Chinese Herbal Medicine In The Theoretical Study Of Phenols Elimination Of Free Radical Reactions

Free radical theory, which has been firstly proposed since the mid-50s of the 20th century by the famous scholar, Harman, as the most famous aging theory, has been the majority scientific consensus. As the advance of the study of free radicals, people developed and producted a variety of effective antioxidant drugs. However, the research costs of chemical synthesised antioxidant are high, and the side effects of chemical synthesised antioxidant are larger. In recent years, people have found that natural products containing a variety antioxidants with low toxicity and stronger physiological activity, and have begun to develop new antioxidants based on these natural antioxidants. Due to the instability of free radicals, not only the experimental study is demanding conditions, costly, and difficult to carry out a large number of experiments, but it is also very difficult to achieve special conditions similar to the physiological environment. Therefore, the theory research based on the rapid developments of computer becomes the best method to make up for chemical experiments. In this paper, the quantum chemical methods is used, to calculate and analyze the theoretical model, and discuss the theory results and known activity of natural antioxidant, and explain experimental results from the theoretical study.This paper includes the following aspects of study:1. Using BLYP/DND Methods in DMol3 package which based on the density functional theory (DFT), we optimized the structure of polyphenolic compounds, resveratrol, and calculated the single point energy and electronic parameters of the optimized structures. The relationships of the antioxidant activity of Resveratrol with its dissociation energies, the structure and the frontier orbital distribution parameters, and with the spin density, single-electron distribution and geometry parameters of free radicals were discussed. The same theory method was used to simulation the reaction of resveratrol and methyl hydroperoxide free radical, and locates the transition states. Then the activation energies of the reaction were estimated, and the chnages of molecular structure and electronic properties along the reaction process were analyzed. Based on the analysis and discussion above, the dissimilarity of scavenging activity on different hydroxygen in resveratrol was certified.2. With the use of BLYP/DND Methods in DMol3 package which based on the density functional theory (DFT), the geometry of Quercetin and its radicals were optimized and analyzed. Based on the O-H dissociation energy, geometric structure, the electron and the frontier orbital properties, we disscussed the stability of radicals and the dissimilarity of experimental antioxidant activity on different hydroxygen in Quercetin. It was certified that quercetin had high biological activity. Finally, it was put forward that two hydroxyls at B ring participating in the scavenging reaction had some difficulty in transforming to hydroxyl diradicals.3. Using Gaussian 03 packages, we optimized the structure of reactants and products of all the possible cyclohexene catalyzed oxidation reaction process and estimated there energetics parameters, and proved that the proposed reaction could take place and is a thermodynamics favorable reaction. As well, products in every step of the approximate reaction process reported in the literature were optimized and their enegitics parameters were estimated, and it was proved that from the thermodynamic point of view, the approximate reaction process could take place, too;Using Gaussian 03 packages, we calculated the molecular structures in the acylation reaction of Coriaria lactone. According to calculation electronic and structure parameters, the slectivity of tutin and coriatin in the acylation reaction was discussed, respectively.In conclusion, the slectivity of tutin is due to the steric hindrance, but the slectivity of coriatin is due to the intramolecular hydrogen bonds.