Semisynthesis and Kappa-Opioid Receptor Activity of Derivatives of Columbin, a Furanolactone Diterpene.

Columbin, a natural compound from plants used in traditional medicine, was modified to create derivatives that might activate the kappa-opioid receptor (KOR), a target for conditions like anxiety, depression, and addiction. The derivatives showed slightly improved activity at the KOR compared to the original columbin, but neither the parent compound nor its derivatives were potent KOR ligands. This study is the first to test columbin at the KOR and explores chemical modifications that can be made to the columbin molecule.

Study at a glance

Abstract

Columbin (1) is a furanolactone diterpene isolated from the roots of Jateorhiza and Tinospora species. These species generally grow in Asia and Africa and have been used in folk medicine for their apparent analgesic and antipyretic activities. Columbin (1) is of particular interest due to its structural similarity to the known kappa-opioid receptor (KOR) agonist salvinorin A. Given that the KOR is of interest in the study of many serious diseases, such as anxiety, depression, and drug addiction, obtaining natural or semisynthetic molecules with KOR activity recently has gained much interest. For this reason, in the present study, derivatives of 1 were designed and synthesized using known structure-activity relationships of salvinorin A at KORs. The structures of the columbin analogues prepared were elucidated by NMR spectroscopy and mass spectroscopy, and their KOR activity was investigated in vitro by inhibition of forskolin-induced cAMP accumulation. Slight improvements in KOR activity were observed in columbin derivatives over their parent compound. However, despite the structural similarities to salvinorin A, neither columbin (1) nor its derivatives were potent KOR ligands. This work represents not only the first evaluation of columbin (1) at the KOR but also one of the first works to explore synthetic strategies that are tolerated on the columbin core.