Anti-inflammatory neo-Clerodane Diterpenoids from Ajuga pantantha.

Eight new neo-clerodane diterpenoids (1-8) were acquired from the aerial parts of Ajuga pantantha. Spectroscopic data analysis permitted the definition of their structures, and experimental and calculated electronic circular dichroism data were used to define their absolute configurations. Compounds 2 and 4-8 were found to have NO inhibitory effects with IC₅₀ values of 20.2, 45.5, 34.0, 27.0, 45.0, and 25.8 μM, respectively. The more potent compounds 2, 6, and 8 were analyzed to establish their anti-inflammatory mechanism, including regulation of the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) proteins as well as their binding interactions with the two proteins.