Antidiarrheal effect of fractions from stem bark of Thespesia populnea in rodents: Possible antimotility and antisecretory mechanisms

Abstract

Objective To evaluate antidiarrheal activity of the fractions of aqueous extract from stem barks of Thespesia populnea (Malvaceae). Methods From the aqueous extract three fractions namely ethyl acetate fraction (EAF), methanolic fraction (MF) and residue fraction (RF) were made and studied for antidiarrheal activity. Antidiarrheal activity of the fractions were evaluated in castor oil induced diarrhea, prostaglandin E 2 (PG-E 2) induced diarrhea and charcoal meal test as in vivo models and the most potent fraction was further evaluated with in vitro models to determine the possible antimotility effect. Results In castor oil induced diarrhea model, the RF (10, 25, 50 and 100 mg/kg, po.) and MF (100 mg/kg, po.) has significantly reduced the cumulative wet faecal mass, where as the EAF have not shown any significant antidiarrheal activity, RF was found to be more potent than MF. Based on these results and percentage yield, only RF was evaluated in PG-E 2 induced enteropooling and charcoal meal test. RF (10, 25 and 50 mg/kg) had shown significant inhibition of PG-E 2 induced secretions (antisecretory) and decreased the movement of charcoal in charcoal meal test indicating its antimotility activity. Furthermore, RF has showed significant inhibition of acetylcholine, histamine and BaCl 2 induced contractions on rat colon, guinea pig ileum and rabbit jejunum with EC 50 values of 241.7, 303.1 and 286.1 μg/mL, respectively indicating the antimotility effect of RF. The phytochemical analysis of RF showed presence of gums and mucilages and the possible mechanism may be the combination inhibition of elevated prostaglandin biosynthesis and reduced propulsive movement of the intestine. Conclusions RF possesses good antidiarrheal activity comparing with other two fractions and the possible mechanism thought to be associated with combination of antisecretory and antimolity.