Lupane-type triterpenoids from Acacia dealbata bark extracted by different methods

Abstract

The management of invasive species generates large amounts of biomass which end up in low value applications. However, these residues can potentially contain compounds with important bioactive properties. In this study the bark of Acacia dealbata Link (Fabaceae) was extracted by different methods targeting triterpenoids content and bulk product. Batch solid-liquid extraction (SLE-batch), Soxhlet extraction (n-hexane, dichloromethane, ethyl acetate and ethanol) and supercritical fluid extraction (SFE) (CO2 with/without ethanol or ethyl acetate) were performed under different pressure and/or temperature conditions in order to assess total extraction yield (ηTotal), extract concentrations and yields of lupenyl acetate and lupenone. The extracts composition was analysed by gas chromatography coupled to mass spectroscopy. Summarily: (i) the highest values of ηTotal were achieved with ethanol by both Soxhlet and SLE-batch, and by SFE at 300 bar, 80 ⁰C with 5 wt.% ethanol; (ii) the highest concentrations of triterpenoids were obtained with n-hexane by Soxhlet and SLE-batch and, and by SFE at 200 bar, 40 °C with 5 wt.% ethyl acetate; (iii) the maximum individual yields were achieved with ethanol by both Soxhlet and SLE-batch, and by SFE at 200 bar, 40 °C with 5 wt.% ethyl acetate. The solubilities of lupenyl acetate, lupenone, tetracosanoic acid and hexacosan-1-ol in the various solvents were theoretically estimated, providing important insights for the interpretation of the experimental results.