Introduction Diabetes mellitus (DM) is a metabolic disorder marked by chronic high blood glucose, which results in an array of secondary complications of the heart, kidney, and eyes (1). DM is the predominant cause of death around the world affecting both developing and developed countries. DM is, therefore, a serious health challenge placing a heavy burden on the economy. The global prevalence of DM has shown an alarming projection in recent times and according to the World Health Organization (WHO), diabetes will be seen as the seventh leading cause of mortality by the year 2030 (2). Taking into account the pathology of diabetes, the prevention of beta cell from degenerating and enhancement of the endogenous regeneration of islets will be a crucial strategy in the management of diabetes. Despite the availability of therapy for diabetes management, there is a growing interest in using anti-diabetic compounds from natural sources because of the unwanted adverse effects of the available drugs (3). A wide range of studies are available on the advantageous effects of using phytotherapy for the management of diabetes (4). The mechanism of action of phytochemicals and active isolate(s) from plants is by decreasing intestinal absorption of glucose, inhibiting hepatic gluconeogenesis, enhancing uptake of glucose by tissues, stimulation of insulin release by the pancreas, and/or regenerating pancreatic tissues (5-7) Spondias mombin is a fructiferous plant belonging to a large family referred to as Anacardiaceae. All parts of the plant have been used in the management of various disease conditions. These conditions include cardiovascular diseases, dysentery, hemorrhoids, and diarrhea (8). Hosseini et al (9) in their reports on the “pancreatic beta cell protection/ regeneration with phytotherapy” recorded an increase in the number, percentage, and volume density of beta cells in islets of the treated diabetic animals. We, therefore, aimed to determine the improvement of insulin secretion and effects of leaf extracts (aqueous and ethanol) of S. mombin on pancreatic islet cell regeneration in streptozotocin-induced diabetic rats. Avicenna Journal of Medical Biochemistry © 2020 The Author(s); Published by Hamadan University of Medical Sciences. This is an open-access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 2020 June;8(1):15-20 doi:10.34172/ajmb.2020.02 Preliminary Nutrient Determination and Regeneration of Pancreatic Islet Cells by Extracts of Spondias mombin Leaves in Streptozotocin-Induced Diabetic Rats Nkeiruka Eluehike 1* ID , Iyere Osolase Onoagbe 2 ID 1 Department of Medical Biochemistry, School of Basic Medical Sciences, University of Benin, Benin City, Nigeria. 2 Department of Biochemistry, Faculty of Life Sciences, University of Benin, Benin City, Nigeria. http://ajmb.umsha.ac.ir Research Article Received: 20 March 2020 Accepted: 19 June 2020 ePublished: 29 June 2020 Abstract Background: There is a growing trend towards the use of medicinal plant that can prevent degeneration of pancreatic cells and regenerate islet cells in diabetes treatment Objectives: The possible effects of the extracts of Spondias mombin leaves on the regeneration of pancreatic beta cells in streptozotocin (STZ)-induced diabetic rats were determined in this study. Methods: Twenty-five male Wistar rats were randomly divided into 5 groups (A-E) including normal and diabetic rats. Aqueous and ethanol extracts of S. mombin were administered orally to diabetic rats in groups D and E for 12 weeks. Blood samples were collected for serum insulin and C-peptide assays. The pancreases were also collected for histopathological examination. Additionally, mineral and vitamin contents of the leaves were determined using standard procedures. Results: The highest vitamin content was vitamin C in the leaves, while the highest mineral content was calcium. Treatment with extracts of Spondias mombin attenuated the STZ-induced hypoinsulinemia, which was evident from the increased serum insulin and c-peptide levels in the extract treated groups. Histopathological examination of the pancreas revealed an increase in the number and size of the pancreatic beta cells in the extracts treated groups in comparison to the shrunken and diminished islet cells observed in the untreated animals. Conclusion: Extracts of S. mombin leaves are capable of regenerating pancreatic β-cells which were destroyed by streptozotocin induction. Keywords: Pancreatic β-cells, S. mombin, insulin, C-peptide, Diabetes *Corresponding author: Nkeiruka Eluehike, Department of Medical Biochemistry, School of Basic Medical Sciences, University of Benin, Benin City, Nigeria. Tel: +2348061344256, Email:nkeiruka.ezeugwu@ uniben.edu