Identification of 5-hydroxy-6-indolyl-O-sulfate in urine of patients with malignant melanoma.

It has previously been shown that enzymatically hydrolyzed urine of patients with malignant melanoma contains 5,6-dihydroxyindole (5, 6DHI ). In this study we describe the elucidation of the entire structure of urinary 5, 6DHI -conjugate. Differential hydrolysis of melanotic urine revealed that, in contrast to beta-glucuronidase, sulfatase can liberate 5, 6DHI from its conjugated form. 5, 6DHI -sulfate was synthetized by reacting 5, 6DHI with sulfur trioxide trimethylamine complex. Thin-layer chromatography (TLC) documented its close similarity to the Thorm ahlen -positive compound usually entitled "C." Gas chromatographic-mass spectrometric (GC-MS) analysis of methylated and subsequently hydrolyzed synthetic 5, 6DHI -sulfate showed that the synthetic product consisted of a mixture of 5-hydroxy-6-indolyl-O-sulfate and 6-hydroxy-5-indolyl-O-sulfate (with a certain amount of 5, 6DHI -disulfate). 5, 6DHI -sulfate was purified with use of DEAE-cellulose column chromatography from melanotic urine. Methylation of this conjugate with deuterated dimethylsulfate and subsequent GC-MS analysis of the hydrolyzed product provided evidence that 5, 6DHI from melanotic urine was almost exclusively sulfated in position 6. It was concluded (1) that 5, 6DHI is excreted as a 6-O-sulfate, and (2) that this compound is consistent with Thorm ahlen -positive compound "C".