The lipids of fish. 5. The lipids remaining in the flesh of the haddock after extraction by acetone and ethanol-ether

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Abstract
Haddock flesh, previously exhaustively extracted with acetone and ethanol-ether (3:1 v/v) at room temperature, was extracted successively with boiling ethanol-benzene (2:1 v/v), boiling chloroform-methanol (1:1 v/v) and pyridine at 100[degree]. The 3 extracts proved to consist predominantly of non-lipid material, most of which was removed by partition between chloroform and water. The purified extracts were separated into acetone-soluble and acetone-insoluble fractions, and the former further subdivided into neutral and acidic lipids. Counter-current distribution between light petroleum and 85% (v/v) aqueous ethanol was also employed in fractionating the ethanol-benzene and chloroform-methanol extracts. Acidic, neutral and acetone-insoluble fractions were all complicated mixtures, and the acidic lipids were neither free fatty acids nor simple phos-phatidic acids. Lipid portions of all these extracts differ appreciably from the previous extracts, in particular in the high content of unsaponifiable matter, for the present assigned to waxes and hydrocarbons. The total lipids of haddock flesh, amounted to 0.55% of the fresh tissue. Lecithins are outstandingly the major component (43%) and triglycerides (2.4%) quantitatively among the least important. The solvents used showed a varying efficiency for the different lipids. The lipids most resistant to extraction are rich in non-sterol unsaponifiable matter, as are the traces of lipids associated with the water-soluble impurities removed during the purification processes.