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Similarities and Differences:
- The improved ORAC versus the original ORAC - The history of ORAC
In 1997, Brunswick Laboratories, replicated the automated method developed by Cao and Prior, and to date, has served more than 200 customers worldwide and has established the world's largest antioxidant database consisting of over 5000 points of ORAC data for fruits, vegetables, beverages, grains, functional/engineered foods, extracts, and other natural product sources. During the course of analyzing a wide variety of samples, some limitations of the ORAC assay were found:
- B-phycoerythrin (B-PE), the protein fluorescent probe of ORAC, was found to interact with polyphenols due to the nonspecific protein binding, causing falsely low ORAC value. In addition, B-PE is photobleached after exposed to the excited light.
- The isolation process of B-PE produces variability from lot-to-lot, causing variable reactivity to peroxyl radicals (Cao, et al 1999).
- The original ORAC assay does not measure "total antioxidant capacity". This assay is performed in aqueous buffer solution, therefore only water-soluble antioxidant can be measured. In addition, the peroxyl radical has been the only radical source used in routine analyses, and other ROS species such as hydroxyl radical, singlet oxygen and peroxynitrite are not measured. Whereas we introduced fluorescein as the new probe in the ORAC assay, we found that fluorescein has the following distinct advantages over B-PE:
- Fluorescein does not interact with the test sample
- Fluorescein is very stable
With the exception of the fluorescent probe, the improved ORAC assay is exactly the same as the original ORAC assay in terms of experimental conditions, AUC technique and chemical principles. However, the ORAC value obtained by the improved ORAC is higher than that obtained by the original ORAC assay. The reason for this is due to the fact that in the improved ORAC reaction, the fluorescent probe is exclusively damaged by the peroxyl radical, and therefore the new assay measures the antioxidant capacity more accurately.
- The ORAC versus other methods
The advantages of the improved ORAC assay over other popular methods have been discussed extensively by Cao (1998) and Ou (2001 and 2002), respectively. General speaking, the ORAC method measures antioxidant chemically and physiologically.
- Difference between total antioxidant capacity assay and individual antioxidant profile
The Brunswick total antioxidant capacity assays are developed to quantify the REACTIVTY of antioxidants regardless of known or unknown compounds. The total antioxidant capacity results do not provide the identity of individual antioxidant compound; While, Our INDIVIDUAL ANTIOXIDANT PROFILE assays are utilized to measure the QUANTITY of individual antioxidant compound, the results do not reflect the actual antioxidant REACTIVITY.
- Relationship between TOTAL ANTIOXIDANT CAPACITY and OXIDATIVE STRESS ASSAYS
Since the antioxidants from dietary sources would be interacting with the free radicals in the body preferably to inhibit the oxidative damage to cell membranes and DNA, the dietary antioxidants theoretically do not alter the antioxidant level in the body, instead they actually decrease the oxidative stress level. The oxidative stress level has to be estimated by the quantity
of oxidized products of lipid, protein and DNA. In general, the higher ORAC values of antioxidant, the lower level of oxidative stress,provided that the given antioxidant possesses relatively high bioavailability. Figure 8 demonstrates the relation between the ORAC assays and the oxidative stress assays.
© Copyright 2003-2006 by
Brunswick Laboratories
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