Eudesmane-Type Sesquiterpenes from Curcuma phaeocaulis and Their Inhibitory Activities on Nitric Oxide Production in RAW 264.7 Cells

Abstract

Eight eudesmane-type sesquiterpenes - phaeusmanes A-H (1-8) - isolated for the first time in this work, and four others (9-12) isolated for the first time from plants in this work, together with fourteen known eudesmane derivatives, were isolated from the rhizomes of Curcuma phaeocaulis. Their structures were elucidated by 1D and 2D NMR and CD spectroscopy and HRMS. Compound 8 is the first example of a nitrogen-containing eudesmane-type sesquiterpene isolated from the genus Curcuma. Furthermore, inhibitory effects of the isolated compounds on NO production in lipopolysaccharide-activated macrophages were evaluated. Compounds 1, 6, 10, 19, 22, and 24 showed strong inhibitory activities on NO production with IC50 values of 3.2, 4.8, 1.2, 0.8, 3.8, and 0.8 μM, respectively. Preliminary structure-activity relationships for these compounds are proposed. A possible biogenetic pathway for nitrogen-containing eudesmane-type sesquiterpene 8 is postulated. Eight new sesquiterpenes (phaeusmanes A-H), together with eighteen known analogues, were isolated from the rhizomes of Curcuma phaeocaulis. Their complete structures were elucidated by NMR, MS, and CD spectroscopy. The NO inhibitory effects of the isolates are presented. A possible biogenetic pathway for N-containing eudesmane-type sesquiterpene 8 is postulated. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.