IDENTIFICATION OF METABOLITES OF SULFOBROMOPHTHALEIN *

Abstract

The 2 major ninhydrin-positive metabolites of sulfobromophthalein appearing in human bile were isolated by column and paper chromatog-raphy. Their chemical characteristics were studied as follows: Hydrolysis of the purified metabolites with concentrated hydrochloric acid at 120[degree] C revealed the presence of the amino acids, glycine, glutamic acid and possibly cysteine. Similar treatment of control bile containing no sulfobromophthalein also resulted in the appearance of considerable amounts of glycine and glutamie acid. Hydrolysis of the metabolites with hydrobromic acid more clearly demonstrated the presence of cysteine, which was not detectable in the control bile after similar treatment. Both controls and metabolite fractions contained glycine and glutamic acid. Treatment of both metabolites with Raney-nickel resulted in release of desulfurated cysteine (alanine). Controls were negative. Staining with potassium dichromate-silver nitrate gave a positive reaction, indicating the presence of a mercaptide in the metabolites. Synthetic complexes of BSP with cysteine, cystine or glutathione had the same chromatographic mobility as the two naturally occurring metabolites. Amino acids lacking the sulhydryl group failed to form complexes. It was concluded that BSP is excreted at least in part as a mercaptide with cysteine or the peptide glutathione.