Study of the mechanism of the photochemical oxidation of bilirubin by high-performance liquid chromatography.

The photochemical degradation of bilirubin was studied in vitro using high-performance liquid chromatography and spectrophotometry. Attention was centered on the formation of biliverdin, which is produced as an intermediate in the photooxidation catalysed by riboflavin. approximate values of the overall and partial relative rate constants were calculated using the physiochemical criteria for a pseudo-monomolecular reaction. A more precise evaluation was made by non-linear regression programmes on a Hewlett-Packard 9835 A computer. In addition to the formation of biliverdin, attention was also paid to accompanying processes affecting the reaction mechanism, which were explained as aggregation and dimerization of bilirubin and biliverdin. It was also found that during phototherapy of newborn babies suffering from hyperbilirubinaemia the level of biliverdin in the plasma increased. The results are discussed from the point of view of phototherapy.