A fluorometric determination of N-methyl-4-phenylpyridinium ion, using high-performance liquid chromatography

A simple and sensitive assay procedure for the quantitation of N-methyl-4-phenylpyridinium ion (MPP+), a neurotoxin, was devised using its fluorescence and high-performance liquid chromatography (HPLC). The fluorescence intensity of MPP+ was several thousand times more than that of N-methyl-1,2,3,6-tetrahydropyridine (MPTP), a metabolic precursor of MPP+. This method was found to be sensitive enough to measure less than 10 pmol MPP+ without using HPLC and 10 fmol using HPLC. The oxidation of MPTP by monoamine oxidase in human brain synaptosomal mitochondria was examined by this assay method. This fluorometric-HPLC method should have broad application in the study of the neurotoxin MPP+.