Vietnamese Callisia fragrans (C. fragrans) has been considered as a valuable traditional plant with various medicinal properties. In this study, polyphenols were extracted from Vietnamese C. fragrans leaves by supercritical carbon dioxide (SC-CO2) extraction method using ethanol as a cosolvent. The investigation of four factors influencing the total polyphenol content (TPC) and antioxidant activity of the extracts obtained from each single-factor experiment was conducted including ethanol concentration, CO2 flow rate, extraction temperature, and pressure. Besides, the extraction efficiency of the SC-CO2 method under the best extraction conditions, namely ethanol concentration of 14%, CO2 flow rate of 20 g/min, extraction temperature of 45°C, and pressure of 200 bar was compared to that of the Soxhlet extraction (SE) method in terms of the TPC and antioxidant activity of the extracts. The results showed that using SC-CO2 method, the TPC and the half-maximal inhibitory concentration value obtained were of 87.42 ± 1.33 mg/g and 243.83 ± 5.30 μM TE/g, respectively, with much less time and solvent amount required while that obtained using SE method were of 85.34 ± 4.27 mg/g and 236.33 ± 7.66 μM TE/g, respectively. This indicated that SC-CO2 would be suitable for the industrial production of polyphenols with high antioxidant activity of the extracts obtained due to the restrictions of using the SE method and advantages of applying SC-CO2 method. Therefore, SC-CO2 method could be regarded as a potentially upcoming extraction technique which might be employed to replace the conventional SE method.

V. amygdalina (V.A) is an herb commonly used in folk medicine; it possesses various compounds with therapeutic capabilities. Traditional extraction approaches applied to this plant may destroy its bioactive compounds and inherently contaminate them with toxic organic solvents. In this study, ultrasound-assisted extraction combined with gas-bubble flotation was applied to increase V.A extraction yield. The efficiency of water maceration was increased by 200%, without the drawbacks of the conventional extraction methods. The total phenolic content yield was 189 ± 12.7 (mg GAE/g dry weight) with a condensation efficiency of 115 ± 5.7%; and the total flavonoid content was 6.44 ± 1.68 (mg QE/g dry weight). Additionally, the antioxidant activity of the condensed foam was enhanced up to 120%. Analysis of the extract by FTIR revealed the presence of extractable chemical families: sesquiterpene lactones, saponins and flavonoids, and that the chemical characteristics of the extract were also preserved This article is protected by copyright. All rights reserved. This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as