Extraction and fractionation of saponins by sequential extraction in a fixed bed using supercritical carbon dioxide, ethanol and water

Author(s)

Raphaela Gabrí Bitencourt

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia de Alimentos
• Defense date: 2014-03-20

Examining board members

Fernando Antonio Cabral; Losiane Cristina Paviani; Rodney Alexandre Ferreira Rodrigues

• Advisor: Fernando Antonio Cabral; Carmen Lucia Queiroga

Abstract

Saponins are compounds that stand out due to their pharmacological actions, and also because they are employed by food and cosmetics industry due to its physicochemical properties, such as surfactants. Extraction processes with supercritical carbon dioxide (scCO2) as a substitute of toxic organic solvents represent a good option for extracting biocompounds since they obtain free of undesirable solvents extracts and residues thus being a green technology. Therefore, this study aimed to extract and fractionate saponins of three plant sources: roots of Pfaffia glomerata and Hebanthe eriantha (Brazilian ginseng) and fruits of Melia azedarach, by a sequential process in fixed bed using scCO2, ethanol and water as solvents. The extractions were performed at 50 °C and 300 bar in four sequential steps. In the first step scCO2 was used as solvent; in the second scCO2/ethanol mixture, mass ratio 70:30 (w/w); pure ethanol and ethanol/water mixture 70:30 (v/v) were used in the third and fourth stages, respectively. The efficiency of extraction and fractionation process was evaluated based on: 1) the extraction yield, 2) presence of saponins, which were monitored by thin layer chromatography (TLC) and 3) the potential of extracts to reduce the surface tension of aqueous solutions. The extracts of Melia azedarach also were evaluated for their content of total phenols and flavonoids, chemical profile by GC-MS and mass spectrometry (ESI-MS). The roots studied presented similar overall extraction curves (kinetic) and yields in the first three steps. The extraction yields for the four stages of extraction were 0.16, 0.55, 1.00 and 6.9 % for roots of P. glomerata and 0.17, 0.58, 0.89 and 28 % for H. eriantha roots, respectively, showing predominant presence of polar compounds in these species. The extraction yields from fruits of M. azedarach were higher (7.6, 6.4, 19 and 12.3 %) than roots of Brazilian ginseng. Analyses by TLC indicated that process was selective in accordance with the polarity of the solvent used providing fractions enriched in different compounds. The extracts of three plant matrices obtained by carbon dioxide and ethanol mixture (SCEE) presented highest ability to reduce surface tension, with values of 25.0, 25.0 and 26.9 mN.m- 1 for P. glomerata, H. eriantha and M. azedarach, respectively, against 36.3 mN.m-1 for a synthetic surfactant solution (sodium dodecyl sulphate). This result suggests that ability is associated with the presence of less polar saponins. And further, Brazilian ginseng saponins have critical micelle concentration (CMC) ? 20 g.L-1. The highest levels of phenolic compounds of M. azedarach were obtained in hydroalcoholic extract (21.6 mg EAG/g extract) and SCEE (20.6 mg EAG/g extract). It was not observed a significant presence of volatile compounds in fruits of M. azedarach by GC-MS. ESI-MS analyses identified fatty acids (linoleic, palmitic and myristic acid) and azedarachin C (limonoid) in supercritical extract (SCE) and the presence of phenolic compounds (caffeic and malic acid) in the other extracts. Finally, the supercritical carbon dioxide has shown to be selective for saponins with the highest capacity to reduce the surface tension of water when used with ethanol as cosolvent. In general, process of sequential fixed bed extraction with green solvents represents a great alternative instead of using organic solvents to extract and fractionate saponins present in different plant sources (AU)

• FAPESP's process: 12/20736-9 - Use of supercritical technology to fractionate saponins in natural extracts
• Grantee: Raphaela Gabrí Bitencourt
• Support Opportunities: Scholarships in Brazil - Master