Anti-Inflammatory Effects of Triterpenoids; Naturally Occurring and Synthetic Agents

Evidence suggests that discovery of anti-inflammatory agents is driven by the search for bioactive compounds from natural products and synthetic chemicals. Triterpenoids are a wide-spread group of natural products and a polycyclic secondary metabolite in many terrestrial plants. In addition, their anti-inflammatory activity and action as immunomodulators has been demonstrated in many studies. Because of their various advantages, triterpenoids are used as a platform or target of drug development in wide-range applications against inflammatory diseases. Therefore, the modification of a variety of triterpenoids in structure from the natural origin has been done for optimization of bioactivity, and some semisynthetic analogs are suggested to be potent anti-inflammatory triterpenoids. The aim of this review is to illustrate the anti-inflammatory effects of several triterpenoids originating from natural products and chemical synthesis, and to analyze the structural activities and relationships between the different types of triterpenoids. These triterpenoids include avicins, boswellic acid, celastrol, diosgenin, escin, ginsenosides, glycyrrhizin, lupeol, oleanolic acid, platycodon D, saikosaponins, ursolic acid, 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO), and their derivatives. This review provides a summary of recent advances of treiterpenoids and discusses further advances on the anti-inflammatory effect.