Fluorescence spectra and decays of malvidin 3,5-diglucoside in aqueous solutions

Abstract

The fluorescence properties of malvidin 3,5-diglucoside in aqueous solutions at various pH values were investigated using steady state and time-resolved fluorescence techniques. Fluorescence emission bands were assigned to the flavylium cation (AH +) (λ max = 620 nm), hemiacetal (B) (λ max = 370 nm), chalcone (C) (λ max = 435 nm), ionized chalcone (C −) (λ max = 495 nm), quinonoidal base (A) (λ max = 660 nm) and ionized quinonoidal base (A −) (λ max = 665 nm) forms. The fluorescence decays of these forms are, in general, multiexponential. In some cases, this is due to the overlap of more than one emission band, and in others indicates an excited state interconversion between some of these forms.