Screening for defects in tryptophan metabolism.

We introduced a two-step procedure for the detection of defects in metabolism of tryptophan: (1) HPTLC (described previously) is suitable when starting the investigation, (2) two HPLC methods with isocratic elution and spectrophotometric detection are used at the next step, when pathological findings are to be confirmed and the individual metabolites quantified. The first method enables the assessment of tryptophan, 5-hydroxyindolylacetic acid, indolylacetic acid, indolylacryloylglycine, indolylacrylic acid and its possible precursors, namely indolyllactic and indolylpropionic acids. The second procedure is intended for the monitoring of anthranilic, 3-hydroxyanthranilic, kynurenic and xanthurenic acids, kynurenine, 3-hydroxykynurenine and indoxyl-sulfate.