LC–MS/MS-Based Quantification of Kynurenine Metabolites, Tryptophan, Monoamines and Neopterin in Plasma, Cerebrospinal Fluid and Brain

Aim: The kynurenine (KYN) pathway is implicated in diseases such as cancer, psychiatric, neurodegenerative and autoimmune disorders. Measurement of KYN metabolite levels will help elucidating the involvement of the KYN pathway in the disease pathology and inform drug development. Methodology: Samples of plasma, cerebrospinal fluid or brain tissue were spiked with deuterated internal standards, processed and analyzed by LC–MS/MS; analytes were chromatographically separated by gradient elution on a C18 reversed phase analytical column without derivatization. Conclusion: We established an LC–MS/MS method to measure 11 molecules, namely tryptophan, KYN, 3-OH-KYN, 3-OH-anthranilic acid, quinolinic acid, picolinic acid, kynurenic acid, xanthurenic acid, serotonin, dopamine and neopterin within 5.5 min, with sufficient sensitivity to quantify these molecules in small sample volumes of plasma, cerebrospinal fluid and brain tissue.