Journal of Ethnopharmacology 130 (2010) 1–8 Contents lists available at ScienceDirect Journal of Ethnopharmacology journal homepage: www.elsevier.com/locate/jethpharm Depressant effects of Clinopodium mexicanum Benth. Govaerts (Lamiaceae) on the central nervous system R. Estrada-Reyes a,b , M. Martínez-Vázquez b,∗ , A. Gallegos-Solís a , G. Heinze c , J. Moreno c a Laboratorio de Fitofarmacología, Dirección de Investigaciones en Neurociencias, Instituto Nacional de Psiquiatría Ramón de la Fuente Mu˜ niz, Calzada México-Xochimilco 101, Col. San Lorenzo Huipulco, Delegación Tlalpan, Mexico City 14370, Mexico b Instituto de Química, Universidad Nacional Autónoma de Mexico, Coyoacan, Mexico D.F. 04510, Mexico c Dirección de Servicios Clínicos, Instituto Nacional de Psiquiatría Ramón de la Fuente Mu˜ niz, Calzada México-Xochimilco 101, Col. San Lorenzo Huipulco, Delegación Tlalpan, Mexico City 14370, Mexico article info Article history: Received 19 September 2009 Received in revised form 30 January 2010 Accepted 10 March 2010 Available online 31 March 2010 Keywords: Depressant Central nervous system Sedative-hypnotic Clinopodium mexicanum Satureja mexicana Toronjil abstract Ethnopharmacological relevance: The decoction of leaves of Clinopodium mexicanum Benth. Goaverts (Lamiaceae), commonly known as “Toronjil de Monte”, is used in the Mexican traditional medicine to induce sleep, as well as sedative and analgesic remedy. Aim of the study: To evaluate the putative depressant effects of an aqueous extract of the medicinal plant Clinopodium mexicanum on the central nervous system (CNS). Materials and methods: The effects of the extract (AECM) on mice were tested in several animal paradigms, including sodium pentobarbital-induced sleep, open field tests, and hole-board tests. The effects of AECM on pentylenetetrazole- and picrotoxin-induced convulsions in mice and on the antithermonociceptive response in the hot-plate paradigm were also tested. Additionally, the active extract (AECM) was analyzed with HPLC–ESI-MS techniques. Results: Mice acutely treated with AECM at 100, 200, 500 and 1000 mg/kg doses prolonged the sleeping time induced by sodium pentobarbital (42 mg/kg). This extract, at 100 and 200 mg/kg doses, showed a sedative effect in the hole-board paradigm and decreased spontaneous activity in mice. AECM at 10, 100 and 200 mg/kg prolonged the onset of seizures induced by pentylenetetrazole (90 mg/kg) and antago- nized tonic convulsions induced by picrotoxin (10 mg/kg). Additionally, AECM inhibited the response to a thermonociceptive stimulus. The intraperitoneal AECM treatment produced mortality with an LD 50 = 2154 mg/kg. Chemical analysis showed that the flavanone glycosides neoponcirin, poncirin, and isonaringenin are the main compounds of the active extract. Conclusions: This study demonstrates that an acutely administered single dose of an aqueous extract of Clinopodium mexicanum can exert depressant effects on the CNS. These findings are in agreement with the traditional use of Clinopodium mexicanum to induce sleep as well as sedative and analgesic remedy. The chemical analysis of AECM revealed the presence of the flavanone glycosides neoponcirin, poncirin, and isonaringin. © 2010 Elsevier Ireland Ltd. All rights reserved. 1. Introduction Clinopodium (Lamiaceae) is a cosmopolitan genus whose dis- tribution covers southern and southeastern Europe, Anatolia, northern Iran, Russia, Asia, Ethiopia, the United States of Amer- ica, and Mexico. This wide distribution enables the medical use of several species. For example, in Pakistan, Clinopodium umbrosum and Clinopodium vulgare are both used to treat wounds, bleeding and cardiac problems (Khan and Khatoon, 2008). In the USA, a ∗ Corresponding author. E-mail addresses: oscar.martinezvazquez@gmail.com, marvaz@servidor.unam.mx (M. Martínez-Vázquez). decoction of Clinopodium douglasii has been used by the Costanoan Indians as an anthelmintic remedy (Bocek, 1984). In Portugal, the leaves of Clinopodium ascendens are used as a mouth freshener and to alleviate headache and toothache (Castilho et al., 2006). In Mexico, the genus Clinopodium is represented by 13 aromatic species, some of which are used as medicinal herbs. Clinopodium mexicanum Benth. Govaerts (Lamiaceae) (Syn. Gardoquia mexi- cana Benth, Satureja mexicana (Benth) Brinq.) is a perennial herb endemic to Hidalgo, Guerrero, Oaxaca, and Veracruz States. This species possesses small red-colored flowers, often attains a height of 30–80 cm, and is more commonly known by its vernacular name “Toronjil de Menta” (mint’s hyssop). Local people use the whole plant to relieve toothache and “nervousness” (Harley and Granda, 2000). In Mexico City, Clinopodium mexicanum is also known as 0378-8741/$ – see front matter © 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.jep.2010.03.012