title: Determination of D,L-threo-3,4-dihydroxyphenylserine and of the D- and L-enantiomers in human plasma and urine.
abstract: DL-threo-3,4-Dihydroxyphenylserine (DOPS) is increasingly being investigated for treatment of disorders involving defects of the sympathetic nervous system, such as Parkinson's disease, Shy-Drager syndrome and congenital dopamine-beta-hydroxylase deficiency. Whilst L-DOPS is converted by aromatic L-amino acid decarboxylase into natural norepinephrine in vitro, D-DOPS inhibits this process. There are no data on the interaction between D- and L-DOPS in vivo because a reliable method for the measurement of the D- and L-enantiomers in plasma and urine is lacking. We describe here such a method based on reversed-phase chromatography after derivatization with o-phthaldialdehyde and N-acetyl-L-cysteine. Good separation was achieved with this procedure (resolution factor 2.33). Two simple and sensitive methods are also presented for total D,L-DOPS estimation, based on reversed-phase chromatography with electrochemical detection after either deproteinization (DP) or liquid-liquid extraction (LE) as sample preparation steps. The two methods gave identical results (regression line DOPS (DP) = 1.026 DOPS (LE) + 33.28; r = 0.997; n = 52). Excellent agreement was found between the sum of the D- and L-DOPS concentrations and the measured total D,L-DOPS concentration (regression line DOPS (D + L) = 0.955 DOPS (total, LE) + 116.65; r = 0.992; n = 100).
mesh_terms: D000111:Acetylcysteine; D015103:Droxidopa / Q000032:analysis* / Q000097:blood / Q000652:urine; D006801:Humans; D012694:Serine / Q000031:analogs & derivatives*; D013050:Spectrometry, Fluorescence; D013237:Stereoisomerism; D009764:o-Phthalaldehyde
chemical_list: D012694:Serine; D009764:o-Phthalaldehyde; D015103:Droxidopa; D000111:Acetylcysteine