Analysis of tryptophan catabolism in HBV patients by HPLC with programmed wavelength ultraviolet detection

Background: In order to understand the tryptophan catabolism in acute and chronic hepatitis B patients, we quantitatively analyzed plasma kynurenine and tryptophan simultaneously by high performance liquid chromatography with programmed wavelength ultraviolet detection. Methods: A new and specific high performance liquid chromatography method to simultaneously measure plasma kynurenine and tryptophan with programmed wavelength ultraviolet detection using 3-nitrotyrosine as internal standard was elaborated. Thirty patients were recruited (10 patients with acute HBV, 10 with chronic HBV and 10 healthy subjects). Results: The retention times of kynurenine and tryptophan were 2.9 min and 4.4 min, respectively. For kynurenine, the assay was linear from 0.442 mu mol/l to 18.3 mu mol/l. For tryptophan, the linearity was from 3.67 to 470 mu mol/l. The detection limits were 0.014 mu mol/l for Kyn and 0.122 mu mol/l for Trp, respectively. Its precision and recovery are satisfactory. In this study we found that the kynurenine per tryptophan ratio of acute group is higher than control group and chronic group. Conclusions: The method is simple, fast, accurate, and suitable for applicability to clinical measurement. (C) 2009 Elsevier B.V. All rights reserved.