Preparative isolation and purification of three flavonoid glycosides from Taraxacum mongolicum by high-speed counter-current chromatography.

A preparative high-speed counter-current chromatography (HSCCC) was successively applied to purify three flavonoid glycosides from the aerial part of Taraxacum mongolicum, a traditional Chinese medicine. Subsequent UV, MS, and NMR analyses have led to the characterization of three flavonoid glycosides including two new compounds isoetin-7-O-beta-D-glucopyranosyl-2'-O-alpha-L-arabinopyranoside and isoetin-7-O-beta-D-glucopyranosyl-2'-O-alpha-D-glucopyranoside, and a known compound, isoetin-7-O-beta-D-glucopyranosyl-2'-O-alpha-D-xyloypyranoside, which were first isolated from T. mongolicum. The two-phase solvent system composed of ethyl acetate/n-butanol/water (2:1:3, v/v/v) was performed in HSCCC. Consequently, a total of 25.7 mg isoetin-7-O-beta-D-glucopyranosyl-2'-O-alpha-L-arabinopyranoside, 19.1 mg isoetin-7-O-beta-D-glucopyranosyl-2'-O-alpha-D-glucopyranoside, and 10.6 mg isoetin-7-O-beta-D-glucopyranosyl-2'-O-alpha-D-xyloypyranoside were obtained with purity of 98.7, 98.3, and 99.1%, respectively, as determined by HPLC from 500 mg enriched extract after cleaning-up by polyamide resin.