Supercritical CO2 extraction of oleanolic acid from grape pomace

In this work, we investigated the possibility to extract oleanolic acid through supercritical fluid extraction from waste materials such as grape pomace, which can represent a yet unexploited source of highly added-value products. Preliminary supercritical fluid extractions were performed on dried grape skin samples and compared with solid-liquid extraction. After optimising extraction parameters such as temperature, pressure and extraction time, the ratio between supercritical and solid-liquid extraction yields was approximately 1/5. Supercritical CO2 extractions were also carried out on dried grape pomace samples. In this case, the ratio between supercritical and solid-liquid extraction yields was increased up to 1/3, thanks to a combination of static and dynamic extraction and the use of ethanol as modifier. This extraction technique proved successful in extracting oleanolic acid from grape pomace samples with extraction yields that were comparable with those obtained with well-established extraction techniques such as solid-liquid extraction.