The lipids of fish. 2. The acetone-soluble lipids of the flesh of the haddock

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Abstract
An acetone extract of haddock flesh was separated into 3 fractions comprising (A) acetone-soluble non-phosphatidic lipids plus some lecithin, (B[image]) mainly lecithin soluble in acetone in the absence of added electrolytes, and (C) acetone-insoluble lipids. The lecithin in (A) was partly genuinely soluble in acetone and partly soluble in the presence of other lipids. The significance of acetone-insolubility in the prepn. of phospholipins is discussed. Fractions A and B[image] were studied by countercurrent distr. between light petroleum and 85[degree]/o (v/v) ethanol, followed by pooling of certain fractions on the basis of similar chemical compositions and analysis of the pooled material for various lipid constituents. Fraction A consisted of about 32[degree]/o lecithin, 18[degree]/o free cholesterol, 18[degree]/o free fatty acids, 10[degree]/o cholesterol esters, 8[degree]/o waxes, 7[degree]/o triglycerides, 2[degree]/o hydrocarbons, etc. and 5[degree]/o non-lipid matter. The free fatty acids were a genuine constituent of haddock flesh and not a post-mortem artifact. Fraction B[image] consisted of about 61[degree]/o lecithin, 6[degree]/o waxes, 1[degree]/o hydrocarbons, etc., and 32[degree]/o unidentified material, including probably 4[degree]/o plasmalogens. Detailed fatty acid analyses of the lecithins in fractions A and B[image] revealed exceptionally high proportions of highly unsaturated C20 and C22 acids, with a curious total lack of hexadecenoic acid and unusually small amts. of C18 unsaturated acids. The free fatty acids were in some respects intermediate in type between those of the lecithins and those of haddock depot fat. The significance of these fatty acid compositions cannot be assessed until all the lipid fractions of the tissue have been similarly examined. Certain fractions were quite rich in uncharacterized N, and early observations of the presence of firmly bound N in the fatty acids liberated from phospholipins were confirmed.
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