BACKGROUND

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.

OBJECTIVE

To evaluate the putative depressant effects of an aqueous extract of the medicinal plant Clinopodium mexicanum on the central nervous system (CNS).

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 1000mg/kg doses prolonged the sleeping time induced by sodium pentobarbital (42mg/kg). This extract, at 100 and 200mg/kg doses, showed a sedative effect in the hole-board paradigm and decreased spontaneous activity in mice. AECM at 10, 100 and 200mg/kg prolonged the onset of seizures induced by pentylenetetrazole (90mg/kg) and antagonized tonic convulsions induced by picrotoxin (10mg/kg). Additionally, AECM inhibited the response to a thermonociceptive stimulus. The intraperitoneal AECM treatment produced mortality with an LD(50)=2154mg/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.