Drug and Chemical Toxicology, 30:67–81, 2007 Copyright © Informa Healthcare ISSN: 0148-0545 print / 1525-6014 online DOI: 10.1080/01480540601017710 LDCT 0148-0545 1525-6014 Drug and Chemical Toxicology, Vol. 30, No. 1, October 2006: pp. 1–33 Drug and Chemical Toxicology Prolonged Quercetin Administration Diminishes the Etoposide-Induced DNA Damage in Bone Marrow Cells of Rats Quercetin Protects Against Etoposide-Induced DNA Damage Kapiszewska et al. Maria Kapiszewska, 1 Agnieszka Cierniak, 1 Monika A. Papiez, 2 Agata Pietrzycka, 3 Marek Stepniewski, 3 and Adam Lomnicki 4 1 Department of General Biochemistry, Faculty of Biotechnology, Jagiellonian University, Krakow, Poland 2 Department of Cytobiology and Histochemistry, Jagiellonian University, Krakow, Poland 3 Radioligand Laboratory, Faculty of Pharmacy, Collegium Medicum, Jagiellonian University, Krakow, Poland 4 Institute of Environmental Sciences, Jagiellonian University, Krakow, Poland The DNA damage in bone marrow cells induced by etoposide (E) injected intraperito- neally to rats (100 mg/kg b.w.) decreased to the control level when quercetin (Q) was administered subcutaneously for 10 consecutive days (40 mg/kg b.w.per day) before E was injected. The antioxidant power (FRAP assay) increased significantly after Q or E com- pared with control rats but did not change when Q preceded the E injection. The superox- ide dismutase activity significantly increased in Q+E-treated rats compared with quercetin given alone. The study provides evidence that Q protects bone marrow cells against long-lived E-induced DNA damage and alters the redox balance in lung tissue. Keywords Antioxidant enzymes, Bone marrow cells, Comet assay, DNA damage, Etoposide, Quercetin, Rats. INTRODUCTION Dietary supplements, mainly antioxidants, are broadly used not only by the population at large for health promotion but also by individuals diagnosed with cancer (Conklin, 2004). They are capable of detoxifying free radicals or Address correspondence to Maria Kapiszewska, Department of General Biochemistry, Faculty of Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Kraków, Poland; Fax: #+48-12-664-6902; E-mail: mkapisz@if.uj.edu.pl