Isolation and identification of constituents with activity of inhibiting nitric oxide production in RAW 264.7 macrophages from Gentiana triflora.

Gentiana triflora is widely used to treat inflammation, jaundice, hepatitis, and rheumatism. In this study, three new compounds, including a benzo seven-membered ring compound, gentioxepine (1), two secoiridoid glucosides, (1S,5R,9R)-deglucosyltrifloroside (2) and (1S,5R,9R)-scabraside (3), together with seven known ones, (+)-syringaresinol (4), deglucogelidoside (5), 3,4-dihydro-1H,6H,8H-naphtho[1,2-c:4,5-c',d']dipyrano-1,8-dione (6), deglucoscabraside (7), 2-hydroxy-3-O-β-D-glucosyloxy benzoic acid methyl ester (8), gentiolactone (9), and trifloroside (10), were isolated from the ethanol extract of Gentiana triflora. Their structures were mainly confirmed on the basis of NMR, MS, IR, CD, and UV spectral evidences. Inhibiting activities of nitric oxide production of eight of the compounds isolated, as well as gentiopicroside, were evaluated in the macrophage cell line RAW 264.7. The results show that the three new compounds and compound 7 could significantly suppress lipopolysaccharide-induced production of NO, with IC50s of 2.2 µM, 37.5 µM, 17.6 µM and 6.9 µM, respectively. Among them, compounds 1, 3, and 7 showed stronger inhibitory activity than that of the clinically used drug indometacin. Other tested compounds exerted moderate inhibiting activities.