tailieunhanh - Báo cáo khoa học: Anti- and pro-oxidant effects of quercetin in copper-induced low density lipoprotein oxidation Quercetin as an effective antioxidant against pro-oxidant effects of urate

We recently reported that, depending on its concentration, urate is either apro- or anantioxidant inCu 2+ -induced low-density lipoprotein (LDL)oxidation. We also previously demonstrated an antioxidant synergy between urate and some flavonoids in the Cu 2+ -induced oxidation of diluted a result, the effectof theflavonoidquercetinon the Cu 2+ -induced oxidation of isolated LDL has been studied either in the presence or absence of urate. | Eur. J. Biochem. 271 1991-1999 2004 FEBS 2004 doi Anti- and pro-oxidant effects of quercetin in copper-induced low density lipoprotein oxidation Quercetin as an effective antioxidant against pro-oxidant effects of urate Paulo Filipe1 2 Josiane Haigle3 Joao Nuno Silva1 2 Joao Freitas1 2 Afonso Fernandes1 Jean-Claude Maziere4 Cecile Maziere4 Rene Santus3 5 and Patrice Morliere3 5 1Centro de Metabolismo e Endocrinologia and 2Clinica Dermatologica Universitária Faculdade de Medicina de Lisboa Hospital de Santa Maria Lisbon Portugal 3Museum National d Histoire Naturelle RDDM Photobiologie - INSERM Paris France 4Laboratoire de Biochimie Universite de Picardie Jules Verne U Amiens Hopital Nord Amiens France 5Institut de Recherche sur la Peau INSERM Hopital Saint-Louis Paris France We recently reported that depending on its concentration urate is either a pro- or an antioxidant in Cu2 -induced low-density lipoprotein LDL xxidation. We i4o previously demonstrated an antioxidant synergy between urate and some flavonoids in the Cu2 -induced oxidation of diluted serum. As a result the effect of the flavonoid quercetin on the Cu2 -induced oxidation of isolated LDL has been studied either in the presence or absence of urate. We demonstrate that like urate quercetin alone at low concentration exhibits a pro-oxidant activity. The pro-oxidant behavior depends on the Cu2 concentration but it is not observed at high Cu2 concentration. When compared with urate the switch between the pro- and the antioxidant activities occurs at much lower quercetin concentrations. As for urate the pro-oxidant character of quercetin is related to its ability to reduce Cu2 with the formation of semioxidized quercetin and Cu with an expected yield larger than that obtained with urate owing to a more favorable redox potential. It is also shown that the pro-oxidant activity of urate can be inhibited by quercetin. An electron transfer between quercetin and .