A novel tetrahydro-beta-carboline, chemically identified as 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid ethyl ester (ethyl 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylate) (MTCA-EE), has been found in alcoholic beverages ranging from an undetectable amount to 534 mu g/l. RP-HPLC with fluorescence detection and GC-MS were used for characterization. MTCA-EE occurred as two diastereoisomers 1S,3S and 1R,3S with an average ratio (SS/RS) of 2.21. The concentration of MTCA-EE (1S,3S plus 1R,3S) was 109.6-534 mu g/l in sherry wines, 75.2-140.7 mu g/l in sparkling wines, 3.4-161.65 mu g/l in red and white wines, 32.7-47.2 mu g/l in port wines, and 8.7-37.2 mu g/l in sake. MTCA-EE seemed to occur in some high alcohol beers at less than 10 mu g/l. Most distilled alcoholic beverages did not contain MTCA-EE although, exceptionally, one brandy reached 28.6 mu g/l. 1-Methyl-1,2,3,4-etrahydro-beta-carboline-3-carboxylic acid (MTCA) and L-tryptophan ethyl ester (L-TRP-EE) were two precursors leading to MTCA-EE. Alcoholic drinks containing MTCA-EE and MTCA could be an exogenous source of bioactive beta-carbolines found in vivo. MTCA-EE is a structural analogue (reduced pyrido ring) of beta-carboline-3-carboxylic acid ethyl ester (beta-CCE), a potent benzodiazepine receptor inverse agonist. (C) 1999 Elsevier Science Ltd. All rights reserved.