RESUMO
ETHNOPHARMACOLOGICAL RELEVANCE: Lippia alnifolia Mart. & Schauer, known as "alecrim-do-mato", "alecrim-de-vaqueiro" and "pedrécio", is used in folk medicine as antiseptic and to treat diseases that affect respiratory system, like bronchitis and asthma. AIM OF THE STUDY: The aim of this work was to investigate the spasmolytic activity and relaxant mechanism of the Lippia alnifolia essential oil (EOLA) on isolated guinea-pig trachea and to correlate with its use in folk medicine. MATERIALS AND METHODS: Leaves from L. alnifolia were collected in Pico das Almas, Chapada Diamantina, situated in the city of Rio de Contas, Bahia, Brazil. EOLA was extracted by hydrodistillation, analyzed by GC/FID and GC/MS and the volatile constituents were identified. Spasmolytic activity was assayed in isolated guinea-pig trachea pre-contracted with carbachol 1⯵M or histamine 10⯵M. Relaxant mechanism of EOLA was determined comparing concentration-response curves in the presence or absence of different blockers. RESULTS: Chemical analysis revealed the presence of carvone (60⯱â¯0.8%) as major constituent. EOLA (1-243⯵g/mL) relaxed isolated guinea-pig trachea pre-contracted with carbachol 1⯵M [EC50â¯=â¯53.36 (44.75-63.51) µg/mL] or histamine 10⯵M [EC50â¯=â¯5.42 (4.42-6.65) µg/mL]. The pre-incubation of 4-aminopyridine in histamine-induced contractions did not alter significantly the relaxant effect of EOLA. However, the presence of cesium chloride, glibenclamide, tetraethylammonium, propranolol, indomethacin, dexamethasone, hexamethonium, atropine, L-NAME, methylene blue or ODQ reduced EOLA relaxant effect. EOLA 18⯵g/mL pre-incubation in calcium-free medium reduced histamine-evoked contractions, but did not alter histamine contractions in the presence of nifedipine. CONCLUSIONS: Lippia alnifolia essential oil has spasmolytic activity on isolated guinea-pig trachea and its mechanism of action possibly involves the activation of multiple signal transduction pathways, which culminate in potassium channels activation and cytosolic calcium reduction.