Research On The Quenching Mechanism Of Singlet Oxygen By Resveratrol And Its Dimer

Wine grapes(Vitis vinifera)are rich in stilbene compounds.Stilbenes are a general term for non-flavonoid polyphenol compounds which contain stilbene units.The structure of stilbenes is complex and diverse,and widely distributed in nature.In recent years,as a class of important stilbene compounds,resveratrol and its oligomers have attracted wide attention due to their potential nutritional and health-care value,especially resveratrol dimers have the strong physiological activity of selectively quenching singlet oxygen.Therefore,the purpose of the investigation is to further explore the mechanism of resveratrol and its dimer quenching singlet oxygen,and the main content of this experiment includes the following three aspects.1.The UHPLC-QTOF-MS2 method for identification of resveratrol dimers was established by analyzing the fragmentation pathways of four known resveratrol oligomers trans-E-Viniferin,cis-?-Viniferin,trans-?-Viniferin and(-)-Hopeaphenol.This method could be applied to quickly and easily identify the resveratrol dimer in extract of wine grape.MS/MS experiments on the[M-H]-ions could provide the abundant structural information,especially the relative abundance of the key product ion at m/z 347 could be used to further identify isomers of resveratrol dimers.With the aid of the fragmentation pathways,Gnetin C and cis-Scirpusin A were identified in the crude extract of wine grape.2.Previous studies have illustrated that both resorcinol and carbon-carbon double bond could participate in the reaction of resveratrol dimers quenching singlet oxygen.Up to now,it has not been reported in literature that which structure(resorcinol or carbon-carbon double bonds)plays a more decisive role in stilbenes quenching singlet oxygen.To explore the characteristic structure of quenching singlet oxygen,the activity of resveratrol,pterostilbene and piceatannol quenching singlet oxygen was compared and analyzed by UHPLC-QTOF-MS2 and UHPLC-QQQ-MS2.The results showed that catechol ring,carbon-carbon double bond and resorcinol ring could participate in the reaction of quenching singlet oxygen,and catechol ring was the most important structure in resveratrol and its analogues quenching singlet oxygen,the contribution of the structures in quenching singlet oxygen activity are as follow:catechol ring>carbon-carbon double bond>resorcinol ring,which is supported by the chemical calculation of energy.3.The mechanism of resveratrol dimer(trans-?-Viniferin and trans-?-Viniferin)protecting DNA from singlet oxygen was investigated.The reactants and products of resveratrol dimer protecting guanine from oxidative damage were qualitatively monitored and quantitatively analyzed by UHPLC-QTOF-MS2 and UHPLC-QQQ-MS2,which results verified that two resveratrol dimers could inhibit the oxidative damage of guanine to varying degrees.The reaction mechanism is that resorcinol in resveratrol dimer could react preferentially with singlet oxygen and producing p-benzoquinone,therefore protecting DNA from singlet oxygen damage.In this paper,the UHPLC-QTOF-MS2 method based on fragmentation pathway was used to identified resveratrol dimer in the extract of wine grapes.And the mechanism of resveratrol and its analogues quenching singlet oxygen,resveratrol dimer protecting DNA from oxidative damage were explored by UHPLC-QTOF-MS2 and UHPLC-QQQ-MS2.The results would provide the theoretical basis for the development of grape health food and it is important significantly for the prevention and treatment of singlet oxygen-mediated diseases.