Effects of aqueous extracts from Ceratonia siliqua L. pods on small intestinal motility in rats and jejunal permeability in mice

Abstract

The current study was performed to assess the effects of carob pod aqueous extracts (CPAE, pulp, seeds or mixture) on gastrointestinal transit (GIT) and intestinal epithelium permeability. In this aspect, male rats fasted for 16 hours were used and given by oral administration NaCl (0.9%, control group) or various doses of CPAE (50, 100 and 200 mg kg⁻¹, b.w.). Two other groups of rats (batch tests) received clonidine (an alpha-2 adrenergic agonist, 1 mg kg⁻¹) or yohimbine (an alpha-2 adrenergic antagonist, 2 mg kg⁻¹). Two hours later, all animals were given a test meal containing charcoal and gum arabic in water. 30 minutes later, rats were anesthetized, a laparotomy was performed and the distance traveled by the meal compared to the total length of the small intestine was measured. Regarding the effect of CPAE on diarrhoea, the extract was administered orally to three groups of rats (ten in each group). Two other groups received normal saline (10 mL kg⁻¹) and loperamide (10 mg kg⁻¹) as a negative and standard group. Compared with the control group, the animals treated with the CPAE of pulp, seeds or a mixture (50% pulp and 50% seeds) of mature carob, showed a significant increase (3–25%) of GIT in a dose-dependent manner. By contrast, the CPAE of immature carob pods significantly and dose dependently decreased (3–19%) the GIT and diarrhoea (66–87%). However, clonidine and yohimbine respectively decreased (58%) and increased (30%) the GIT. More importantly, using the Ussing chamber system, we found that aqueous extracts of mature and immature carob pods significantly and dose-dependently increased or decreased intestinal epithelium permeability. The results indicate that carob possesses significant laxative and anti-diarrheal activities due to its opposite effects both on gastrointestinal propulsion and permeability. These findings confirm that the degree of maturity of carob characterized by a different phytochemical composition may be responsible for these actions.