Features of the Chemical Composition and Structure of Birch Phloem Dioxane Lignin: A Comprehensive Study

Abstract

Understanding the chemical structure of lignin in the plant phloem contributes to the systematics of lignins of various biological origins, as well as the development of plant biomass valorization. In this study, the structure of the lignin from birch phloem has been characterized using the combination of three analytical techniques, including 2D NMR, Py-GC/MS, and APPI-Orbitrap-HRMS. Due to the specifics of the phloem chemical composition, two lignin preparations were analyzed: a sample obtained as dioxane lignin (DL) by the Pepper’s method and DL obtained after preliminary alkaline hydrolysis of the phloem. The obtained results demonstrated that birch phloem lignin possesses a guaiacyl–syringyl (G-S) nature with a unit ratio of (S/G) 0.7–0.9 and a higher degree of condensation compared to xylem lignin. It was indicated that its macromolecules are constructed from β-aryl ethers followed by phenylcoumaran and resinol structures as well as terminal groups in the form of cinnamic aldehyde and dihydroconiferyl alcohol. The presence of fatty acids and flavonoids removed during alkaline treatment was established. Tandem mass spectrometry made it possible to demonstrate that the polyphenolic components are impurities and are not incorporated into the structure of lignin macromolecules. An important component of phloem lignin is lignin–carbohydrate complexes incorporating xylopyranose moieties.

Structural features of lignin–hemicellulose–pectin (LHP) orchestrate a tailored enzyme cocktail for potential applications in bark biorefineries

“…It has been reported that dioxane lignin can be extracted with tannins and fatty acids from the bark of spruce or birch. 47,48 In WW, the disappearance of the peak centering around 20 ppm in WW_N can be attributed to the C4–C8 of the inter-flavonoid linkages of tannins or fats, and these were completely removed after the 0.1 M NaOH treatment 48 (Fig. 5).…”

New Oligomeric Dihydrochalcones in the Moss Polytrichum commune: Identification, Isolation, and Antioxidant Activity

“…For the primary screening of the chemical composition of the P. commune acetone extract, the combination of the two-dimensional NMR spectroscopy and the computational expert system for processing the obtained data, which was proven in a recent study of polyphenolic compounds in birch phloem [ 18 ], was used. This made it possible to isolate the signals of individual components of a complex mixture and presumably identify them on the basis of a library search.…”

Comprehensive Characterization of Secondary Metabolites in Fruits and Leaves of Cloudberry (Rubus chamaemorus L.)

“…This study is an attempt to fill this gap and is aimed at a comparative characterization of the aqueous ethanol extracts of cloudberry fruits and leaves, as well as a comprehensive study of the chemical composition and antioxidant activity of leaf secondary metabolites. Its methodological basis is formed by the combination of the most powerful and complementary techniques of two-dimensional NMR spectroscopy and high-performance liquid chromatography–high-resolution mass spectrometry, which has already proven itself in solving problems with regard to non-targeted screening and the identification of extractive substances of moss, compression wood, and birch phloem polyphenols [ 16 , 17 , 18 ].…”