Fig. 4

Redox properties of naphthoquinones. a One-electron reduction of the naphthoquinone core, first to the radical semiquinone and then to the hydroquinone. b Reduction of the naphthoquinone core in a biochemical context in the presence of NADPH under aerobic conditions, with the resulting production of the superoxide radical anion. It is important to consider that semiquinones cannot be reoxidized to quinones without oxygen and, therefore, can accumulate in the cell in anaerobic conditions [2]