Vol. 7(30), pp. 2167-2172, 15 August, 2013 DOI 10.5897/AJPP2013.3510 ISSN 1996-0816 © 2013 Academic Journals http://www.academicjournals.org/AJPP African Journal of Pharmacy and Pharmacology Full Length Research Paper Acute modulation of rat plasma glucose byan aqueous garlic extract Meherzia Mokni 1 , Sonia Hamlaoui 1 *, Ferid Limam 2 , Mohamed Amri 1 and Ezzedine Aouani 2 1 Laboratoire de Neurophysiologie Fonctionnelle et Pathologies, Département des Sciences Biologiques, Faculté des Sciences de Tunis. Campus Universitaire El Manar II-2092 Tunis, Tunisie. 2 Laboratoire des Substances Bioactives, Centre de Biotechnologie, Technopole Borj-Cedria, BP-901, 2050 Hammam- Lif, Tunis, Tunisie. Accepted 19 July, 2013 In this study, the putative antidiabetic effect of garlic was re-investigated. Aqueous crude garlic solution was prepared at high concentration (2 g/ml) and extracts were obtained by ethanol precipitation followed by chromatography on C18 Sep-Pak cartridge. Garlic or extracts were administered by single intraperitoneal injection to euglycaemic rats. Plasma glucose, insulin and nitric oxide (NO) were determined after 30 min, 1 and 2 h, respectively. Garlic induced hypoglycemia and hyperinsulinemia which is mimicked by an ethanol soluble and non polar extract. This active principle appeared different from S-allyl-cystein sulfoxide based on physico-chemical properties and mode of action. Data of thin layer chromatography experiments indicated the presence of at least four molecular species, indicating a more non polar nature, with Rf values higher than S-allyl-cystein sulfoxide. The mechanism of action seemed to involve nitric oxide as its glucose induced lowering activity is abolished by diphenyleneiodonium which is a selective constitutive nitric oxide synthase inhibitor. Key words: Garlic, Plasma Glucose, Insulinemia, Nitric Oxide, Thin Layer Chromatography. INTRODUCTION Garlic (Allium sativum L.), an indigenous dietary component, belongs to the Liliaceae family and is widely used as a condiment. Besides, it is also used widely in home remedies and pharmacotherapy against debilitated pathologies because of its antioxidant (Lieben et al., 2012), anticardiovascular (Ginter and Simko, 2010), and antihyperglycemic (Kumar et al., 2013) activities. The antidiabetic effect of garlic is still controversial. Although some investigators (Swanston-Flatt et al., 1990; Baluchnejadmojarad et al., 2003) were unable to detect any glucose lowering activity in garlic preparations, some others described plasma glucose lowering activity and insulin secretagogue effect on a sulfur derived amino acid identified as S-allyl-cysteine-sulfoxide (SACS) (Bordia et al., 1977; Sheela and Augusti, 1992; Kook et al., 2009). Moreover this insulin secreting activity was only demonstrated in vitro, using isolated cells from normal rat pancreas (Augusti and Sheela, 1996). Although the mode of garlic’s action or its derivatives is still uncertain, nitric oxide (NO) was suggested as a putative mediator (Mokni et al., 2006; Lieben et al., 2012) especially in antihypertensive effects (Pedraza-Chaverri et al., 1998). NO is synthesized from L-arginine by NO synthase (NOS) which exist in three isoforms: neuronal, endothelial constitutive and inducible form (Kerwin et al., 1995). NO, derived from constitutive NOS, is reported to modulate vasomotor tone, inhibition of platelet or leukocyte aggregation and adhesion to the endothelium *Corresponding author. E-mail: sonia_hamlaoui@yahoo.fr. Tel: 216 98 968 113. Fax: 216 71 885 480.