Inhibitors from the rhizomes of Alpinia officinarum on production of nitric oxide in lipopolysaccharide-activated macrophages and the structural requirements of diarylheptanoids for the activity.

The 80% aqueous acetone extract from the rhizomes of Alpinia officinarum, a Chinese medicinal herb, were found to inhibit nitric oxide (NO) production in lipopolysaccharide (LPS)-activated mouse peritoneal macrophages. Through bioassay-guided separation, two diarylheptanoids [7-(4''-hydroxy-3''-methoxyphenyl-1-phenylhept-4-en-3-one and 3,5-dihydroxy-1,7-diphenylheptane] and a flavonol constituent (galangin) substantially inhibited LPS-induced NO production with IC50 values of 33-62 microM. To clarify structure-activity relationships of diarylheptanoids, related diarylheptanoids from Curcuma zedoaria were examined. Results indicate that the double bond or enone moiety at the 1-7 positions is important for the activity.