Novel approaches in measuring the antioxidative potential of animal feeds the FRAP and DPPH methods

Two methods were adapted and optimized for evaluating the antioxidative potential of animal feeds. In the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method, the neutralization of the stable radical DPPH circle by antioxidants present in animal feeds was measured. The ferric reducing antioxidant power (FRAP) method was used to measure the reducing capacity of feeds. To optimize both methods regarding to the type of solvent, the time of extraction and the volume of solvent needed, a commercial pig feed was used. Of the different solvents used, methanol showed superior results to chloroform, water, ethanol, acetone and chloroform-methanol (1:1, v/v). The time of extraction was also examined. The antioxidative potential of the extract of a first extraction step did not change with extraction time after 3 h of extraction. The need for a second extraction step was also investigated, but this could be reduced to a wash step. In a last phase, the volume of the extraction solvent was optimized. It seemed that 25 mL of methanol was sufficient to give a repeatable extraction yield from 2 g of feed. Both methods gave reproducible results with a high recovery for the tested feed. Therefore, it can be concluded that using methanol as the extraction solvent, the DPPH and FRAP methods are useful techniques for monitoring the total antioxidative potential of animal feeds. (c) 2006 Society of Chemical Industry.