Irradiation of Phenolic Compounds with Ultraviolet Light Causes Release of Hydrated Electrons
Irradiation of Phenolic Compounds with Ultraviolet Light Causes Release of Hydrated Electrons
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DOI：
10.1007/s00723-018-0999-9
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发表时间：
2018-03
影响因子：
1
通讯作者：
Shoko Okazaki;K. Takeshita
中科院分区：
文献类型：
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作者：
Shoko Okazaki;K. Takeshita
酚类化合物被广泛用于许多目的，包括医疗药物、化妆品、食品添加剂和辅助食品，并且经常暴露于太阳的紫外线（UV）。本文研究了由酚类化合物产生的自由基，通过紫外线照射，使用电子顺磁共振（ESR）-自旋捕获技术与5，5-二甲基-1-吡咯啉-N-氧化物（DMPO）。本文研究了对苯二酚、邻苯二酚、间苯二酚、邻苯三酚和没食子酸甲酯等多元酚类化合物在紫外光照射下，DMPO与氢自由基和羟基自由基形成加合物（DMPO-H）的ESR信号。自由基加合物中没有检测到一元酚，如苯酚和对羟基苯甲酸甲酯。DMPO-H信号强度随酚类化合物浓度的增加而增强。当用水合电子的清除剂N_2O代替空气的溶液被辐照时，DMPO-H的信号强度降低。然而，甲酸钠，氢自由基的清除剂，不影响DMPO-H的信号强度。DMPO-H的信号强度随溶液pH的升高而增强。半醌型自由基增加的多元酚在DMPO的情况下，在紫外线照射的解决方案。这些结果表明，水合电子产生的多元酚的紫外线照射，和酚盐离子是负责生产的水合电子。
Phenolic compounds are widely used for a number of purposes, including medical drugs, cosmetics, food additives, and supplementary foods, and are often exposed to the ultraviolet (UV) rays of the sun. We herein examined free radicals produced from phenolic compounds by UV irradiation using an electron paramagnetic resonance (ESR)-spin trapping technique with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). The ESR signals of DMPO adducts of the hydrogen radical (DMPO–H) and hydroxyl radical were detected following the UV irradiation of polyhydric phenols, such as hydroquinone, catechol, resorcinol, pyrogallol, and methyl gallate, in an aqueous solution. Radical adducts were not detected in monohydric phenols, such as phenol and methylparaben. The signal intensity of DMPO–H became stronger as the concentration of phenolic compounds increased. The signal intensity of DMPO–H decreased when the solution in which air was replaced with N2O, a scavenger of hydrated electrons, was irradiated. However, sodium formate, a scavenger of the hydrogen radical, did not affect the signal intensity of DMPO–H. The signal intensity of DMPO–H became stronger as the pH of the solution increased. Semiquinone-type radicals increased following the UV irradiation of solutions of polyhydric phenols in the absence of DMPO. These results indicate that hydrated electrons are generated by the UV irradiation of polyhydric phenols, and that phenoxide ions are responsible for the production of hydrated electrons.