Pycnocycla spinosa Decne. exBoiss. var. spinosa (Fam. Umbelliferae) is an essential oil-containing wild plant growing in central parts of Iran (Mozafarain, 1996). Hydroalcoholic extract of Pycnocycla spinosa has spasmolytic effects in vitro and anti-diarroheal actions in vivo (Sadraei et al. 2002). The aim of this research was to separate fractions of total hydroalcoholic extract of P. spinosa and screen for their spasmolytic activity to find out which fraction possesses the most antispasmodic activity. The hydroalcoholic extract of P. spinosa constituents includes alkaloids, flavonoids and saponins. These components were separated by a fractional liberation technique. Male Wistar rats were killed by a blow to the head followed by exsanguination. A portion of ileum was removed and suspended in Tyrode solution at 37 °C for contraction studies. An alkaloid fraction of P. spinosa in a concentration-dependent manner inhibited the ileum contraction induced by 80 mM KCl with an IC₅₀ value of 4.5 ± 0.9 mg ml^-1 (mean ± S.E.M., n = 6). With 10 mg ml^-1 bath concentration the response to KCl was almost abolished. The inhibitory effect of the alkaloid fraction was reversible after washing the tissue with fresh Tyrode solution. The flavonoid extract also concentration dependently inhibited the tonic contraction to KCl (IC₅₀ = 12 ± 2.1 mg ml^-1, n = 6). The saponin fraction at relatively higher concentrations had an inhibitory effect on ileum contractions due to KCl. The inhibitory effect starts at 40 mg ml^-1 and at 160 mg ml^-1 about 18 % of the contraction still remained. The alkaloid extract of P. spinosa also reduced the tissue response to 5-hydroxytryptamine (5-HT, 1.28 mM) (IC₅₀ = 4.8 ± 1.2 mg ml^-1, n = 6) and acetylcholine (ACh, 320 nM) (IC₅₀ = 6.5 ± 0.8 mg ml^-1, n = 6) in a concentration-dependent manner. Equivalent volume of vehicle (ethanol) had no significant effect on KCl, ACh or 5-HT responses (ANOVA). From this study it can be concluded that alkaloid, flavonoid and saponin compounds in the total extract of P. spinosa contribute to the spasmolytic activity. As the alkaloid fraction has the most potent constituents and it can inhibit the ileum contractions induced by three different spasmogens, it is suggested that active materials in the alkaloid fraction should be further separated in order to identify the most active chemical structure, which could be used as an antispasmodic in gastrointestinal disorders such as diarrhoea.

All procedures accord with current local guidelines.