Guaiane-Type Sesquiterpenes from Curcuma phaeocaulis and Their Inhibitory Effects on Nitric Oxide Production

Ten new guaiane-type sesquiterpenes (1–10), phaeocaulisins A–J, and 18 known guaiane derivatives were isolated from rhizomes of Curcuma phaeocaulis. Their structures were established on the basis of extensive spectroscopic analyses, X-ray crystallographic analysis, and comparison with literature data. Compound 10 is the first example of a norsesquiterpene with this unusual skeleton isolated from the genus Curcuma. All of the isolated compounds were tested for inhibitory activity against LPS-induced nitric oxide production in RAW 264.7 macrophages. Compounds 1, 2, 20, and 22–24 inhibited nitric oxide production with IC50 values less than 2 μM. Preliminary structure–activity relationships for these compounds are discussed.