Abstract

Glucose oxidase (GOx) is responsible for the generation of hydrogen peroxide in honey. However, several studies have shown a lack of correlation between the amounts of GOx and H2O2 in honey, indicating contributions from other hidden factors; such as the autoxidation of flavonoids catalyzed by metals or the inhibition of GOx activity by themselves. Thus, the aim of this study was to investigate the generation of H2O2 in honey attributable to GOx activity and flavonoid autoxidation, and to evaluate the effects of Cu2+ and Fe3+ on this process. To this end, the research plan considered: (I) Evaluate the effects of Cu2+, Fe3+ and flavonoids on the activity of GOx in an artificial honey as simplified model. (II) Survey the generation of H2O2 in a semi-natural model system consisting of isolated GOx and flavonoid fractions from honeys. (III) Relate the generation of H2O2 to the activity of GOx, flavonoids, copper and iron in natural honey. The results show that flavonoids, Cu2+ and Fe3+ inhibit the activity of GOx. However, the formation of complexes between them attenuates this effect. Moreover, metals promote prooxidant action of flavonoids, particularly flavonols, contributing to the generation of H2O2 in a lesser extent than GOx activity in honey. The evidence indicates that the generation of hydrogen peroxide in honey is due to a complex network of reactions.