Flavonoids are the largest class of polyphenolic substances found in plants. Some epidemiological studies found a reverse correlation among flavonoid-rich diets and disease risk, what may be attributed to a potential antioxidant character of these substances. Our ongoing investigation aims to evaluate the antioxidant properties of rutin, a flavonoid glycoside, in oxidative processes mediated by Fe(II) and Fe(III) in vitro. Supression of oxidative damage to 2-DR (2-deoxyrribose) mediated by 30 mM Fe(III)-EDTA (1:1 ratio)/O₂ or to 30 mM Fe(III)-citrate (1:1 ratio)/O₂ plus 200 mM ascorbate in phosphate buffered media was not observed when rutin was added to reaction media even at higher concentrations. Under same conditions, addition of desferrioxamine (DFO) to media suppressed 2-DR degradation up to 37.5%. In fact, when results from 2-DR degradation in reactions employing O₂ and Fe-citrate (in 1:1 ratio, concentrations from zero to 150mM) plus 200 mM ascorbate or unchelated Fe(III) (concentrations up  to 150 mM) and O₂ plus 200 mM ascorbate in phosphate buffered media were compared to TBARS resulting from degradation promoted by Fe(III)-rutin/O₂ and ascorbate (same concentrations and conditions) discrete but consistently higher TBARS results were found in the later condition, what may be related to chelation.  In contrast, rutin was a very efficient suppressor of lipid peroxidation. Rutin (60 mM) totally inhibited rat liver homogenate lipid peroxidation induced by Fe(III)/ascorbate (iron 30 mM, 200 mM ascorbate, measured TBARS 1.49 nmol/ml). Measured TBARS values for control experiments employing same Fe (III)/ascorbate concentrations and conditions, performed with 60 mM citrate or 100 mM BHT (butylated hydroxytoluene) were respectively 10.84 nmol/ml and 1.59 nmol/ml. (TBARS measured for media with ascorbate, buffer and rat liver homogenate was 2.14 nmol/ml.) Acknowledgments: Antonieta Alencastro (UnB), PRONEX, CNPq and Projeto Milenio-Redoxoma.