Redox Reactions of Sanazole (AK- 2123) in Aqueous Solutions : A Pulse Radiolysis Study

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The redox chemistry of sanazole, an efficient hypoxic cell radiosensitizer, generally referred to as AK-2123, was studied by pulse radiolysis with e_<aq>^- , CO_2^<-.>, 2-propanol radicals and ^.CH2OH radicals. AK-2123 reacts with e_<aq>-, CO_2^<-.> and 2-propanol radicals at almost diffusion-controlled rates, producing a nitro radical anion (λ_<max>= 290 nm) within a few microseconds. The decay kinetics of the radical anion was independent of the pH. The radical anion reacts with oxygen with a rate constant of 3.4×10^6 dm^3 mol^<-1> s^<-1>. An electron-transfer reaction was observed from the thymine radical anion to AK-2123. From redox equilibria with methyl viologen, the one-electron reduction potential of AK-2123 in aqueous solution, determined by pulse radiolysis, was estimated to be -0.33±0.02 V vs. NHE. Depletion of intracellular nonprotein thiols did not mitigate the radiosensitizing affect of the hypoxic radiosensitizer, AK-2123.
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