Analysis of brain lipids by high performance thinlayer chromatography and densitometry

The authors have devised a high performance thin-layer chromatography (HPTLC) densitometry method to resolve the major lipid classes of brain tissue. They used DEAE-Sephadex column chromatography to separate the total lipid into neutral and acidic lipid fractions. The lipid fractions were then spotted on separate HPTLC plates and chromatographed in one dimension using two solvent systems. Quantitation was by in situ densitometry with absolute amounts of the lipid classes determined from co-chromatographed standards. An internal standard was also used to improve the precision. The individual lipid classes of rat whole brain, human brain gray and white matter, rat and bovine myelin, and bovine oligodendroglia were quantitated. Human brain phosphatidylethanolamine plasmalogen was also quantitated. Sensitivity was increased by using the cupric acetate charring reagent, which we found to be more sensitive than the conventional sulfuric acid-dichromate reagent. Total lipid (less than 400 μg) was quantitated from 5 mg of tissue wet weight. The limit of detection, on HPTLC, for the individual lipid classes was below 20 ng.