Background: The effect of spices on gastric acid secretion is variable. Their mechanism of action is also not well established.
Aim: To study the effect of spices on gastric acid secretion in anesthetized rats.
Methods: Aqueous extracts (10% w/v) of red pepper (Capsicum annuum), fennel (Foeniculum vulgare), omum/ajwan (Carum copticum), cardamom (Elettaria cardamomum), black pepper (Piper nigrum), cumin (Cuminum cyminum) and coriander (Coriandrum sativum) were prepared. The stomach of pentobarbitone-anesthetized rats was perfused at 0.15 mL/min with aqueous extracts of spice or acetylcholine (1 microgram/mL or 10 micrograms/mL solutions, in 40 min blocks, twice in each experiment bracketed by saline perfusions. The acid content in the samples was estimated by titration with 0.1N NaOH with phenolphthalein as indicator. Atropine 1 microgram/mL was added to the perfusion fluid in 28 experiments. In 32, acute gastric mucosal injury was induced by leaving aspirin 125 mg/Kg in the stomach for 2 h before perfusion.
Results: All the spices tested increased acid secretion in the following declining order: red pepper, fennel, omum, cardamom, black pepper, cumin, coriander. Red pepper increased acid secretion (mean [SEM] 0.93 [0.16] mL 0.1N HCl) to about 7 times the basal secretion (0.14 [0.05]; p < 0.005). The increase in acid secretion by the other spices was as follows: fennel 0.42 (0.11) mL 0.1 N HCl from basal secretion (0.12 [0.03]) (p < 0.02); omum 0.33 (0.05) from 0.09 (0.02) (p < 0.01); cardamom 0.28 (0.04) from 0.10 (0.03) (p < 0.005); black pepper 0.19 (0.03) from 0.04 (0.01) (p < 0.005); cumin 0.12 (0.02) from 0.08 (0.01) (p < 0.05); coriander 0.18 (0.03) from 0.09 (0.02) (p < 0.005). Atropine abolished the acid secretion induced by acetylcholine and significantly reduced acid induction by red pepper, omum and coriander, but not that by fennel. In experiments with aspirin-induced mucosal injury the basal acid secretion was low; acid secretion by red pepper and fennel was reduced significantly, but not that by acetylcholine. Cumin and coriander increased acid secretion in injured stomachs.
Conclusion: The spices tested increased gastric acid secretion, in some by a cholinergic mechanism but by other mechanism(s) as well. Red pepper produced maximum increase in acid secretion, but this was significantly reduced in injured stomachs. Cumin and coriander increased gastric secretion in injured stomachs.