Repair effect of thymine radical anion by echinocoside using pulse radiolysis

Repair activities of thymine radical anion by echinocoside, isolated from Pedicularis plicata, were studied using pulse radiolysis technique. The thymine radical anion was produced by the reaction of hydrated electron with thymine. Echinocoside, one of the polyphenols of phenylpropanoid glycoside, was added to the thymine aqueous solution saturated with N-2. Kinetic analysis by transient absorption spectrum showed that thymine radical anion was formed at first, and then after several decades of microseconds of pulse radiolysis, the spectrum of thymine radical anion was changed to that of echinocoside radical anion. The evidence indicated that thymine radical anion was repaired through one-electron-transfer between the DNA base radical anion and echinocoside. The rate constant of electron transfer by echinocoside was 1.45 x 10(9) dm(3) . mol(-1). s(?-1).