Optimizing extraction of antioxidant-enriched Dillenia ovata stem bark and evaluating its antidiabetic activities in vitro and in vivo

• Optimal extraction conditions for Dillenia ovata stem bark (DOSB) have been identified. • DOSB extract inhibited key enzymes in diabetic management. • DOSB extract could reduce diabetes and its complications in mice. • Optimized DOSB extract (200 mg/kg) showed greater potency than 400 mg/kg non-optimized. • Betulinaldehyde and betulinic acid were isolated from DOSB for the first time. Our objectives included optimizing extraction of antioxidant-enriched Dillenia ovata stem bark , and testing the antidiabetic effects of optimal extract. This study employed a Box–Behnken design-based statistical model to enhance the extraction of antioxidant-enriched compounds from Dillenia ovata stem bark. In vitro antidiabetic activity was assessed by inhibiting the key enzymes α-amylase and α-glucosidase, and in vivo testing was conducted using an alloxan-induced diabetic mice model. The optimal extraction conditions were 28.43 °C, 25.48 h, 72.80 % ethanol, and a material-to-solvent ratio of 1:10 (w/v). Two compounds, betulinaldehyde and betulinic acid, were isolated for the first time from the ethyl acetate fraction of the optimal DOSB extract. The IC 50 values of the optimal extract against α-amylase and α-glucosidase were 18.64 µg/mL and 10.26 µg/mL, respectively, whereas the two isolated compounds also exhibited considerable inhibitory activities. In vivo , the optimized DOSB extract at a dose of 200 mg/kg BW demonstrated comparable or superior therapeutic effects to the non-optimized extract at 400 mg/kg BW, suggesting improved potency resulting from the optimized extraction process. The DOSB extract reduced blood glucose levels, promoted weight loss, showed antioxidant activity by decreasing malondialdehyde (MDA), increased glutathione (GSH) in liver tissue, restored pancreatic structure, and normalized blood lipid profiles. The study supports the continued use of Dillenia ovata stem bark in diabetes management and encourages conservation efforts to ensure its sustainable use.