In order to cope with
excessive amounts of ROS, cells have evolved biological defense
systems, composed of nonenzymatic antioxidants such as vitamin
C, vitamin E, and reduced glutathione (GSH) as well as antioxidant
enzymes such as superoxide dismutase (SOD), glutathione reductase
(GR), glutathione peroxidase (GPx), glutathione S-transferase
(GST), and catalase (CAT)