Etoposide的氧化还原反应: 脉冲辐解和激光光解研究

首次用脉冲辐解时间分辨方法研究了etoposide(VP16)在水溶液中与N~3^.,(SCN)~2^.^-和e~a~q^-之间发生的单电子氧化还原反应,测定了VP16的阴离子自由基、脱质子中性自由基的特征吸收谱;测得VP16与e~a~q^-,N~3^.,(SCN)~2^.^-的绝对反应速率常数分别为2.7×10^9,3.2×10^9和2.5×10^8dm^3.mol^-^1.s^-^1。研究表明,水溶液中的VP16可为248nm激光光电离,光电离的瞬态产物为阳离子自由基及脱质子中性自由基,并且测定了其酸碱电离的pK值。测得SO~4^.^-自由基单电子氧化VP16的反应速率常数为2.8×10^9dm^3.mol^-^1.s^-^1。

Redox reactions of etoposide in aqueous solution: A pulse radiolysis and laser flash photolysis study

Time-resolved pulse radiolysis has been used to study the reactions of etoposide (VP16) with N~3^., (SCN)~2^.^-, e~a~q^- in aqueous solution. The absorption spectra of reaction products were investigated, and a series of rate constants were determined to be 2. 7×10^9, 3.2×10^9, 2.5×10^8dm^3.mol^-^1.s^-^1 for reactions of e~a~q^-, N~3^., (SCN)~2^.^- with etoposide, respectively. Using laser flash photolysis techniques, it is demonstrated that VP16 in aqueous solution is ionized by 248nm photon to give hydrated electron and neutral radical resulting from rapid deprotonation of radical cation of etoposide. The pK value of VP16 is found to be 10.6, and the rate constants for reaction of VP16 with SO~4^.6- is 2.8× 10^9dm^3.mol^- ^1.s^-^1.