Cactus pear antioxidants: a comparison between fruit pulp, fruit peel, fruit seeds and cladodes of eight different cactus pear cultivars (Opuntia ficus-indica and Opuntia robusta)

The cactus pear plant is an under-valued food source with health-promoting properties that thrives in arid and semi-arid regions due to its efficient use of water. Eight South African cultivars from two Opuntia species were investigated for their antioxidant content and potential. The fresh fruit (pulp), peel, seeds and cladodes of each cultivar were compared in the study. Analysis included betalains, ascorbic acid, phenolics and carotenoids. The activity of the antioxidants were determined by using the DPPH method and by measuring the chelating activity of ferrous ions. When % DPPH was tested, peel and cladodes were consistently the highest, while in the % chelating activity tests, fruit pulp and seeds were the best tissue types. Cladodes contained more phenolics and carotenes than fruit regardless of the cultivar. For pulp and peel, the cultivar that contained the highest antioxidant content and potential was Robusta with its high content of betalains followed by Gymno-Carpo and Ofer with high ascorbic acid levels. The study proves that the fruit (pulp), peel and seeds from different cultivars contain specific antioxidants relating to the colour of the fruit, but the cladodes of any cultivar contain similar and highly effective antioxidants.