TY - JOUR
T1 - 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
AU - Mukai, Kazuo
AU - Ouchi, Aya
AU - Abe, Takumi
AU - Murata, Kazumasa
AU - Nakagawa, Kiyotaka
AU - Miyazawa, Teruo
N1 - Publisher Copyright:
© 2014 American Chemical Society.
PY - 2014/12/10
Y1 - 2014/12/10
N2 - Recently, a new assay method that can quantify the aroxyl radical (ArO•) absorption capacity (ARAC) of antioxidants (AOHs) was proposed. In the present work, the second-order rate constants (ks Extract) and ARAC values for the reaction of ArO• with seven kinds of rice bran extracts 1-7, which contain different concentrations of α-, β-, γ-, and δ-tocopherols and -tocotrienols (α-, β-, γ-, and δ-Tocs and -Toc-3s) and γ-oryzanol, were measured in ethanol at 25 °C using stopped-flow spectrophotometry. The ks Extract value (1.26 × 10-2 M-1 s-1) of Nipponbare (extract 1) with the highest activity was 1.5 times larger than that (8.29 × 10-3) of Milyang-23 (extract 7) with the lowest activity. The concentrations (in mg/100 g) of α-, β-, γ-, and δ-Tocs and -Toc-3s and γ-oryzanol found in the seven extracts 1-7 were determined using HPLC-MS/MS and UV-vis absorption spectroscopy, respectively. From the results, it has been clarified that the ArO•-scavenging rates (ks Extract) (that is, the relative ARAC value) obtained for the seven extracts 1-7 may be approximately explained as the sum of the product {∑ ks AOH-i [AOH-i]/105} of the rate constant (ks AOH-i) and the concentration ([AOH-i]/105) of AOH-i (Tocs, Toc-3s, and γ-oryzanol) included in rice bran extracts. The contribution of γ-oryzanol to the ks Extract value was estimated to be between 3.0-4.7% for each extract. Taken together, these results suggest that the ARAC assay method is applicable to general food extracts.
AB - Recently, a new assay method that can quantify the aroxyl radical (ArO•) absorption capacity (ARAC) of antioxidants (AOHs) was proposed. In the present work, the second-order rate constants (ks Extract) and ARAC values for the reaction of ArO• with seven kinds of rice bran extracts 1-7, which contain different concentrations of α-, β-, γ-, and δ-tocopherols and -tocotrienols (α-, β-, γ-, and δ-Tocs and -Toc-3s) and γ-oryzanol, were measured in ethanol at 25 °C using stopped-flow spectrophotometry. The ks Extract value (1.26 × 10-2 M-1 s-1) of Nipponbare (extract 1) with the highest activity was 1.5 times larger than that (8.29 × 10-3) of Milyang-23 (extract 7) with the lowest activity. The concentrations (in mg/100 g) of α-, β-, γ-, and δ-Tocs and -Toc-3s and γ-oryzanol found in the seven extracts 1-7 were determined using HPLC-MS/MS and UV-vis absorption spectroscopy, respectively. From the results, it has been clarified that the ArO•-scavenging rates (ks Extract) (that is, the relative ARAC value) obtained for the seven extracts 1-7 may be approximately explained as the sum of the product {∑ ks AOH-i [AOH-i]/105} of the rate constant (ks AOH-i) and the concentration ([AOH-i]/105) of AOH-i (Tocs, Toc-3s, and γ-oryzanol) included in rice bran extracts. The contribution of γ-oryzanol to the ks Extract value was estimated to be between 3.0-4.7% for each extract. Taken together, these results suggest that the ARAC assay method is applicable to general food extracts.
KW - ARAC value
KW - antioxidant activity
KW - free radicals
KW - kinetic study
KW - reaction rate
KW - rice bran extract
KW - stopped-flow spectrophotometry
KW - tocopherol
KW - tocotrienol
KW - vitamin E
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U2 - 10.1021/jf503996z
DO - 10.1021/jf503996z
M3 - Article
C2 - 25393029
AN - SCOPUS:84916624267
VL - 62
SP - 11901
EP - 11909
JO - Journal of Agricultural and Food Chemistry
JF - Journal of Agricultural and Food Chemistry
SN - 0021-8561
IS - 49
ER -