Determination of free aspartic acid enantiomers in rat brain by capillary electrophoresis with laser-induced fluorescence detection

Quantification of aspartic acid enantiomers in rat brain by using a chiral capillary electrophoresis procedure is described. Amino acids were pre-column derivatized with naphthalene-2,3-dialdehyde. Enantiomeric separation was achieved by micellar electrokinetic chromatography in the presence of methanol and β-cyclodextrin as chiral selector. The chiral separation was coupled with laser-induced fluorescence detection. Contents of d- and l-aspartic acids in rats at different stages of growth (from 1 day before birth to 90 days after birth) were determined. d-Aspartic acid was detected in all the brain tissue samples tested, but at different levels. In the cerebrum of rats 1 day before birth, d-aspartic acid was found to be at the highest concentration of 81 nmol/g wet tissue. The level of d-aspartic acid in rat brain falls rapidly after birth, while the l-aspartic acid level increases with age.