Antioxidants or free radical scavengers are the molecules which prevent free radicals and other potentially toxic oxidizing species from damaging cells and organisms. The source of antioxidants are either endogenous, i.e. produced by our body, or exogenous, i.e.. obtained via nutrition. Endogenous antioxidants are classified into two subgroups of enzymatic such as dismutase, reductase, catalase, peroxidase, etc. and non-enzymatic such as glutathione, bilirubin, metallothioneins, and uric acid. However, as the amount of free radicals is often higher than the capacity of endogenous antioxidants to detoxify, it is necessary to obtain some antioxidants from external sources (vitamin A, vitamin C, and vitamin E) to balance the disequilibrium. As antioxidants are different in their reducing capacity, the Ferric Reducing Antioxidant Power (FRAP) is utilized to evaluate the reducing power of antioxidants in comparison to ascorbic acid as a standard. The antioxidant capacity of biological samples is considered as an indicator of the overall potential of body against undesired effects of reactive oxygen species (ROS) and oxidative stress-related diseases.