Usnic Acid as a Potential Therapeutic Agent for Ulcerative Colitis: Anti-Inflammatory, Antioxidant and Intestinal Barrier-Protective Properties

Ulcerative Colitis (UC) is a chronic, relapsing disease that includes mucosal inflammation, abnormal immune response and oxidative stress. There are a number of therapeutic strategies for the treatment of UC, which include amino salicylates, corticosteroids, immunomodulatory agents, biologicals, and small molecule drugs; however, therapy resistance, recurrence and adverse effects resulting from prolonged use still pose a challenge. In this regard, it becomes essential to discover new drugs that possess both anti-inflammatory and antioxidative properties. Usnic acid is a dibenzofuran compound isolated mainly from lichens that has drawn a lot of interest owing to its various pharmacological activities. This review highlights the use of usnic acid in ulcerative colitis treatment, specifically discussing its origin, chemical structure, pharmacological actions, mechanism of action and safety. Its anti-inflammatory activity has been proved by experimental studies on the modulation of inflammatory mediators, which include TNF-α, IL-1β, IL-6, NO, and inflammatory signalling pathways such as NF-κB and TLR4. The antioxidant property is due to the enhancement of SOD and GSH activity, and reduction of MDA, MPO and lipid hydroperoxides levels. Moreover, its immunomodulatory actions and protective effects on the intestinal barrier have been considered. However, incomplete data on its pharmacokinetics, insufficient experimental results related to disease-specificity and problems with the toxicity especially hepatotoxicity are the main challenges. It is necessary to carry out additional research to confirm its therapeutic effectiveness, mechanism of action, optimum dose and safety profile. In general, usnic acid is a perspective bioactive natural compound that can be used to develop new therapeutic approaches for ulcerative colitis.