Metabolism of plasmalogen: II. The determination of alkenyl ethers in the presence of free aldehydes

Abstract

SUMMARY A rapid and sensitive method for the analysis of alkenyl ethers (plasmalogens) in the presence of free aldehyde is proposed. The method is applicable over the range 0.02-0.2 pmoles of plasmalogen and is particularly useful for following the course of enzymatic or chemical reactions in mixtures containing both free aldehydes and plasmalogens in aqueous media. Plasmalogens, naturally occurring alkenyl ethers, react with a variety of acidic carbonyl reagents in a manner similar to free aldehydes. This reactivity may be due to rapid hydrolysis of the acid-labile alkenyl ether group, thus producing the free aldehyde. As a result, many of the standard colorimetric procedures are unsuitable for the specific determination of aldehydes in the presence of alkenyl ethers, and, similarly, there are few convenient procedures for determining alkenyl ethers in the presence of free aldehydes. The iodometric method of Norton (1) for the determination of alkenyl ethers is of considerable value, but this method is less sensitive than the reaction for aldehydes with fuchsin-sulfurous acid and is subject to interference from other iodine-reactive compounds (e.g. , reducing agents such as sulfhydryl derivatives), if present. More sensitive iodometric methods have been reported recently by Gottfried and Rapport (2) and Williams et al. (3), but these are still not directly applicable to systems that contain mercaptans. The latter are present in many enzymatic reaction mixtures. Although most interfering substances may be removed by washing a lipid extract with water, this process will considerably lengthen the time needed for analysis.