The separation and direct detection of ceramides and sphingoid bases by normal-phase high-performance liquid...

Sphingolipids are an important class of lipids due to their role as biologically active molecules and as intracellular second messengers. Sphingolipid metabolites are involved in a wide variety of important biological processes including signal transduction and growth regulation. Simple, quantitative analytical methods are needed to assay these complex lipids, in order to study their biological functions. The current methods used to quantify ceramides and long-chain sphingoid bases are primarily based on derivatization with uv or fluorescent tags and with radioactive-based enzymatic assays. A method was developed to separate ceramides and sphingoid bases by normal-phase high-performance liquid chromatography and detect them directly with evaporative light-scattering detection. Ceramides and the sphingoid bases phytosphingosine, dihydrosphingosine, sphingosine, and sphingosine 1-phosphate were resolved with a rapid and quantitative assay in the nanomole range. Yeast extracts grown to various time points were assayed for ceramide and sphingoid bases using a simple, isocratic HPLC system. Both ceramide and phytosphingosine, the primary sphingoid base present in yeast cell extracts, were detected in yeast cell extracts. Phytosphingosine was resolved as a sharp peak with the addition of triethylamine and formic acid modifiers to a chloroform/ethanol mobile phase. This method demonstrates the first direct assay of both ceramides and sphingoid bases.