Protective effect of freeze-dried extract of Persicaria bistorta Samp. on acetic acid-induced colitis model in rats: Involvement of nitric oxide and opioid system.

Inflammatory bowel disease is a chronic inflammatory disorder accompanied by occasional flare-ups, abdominal pain, and rectal bleeding. Persicaria bistorta Samp. is a medicinal plant repeatedly mentioned in traditional Persian medicine for the treatment of bleeding and tissue damage in different organs, including the intestines. The current study aimed to evaluate the effect of bistort root in an animal model of colitis. Freeze-dried aqueous extract of the plant (PB) was prepared and analyzed using liquid chromatography-mass spectrometry and high-performance liquid chromatography. The anti-inflammatory effect of oral PB (300, 500, and 700 mg/kg) was evaluated in acetic acid-induced colitis in Wistar rats compared with negative control and positive control (dexamethasone). The role of nitric oxide (NO), opioid receptors, Toll-like receptors (TLR-4), interleukin (IL)-1β, IL-6, TNF-α, NF-κB, myeloperoxidase, and intestinal tissue damage using immunohistochemistry staining for cyclooxygenase-2 (COX-2) were also assessed. A total of 29 compounds were identified in the extract. The gallic acid content of the extract was 4.973 ± 1.102 mg/g. PB significantly ameliorated the gross morphological damage from 4.66 ± 0.577 in negative control to 1.33 ± 0.56 in PB 700 (p < 0.001). Also, PB 700 lowered the levels of TNF-α (p < 0.01), TLR-4 (p < 0.001), NF-κB (p < 0.0001), IL-1β (p < 0.0001), and IL-6 (p < 0.0001) compared to the negative control. Additionally, while blocking NO and opioid pathways, the therapeutic effect of the extract was not significant, compared to the negative control, suggesting that PB 700 has exerted its therapeutic effect via these two pathways. However, further mechanistic and clinical studies are recommended to confirm PB as a natural treatment for colitis.