青蒿素与DNA作用的电化学机理

Electrochemical Study on Interaction Between Artemisinin and DNA

在体积分数为20%乙醇的Britton-Robinson缓冲溶液(pH=7.4)中,利用循环伏安法和紫外可见吸收光谱法研究了青蒿素与DNA的相互作用。电化学研究表明,DNA的存在能导致青蒿素在银电极上-0.672 V处的还原峰电流下降,峰电位正移。通过对比双链DNA(dsDNA)和单链(ssDNA)与青蒿素作用,得出青蒿素可嵌插到DNA分子中,形成非电活性的复合物。电化学方法可计算出DNA与青蒿素的结合比为1∶4,结合常数为3.6×104。电极过程的电化学参数表明,DNA作用前后,α、β值变化不明显,进一步证实了该复合物是非电活性;Ks值变小,表明二者作用后受扩散控制。紫外可见吸收光谱法研究表明,青蒿素对DNA分子发生嵌插作用。通过光谱滴定法可计算二者的结合比和结合常数,同样获得1个DNA结合4个青蒿素分子,结合常数为4.0×104,与电化学方法测定结果相吻合。实验数据显示,青蒿素进入细胞内有可能与细胞核中DNA结合,诱导细胞凋亡。

The interaction between artemisinin and DNA was studied by cyclic voltammetry and UV-Vis spectroscopy in a Britton-Robinson buffer solution （ pH = 7. 4） containing 20% ethanol. The results would be helpful to understanding the antitumor mechanism of artemisinin and its derivatives. The electrochemical results show that the reduction peak current of artemisinin at a potential of - 0. 672 V at sliver electrode decreased and the peak potential shifted positively with adding DNA in artemisinin solution. The comparison of the interactions of dsDNA and ssDNA with artemisinin indicates that artemisinin reacted with DNA in a mode of intercalation to form an electrochemically inactive complex. The calculation via electrochemical method shows that the ratio of DNA： artemisinin was 1：4 and the combination constant was 3.6 × 10^4. The determination of electrochemical parameters （α,β and Ks ） in the absence and the presence of DNA also shows that an electrochemically inactive complex was formed and the reaction was controlled by a diffusion-controlled electrode process. UV-Vis spectroscopic studies further confirmed the intercalation between artemisinin and DNA. The experiments of spectroscopic titration indicated that one DNA molecule combined with four artemisinin molecules and the binding constant reached 4. 0 × 10^4, which was similar to the result from electrochemical method. These results show that artemisinin might combine with the DNA of nucleus which induced the apoptosis of the cells when it entered into them.