Chemical characterization of the bark ofEucalyptus urophyllahybrids in view of their valorization in biorefineries

Abstract

Eucalyptus urophylla hybrids are important raw materials for the forest industry in Brazil, and large quantities of barks are available at mill site that may be used for added-value products. The chemical composition of barks of six commercial hybrids clones of E. urophylla × E. grandis, E. urophylla × E. Camaldulensis, and undisclosed E. urophylla hybrids was studied. The hybrids had similar composition, on average (data based on oven dry bark): 16% extractives, mainly corresponding to polar compounds that are soluble in ethanol and water, 19% lignin, 47% polysaccharides, 1% suberin, and 2% ash. The polysaccharides consists mainly of cellulose as indicated by 84% of total neutral monosaccharides in the acid hydrolysate and 10% xylose. The compositions of the lipophilic extracts was determined by GC-MS before and after alkaline hydrolysis. In all the barks, fatty acids, and triterpenes (namely: betulinic and ursolic acids) were the most abundant compounds followed by smaller amounts of sterols, long-chain aliphatic alcohols, phenolic acids, and acylglycerols. The ethanol-water bark extract had a high phenolic content: total phenolics ranged 211-551 mg gallic acid equivalents (GAE) g -1 of extract, tannins 76-184 mg catechin equivalents (CE) g -1 extract, and flavonoids 98-234 mg CE g -1 of extract. The antioxidant activity corresponds to 338 mg Trolox g -1 of extract. Development of high-value products is proposed through an integrated biorefinery approach including valorisation of extractives and targeting for cellulose-based applications.

Bark anatomy, chemical composition and ethanol-water extract composition of Anadenanthera peregrina and Anadenanthera colubrina

“…For instance 28.1% and 28.3% for Eucalyptus grandis x urophyla and E . grandis , respectively [ 48 ] or 26.7% for Pseudotsuga menziesii [ 30 ]. The phenolic content of bark extracts is very variable between species but usually below the values found here.…”

“…Total flavonoids were quantified by an aluminium chloride colorimetric assay using catechin as a standard [ 39 ] and the proanthocyanidins content (condensed tannins) was determined by the vanillin-H 2 SO 4 method using catechin as a standard [ 40 ]. The experimental procedure is described in detail in [ 30 ].…”

“…The antioxidant activity was assessed by the DPPH free radical assay [ 41 ] following a procedure described before [ 30 ]. The antioxidant activity was expressed as IC 50 values and also as in terms of Trolox equivalents (TEAC).…”

“…Eucalyptus spp. [ 28 , 29 , 30 ], Pseudotsuga menziesii [ 31 ], Quercus cerris [ 32 ], Tectona grandis [ 33 ]. Overall it has been shown that knowledge on the anatomy and chemical composition of the barks is essential for designing their fractionation and valorization routes.…”

Inter- and intraspecific variability of selected diarylheptanoid compounds and leaf morphometric traits in Alnus glutinosa and Alnus incana

“…In chemotaxonomic studies of plants, different methods are used [e.g. chemiresistor sensor array (Kalaw and Sevilla III 2018), Fourier-transform infrared (FTIR) absorption (Wang et al 2016), DNA analysis (Yu et al 2016)] as well as various chemical compounds, of which secondary metabolites are considered good chemotaxonomic markers (Nawawi et al 2016;Sartori et al 2016;Wu et al 2017). Chemotaxonomy is helpful in plant taxonomy on different hierarchical levels.…”