Riboflavin sensitized photodegradation of Furaneol in a β-cyclodextrin complex

Abstract

A study on the photodegradation of the widely employed flavoring compound Furaneol (FUR), in the presence of vitamin B2 (Riboflavin, Rf) was carried out, in aqueous and microheterogeneous media. The system as a whole allows the evaluation of FUR stability, since the vitamin is an endogenous natural photosensitizer. In a visible-light-irradiated solution of Rf plus FUR, a complex mechanism of competitive reactions occurs. FUR quenches the singlet (2.7 x 109 M-1s-1) and triplet (6.0 x 108 M-1s-1) Rf electronically excited states and reacts with singlet molecular oxygen (O2(1g)) generated from the triplet excited state of the sensitizer, with a reactive rate constant of 1.97 x 107 M-1s-1. In the oxidation process, two oxygen molecules are incorporated. In the presence of β-cyclodextrin (CD), experimental and theoretical results show the formation of an inclusion 1:1 complex of FUR with the oligosaccharide. The Rf- photosensitized oxidation rates of FUR were higher in the microheterogeneous medium, probably due to the incorporation of FUR in the non-inclusion complex between Rf and CD which may produce O2(1g) near the oxidizable substrate. The overall result of this study demonstrates that visible-light exposure of formulations containing Rf and FUR may cause significant oxidation of the flavoring agent.