Studies on spasmogenic and spasmolytic activities of Calendula officinalis flowers.
The aqueous-ethanol extract of Calendula officinalis flowers (Co.Cr) was studied for its possible spasmolytic and spasmogenic effects in isolated gut preparations. In rabbit jejunum, Co.Cr caused a dose-dependent (0.03-3.0 mg/mL) relaxation of spontaneous and K+-induced contractions, suggestive of calcium channel blockade (CCB). In a few preparations, a mild non-reproducible spasmogenic effect was observed at lower doses, followed by relaxation. The CCB effect was confirmed when pretreatment of the jejunum preparations with Co.Cr produced a dose-dependent rightward shift in the Ca(++) dose-response curves, similar to that of verapamil. Activity-directed fractionation revealed that the spasmolytic activity of the plant was concentrated in its organic fractions. The aqueous fraction exhibited a marked atropine sensitive spasmogenic effect but was found to be devoid of any spasmolytic effect. These data indicate that the crude extract of Calendula officinalis flowers contains both spasmolytic and spasmogenic constituents, exhibiting these effects through calcium channel blocking and cholinergic activities and this study provides a scientific base for its traditional use in abdominal cramps and constipation.