Cholinomimetic and calcium channel blocking activities of Carthamus oxycantha

The crude extract of Carthamus oxycantha (Co.Cr) and its fractions were studied in vitro for their possible spasmogenic and spasmolytic activities. Co.Cr (0.03–10 mg/mL) caused an atropine sensitive spasmogenic effect in guinea‐pig ileum. In spontaneously contracting rabbit jejunum preparations, Co.Cr caused a dose‐dependent (0.03–3.0 mg/mL) spasmogenic effect, followed by relaxation at the next higher doses of 5.0–10.0 mg/mL. In the presence of atropine, the spasmogenic effect was blocked and the relaxant effect was observed at lower doses (0.1–5.0 mg/mL), shifting the inhibitory dose‐response curves to the left. Co.Cr also inhibited K + (80 m m )‐induced contractions in atropinized preparations at similar doses, suggesting calcium channel blockade (CCB) activity. The CCB effect was further confirmed when pretreatment of the tissue with Co.Cr produced a dose‐dependent shift in the Ca ++ dose‐response curves to the right, similar to that caused by verapamil. Activity‐directed fractionation revealed that the spasmolytic effect was concentrated in organic fractions in the following order of potency: hexane > ethylacetate > chloroform, while the aqueous fraction exhibited spasmogenic and weak spasmolytic effects. These results indicate that Carthamus oxycantha contains a combination of spasmogenic (cholinergic) and spasmolytic (calcium antagonist) constituents. Copyright © 2005 John Wiley & Sons, Ltd.