Figure 1: Oxidative stress mechanisms. GSH (glutathione) and vitamin C (ascorbic acid) and vitamin E (-tocopherol) are nonenzymatic antioxidants that assist in antioxidant defence against reactive oxygen species (ROS), to inhibit or repair damage to cells. Scavenging enzymes GPx (glutathione peroxidase), SOD (superoxide dismutase), and CAT (catalase) work to prevent oxidative damage by detoxifying reactive oxygen species (ROS). Environmental ROS as well as cell generated ROS like H2O2 (hydrogen peroxide), OH (hydroxyl free radical), (superoxide anion), and (peroxynitrite) are all prooxidants that when in abundance can lead to an imbalance in the redox homeostasis causing oxidative stress, which have detrimental effects to lipid membranes, proteins, and DNA.