HPLC and HPLC-MS Analysis of Urinary Nε-Monomethyl-Lysine

Administration of 14 C-labelled L-deprenyl to rats results in the urinary elimination of a 14 C-labelled compound. The 9-fluorenylmethoxycarbonyl chloride-reacted urine sample is fractionated by high-performance liquid chromatography (HPLC) on an octadecyl silica stationary phase. N e -Monomethyl-lysine is identified in the fraction containing the majority of the radioactivity. Structural elucidation is carried out using HPLC-mass spectrometry in atmospheric pressure chemical ionization mode. Identification of the 14 C-labelled fragment in N e -monomethyl-lysine is an experimental proof that an N-methylated amino acid is generated by transmethylation from a well-known drug. This type of transmethylation may have basic importance in the positive side effects of certain drugs.