Studies on antidiarrheal and laxative activities of aqueous-ethanol extract of Asphodelus tenuifolius and underlying mechanisms

Abstract

Background: Asphodelus tenuifolius Cav. (Asphodelaceae) has traditional reputability in treatment of diarrhea and constipation but no scientific study has been reported for its gastrointestinal effects. Present study was conducted to evaluate antidiarrheal and laxative activities of the plant. Methods: Aqueous-ethanol crude extract of Asphodelus tenuifolius (At.Cr) was subjected to phytochemical screening and liquid-liquid fractionation. In vivo studies of charcoal meal intestinal transit test, antidiarrheal activity against castor oil induced diarrhea and laxative activity were performed in mice. In vitro experiments were conducted upon rabbit jejunum preparations using standard tissue bath techniques. Results: Phytochemical screening indicated presence of alkaloids, anthraquinones, flavonoids, saponins, steroids, tannins and phenols in At.Cr. In charcoal meal intestinal transit test, At.Cr increased (p < 0.001) intestinal motility at 100 mg/kg dose, but decreased (p < 0.001) it at 500 mg/kg dose, when compared to the control group. At.Cr (300-700 mg/kg) provided protection from castor oil induced diarrhea in mice, which was significant (p < 0.001) at 500 and 700 mg/kg doses, as compared to the saline treated control group. At.Cr (50 and 100 mg/kg) enhanced total and wet feces counts in normal mice, as compared to saline treated control. In jejunum preparations, At.Cr inhibited spontaneous, K+ (80 mM) and K+ (25 mM) mediated contractions, similar to verapamil. Pre-incubation of jejunum preparations with At.Cr resulted in rightward nonparallel shift in Ca+ 2 concentration response curves, similar to verapamil. The spasmolytic activity was concentrated in ethylacetate fraction. Aqueous fraction exhibited spasmogenicity upon spontaneous contractions, which was blocked in presence of verapamil, but remained unaffected by other tested antagonists. Conclusion: The Asphodelus tenuifolius crude extract possesses gut modulatory activity, which may normalize gut functions in diarrhea and constipation. The spasmolytic activity of the extract was found to be mediated through Ca+ 2 channel blocking action. The spasmogenic activity, found partitioned in aqueous fraction, possibly involves Ca+ 2 influx through voltage gated Ca+ 2 channels. The study supports ethnic uses of the plant in diarrhea and constipation.