Preclinical studies of licorice in ulcerative colitis: A systematic review with meta-analysis and network pharmacology

Ethnopharmacological relevance: Licorice, as a traditional Chinese herbal medicine, possessing the efficacies of invigorating spleen and replenishing qi, heat-clearing and detoxicating, phlegm-resolving and cough suppressant, relieving spasm and pain, and hamonizing actions of various medicines.

Aim of the study: The goal of this systematic review, which includes meta-analysis and network pharmacology in preclinical studies, is to investigate the multiple efficacies of licorice on ulcerative colitis (UC).

Materials and methods: We searched several databases, e.g., Web of Science, Elsevier ScienceDirect and PubMed until Januanry 2022 for literature collection, and the Review Manager 5.3 was used to analyze the data. To synthesize the retrieved data, the fixed and random-effects models were utilized, respectively, and network pharmacology was applied to confirm the mechanisms.

Results: Based on the result of meta-analysis, it suggested that the treatments of licorice extract and its active compounds showed strong therpeutic effects, which not only reflected the declining histological score, a index of the colitis severity [SMD = -2.86, 95% CI (-3.65, -2.08); P < 0.00001], but also reversed colonic shortness [WMD = 1.67, 95% CI (1.16, 2.19); P < 0.00001] between experimental UC model and licorice-treatment groups. In addition, it suggested the significant reduction of TNF-α level [SMD = -2.70, 95% CI (-3.23, -2.16); P < 0.00001], which acted as a crucial role in inflammatory response. Furthermore, from the results of network pharmacology, it indicated that anti-inflammation, anti-oxidative stress, immunomodulatory effect and microbiota homeostasis were the predominant therapeutic mechanisms of licorice extract and its active compounds treating UC.

Conclusion: This systematic review with meta-analysis and network pharmacology demonstrates an efficient role of licorice extract and its active compounds in preclinical studies of UC, which provides supporting evidence for clinical trial implementation. However, there exist some limitations, such as technique quality decificency, missed reports due to negative outcome, failure to calculate sample size, and the risk of bias.