Extraction of High Value Triterpenic Acids from Eucalyptus globulus Biomass Using Hydrophobic Deep Eutectic Solvents

Abstract

Triterpenic acids (TTAs), known for their promising biological properties, can be found in different biomass sources and related by-products, such as Eucalyptus globulus bark, and have been extracted using organic volatile solvents such as dichloromethane. Recently, deep eutectic solvents (DES) have been identified as promising alternatives for the extraction of value-added compounds from biomass. In the present work, several hydrophobic DES were tested for the extraction of TTAs from E. globulus bark. Initial solubility studies revealed that DES based on menthol and thymol as the most promising solvents for these compounds given the highest solubilities obtained for ursolic acid (UA) at temperatures ranging from room temperature up to 90 °C. Accordingly, an eutectic mixture of menthol:thymol (1:2) was confirmed as the best candidate for the TTAs extraction from E. globulus outer bark, leading to extraction yields (weight of TTA per weight of biomass) at room temperature of 1.8 wt% for ursolic acid, 0.84 wt% for oleanolic acid and 0.30 wt% for betulinic acid. These values are significantly higher than those obtained with conventional organic solvents under similar conditions. The results obtained using these DES are promising for the recovery of TTAs for nutraceutical and pharmacological applications, while reinforcing the potential of DES as promising solvents to be applied in biorefinery processes.

Co-production of biofuels and value-added compounds from industrial Eucalyptus globulus bark residues using hydrothermal treatment

“…Opposing to eucalyptus wood, literature data on the fractionation of eucalyptus bark is rather scarce, with most of the existing results focusing on its characterization and/or in the extraction of bioactive compounds and the effect of pretreatment on its enzymatic saccharification [16,17,21,38,39]. As for eucalyptus wood, eucalyptus bark also presents an interesting potential, mostly due to a considerable amount of polysaccharides (67.17%) and, to a lower extent, lignin (21.86% Klason lignin) and a minimal content of ash (2.63%), as shown in Table 1.…”

Natural Polymers-Based Materials: A Contribution to a Greener Future

“…This mindset has been supported by the enforcement of environmental regulations, such as the Pollution Prevention Act of 1990 that is enforced by the US Environmental Protection Agency (EPA), the Rio Declaration on Environment and Development that was adopted by the United Nations (UN) Conference on Environment and Development only two years later [ 32 ], and the adoption of the UN objectives of the 2030 Agenda for Sustainable Development [ 33 ]. The role of academia in the implementation of more sustainable practices is evident in the upsurge of diverse literature reports dealing with the maximization of resources [ 34 , 35 ], the use of environmentally benign solvents [ 36 , 37 , 38 ], and the valorisation of renewable resources for the recovery of high-value low-molecular-weight compounds and macromolecular fractions [ 39 , 40 ] (to give a few examples).…”

“…Innovation in BioPolymer-based Functional Materials and Bioactive Compounds, from the Portuguese associate laboratory CICECO–Aveiro Institute of Materials [ 41 ] at the University of Aveiro in Portugal. Among other research topics [ 42 , 43 , 44 , 45 ], this interdisciplinary group exercises research activities devoted to the use of renewable feedstocks for the extraction of high-value compounds from agroforest and industrial by-products [ 39 , 40 , 46 ], the valorisation of vegetable oils for the production of monomers and polymers [ 47 , 48 , 49 , 50 , 51 ], the design of biobased polyesters [ 52 , 53 , 54 , 55 ], and, in particular, the development of a panoply of natural polysaccharide- and protein-based materials [ 6 , 56 , 57 , 58 , 59 , 60 , 61 , 62 ].…”

Biocatalysis in the Chemistry of Lupane Triterpenoids

“…Hydrophobic deep eutectic solvents were used as an alternative for the extraction of betulinic acid ( 5 ) and other terpenic acids in work published in 2020 by Silva et al [ 47 ]. Deep eutectic solvents are described in the article as a combination of at least one hydrogen bond acceptor and a hydrogen bond donor that forms a eutectic mixture.…”

“… Methods of synthesis of betulinic acid [ 47 , 48 , 49 , 50 , 51 , 52 ]. Reagents and conditions: (i) chromium(VI) oxide; sulfuric acid, and acetone, H 2 O; (ii) sodium tetrahydroborate and isopropyl alcohol; (iii) 4-acetylamino-2,2,6,6-tetramethylpiperidine-N-oxyl, sodium chlorite, tetrabutylammomium bromide, sodium hypochlorite, and phosphate buffer at 50 °C; (iv) 4-acetylamino-2,2,6,6-tetramethylpiperidine-N-oxyl, tetrabutylammomium bromide, sodium hypochlorite, and phosphate buffer (pH = 7.6) at 50 °C; (v) BAIB, TEMPO, NaH 2 PO 4 , NaClO 2 , 2-methyl-2-butene, BuOAc, water, and t-BuOH at 20 °C for 6 h; (vi) 2,6,6-tetramethyl piperidine-N-oxyl, tetrabutylammomium bromide, and sodium hypochlorite in phosphate buffer with dichloromethane for 6 h with pH = 6.8; (vii) sodium dihydrogenphosphate, sodium permanganate, DCM, water, and tert-butyl alcohol at 25 °C for 3 h; (viii) K 2 CO 3 and MeOH for 24 h; and (ix) KOH and MeOH with heating for 3 h. …”