The aim of this work was to obtain extracts from two plants, namely Pterospartum tridentatum (Carqueja) and Waltheria indica, using supercritical carbon dioxide (scCO2), a green solvent. ScCO2 was used pure or with added co-solvent ethanol. The essential oils from these plants have economic value due to their content in compounds with medicinal properties. For comparison, extraction assays were performed using Soxhlet/ethanol and infusion/water. The highest yields of extraction were obtained when using infusion/water - 22,5% for Carqueja and 25,0% for W. indica – followed by Soxhlet/ethanol - 21,5% for Carqueja and 22,4% for W. indica. In the case of extractions with scCO2, higher yields of extraction were obtained at 500 bar than 350 bar at a temperature of 40 ºC – 1.28% and 0.64%, respectively. These values went up when at the same temperature and 300 bar, ethanol was added to CO2 as co-solvent – maximum of 4.36% for Carqueja and 14 wt.% ethanol, and maximum of 3.13% for Waltheria indica and 10 wt.% of ethanol. Extraction assays were also carried out by Soxhlet/ethanol and infusion/water from Carqueja and W. indica previously extracted with scCO2, with or without co-solvent ethanol. The trend observed was an increase in yields of extraction when Soxhlet/ethanol was used, suggesting that scCO2 was able to remove from both plants compounds that the Soxhlet/ethanol method cannot extract. In the case of infusion/water, the trend observed was a decrease in yields of extraction relative to the values obtained with the original plant material, suggesting that scCO2 was able to remove from both plants some compounds that are also extracted by the infusion/water method. Taking into consideration that polyphenols are the major class of compounds present in Carqueja and in W. indica, the extracts obtained were analyzed with a view to quantifying total phenolic compounds (TPC) and antioxidant capacity, the latter through values of EC50 (half maximum effective concentration). The best results for Carqueja were 64, 67 and 118 mg of gallic acid equivalents per g of plant and for extracts obtained with scCO2/ethanol, Soxhlet/ethanol and infusion/water, respectively, and for Waltheria indica 10, 77 and 91 mg of gallic acid equivalents per g of plant and for extracts obtained with scCO2/ethanol, Soxhlet/ethanol and infusion/water, respectively. The EC50 values were always very high (unfavorable) for extracts from both plants obtained by scCO2/ethanol extraction, and were of ca. 1 and 0.4 g of extract per g of DPPH (radical used in this assay) for Carqueja extracts obtained by Soxhlet/ethanol and infusion/water, respectively, and 2 and 0.3 g of extract per g of DPPH for Waltheria indica extracts obtained by Soxhlet/ethanol and infusion/water, respectively. A preliminary characterization of Carqueja extracts performed by thin layer chromatography (TLC) had already evidenced the presence of phenolic compounds in extracts obtained by Soxhlet/ethanol, as well as fatty acids, triglycerides and terpenes in extracts obtained by scCO2, Soxhlet/ethanol and Soxhlet/n-hexane extraction. This work can be considered a first approach to the use of supercritical technology to obtain extracts from Carqueja and W. indica
