Studies on the Diazo Reaction of Three Bilirubin Isomers

Abstract

We described the diazo reaction of bilirubins IIIα, IXα and X IIIα, using various diazonium salts. These bilirubin isomers reacted with diazonium salts to form an azo dye with a slightly different absorption peak. There was little difference in the rate constant between these three isomers, while a significant difference in the color intensity of the azo dyes was observed. It has been reported that serum bilirubin in human adults is bilirubin IXα, but in patients' sera after storage bilirubins IIIα and X IIIα were also detected by means of thin layer chromatography. The relative proportions of formation of these three isomers were correlated with serum total bilirubin concentration.