Table 1.

Production of ROS in different cellular compartments.

ROS species	Source	Reactions
Superoxide radical (•O−2) [28]	Mitochondria associated with Complex I and Complex III	O2 →e− + •O−2 M(n+1)+−SOD + O−2 → Mn+−SOD + O2 (superoxide dismutase) (Mn- Cu (n = 1); Mn (n = 2); Fe (n = 2); Ni (n = 2))
Hydroxyl radical (•OH) [29]	Mitochondria, cytosol	H2O →e− + •OH (UV/x-rays) Mn+−SOD + O−2 + 2H+ → M(n+1)+− SOD + H2O2
Hydrogen peroxide (H2O2) [30]	Mitochondria, cytosol, nucleus	2H2O2 → 2 H2O + O2  (catalase) 2GSH + H2O2→ GS–SG + 2H2O (Glutathione peroxidase)
Singlet oxygen (1O2) [31]	Chlorophyll	3O2 →1O2 (Photosensitizer)