Reversible photoreduction of flavin with bilirubin II.

Bilirubin react with flavins under both aerobic and anaerobic conditions. Under anaerobic conditions these substances behave as a redox-system in solution, riboflavin functioning as an electron acceptor and bilirubin as an electron donor. The reaction products are the leuco-form of riboflavin and biliverdin. On the basis of the dependence of the optical spectrum and of the reaction rate on pH it can be assumed that bilirubin reacts in the anionic form. Under anaerobic conditions a reversible reaction occurs leading to a dynamic equilibrium of the reactants. The products were identified and determined by optical spectroscopy, chromatography and potentiometry. Excretion of biliverdin in the stool of new-born infants was orientatively monitored during the phototherapy of hyperbilirubinemia, after the administration of small doses of riboflavin. It has been found that excretion of biliverdin increases during the phototherapy. The possibility of utilizing the described reaction for an improvement in the phototherapy of new-born infant hyperbilirubinemia is discussed.