Tryptophan and kynurenine determination in untreated urine by reversed-phase high-pressure liquid chromatography

A fast and sensitive method for the analysis of tryptophan and some of its metabolites is discussed. A reversed-phase chromatographic system with water mobile phase can separate tryptophan, N-formalkynurenine, kynurenine and 3-hydroxykynurenine in less than 15 min at a flow-rate of 1 ml/min. The application of the method to the analysis of tryptophan and kynurenine in untreated urine of a patient loaded with tryptophan is described. The ease and speed of analysis makes the method very attractive for clinical purposes. Among other things, it was found that tryptophan in untreated urine degrades with time, even if the sample is frozen at −11°.