The chemistry of Klett’s test for urinary indican

Urinary indican is a biomarker. This analyte can be detected by a series of oxido reduction reactions after acidolysis of indoxyl sulfate. Then the key intermediates condense to afford indigo blue and indigo red, the latter in less proportion. In his test for indican Klett used ammonium persulfate in acidic medium, the reactive species being the powerful oxidant peroxydisulfuric acid. Since the reaction series occurring in this test has not been advanced we provide it as well as the reaction mechanism with the electron flow. This test has both pharmacological and chemical interest. Its mechanism is sui generis, for instance there is desulfation at one position and then sulfation in other site, and a symmetrical reagent is reacting as a rather polarized one.