The extract of Siegesbeckia pubescens herb and its chemical constituents were tested for the ability to inhibit lipopolysaccharide (LPS)-induced nitric oxide (NO) production in BV2 microglia. The methanol extract and the 90% MeOH fraction of S. pubescens effectively attenuated lipopolysaccharide-induced nitric oxide production. Several steps of chromatography yielded eight ent-kaurane diterpenes (1-8) and one ent-pimarane diterpene (9) from the 90% MeOH fraction. Among these compounds, compounds 2-9 showed significant inhibitory effect on lipopolysaccharide-induced nitric oxide production in BV2 microglia. Compounds 3 and 9 concentration-dependently decreased the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), supported by quantitative real time polymerase chain reaction (PCR) and Western blot analysis. These results suggest that ent-kaurane and ent-pimarane diterpenes isolated from S. pubescens are expected to be potential candidates against neuroinflammation-related disease.

A methanolic extract of ALNUS FIRMA barks (Betulaceae) significantly attenuated nitric oxide production in lipopolysaccharide-stimulated BV2 microglia. Two new compounds, characterized as 4-hydroxy-2,6-dimethoxyphenyl 6'- O-syringoyl- beta- D-glucopyranoside (1) and 4-hydroxy-2,6-dimethoxyphenyl 6'- O-vanilloyl- beta- D-glucopyranoside (2), were isolated from the barks of A. FIRMA using bioactivity-guided fractionation, together with two known phenolic glycosides (3, 4) and 11 known diarylheptanoids (5- 15). Among these compounds, 1- 4 and 6- 11 showed significant inhibitory effect on lipopolysaccharide-induced nitric oxide production in BV2 microglial cells at concentrations ranging from 10 microM to 100 microM.