An ionic liquid aqueous two-phase system (ILATPS) based on the hydrophilic ionic liquid 1-butyl-3-methylimidazolium chloride ([C(4)mim]Cl) and inorganic salts (K3PO4 and K2HPO4) was employed to separate Cordyceps sinensis polysaccharides (CSPS) and proteins by a single-step procedure. The maximum extraction efficiencies of CSPS and proteins were 89.4% and 88.2%, respectively, as obtained with the [C(4)mim]Cl/K3PO4 system at 25 degrees C and pH 13.0 under optimal conditions. The partially purified CSPS obtained from the bottom salt-rich phase comprised glucose, mannose, and galactose at a molar ratio of 10:3.5:1. The backbone of CSPS mainly comprised alpha-1,4-linked-D-glucose residues with a molecular weight of 2.3 x 10(7) Da. The results of this study suggest that ILATPS is an efficient and environmentally friendly system that will highlight novel possibilities in the large-scale separation and purification of active polysaccharides from fungi or mushrooms. (C) 2014 Elsevier B.V. All rights reserved.