Luem pua rice extract attenuates the severity of dextran sulfate sodium-induced ulcerative colitis in rats through cholinomimetic effects

Abstract

Objective: The objective of the study was to investigate the effect of aqueous extract of unpolished dark purple glutinous Thai rice variety Luem Pua (LP) in dextran sulfate sodium (DSS)-induced ulcerative colitis (UC) in rat and the possible cholinomimetic effects of the extract. Methods: The effect of LP extract (0.5, 1, or 1.5 mg/ml final concentration) on ileum contraction was tested using isolated guinea pig ileum. Certain agonists (acetylcholine, tetramethylammonium, and clonidine) and antagonists (hexamethonium chloride and atropine) were studied to determine the cholinomimetic effect of the extract. The effects of LP extract (5 g/kg/day) in DSS-induced UC model (drinking water was replaced with 3% DSS in water for 7 days) in rat were evaluated. On each day of treatment, the change of disease activity index (DAI) was recorded. At the end of the experiments, rats were terminated and disease severity expressed as DAI, colon length, and spleen weight were determined. Results: LP extract at the concentration of 0.5, 1, and 1.5 mg/ml (final concentration) could contract the ileum in a dose-dependent manner and be blocked completely by atropine. Oral administration of LP extract could significantly attenuate the severity of DSS-induced UC as seen by the reduction of DAI, colon length, and spleen weight. Conclusion: Results in isolated guinea pig ileum suggest that LP might contain active substance that could activate muscarinic receptors. In addition to antioxidant activity, through activation of muscarinic receptor, might explain the protective effects of LP extract against DSS-induced UC in rats.