Quantitation and occurrence of hydroxy fatty acids in fats and oils

A relatively simple method is detailed for the routine quantitation and isolation of hydroxy fatty acids (HFA) in the glycerides of lipids. The lipid in cyclohexane is transmethylated in a two-phase, 3.5 min procedure, and the hydroxyl compounds in the methyl ester fraction are derivatized with pyruvic acid chloride 2,6-dinitrophenyl-hydrazone in the presence of triethylenediamine. The derivatives are fractionated on alumina, and the HFA fraction is evaluated spectrophotometrically. A large variety of animal, plant and marine lipids contain HFA in concentrations ranging from <10 to >1000 μmoles/g lipid. The derivatives lend themselves admirably to purification techniques. A procedure for regenerating the parent HFA from the derivative is described.