Effects of Hypericum perforatum extract on rat irritable bowel syndrome

In irritable bowel syndrome (IBS), disturbance of bowel motility is associated with infiltration of inflammatory mediators and cytokines into the intestine, such as neutrophils, myeloperoxidase (MPO), tumor necrosis factor alfa (TNF-α), and lipid peroxide.

Regarding promising anti-inflammatory and anti-oxidative effects of Hypericum perforatum (HP) extract, besides its anti-depressant effect, this study was designed to evaluate the effects of HP in an experimental model of IBS.

IBS was induced by a 5-day restraint stress in rats. The HP extract was administered by gavage in doses of 150, 300, and 450 mg/kg for 26 days. Fluoxetine and loperamide were used as positive controls. Gastric emptying and small bowel and colon transit, besides the levels of TNF-α, MPO, lipid peroxidation, and antioxidant power, were determined in colon homogenates.

Data were analyzed by one-way ANOVA followed by Tukey's post hoc test for multiple comparisons.

A significant reduction in small bowel and colonic transit (450 mg/kg), TNF-α, MPO, and lipid peroxidation and an increase in antioxidant power in all HP-treated groups (150, 300, and 450 mg/kg) were seen as compared with the control group. Gastric emptying did not alter significantly when compared with the control group. Treatment with loperamide (10 mg/kg) significantly inhibited gastric emptying and small bowel and colonic transit, while flouxetine (10 mg/kg) decreased gastric emptying, TNF-α, MPO, and lipid peroxidation and increased the antioxidant power of the samples in comparison with the control group.

HP diminished the recruitment of inflammatory cells and TNF-α following restraint stress not in a dose-dependent manner, possibly via inhibition of MPO activity and increasing colon antioxidant power, without any difference with fluoxetine. The HP extract inhibits small bowel and colonic transit acceleration like loperamide but has minimal effect on gastric emptying.