Freeze-dried aqueous extracts (AEs, 0.1-1g/kg body wt., p.o.) obtained from entire or selected parts of Stachytarpheta cayennensis were tested for their effects on gastric secretion, gastric motility,
inflammation and
pain in rodents, with the purpose of validating the plant's ethnomedical uses. The AE-Total, AE-Flowers and AE-Leaves but not AE-Stems inhibited the gastric acid secretion in pylorus-ligated rats with varying potency. Purification of AEs yielded the semipurifed fractions EtFs rich in
iridoids. All the EtFs with exception of EtF-Stems inhibited gastric acid secretion of pylorus ligated mice. While AE-Total stimulated the intestinal transit of mice by 43%, AE-Leaves delayed it by 38%. These effects on intestinal transit were not observed when the EtFs were tested. Only AE-Leaves and AE-Flowers altered the gastric emptying of semisolids, increasing it by 45% and 69%, respectively. These results indicate that the compounds related to inhibition of gastric acid secretion and gastrointestinal motility are different. The AE-Total reduced abdominal writhing induced by
acetic acid potently (ED50 value = 700 mg/kg, p. o.) without altering the writhes induced by
acetylcholine. Attempts to identify the mechanism of
analgesia were unsuccessful since the AE-Total did not show
analgesic effects when tested in different models of
pain such as
formalin and
capsaicin or the tail-flick test. Pretreatment of animals with AE-Total did not show antiinflammatory activity in any of the acute (paw
edema induced by
carrageenin,
dextran or
histamine,
pleurisy induced by
carrageenin and
capsaicin-induced mouse ear
edema) or chronic (air pouch) models used. No toxic signs were observed after administration of the different extracts up to 2 g/kg body wt., p.o. Collectively, the results confirmed folk information indicating presence of
analgesic, mild
laxative and potent inhibition of gastric secretion activities in the aqueous extracts of S. cayennensis. The results do not, however confirm the folk use of the plant as an antiinflammatory medicine.