3-Hydroxyanthranilic acid-derived compounds formed through electrochemical oxidation

3-Hydroxyanthranilic acid (3-HAA)-derived oxidation products were analyzed using high-performance liquid chromatography with an electrochemical reactor and diode array detection and high-performance liquid chromatography with an electrochemical reactor and UV detection coupled with mass spectrometry. In addition to 3-HAA dimers such as cinnabarinic acid (CA), 6-amino-3-(2-carboxy-6-hydroxyphenyl)amino]-2,5-dioxo-1,3-cyclohexadiene-1-carboxylic acid and 4,7-diamino-8-hydroxy-6H-dibenzoa,d]pyran-6-one-3-carboxylic acid, a 3-HAA trimer and a 3-HAA tetramer were also detected and identified based on their electrospray ionization mass spectra and their UV–visible spectra. These five oxidation products were also detected on the elution profiles of high-performance liquid chromatography–diode array detection analyses for the reaction mixtures of the auto-oxidation of 3-HAA, of 3-HAA with potassium ferricyanide, of 3-HAA with horseradish peroxidase and hydrogen peroxide, and of 3-HAA with superoxide dismutase (SOD). 4,7-Diamino-8-hydroxy-6H-dibenzoa,d]pyran-6-one-3-carboxylic acid was predominant in the auto-oxidation, in the reaction of 3-HAA with horseradish peroxidase and hydrogen peroxide, and in the electrochemical oxidation of 3-HAA at an applied potential of 0.0 V. On the other hand, CA, the 3-HAA trimer and the 3-HAA tetramer were predominant in the reaction of 3-HAA with K₃Fe(CN)₆] and in the electrochemical oxidation of 3-HAA at an applied potential of 1.0 V.