Effect of Aframomum melegueta. Seed Extract on Castor Oil-Induced Diarrhea

The effect of the aqueous (aq) seed extract of Aframomum melegueta. K. Schum. (Zingiberaceae) on castor oil-induced diarrhea, intestinal fluid secretion, and gastrointestinal transit was investigated in the study. Castor oil (10 ml/kg, p.o.) induced copious diarrhea in all rats 3 h after treatment. Furthermore, it produced a significant increase in the volume of intestinal fluid secretion in rats and also enhanced intestinal transit in mice. The aq seed extract of A. melegueta. (100-500 mg/kg, p.o.) offered significant protection against diarrhea induced by the oil. At a dose range of 250-500 mg/kg, the extract reduced significantly the volume of fluid secretion in castor oil-treated rats. At these doses, it also demonstrated a significant antitransit activity in a dose-related manner. Acetylsalicylic acid (100 mg/kg, p.o.) delayed diarrhea and reduced the number of animals with diarrheal droppings to 20%. At the same dose level, acetylsalicylic acid reduced significantly the volume of intestinal fluid secretion but lacked antitransit property in castor oil-treated animals. N.-Nitro-L-arginine methyl ester (L-NAME) (2.5-10 mg/kg, i.p.) dose-dependently reduced the number of animals with diarrhea. At 50 mg/kg i.p., it offered 100% protection against diarrhea induced by the oil. Furthermore, L-NAME (10 mg/kg, i.p.) significantly inhibited both the intestinal fluid secretion and gastrointestinal transit induced by castor oil. However, L-NAME (10 mg/kg, i.p.) did not significantly modify the antidiarrheal effect of A. melegueta.. L-Arginine, a substrate of nitric oxide synthase or isosorbide dinitrate, a nitric oxide donor, did not alter the effect of A. melegueta. on diarrhea. Ascorbic acid (100 mg/kg, p.o.) and α.-tocopherol (20 mg/kg, p.o.) reduced the number of animals with diarrhea to 80% and 70%, respectively. However, they both lacked significant activities on intestinal fluid secretion and gastrointestinal transit induced by castor oil. The combination of ascorbic acid (100 mg/kg, p.o.) or α.-tocopherol (20 mg/kg, p.o.) with A. melegueta. (500 mg/kg) offered higher protection against diarrhea than the extract alone. Considering these results together, it may be inferred that Aframomum melegueta. seed extract may be a useful antidiarrheal agent.