Opuntia stricta (Haw.) Fruit Pulp and Seeds as Source of Bioactive Phytochemicals with Promising Functional Properties

In recent years, <i>Opuntia stricta</i> (Cactaceae family) has garnered considerable attention due to its promising nutritional and medicinal properties. This study aims to investigate the chemical composition and bioactivity of Sicilian <i>Opuntia stricta</i> fruit pulp and seeds. Liquid chromatography-mass spectrometry analysis revealed the presence of betalain derivatives, especially isobetanin and betanin, as the main pigments in the freeze-dried pulp and its hydroalcoholic extract. Other constituents, namely, piscidic acid, isorhamnetin-3-<i>O</i>-glucoside, and isorhamnetin-3-<i>O</i>-rutinoside, were identified. Linoleic acid (41.95%) was the main abundant fatty acid followed by palmitic acid (19.32%) in the seed's fixed oil as analyzed by gas chromatography-mass spectrometry. The antioxidant activity was assessed using a multi-target approach using 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power assay (FRAP), and <i>β</i>-carotene bleaching tests. The ABTS test showed greater sensitivity to the action of the samples with significant half-maximal inhibitory concentrations (IC₅₀) of 13.24 and 14.82 mg/mL for the hydroalcoholic extract and the freeze-dried fruit pulp, respectively. <i>Opuntia stricta</i>'s extracts were also assessed for the carbohydrate-hydrolyzing enzyme and lipase inhibitory effect. The freeze-dried fruit pulp exhibited the highest effect against lipase (IC₅₀ of 33.54 μg/mL). Collectively, our results contribute to the characterization of this traditionally consumed Sicilian edible plant and suggest its use as a source of bioactive compounds useful for the prevention of obesity linked to hyperglycemia.