Abstract

Objective: To investigate the effect of crude methanolic extract of Combretum racemosum (C. racemosum) leaves on histamine-stimulated gastric secretion in rats. Methods: Phytochemical and acute toxicity tests were performed. Anti-secretory activity of C. racemosum extract was investigated in pyloric ligated rats administered histamine. Gastric juice was collected from all the animals and the volume, titratable acidity, pH and mucus content were measured. The effect of C. racemosum extract on calcium chloride induced contractions of the guinea-pig ileum suspended in high potassium, calcium-deficient depolarizing solution was investigated. The H2 receptor antagonistic potency was also evaluated using the isolated non-gravid rat uterus. Results: Phytochemistry revealed the presence of abundant amounts of saponins and moderate amounts of glycosides, terpenoids, proteins, reducing sugar, resins, alkaloids, flavonoids and carbohydrates. The oral LD50 of the extract was greater than 8 000 mg/kg body weight in mice. Pretreatment of pyloric ligated rats with C. racemosum prior to histamine administration significantly reduced (P < 0.001) the volume of gastric juice and titratable acidity, and significantly increased (P < 0.001) gastric pH and gastric mucus when compared to the negative control. Both doses of C. racemosum protected rats significantly (P < 0.001) from histamine-induced ulceration. C. racemosum potently inhibited contractions evoked by calcium chloride in a dose-dependent and reversible manner with an IC50 of 1 132 µg/mL. It also antagonized the relaxant effect of histamine on the isolated rat uterus in a manner comparable to cimetidine. Conclusions: The leaves of C. racemosum possess gastric anti-secretory and anti-ulcer effects and justify its use in traditional medicine in South-East Nigeria for the treatment of peptic ulcer disease.

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