**3. Role of SOD in intracellular parasites**

There are several intracellular protozoan parasites which are causing severe illness in human's beings and if left untreated 100% mortality. These intracellular parasites belonging to the genus *Plasmodium*, *Leishmania,* and *Trypanosoma*, causing a spectrum of diseases like malaria, Leishmaniasis, African sleeping sickness, and Chagas disease in humans [1]. Antioxidant defense of pathogenic protozoan parasites is significantly distinct from each other as well as compared to their mammalian host. Trypanosomatids, as well as *Plasmodium* species have an Fe-containing SOD isoform, which is typically found in bacteria but absent in other eukaryotic cells [32, 33]. The main function of Fe-SOD is to neutralizing the O[−] that are formed during the generation of the superoxide radical [34]. Parasite persistence is determined by a balance between the ability of the immune response and resistance against free radicals produced by host cells. *Leishmania*-infected macrophages are able to produce inflammatory cytokines, ROS, and • NO derivatives, which usually lead to the killing of the phagocytosed microorganism. However, *Leishmania* and *Trypanosoma spp*. are few protozoa that can survive and resist cytotoxic environments within the macrophage, and further, they can able to replicate in such a hostile condition **Table 1** [4, 5].
