Indoxyl-beta-D-glucuronide, the primary emitter of low-level chemiluminescence in plasma of hemodialysis patients

Characteristic light emission induced by the oxidation of hydroxyl radicals has been found in plasma of hemodialysis patients (Agatsuma et al., Clin Chem 1992;38:48-55). We purified a primary emitter, a chemiluminescent component peaking at 430 nm, by anion-exchange chromatography and reversed-phase HPLC. By using proton nuclear magnetic resonance and authentic indoxyl compounds, we determined the primary emitter to be indoxyl-beta-D-glucuronide. Absorption and fluorescence spectra of the purified sample coincided well with those of authentic indoxyl-beta-D-glucuronide, as did the peak in the chemiluminescence emission spectrum. Retention time of the purified sample on reversed-phase HPLC, measured by fluorescence, was also in accordance with that of indoxyl-beta-D-glucuronide. To our knowledge, this is the first identification of a primary emitter of low-level chemiluminescence from a biological source.