Naturally present metal ions in plants could interfere with common antioxidant assays

Most of the commonly applied assays used to assess antioxidant properties of plant extracts exploit the ability of some biologically active metabolites to participate in oxidation-reduction reactions with metal ions. On the other hand, most plants contain different chelated metal ions whose levels depend on the geographic origin, soil, and environmental pollutions. In this study the levels of redox-active metal ions in three plant sources were measured and extracts of these botanicals were treated with Chelex(Ⓡ) • The proposed pre-analytical procedure is simple and does not require special instrumental equipment. • Preliminary depletion of redox active metal ions, namely iron and copper ions could improve reproducibility of the analytical methods. • The method allows a more reliable comparison of antioxidant properties of particular botanical species from different geographic regions.