Research On The Mechanism Of Resveratrol And Its Dimers To Quench Singlet Oxygen And Protect DNA From Oxidative Damage

The red wine(Vitis vinifera)contained a large amount of stilbenes,Resveratrol,in particular,has been shown to be a selective quencher for singlet oxygen(1O2).However,due to the complex molecular structure of these compounds,only a few researchers have explored the mechanism of resveratrol quenching singlet oxygen.Hence,the ability to quench singlet oxygen1O2with IC50 of Resveratrol and its three dimers,Trans-?-viniferin,Trans-?-viniferin and Scirpusin A were determined by electron spin resonance spectroscopy(EPR),and their values were 45 ?mol/L,5?mol/L,20 ?mol/L and 17 ?mol/L respectively.Therefore,in the first part of the study,the mechanism of quenching singlet oxygen of resveratrol dimer isomers and analogues were systematically and comprehensively explored by combining UHPLC with accurate MS.I:Resorcinol ring exists in stilbenes.The photochemical products were 14Da or 16Da higher than reagents and underwent an endoperoxide intermedate to quinones;II:[2+2]cyclization of intra-molecular trans-double bond.The products were 18Da greater than substrates thereby cycloaddited to oxygen heterocyclic;?;[4+1],[4+2]cyclization of oxetane formed products were 28Da and 44Da higher than Trans-?-viniferin,Trans-?-viniferin,Scirpusin A.?:5-phenol-2,3-dihydrobenzofuran ring exists in Trans-?-viniferin been oxidized,causing the products at 16Da,32Da higher than Trans-?-viniferin.Based on the above quenching mechanism of singlet oxygen for each functional group,the present study also revealed the general mechanism of quenching 1O2 by stilbenes.On this basis,the second part of this study was to explore the mechanism of resveratrol prevented DNA from 1O2 oxidative damage.DNA could be oxidized by 1O2 resulting in irreparable functional damage,and a large number of studies have shown that guanine was the most oxidizable base.Therefore,agarose gel electrophoresis assay demonstrated that DNA was damaged by 1O2 under 5 minutes UVA irradiation and 5 mmol/L resveratrol dissolved in MeOH could relieve the oxidation stress.Additionally,Ultra-High Performance Liquid Chromatography Coupled with Accurate Mass Spectrometry was performed to reveal the mechanism.Four guanine oxidation products at m/z 140.0334[M-H]-1,DGh,8-oxoG and Sp,and two conjugates at m/z 377.1104[M-H]-and 391.0907[M-H]-were found.Ultra-High Performance Liquid Chromatography Coupled with Mass Spectrometry identified the reduction of guanine oxidation products after resveratrol inhibited oxidation.Thus,we proposed the mechanism that phenol ring of resveratrol linked with the free amino groups(-NH)of guanine at the beginning of 1O2 attacking to form m/z 377.1104[M-H]-,however,as 1O2 attacking continuously,resveratrol could efficiently react with 1O2 first to achieve the protection of guanine.In sum up,the mechanism of quenching 1O2 by stilbenes was explored.The further application of resveratrol showed that it could protect DNA against oxidative damage and reveal the cause of protective effect.Phenolic ring in the class of compounds was the priority functional groups of the molecular structure to quench singlet oxygen.This research also laid a theoretical foundation for the subsequent in vivo study of stilbenes.