The lipids of fish. 3. The acetone-insoluble fraction of an acetone extract of the flesh of the haddock

Abstract

Some lipids present in a crude acetone extract of haddock flesh are practically insoluble in acetone at O[degree] after purification. This material was fractionated by counter-current distr. between light petroleum and 85% (v/v) ethanol, certain products being further fractionated in absolute ethanol at -30[degree]. 2 fractions consisting mainly of lecithin and 2 of an unidentified lipid were obtained for detailed fatty-acid analyses. The lecithins differed from those isolated previously from the acetone-soluble fractions of the same total tissue extract, containing less C20 and C22, more C18 unsaturated acids and, more total saturated acids. The various groups of unsaturated acids were less highly unsaturated. The fatty acids of the unidentified lipid differed from those of the lecithins mainly in containing more stearic acid than palmitic acid and in respect to unsaturation. The unidentified lipid contained a higher ratio of fatty acids to glycerophosphate than the known glycerophosphatides. The presence in hydrolysates of a substance resembling glycerophos-phoric acid but giving a Ba salt insoluble in water, and of a non-amino base giving a water-insoluble phosphomolybdate, but different from choline, may afford clues to the composition of the unidentified lipid. Minor lipid constituents were identified. The material contained 25% non-lipid impurities, more than the acetone-soluble fraction of the same original extract. Acetone precipitation does not, therefore, always afford purer phospholipid prepns. This non-lipid could not be removed by countercurrent distr. and every fraction was heavily contaminated. Various amino compounds, acid-hydrolyzable P compounds and probably carbohydrates which were found in hydrolysates were possibly of non-lipid origin.