Antidiabetic and antioxidant potential of powder blend of Vigna subterranea, Curcuma longa, and Piper nigrum in streptozotocin-induced rats

Abstract

Background: Diabetes mellitus is a chronic metabolic disorder characterized by persistent hyperglycemia and frequently associated with oxidative stress and metabolic complications. The present study evaluated the antidiabetic and antioxidant potential of a powder blend composed of Vigna subterranea, Curcuma longa, and Piper nigrum in streptozotocin-induced diabetic rats. Methods: A mixture design approach was used to optimize the formulation of the powder blend based on total phenolic content, flavonoid content, DPPH radical scavenging activity, and α-amylase inhibition. Phytochemical screening and antioxidant assays were performed to characterize the optimized mixture and compare it with individual plant components and binary combinations. Diabetes was induced in Wistar rats using streptozotocin (50 mg/kg), and treatments were administered orally for 14 days. Results: The optimized mixture exhibited significantly higher total phenolic content (135.65 ± 3.96 mg GAE/g) and flavonoid content (89.62 ± 2.71 mg CE/g) compared with individual plant extracts. Strong antioxidant activity was observed, with ferric reducing antioxidant power (67.42 ± 0.54 µg Trolox/g) and DPPH radical scavenging activity of 59.11 ± 1.58%. In diabetic rats, treatment with the optimized mixture significantly reduced blood glucose levels from 287 mg/dL on day 0 to 173 mg/dL on day 14 (p<0.05). Additionally, the mixture improved lipid profile parameters and reduced serum levels of transaminases, urea, creatinine, and uric acid. Antioxidant enzyme activities, including catalase and superoxide dismutase, were significantly increased, while lipid peroxidation decreased. Conclusion: These findings demonstrate that the combination of Vigna subterranea, Curcuma longa, and Piper nigrum possesses significant antidiabetic and antioxidant properties and may represent a promising nutraceutical strategy for the management of type 2 diabetes.