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A combined experimental–theoretical study of the acid–base behavior of mangiferin: implications for its antioxidant activity

机译:Mangiferin酸碱行为的组合实验理论研究:其抗氧化活性的影响

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Acidity constants of mangiferin (H _(4) MGF) in DMSO/H _(2) O (80%/20%, v/v) were determined by UV-Visible and ~(1) H and ~(13) C NMR spectroscopies. UV-Visible absorption spectra in the 4.2 ≤ pH ≤ 11.7 range were fitted using the computational program SQUAD, for the refining of p K _(a) values, obtaining as results: p K _(a1) = 7.337 ± 0.001, p K _(a2) = 8.936 ± 0.001, and p K _(a3) = 10.297 ± 0.028. The sigmoidal curves of the chemical shifts of ~(1) H and ~(13) C in a similar pH range were fitted using the same model refined by SQUAD for UV-Visible data. The behavior of the chemical shifts as a function of pH allowed us to assign the deprotonation order. A theoretical DFT study has been followed confirming the deprotonation order determined experimentally, as well as a proposed mechanism of antioxidant activity, that considers the fractions of the different species at physiological pH. It was found that mangiferin is an excellent peroxyl radical scavenger in aqueous solution, significantly surpassing the activity of Trolox, which is a well-known antioxidant frequently used as a reference in this context.
机译:Mangiferin(H _(4)MgF)的酸度常数在DMSO / H _(2)O(80%/ 20%,V / V)中通过UV可见和〜(1)H和〜(13)C测定NMR光谱法。使用计算节目队列的4.2≤PH≤11.7范围内的UV可见吸收光谱,用于P _(A)值的精炼,获得结果:Pκ_(a1)= 7.337±0.001,p k _(A2)= 8.936±0.001,Pκ_(A3)= 10.297±0.028。在类似的pH范围内〜(1)H和〜(13)C的化学位移的矩形曲线使用与UV可见数据精制的相同模型配合。作为pH函数的化学变化的行为使我们能够分配去质子化秩序。遵循理论DFT研究,确认通过实验确定的去质子化令,以及提出的抗氧化活性机制,其认为在生理pH下不同物种的级分。发现Mangiferin是水溶液中的优异的过氧基清除剂,显着超过滴油的活性,其是常用于本文中的众所周知的抗氧化剂。

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