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

Abstract 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 CO 2 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.