title: Method for the determination of gamma-L-glutamyl-L-dihydroxyphenylalanine and its major metabolites L-dihydroxyphenylalanine, dopamine and 3,4-dihydroxyphenylacetic acid by high-performance liquid chromatography with electrochemical detection.
abstract: A high-performance liquid chromatographic method for the analysis of gamma-L-glutamyl-L-dihydroxyphenylalanine (gludopa) and its major metabolites L-dihydroxyphenylalanine (L-DOPA), dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) is described. High sensitivity is achieved with a multi-cell coulometric detector utilising the specific electrochemical properties of gludopa (limit of detection 10 pg on-column). The retention time of gludopa was both pH-dependent and sensitive to negatively charged ion-pairing agents. An alumina-based solid-phase sample preparation technique with dihydroxybenzylamine as internal standard is described for plasma and urine (limit of detection 40 pg/ml) and an ultrafiltration technique is described for tissues (limit of detection 1-10 ng/g). After treatment with 50 mg/kg gludopa, in excess of twenty separate catecholic metabolic peaks can be detected in rat urine, whereas in humans after 9 mg/kg the only catechols detected were L-DOPA, dopamine and DOPAC.
authors.affiliation: Imperial Cancer Research Fund Medical Oncology Unit, Western General Hospital, Edinburgh, Scotland, U.K.
authors.forename: J
authors.initials: J
authors.lastname: Cummings
authors.forename: L M
authors.initials: LM
authors.lastname: Matheson
authors.forename: J F
authors.initials: JF
authors.lastname: Smyth
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000032:analysis* / Q000097:blood / Q000652:urine; D000818:Animals; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives* / Q000032:analysis / Q000097:blood / Q000652:urine; D004298:Dopamine / Q000032:analysis* / Q000097:blood / Q000652:urine; D006801:Humans; D007668:Kidney / Q000032:analysis; D007980:Levodopa / Q000032:analysis* / Q000097:blood / Q000652:urine; D008099:Liver / Q000032:analysis; D010648:Phenylacetates / Q000032:analysis*; D051381:Rats
chemical_list: D010648:Phenylacetates; D015102:3,4-Dihydroxyphenylacetic Acid; D007980:Levodopa; C017342:gamma-glutamyl DOPA; D004295:Dihydroxyphenylalanine; D004298:Dopamine