Gastrointestinal effects of Syzigium aromaticum (L) Merr. & Perry (Myrtaceae) in animal models

Gastrointestinal disorders constitute one of the most common diseases world-wide and the treatment of some of them has since constituted a great challenge to health workers, which therefore calls for an urgent search into newer agents. In recent years, several efforts have been made through series of investigations on natural resources.

The plant Syzigium aromaticum (SYZ), commonly known as clove has since been employed locally to treat constipation. Attempt to complement the effort of other researchers called for its selection for laboratory investigation, in order to determine its possible effect on intestinal propulsion in rodents as well as its suspected gastrointestinal protective properties.

SYZ hot aqueous extract was investigated using selected doses in the various study models. Effect of the decoction on intestinal propulsion was studied by administering 300 and 700 mg kg(-1) hot extract to groups of overnight fasted mice, while using charcoal meal as a marker. The effect of the herbal drug was compared with other standard drugs and antagonists. In the same vein, the same doses of the extract were administered orally to groups of overnight fasted rats prior to challenge with different necrotizing agents-absolute ethanol (1 ml/rat), indomethacin (30 mg kg(-1)) and 70% ethanol in 150 mM HCl (1 ml/rat). Both negative and positive controls were similarly treated simultaneously with distilled water (10 ml kg(-1)) and standard antiulcer drugs (omeprazole 20.0 mg kg(-1), cimetidine 100.0 mg kg(-1) and misoprostol 0.2 mg kg(-1)), respectively. Lastly, the effect of SYZ was investigated on a segment of isolated rabbit ileum and subsequently compared with acetylcholine 5.5 x 10(-5) M. The effects of atropine (3.4 x 10(-6) M and 3.4 x 10(-5) M) on SYZ were also studied.

The extract was found to increase the gut muscle propulsion similar to the standard drugs-carbachol and metoclopramide. When used together with atropine, SYZ produced a reduction in intestinal propulsion which suggested the involvement of cholinergic mechanisms in the action of the extract. In the ulcer models, the decoction reduced the ulcer number and ulcer area in the ethanol and HCl-ethanol models, with significant respective ulcer indices of 2.80 +/- 3.51 and 11.4 +/- 3.79 compared with controls (p < 0.05). In the indomethacin model, the extract, 700 mg kg(-1), compared favourably with misoprostol with an index of 0.20 +/- 0.11 which was also found to be significant compared with the control. In the in-vitro investigation on the rabbit ileum SYZ (200-6400 microg ml(-1)) contracted the tissue in a dose-dependent fashion but it was found to be less effective than acetylcholine (5.5 x 10(-5) M). Atropine sulphate 3.4 x 10(-6) M and 3.4 x 10(-5) M reduced gut contractility induced by SYZ, similar to the in-vivo observation. The latter could substantiate the earlier speculation of the herbal drug exerting its effect via cholinergic mechanism apart from the diverse possible activities of the various bioactive components that were identified through phytochemical testing of SYZ.

The present findings explain the folkloric uses of SYZ as an antiulcer and a purgative agent as well as its possible mechanism of action.