Spasmolytic action of Lepechinia caulescens is through calcium channel blockade and NO release

The present study was undertaken to elucidate the mode of action of methanol extract from aerial parts of L. caulescens (TC-MELc) as spasmolytic agent on in vitro rat ileum test, and investigate the possible antibacterial activity of different extracts from the plant. TC-MELc induced a concentration-dependent (0.001 to 100 μg/mL) antispasmodic effect on spontaneous contractions. TC-MELc also (IC50 11.2 μg/mL) induced a marked depression on cumulative concentration-response curve for carbachol (Emax = 2.3 ± 0.3 g vs. 0.66 ± 0.1 g) and serotonin (Emax = 1.1 ± 0.3 g vs. −0.01 ± 0.09 g). Besides, extract decreased and displaced to the right KCl and CaCl2 concentration–response curves. Moreover, TC-MELc (11.2 μg/mL) provoked a total relaxation when ileum strips were contracted with carbachol (1 μM) in calcium-free Krebs solution. Pre-treatment with l-NAME (10 μM) produced a significant change of the relaxant response and activity was markedly inhibited. Additionally, hexanic (HELc), dichloromethanic (DELc) and methanolic (MELc) extracts from aerial parts were studied to determine their antibacterial activity. DELc showed antibacterial activity on all bacterial strains assayed (≤100.0 μg/mL). Data indicate that L. caulescens contains antibacterial and spasmolytic constituents mediating their effect through blockade of Ca2+ influx and NO release, which may explain its traditional use against diarrhoea.