Trop J Nat Prod Res, May 2020; 4(6):233-236 ISSN 2616-0684 (Print) ISSN 2616-0692 (Electronic) 233 © 2020 the authors. This work is licensed under the Creative Commons Attribution 4.0 International License Tropical Journal of Natural Product Research Available online at https://www.tjnpr.org Original Research Article Effect of Pterocarpus santalinoides Leaf Extract on Oral Glucose Tolerance Test in Normal and Alloxan-Induced Diabetic Rats Kelechi G. Madubuike 1 *, Aruh O. Anaga 2 , Isaac U. Asuzu 2 1 Department of Veterinary Physiology and Pharmacology, Michael Okpara University of Agriculture, Umudike. 2 Department of Veterinary Physiology and Pharmacology, University of Nigeria, Nsukka. Introduction The use of plant materials for treating human and animal diseases dates prior to the advent of civilization. 1 Since then, interest in plant extracts for healing purposes has been on the increase, owing to their easy accessibility, cost-effectiveness and safety. 2 The World Health Organization (WHO) estimates that 80% of the population of developing countries (which constitute about 4 billion people) rely on traditional medicine for their primary healthcare needs. 3 It is on record that 85% of traditional medicine involves the use of plant materials for the treatment of diseases. 4 Also, about 25% of synthetic drugs prescribed globally originated from plants. 5 Today, researchers are combing this vegetation treasure hub for biologically active phytoconstituents, which are leads towards the discovery of novel drugs that will combat some chronic ailments, which seem to be defying currently available remedies. One of such chronic ailments is diabetes mellitus – a metabolic disorder characterized by persistent hyperglycemia, resulting from insufficient insulin secretion or poor utilization by cells. 6,7 Currently, treatment of diabetes involves insulin therapy, oral hypoglycemic *Corresponding author. E mail: drkaycee2002@yahoo.com; madubuike.kelechi@mouau.edu.ng Tel: +2348036689778 Citation: Madubuike KG, Anaga AO, Asuzu IU. Effect of Pterocarpus santalinoides Leaf Extract on Oral Glucose Tolerance Test in Normal and Alloxan-Induced Diabetic Rats. Trop J Nat Prod Res. 2020; 4(6):233-236. doi.org/10.26538/tjnpr/v4i6.4 Official Journal of Natural Product Research Group, Faculty of Pharmacy, University of Benin, Benin City, Nigeria. drugs (OHDs) and lifestyle intervention through exercise and modification of diet. 8 Side effects associated with the use of OHDs and insulin therapy such as severe hypoglycemia, weight gain and gastrointestinal disturbances. 7,9 have led to the search for new, potent and safer antidiabetic drugs. Oral glucose tolerance test measures the ability of the body to utilize glucose. 10 It is a convenient means of screening substances, especially ethnobotanicals for antidiabetic potential. 11 Pterocarpus santalinoides is a culinary vegetable found in Nigeria and some other West African countries. Common names of the plant in some ethnic groups in Nigeria include: nturukpa (Igbo), gunduru (Hausa), gbengbe (Yoruba), nja (Efik), ikyarakwa or kereke (Tiv), maganchi (Nupe), okumeze (Edo) and piegwu or uturukpa (Igede). 12 Decoction of the leaves of P. santalinoides is used to relieve symptoms of diabetes, stomach ache, diarrhea. 13,14 Previous studies have reported hypoglycemic activity of the plant, 11,15 however, its mechanism of action is still unknown. This study seeks to investigate the effect of the methanol leaf extract of Pterocarpus santalinoides on postprandial hyperglycemia in rats, as a means of elucidating the possible mechanism of action of the plant. Materials and Methods Collection and identification of plant material Fresh leaves of P. santalinoides were collected from Nsukka, Enugu State, Nigeria, in October, 2014. Identification and authentication of the plant material was done by Mr. A. O. Ozioko, a taxonomist with the Bioresources Development and Conservation Programme (BDCP), Nsukka. A voucher specimen (with identification number MOUAU/VPP/2014/017) has been deposited in the herbarium of the Department of Veterinary Physiology and Pharmacology, Michael Okpara University of Agriculture, Umudike, Abia State, Nigeria. ARTICLE INFO ABSTRACT Article history: Received 19 May 2020 Revised 05 June 2020 Accepted 26 June 2020 Published online 02 July 2020 Hypoglycemic effect of Pterocarpus santalinoides has been scientifically reported but without any clue to its mechanism of action. To elucidate its mode of hypoglycemic activity, the effect of the plant on postprandial hyperglycemia was investigated. Dried, pulverized leaves (500 g) of P. santalinoides was macerated in 80% methanol (1.5 L), filtered and concentrated to dryness. Preliminary phytochemistry of the extract was done and its acute toxicity was evaluated following the up-and-down method. The effect of varying doses (50, 100 and 200 mg kg -1 , per os) of the extract on oral glucose tolerance test was assessed in normal and alloxan (160 mg kg -1 , i.p.)-induced diabetic rats. The positive and negative control groups received glibenclamide (2 mg kg -1 ) and distilled water (5 mL kg -1 ), respectively. Glycosides, alkaloids, flavonoids, saponins tannins and terpenes were found to be present in the extract. Its acute toxicity test recorded neither death nor sign of toxicity in the rats even at the maximum oral dose of 5000 mg kg -1 . In normal rats, 50, 100 and 200 mg kg -1 of the extract exhibited significant (p < 0.05) hypoglycemic activity by lowering blood glucose levels to 70.00±2.85, 69.33±3.29 and 68.17±3.34 mg dL -1 , respectively, 180 min post-glucose load (2 g kg -1 ). In diabetic rats, the extract (100 and 200 mg kg -1 ) significantly (p < 0.05) lowered blood glucose levels of treated rats when compared with the negative control group. The results show that Pterocarpus santalinoides leaf extract significantly lowers blood glucose levels in rats, via enhanced glucose utilization. Keywords: Pterocarpus santalinoides, hyperglycemia, alloxan, glucose, postprandial. Copyright: © 2020 Madubuike et al. 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.