Norditerpenoids from Flickingeria fimbriata and their inhibitory activities on nitric oxide and tumor necrosis factor-α production in mouse macrophages.

Bioassay-guided fractionation of the ethanolic extract of the leaves of Flickingeria flimbriata led to the isolation of two new degraded diterpenoids 1 and 2, a new ent-pimarane type diterpenoid 3, and four known steroids 4-7. The structures of 1-3 were elucidated by spectroscopic analysis, and their absolute configurations were determined by chemical methods, TDDFT quantum chemical calculations of ECD spectra, and CD exiton chirality method. Compounds 1 and 2, named flickinflimilins A and B, possess a rare 15,16-dinor-ent-pimarane skeleton. Compounds 1-7 were screened for the inhibitory activity against lipopolysaccharide (LPS)-induced NO and TNF-α production in RAW264.7 cells. Compounds 1-3 exhibited potent inhibitory activities, with IC50 values of less than 10 µM.