Reaction of hydroxyl radical with phenylpropanoid glycoside and its derivatives by pulse radiolysis

The reaction of hydroxyl radical with 1 phenylpropanoid glycoside (PPG), cistanoside C, and its 3 derivatives: 1-0-β-D-2-(p-hydroxyphenyl)-ethanyl-glucose, 6-O-(E)-femloyl-glucose and 6-O-(E)-p-hydroxy-cinnarnoylglucose isolated from folk medicinal herbs was investigated by pulse radiolysis technique respectively. The reaction rate constants were determined by analysis of built-up trace of absorption at λmax of specific transient absorption spectra of PPG and its derivatives upon attacking · OH. All four compounds react with · OH at close to diffusion controlled rate (1. 03 × 109-19.139 × 109 L · mol 1 · s 1), suggesting that they are effective · OH scavengers. The results demonstrated that the numbers of phenolic hydroxyl groups of PPG and its derivatives are directly related to their scavenging activities. By comparing the reaction rates of · OH with 1-O-β-D-2-(p-hydroxyphenyl)-ethanyl-glucose, 6-O-(E)-feruloyl-glucose or 6-O-(E)-p-hydroxy-cinnomoyl-glucose, it is evident that the phenylethyl group is more impofiant than phenylacryloyl group for scavenging · OH. Project supported partly by the National Natural Science Foundation of China, the Doctoral Programme of the Minister of Ed-ucation of China, the China Postdoctoral Sciences Foundation, and the Laboratory of Radiation Chemistry, Chinese Academy of Sciences.