Synergism and antagonism between quercetin and other chain-breaking antioxidants in lipid systems of increasing structural organisation

Antioxidative effect of quercetin was affected differently in neat sunflower oil, in methyl linoleate o/w emulsion and in phospholipid liposomes by the other chain-breaking antioxidants, alpha-tocopherol, rutin and astaxanthin. Quercetin was better than or comparable to alpha-tocopherol as an antioxidant in the three lipid systems. The presence of alpha-tocopherol showed a strong synergistic effect for quercetin in the emulsion, less in the liposomes and a clear antagonistic effect in the neat oil. Astaxanthin, without any effect alone in neat oil or in the liposomes, but with some effect in the emulsion, did not affect quercetin as an antioxidant. Rutin was only effective as an antioxidant in the liposomes where rutin showed clear synergism with quercetin. The interaction of quercetin with the other antioxidants is classified according to the structural organisation of the lipid substrate. (c) 2006 Elsevier Ltd. All rights reserved.