i have prepare linear curve of 2.5micrmolar FeSO4 to 20 micrmolar FeSO4...also i have taken absorbance of standard Ascorbic acid and my extract at different concentration ....Then how to calculate FRAP activity?
Dear Vikas,
I have copied the experimental section of FRAP assay from a publication entitled " ANTIOXIDANT ACTIVITY OF ETHANOLIC EXTRACT OF Maranta arundinacea .L TUBEROUS RHIZOMES" Published in Asian Journal of Pharmaceutical and Clinical Research Vol 5, Issue 4, 2012 (for full paper see attached file) for quick view. You should make a curve such as that illustrated in Figure 6 of the paper.
THERE IS NO CALCULATIONS TO BE DONE. ONLY TO SHOW GRAPHICALLY THE EFFECT COMPARED TO STANDARD.
http://www.ajpcr.com/Vol5Issue4/1256.pdf
FRAP Assay
Frap assay measures the reducing potential of an antioxidant reacting with a ferric tripyridyltriazine [Fe3+-TPTZ] complex and producing a coloured ferrous tripyridyltriazine [Fe2+-TPTZ]11. Generally, the reducing properties are associated with the presence of compounds which exert their action by breaking the free radical chain by donating a hydrogen atom26.Frap assay treats the antioxidants in the sample as a reductant in a redox-linked colorimetric reaction27. In the present study, the trend for ferric ion reducing activities of M.arundinacea and BHT are shown in Fig 6. The absorbance of M.arundinacea clearly increased, due to the
formation of the Fe2+-TPTZ complex with increasing concentration. The water and ethanol extracts of sumac (Rhus.coriaria L.) showed increased ferric reducing power with the increased concentration as standard antioxidants28. Hence they should be able to donate electrons to free radicals stable in the actual biological and food system.
Fig 6:FRAP Assay
The ethanolic extract of M.arundinacea was found to be an effective scavenger of ABTS, DPPH, H2O2, and NO and also possessed a good reducing power and Frap activity. Earlier reports on the antioxidant activity of M.arundinacea are very rare in the literature. Therefore, it is very difficult to compare our results with that of previous studies. The high antioxidant activity of M.arundinaacea enhanced the potential interest in these under-exploited tubers for improving the efficacy of different products as nutraceutical and pharmacological agents. The consumption of the arrowroot may play a role in preventing human diseases in which free radicals are involved, such as cancer, cardiovascular disease, and aging. We conclude that, the results presented indicate that M.arundinacea extract attenuated oxidative stress via its antioxidant properties. However, further investigations on phenols, flavonoids, active principle, their in vivo antioxidant activity, and the different
antioxidant mechanism are warranted.
Hoping this will be helpful,
Rafik
I fully concur with Rafik. Maybe include vitamin C as a comparison which allows you give results as vitamin C equivalents
You may put direct graph for the result or alternatively you can calculate the IC50 value.
https://www.researchgate.net/post/How_do_we_calculate_the_IC_50_value_in_antioxidant_assays
https://www.researchgate.net/post/How_do_I_calculate_DPPH_assay_IC50
Mr. Vikas
I'd rather use gallic acid or ascorbic acid as a standard and express the results as equivalents of these reducing substances with all measurements made under the same conditions of acidity, temperature, iron (III) chloride concentration and hexacyanoferrate (III) concentration. It is also better to run all of the samples and standards together after at least 30 min of color development. Afterwards, you get IC50 from equation and graph as usual.
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