Lipophilic extractives from the bark of Eucalyptus grandis x globulus, a rich source of methyl morolate: Selective extraction with supercritical CO2

The chemical composition of the lipohilic extracts of the inner and outer barks of Eucalyptus grandis x globulus, cultivated in Portugal, was studied by gas chromatography–mass spectrometry. The two bark fractions show different chemical compositions. β-Sitosterol is the most abundant compound in the inner bark (82 mg kg−1), while long chain aliphatic alcohols are the main family of components accounting for 208 mg kg−1. In the outer bark fraction, triterpenic compounds (8.5 g kg−1) are the most abundant ones from which methyl morolate (methyl 3-hydroxyolean-18-en-28-oate) is the chief component (3 g kg−1). This oleanane type tritepenic acid methyl ester was identified here for the first time as a component of Eucalyptus bark tissues using GC–MS and NMR. Other high value triterpenic acids such as ursolic, oleanolic and betulinic acids, accounting for 1.3, 0.9 and 0.6 g kg−1, respectively, were also detected in this fraction. Finally, the extraction of methyl morolate with supercritical CO2 was also carried out aiming at designing an environmentally friendly extraction alternative for this abundant compound. At 20 MPa and 333 K, the methyl morolate extraction attained a plateau at 6 h. In the whole, the acetylated triterpenic acids were more significantly extracted when compared to their free acids, which is directly related with the less polar nature of the former molecules.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The composition of Eucalyptus globulus x grandis bark lipophilic extracts is reported for the first time. ► Outer bark extract is a rich sources of triterpenic acids (∼8.5 g kg−1) among which methyl morolate was the most abundant compound (∼3 g kg−1). ► The methyl ester of morolic acid was identified for the first time in Eucalyptus barks. ► Supercritical CO2, enables methyl morolate extraction under environmentally benign conditions.