Complex I and cytochrome c are molecular targets of flavonoids that inhibit hydrogen peroxide production by mitochondria

► Flavonoids have different effects on H2O2 production by heart and brain mitochondria. ► Quercetin, kaempferol and epicatechin inhibit mitochondrial H2O2 production. ► Quercetin, kaempferol and apigenin inhibit Complex I activity. ► Epicatechin, quercetin and kaempferol reduce cytochrome c.