Radical scavenging properties of adenosine and derivatives in vitro

The radical scavenging properties of adenosine and related nucleosides were determined. Various protocols were used to assess the reactivity of the compounds toward hydroxyl radicals, superoxide ions, and hypochlorous acid. In the 2-deoxy-D-ribose assay (hydroxyl radicals) all nucleosides tested were equally effective in the presence of EDTA, with rate constants between 10 9 and 10 10 M -1 .sec -1 . However, in the absence of EDTA, resembling in vivo conditions, large differences were observed. An intact cis diol function in the sugar moiety of the compounds appeared important to retain full scavenging activity, probably due to firm complexation of iron ions. The reactivity toward hydroxyl radicals was confirmed in electron spin resonance (ESR) experiments with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin-trapping agent. Superoxide ions and hypochlorous acid did not react with the nucleosides. From the results it is hypothesized that the radical scavenging properties of adenosine play a role in its established cardioprotective actions in vivo.