Evaluation of Antioxidant Interactions of Combined Model Systems of Phenolics in the Presence of Sugars.

The aim of this study was to determine the antioxidant activity of model systems of phenolics (individual and combinations) without and with the addition of sugars (sucrose or trehalose). Also, the synergistic or antagonistic effects of the phenolics in all model systems were evaluated. The results for the antioxidant activity were obtained by three assays, ABTS+', DPPH' and FRAP. ABTS" and DPPH' assay showed that quercetin and gallic acid had the same antioxidant activity, higher than catechin. When the FRAP assay was applied, the order of increasing of antioxidant activity was quercetin < gallic acid < catechin. The highest synergistic effect was achieved in the model system of catechin, quercetin and gallic acid. Addition of sugars, sucrose and trehalose, influenced both antioxidant activity and synergistic effect of phenolics in the model systems. The highest synergistic effect in the model systems with sucrose addition was observed with catechin, quercetin and gallic acid, while in samples with trehalose, the highest synergistic effect was in combination with catechin and gallic acid. Interactions of phenolics and phenolics/sugars caused changes in antioxidant activity as well as synergistic effects.