Antispasmodic activity of extracts and compounds of Acalypha phleoides Cav.

The aerial parts of Acalypha phleoides are usually prescribed in the Mexican traditional medicine for a variety of gastrointestinal complaints. The MeOH-CHCl(3) (1:1) extract of the aerial part of A. phleoides showed an inhibitory effect on the gastrointestinal propulsion of a charcoal meal in mice. In isolated guinea-pig ileum, this extract produced a concentration dependent inhibition of the contractions induced by 5-hydroxytryptamine, but it was unable to inhibit the contractions elicited by acetylcholine, histamine, KCl and BaCl(2). This extract produced also a concentration dependent inhibition of the spontaneous pendular movement of the isolated rabbit jejunum. This inhibitory activity was partially blocked by propranolol. The essential oil, obtained from the aerial part of this plant, was more potent than the MeOH-CHCl(3) (1:1) extract in inhibiting the spontaneous pendular movement of the rabbit jejunum. Thymol, camphor and gamma-terpinene were identified from the essential oil by GC-MS. These monoterpenes showed antispasmodic activity in the rabbit jejunum preparation, thymol was the most active compound, followed by camphor and gamma-terpinene. Thymol and camphor in high concentrations also showed tracheal relaxant properties, but gamma-terpinene did not. These in vivo and in vitro results tend to support the traditional use of A. phleoides as an antispasmodic agent.