Supercritical fluid extraction of triterpenic acids from Eucalyptus globulus bark

Eucalyptus globulus bark contains four significant families of compounds, namely triterpenic (TT) acids (betulinic, betulonic, oleanolic and ursolic acids, and the acetylated forms of the latter two), long chain aliphatic alcohols, fatty acids, and sterols. The first group is the most abundant and possesses demonstrated bioactivity, which raises the importance of this biomass. The supercritical fluid extraction (SFE) of E. globulus bark was carried out in this work with carbon dioxide at 100, 140 and 200 bar, and 40, 50 and 60 °C, and the extracts were analyzed by GC–MS. The results are compared with those obtained by Soxhlet with dichloromethane, and the influence of the operating conditions upon the global yield and the individual yields of the triterpenic acids is discussed in detail. The acetylated TT acids imparted a large effect on the extraction yields, as they appeared in large concentrations on the extracts independently of their absolute loadings in the bark. The polarity of the free acids, higher than that of their acetyl derivatives, justifies this behavior. Modeling calculations were also performed for interpreting the SFE results. The experimental observations are in agreement with predictions accomplished for the solubilities and mass transfer fluxes of ursolic acid and 3-acetylursolic acid that were chosen as key TT acids in the process.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Supercritical fluid extraction (SFE) of Eucalyptus globulus bark. ► Eucalyptus bark extracts contain high amounts of triterpenic acids. ► Ursolic and 3-acetylursolic acids are the most abundant triterpenic acids. ► Effect of pressure and temperature upon supercritical extraction yields is evaluated. ► Modeling results interpret and justify the trends of experimental SFE results.