Suppression of inducible nitric oxide synthase expression by diarylheptanoids from Alpinia officinarum

Six diarylheptanoids were isolated from the rhizome of Alpinia officinarum (Zingiberaceae) as inhibitors of nitric oxide (NO) production in the lipopolysaccharide-activated macrophage cell line RAW 264.7. A double bond at C-4 of the linker between two aromatic rings was found to be essential for activity. Furthermore, the active diarylheptanoids suppressed expression of the inducible NO synthase protein and mRNA. These results imply that the traditional use of Alpinia officinarum rhizome as anti-inflammatory drug may be explained, at least in part, by the inhibition of NO production in activated macrophages.