Incorporation and photodegradation of flavin and indole derivatives in anionic, cationic and neutral micellar dispersions

When riboflavin is irradiated in the presence of tryptophan (Trp), photoproducts toxic for tumour cells are generated (A.M. Edwards et al., J. Photochem, Photobiol. B: Biol. 24 (1994) 179-186). Due to the endogenous nature of these compounds, and considering that flavin interacts directly with the Trp indole ring (type I mechanism), we have investigated the effect of compartmentalization in the interaction between indole and flavin derivatives. The behaviour of compounds more hydrophobic than tryptophan and riboflavin has been studied in micellar dispersions. The partition constant between the micellar and aqueous phase and the photodegradation rate constants are determined for all compounds. A good agreement between the generation of photoproducts and the values of photodegradation rate constants is found. Our results indicate that the presence of ionic micelles hinders photoproduct generation, which is favoured when using neutral micelles. (C) 1999 Elsevier Science S.A. All rights reserved.