The number of exchanged electrons per molecule of caffeic acid (CA), chlorogenic acid (CGA), gallic acid (GA), catechin (CTH), epigallocatechin gallate (EGCG), ascorbic acid (AA), dehydroascorbic acid (DHA), and Trolox in DPPH, ABTS, and FC assays. Trolox quinone (Equation (12)) or its degradation products do not react further with ABTS⋅+ or DPPH⋅ as approximately two electrons are exchanged per molecule of Trolox over 180 min. For practically all antioxidants, with the exception of Trolox, the number of exchanged electrons under the most favorable conditions, typically the FC assay, is more than two-fold higher than under the least favorable conditions in the majority of cases, the DPPH assay in MeOH. 933 0 obj <>stream �:�, �?���� �'��e �\i�WiW��HK�(��R�H�v�C����j�a����ya�#��A~pf����y�������U�] For GA, secondary reactions are quantitatively relevant under all conditions analyzed already at the subminute range. A relevant question is whether such reactions can be related to the efficiency of the antioxidants in food matrices and, potentially, in vivo where antioxidants are enzymatically and nonenzymatically modified. There are three categories of antioxidant species: enzyme systems (GSH reductase, catalase, peroxidase, etc. 1999, 26, 1231-1237, "Withdrawn: Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods, Release 2 (2010)", https://en.wikipedia.org/w/index.php?title=Trolox&oldid=983511211, Articles with changed ChemSpider identifier, Pages using collapsible list with both background and text-align in titlestyle, Articles containing unverified chemical infoboxes, Creative Commons Attribution-ShareAlike License, This page was last edited on 14 October 2020, at 17:18. NF kappaB p65 (pS536 + Total) ELISA Kit (ab176663). ORAC represent a hydrogen atom transfer (HAT) reaction mechanism, which is most relevant to human biology. Oxygen radical absorbance capacity (ORAC) used to be an alternative measurement, but the United States Department of Agriculture (USDA) withdrew these ratings in 2012 as biologically invalid, stating that "The data for antioxidant capacity of foods generated by in vitro (test-tube) methods cannot be extrapolated to in vivo (human) effects and the clinical trials to test benefits of dietary antioxidants have produced mixed results. In the FC assay, Trolox exchanged 2.25 electrons. A weak positive correlation between GA and its derivative, EGCG, could be attributed to the similar chemical structure. 0000028663 00000 n 0000006612 00000 n There are serious and justified concerns about the current practice that assays with radicals are allowed to proceed for long reaction periods . We know now that antioxidant molecules in food have a wide range of functions, many of which are unrelated to the ability to absorb free radicals" , 6-Hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid, InChI=1S/C14H18O4/c1-7-8(2)12-10(9(3)11(7)15)5-6-14(4,18-12)13(16)17/h15H,5-6H2,1-4H3,(H,16,17), Except where otherwise noted, data are given for materials in their, R.; Pellegrini, N.; Pannala, A.; Yang, M.; Rice-Evans, C. Antioxidant activity applying an improved ABTS radical cation decolorization assay.
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