Table 1.

Main ROS and their effects

Species	Chemical structure	Description	Occurrence	Action
Superoxide radical	O2−	Most potent radical in the induction of cellular damage	Almost all aerobic cells	Majority of reactions as a reducing agent
Hydroxyl radical	OH•	O2− acid conjugate, highly reactive	Formed through water radiolysis	DNA, proteins, carbohydrates and lipids
Hydrogen peroxide	H2O2	It is not a free radical because did not submit electrons paired in the last layer	Reactions for the production of OH•	Proteins and lipids
Singlet oxygen	1O2	Excited form of molecular oxygen. It is not a free radical, because did not submit electrons paired in the last layer	Generated by phagocytes, luminous induction and catalysed reactions by peroxidases	DNA changes

Adapted from Oliveira MC et al. (2010).⁷⁸