Fractionated extraction of saponins from Brazilian ginseng by sequential process using supercritical CO2, ethanol and water

Abstract

Saponins are surfactants that reduce the surface tension of aqueous solutions, besides having pharmacological actions. In order to extract and fractionate saponins from Pfaffia glomerata roots and Hebanthe eriantha roots using supercritical technology, fractionated extracts were obtained from a sequential process in fixed bed using supercritical CO2 (scCO2), ethanol, and water as solvents. All extractions were carried out in four sequential steps, at 50°C and 300bar. In the first step, pure scCO2 was used as solvent, while (a) scCO2/etanol (70:30, w/w); (b) ethanol, and (c) ethanol/water (70:30, v/v) were used as solvents in the three subsequent steps. The extracts were analyzed by thin layer chromatography (TLC) and surface tension. The extraction yields of the four steps were 0.16, 0.55, 1.00, and 6.90% for P. glomerata roots, and 0.17, 0.58, 0.89, and 28% for H. eriantha roots, showing a predominance of high polarity compounds in these species. TLC analysis showed that the extraction process was selective according to the polarity of the solvent, and provided extracts containing different saponins, except for scCO2 extraction. The extracts from the extraction using ethanol+scCO2 (Step 2) showed the greatest ability to reduce the surface tension of water from 72mNm−1 (pure water) to 25mNm−1, suggesting that this step was the best for extraction of less polar saponins in the extracts. The critical micelle concentration (CMC) values were approximately 2 and 8gL−1 for P. glomerata and H. Eriantha, respectively. These results confirmed the efficacy of the extraction process under study.