Diterpenoids from aerial parts of Flickingeria fimbriata and their nuclear factor-kappaB inhibitory activities.

Chemical investigation of the aerial parts of Flickingeria fimbriata (Bl.) Hawkes resulted in isolation of sixteen ent-pimarane diterpenoids, including five rare 16-nor-ent-pimarane diterpenoids, two 15,16-dinor-ent-pimarane diterpenoids and one ent-pimarane diterpenoid. Structures were mainly elucidated by extensive spectroscopic analysis, and their absolute configurations were unequivocally determined by the exciton chirality method, the modified Mosher's method, the CD experiments (including Snatzke's method) and chemical transformations, respectively. All the isolated compounds were screened for inhibitory effects on the nuclear factor-kappaB (NF-κB) in lipopolysaccharide (LPS) induced murine macrophage RAW264.7 cells, using a NF-κB-dependent luciferase reporter gene assay. Several of these compounds displayed comparable or even better activities than the positive control pyrrolidinedithiocarbamate (PDTC) (IC50=26.3 μM) with IC50 values in the range of 14.7-29.2 μM and structure-activity relationships are briefly proposed.