应用循环伏安和紫外光谱法研究杨梅酮氧化还原性质及其稳定性.结果表明:在B-R缓冲溶液中玻碳电极上,杨梅酮的氧化还原表现为两步氧化反应和两步还原反应.氧化反应对应于B环4-′OH和C环3-OH的氧化,还原反应对应于C环4位羰基还原为中间体自由基之后再进一步还原生成羟基.以上各步反应均为单电子单质子电极过程.杨梅酮的氧化还原反应与溶液pH关系密切,但其原因来自于去质子化作用,并导致它的抗氧化能力增强,但其最终氧化产物没有电化学活性,并吸附在电极表面,阻碍了电极过程电子传递.在pH 7.45~12.00范围内,杨梅酮也因去质子化作用导致紫外光谱Ⅰ带和Ⅱ带随pH增加,而发生红移,分解作用加剧.同时分解作用还与放置时间有关.
The electrochemical mechanism of redox and stability of myricetin were investigated using cyclic voltammetry and electronic absorption spectra.Two oxidation reactions and two reduction reactions were achieved in B-R buffer solution.The oxidation reactions were both due to oxidation of 4′-OH on ring B and 3-OH on ring C within a one electron one proton process.The reduction reactions both correspond to the transformation of 4-carbonyl group on ring C to intermediate radical,and intermediate radical to hydroxyl group within a one electron one proton process,respectively.The redox of myricetin is pH dependent because of deprotonation,resulting in an increase of the antioxidant ability upon formation of the deprotonated forms.The final oxidation product of myricetin without electroactivity adsorbs on the electrode surface,and blocks transfers of electron.With increase of pH(7.45~12.00),Ⅰand Ⅱ bonds of electronic absorption spectra of myricetin are red-shifted due to the deprotonation and the degradation of myricetin increases.The time of storage affects intensity of degradation of myricetin.
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