Polyamide thin-layer chromatographic separation of DOPA metabolites and related compounds.

The use of L-DOPA* in therapy of Parkinsonisml has stimulated interest in the metabolism of this compound in normal’ and pathologic3 states. Goodall and Alton’ separated 35 DOPA metabolites from the urine of healthy subjects by GLC. Seventeen of these metabolites, including 11 acidic compounds, were unidentified. Recently, 3-hydroxyphenylacetic acid, 3-methoxy-4-hydroxyphenyllactic acid, and 4-hydroxyphenyllactic acid were identified in the urine of patients receiving large oral doses of L-DOPA4. More recently, 3-hydroxyphenylacetic acid has been shown to be produced from DOPA by the intestinal microflora’. The substituted phenyllactic acids are products of a transamination pathway of metabolism enhanced by large doses of L-DOPA 406. This pathway, a major route for the metabolism of L3-0-methylDOPA’,, as well as other possible pathways, may have significance in Parkinson pitients. The production of 3-methoxy-4-hydroxyphenyllactic acid by such patients receiving L-DOPA confirms earlier observations of this metabolite in the urine of patients with DOPA-secreting tumorsE’ll. The present study was prompted by the possibility that important DOPA metabolites may not yet have been identified and by the lack of a simple, readily-available method for the separation of potential DOPA metabolites differing only slightly in structure. The advantages of polyamide thin layers for the separation of phenoliccompounds has been recognized I’. This report includes TLC data obtained with authentic samples of compounds not previously available for study.