Secoiridoid glycosides from the root of Gentiana crassicaulis with inhibitory effects against LPS-induced NO and IL-6 production in RAW264 macrophages

The root of Gentiana crassicaulis has been widely used for the treatment of rheumatism, arthralgia, apoplexy, jaundice and diabetes in traditional medicines, and contains secoiridoid glycosides as the main active ingredients. In the present study, five new secoiridoid glycosides, 6′-O-β-D-xylopyranosylgentiopicroside (1) and gentiananosides A-D (2-5), together with 11 known ones were isolated from the MeOH extract of dried roots of G. crassicaulis. Their structures were elucidated on the basis of extensive spectroscopic evidence. Of them, gentiananosides A (2) and B (3) were concluded to be novel secoiridoid glycosides with an ether linkage between C-2′ of the sugar moiety and C-3 of the aglycone. Compounds 1, 4, 5, 7, 8, 12-14 exhibited moderate inhibitory effects against lipopolysaccharide-induced nitric oxide and interleukin-6 (IL-6) production in RAW264 cells, whereas 2 and 15 exhibited moderate inhibitory effects only against IL-6 production.