Evaluation of Anti-Diabetic and Antioxidant Potential of Vernonia auriculifera Bark Extract in Streptozotocin-Induced Diabetic Wistar Rats

Background: Diabetes mellitus is a condition characterised by elevated blood glucose levels and oxidative stress, leading to various complications. Medicinal plants represent an important but under utilised source of antidiabetic and antioxidant phytochemical compounds. Objective: This study evaluated the phytochemical composition, in vitro antioxidant activities, and in vivo antidiabetic potential of Vernonia auriculifera Hiern bark extract in streptozotocin-induced diabetic Wistar rats. Methods: The methanolic, ethanolic, and aqueous extracts of the bark were subjected to phytochemical screening. Antioxidant properties were evaluated in vitro by measuring the ferric reducing power (FRAP) and scavenging effect against hydrogen peroxide (H₂O₂). Twenty-five male albino Wistar rats were randomly assigned to five groups: normal control, diabetic control, diabetic treated with 200 mg/kg extract, diabetic treated with 400 mg/kg extract, and diabetic treated with 100 mg/kg metformin. Extracts and metformin were orally administered for 21 days. Results: Phytochemical screening revealed the presence of flavonoids, alkaloids, tannins, glycosides, terpenoids, saponins, and anthraquinones in the methanol extract. The methanol extract showed maximum antioxidant potential, with H₂O₂ scavenging activity at 60 μg/mL (85%), comparable to ascorbic acid. In vivo, the 400 mg/kg dose significantly reduced blood glucose in diabetic animals from 280 to 97 mg/dL (P < 0.01), outperforming metformin (111 mg/dL). Treatment also significantly decreased malondialdehyde (MDA) concentrations and improved the lipid profile. The 200 mg/kg dose produced greater reductions in liver enzyme activities (GGT, ALT, ALP). However, elevated AST at 400 mg/kg, higher triglycerides at 200 mg/kg, and elevated urea at 400 mg/kg indicate dose-dependent safety concerns that require further investigation. Conclusion: Vernonia auriculifera bark extract, particularly at 400 mg/kg, demonstrates significant antidiabetic and antioxidant activities in streptozotocin-induced diabetic Wistar rats.