Accuracy and Validity of AREC (Alkoxy Radical Elimination Capacity) Assay in Evaluating the Antioxidant Abilities of Various Biosubstances

作者：Nakajima Akira^*; Yamaguchi Tomoko; Hattori Gen; Sakurai Yasuhiro; Kawamura Masaki; Kawai Kiyoshi; Miyake Yusuke; Kanaori Kenji; Tajima Kunihiko^*

来源：Bulletin of the Chemical Society of Japan, 2017, 90(2): 223-230.

DOI：10.1246/bcsj.20160355

The AREC (alkoxy radical elimination capacity) assay was developed to observe the DMPO (5,5-dimethyl-1-pyrroline N-oxide) spin adducts of free radicals produced by thermal decomposition of AAPH (2,2'-azobis(2,4-amidinopropane)dihydrochloride) using a flow-injection ESR (FI-ESR) system. The gamma(50) value is defined as [DMPO](0)/ID50 = k(S)/k(1), where k(1) is the rate constant of spin-trapping of the alkoxy radical by DMPO, k(S), that of alkoxy radical-elimination by the substrate, and ID50, 50% inhibition of the alkoxy radical by the substrate, and the AREC value is the ratio of gamma(50) value of the substrate to that of Trolox (6-hydroxy-2,5,7,8-tetramethyl-chroman-2-carboxylic acid, TRX). The gamma(50) and AREC values show fairly wide variations and can be determined for most biosubstances. The highest AREC values were observed for sinapic acid, L-glutathione, caffeic acid, and chlorogenic acid, followed by TRX, syringic acid, trans-ferulic acid, and homogentisic acid. Little correlation is observed between the AREC values and the hydroxy and superoxide radical-elimination abilities. The AREC values of 4-hydroxycinnamic acid derivatives (HCAs) are linearly related to the aryloxy radical-elimination abilities, which indicate that the alkoxy radical-elimination by HCAs is mainly caused by hydrogen-atom transfer. The newly defined AREC value is applicable for various biosubstances, and is far superior and a more reliable indicator than the oxygen radical absorption capacity (ORAC) value determined by the ORAC-fluorescein assay. Thus, the AREC value is an excellent indicator to characterize the antioxidant activities of a wide range of biologically important antioxidants present in fruits, vegetables, and beverages.

• 出版日期2017-2