Inhibition of gastric acid secretion by the aqueous extract and purified extracts of Stachytarpheta cayennensis.

Stachytarpheta cayennensis Schauer (Verbenaceae) is used in folk medicine to treat gastric and intestinal disturbances. The freeze-dried aqueous extract of the whole plant tested to rodents up to the dose of 2 g kg-1, p.o., did not produce signs of toxicity. The extract (0.5-2 g kg-1, p.o.) increased the intestinal motility and protected mice against ulcers induced by restraintin-cold, ethanol or indomethacin. Injected into the duodenal lumen the extract inhibited the basal acid secretion as well as that induced by histamine and bethanecol in pylorus-ligated mice. Partition of the aqueous extract in organic solvents yielded semipurified fractions whose antiacid activity guided further chemical purification. All the fractions were chromatographically characterized, the main substances in the active extract being flavonoids and amines; some substances were revealed only under UV light. The most purified active fraction obtained presented a specific activity 5-10 times higher than that detected in the original extract. Data from pharmacological studies indicate that the antiulcer activity of S. cayennensis is related to a specific inhibition of gastric acid secretion. Cholinergic and histaminergic stimulation of acid secretion were similarly reduced by the extracts suggesting inhibition of common steps in both pathways, possibly at the level of histamine release/H2 receptor interaction, or at the proton pump. Whatever the mechanisms involved, the present data confirm the plant effectiveness as antiacid/antiulcer and laxative.