Determination of dopamine and dopamine-derived (R)-/(S)-salsolinol and norsalsolinol in various human brain areas using solid-phase extraction and gas chromatography/mass spectrometry

Using a solid-phase extraction procedure and a gas chromatographic-mass spe ctrometric (GC/MS) method the levels of dopamine and the levels of dopamine -derived salsolinol (SAL) and norsalsolinol (NorSAL) were determined in hum an brain areas involved in the etiology of alcoholism, parkinsonism and oth er diseases. The possibility that biosynthesis of salsolinol occurs through a stereospecific enzymatic reaction was considered. Using a two-step deriv atization with N-methyl-N-trimethylsilyltrifluoracetamido (MSTFA) and the c hiral reagent (R)-(-)-2-phenylbutyryl chloride, baseline separated peaks of (R)- and (S)-SAL were obtained. Both enantiomers were found in human brain samples with no correlations between levels of salsolinol and dopamine. Th ese findings do not support the hypothesis that only an enantio-selective s ynthesis of (R)-SAL by a putative salsolinol synthase is responsible for th e in vivo formation. In our opinion, non-enzymatic formation of salsolinol via the Pictet-Spengler reaction reveals both salsolinol enantiomers and an additional enzymatic synthesis of only (R)-SAL explains the enantiomer rat io (R)-/(S)-SAL of approximately 2. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.