Humulene derivatives from Zingiber zerumbet with the inhibitory effects on lipopolysaccharide-induced nitric oxide production

A new humulene sesquiterpene, 5-hydroxyzerumbone (5-hydroxy-2E,6E,9E-humulatrien-8-one) (1) and a known compound, zerumboneoxide (2) were isolated from the rhizomes of Zingiber zerumbet (Zingiberaceae), and found to inhibit lipopolysaccharide-induced nitric oxide production in murine macrophage RAW 264.7 cells with IC50 values of 14.1 and 23.5 microM, respectively, by bioassay-guided fractionation (positive control: N(omega)-monomethyl-L-arginine, IC50=21.3 microM). The structure of 1 was determined by spectroscopic methods including 1D and 2D-NMR.