Evaluation of hypoglycemic activity, phytochemical composition and acute toxicity of Opuntia humifusa Raf. cladode extracts in Wistar albino rats

Abstract

Background Local communities in Central Uganda are using the cladodes of Opuntia humifusa in the treatment of diabetes mellitus with the claim that the plant is effective. However, efficacy and safety of the plant is not scientifically validated in Uganda. The aim of this study was to determine the phytochemical composition, hypoglycemic effect and acute toxicity of Opuntia humifusa cladode extracts in Wistar albino rats. Methods Cladodes of O. humifusa were extracted using methanol and water. Phytochemical screening of cladode extracts was done. Hypoglycemic activity of cladode extracts was determined using doses of 200 mg/kg and 400 mg/kg in rats by measuring of fasting blood glucose levels using a glucometer and strips. Alloxan monohydrate (150 mg/kg) was used to induce diabetes mellitus. Estimating of the median lethal dose (LD50) and observing of clinical signs for 14 days was done using doses of 2000 mg/kg and 5000 mg/kg of aqueous extract. This was followed by histopathological evaluation of the liver, kidney, stomach and small intestine. Data analysis was done using Graph pad prism 8 version software. P value < 0.05 was considered statistically significant. Results Phytochemical screening of methanol and aqueous cladode extracts showed the presence of alkaloids, flavonoids, saponins, tannins, phenolic compounds, terpenoids and glycosides. O. humifusa cladodes lowered glucose levels, hypoglycemic effect was statistically significant (p<0.05) in both the methanol and aqueous extracts at doses of 200 mg/kg and 400 mg/kg. LD50 was estimated to be 2000 mg/kg< LD50 <5000 mg/kg. Organ lesions occurred on the liver, stomach and small intestine. Clinical signs such as piloerection, lethargy, writhing, tremors and convulsions were seen within the first 4 hours of observation. Conclusion The Opuntia humifusa cladode aqueous and methanol extracts were rich in phytochemicals such as alkaloids, saponins, glycosides, tannins, flavonoids, phenolic compounds and terpenoids. The O. humifusa cladode aqueous and methanol extracts were able to cause hypoglycemic effect when orally administered for 12 days in alloxan induced diabetic rats. The estimated LD50 obtained showed that aqueous cladode extract has low toxicity to the human population, based on the Globally Harmonized System for classification and labeling of chemicals. Clinical signs and organ damage showed that there could be a possibility of side effects when aqueous cladode extract is consumed.