Hydroxyl Radicals Damage Dna And Rna Bases, Flavonoids Clean Up The Topology Of The Quantum Chemical Study Of The Hydroxyl Radical Reaction Mechanism And Electron Density Analysis

This dissertation contains three parts.The first part is the theoretical study of the Purine and Pyrimidine react with hydroxyl radical.The second and the third parts are the quantum study of the free radical scavenging capacity of bioflavoinoids(B ring and A ring).The additional mechanism of Purine and Pyrimidine react with hydroxyl radical has been theoretically studied by DFT B3LYP/6-31G in the first part of the dissertation.The results show that Guanine,Adenosine,Cytosine and Thymine all can react with hydroxyl radical.The topological study of transition states and IRC results show that the hydroxyl radical added to the ring structure of Purine and Pyrimidine as the reaction carry out.The activation energy of Purine react with hydroxyl radical is between 32～35kJ/mol,higher than that of Pyrimidine(11～15kJ/mol).In addition,the abstraction hydrogen Mechanism of Thymine and Uracil(the base Included in the RNA) has been studied,and the topological study of the transiton state has also been carded out of them.The hydroxyl radical snatch the hydrogen atom of Thymine and Uracil,formimg a 6-membered-ring structure.The mechanism of hydroxyl free radical scavenging of flavoinoids compounds (B ring) has been theoretical studied under the DFT B3LYP/6-31g.The IRC also has been carried under the same theory.The results show that the phenolic hydroxyl of flavoinoids(B ring) reacts with hydroxyl radical to produce H₂O and Quinone-type radical which is more stable.The hydroxyl free radical close to the flavoinoids(B ring) from one side of the molecular.The dihedral angel of B ring and A,C ring becomes smaller during the reaction process.The activation energy of B ring elementary reaction is between 16～20kJ/mol.The mechanism of hydroxyl free radical,scavenging of flavoinoids compounds (A ring) has been theoretical studied under the DFT B3LYP/6-31 g.The IRC also has been carded under the same theory.The results show that the phenolic hydroxyl of flavoinoids(A ring) reacts with hydroxyl radical to produce H₂O and Quinone-type radical which is more stable.The hydroxyl free radical close to the bioflavoinoids(A ring) from one side of the molecular.The dihedral angel of A,C ring and B ring becomes larger during the reaction process for most of the reaction. The activation energy of B ring elementary reaction is between 14～19kJ/mol.The AIM analysis show that there is no weak interaction between oxygen of hydroxyl free radical and the hydrogen of flavoinoids which is adjacent to the phenolic hydroxyl which is losing hydrogen in the reaction,except naringonin in B ring reaction.But for A ring reaction,except fisotin,there is weak interaction and a six membered ring in the reaction area,which is mentioned above.