The antitumor mechanism of etoposide (VP-16) is investigated using pulse radiolysis technology. The oxidizing mechanism of VP-16 is studied by sodium persulfate, and the reaction rate constant is 4.04× 109 L· mol-1 · s-1. The electron-transfer between VP-16 and tyrosine is observed and the reaction rate constant is 1.1 - 108 L · mol-1· s-1.
Reactions of 4-chlorophenol, and other phenols, with eaq , ?H, ?N3 and ?OH in aqueous solutions were studied - by nano-second pulse radiolysis. The transient absorption spectra were attributed to determine the micro-reaction rate constants. It was found that the phenols were more easily oxidized by ?OH than reduced by eaq ; and pH value - and molecular structure of the phenols affected the rate constants of the reactions. In addition, γ-ray radiolysis of 4-chlorophenol aqueous solution was performed and the degradation products were analyzed with HPLC, GC-MS and other methods. It is concluded that the radiolysis technology alone is not efficient in terms of mineralization of the phenol and the presence of O2 and alkaline conditions can facilitate the mineralization process.
Time-resolved laser flash photolysis and pulse radiolysis have been used to study the chemical activity of podophyllotoxin(PPT) and etoposide(VP-16). The mechanism of photoionization of etoposide and podophyllotoxin has been confirmed and illustrated. It is demonstrated that VP-16 and PPT in aqueous solution can be photoionized at 248 nm to give hydrated electron and neutral radical resulting from rapid deprotonation of radical cation of VP-16 and PPT. The quantum yield for the photoionization of VP-16 and PPT with single-photo is 0.21 and 0.61, respectively. In addition, they can react with hydrated electron, hydrogen radical and hydroxyl radical. This will give chemists some advice on synthesizing new derivatives of podophyllotoxin in cancer treatment.
