Hypoglycemic and in vitro antioxidant activities of Stereospermum kunthianum stem bark hydromethanol extract

This study investigated Stereospermum kunthianum stem bark hydromethanol extract for hypoglycemic and in vitro antioxidant activities. Phytochemical analyses were performed to determine the components of the extract. In vitro antioxidant activities of the extract were assessed with 1, 1-diphenyl-2-picrylhydrazyl radical scavenging and ferric reducing /antioxidant power assays. An oral acute toxicity study to determine the safe dose of the extract was conducted in albino Wistar rats. Evaluation of the extract's hypoglycemic activities on blood glucose levels of normal, glucose loaded and streptozotocin-induced diabetic rats were performed. The extract contained various constituents, including saponins, terpenes, tannins, flavonoids, carbohydrates, alkaloids, and steroids. 1, 1-diphenyl-2-picrylhydrazyl radical scavenging assay proved more sensitive, showing a concentration-dependent increase in antioxidant capacity of the extract, which peaked at 71.8% relative to ascorbic acid (92.9%) at the highest test concentration (400 μg mL-1). The rats tolerated Stereospermum kunthianum extracts with the oral LD50 of more than 5000 mg kg-1. Interestingly, various doses (100-400 mg kg-1) of the extract were effective in causing significant (p≤0.05) reductions in the blood glucose levels of normoglycemic, glucose challenged and streptozotocin-induced diabetic rats when compared to their controls. The results suggest that the stem bark extract of S. kunthianum was a relatively safe herbal extract, rich in phytochemicals, possessed good antioxidant activity, with potential anti-diabetic effects.