Lucigenin (bis-N-methylacridinium) as a mediator of superoxide anion production

Lucigenin (bis-N-methylacridinium) (Luc2+) has frequently been used for the luminescent detection of O2-. In fact, the pathway leading to this luminescence requires univalent reduction of Luc2+ to LucH.+ followed by formation of an unstable dioxetane by reaction of LucH.+ with O2-. It is now shown that LucH.+ rapidly autooxidizes and so produces O2-. Luc2+ can thus mediate O2- production in systems, such as glucose plus glucose oxidase, in which there is ordinarily no O2- production. Luc2+ luminescence can thus be used as the basis for assaying superoxide dismutase activity but should not be used for measuring, or even detecting, O2-.