International Journal of Pharmacology1811-77751812-5700Asian Network for Scientific Information10.3923/ijp.2007.19.26JunTan LiancaiZhu BochuWang 1200731It is well known that DNA damage plays an important role in carcinogenesis. Quercetin, as an antioxidant and free radical-scavenger, is known to protect DNA from damage produced by Reactive Oxygen Species (ROS) such as hydroxyl free radical (·OH), Hydrogen Peroxide (H2O2) and superoxide ion (O2·G). But quercetin has been reported to be carcinogenic too. Based on the contradiction in terms, we study the effect of quercetin on DNA damage in the presence of cupric ion. Present results show that quercetin has opposite effects on DNA damage induced by cupric ion depending on the concentration of cupric ion. At low concentration of cupric ion, quercetin exerted a protective role. While at higher concentration of cupric ion, quercetin promoted DNA cleavage, which was not inhibited by hydroxyl free radical scavenger. Additionally, quercetin diminished slightly the oxidation of CT DNA by cupric ion plus H2O2 in the 2-thiobarbituric acid-reactive substances (TBARS) assay. So, it can be concluded that oxidative stress is not the only reason for DNA damage induced by quercetin plus cupric ion. We further propose a mechanism for explaining the promoting effect that formation of quercetin copper (II) complexes binding to DNA in an intercalation mode may result in hydrolytic cleavage of DNA. The results may imply that in certain pathological situations quercetin may result in DNA damage rather than exert a protective role to bring on carcinogenesis.]]>Afanas'ev, I.B., A.I. Dorozhko, A.V. Brodshi, V.A. Kostyak and A.I. Potaporitch,19893817631769Ahmed, M.S. and V. Ramesh,19949193197Alina, B. and R.A. Juan,2001262023Torreggiani, A., M. Tamba, A. Trinchero and S. Bonora,2005744-747759766Das, A., J.H. Wang and E.J. Lien,199442133166Duthie, S.J., W. Johnson and V.L. Dobson,1997390141151Galaris, D. and A. Evangelou,20024293103Halliwell, B. and J.M.C. Gutteridge,19993rd Edn.,pp: 105-350pp: 105-350Hussain, S.P., K. Raja, P.A. Amstad, M. Sawyer and L.J. Trudel et al.,2000971277012775Kawanishi, S., Y. Hiraku, M. Murata and S. Oikawa,200232822832Kennedy, L.J., K. Moore Jr, J.L. Caufield, S.R. Tannenbaum and P.C. Dedon,199710386392Komiyama, M., N. Takeda and H. Shigekawa,19991614431451Kulms, D., E. Zeise, B. Poppelmann and T. Schwartz,20022158445851Lloyd, D.R., P.L. Carmichael and D.H. Phillips,199811420427Masataka, Y., H. Miyako, N. Makoto and M. Keiko,199968468472Morel, I., G. Lescoat, P. Cogrel, O. Sergent and N. Pasdeloup et al.,1993451319Naruto, Y., T. Hiroshi and K. Shosuke,1999425107115Negre-Salvayre, A. and R. Salvayre,199212101106Osako, T., S. Nagatomo, T. Kitagawa, C.J. Cramer and S. Itoh,20052O2.]]>10581590Pamukcu, A.M., S. Yalciner, J.F. Hatcher and G.T. Bryan,1980P. aquilinum).]]>4034683472Pattubala, A.N.R., N. Munirathinam and R.C. Akhil,2004200414401446Pedreño, E., A.J. López-Contreras, A. Cremades and R. Peñafiel,20059920742080Rubens de Souza, F.V. and F.W. De Giovani,2004997104Russo, A., R. Acquaviva, A. Campisi, V. Sorrenti, C. Di Giacomo, G.Virgata, M.L. Barcellona and A. Vanella,2000169198Selvakumar, B., V. Rajendiran, P. Uma Maheswari, H. Stoeckli-Evans and M. Palaniandavar,2006100316330Wojciech, B. and S.K. Kazimierz,20021275562Yamamoto, K. and S. Kawanishi,19892641543515440Yamashita, N., M. Murata, S. Inoue, M.J. Burkitt, L. Milne and S. Kawanishi,199811855862Zhou, J., L.F. Wang, J.Y. Wang and N. Tang,2001265793