Sphingoid bases derivatives

Lavie, Y. and Liscovitch, M., 1990, Activation of phospholipase D by sphingoid bases in NG108-15 neural-derived cells,/. Biol. Chem. 265 3868-3872. 

Berdyshev, E. V., Gorshkova, I. A., Garcia, J. G., Natarajan, V., Hubbard, W. C. Quantitative analysis of sphingoid base-1-phosphates as bisacetylated derivatives by liquid chromatography-tandem mass spectrometry. Anal Biochem 339 (2005) 129-136. 

Figure 1.3 Simplified pathways and network of the common sphingolipid classes and other related lipids. The network and the pathways are derived from the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway databases. The pathways indicate the origins of sphingoid base core structures and their derivatives. Other sphingoid bases can be biosynthesized from other fatty acyl CoA by the replacement of palmitoyl CoA or some other amino acids replacing serine. The structures of individual lipid classes and their abbreviations used in the book are indicated in Figure 1.6.

A modest fragment ion at [M-l-Alk-429] corresponding to the loss of the long-chain sphingoid base as a terminal conjugated diene from the [M-i-Alk-(200-t-Alk)]+ ion, which can be used to determine the structure of the sphingoid base of the molecule and then derive the constituent of the FA amide. 

The sphingoid bases from plasma sphingomyelin, for example, were separated as A/-acetyl-0-TMS ether derivatives on a packed column (2 m x 3 mm) packed with 3% SE-30 , maintained isothermally at 230 C [724]. Saturated and unsaturated isomers are... 

Such procedures may be suitable for the analysis of samples containing a relatively simple range of long chain bases, but some natural lipid extracts are very complex. Alternative complementary techniques must then be employed to obtain the resolution needed. The most widely used approach is to stabilise the amino group by conversion to the dinitrophenyl (DNP) derivative, for separation into different classes by TLC procedures these compounds are yellow in colour so are easily seen on a TLC plate. DNP derivatives can later be degraded to aldehydes by periodate oxidation for GC analysis in this form [464,465]. The procedure for the preparation of A/-DNP derivatives of sphingoid bases is ... 

The sphingoid bases (up to 5 mg) are reacted with 1-fluoro-2,4-dinitrobenzene (5 mg) in methanol (1 mL), with addition of potassium borate buffer (pH 10.5 4 mL) drop-wise followed by heating at 60°C for 30 min. After cooling, the mixture is partitioned between chloroform, methanol and water in the ratio of 8 4 3 by volume, and the lower phase is collected and evaporated. The products are purified by chromatography on a short column of silicic acid (1 g), from which non-polar impurities are eluted first with hexane-diethyl ether (7 3 20 mL), while the required DNP derivatives are recovered with the same solvents in the ratio 1 1."... 

Aldehydes are more easily identified than are the parent compounds, since a wide range of standards is available from commercial sources or can be prepared synthetically from other lipids. As an example of the full application of this methodology, more than 30 different bases were detected in the sphingolipids of bovine kidney [469]. Mass spectrometry can be utilised as an aid to identification of aldehydes (see also Section B above), although some workers have preferred to reduce them to fatty alcohols and then to prepare acetate or TMS ether derivatives for this purpose [624]. In addition, all the methods for the location of double bonds in fatty acids, such as ozonolysis or hydroxylation with osmium tetroxide and preparation of TMS ethers for MS, have been utilised with aldehydes prepared from sphingoid bases [464,465]. 

One further type of derivative of sphingoid bases for GC-MS purposes is worthy of note, i.e. cyclic boronates [277]. Usually, it is necessary to protect the amine group, but a b/s-boronate derivative is formed from trihydroxy bases. Model compounds, prepared from standards, had excellent GC properties and also exhibited distinctive fragmentation properties on mass spectrometry. For example, they gave molecular ions in reasonable abundance. Unfortunately, they do not appear to have been applied to the analysis of natural samples. 

Chemical Structures of Sphingoid Long-Chain Bases and Their Glycosylated and Phosphoryl-ated Derivatives... 

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