Ferric reducing ability of plasma

Ferric Reducing Ability of Plasma (FRAP) is a method used to measure the antioxidant capacity of an individual's blood plasma. This method is based on the principle that at low pH, a ferric-triipyridyltriazine (Fe^3+-TPTZ) complex can be reduced to the ferrous form, which is blue and can be monitored by measuring the change in absorption at 593 nm.

Overview

The FRAP assay is a simple, inexpensive, and reproducible method for assessing total antioxidant power (TAP). It measures the change in absorbance at 593 nm due to the formation of a blue colored Fe^2+-tripyridyltriazine compound from colorless oxidized Fe^3+ form by the action of electron donating antioxidants.

Methodology

The FRAP assay is performed in acidic buffer (pH 3.6) to maintain the redox potential of the Fe^3+/Fe^2+ couple, which is the driving force for the reduction. The antioxidants in the sample reduce the Fe^3+-TPTZ complex to the blue Fe^2+ form, the concentration of which can be monitored by measuring the absorbance change at 593 nm.

Applications

The FRAP assay is used in clinical biochemistry and food science to measure the antioxidant capacity of biological fluids and food extracts respectively. It is also used in epidemiological studies to investigate the relationship between dietary antioxidant intake and disease.

Limitations

The FRAP assay has some limitations. It does not measure the antioxidant capacity of protein-bound antioxidants, and it is not suitable for measuring the antioxidant capacity of lipophilic antioxidants. Furthermore, the FRAP assay measures the total reducing power and does not distinguish between different types of antioxidants.

See also

• Antioxidant
• Oxidative stress
• Reactive oxygen species