Antioxidant/pro-oxidant properties of model phenolic compounds. Part II: Studies on mixtures of polyphenols at different molar ratios by chemiluminescence and LC-MS

► Quercetin and ascorbic acid at molar ratio 2:1 show strong antioxidant activity. ► Quercetin and caffeic acid at molar ratio 1:2 show very weak antioxidant activity. ► Catechin and caffeic acid at a molar ratio of 1:3 show very weak antioxidant activity. ► Efficient cycling of o-quinones may result in strong antioxidant activity. ► LC-MS assisted proof for redox cycling of o-quinones.