The one-electron reduction potential of 3-amino-1,2,4-benzotriazine 1,4-dioxide (tirapazamine): a hypoxia-selective bioreductive drug.
The one-electron reduction potential of 3-amino-1,2,4-benzotriazine 1,4-dioxide, tirapazamine (SR 4233) in aqueous solution has been determined by pulse radiolysis. Reversible electron transfer was achieved between radiolytically-generated one-electron reduced radicals of tirapazamine (T), and quinones or benzyl viologen as redox standards. The reduction potential Em7(T/T-) was -0.45 +/- 0.01 V vs. NHE at pH 7 From the pH dependence of the reduction potential, pKa = 5.6 +/- 0.2 was estimated for the tirapazamine radical, a value similar to the pKa determined by other methods.
Gray Laboratory Cancer Research Trust, Mouni Vernon Hospital, Northwood, Middx, UK.
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Priyadarsini
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Tracy
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Wardman
D001594:Benzyl Viologen / Q000737:chemistry; D015687:Cell Hypoxia; D004579:Electron Transport; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D011675:Pulse Radiolysis; D000077704:Tirapazamine; D014227:Triazines / Q000737:chemistry*
D014227:Triazines; D001594:Benzyl Viologen; D000077704:Tirapazamine