Science and Education Publishing Journal of Food and Nutrition Research 2333-1240 3 1 2015 01 06 Oleanolic acid Separation From Grape Skins by Aqueous Two-phase Extraction and Estimate Its Antioxidant Activity 34 39 EN Xifeng Zhang Fenqin Zhang Guanghong Luo Kaiyuan Bio-tech Development Center, Hexi University, Zhangye, P.R. China Shenghui Yang Danxia Wang JFNR2015316 10.12691/jfnr-3-1-6 2014 12 22 2014 12 29 2015 01 06 The aim of the current study is to focus on separating the oleanolic acid (OA) from previously prepared aqueous two-phase extraction (ATPE) of grape skins. Several different influential extraction parameters, such as ethanol concentration (v/w), ammonium sulphate concentration (w/w), crude extract concentration (w/w), extraction temperature, and pH, were also investigated. The optimal differential partitioning of OA was achieved in a system (at pH4.0, temperature=25°C)composed of 23% (v/w) ethanol, 18% (w/w) ammonium sulphate, 8% (w/w) crude extract and 41% (w/w) water. The recovery of extracted OA from experiments was determined to be 93.54%. The antioxidant activity of the separated ATPE in relative to VC were, also, investigated in this study at the proper conditions.The ATPE extract showed a relatively high antioxidant ability compared with that of Vitamin C. This proposed extraction technique opens up new possibilities in extraction of other active ingredients in natural plants or biologic samples.