HPLC-MS MS IDENTIFICATION OF TRYPTOPHAN-DERIVED TETRAHYDRO-BETA-CARBOLINE DERIVATIVES IN FOOD/

Based on electrospray ionization-tandem mass spectrometry coupled to l iquid chromatography (HPLC-ESI-MS/MS) a method for separation and sele ctive detection of 1,2,3,4-tetrahydro-beta-carboline derivatives (THC) was developed. Retro-Diels Alder (RDA) fragmentation of the tetrahydr opyrido moiety resulted in the characteristic neutral loss of 73 amu f or tryptophan-derived THC-3-carboxylates. Accordingly, Pictet-Spengler condensation products of tryptamin exhibited product ions formed by l oss of 29 amu. However, THC-1-carboxylates as obtained by reaction of tryptamin with alpha-oxo acids also yielded product ions [M+H-73](+), apparently originating from the combination of RDA-cleavage plus subse quent decarboxylation. As result, one had to consider the possibility of false-positive identification of THC-3-carboxylates in presence of isomeric THC-1-carboxylates. In order to overcome these analytical pit falls, the unequivocal identification of trace amounts of THC-3-carbox ylates by HPLC-MS/MS required the chromatographic separation of isomer ic THC prior to selected reaction monitoring (SRM). Utilizing SRM, lim its of detection for various THC were established in the 10 ng mL(-1) range. Subsequent analysis of food samples like seasoning sauce and ye ast extract by HPLC-ESI-MS/MS revealed the presence of tryptamin-deriv ed 1,2,3,4-tetrahydro-beta-carboline-1-carboxylic acid, 1-methyl-tetra hydro-beta-carboline-1-carboxylic acid, 1-carboxyethyl-tetrahydro-beta -carboline and arboxyethyl-tetrahydro-beta-carboline-1-carboxylic acid beside established THC-3-carboxylates and -1,3-dicarboxylates.