An Overview of Structurally Modified Glycyrrhetinic Acid Derivatives as Antitumor Agents.

Glycyrrhetinic Acid (), a triterpenoid aglycone component of the natural product glycyrrhizinic acid, was found to possess remarkable anti-proliferative and apoptosis-inducing activity in various cancer cell lines. Though was not as active as other triterpenes, such as betulinic acid and oleanolic acid, it could trigger apoptosis in tumor cells and it can be obtained easily and cheaply, which has stimulated scientific interest in using as a scaffold to synthesize new antitumor agents. The structural modifications of reported in recent decades can be divided into four groups, which include structural modifications on ring-A, ring-C, ring-E and multiple ring modifications. The lack of a comprehensive and recent review on this topic prompted us to gather more new information. This overview is dedicated to summarizing and updating the structural modification of to improve its antitumor activity published between 2005 and 2016. We reviewed a total of 210 derivatives that we encountered and compiled the most active derivatives along with their activity profile in different series. Furthermore, the structure activity relationships of these derivatives are briefly discussed. The included information is expected to be of benefit to further studies of structural modifications of to enhance its antitumor activity.