An antioxidant is molecule that can inhibit oxidation of other molecules. Oxidation of molecules produces free radicals. These free radicals can cause harmful chain reactions that are responsible for cell damage or cell death, which can be responsible for carcinogenesis or low-density lipoprotein (LDL) oxidations in cardiovascular diseases. Antioxidants neutralize these radicals by donating their electrons, ending the electron taking reaction. Oxidative stress is a characteristic feature in many diseases. The majority of free radicals that damage biological mechanisms are oxygen-free radicals and these are known as ‘reactive oxygen species’ (ROS). ROS can be formed during UV light irradiation, by X rays, gamma rays produced during metal catalyzed reactions are present in the atmosphere as pollutants are produced by neutrophils and macrophages during inflammation and are by products of mitocondrÅŸal catalyzed electron transport systems and various other mechanisms . The disharmony between ROS production and antioxidant numbers to scavenge ROS will increase oxidative stress. ROS are oxygen derived small molecules produced as intermediates in the redox reactions, such as ozone, superoxides, singlet oxygen and hydrogen peroxide. So, ROS play important roles in cellular signaling processes and trigger diseases.

Antioxidants are capable of deactivating free radicals before they attack human cells. Humans have generated highly complex antioxidant systems (enzymic or nonenzymic), which work synergistically and in combination with each other to prevent cells or organs against free radicals. The antioxidants can be endogenous or exogenous eg, as a part of diet or dietary supplements