title: Improved method for analysis of cysteinyldopa in human serum.
abstract: 5-S-L-Cysteinyl-L-dopa is a well-known pigment intermediate and analysis of its serum concentration is well suited for evaluation of treatment and follow-up of stage III and IV malignant melanoma. A simplified analytical method is described using organic extraction followed by clean-up on a boronate gel to capture the compound containing vicinal hydroxyls. Weak acid solution elutes the 5-S-cysteinyldopa suitable for high-performance liquid chromatography (HPLC). The absolute recoveries of cysteinyldopa and its diastereomer 5-S-D-cysteinyl-L-dopa (used as an internal standard) were 81.5 +/- 2.8% and 81.3 +/- 2.7%, respectively, and use of the internal standard for the whole procedure gave an analytical recovery of 101 +/- 0.8%. The limit of quantitation was 1.5 nmol/L and the imprecision of the method was < 5.0% over the analytical range 1.5-500 nmol/L. The method is cheap and easy to perform and compares well with other described techniques. The use of the method is illustrated by results obtained during treatment of a patient with metastatic malignant melanoma.
authors.affiliation: Department of Biomedicine and Surgery, Division of Clinical Chemistry, University Hospital, Linköping, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Arstrand
authors.forename: A
authors.initials: A
authors.lastname: Kullman
authors.forename: R
authors.initials: R
authors.lastname: Andersson
authors.forename: T
authors.initials: T
authors.lastname: Rasmuson
authors.forename: B
authors.initials: B
authors.lastname: Kågedal
mesh_terms: D000368:Aged; D002624:Chemistry, Clinical / Q000379:methods*; D002851:Chromatography, High Pressure Liquid; D003548:Cysteinyldopa / Q000097:blood*; D006801:Humans; D008545:Melanoma / Q000097:blood / Q000556:secondary; D015203:Reproducibility of Results; D012878:Skin Neoplasms / Q000097:blood / Q000473:pathology
chemical_list: D003548:Cysteinyldopa