FRAP assay

Ferric Reducing Antioxidant Power (FRAP) Assay... 

Benzie IFF and Strain JJ. 1996. The ferric reducing ability of plasma (FRAP) as a measure of antioxidant power the FRAP assay. Anal Biochem 239(1 ) 70—76. 

Guo C, Yang J, Wei J, Li Y, Xu J and Jiang Y. 2003. Antioxidant activities of peel, pulp and seed fractions of common fruits as determined by FRAP assay. Nutr Res 23(12) 1719-1726. 

Analysis of antioxidant activity by performing a FRAP assay was proposed by Benzie and Strain [23]. It involves colorimetric determination of the reaction mixture in which the oxidants contained in the sample reduce Fe ions to Fe. At low pH, Fe(in)-TPTZ (ferric-tripyridltria-zine) complex is reduced to the ferrous (Fe ) form and intense blue colour at 593 nm can be observed. The FRAP reagent is prepared by mixing 2.5 ml of TPTZ (2,4,6-tris (l-pyridyl)-5-triazine) solution (10 mM in 40mM HCl), 25 ml acetate buffer, pH 3.6, and 2.5 ml FeCl3 H20 (20 mM). The colour of Fe(II)(TPTZ)2 which appears in the solution is measured colorimetri-cally after incubation at 37°C. The measurement results are compared to those of a blank sample, which contains deionised water instead of the analysed sample. The duration of the assay differs from one study to another 4 min [23, 24], 10 min [25] to 15 min [26]. The analysis results are converted and expressed with reference to a standard substance, which can be ascorbic acid [26], FeS04 [23, 25], Trolox [27,18]. 

In ferric reducing/antioxidant power (FRAP) assay reaction of Fe (Ill)-tripiridyltriazine reduction to Fe (Il)-tripiridyltriazine is used. The latter compound is bright blue and its absorption band is 593 nm [49,50],... 

FRAP assay Absorbance of Fe + complex at 593 nm produced by antioxidant reduction of corresponding tripyridyltriazine Fe + complex... 

Cherezov, V., Liu, J., Griffith, M., Hanson, M. A., Stevens, R. C. (2008). LCP-FRAP assay for pre-screening membrane proteins for in meso crystallization. Crystal Growth and Design, 8, 4307—4315. 

Corsican Limbarda crithmoides L. ssp. longifolia (Asteraceae) essential oil was investigated, and it was found to contain 65 constituents, among which the major compounds werep-cymene, a-pinene, thymol-methyl-ether, 2,5-dimethoxy-p-cymenene, 3-methoxy-j9-cymenene, and a-phellandrene. In DPPH and ABTS assays, this essential oil showed positive results. A moderate reducing power of ferric ion was measured with FRAP assay and was attributed to the essential oil (Andreani et al., 2013). 

The Ferric Reducing Antioxidant Power (FRAP) assay uses an electron transfer reaction to assess the reducing ability of a given antioxidant. This colorimetric assay is based on the reduction of an Fe(ni)-tripyridyltriazine (TPTZ) complex to its intensely blue coloured Fe(II) analogue (Schane 4.4) under acidic conditions [11]. 

Scheme 4.4 Mechanistic basis of the FRAP assay reduction of the Fe(III)-TPTZ complex 128 to the Fe(II)-TPTZ complex 129 via an electron transfer reaction...

Fig. 4.5 Dost-respome lines showing concentration-dependence of Fe(II) generation from Fe(III) in the FRAP assay...

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