Antioxidant Assays

We have seen from the aritcle "Anthocyanin antioxidants from edible fruits" that the method called DPPH free radical-scavenging assay was used to test the antioxidant activity. It was the method to dtermine IC50 value, which is defined as the total antioxidant necessary to decrease the initial DPPH radical concentration by 50%.

My article for the assignment 2 also tested the antioxidant capacity in foods. However, the paper provided three antioxidant assays instead of one. The first new assay is called beta-carotene bleaching assay. In this assay, beta-carotene and the food extract were mixed first. The presence of antioxidants in the food will inhibit the oxidation of beta-carotene by hydroperoxides. Thus, the degradation rate of beta-carotene depends on the antioxidant activity of the food.

The other assay is called Ferric reducing/amtopxodant power (FRAP) assay. Basically, FRAP assay measures the reducing potential of an antioxidant reacting with a ferric tripyridyltriazine (Fe3+TPTZ) complex and producing a blue colored ferrous tripyridyltriazine (Fe2+TPTZ). The FRAP reagent can be prepared by mixing acetate buffer, TPTZ, and FeCl3 6H2O. The reducing properties are associated with the presence of compounds, which exert their action by breaking the free radical chain through donating a hydrogen atom.

I felt the article with three different assay was much more convincing than the article that we have read. Experiments can be improved with more methods and more trials.

http://www.worldcocoafoundation.org/info-center/document-research-center/documents/Othman2007.pdf