Evaluation of Indigo Naturalis Prepared Using a Novel Method: Therapeutic Effects on Experimental Ulcerative Colitis in Mice

<b>Background/Objectives</b>: Indigo naturalis (IN) is a traditional Chinese medicine concocted from medicinal plants such as <i>Baphicacanthus cusia</i> (Nees) Bremek. IN has multifaceted pharmacological activities. Recent research highlights the remarkable efficacy of IN in treating ulcerative colitis (UC). This study investigates the efficacy of Indigo Naturalis prepared using a novel method (NIN) in ameliorating UC. <b>Methods</b>: We have developed a new IN processing technology without the use of lime. Correspondingly, the content of active ingredients has relatively increased in NIN. In this study, dextran sulfate sodium salt (DSS) induced UC models among male KM mice, and the protective effects of NIN on UC were verified. <b>Results</b>: NIN could significantly improve weight loss, diarrhea and prolapse, bloody stools, elevated Disease Activity Index (DAI) and alleviate the colitis symptoms of mice; it could also improve the shortening of colon, disappearance of intestinal crypts, epithelial cell destruction and inflammatory infiltration caused by UC; and it could also significantly reduce the Histological Index (HI). In addition, NIN relieved the inflammatory response by decreasing the content of pro-inflammatory cytokines TNF-α and IL-1β and elevating the content of anti-inflammatory cytokines IL-10 and IL-22. It also restored the intestinal mucosal barrier by increasing the level of MUC2 protein expression at the site of colonic injury. <b>Conclusions</b>: The significant effects of NIN on UC were verified for the first time, suggesting that NIN was worth further developing into a novel therapeutic drug and, necessarily, further safety evaluations and comparisons with traditional IN will help in the application of NIN.