Abstract
The repair activities and mechanisms of both silybin (3,5,7-trihydroxy-2-[3-(4-hydroxy-3-methoxyphenil)-2-hydroxymethyl-1,4-bentreatment bone zodioxan-6-il]-chronan-4-one) and its analogues towards the oxidizing deoxyguanosine monophosphate (dGMP) hydroxyl radical adduct were investigated with pulse radiolysis techniques. On pulse irradiation of nitrous oxide saturated 2.0 mM dGMP aqueous solution containing 0.01 mM silybin at neutral pH (2 mM phosphate buffer), the transient absorption spectrum of the dGMP hydroxyl radical adduct (dGMP-OH) decays following the formation of phenoxyl radical of silybin within tens of microseconds. This indicates that there is a repair reaction between dGMP-OH and silybin. The rate constant of the repair reaction was calculated to be 1.0×109 M-1s-1 for silybin .The repair activity of hesperetin, naringin and naringenin towards dGMP-OH were also measured. A comparison of the rate constants of the four flavanones shows that silybin has highest reparation activities towards dGMP-OH adduct. These results imply that non-enzymatic fast repair might be a universal repair mechanism of phenolic antioxidants.
