An Overview of Oxidative Stress and Antioxidant Defensive System

Abstract

Free radicals play an important role in cell's life and death. These are unstable/unpaired electrons in their outermost shell and may become highly reactive. Reactive oxygen species (ROS) are generated from molecular oxygen/nitrogen through Electron Transport Chain (ETC), cytochrome P450, and other cellular and sub-cellular functions. They affect beneficial metabolic and cellular processes and also play key role in pathological conditions of the body. It is normally balanced by endogenous antioxidant system. Imbalances in redox status may develop cellular oxidative stress. If the endogenous antioxidants fail to overcome the reactive metabolites production, then exogenous antioxidants would be necessary to balance redox status. Dietary sources, including plants, herbs, spices, vitamins and herbal extracts, play an important role in this regard. This review article summarizes the functional role of Reactive Oxygen Species (ROS), reactive nitrogen species, reactive halogen species and their pathological importance. It also highlights the significant role of endogenous, as well as exogenous antioxidant system in reactive generation of intermediates.