In Vitro Antidiabetic Activity and Mechanism of Action of Methanolic Extract of Opuntia stricta Cladodes

Type 2 diabetes mellitus (T2DM) is characterized by insulin resistance and β-cell dysfunction, leading to chronic hyperglycemia. Although Opuntia species have demonstrated antidiabetic potential, evidence on the in vitro mechanisms of Opuntia stricta cladodes (OSCs) remains limited. This study investigated the antidiabetic activity and mechanism of action of methanolic extracts of OSC using multiple cell-based assays.

Cladodes were collected in Zambia, shade-dried, powdered, and extracted with methanol. Cytotoxicity and antidiabetic effects were assessed using C3A hepatocytes, L6 myoblasts, Caco-2 epithelial cells, and INS-1 β-cells. Assays included cell viability, glucose utilization, glucose uptake, and β-cell proliferation. Data were analyzed using Student's t-test and one-way ANOVA with Tukey's post hoc test (p < 0.05).

The OSC extract showed good tolerability, with cell viability > 80% across all cell lines. In C3A hepatocytes, glucose utilization increased significantly at 6.25-100 μg/mL (p < 0.001), with the highest effect at 100 μg/mL (90.1% ± 0.3%) compared to untreated (86.3% ± 0.4%). Glucose uptake was also significantly enhanced at 100 μg/mL compared to untreated (51.2% ± 1.0% vs. 43.4% ± 2.5%, p < 0.001) but without a significant difference from insulin (50.2% ± 3.6%, p = 0.984). After 24 h in L6 myoblasts, treatment at 100 μg/mL modestly but significantly increased glucose utilization compared with untreated controls (95.06% ± 0.44% vs. 93.5% ± 0.59%, p < 0.005). Uptake also increased significantly at 100 μg/mL when compared to untreated (53.7% ± 1.7% vs. 48.5% ± 2.6%, p < 0.005) but was not significantly different from insulin (53.7% ± 1.7% vs. 54.3% ± 2.0%, p = 0.999). In Caco-2 cells, glucose uptake decreased compared with untreated controls at 6.25 μg/mL (57.5% ± 4.9% vs. 64.6% ± 3.6%, p < 0.05) and 100 μg/mL (50.8% ± 9.4% vs. 64.6% ± 3.6%, p < 0.001). In INS-1 β-cells, proliferation increased at 125 μg/mL after 24 h compared to untreated (111.8% ± 2.2% vs. 100.0% ± 3.8%, p < 0.001), exceeding 10% fetal bovine serum (FBS) (97.8% ± 4.1%) but declined significantly at 48 and 72 h (p < 0.05).

OSC extracts enhanced glucose utilization and uptake in C3A hepatocytes and L6 myoblasts to levels similar to insulin, reduced intestinal glucose uptake in Caco-2 cells relative to untreated controls, and transiently stimulated β-cell proliferation beyond that of 10% FBS. These findings highlight OSC as a promising source of antidiabetic bioactives, warranting further molecular and in vivo studies.