Determination of tetrahydro-beta-carbolines in rat brain by gas chromatography-negative-ion chemical ionization mass spectrometry without interference from artifactual formation.

This paper describes a quantitative method for neuroactive alkaloids, 1-methyl-1,2,3,4-tetrahydro-beta-carboline (MTBC) and 1,2,3,4-tetrahydro-beta-carboline (TBC), in rat brain by gas chromatography-negative-ion chemical ionization mass spectrometry (GC-NICIMS). After addition of tetradeuterated MTBC and TBC (internal standards), the samples were subjected to deproteinization, reaction with fluorescamine, solvent extractions, trifluoroacetylation and GC-NICIMS analysis. In contrast to the other previous methods, the artifactual formation during analysis did not interfere with the determination of MTBC and TBC because their precursor tryptamine was removed as a fluorescamine derivative from the analytical system at the first step of pretreatment. MTBC and TBC were specifically and reliably determined in the range of pg-ng/sample. Application of the proposed method has revealed that the MTBC and TBC contents in rat brain significantly increase after intraperitoneal administration of MTBC and TBC, indicating their ability to easily cross the blood-brain barrier.