Dioscin derivatives from the Dioscorea villosa roots were isolated and purified by centrifugal partition chromatography coupled with evaporative light scattering detection. The two-phase solvent system composed of chloroform-methanol-isopropanol-water (7:6:1:4, v/v/v/v) was used to obtain prosapogenin A of dioscin (1, 11.1 mg), dioscin (2, 8.9 mg), deltonin (3, 29.2 mg) and diosgenin 3-O-[alpha-L-rhamnopyranosyl(1 --> 2)]-[beta-D-glucopyranosyl(1 --> 3)-beta-D-glucopyranosyl(1 --> 4)]-beta-D-glucopyranoside (4, 6.2 mg) from 300 mg of saponin-rich extract from the roots of D. villosa. The purities of 1, 2, 3 and 4 were determined to be 98.9, 97.4, 99.2 and 99.5%, respectively. Their chemical structures were determined by spectroscopic data of ESI-MS, 1H NMR and 13C NMR and comparing with those of previously reported values.