DOI: 10.36347/sajb.2014.v02i02.008

Pages: 110-118

The biochemistry of reactive oxygen species (ROS) such as superoxide anion, hydrogen peroxide, hydroxyl radicals, and singlet oxygen is important in aerobic metabolism of the cell mostly reactive nitrogen species are well recognised for playing dual function as both dangerous and beneficial species. Overproduction of ROS from mitochondrial electron transport chain leakage or excessive stimulation of xanthine oxidase and other oxidative enzymes results in oxidative stress, a process that can be an important mediator of damage to cell structure and function, lipids, proteins, carbohydrates and DNA. In contrast, beneficial effects of ROS/RNS occur at very low concentrations and involve physiological roles in cellular responses in defence against infectious agents, gene expression, cellular growth, in the function of a number of cellular signalling pathways, hypoxia and respiratory burst. In the past and present years, progress has been made in the recognition and understanding of the roles of reactive oxygen species in many diseases. The body protects itself from the potential damages of reactive oxygen species, by utilizing antioxidant enzymes and non-antioxidant enzymes e.g superoxide dismutases, glutathione peroxidases, glutathione reductase and catalase. Scientists have indicated that antioxidant obtained from daily diets such as non-enzymatic antioxidants vitamin E, vitamin C, carotenoids and polyphenols can scavenge the reactive oxygen species. These compounds may also be required as cofactors for antioxidant enzymes or be used by cells for up-regulating enzymatic antioxidants.