Effects of Methanol Extract from the Peel of Red Onion (<i>Allium cepa</i> L.) on Ulcerative Colitis Induced by Acetic Acid in Wistar Rats

Abstract

Background: Ulcerative colitis (UC) is a type of inflammatory bowel disease (IBD). The urgent need to discover new medicines for the treatment of UC has led to a substantial amount of research annually. Objectives: This study aimed to explore the potential beneficial effects of Allium cepa L. peel methanolic extract (ACPME) on experimental ulcerative colitis in rats. Methods: The extraction of red onion peel (Allium cepa) was performed using the percolation method. Total flavonoid and phenolic contents were determined using aluminum chloride and Folin-Ciocalteu techniques, respectively. Ulcerative colitis was induced by intrarectal administration of 2 mL of 3% acetic acid. The animals were divided into six groups: The normal group, the colitis control group, groups treated with ACPME (50, 100, and 150 mg/kg body weight; 4 days of treatment), and the group treated with dexamethasone (1 mg/kg). Macroscopic, histological, and biochemical evaluations (MPO, IL-6, IL-1 beta, and TNF-alpha) were conducted on distal colon samples to assess the extract's efficacy. Results: The total phenolic content of the extract was 223.38 ± 0.002 mg of gallic acid equivalent per gram of dry extract, while the total flavonoid content was 49.42 ± 0.008 mg of quercetin equivalent per gram of extract. Compared to the colitis control group, ACPME administration (50 and 100 mg/kg) significantly reduced macroscopic and microscopic colon damage, pro-inflammatory cytokine levels, and MPO activity in colon samples. Conclusions: The present study demonstrated that ACPME could have a beneficial impact on experimental colitis. This effect may be partly due to modulating neutrophil infiltration and pro-inflammatory cytokines such as IL-6, IL-1 beta, and TNF-alpha. However, further research is required to substantiate these effects.