Redox reactions of 3'-azido-3'-deoxythymidine (AZT) and interaction of its OH-derived radical with bilirubin and riboflavin: A pulse radiolysis study |
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Authors: | Ravi Joshi Soumyakanti Adhikari Tulsi Mukherjee |
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Institution: | (1) Radiation Chemistry and Chemical Dynamics Division, Bhabha Atomic Research Centre, Mumbai, 400 085, India |
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Abstract: | Using the technique of pulse radiolysis, redox studies of 3-azido-3-deoxythymidine (azidothymidine or AZT) with hydrated electron and hydroxyl radicals, generated in phosphate-buffered aqueous medium, are reported. The hydrated electron reacts with AZT (k = 1.9 × 1010 dm3 mol-1 s-1) to generate transients with absorption maxima at 300 and 340 nm. The hydroxyl radical adds to AZT to generate transients with absorption maxima at 310 and 365 nm, with formation rate constant of 9.0 × 109 dm3 mol-1 s-1 as observed at 310 and 365 nm. The secondary radical 6-hydroxy-5-yl-azidothymidine, formed in the reaction of AZT with hydroxyl radical, reacts with bilirubin to give a transient of bilirubin with bimolecular rate constant of 1.8 × 108 dm3 mol-1 s-1. In the reaction of hydroxyl radical with AZT/riboflavin pair, an . H atom transfer from riboflavin to the 6-hydroxy-5-yl-azidothymidine is observed. Reactions of OH-derived radicals of thymine with bilirubin and riboflavin are similar to that of AZT. Possible mechanisms are proposed for the observed reactions. |
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