Ethnopharmacological relevance: Plantago major (P. major) has traditionally been used in Iranian Persian medicine to treat gastrointestinal ulcers and bleeding. Research objectives: This study aimed to investigate the anti-inflammatory effects of the leaf and seed extracts of P. major in rats with acetic acid-induced ulcerative colitis (UC). Materials and methods: To this end, 49 rats were randomly divided into seven groups. UC was induced in all groups but the control (vehicle) group using a single intra-rectal administration of 2 ml of 4% acetic acid. Other groups received daily intraperitoneal (i.p.) injections of the seed extract of P. major (400 mg/kg and 700 mg/kg), the leaf extract of P. major (400 mg/kg and 700 mg/kg), and sulfasalazine (400 mg/kg) for seven consecutive days, respectively. The rats’ rectum was surgically removed and evaluated for macroscopic and microscopic damage. The tissue levels of oxidative stress and inflammatory markers were measured using the ELISA method. Results: The high-dose leaf extract significantly decreased ulcer index and histopathologic damage as well as the tissue levels of IL-6, TNF-α, PGE2, IL-1β, MPO, and MDA compared to the damage group. The low-dose leaf extract also significantly reduced the levels of some markers. The seed extract in the two used doses caused a modest decrease in the histopathological damages and ulcer index. Conclusions: P. major leaf extract effectively reduces inflammation and mucosal damage in rats with UC, especially when administered in high doses. P. major seed extract has minimal protective effects on UC.
