The identification of Thormählen positive melanogen "A" from the urine of melanoma patients as 6-methoxy-5-indolylglucosiduronate.

The Thormählen positive melanogen previously determined as "A" has been isolated from melanotic urine by means of column chromatography on Amberlite IR 45, DEAE cellulose and Dowex 50. According to its behavior during a study with 1H--NMR spectra it has been found that the isolatd compound is 6-methoxy-5-indolyglucosiduronate, the metabolite of 5,6-dihydroxyindole. The possible formation and biotransformation of this compound is discussed.