Radical scavenging and chemical repair of rutin observed by pulse radiolysis: as a basis for radiation protection

Pulse radiolysis was conducted to investigate: several fundamental reactions of a natural flavonoid, rutin, and its glycosylated form (alpha G-rutin) as a basis for their radiation protection properties; the reactions with (OH)-O-center dot (radical scavenging) and dGMP radical, dGMP(center dot) (chemical repair), which was used as a model of initial and not yet stabilised damage on DNA. Three absorption peaks were commonly seen in the reactions of the flavonoids with (OH)-O-center dot, showing that their reactive site is the common structure, i.e. aglycone. One among the three peaks was attributed to the flavonoid radical produced as a result of the removal of a hydrogen atom. The same peak was found in their reactions with dGMP(center dot), showing that dGMP(center dot) is chemically repaired by obtaining a hydrogen atom supplied from the flavonoids. Such a spectral change due to the chemical repair was as clear as never reported. The rate constants of the chemical repair reaction were estimated as (9 +/- 2)x10(8) M-1 s(-1) and (6 +/- 1)x10(8) M-1 s(-1) for rutin and alpha G-rutin, respectively. The rate constants of the radical scavenging reactions towards (OH)-O-center dot were estimated as (1.3 +/- 0.3)x10(10) M-1 s(-1) and (1.0 +/- 0.1)x10(10) M-1 s(-1) for rutin and alpha G-rutin, respectively. In addition, there was no obvious difference between rutin and alpha G-rutin, indicating that the glycosylation does not change early chemical reactions of rutin.