Labdane diterpenoids as potential anti-inflammatory agents

The search for new anti-inflammatory agents is challenging due to the complexity of the inflammatory process and its role in host defense. Over the past few decades, a significant body of evidence has emerged, supporting the prominent role of labdane diterpenoids in therapeutic interventions of various inflammatory diseases. The anti-inflammatory activity of labdane diterpenoids has been attributed mainly to the inhibition of nuclear factor-κB (NF-κB) activity, the modulation of arachidonic acid (AA) metabolism and the reduction of nitric oxide (NO) production. This article provides extensive coverage of naturally occurring labdane diterpenes, discovered between 1981 and 2016, which have been verified as NF-κB, NO, or AA modulators. Herein, we also discuss the role of Michael acceptor, a common structural feature present in most of the active labdane diterpenes, and its association with NF-κB signaling inhibition. In the cases where a sufficient amount of data exists, structure-activity relationship (SAR) studies and clinical studies performed on the anti-inflammatory labdane diterpenoids are also discussed.