid composition of the lysolecithin isolated from a reaction mixture is used in estimatester linkages. The calculation is based on the above analytical results; i.e., the presence of 85.1% and 3.7% saturated acids in the isolated lysolecithin indicates a 100% and a 0% cleavage, portion of saturated acids and the 22.8% portion of unsaturated acids in the lysolecithin isolated from a reaction mixture of the lecithin and tbutoxide, for example, would indicate a 90.4% early stages of alcoholysis but both ester linkages in a random manner in later stages, whereas i-propoxide and t-butoxide give a highly preferential cleavage of the ester (90% throughout the reaction time studied (5hr)) and laurylamine (79% even after 20hr of reaction).The present results are not in accord with the latest proposal made by Hancock4) concerning the alkaline hydrolysis of the ester, according to should result, provided that an ionic effect of the phosphorylchloline residue remains the same on both ester bonds.A solvent effect, i.e., the unbe a major controlling factor in the reaction, since a random cleavage occurred in the case of nalkoxides.Furthermore, no such effect has been made apparent in the case of the hydrolysis of monoglycerides in an organic solvent.5) Therefore, it appears that certain conformations of the lecithin molecule are involved in directing the course of the reaction. The present observations suggest, therefore, that the lecithin molecule in the alcohols employed exists chiefly in the trans-trans and trans-gauche 1)

The optimum conditions for cleavage of the fatty acid ester linkages in the lecithin molecule were found to be 20 min. at 10°C with the use of two moles of lithium aluminum hydride per mole of lecithin. The product formed under these conditions was identified to be l-α-glycerylphosphorylcholine when ovolecithin which was shown to be l-α-lecithin was used. Discussion has been presented as to two mechanisms possibly participating in the cleavage of glycerylphosphorylcholine, one involving a complex formation with the phosphoryl group and the other with the cationic nitrogen atom of the choline base.