Free radicals: A review

Abstract

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are normally produced in aerobic organisms. Free radicals play a physiological role being necessary for cellular functioning because redox reactions are the basis for numerous biochemical pathways as well as cellular chemistry, biosynthesis of macromolecules and metabolic regulation. They can able to act as second messengers, producing the stimulation of cell proliferation and being mediators for the activation of cells. However, ROS and RNS can also lead to unwanted oxidation reactions when accumulate and if they are in high amounts they can produce toxic effects. The organism must confront and control the presence of both pro-oxidants and antioxidants continuously. The balance between these is tightly regulated and extremely important for maintaining vital cellular and biochemical functions. Although the exposure of the organism to ROS is extremely high from exogenous sources, the exposure to endogenous sources is much more important and extensive. The dual nature of these species with their beneficial and deleterious characteristics implies the complexities of their specific functioning at a biological site.

Keywords

Antioxidants - free radicals - oxidative stress