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| Content Provider | World Health Organization (WHO)-Global Index Medicus |
|---|---|
| Author | Dorta, E. Atala, E. Aspee, A. Speisky, H. Lissi, E. Lopez-Alarcon, C. |
| Description | Country affiliation: Chile Author Affiliation: Dorta E ( Pontificia Universidad Catolica de Chile (Facultad de Quimica), Departamento de Farmacia, Chile.); Atala E ( Pontificia Universidad Catolica de Chile (Facultad de Quimica), Departamento de Farmacia, Chile.); Aspee A ( Universidad de Santiago de Chile (Facultad de Quimica y Biologia), Departamento de Ciencias del Ambiente, Chile.); Speisky H ( Universidad de Chile (Instituto de Nutrición y Tecnología de los Alimentos), Chile.); Lissi E ( Universidad de Santiago de Chile (Facultad de Quimica y Biologia), Departamento de Ciencias del Ambiente, Chile.); Lopez-Alarcon C ( Pontificia Universidad Catolica de Chile (Facultad de Quimica), Departamento de Farmacia, Chile. Electronic address: clopezr@uc.cl.) |
| Abstract | During the last decades the ORAC (Oxygen Radical Absorbance Capacity) assay has been widely employed to evaluate the in vitro antioxidant capacity of polyphenol-rich fruits, vegetables and beverages. The method employs fluorescein (FLH) as target molecule and AAPH (2,2'-azo-bis(2-amidinopropane)dihydrochloride) as the source of peroxyl radicals (ROOâ¢). The protection of FLH, afforded by antioxidants (XH), is often characterized by kinetic profiles with clear lag times (LT), which are directly associated with the stoichiometry (n) of the XH-ROO⢠reaction. However, even for simple phenolic compounds, the LT measured imply large n values (defined as the number of ROO⢠moles trapped by each antioxidant molecule) which cannot be explained by a simple reaction mechanism. Nonetheless, they can be explained when considering the formation of alkoxyl radicals (ROâ¢) from the recombination of two AAPH-derived ROOâ¢. In the present work, we provide kinetic data showing that, in the zero order kinetic limit of FLH consumption, there is a low reaction rate incompatible with total trapping of ROOâ¢. Thus, the consumption of FLH should be mostly related to its reaction with ROâ¢. In addition, we present data regarding the assumption that in competitive measurements, the LT is due to efficient trapping of the ROO⢠by the added phenols, leading to high n values (1.7 to 23) for mono and polyphenols. These values are not in agreement with kinetic studies of the antioxidant consumption mediated by the presence of AAPH carried out by HPLC-DAD technique, which imply a competition by ROâ¢. The results suggest that the use of FLH as probe at low concentrations give, for several antioxidants, ORAC values mainly related to their reaction towards RO⢠radicals instead of primary ROOâ¢radicals. |
| File Format | HTM / HTML |
| ISSN | 08915849 |
| Issue Number | Suppl 1 |
| Journal | Free Radical Biology and Medicine |
| Volume Number | 75 |
| e-ISSN | 18734596 |
| Language | English |
| Publisher | Elsevier |
| Publisher Date | 2014-10-01 |
| Publisher Place | United States |
| Access Restriction | One Nation One Subscription (ONOS) |
| Content Type | Text |
| Resource Type | Article |
| Subject | Physiology (medical) Biochemistry |
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