Phytochemical Characterization, Antioxidant Capacity and Antihyperglycemic Effects of Three Mexican Cultivars of Opuntia ficus-indica: Evidence for the Therapeutic Potential of the San Martín Variety in Type 2 Diabetes

Prickly pear (Opuntia ficus-indica) fruits are recognized as valuable sources of bioactive compounds with potential health-promoting properties. However, the relationship between phytochemical composition and antidiabetic activity among different cultivars remains insufficiently characterized. This study evaluated the chemical composition, antioxidant capacity, and anti-hyperglycemic effects of juices obtained from three Mexican prickly pear cultivars (San Martín, Mandarina, and Vigor). Organic acids, sugars, total phenolic and total flavonoid content, betalains, and antioxidant capacity were determined using chromatographic and spectrophotometric methods. The antihyperglycemic activity of the juices was evaluated in healthy Wistar rats using oral glucose tolerance tests (OGTT), and the antidiabetic potential of the San Martín cultivar was assessed in a neonatal streptozotocin-induced type 2 diabetes (T2D) model. Ascorbic acid, oxalic acid, and malic acid were identified in all cultivars, with ascorbic acid being the predominant organic acid in San Martín and Mandarina cultivars juices. Mandarina cultivar exhibited the highest concentration of total phenolic compounds, whereas San Martín cultivar contained significantly greater levels of flavonoids and betalains. Antioxidant activity assessed by ABTS and FRAP assays confirmed the presence of highly active hydrophilic antioxidant compounds. Among the cultivars evaluated, only Mandarina and San Martín juices significantly attenuated postprandial hyperglycemia in healthy animals. Interestingly, freeze-drying abolished the antihyperglycemic effect of San Martín cultivar juice, suggesting degradation or modification of bioactive constituents during processing. In diabetic rats, sub-chronic administration of fresh San Martín cultivar juice significantly reduced blood glucose levels but failed to restore glucose tolerance. Altogether, these findings demonstrate that San Martín prickly pear cultivar juice represents a promising source of bioactive compounds with antihyperglycemic activity. The observed effects are likely associated with the synergistic action of flavonoids, betalains, phenolic compounds, and ascorbic acid. Further mechanistic studies and clinical investigations are warranted to elucidate the molecular pathways involved and evaluate its potential as a functional food for the management of T2D.