The structure of plasmalogens: VII. Analysis of mammalian liver lipids and the interference of vitamin A in the analysis

Low values of the molar ratio of α,Β-unsaturated ether to aldehydogenic lipid found with lipid extracts of mouse and rat liver are shown to result solely from the presence in these extracts of vitamin A rather than of long-chain aldehydes or mixed acetals. Vitamin A interferes in the spectrophotometric determination of specific iodination of α,Β-unsaturated ethers because it absorbs some light at 355 mμ. The correction is made simply by using an appropriate sample blank. Vitamin A interferes much more seriously with the estimation of aldehydogenic lipids as p-nitrophenylhydrazones because of its transformation under the reaction conditions to anhydro vitamin A. The correction for this interference may be made by independent estimation of the vitamin A content (Carr-Price reaction), determining a standard curve for vitamin A subjected to the p-nitrophenylhydrazone procedure, and subtracting the appropriate value.The vitamin A content of liver is dependent on the species of animal as well as on diet. In the animals studied, the average level of interference of vitamin A in estimations of liver plasmalogen was 75% for the mouse, 50% for the rat, 8% for the rabbit, and negligible for guinea pig.