Effect of antioxidant potential in the oxygen radical absorption capacity (ORAC) assay
Bisby, RH, Brooke, R and Navaratnam, S 2008, 'Effect of antioxidant potential in the oxygen radical absorption capacity (ORAC) assay' , Food Chemistry, 108 (3) , pp. 1002-1007.
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The "Oxygen Radical Absorption Capacity” (ORAC) assay (Ou, B., Hampsch-Woodill, M., Prior, R.L. (2001). Development and validation of an improved oxygen radical absorbance capacity assay using ﬂuorescein as the ﬂuorescent probe. Journal of Agricultural and Food Chemistry 49, 4619–4626) is widely employed to determine antioxidant content of foods and uses ﬂuorescein as a probe for oxidation by peroxyl radicals. Kinetic modeling of the ORAC assay suggests that the lag phase for loss of ﬂuorescence results from equilibrium between antioxidant and ﬂuorescein radicals and the value of the equilibrium constant determines the shape of the lag phase. For an eﬃcient antioxidant this constitutes a "repair" reaction for ﬂuoresceinyl radicals and produces a well deﬁned lag phase. The lag phase becomes less marked with increasing oxidation potential of the antioxidant. Pulse radiolysis conﬁrms that ﬂuoresceinyl radicals are rapidly (k 10^9 dm3 mol-1 s-1) reduced by Trolox C, a water soluble vitamin E analogue. ORAC assays of phenols with varying oxidation potentials suggest that it might be employed to obtain an estimate of the redox potential of antioxidants within food materials.
|Uncontrolled Keywords:||Antioxidant, fluorescein, oxygen, radical, ORAC, pulse radiolysis, reduction potential|
|Themes:||Health and Wellbeing|
|Schools:||Schools > School of Environment and Life Sciences > Biomedical Research Centre|
|Journal or Publication Title:||Food Chemistry|
|Depositing User:||RH Bisby|
|Date Deposited:||28 Sep 2011 10:40|
|Last Modified:||03 Jun 2014 08:08|
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