Biochemical activation of AZQ [3,6-diaziridinyl-2,5-bis(carboethoxyamino)-1,4-benzoquinone] to its free radical species.

The aziridinyl quinone 3,6-diaziridinyl-2,5-bis(carboethoxyamino)-1,4-benzoquinone is an antitumor agent that enhances electron flow from reduced nicotinamide adenine dinucleotide phosphate (NADPH) to molecular oxygen in rat liver microsomes, rat liver nuclei, and purified NADPH-cytochrome c reductase. The process is enzymatic and has an optimum pH of 7.5; NADPH is the preferred cofactor. Electron spin resonance studies show the presence of a free radical semiquinone characterized by five hyperfine lines at g = 2.0046.