Chemical composition of lipophilic extractives from six Eucalyptus barks

Abstract

Barks show a large diversity in chemical composition and are generally characterized by a substantial content of extractives. Today, these components are viewed with a renewed interest as valuable source of chemicals and bioactive compounds. The barks of six eucalypt species, Eucalyptus botryoides, E. camaldulensis, E. maculata, E. rudis, E. sideroxylon and E. viminalis, were studied in relation to their lipophilic extractives that represented between 0.1% (E. rudis) and 1.8% (E. viminalis) of the oven-dry bark. It is the first time that a detailed chemical composition is given for the lipophilic extracts from the barks of these eucalypt species. They showed a high content in triterpenes (between 3623.1 and 13,616.5 mg/kg of bark), especially triterpenic acids such as betulinic, ursolic, oleanolic and arjunolic acids. Sterols were also identified in considerable amounts (174.0–1736.7 mg/kg of bark). β-Sitosterol was the major sterol, with 1350.1 mg/kg of bark in E. maculata. Fatty acids C16–C28 existed in smaller amounts. A saponification treatment (MeOH/KOH) showed that fatty acids, sterols and triterpenes existed in both esterified and non-esterified forms. The presence of triterpenes represents a potential added value for the valorization of bark residues by production of bioactive or high-value compounds.