title: Preparative isolation and purification of three stilbene glycosides from the tibetan medicinal plant Rheum tanguticum maxim. Ex Balf. by high-speed counter-current chromatography.
abstract: BACKGROUND
  Stilbene glycosides are the primary constituents of Rheum tanguticum Maxim. ex Balf., to which different bioactivities has been attributed, including: anti-HIV, anti-oxidant, anti-tumour, anti-malarial, and anti-allergy activity. However, effective methods for the isolation and purification of stilbene glycosides, such as trans-rhapontin, cis-rhapontin and trans-desoxyrhaponticin, from this herb are not currently available.
  
  
  OBJECTIVE
  To develop an efficient method for the preparative isolation and purification of three stilbene glycosides from Rheum tanguticum Maxim. ex Balf. via high-speed counter-current chromatography (HSCCC).
  
  
  METHODS
  A solvent system composed of chloroform:n-butanol:methanol:water (4:1:3:2, v/v/v/v) was developed for the separation. The upper phase was used as the stationary phase, and the lower phase was used as the mobile phase. The flow rate was 1.8 mL/min. The apparatus was controlled at 800 rpm and 25 °C, and the effluent was monitored at 280 nm. Chemical constituents were analysed by high-performance liquid chromatography (HPLC), and their structures were identified by ¹H- and ¹³C-NMR.
  
  
  RESULTS
  Under the optimised conditions, 25.5 mg trans-rhapontin, 16.0 mg cis-rhapontin and 20.5 mg trans-desoxyrhaponticin were separated from 80 mg crude sample; the isolates had purities of 99.6, 97.2 and 99.2%, respectively.
  
  
  CONCLUSIONS
  A simple and efficient HSCCC method has been optimised for the preparative separation of stilbene glycosides from Rheum tanguticum Maxim. ex Balf.
authors.affiliation: Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining 810001, China. xhzhao@nwipb.ac.cn
authors.forename: Xiao-Hui
authors.initials: XH
authors.lastname: Zhao
authors.forename: Fa
authors.initials: F
authors.lastname: Han
authors.forename: Yu-Lin
authors.initials: YL
authors.lastname: Li
authors.forename: Hui-Lan
authors.initials: HL
authors.lastname: Yue
mesh_terms: D003377:Countercurrent Distribution / Q000379:methods*; D006027:Glycosides / Q000737:chemistry / Q000302:isolation & purification*; D015394:Molecular Structure; D018517:Plant Roots / Q000737:chemistry; D010946:Plants, Medicinal / Q000737:chemistry*; D015203:Reproducibility of Results; D012250:Rheum / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013267:Stilbenes / Q000737:chemistry / Q000302:isolation & purification*; D018609:Tibet
chemical_list: D006027:Glycosides; D012997:Solvents; D013267:Stilbenes