A Simple Method for Measuring Phosphatidylcholine as Its Hydrophobic Complex with Tetrathiocyanatocobaltae

Abstract

A sensitive colorimetric method for quantitative determination of phosphatidylcholine is described. The procedure is very simple, not involving lipid extraction or acid digestion, and can be used for direct estimation of phosphatidylcholine in blood plasma. The method depends on the formation of a stable hydrophobic complex of phosphatidylcholine with tetrathiocyanatocobaltate. Similar complexes are formed by other species of diacylglycero-phosphoryl esters, but the absorbance coeffcients of these complexes are only 10 to 20% of that of the phosphatidylcholine complex. Phospholipids without unsaturated fatty acids, such as dipalmitoyl phosphatidylcholine, do not form hydrophobic complexes. Lysophosphatidyl-choline and sphingolipids also do not form similar complexes.