藤茶中抗氧化成分--二氢杨梅素在碱性溶液中的自氧化作用机理

Exploring Self-oxidative Mechanism of Dihydromyricetin as An Antioxidant Isolated from Vine Tea in Alkaline Solutions

为了进一步研究具有优异抗氧化能力的天然药物--二氢杨梅素,在碱性溶液中结构不稳定性原因及自氧化作用机制。实验分别采用了HPLC色谱法、1HNMR、13CNMR、ESI-MS及电子顺磁共振(EPR)技术,对二氢杨梅素在不同碱性环境中的行为变化进行研究。实验结果表明,二氢杨梅素分别在相同条件下,不同碱性的缓冲溶液(pH 7.4(PBS)、pH 8.5(Tris-HCl)、pH 9.4(Borax-NaOH))中,室温搅拌,均发现有杨梅素成分生成,并经^1HNMR、^13CNMR和ESI-MS技术进行结构确认。分别向等量的二氢杨梅素不同缓冲溶液(pH 7.4(PBS)、pH 8.5(Tris-HCl)、pH 9.4(Borax-NaOH))中,加入DMPO自由基捕获剂,经电子顺磁共振(EPR)技术,均能检测到DMPO-O^-2·加合物的特征峰存在,且强度不同。相反,在氮气的条件下,其DMPO-O^-2·加合物的特征峰强度大幅度降低。实验结果充分证明了二氢杨梅素在有氧且碱性溶液中,会导致自身分子结构不稳定,而产生超氧阴离子自由基的作用机制。

To further understand cause of instability and self-oxidative mechanism of dihydromyricetin(DMY) as an excellent natural antioxidant in alkaline surroundings.Experiments were carried out to investigated behavioral effect of DMY in varied alkaline solution,and observed by HPLC,1HNMR,13CNMR,ESI-MS and EPR.Firstly,when DMY was transferred to varied alkaline buffer solutions(buffer:PBS,pH 7.4;Tris-HCl,pH 8.5;Borax-NaOH,pH 9.4),respectively,with stirring at room temperature,there was a component,by means of isolation and purification by column chromatography,subsequently,was confirmed to be Myricetin by ^1HNMR,^13CNMR and ESI-MS.Secondly,in mechanism of behavioral effect of dihydromyricetin in alkaline buffer solution,the superoxide anion free radical generated from DMY in air-saturated alkaline buffer solution(buffer:PBS,pH 7.4;Tris-HCl,pH 8.5;Borax-NaOH,pH 9.4),was determined by typical signals of DMPO-O^-2· adduct,using EPR technology.Adversely,when DMY was dissolved in nitrogen-saturated alkaline buffer solution,the intensity of typical signals of DMPO-O^-2· was reduced dramatically.Therefore,relying on above data,it indicated well that DMY in alkaline solution enable to generate reactive oxygen species of superoxide anion free radical.Resultly,it is adequately witnessed that behavioral effect of dihydromyricetin in alkaline solution conforms to self-oxidation process,with generating superoxide anion.