Ferric-bipyridine assay: A novel spectrophotometric method for measurement of antioxidant capacity

Abstract

Measurement of the antioxidant potential using in vitro assays is paramount in the assessment of various food products and nutraceuticals. Researchers always attempt to develop more accurate assays which can be performed in unsophisticated conditions. This novel method, Ferric-Bipyridine reducing capacity of total antioxidants (FBRC) is a very simple, accurate assay performed based on the reduction of Fe (III) to Fe (II) by antioxidants with the formation of a colored complex with bipyridine (Bp) i.e, Fe(II)-Bp. The FBRC method thus developed was assessed under carefully adjusted parameters of oxidant concentration, pH, temperature, solvent, light and time in order to fix the optimum conditions for the assay. The spectrophotometric monitoring of Fe(II)-Bp complex was noted by the formation of an intense pink color at room temperature with absorption maxima at 535 nm, pH 4. The analytical performance of this method was fully validated, and the obtained results were satisfactory. It was successfully applied to measure the total antioxidant capacity of standard compounds such as gallic acid, ascorbic acid and butylated hydroxy toluene (BHT), in addition to some plant extracts and oils. The FBRC method is inexpensive, reproducible and simple to perform. In addition, the antioxidant activity of the tested compounds compared to common reference methods showed that the novel FBRC method is superior to the Ferric reducing antioxidant power (FRAP) with regard to its use of realistic pH and faster kinetics. Thus, the FBRC method is convenient for the estimation of total antioxidant in plants extracts, natural products, essential oils and food stuff.