DETERMINATION OF 1,3-THIAZOLIDINE-CARBOXYLIC ACIDS IN URINE BY REVERSED-PHASE HPLC AFTER FLUORESCENCE LABELING WITH DANSYL CHLORIDE

Hyperoxaluria (HOU) - a severe inherited disease - is caused by accumulation of the cytotoxic glyoxylic acid. Spontaneous, not enzyme-mediated formation of 1,3-thiazolidines by condensation of glyoxylic acid with sulphur-containing biogenic amines or amino acids is the key step of our "chemical" concept for the therapy of glyoxylate-induced oxalurias. A sensitive and reliable high-performance liquid chromatographic (HPLC) assay for the determination of these highly polar alkaloid-type heterocycles and their precursors, L-cysteine, cysteamine, and D(-)-penicillamine, has been developed, based on the pre-chromatographic derivatization of secondary amines with dansyl chloride to form yellow fluorescent compounds. Series of tests, monitoring diastereomeric 5,5-dimethyl-thiazolidine-2(R,S)-4(S)-dicarboxylic acids after dansylation in matrix-free solution and in urine, respectively, using an external standard method, are presented. The detection limit for urine samples was determined to be 2-3 nmol/ml.