Polyphenol-rich extract of Ocimum gratissimum leaves ameliorates colitis via attenuating colonic mucosa injury and regulating pro-inflammatory cytokines production and oxidative stress

Colitis is a chronic inflammation and ulcer on the inner lining of the large intestine. For many centuries Ocimum gratissimum (OG) leaves have been used in folk medicine in Nigeria to treat inflammatory bowel diseases, however, to date, the anti-colitis effects of OG have not been scientifically proven. In this study we investigated the effects of polyphenol rich extract of Ocimum gratissimum (PREOG) leaf on colonic mucosa injury in colitis, its mechanisms, initial administration time and dosage. Dextran sodium sulfate (DSS)-induced rat colitis models was used. PREOG administration was initiated at 3 and 7 d after the model was established at doses of 200, 400 and 800 mg/kg for 7 d. 5-aminosalicylic acid (5-ASA) was used as a reference drug. The disease activity index (DAI), vascular permeability, markers of oxidative stress, granulocyte infiltration, inflammation and histopathological alteration were evaluated. Obvious colonic inflammation and mucosa injuries were observed in DSS-induced colitis groups. PREOG administration promoted repair of colonic mucosa injuries, attenuated inflammation, and decreased DAI scores in rats with colitis. PREOG also decreased the plasma concentrations of Interleukin-(IL)-6 and tumor necrosis factor (TNF)-alpha, and concentrations of myeloperoxidase, nitric oxide, cyclooxygenase-2 and malondialdehyde in the colon, and increased the plasma concentrations of IL-4 and IL-10 as well as the concentration of superoxide dismutase, catalase and reduced glutathione in the colon. The efficacy of PREOG was dosage dependent. In conclusion, OG repairs colonic mucosa injury in experimental colitis through its ant-inflammatory and ant-oxidant. Its efficacy related to initial administration time and dose.