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 IC(50) values of less than 10 µM.