Involvement of NADPH: cytochrome P450 reductase in the activation of indoloquinone EO9 to free radical and DNA damaging species56Abbreviations: EORTC, European Organisation for the Research and Treatment of Cancer; DMPO, 5,5-dimethyl-1-pyrroline-1-oxide; and AN and AH, hyperfine-splitting constants for nitrogen and hydrogen, respectively.