Indolic urinary melanogens: separation and identification by gas chromatography with selected-ion monitoring mass spectrometry of 5-hydroxy-6-methoxyindole-2-carboxylic and 5-methoxy-6-hydroxyindole-2- carboxylic acids.
Two isomeric urinary melanogens, 5-hydroxy-6-methoxyindole-2-carboxylic acid and 5-methoxy-6-hydroxyindole-2-carboxylic acid, have been separated by gas chromatography with selected-ion monitoring mass spectrometry. After chemical synthesis of one of these two isomers, 5-methoxy-6-hydroxyindole-2-carboxylic acid, and the establishment of the mass spectrum of its trimethylsilylated derivative, a 30-ml sample of a melanotic 24-h urine was adjusted to pH 1 and extracted twice with 10 ml of ethyl acetate. The extract was evaporated to dryness and the residue derivatized with methyl-8, followed by Tri-Sil/TBT. Silylated derivatives were analysed by gas chromatography with selected-ion monitoring mass spectrometry. The mass spectrum of the 5-methoxy-6-hydroxyindole-2-carboxylic acid allowed the determination of the retention times of both isomers.
Duthel
J M
JM
Laboratory of Biochemistry, Toxicology and Trace Analysis, Edouard Herriot Hospital, Lyon, France.
Vallon
J J
JJ
D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007211:Indoles / Q000652:urine*; D007477:Ions; D008543:Melanins / Q000652:urine*
D007211:Indoles; D007477:Ions; D008543:Melanins; C009904:melanogen; C017407:5-hydroxy-6-methoxy-2-indolylcarboxylic acid; C017408:6-hydroxy-5-methoxy-2-indolylcarboxylic acid