Relaxant and antispasmodic effects of extracts of the orchid Encyclia michuacana on isolated guinea pig ileum.

The antispasmodic effects of hexane-, chloroform-, methanol- and water-extracts of the orchid Encyclia michuacana were studied in vitro on guinea pig ileum against three spasmogens: acetylcholine (Ach), histamine and barium chloride. The chloroform extract exerted a significant antispasmodic effect on ileum contractions induced by Ach, histamine and barium chloride (IC(50) = 90.64, 73.12 and 115.2 microg/mL, respectively). Furthermore, the chloroform extract of E. michuacana provoked a concentration-dependent inhibition of spontaneous contractions of guinea pig ileum with potencies comparable to those of papaverine. The antagonism against the spasmogens used suggests that the action of the chloroform extract of E. michuacana could be due mainly to the presence of gigantol. Hexane-, methanol- and water-extracts did not elicit any significant spasmolytic activity.