A new quaternary ammonium cysteine analogue as a trapping reagent for reactive metabolites screening

The novel cysteine-cholamine (Cys-chol) trapping reagent was synthesized by coupling N-(tertbutoxycarbonyl)- S-trityl-L-cysteine with cholamine in the presence of HBTU (O-(benzotriazol-1-yl)- N,N,N',N'-tetramethyluronium hexafluorophosphate), and then deprotecting by trifluoroacetic acid. Cys-chol reagent enhanced the sensitivity of reactive metabolite screening 4 to 20 times without introducing additional sample preparation or derivatization steps. Retention of Cys-chol conjugates on reversed-phase column is higher than for respective GSH conjugates which helps in reduction of background interference. The use of Cys-chol trapping reagent can potentially improve sensitivity and specificity of routine reactive metabolite screening assay in drug discovery.