Tetrahydroxanthones from Mongolian medicinal plant Gentianella amarella ssp. acuta

Two tetrahydroxanthones, 1,3,5S,8S-tetrahydroxy-5,6,7,8-tetrahydroxanthone (1) and 1,3,5R,8S-tetrahydroxy-5,6,7,8-tetrahydroxanthone (2), and six new tetrahydroxanthone glycosides, amarellins A-F (3-8), were isolated from the aerial parts of a Mongolian medicinal plant Gentianella amarella ssp. acuta (Gentianaceae). The structures of 1-8 were elucidated on the basis of spectroscopic analysis, chemical conversion, and ECD calculation. Amarellins A-C (3-5) were assigned as 8-O-β-D-glucoside, 8-O-β-D-xyloside, and 1-O-β-D-glucoside of 1, respectively, while amarellins D-F (6-8) were elucidated to be 8-O-β-D-xyloside, 1-O-β-D-glucoside, and 3-O-β-D-glucoside of 2, respectively.