In order to investigate the charge transfer protection mechanism on DNA and dTMP another hydroxy cinnamic acid derivative-sinapine has been studied. Sinapine also belongs to phenyl substituted unsaturated carboxylic acid and its EA(ε,LEM,o: 1.81 eV) is very close to that of caffeic acid ε,LEMO, : 1.79 eV) but its IP(ε,HOM,o:-11.27 eV) is much lower than that of caffeic acid (ε,HOMO,: -11.74 eV) , therefore in comparision with caffeic acid sinapine exert stronger protection effect on DNA, for example, ESR spectrum from DNA-sinapine with more minor molar ratio of protector to nucleotide of DNA(1:8) than that of DNA-caffeic acid (1:4) revealed the characteristic similar to that from sinapine alone irradiated and recorded at 77 K. After annealing at room temperature the ESR pattern changed into that from sinapine alone with clear baseline demonstrating no trace signal from 5-thymyl radical i. e. stronger protective effect by sinapine.