Effect of Aframomum melegueta seed extract on castor oil-induced diarrhea

ABSTRACT 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.