Kinetic Study of the Scavenging Reaction of the Aroxyl Radical by Seven Kinds of Rice Bran Extracts in Ethanol Solution. Development of an Aroxyl Radical Absorption Capacity (ARAC) Assay Method
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- 作者：Kazuo Mukai ; Aya Ouchi ; Takumi Abe ; Kazumasa Murata ; Kiyotaka Nakagawa ; Teruo Miyazawa
- 刊名：Journal of Agricultural and Food Chemistry
- 出版年：2014
- 出版时间：December 10, 2014
- 年：2014
- 卷：62
- 期：49
- 页码：11901-11909
- 全文大小：452K
- ISSN：1520-5118
文摘
Recently, a new assay method that can quantify the aroxyl radical (ArO鈥? absorption capacity (ARAC) of antioxidants (AOHs) was proposed. In the present work, the second-order rate constants (ksExtract) and ARAC values for the reaction of ArO鈥?with seven kinds of rice bran extracts 1鈥?, which contain different concentrations of 伪-, 尾-, 纬-, and 未-tocopherols and -tocotrienols (伪-, 尾-, 纬-, and 未-Tocs and -Toc-3s) and 纬-oryzanol, were measured in ethanol at 25 掳C using stopped-flow spectrophotometry. The ksExtract value (1.26 脳 10鈥? M鈥? s鈥?) of Nipponbare (extract 1) with the highest activity was 1.5 times larger than that (8.29 脳 10鈥?) of Milyang-23 (extract 7) with the lowest activity. The concentrations (in mg/100 g) of 伪-, 尾-, 纬-, and 未-Tocs and -Toc-3s and 纬-oryzanol found in the seven extracts 1鈥? were determined using HPLC-MS/MS and UV鈥搗is absorption spectroscopy, respectively. From the results, it has been clarified that the ArO鈥?scavenging rates (ksExtract) (that is, the relative ARAC value) obtained for the seven extracts 1鈥? may be approximately explained as the sum of the product {危 ksAOH-i [AOH-i]/105} of the rate constant (ksAOH-i) and the concentration ([AOH-i]/105) of AOH-i (Tocs, Toc-3s, and 纬-oryzanol) included in rice bran extracts. The contribution of 纬-oryzanol to the ksExtract value was estimated to be between 3.0鈥?.7% for each extract. Taken together, these results suggest that the ARAC assay method is applicable to general food extracts.