Riboflavin derivatives for enhanced photodynamic activity against Leishmania parasites

Riboflavin derivatives with various substituents (O-acyl, N-methyl, N-alkylcarboxyalkyl or N-alkyl(trialkyl)ammonium) have been prepared and spectroscopically characterized (absorption, emission and fluorescence quantum yields). Their quantum yields of photosensitized singlet molecular oxygen production (ΦΔ 0.24–0.58) and octanol/water partition coefficients (Pow ≤0.01–11) were measured. Preliminary studies indicate that all derivatives display higher phototoxicity against the human protozoan parasite Leishmania than the parent riboflavin, with negligible toxicity in the absence of light. Their photodynamic action shows a higher correlation with Pow than with ΦΔ, opening up their potential application to cutaneous diseases treatment.