Miscanthus x giganteus Extractives: A Source of Valuable Phenolic Compounds and Sterols

Abstract

The chemical composition of the lipophilic extracts of bark and core, of the Miscanthus x giganteus stalk, was studied by gas chromatography-mass spectrometry (GC-MS). Aromatic compounds, sterols, and fatty acids, followed by long-chain fatty alcohols, were the major families of components present in the M. x giganteus stalk. Aromatic compounds are more abundant in the M. x giganteus bark (521 mg/kg of bark), with vanillic acid, vanillin, and p-hydroxybenzaldehyde as the major compounds of this family. In the M. x giganteus core, sterols represent about 949 mg/kg of dry core with beta-sitosterol, 7-oxo-beta-sitosterol, stigmasterol, and campesterol as the major components. The detection of small amounts of esters in the GC-MS analysis with short columns explains the small increase in the abundance of the identified families after alkaline hydrolysis. The high content of valuable sterols and aromatic compounds in M. x giganteus and, particularly, in the core, which is considered a residue in most applications, can open new perspectives for the integrated upgrading of this grass within the biorefinery perspective.

Lipophilic Extractives from the Cortex and Pith of Elephant Grass (Pennisetum purpureum Schumach.) Stems

“…extractives was also found in the pith compared with the cortex. 7 The content is also similar to that found in other nonwoody fibers, such as flax, 16,17 hemp, 18 kenaf, 19 sisal, 20 abaca, 21 or jute. 22 The composition of the lipophilic extracts in the cortex and pith of elephant grass was analyzed in detail by GC and GC-MS according to previously developed protocols.…”

“…This content is similar to that found in the related species from the Poaceae giant reed, 8 and M. × giganteus. 7 Interestingly, in M. × giganteus, a higher abundance of lipophilic n-fatty alcohols 14…”

“…Fatty alcohols also occurred in higher amounts in the cortex than in the pith in the related species M. × giganteus. 7 A series of n-alkanes ranging from tricosane (C 23 ) to tritriacontane (C 33 ) also occurred in elephant grass in low amounts (14 mg/kg in the cortex and 21 mg/kg in the pith) with a strong odd-over-even carbon atom number predominance, nonacosane (V) being the most abundant followed by hentriacontane.…”

“…Alkyl ferulates have been widely reported in different plant families, 20,21,23−26 although they were not found in the related species giant reed 8 and M. × giganteus. 7 Glycerides (mono-, di-, and triglycerides) were another class of compounds present in significant amounts in the cortex and pith of elephant grass. Glycerides, and especially mono-and diglycerides, were reported in the related species from the Poacea giant reed 8 but were not reported among the lipophilic extractives in M. × giganteus, 7 despite the fact that mono-and diglycerides are very common constituents in many plants.…”

“…A previous paper from our group has already described in detail the characteristic of the lignin polymer of elephant grass; 6 however, to our knowledge, no previous studies have been published dealing with the composition of the lipophilic extractives in this species. Previous papers have, however, described the lipophilic extractives in related species from the Poaceae, M. × giganteus 7 and Arundo donax. 8 Extractives are a heterogeneous group of compounds dissolving in organic solvents (such as acetone or dichloromethane).…”