Models for Antidiarrheal Activity

The method described by Shoba and Thomas³² was followed for this study with slight modification. Thirty mice fasted for 12 hours were randomly allocated to 5 groups of 6 animals each. Group I (received distilled water 10 mL/kg) served as control group, group II received the standard drug loperamide 3 mg/kg orally, and groups III, IV, and V received the methanolic leaf extract of O. quadripartita at doses of 100, 200, and 400 mg/kg, respectively. The extract and the standard drug, loperamide were dissolved with distilled water and volume administered was 10 mL/kg for all mice. One hour after administration, all mice received 0.5 mL of castor oil by an oral gavage and then they were individually placed on the floor, which was covered with dry toner plain paper copier film (nonwetting transparent paper). The floor lining was changed each time the mouse defecated. During an observation period of 4 hours, the time of onset of diarrhea, the total number of fecal output (frequency of defecation), consistency of feces (wet and dry diarrheal drops) excreted by the mice were recorded and compared with the control group. The results were expressed as a percentage of inhibition of diarrhea:

The effect of the extract on inhibition of intraluminal fluid accumulation was determined by measuring the volume of fluid accumulated in intestine of mice. Thirty mice were fasted for 18 hours prior to experiment and divided into 5 groups of 6 mice each. Group I (negative control) were treated with 10 mL/kg distilled water. Group II were treated with standard drug (loperamide 3 mg/kg orally). Groups III, IV, and V were treated with the extract at doses of 100, 200, and 400 mg/kg, respectively. One hour later, all the mice were challenged with 0.5 mL of castor oil orally. After 1 hour, the mice were sacrificed, the pyloric and cecum ends of the small intestine were tied and the intestine was removed. The intestinal contents were expelled into a measuring cylinder and then the volume was measured. Then, the percentage inhibition was calculated.³⁰

Gastrointestinal motility test was evaluated according to the method described by Ezeja and Anaga.³³ Mice that were fasted for 18 hours were randomly assigned to 5 groups: group I received distilled water (10 mL/kg orally), group II received atropine sulfate (5 mg/kg intraperitoneally), and groups III, IV, and V received different dose of the extract at doses of 100, 200, and 400 mg/kg, respectively, 30 minutes before the administration of 0.5 mL of castor oil. Thirty minutes after the administration of castor oil, each mouse received 0.5 mL of 10% charcoal suspension in 5% of acacia gum by oral gavages. Thirty minutes later, mice were sacrificed, the abdomen opened, and small intestine was removed. Then the total length of small intestine was measured with a calibrated ruler. Thereafter, the distance covered by charcoal from the pylorus to the cecum was measured and expressed as a percentage of the overall length of the small intestine from where the percent inhibition of movement was calculated.

The in vivo antidiarrheal index (ADI in vivo) was then expressed according to the formula developed by Aye-Than et al³⁴:

where D freq is the delay in defecation time or diarrhea onset obtained from castor oil diarrhea test, G meq is the gut meal travel reduction (as % of control) obtained from charcoal meal test (% inhibition), and P freq is the purging frequency or reduction in the number of wet stools (as % of control) obtained from castor oil–induced diarrheal model (% inhibition of defecation).