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. Graphical Abstract

Background Diabetes mellitus is one of the leading causes of morbidity and mortality globally. Although synthetic hypoglycemic agents are commonly used to manage this disorder, such medications, besides being unable to cure the disease, are expensive and associated with side effects. Conversely, medicinal plants have emerged as effective, safe and affordable alternative treatments. Boswellia dalzielii plant has been reported to possess ethnomedicinal properties for the treatment of various health conditions; however, scientific studies exploring this plant as antihyperglycemic agent are still limited. Thus, this study evaluated the antihyperglycemic activity of aqueous stem bark extract (ASBE) of B. dalzielii in alloxan-induced diabetic Wistar albino rats. Methods Phytochemical screening of the ASBE of B. dalzielii was conducted. Twenty male Wistar albino rats weighing 100–150 g divided into 4 groups (A–D) of five rats were used for the study. Group A served as the normal control and received neither ASBE of B. dalzielii nor glibenclamide. The treatment for the other three groups was as follows: Group B, 10 mg/kg of glibenclamide (diabetic control); Group C, 500 mg/kg ASBE of B. dalzielii; and Group D, 1000 mg/kg ASBE of B. dalzielii. Treatments were administered orally every 24 h for a period of 2 weeks. Blood glucose level and body weight were evaluated at weeks 0, 1 and 2. Histomorphological features of the rats’ pancreas in all the groups were compared. Results The phytochemical analysis revealed the presence of alkaloids, saponins, tannins, cardiac glycosides, flavonoids, carbohydrates, steroids and triterpenes. The two different doses of the plant extract significantly reduced blood glucose level at weeks 1 and 2 (all p < 0.05), with the 1000 mg/kg dose demonstrating a greater reduction compared with glibenclamide at week 2 (p = 0.014). However, only the 500 mg/kg dose led to restoration, albeit slight, of the pancreatic islet cells. Conclusion This study suggests that B. dalzielii plant exhibits a potent antihyperglycemic activity evidenced by reduced blood glucose levels and slight restoration of pancreatic islet cells. This plant could be, therefore, considered in the treatment of diabetes mellitus. Graphical Abstract