The encapsulation of antioxidants with biocompatible polymers is essential for their protection against degradation factors like light and oxygen, and facilitates its solubility in the target medium. This work presents the co-precipitation of an ethanolic extract of rosemary leaves by supercritical antisolvent (SAS) process in poloxamers in order to improve the aqueous solubility of the extract. In a first step, the precipitation of antioxidants by SAS was studied in the range of temperatures from 25 to 50 degrees C and pressures from 8 to 12 MPa. Total content of polyphenols was quantified according to the Folin-Cicalteu method. Also HPLC analyses were performed to verify the presence of some of the major rosemary antioxidants, carnosic and rosmarinic acid. The dissolution rate of rosemary polyphenols from particles was measured in isotonic phosphate buffer solution (pH = 6.8). The encapsulation of the extract was successfully achieved with a yield up to 100%. The total polyphenolic content was dissolved from the encapsulated product, in the aqueous medium, after 1 h, whereas only 15% of the antioxidants of the pure precipitate were dissolved after 8 h. (C) 2011 Elsevier Ltd. All rights reserved.