Simultaneous determination of tryptophan and kynurenine in serum by HPLC with UV and fluorescence detection.

Tryptophan metabolism is disturbed in mental depression, and the induction of indoleamine 2,3-dioxygenase increases kynurenine production. In order to determine this disturbance in patients with chronic hepatitis C and receiving interferon-based immunotherapy, a new and specific HPLC protocol was elaborated. For tryptophan, the assay was linear from 6.25 to 100 µmol L⁻¹, and the limits of detection (LOD) and quantitation (LOQ) for the method were 0.7 and 8.0 µmol L⁻¹. For kynurenine, the linearity of calibration was from 0.0625 to 6.25 µmol L⁻¹, with LOD and LOQ of 2 and 3 nmol L⁻¹. Reproducibility and repeatability were satisfactory. The method allowed study of human blood serum. Copyright © 2004 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]