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Determination of Supercritical Carbon Dioxide Extraction Parameters for Quercus infectoria Galls and the Effects on Extraction Yield and Antioxidant Activity

Currently, finding alternative ways of extracting medicinal plant gain more interest from the researchers.  Quercus infectoria, a medicinal plant, is rich with bioactive compound being extracted using supercritical carbon dioxide (SC-CO 2 ) extraction which helps to maintain the quality of the product as well as green environment. CO 2 is widely used as solvent due to moderate critical conditions, nontoxic and easily removed from the products. This work was performed to determine the optimum extraction parameters of SC-CO 2 extraction and their effects on the total phenolic content and antioxidant activity of Q.infectoria extract. Hence, two different parameters have been investigated which were extraction time and CO 2 flow rate (2, 3, 4 ml/min) while pressure (P) and temperature (T) were fixed at highest density (P = 30 MPa, T = 40 o C). The results obtained from this study show that the solvent flow rate of 2 ml/min gives the highest percentage of yield (0.3652%) and the complete extraction of the sample was achieved at 80 minutes. Better quality of the extract was shown at 2 ml/min as resulted in high amount of phenolic compound in the extract presented as gallic acid equivalent (GAE) (2.04×10 2 mg GAE/g sample). The extracts were screened for possible antioxidant activity by 2,2-diphenyl-1-picryl hydrazyl (DPPH) free radical scavenging assays. In this study, the best result obtained for antioxidant activity was at flow rate of 3 ml/min with inhibition percentage of 96.97%.