Development and application of chromatographic methods for glycerolipid analysis

There is no uniformly adopted definition for lipids and it is widely accepted that lipids are fatty acids, their derivatives, and substances related biosynthetically or functionally to these compounds [1]. Glycerolipids –lipids based on glycerol (acylglycerols, phospholipids, glycolipids, etc.) –in living organisms are complex mixtures of different types of molecules that contain stereoisomers and regioisomers. Although the technology of chromatography has advanced rapidly in recent years, there still exist many lipid molecules whose separations are difficult to achieve and physiological significance and biological activities are unknown. Accurate and concise methods for the analysis of lipids are therefore essential for many research studies. In the present “post-genomic era” the focus of investigation is moving away from gene sequences and interest is gradually returning to the gene products themselves (proteomics). It is well recognized that an understanding of pathophysiological changes that occur in cells and tissues requires complementary profiling of lipidderived metabolic products (lipidomics). This has led to the development of mass spectrometry (MS) -based lipidomics methodology [2,3]. MS, however, is unable to differentiate between enantiomers, and in many instances among regioisomers. This shortcoming is especially obvious in glycerolipids due to the prochiral nature of glycerol [4]. There were two unsolved problems in glycerolipid chromatography in the 1980s, one of which was enantiomer separation and the other regioisomer (reverse isomer) separation. We have solved important aspects of these problems by using chiral-phase HPLC [5] and reversed-phase HPLC [6], respectively. This review describes the chromatographic methods developed for both stereoisomeric and regioisomeric glycerolipids and their applications to lipid research. Readers are referred to earlier comprehensive reviews for background covering chiral analysis of glycerolipids [4, 7–14]. Focusing Review