title: Determination of m- and p-O-methylated products of L-3,4-dihydroxyphenylalanine using high-performance liquid chromatography and electrochemical detection.
abstract: In a study of in vitro and in vivo metabolism of L-3,4-dihydroxyphenylalanine (L-Dopa), two methods of high-performance liquid chromatography (HPLC) were used to separate the m- and p-O-methylated products. A reversed-phase column and an aqueous mobile phase by gradient elution were used; the elute was analyzed electrochemically with a single amperometric and dual coulometric electrode. The L-Dopa and its O-methylated products could be detected individually in the enzymatic methylation of rat liver homogenate and in patients with Parkinson's disease. Meta/para ratios of O-methylation are easily obtained by this method.
mesh_terms: D000818:Animals; D002394:Catechol O-Methyltransferase / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004563:Electrochemistry; D006801:Humans; D007536:Isomerism; D007980:Levodopa / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008745:Methylation; D010300:Parkinson Disease / Q000097:blood / Q000201:enzymology; D051381:Rats; D011919:Rats, Inbred Strains; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis
chemical_list: D014443:Tyrosine; C046013:4-methoxytyrosine; D007980:Levodopa; D002394:Catechol O-Methyltransferase; C008404:3-methoxytyrosine