Preparative isolation of closely-related xanthones from Gentianella amarella ssp. acuta by High-speed countercurrent chromatography.
BACKGROUND
A methanolic extract from Gentianella amarella ssp. acuta was shown to contain several xanthones exhibiting acetylcholinesterase inhibitory activity. These xanthones were difficult to separate by conventional LC techniques, which prevented the isolation of pure compounds in sufficient amounts to perform in-depth biological testing.


OBJECTIVE
To develop a suitable preparative method for the separation of closely related xanthones.


METHODS
The methanolic extract was first partitioned with solvents of increasing polarity, in order to separate glycosides from xanthone aglycones. High-speed countercurrent chromatography (HSCCC) methods were then optimised for the fractionation of both polar and non-polar extracts.


RESULTS
The use of HSCCC enabled the separation of xanthones which co-eluted by HPLC. Ten closely related xanthones--three of which were isomeric--were successfully isolated by developing suitable solvent systems. All compounds were obtained in sufficient amounts to allow further biological assays (e.g. up to 250 mg), including even minor compounds that were not detectable by analytical HPLC.


CONCLUSIONS
The orthogonality of HSCCC with HPLC and the absence of solid-phase supports enabled the detection, separation and preparative isolation of closely related compounds which were difficult to resolve by other techniques.
Urbain
Aurélie
A
Laboratory of Pharmacognosy and Phytochemistry, School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, CH-1211 Geneva 4, Switzerland.
Marston
Andrew
A
Batsuren
Dulamjav
D
Purev
Ondognii
O
Hostettmann
Kurt
K
D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003377:Countercurrent Distribution / Q000379:methods*; D031313:Gentianella / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D012997:Solvents / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D044004:Xanthones / Q000302:isolation & purification*
D012997:Solvents; D044004:Xanthones