neo-Clerodane Diterpenoids from Scutellaria barbata and Their Inhibitory Effects on LPS-Induced Nitric Oxide Production.

Three new neo-clerodane diterpenoids (1-3) along with 12 known compounds (4-15) were isolated from a methanol extract of the aerial parts of Scutellaria barbata. The structures of 1-3 were determined by interpretation of their 1D and 2D NMR spectroscopic data as well as HRESIMS values. All isolated compounds were tested for their inhibitory effects on LPS-induced nitric oxide production in RAW 264.7 macrophages. Compounds 1-4, 7, and 10-12 were found to inhibit nitric oxide production with IC50 values ranging from 20.2 to 35.6 μM.