Rubesanolides F and G: Two Novel Lactone-Type Norditerpenoids from Isodon rubescens.

A phytochemical investigation of the leaves of the medicinal plant Isodon rubescens led to the isolation of the two new degraded abietane lactone diterpenoids rubesanolides F (1) and G (2). Their structures were elucidated based on the analyses of the HRESIMS and 1D/2D NMR spectral data, and their absolute configurations were determined by ECD spectrum calculations and X-ray single crystal diffraction methods. Compounds 1 and 2, with a unique γ-lactone subgroup between C-8 and C-20, were found to form a carbonyl carbon at C-13 by removal of the isopropyl group in an abietane diterpene skeleton. Rubesanolide G (2) is a rare case of abietane that possesses a cis-fused configuration between rings B and C. The two isolates were evaluated for their biological activities against two cancer cell lines (A549 and HL60), three fungal strains (Candida alba, Aspergillus niger and Rhizopus nigricans) and three bacterial strains (Escherichia coli, Staphylococcus aureus and Bacillus subtilis).

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.