Riboflavin-sensitized photoprocesses of tryptophan.

The photodegradation of tryptophan in oxygen saturated aqueous solution sensitized by riboflavin is accompanied by the generation of the following reactive oxygen species: 1O2, OH., H2O2 and O2.-. When parallel photodegradation experiments are run with 14C-riboflavin in one case and 14C-tryptophan in the other and the irradiation products are separated by Sephadex G-15 and C18-HPLC, the generation of the following species is detected: aggregate forms of riboflavin, indolic products associated to flavins, indolic products of molecular weight higher than tryptophan, formylkynurenine, and other tryptophan photodecomposition products. The significance of the riboflavin anion radical and tryptophan cation radical as intermediates in the photoproduct formation is discussed.