Abstract
The oxidative activities of lumiflavin, riboflavin, flavin mononucleotide and flavin-adenine dinucleo-tide in the excited state are compared by excitation with blue light in the presence of a substrate as hydrogen donor. The order of oxidative activity is flavin mononucleotide > riboflavin > lumiflavin = flavin -adenine dinucleotide = 0. Excited flavin-adenine dinucleotide shows oxidative activity in the presence of urea. A general mechanism is proposed for the oxidation process, which is ascribed to structural factors affecting singlet to triplet transitions in the excited flavins.