. 2019 Jan 24;55(2):26. doi: 10.3390/medicina55020026

Table 1.

Major ROS and RNS of physiological importance.

Major ROS		Sources
Free Radicals	Hydroxyl radical ( $O H^{•}$ )	Decomposition of ONOO⁻ or, HOCl
	Superoxide radical ( $O_{2}^{• -}$ )	Electron transport systems, and one-electron reduction of O₂ by respiratory burst via the action of membrane bound NADPH oxidase
	Peroxyl radical (ROO^•)	Produced in the Fenton reaction
Non-Radicals	Hydrogen peroxide (H₂O₂)	Activated macrophages during inflammation
Non-Radicals	Hypochlorous acid (HClO)	Combined activities of NADPH oxidase and myeloperoxidase (MPO) in phagocytes
	Lipid peroxides (ROOH)	Formed from oxidation of polyunsaturated fatty acid via lipid-peroxyl radical reaction
Major RNS		Sources
Free Radicals	Nitric oxide (NO^•)	Nitric Oxide Synthase (NOS)
Free Radicals	Nitrogen dioxide ( $N O_{2}^{•}$ )	Activated neutrophils
Non-radicals	Dinitrogen trioxide (N₂O₃)	Produced in pathological conditions where (inducible nitric oxide (iNOS) is upregulated
	Peroxinitrite (ONOO⁻)	Produced in pathological conditions where iNOS is upregulated
	Nitrite ( $N O_{2}^{-}$ )	Oxidation product from NO, formed during NOS activation in inflammatory diseases
	Nitryl ion ( $N O_{2}^{+}$ )	Activated neutrophils