大黄素的极谱行为及应用研究

在H₃BO₃-Na₂B₄O₇(pH8.5)底液中,大黄素在单扫示波极谱仪上于-0.75V(vs.SCE)左右有一灵敏的二阶导数峰,峰电流与浓度在1.42×10^-7～5.7×10^-6mol·L^-1和7.1×10^-6～7.1×10^-5mol·L^-1范围内呈良好的线性关系,检测限为0.7×10^-7mol·L^-1。本法操作简便、快速、灵敏、选择性好,应用于中药大黄中大黄素的测定,结果良好。本文还研究了大黄素的极谱行为及电极反应机理,并用电化学方法讨论了大黄素、大黄酸、大黄酚、大黄素甲醚和芦荟大黄素清除由邻苯三酚自氧化产生的超氧自由基(O^·-₂)的作用。

INVESTIGATION ON ELECTROCHEMICAL BEHAVIOR OF EMODIN AND ITS APPLICATION

Emodin showed a second-order derivative reduction wave with peak potential of -0.75 V (SCE) by single sweep oscillopolarography using H3BO3-Na2B4O7 (pH 8.50) as base solution. The peak height of emodin is proportional to the concentration in the range of 1.42 x 10(-7)-5.7 x 10(-6) mol.L-1 and 7.1 x 10(-6)-7.1 x 10(-5) mol.L-1, respectively. The detection limit is 0.7 x 10(-7) mol.L-1. It can be employed for the determination of emodin in Rheum officinale Baill with satisfaction. The electrochemical behavior of emodin was studied and the electrode reaction mechanism was proposed. In addition, it was found that emodin, aloe-emodin, chrysophanol, rhein and physcion can scavenge superoxide anion radical produced by the autoxidation of pyrogallol. The scavenging activity is in the order: emodin > aloe-emodin > chrysophanol > rhein > physcion.