REPAIR EFFECT OF THYMINE RADICAL-ANION BY ECHINOCOSIDE USING PULSE-RADIOLYSIS

Repair activities of thymine radical anion by echinocoside, isolated f rom Pedicularis plicata, were studied using pulse radiolysis technique . The thymine radical anion was produced by the reaction of hydrated e lectron with thymine. Echinocoside, one of the polyphenols of phenylpr opanoid glycoside, was added to the thymine aqueous solution saturated with N-2. Kinetic analysis by transient absorption spectrum showed th at thymine radical anion was formed at first, and then after several d ecades of microseconds of pulse radiolysis, the spectrum of thymine ra dical anion was changed to that of echinocoside radical anion. The evi dence indicated that thymine radical anion was repaired through one-el ectron-transfer between the DNA base radical anion and echinocoside. T he rate constant of electron transfer by echinocoside was 1.45 x 10(9) dm(3) . mol(-1). s(?-1).