Antioxidant and free radical scavenging activity of iron chelators

Inside the human body, reactive derivatives of oxygen, known as reactive oxygen species (ROS) such as the superoxide radical (O-2(center dot)), hydroxyl radical ((OH)-O-center dot) and hydrogen peroxide (H2O2), are constantly generated. The ROS easily cause oxidative damage to various biomolecules such as proteins, lipids and DNA leading to various disease conditions. Iron chelators function as antioxidants by scavenging ROS and also reduce the amount of available iron thereby decreasing the quantity of (OH)-O-center dot generated by Fenton reactions. In this study, the antioxidant activity of the iron chelators: caffeic acid (CA), 2,3-dihydroxybenzoic acid (DHBA), desferroxamine B (FOB) and benzohydroxamic acid (BHA) were determined using five different in vitro antioxidant assays. The antioxidant assays used were: iron binding ability, reducing ability using the potassium ferricyanide reduction method, 1,1diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, H2O2 scavenging activity and (OH)-O-center dot scavenging activity. The standard used for the iron binding ability was Na(2)EDTA whereas vitamin C was used as a standard for the remaining assays. The iron chelators showed a concentration dependent increase in their radical scavenging activities as well as their reducing ability. At the concentration of 1 mM, FOB had the highest iron binding ability of 93.7% whereas DHBA had the lowest iron binding ability of 5.0% compared to the standard Na2EDTA which had 94.8%. The iron chelators, with the exception of BHA, showed good reducing ability than vitamin C. Caffeic acid showed significant DPPH, hydrogen peroxide and hydroxyl radical scavenging activities of 84.7%, 99.8% and 14.5%, respectively. All the iron chelators were observed to show significant activities in all five antioxidant assays. (C) 2015 The Authors. Published by Elsevier Ireland Ltd. This is an open access article under the CC BY-NC-ND license