Interactions between quercetin and catechin in a model matrix: Effects on the in vitro antioxidant behaviour

A hydroalcoholic medium at pH 3.5, containing Fe3+ and pyruvic acid, was used as the model matrix to study quercetin/catechin interactions and their possible influence on the antioxidant characteristics of the system. Incubation at 55 °C for a period of 20 days resulted in a complete disappearance of quercetin and a decrease of catechin concentration by almost 75%. Liquid chromatography-mass spectrometry analysis showed that the degradation products are mainly quercetin derivatives, but evidence also indicated that there may be the formation of a co-pigment-like, decarboxylated pyruvic acid-bridged quercetin/catechin adduct. The hydroxyl free radical scavenging activity (SAHFR) exhibited significant negative correlation (P < 0.05) with both quercetin and catechin concentration whereas the antiradical activity (AAR) was positively and significantly (P < 0.05) linked only with quercetin, stressing its importance as natural antioxidant agent with a key role in food systems.