The anti-diabetic activity of licorice, a widely used Chinese herb

Ethnopharmacological relevance: A great deal of valuable experience has been accumulated in the traditional Chinese medicine (TCM) system for the treatment of Xiaoke disease which is known as diabetes mellitus now. As the most-commonly used Chinese herb, licorice has been used in TCM for more than two thousand years. It is often used in combination with other herbs to treat metabolic disorders, especially diabetes mellitus. Aim of the study: To summarize the characteristics, mechanisms, and clinical use of licorice and its active components for treating diabetes mellitus. Methods: PubMed, Web of Science, Research Gate, Science Direct, Google Scholar, and Academic Journals were used as information sources by the inclusion of the search terms 'diabetes', 'licorice', 'licorice extracts', 'flavonoids', 'triterpenoids', and their combinations, mainly from 2005 to 2019. Results: Licorice extracts, five flavonoids and three triterpenoids isolated from licorice possess great antidiabetic activities in vivo and in vitro. This was done by several mechanisms such as increasing the appetency and sensitivity of insulin receptor site to insulin, enhancing the use of glucose in different tissues and organs, clearing away the free radicals and resist peroxidation, correcting the metabolic disorder of lipid and protein, and improving microcirculation in the body. Multiple signaling pathways, including the PI3K/Akt, AMPK, AGE-RAGE, MAPK, NF-KB, and NLRP3 signaling pathways, are targets of the licorice compounds. Conclusion: Licorice and its metabolites have a great therapeutic potential for the treatment of diabetes mellitus. However, a better understanding of their pharmacological mechanisms is needed for evaluating its efficacy and safety.