Abstract

"Berries are among the richest fruits in antioxidant capacity. They are becoming an important and fast growing economic resource for Chile. The FRAP assay, is one of the analytical methods to evaluate the antioxidant capacity of fruits and vegetables. The current experimental protocol has established that an interval of 4 min and a temperature of 37°C would constitute suitable conditions to assay the total antioxidant capacity of most samples. However, the applications of such experimental conditions to samples of berries are not suitable to assess the ""total FeTPTZ-reducing capacity"" contained in these fruits. The objectives of this study were: 1) to establish the adequate experimental conditions to determine the total antioxidant capacity of berries through the FRAP assay, 2) to determine the effect of three different solvent extraction protocols on the FRAP value of samples of berries (70:30 acetone/water, 70:30 ethanol/water and aqueous extraction) and 3) to compare the FRAP values and FRAP reaction kinetics of different berry extracts. Results indicate that: 1) the FRAP value of the samples of berries varies as a function of the time of incubation, 2) blackberries have the highest antioxidant capacity, followed by blueberries, strawberries and raspberries, 3) 70:30 acetone/water extraction resulted in FRAP values higher than 70:30 ethanol/water and aqueous extract and 4) along the 0-250 min of monitoring the Fe-TPTZ reduction, substantially different reaction kinetics could be appreciated as a function of the species and the nature of the extract studied. The large differences in FRAP reaction kinetics are likely to underlie differences in the reactivity of antioxidant molecules present in these berries. It seems important to reevaluate the experimental conditions so far employed to assess the actual FRAP values in samples of these type of fruits."