One-electron enzymatic reduction

Chemical Radical metabolite Free radical toxicity Use Ref. 

Quinone anticancer agents Daunomycin Q , Oj Cardiotoxicity Anti-cancer [33-35] 

Nitro-aromatic Nitrofurantoin compounds RNOj-, Oj- Pulmonary edema Anti-bacterial [36] 

Many xenobiotics, including a wide variety of quinones and nitro compounds, will accept an electron from almost any redox flavoenzyme. The microsomal reduction of nitroaromatic compounds, quinones, quinone-imines, some azoaromatic compounds, paraquat, and tetrazolium salts is catalyzed by NADPH-cytochrome P-450 reductase [44], One-electron transfer to these electron acceptors has been proved to be obligatory in the case of quinone and nitro compounds, and is probably obligatory in other cases as well. Therefore, a reduction of an aromatic compound by NADPH-cytochrome P-450 reductase can probably be assumed to form a free radical metabolite. In contrast, free radical formation by reductive dehalogenation is totally cytochrome P-450-dependent, with the reductase being inactive. 

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