Inhibitory constituents of lipopolysaccharide-induced nitric oxide production in BV2 microglia isolated from Amomum tsao-ko

A methanolic extract of the fruits of Amomum tsao-ko (Zingiberaceae) significantly attenuated nitric oxide production in lipopolysaccharide-simulated BV2 microglia. Two new bicyclic nonanes characterized as 6,7-dihydroxy-indan-4-carbaldehyde (1) and 6-hydroxy-indan-4-carbaldehyde (2) were isolated with the eleven known compounds 6,7-dihydroxy-3,7-dimethyloct-2-enoic acid (3), tsaokoin (4), isotsaokoin (5), 8-oxogeraniol (6), p-menth-1-ene-5,6-diol (7),3a-hydroxycarvotagenone (8), tsaokoarylone (9), 1,7-bis(4-hydroxy-3-methoxyphenyl)-4,6-heptadien-3one (10), (+)-hannokinol (11), meso-hannokinol (12) and hannokinin (13), from the fruits of A. tsao-ko using bioactivity-guided fractionation. All thirteen compounds significantly inhibited lipopolysaccharide-induced nitric oxide production in BV2 microglial cells at concentrations ranging from 1 mu M to 100 mu M.