Determination of urinary indolic metabolites

A rapid mass spectral assay for tryptophol, 5-hydroxytryptophol, and 3-indoleacetic acid, employing stable-isotope labeled internal standards, is described. The compounds were extracted from urine or buffer with ethyl acetate and quantitatively measured by chemical-ionization mass spectrometry. The calibration curves were linear over a range of 0.06--2.8 microgram/ml. The technique was applied to the analysis of urine from patients with carcinoid tumors. In addition, the first synthesis of 5-methoxy-3-indoleacrylic acid is reported.