Constituents from Scutellaria barbata Inhibiting Nitric Oxide Production in LPS-Stimulated Microglial Cells

The arial parts of Scutellaria barbata D. Don (Lamiaceae) efficiently inhibited NO production in BV2 microglial cells, and the active constituents were further isolated based on activity-guided isolation using silica-gel column chromatography, RP-C18 MPLC and prep-HPLC. As the results, 2 flavonoids including 6-methoxynaringenin (1) and 6-O-methylscutellarein (5), and 6 neo-clerodane diterpenes such as scutebarbatine W (2), scutebatas B (3), scutebarbatine B (4), scutebarbatine A (6), 6-O-nicotinolylscutebarbatine G (7), and scutebarbatine X (8) were isolated. The structures of these compounds were elucidated based on NMR and MS data, and the comparison of literature values. All the compounds except compound 7 inhibited NO production efficiently with IC₅₀ values of lower than 50 μm. Particularly, compounds 1 and 8 were the most efficient with IC₅₀ values of 25.8 and 27.4 μm, respectively. This is the first report suggesting the potential of S. barbata on the reduction of neuroinflammation.