High-Performance Liquid Chromatographic Determination of L-3, 4-Dihydroxyphenylalanine (L-DOPA) and Its Metabolites in the Urine of Patients with Parkinson's Disease, Control Patients and Normal Subjects after Oral Administration of L-DOPA

A simple, accurate and reliable method for the simultaneous measurement of L-3, 4-dihydroxyphenylalanine (L-DOPA) and its metabolites, dopamine (DM), 3, 4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), excreted in the urine after oral administration of L-DOPA was developed. The method consists of the addition of internal standards to urine samples, high-performance liquid chromatography for 50 min on a column of sulfonated polystyrene, detection of DOPAC, p-hydroxyphenylacetic acid (an internal standard) and HVA by UV absorbance measurements and detection of DOPA, 3, 4-dihydroxybenzylamine (an internal standard) and DM by measurements of fluorescence generated by the reaction with o-phthaldialdehyde. L-DOPA was administered to patients with Parkinson's disease, control patients and normal subjects, and urine samples were collected 0, 2, 4 and 6 hr later. DOPA and metabolites were measured by this method. The excretion patterns in control patients and normal subjects were quite similar to each other and the maximum excretions of these compounds were observed mostly in 0-2 hr urine, whereas in patients with Parkinson's disease the patterns varied and the excretions of all the compounds were delayed in 11 out of 13 patients.