Generation & Mode Of Action Of Free Radicals & Oxidative Stress With Special Emphasis On Health & Disease Prevention

Abstract

The normal functioning of cells is dependent on a proper balance of pro oxidants and antioxidants. The former promote the release of oxidants to provide energy needed for cell functioning. In this process, different biochemical reactions take place which continuously produce free radicals. Living cells continually generate free radicals or reactive oxygen species (ROS) through the respiratory chain during energetic metabolism. Human body has various intrinsic mechanisms to counteract oxidative stress by producing antioxidants, or through externally derived foods and/or supplements. However whenever there is excess of free radicals their accumulation in the body generates a phenomenon called oxidative stress. As we age, this oxidative and/or nitrosative damages elicit a number of late-onset diseases after ROS/RNS accumulate to certain levels. Cumulative tissue injury thus caused by free radical is now known to underlie the pathogenesis of clinical conditions such as cancer, arthritis, arteriosclerosis, and neurodegenerative diseases. Oxidative stress is marked with expression of specific biomarkers whose specificity towards the various disease condition needs validation. During this process of release of energy to perform normal activities of life, electrons are transferred between the molecules resulting in many Reactive Oxygen Species and the non-oxygen free radicals in the body. However, excessive oxidative stress or inadequacy in a normal cell's antioxidant defence system (or both) can cause the cell to experience oxidative stress. Tumour cells usually have an imbalanced redox status resulting in the damage to DNA, proteins and lipids. Higher levels of DNA damage and deficient DNA repair may predispose individuals to cancer. In this review, summarize the source, balance, maintenance, generation, mode of action and physiological functions of ROS, oxidative stress and its toxic mechanisms underlying a number of diseases and also the biomarkers implicated in selected human diseases and prevented by using antioxidants, functional foods, nutraceuticalsand phytochemicals.