Separation and composition of the phospholipids of ox heart

Abstract

Phospholipids equivalent to about 560 mg of phosphorus/kg were extracted from ox heart with chloroform-methanol mixtures and the washed lipid was fractionated on Mallinkrodt silicic acid columns. The phospholipids, in mixtures which contained about 45% of plasmalogens but no inositides, were recovered quantitatively with good separation into cardiolipin, kephalin, lysokephaline, cholinephosphatides and sphingomyelin. The kephalin and choline phosphatide fractions contained about 45 and 55% respectively of plasmalogens which were not separated to any useful extent from the corresponding ester phosphatide. In the presence of the neutral fat fraction, kephalin plasmalogen is liable to decompose on silicic acid columns, with formation of free aldehyde and lysokephalin. Apart from this decomposition, lysophosphatides were not detected. On treatment of acetone-defatted heart with methanol, 95% of the choline phosphatides, together with cardiolipin and inositide, but only 70% of the kephalin was extracted. A method for partition chromatography of phospholipids with organic solvents and secondary cellulose acetate as support is described. With cyclohexane-methanol systems, fractionation of lecithin-choline plasmalogen mixtures containing 50% of plasmalogen yielded 20% of the total lipid in fractions containing 75-85% of plasmalogen. Evidence that the separation is influenced by the nature of the fatty acids was obtained. Data on the composition of cardiolipin preparations and on the mode of hydrolysis of cardiolipin in acid and alkaline conditions are recorded. Glycerophosphoinositide equivalent to about 30% of the inositide present was obtained as crystals from inositide-rich fractions. This inositide contained saturated and unsaturated acids in equimolar proportions: 46% of the fatty acids was present as stearic acid and 15% as C20-22 highly unsaturated acids.