Tetrahydroxanthones from Mongolian medicinal plant Gentianella amarella ssp. acuta

Two tetrahydroxanthones, 1,3,5 S ,8 S -tetrahydroxy-5,6,7,8-tetrahydroxanthone ( 1 ) and 1,3,5 R ,8 S -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.