Effect of phenolic compounds and betalain pigments on the antioxidant capacity of Moroccan prickly pear juices

Juices of nine prickly pears cultivars ( Opuntia ficus-indica L.) were characterized in terms of phenolics and beta lains pigment content. The antioxidant activity of juice was tested by means o f two different methods: the 2,2-diphenyl-1 picrylh ydrazyl (DPPH) methods, and the 2,2azinobis(3-ethyl-benzothiazoline-6-sulfonic acid) ( ABTS) methods. Juices contained total phenolics ranging from 354.37 to 643.66 µg gallic acid eq/g, betaxanthins (15.84 to 51.33 mg i ndicaxanthin/l), betacyanins (52.04 mg betanin/l fo r red juice) and antioxidant capacity (DPPH) ranging from 52.48 to 135.96µg/ml respectively. The total phenolic contents were highly correla ted with ABTS (R 2 = 0.868) and DPPH (R 2 = 0.959) values. The phenolics compounds contribute more significantly to the total antioxidant capac ity than betalain pigments. Therefore, the total phenolic contents can serve as a useful indicator for the antioxidant activities of prickly pear juices.