Table 1.

List of ROS and RNS produced during metabolism [16, 17, 19]

Free radical	Symbol	Half-life
Reactive oxygen species-ROS
Radicals
Superoxide	O2 •−	10−6 s
Hydroxyl	OH•	10−10 s
Alkoxyl radical	RO•	10−6
Peroxyl Radical	ROO•	17 s
Non radicals
Hydrogen peroxide	H2O2	Stable
Singlet oxygen	1O2	10−6 s
Ozone	O3	s
Organic peroxide	ROOH	Stable
Hypochlorous acid	HOCl	Stable (min)
Hypobromous acid	HOBr	Stable (min)
Reactive nitrogen species-RNS
Radicals
Nitric oxide	NO•	sa
Nitrogen dioxide	NO•2	s
Non radicals
Peroxynitrite	ONOO−	10−3 s
Nitrosyl cation	NO+	s
Nitroxyl anion	NO−	s
Dinitrogen trioxide	N2O3	s
Dinitrogen tetraoxide	N2O4	s
Nitrous acid	HNO2	s
Peroxynitrous acid	ONOOH	Fairly stable
Nitryl chloride	NO2Cl	s

^a The half life of some radicals depends on the environmental medium, for example the half life of NO^• in an air saturated solution may be few minutes. S seconds, min minutes