BACKGROUND

Glycyrrhetinic acids (GAs) viz., 18β-glycyrrhetinic acid and 18α-glycyrrhetinic acid, are oleanane-type triterpenes having a carboxylic acid group at C-30, and are extracted from the Chines herbal medicine licorice (Glycyrrhiza uralensis). Although the pharmacological properties of GAs have long been known, attention to them has greatly increased in recent times due to their cytotoxic activity. Areas covered: This review represents the patents granted about natural and synthetic glycyrrhetinic acid analogs from January 2010 to December 2017, the advances made by research groups in conjunction with pharmaceutical companies in the discovery of new natural or synthetic glycyrrhetinic acid analogs. Expert opinion: GAs demonstrate excellent cytotoxic, antimicrobial, enzyme inhibitory, antiinflammatory, antioxidant, analgesic, and antiviral effects. It is interesting to note that the C-3(OH) and C30-CO2H functional groups make GAs very attractive lead structures for medicinal scientists since these functionalities allow the generation of further chemical diversity for improved pharmacological effects. Moreover, various GA analogues have been prepared via modification of the C30-CO2H. It is noteworthy that the C-30 amide of GA demonstrated better cytotoxic effects compared to the parent compounds. In addition, GAs have the capability to conjugate with other anticancer drugs or be converted into their halo or amino analogs which is expected to stimulate medicinal chemist to synthesize new lead compounds in cancer drug discovery.