Trop J Nat Prod Res, June 2021; 5(6):1130-1137 ISSN 2616-0684 (Print) ISSN 2616-0692 (Electronic) 1130 © 2021 the authors. This work is licensed under the Creative Commons Attribution 4.0 International License 1133 1135 1134 Tropical Journal of Natural Product Research Available online at https://www.tjnpr.org Original Research Article Antidiabetic Investigations of Aqueous and Ethanol Extracts of Terminalia macroptera (Guill. & Perr.) Stem Bark in Streptozotocin-Induced Diabetic Wistar Rats Ambrose E. Akpovona 1 * and Iyere O. Onoagbe 2 1 Department of Biochemistry, Faculty of Natural and Applied Sciences, Michael and Cecilia Ibru University, Ughelli North, Delta State, Nigeria 2 Department of Biochemistry, Faculty of Life Sciences, University of Benin, Benin City, Nigeria Introduction Diabetes mellitus (DM) is an anomaly in sugar metabolism that is characterized by the destruction of blood tissues and peripheral organs following chronic high glucose concentration that are due largely to non-secretion of insulin by pancreas or the non-recognition of same by receptors. 1 The disease partly has its origin at the molecular level, and it is expressed physiologically in insulin changes as well as in sustained high glucose levels. These changes lead to alterations in serum lipid profiles (SLP) which result in serious complications and failure of various organs. 2 Oral synthetic hypoglycemic agents and insulin are usually used for the treatment of this metabolic derangement; however, their use over time has diminished due in part to their undesirable side effects such as the development of hypoglycemia, angiopathy, and induction of obesity. 3 The actions of these drugs have shown that they are useful for the management of the disease but not curative. 4 Consequently, scientists are in pursuit of more therapeutic agents that can permanently stop the plague. *Corresponding author. E mail: akpovonaambrose@mciu.edu.ng; aeakpovona@gmail.com. Tel: 08029760507. Citation: Akpovona AE and Onoagbe IO. Antidiabetic Investigations of Aqueous and Ethanol Extracts of Terminalia macroptera (Guill. & Perr.) Stem Bark in Streptozotocin-Induced Diabetic Wistar Rats. Trop J Nat Prod Res. 2021; 5(6): 1130-1137. doi.org/10.26538/tjnpr/v5i6.25 Official Journal of the Natural Product Research Group, Faculty of Pharmacy, University of Benin, Benin City, Nigeria. The search for a remedy has led to the investigation of Terminalia macroptera, a member of Combretaceae family which grows in the tropical savannah biome that is characterized by little rainfall and a long arid period. 5 The plant gives rise to a saucer-like fruit that is light green to purple tinge with its seed encased at the centre and bordered by a thin delicate wing. 6 The bark of the stem contains a high quantity of hydrolyzable tannins that are anti-Bacillus subtilis. 7 Also, extracts of the root bark and leaves have been shown to possess antiplasmodial and anti-bacterial activities. 8-10 Terminalia macroptera has been reportedly used in the treatment of rheumatism and diabetes. 11 It was revealed that useful bioactive molecules like flavonoids, tannins, saponins, alkaloids, and terpenoids are contained in the plant’s stem bark which has also shown erythropoietic properties. 7,12,13 Previous toxicological studies of the stem bark extract in brine shrimp and Wistar rats showed a relatively nontoxic profile. 14,15 Despite the previous experiments and other claims by locals that the plant is utilized in the treatment of diabetes, it is, however, noted that the validity of this plant in lowering elevated blood sugar is yet to be scientifically certified. This study, therefore, investigated the antidiabetic properties of the aqueous (AE) and ethanol extracts (EE) of the plant’s stem bark. Materials and Methods Chemicals and instruments All the chemicals used were of research standard (98–99.8% purity) purchased from registered dealers and were utilized as delivered without further purification. Equipment used for analysis included enzyme-linked immunosorbent assay (ELISA) microplate reader (Spectramax 340 PC molecular device), BIO-RAD thermocycler (model: iCycler 96 Well Reaction Module, S/N 583BR005717, USA), Jen-way UV-VIS spectrophotometer (model 6305, UK), ARTICLE INFO ABSTRACT Article history: Received 19 April 2021 Revised 14 June 2021 Accepted 21 June 2021 Published online 01 July 2021 Diabetes mellitus always-increasing prevalence has prompted investigations into plants traditionally extolled for antidiabetic properties. One of such is Terminalia macroptera, a member of the Combretaceae family that grows in the Savannah. Consequently, this study evaluated the antidiabetic potentials of the stem bark aqueous (AE) and ethanol extracts (EE). Wistar rats were allotted into 2 controls (nondiabetic and diabetic) and 2 treatment (diabetic) groups ( n = 5). All diabetic groups were induced intraperitoneally with streptozotocin (55 mg/kg body weight) from which respective treatment groups were orally administered AE and EE (200 mg/kg/day), while controls received water for 70 days. Thereafter, the concentrations of glucose, lipids, insulin, C- peptide, testosterone, and α-amylase activities were measured in serum. Liver homogenates were evaluated for glycogen and antioxidant status, while mRNA expressions of PDX-1, insulin-1, TNF-α, and Il-1 β were examined in β-cell. AE and EE, respectively, caused 55.66% and 78.95% reductions in elevated glucose when compared to control. However, only EE-treated rats had glucose and glycogen levels normalized besides increased insulin concentration (P < 0.05 vs diabetic control, DC). Both extracts significantly decreased lipid profiles but caused increase in antioxidant levels (P < 0.05 vs DC). In contrast to AE, EE slightly increased C-peptide and testosterone concentrations but significantly enhanced α-amylase activity. Up-regulated insulin gene expressions remained unabated, but those of PDX-1 and inflammatory factors were downregulated by both extracts (P < 0.05 vs DC). Terminalia macroptera stem bark was revealed to possess antidiabetic properties that were better expressed by EE through insulin stimulation. Keywords: Glucose, C-peptide, insulin gene, pancreatic duodenal homeobox-1, tumor necrosis factor-, interleukin-1. Copyright: © 2021 Akpovona and Onoagbe. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 1130