Antispasmodic effects and composition of the essential oils from two South American chemotypes of Lippia alba

Ethopharmacology relevance: Lippia alba (Mill.) N. E. Brown (Verbenaceae) is an aromatic species used in Central and South America as eupeptic for indigestion. In Argentina, it is used by the "criollos" from the Chaco province. There are several chemotypes which differ in the chemical composition of the essential oils. Nowadays, it is experimentally cultivated in some countries of the region, including Argentina. Aim of the study: To compare the chemical composition and pharmacology of the essential oils from two chemotypes: "citral" (CEO) and "linalool" (LEO), in isolated rat duodenum and ileum. Methods: Contractile concentration-response curves (CRC) of acetylcholine (ACh) and calcium in 40 mM K medium (Ca2+-CRC) were done in isolated intestine portions, in the absence and presence of CEO or LEO at different concentrations. Results: Likewise verapamil, CEO and LEO induced a non-competitive inhibition of the ACh-CRC, with IC50 of 7.0 +/- 0.3 mg CEO/mL and 37.2 +/- 4.2 mg LEO/mL. L-NAME, a NO-synthase blocker, increased the IC50 of CEO to 26.1 +/- 8.7 mg CEO/mL. Likewise verapamil, CEO and LEO non-competitively inhibited the Ca2+-CRC, with IC50 of 6.3 +/- 1.7 mg CEO/mL, 7.0 +/- 2.5 mg LEO/mL and 0.24 +/- 0.04 mg verapamil/mL (pIC(50): 6.28). CEO was proved to possess limonene, neral, geranial and (-)-carvone as the major components, while LEO was rich in linalool. Conclusions: Results suggest that CEO has five times more potency than LEO to inhibit muscarinic contractions. The essential oils of both chemotypes interfered with the Ca2+-influx, but with an IC50 about 28 times higher than that of verapamil. Moreover, CEO partially stimulated the NO production. These results show the medicinal usefulness of both Lip pia alba chemotypes, thus validating its traditional use, potency and mechanism of action. (C) 2013 Elsevier Ireland Ltd. All rights reserved.