Tetrahydro-beta-carbolines in human urine and rat brain--no evidence of formation by alcohol drinking.

1-Methyl-1,2,3,4-tetrahydro-beta-carboline (1-MeTHBC) and 6-methoxy-1-methyl-1,2,3,4-tetrahydro-beta-carboline (6-M-1-MeTHBC) were identified and quantified in the urine of 131 healthy volunteers by gas chromatography/mass spectrometry (GC/MS) with a chemically-bonded glass-capillary column. 1-MeTHBC was present naturally in the human urine, whereas 6-M-1-MeTHBC was observed in only 20% of all subjects at a much lower level. No significant relationship was observed between these substances and alcohol consumption in the subjects. Various foods and alcoholic beverages were found to contain 1-MeTHBC but not 6-M-1-MeTHBC; thus, the urinary 1-MeTHBC detected could be of dietary origin. Salsolinol, on the other hand, was significantly elevated in the urine without increase of THBCs by long-term moderate drinking. 1-MeTHBC and 6-M-1-MeTHBC were also analysed in the brains of rats following inhalation of ethanol and acetaldehyde for four days. No evidence of formation of these compounds was observed in any regions of the brain.