Theoretical Study On Antioxidant Activity Of Phenosol And Methoxy Derivatives

Piceatannol plays great roles in preventing and controlling some diseases (such as dementia, heart disease and cancer etc) incurred by the excessive free radicals because of its high oxidation activity. Therefore, it is very important to study the reaction mechanisms between the piceatannol and some free radicals. In this thesis, the kinetics mechanisms of piceatannol with OH and its derivatives with OOH were calculated by using the density functional method (DFT).In chapter 1, the source and harm of free radical, the classification, index and mechanism of antioxidant, the properties and research status of phenols and piceatannol are summarized. In chapter 2, Schrodinger equation, density functional thereory (DFT), transition state theory (TST), intrinsic reaction coordinate (IRC), and solvent effect etc theoretical basis and computer methods were introduced. In chapter 3, hydrogen atom transfer, radical adduct formation and single electron transfer of piceatannol and OH free radicals were studied, considering the effect of solvent effect and calculation of rate constant. In chapter 4, the theoretical research of piceatannol methoxy derivatives and OOH free radicals were carried.The main conclusions are summarized as follows:(1) At M05-2X/6-311-H-G(d,p) level, the reaction mechanisms between piceatannol and OH free radical were studied in gas phase, the effect of solvent polarity on the reaction mechanisms were also considered using the polarizable continuum model. The results show that, for hydrogen atom transfer mechanism, the active position is C4’OH with B ring both in the gas and aqueous phase. For radical adduct formation mechanism, OH radical preferred to adduct on Cα, Cβ and C4’. At the temperature of 298K, the total rate constants of hydrogen atom transfer and radical adduct formation are 5.46×1015 and 2.72×1014 L-mor--·s-1, the more favorable channel is hydrogen atom transfer. Furthermore, the results also manifest that there is a negative correlation between the rate constants and temperature.(2) At M05-2X/6-311++G(d,p) level, the reaction mechanisms between piceatannol methoxy derivatives and OOH free radical were studied in gas and aqueous phase. The results show that, R-A5, R-A3A5 derivatives have strong activity and higher solubility. Furthermore, the results also manifest that there is a positive correlation between the rate constants and temperature, the more favorable channel is hydrogen atom transfer.