Photo-induced degradation of some flavins in aqueous solution

The blue-light induced photo-degradation of FMN, FAD, riboflavin, lumiflavin, and lumichrome in aqueous solution at pH 8 is studied by measurement of absorption coefficient spectral changes due to continuous excitation at 428 nm. The quantum yields of photo-degradation determined are phi(D)(riboflavin, pH 8) approximate to 7.8 x 10(-3), phi(D)(FMN, pH 5.6) approximate to 7.3 x 10(-3), phi(D)(FMN, pH 8) approximate to 4.6 x 10(-3), phi(D)(FAD, pH 8) approximate to 3.7 x 10(-4), phi(D)(lumichrome, pH 8) approximate to 1.8 X 10(-4), and phi(D)(lumiflavin, pH 8) approximate to 1.1 X 10(-5). In a mass-spectroscopic analysis, the photo-products of FMN dissolved in water (solution pH is 5.6) were identified to be lumichrome and the lumiflavin derivatives dihydroxymethyllumiflavin, formyllumiflavin, and lumiflavin-hydroxy-acetaldehyde. An absorption and emission spectroscopic characterisation of the primary photoproducts of FMN at pH 8 is carried out. (C) 2004 Elsevier B.V. All rights reserved.