Comparative Analysis of Antioxidant Potency and Phenolic Compounds in Fruit Peel of Opuntia robusta, Opuntia dillenii, and Opuntia ficus-indica Using HPLC-DAD Profiling

The edible part of the prickly pear fruit is most commonly consumed, while the peel is often discarded, leading to the loss of valuable bioactive components, such as phenolic compounds. This research aims to assess the antioxidant activity, total phenolic content, and quantities of phenolic and flavonoid contents of fruit peel of Opuntia ficus-indica, Opuntia robusta, and Opuntia dillenii. Ten phenolic compounds were identified, with isorhamnetin being the most abundant flavonoid measuring 7184.09 mu g/g, while sinapic acid was identified as the major phenolic acid measuring 1806.36 mu g/g. Opuntia robusta exhibited the highest total phenolic content, total flavonoids, and total phenolic acids measuring 5583.19 mg GAE 100 g(-1), 21041.03 mu g/g, and 3265.17 mu g/g, respectively. Opuntia robusta and Opuntia dillenii demonstrated the higher antioxidant capacity in scavenging 2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) compared to Opuntia ficus-indica, whereas Opuntia dillenii and Opuntia ficus-indica exhibited the highest concentration of antioxidants capable of reducing the Fe3+ complex of ferric ions (TPTZ)(3+) to the ferrous complex Fe (TPTZ)(2+). In contrast, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and total antioxidant capacity (TAC) assays showed no significant difference between the examined species. Compared to the local species Opuntia ficus-indica, the two newly introduced Dactylopius opuntiae-resistant species are richer in phenolic compounds and exhibit greater antioxidant activity.