Antidiabetic effect of aqueous stem bark extract of Parinari macrophylla in alloxan-induced diabetic Wistar rats

Background: Diabetes is a major public health problem with increasing prevalence globally. Plant-based medicines for diabetes are gaining popularity across the world due to perceptions of efficacy, safety and cost-effectiveness. The plant, Parinari macrophylla, has been widely reported to possess potent ethnomedicinal properties especially in the northern part of Nigeria. However, there has been no scientific documentation of this plant to be used as an antidiabetic agent. The objective of this study was to investigate the antidiabetic effect of aqueous stem bark extract of P. macrophylla in alloxan-induced diabetic Wistar rats. Phytochemical screening and acute toxicity studies were conducted. Wistar rats weighing between 100 and 150 g were used for the study and diabetes was induced using alloxan monohydrate (150 mg/kg) intraperitoneally. The animals were treated with different doses of aqueous stem bark extract of P. macrophylla (1000 mg/kg and 2000 mg/kg) for 2 weeks. Blood glucose levels and body weight were then monitored. Histopathological investigation of pancreatic tissue was also conducted. Results: The phytochemical analysis revealed the presence of alkaloids, saponins, tannins, cardiac glycosides, carbohydrates, steroids, and triterpenes as secondary metabolites. The acute toxicity test revealed no mortality with a median lethal dose determined to be above 5000 mg/kg. Although the two different doses of aqueous stem bark extract of P. macrophylla decreased blood glucose levels at weeks 1 and 2, a statistically significant difference (P < 0.05) was only observed for the group treated with 2000 mg/kg dose compared to the diabetic control group at week 2. The histological investigation revealed that the two different doses of aqueous stem bark extract of P. macrophylla caused regeneration of pancreatic islet cells, with the 2000 mg/kg dose being more evident. Conclusion: This study suggests that the stem bark extract of P. macrophylla possesses a potent antidiabetic effect and may potentially be used to treat diabetes and associated complications.