Relaxant effects of the essential oil of Ocimum gratissimum on isolated ileum of the guinea pig Socorro V.F. Madeira a , Francisco Jose ´ A. Matos b , Jose ´ H. Leal-Cardoso a , David N. Criddle a, * a Departamento de Cie ˆncias Fisiolo ´gicas, Laborato ´rio de Farmacologia dos Canais Io ˆnicos, Centro de Cie ˆncias Sau ´de, Universidade Estadual do Ceara ´, Av. Paranjana 1700, Campus Itaperı ´, Fortaleza, CE 60740-000, Brazil b Departamento de Quı ´mica Analı ´tica e Fisico-Quı ´mica, Laborato ´rio de Produtos Naturais, Universidade Federal do Ceara ´, Fortaleza, Brazil Accepted 1 August 2001 Abstract The effects of the essential oil of Ocimum gratissimum L. (Labiatae) (EOOG) on guinea pig ileum were studied. EOOG (0.1  /1000 mg/ml) reversibly and concentration-dependently relaxed the basal tone of the ileum and reversed the tonic contractions induced by 60 mM KCl and 10 mM acetylcholine, with IC 50 values of 23.89 /5.2, 18.69 /4.0 and 70.09 /4.6 mg/ml, respectively. Our results show that EOOG exerts relaxant effects on intestinal smooth muscle, consistent with the popular use of the plant to treat gastrointestinal disorders. # 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Ocimum gratissimum ; Ileum; Relaxation; Labiatae 1. Introduction The plant Ocimum gratissimum L. (Labiatae) is widely distributed in northeastern Brazil, where it is popularly known as ‘Alfavaca’. It is commonly grown in domestic gardens and is widely used both in cooking for flavouring, as well as for its therapeutic properties as an antiseptic and for the treatment of digestive problems (Matos, 1998). Previously, the African variety of this plant has been shown to exert stomachic, anti-diarrhoeal and laxative actions (Oliver, 1960; El-Said et al., 1969). In Brazil, the flowers and leaves of the plant, which constitute a rich source of essential oils (Silva et al., 1999), are generally utilized to prepare infusions or teas (Matos, 1998). Despite the widespread use of this plant in popular medicine and cuisine, surprisingly little research has been carried out to examine its basic pharmacological properties. A previous study of the Nigerian variety of O. gratissimum L. has shown that aqueous extracts exert contractile effects on intestinal muscle, while at the same time inducing a depression of arterial blood pressure in anaesthetized rats (Onajobi, 1986), but the active principles responsible for these effects were not identi- fied. This study led us to examine the possible actions of the essential oil of O. gratissimum (EOOG) on the isolated intestinal smooth muscle of the guinea pig. 2. Methodology 2.1. Plant material The essential oil of O. gratissimum L. was obtained from the Horto de Plantas Medicinais, Organic and Inorganic Chemistry Department of the Federal Uni- versity of Ceara ´ (Fortaleza). A voucher specimen of the plant has been deposited in the Herba ´rio Prisco Bezerra of the Federal University of Ceara ´ (EAC 14968). 2.2. Extraction and composition of EOOG The isolation of the essential oil from the leaves of the plant was carried out by steam distillation according to the method previously described by Craveiro et al. * Corresponding author. Tel.:  /55-85-299-2507; fax:  /55-85-299- 2503. E-mail address: criddle@uece.br (D.N. Criddle). Journal of Ethnopharmacology 81 (2002) 1  /4 www.elsevier.com/locate/jethpharm 0378-8741/02/$ - see front matter # 2002 Elsevier Science Ireland Ltd. All rights reserved. PII:S0378-8741(02)00049-1