ABSTRACT
Free radicals are a highly unstable species with a single electron in their atomic electron shell. Because of their attempt to establish the balance, they bind electrons from other atoms or molecules, where they trigger biochemical instability that mostly ends up with successive chain reaction (Ríos-Arrabal et al., 2013) and oxidation of lots of biomolecules such as proteins, lipids, and DNA. Under physiological condition, free radicals are formed during ATP production in mitochondria or as metabolic products in liver cells. They are also formed in muscle cells during exercise or in phagocytes during immune reaction. Physiologically, they show an essential function in protecting an organism from infection or in keeping the regular metabolism of cells; however, their occurrence in high concentrations represents a signicant risk to human health (Juranek et al., 2013; Ríos-Arrabal et al., 2013).
