Silver ion coordination countercurrent chromatography: Separation of β-elemene from the volatile oil of Curcumae Rhizoma.

In this work, the antitumor constituent β-elemene was selectively separated from the volatile oil of the Curcumae Rhizoma by countercurrent chromatography with silver nitrate as selective reagent based on the formation of coordination complexes. A biphasic solvent system composed of n-hexane/methanol/water (2:1.5:0.5, v/v/v) was selected, in which 0.15 mol/L of silver nitrate was added to the aqueous phase. The aqueous phase was used as the stationary phase for separation of β-elemene by countercurrent chromatography after it was partially purified from the volatile oil by silica gel column chromatography. An enriched β-elemene fraction was obtained by silica gel column chromatography to improve the percentage of β-elemene from 16.5 to 46.1%. Subsequently, β-elemene was further purified from 445 mg of the partially purified sample of volatile oil by countercurrent chromatography with silver nitrate as a selective reagent, yielding 145 mg of β-elemene with greater than 99% purity, as determined by gas chromatography mass spectrometry. The recovery of β-elemene from the crude volatile oil through two steps was around 63.6%.