Effect of Cu2+-complexation on the scavenging ability of chrysin towards photogenerated singlet molecular oxygen (O-2((1)Delta(g))). Possible biological implications

摘要

Visible-light irradiation of aqueous-ethanolic solutions of Riboflavin (Rf) in the individual presence of the flavone chrysin (Chr) and its complex with Cue} ([Chr(2)Cu]; 2:1 L:M) generates singlet molecular oxygen O-2((1)Delta(g)), that concomitantly interact with both flavone derivatives. Overall (k(t)) and reactive (k(r)) rate constants in the order of 107 M-1 s(-1) were determined for the process. Metal chelation greatly enhances the scavenging ability of [Chr(2)Cu] towards O-2((1)Delta(g)) through a mechanism dominated, in >80%, by the physical component. In this way, practically all O-2((1)Delta(g)) is deactivated by the complex without significant loss of the quencher. The isolated flavone quenches O-2((1)Delta(g)) in a prevailing reactive fashion.