Identification of free radical species derived from caffeic acid and related polyphenols
Identification of free radical species derived from caffeic acid and related polyphenols
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DOI：
10.1080/10715760600943892
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发表时间：
2007-01-01
影响因子：
3.3
通讯作者：
Sakurai, Hiromu
中科院分区：
文献类型：
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作者：
Maegawa, Yuka;Sugino, Keiji;Sakurai, Hiromu
多酚类物质广泛存在于各种水果、蔬菜和调味品中。众所周知，由于其抗氧化活性，它们具有多种生理作用。它们的活性取决于有利于形成相应稳定自由基的结构特征。在检验多酚自由基稳定的pH值时，我们证实多酚自由基稳定在NaHCO 3/Na 2CO 3缓冲液（pH 10）中，而不是在生理pH区域中。然后，我们测量了电子自旋共振（ESR）光谱在pH 10的自由基物种的特点，研究来自咖啡酸（CA）与不饱和侧链，二氢咖啡酸（DCA）与饱和侧链，绿原酸（ChA）和迷迭香酸（RA）。在自由基结构分析中，进行了ESR模拟、宏观和微观酸离解常数的测定和分子轨道（MO）计算。在CA中，单酚盐形式被认为参与自由基物种的形成，而在DCA中，二酚形式和单酚盐形式被认为有助于自由基物种的形成。在此基础上，我们提出了多酚在碱性条件下形成的自由基物种的可能结构。
Polyphenols are widely distributed in various fruits, vegetables and seasonings. It is well known that they have several physiological effects due to their antioxidative activities. Their activities depend on structural characteristics that favour the formation of their corresponding stable radicals. During the examination at which pH values, the polyphenol radicals are stabilized, we confirmed that polyphenol radicals were stabilized in NaHCO3/Na2CO3 buffer (pH 10) rather than in physiological pH region. Then, we measured electron spin resonance (ESR) spectra at pH 10 to examine the characteristics of free radical species derived from caffeic acid (CA) with an unsaturated side chain, dihydrocaffeic acid (DCA) with a saturated side chain, chlorogenic acid (ChA) and rosmarinic acid (RA). In analyzing the radical structures, ESR simulation, determinations of macroscopic and microscopic acid dissociation constants and molecular orbital (MO) calculation were performed. In CA, the monophenolate forms were assumed to participate in the formation of free radical species, while in DCA, the diphenol form and the monophenolate forms were presumed to contribute to the formation of free radical species. On the basis of the results, we propose the possible structures of the free radical species formed from polyphenols under alkaline conditions.