Abstract: We employed pH-zone-refining counter-current chromatography(pH-ZRCCC)and conventional high-speed counter-current chromatography (HSCCC) to separate and prepare the chemical components in the crude extracts of Rheum officinale Baill.We initially used pH-ZRCCC to separate the crude extracts of Rheum officinale Baill.with petroleum ether-ethyl acetate-methanol-water(3：7：4：6,V/V) as a binary phase solvent system.Trifluoroacetic acid of 10 mmol/L was added to the upper organicstationary phase as a retainer and NaOH of 15 mmol/L was added to the aqueous mobile phase as an eluter.We acquired cinnamic acid (purity of 96.1%)of 140 mg, rhein(purity of 92.5%) of 130 mg and residue of 560 mg from crude extracts of 1.3 g. We further applied conventional HSCCC to the separation of the residue of 260 mg with petroleum ether-ethyl acetate-methanol-water (7：3：7：4,V/V) as a binary phase solvent system, and obtained aboutemodin (purity of 96.5%)of 98 mg and aloeemodin (purity of 96.5%) of 60 mg. We employed HPLC to detect the purity and ESI-MS and1HNMR to identify those structures. Results show that the combination of pH-ZRCCC and HSCCC is an effective method for the separation of chemical compounds from Rheum officinale Baill.

Key words: pH-zone-refining counter-current chromatography, HSCCC, Rheum officinale Baill., rhein, emodin, aloeemodin