Quantitative Determination of Tryptophan Metabolites (via Kynurenine) in Biologic Fluids

Abstract

Abstract A simple and rapid method for the quantitative determination of eight tryptophan (via kynurenine) metabolites is described. The following compounds can be determined even when present in the same sample of urine, blood or spinal fluid: kynurenine, 3-hydroxykynurenine, Nα-acetylkynurenine, anthranilic and 3-hydroxyanthranilic acids, kynurenic and xanthurenic acids, 8-methyl ether of the xanthurenic acid. The compounds are separated by means of two-dimensional chromatography. Spots of kynurenic acid, Nα-acetylkynurenine and xanthurenic acid 8-methyl ether are eluted with ethanol and the absorbancies are read in the ultraviolet. An acetic solution of p-dimethylaminobenzaldehyde serves as eluent and chromogenic reagent for the spots of kynurenine and anthranilic acid. Spots corresponding to 3-hydroxykynurenine, xanthurenic and 3-hydroxyanthranilic acids are eluted with water and determined by means of the color developed with a diazo reagent. Kynurenic and xanthurenic acids can also be determined conveniently by means of a spectrophotofluorometric procedure. The reproducibility of the results is satisfactory over a large range, and very good for amounts of 1 to 5 µg.