Gastrointestinal digestion modulates antioxidant and antidiabetic properties of Opuntia ficus-indica pulp and peel

Abstract

This study evaluated the effects of simulated gastrointestinal digestion on the antioxidant and antidiabetic properties of Opuntia ficus-indica (cactus pear) pulp and peel. The increasing prevalence of type 2 diabetes has intensified interest in plant-based functional ingredients; however, the stability and bioaccessibility of bioactive compounds following digestion remain insufficiently characterised. A standardised in vitro digestion model comprising oral, gastric, and intestinal phases was used to assess changes in total phenolic content (TPC), antioxidant activity, and antidiabetic potential. Phytochemical profiles and compound bioaccessibility were further characterised using LC–MS analysis. The peel exhibited significantly higher TPC (1080.04 ± 6.01 mg GAE/g DW) than the pulp (563.92 ± 12.24 mg GAE/g DW) (p < 0.001). Simulated digestion reduced antioxidant activity, with DPPH radical scavenging decreasing by approximately 40%. Intestinal-phase extracts retained measurable inhibitory activity against α-glucosidase (1707.14 ± 7.37 µg/mL) and moderate α-amylase inhibition (756.67 ± 174.48 µg/mL), with the peel generally more potent than pulp. LC–MS analysis indicated that digestion enhanced the bioaccessibility of selected phytochemicals. The peel demonstrated greater compound stability, with citric acid (84%) and piscidic acid (81%) remaining highly bioaccessible (p < 0.001). Conversely, dihydrocaffeoylquinic acid exhibited low bioaccessibility in both peel (27%) and pulp (0%), indicating high susceptibility to digestive conditions. These findings demonstrate that gastrointestinal digestion significantly influences the stability, bioaccessibility, and biological activity of O. ficus-indica phytochemicals. The peel warrants further investigation as a potential source of carbohydrate-digesting enzyme inhibitors for nutraceutical applications.