Betulin is a biologically active triterpenoid substance, which can be isolated from birch bark. We report on a new approach to the synthesis of betulin sulfamate with sulfamic acid and ammonium sulfamate in the presence of solid catalysts, including Amberlyst 15® and Sibunit (granules) oxidized at 500 °C, Sibunit (powder) oxidized at 400 °C, Sibunit-sulfated, TiO 2 , and ɣ-Al 2 O 3 . It is shown that the synthesis with both sulfamic acid and ammonium sulfamate in the presence of an Amberlyst 15® catalyst yields sulfur derivatives of betulin. This catalyst has been proven to remain active at the repeated (up to four cycles) use. A reaction scheme for the catalytic production of sulfur derivatives of betulin is proposed. The obtained sulfur derivatives of betulin have been examined by Fourier transform infrared and ultraviolet visible spectroscopy, scanning electron and optical microscopy, X-ray diffractometry, thermogravimetric analysis, differential scanning calorimetry, and elemental analysis. It has been found by Fourier transform infrared spectroscopy that the use of sulfamic acid with an Amberlyst 15® catalyst ensures the formation of betulin sulfates, while when using ammonium sulfamate with the same catalyst, the sulfate and other betulin derivatives are obtained along with sulfates. It has been established from the X-ray diffractometry data that sulfation of betulin causes its stronger amorphization.

For the first time, polysaccharides: cellulose and xylan, isolated from birch wood by peroxide delignification in "acetic acid- water" medium in the presence of catalyst (NH4)6Mo7O24, were proposed to be used to obtain polymer composites (films). The initial components: cellulose, xylan, sodium alginate were characterized using the methods of FTIR, GC, GPC, laser diffraction and chemical analysis.It is shown that the introduction of ultrasound- activated birch bark cellulose into the composition of xylanalginate composites leads to an increase in the strength of the films, an increase in their barrier properties with respect to water vapor, and also reduces the solubility of the films in water.

In present paper, it is proposed to use tannins ethanol- isolated out of mechanically activated pine bark in synthesis of rigid foams without formaldehyde addition. The results obtained using IR and UV spectroscopy indicate that mechanical activation of the bark leads to a change in the content of hydrolyzed and condensed tannins in pine bark extracts. In particular, the composition of extracts obtained from bark activated by energy- tensed AGO-2 retains the highest content of hydrolyzable and condensed tannins, which amount to 62 and 9.4 mg/g of bark, respectively. Using the GPC method, it was established that obtained pine bark tannins being oligomeric: their molecular weight distribution has a bimodal shape with the peaks in 500 and 1000 g/mol regions. Synthesized by so- condensation via furfuryl alcohol tannin- containing rigid foams (TCRF) possess a cellular- type structure with a smooth surface and partially open cavities up to 10 mu m, as detected using SEM. The bulk density of the TCRF lies in range 0.64-0.82 g/cm3, 3 , and their specific compressive strength is about 11.8-19.9 kg/cm(2). It was revealed that calculated thermal conductivity coefficient of the TCRF, which varies in range of 0.129-0.185 W/(m center dot K), compared to known analogues, is close to aerated concrete with thermal conductivity 0.1-0.3 W/(m center dot K). Thermal stability of the TCRF in an argon atmosphere indicates that in the 30-800 degrees C temperature range samples thermal decomposition proceeds uniformly without a sharp mass loss with a low activation energy (10.6-12.6 kJ/mol). The carbon residues yield of the samples after TGA/DSC performed varies in range 42-49 wt.%.

Sulfated polysaccharides have a variety of important biologically active properties, such as anticoagulant, hypolipidemic, antiviral activity, the ability to be a means of targeted drug delivery and to improve the water solubility of certain drugs. Initial and sulfated polysaccharides’ biological activity depends on the method of their preparation, composition and structure. Currently, there is an extensive body of literature data on methods for the sulfation of various natural polysaccharides. However, modern reviews on this topic mainly focus on the biological activity and application of sulfated polymers, rather than on synthesis methods. The latest comprehensive review on methods for the synthesis of sulfated polysaccharides was performed by Caputo in 2019. To further study this area, you need to know the latest trends in this topic. Based on this, we decided to create a new, up-to-date review covering most of the existing methods for the synthesis of sulfated polysaccharides. This work examined methods for the synthesis of biologically active polysaccharide sulfates and their effect on polymer characteristics, as well as the advantages and disadvantages of each method. Traditional methods for sulfating polysaccharides were reviewed such as using a complex of sulfur trioxide with pyridine, and new methods based on the use of toxic free and corrosive free reagents. Some data on the biological activity of the obtained polysaccharides are considered.

Plant biomass, in particular forestry wastes, is a promising renewable feedstock for deep chemical processing. Organosolv methods allow the use of underutilized lignin. The synthesis of modified polymers by azo coupling with the use of aspen (Populus tremula) ethanol lignin and its sulfated modification is studied. The success of the synthesis has been proven and the features of the structure and properties of the synthesized samples were studied by the physicochemical techniques, including Fourier transform infrared and nuclear magnetic resonance spectroscopy, gel permeation chromatography and thermogravimetric analysis. It was shown that the new azopolymers have the ability to photoisomerize, which opens up prospects for their high-tech applications. The modified lignins are proven to be bioactive antioxidants.

Arabinogalactan (AG), extracted from larch wood, is a β-1,3-galactan backbone and β-1,6-galactan side chains with attached α-1-arabinofuranosyl and β-1-arabinopyranosyl residues. Although the structural characteristics of arabinogalactan II type have already been studied, its functionalization using 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) oxidation remains a promising avenue. In this study, the oxidation of AG, a neutral polysaccharide, was carried out using the TEMPO/NaBr/NaOCl system, resulting in polyuronides with improved functional properties. The oxidation of AG was controlled by analyzing portions of the reaction mixture using spectrophotometric and titration methods. To determine the effect of the TEMPO/NaBr/NaOCl system, air-dried samples of native and oxidized AG were studied by Fourier-transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy, as well as by gel permeation chromatography. Compounds that model free (1,1-diphenyl-2-picrylhydrazyl (DPPH)) and hydroxyl radicals (iron(II) sulfate, hydrogen peroxide, and salicylic acid) were used to study the antioxidant properties. It was found that, in oxidized forms of AG, the content of carboxyl groups increases by 0.61 mmol compared to native AG. The transformation of oxidized AG into the H+ form using a strong acid cation exchanger leads to an increase in the number of active carboxyl groups to 0.76 mmol. Using FTIR spectroscopy, characteristic absorption bands (1742, 1639, and 1403 cm−1) were established, indicating the occurrence of oxidative processes with a subsequent reduction in the carboxyl group. The functionality of AG was also confirmed by gel permeation chromatography (GPC), which is reflected in an increase in molecular weights (up to 15,700 g/mol). A study of the antioxidant properties of the oxidized and protonated forms of AG show that the obtained antioxidant activity (AOA) values are generally characteristic of polyuronic acids. Therefore, the TEMPO oxidation of AG and other neutral polysaccharides can be considered a promising approach for obtaining compounds with the necessary controlled characteristics.

Agarose sulfates are bioactive modified polysaccharides important for application. To obtain the bioactive agarose derivatives and expand the range of their potential use, the modification with some functional groups is needed. Agarose sulfates exhibit the anticoagulant, hypolipidemic, and other-type bioactivity. In this study, different methods for preparation of agarose sulfates using nontoxic ammonium sulfamate are investigated. Several activators and catalysts of the process of sulfation with ammonium sulfamate are examined. It is shown that urea does not significantly activate ammonium sulfamate in the sulfation reaction, while potassium permanganate ensures a sulfur content of up to 13.2 wt% in the synthesized agarose sulfate. When Lewis acids (titanium and aluminum oxides) are used, the sulfur content in agarose sulfates can only reach 7.3 wt%. The catalysts with the Bronsted acid sites used in the synthesis of sulfated agarose can provide sulfur contents of up to 14.6 wt% in it. The incorporation of a sulfate group into the agarose molecule has been confirmed by elemental analysis and Fourier-transform infrared spectroscopy: the absorption bands at 1249 cm-1 have been observed in the spectra. The X-ray diffraction and atomic force microscopy studies have revealed no ammonium sulfamate inclusions. According to the X-ray diffraction patterns, sulfation of agarose enhances its X-ray amorphism. It has been established from the atomic force microscopy images that the incorporation of a sulfate group into the agarose molecule changes the size of particles on the film surface from 42 to 80 nm. The theoretical examination of initial and sulfated agarose has been carried out within the density functional theory. The molecular geometry, vibration assignments, HOMO-LUMO, molecular electrostatic potential maps, and electronic properties of the substances have been established by the quantum-chemical calculations in the framework of the density functional theory.

Agrotechnical wastes from processing herbaceous plants consist of lignin and polysaccharides, which can be processed into monomers – phenols and carbohydrates. The prospects of chemical processing of several agrotechnical waste types with a high lignin content (flax shives, sunflower seed husks and buckwheat husks) into vanillin, pulp, and glucose by oxidation and acid hydrolysis were studied. It has been shown that despite the distant phylogenetic relationship of the studied plants, their lignins have a similar structure: they contain a similar amount of methoxyl groups (10–13 wt.% per lignin) and give close yields of aromatic aldehydes upon oxidation with nitrobenzene (17–19%) and oxygen (14–16%). In general, the suitability of agrotechnical wastes for oxidation to aromatic aldehydes determines by the lignin content. Among the studied wastes, flax shives are the most promising feedstock for chemical processing into vanillin and glucose. Cellulose-containing solid residues of oxidation process are more easily hydrolyzed compared to the initial lignocellulosic biomass. The inversion of glucose oligomers during the hydrolysis of cellulose with H2SO4 is limited by the hydrolysis of the tetra- and octamers.

A new approach is being considered for obtaining microfibrillated cellulose with a low degree of polymerization by sulfuric acid hydrolysis with simultaneous ultrasonic treatment under mild conditions (temperature 25 °C, 80% power control). Samples of initial cellulose, MCC, and MFC were characterized by FTIR, XRF, SEM, DLS, and TGA. It was found that a high yield of MFC (86.4 wt.%) and a low SP (94) are observed during hydrolysis with ultrasonic treatment for 90 min. It was shown that the resulting microfibrillated cellulose retains the structure of cellulose I and has an IC of 0.74. It was found that MFC particles are a network of fibrils with an average size of 91.2 nm. ζ-potential of an aqueous suspension of MFC equal to −23.3 mV indicates its high stability. It is noted that MFC has high thermal stability, the maximum decomposition temperature is 333.9 °C. Simultaneous hydrolysis process with ultrasonic treatment to isolate MFC from cellulose obtained by oxidative delignification of spruce wood allows to reduce the number of stages, reduce energy costs, and expand the scope.

Galactomannans are plant polysaccharides with the beneficial properties, which have a wide range of industrial application. The most important galactomannan derivatives are sulfates, which exhibit the anticoagulant and other biological activities. Here, we report on the results of investigations of the effect of urea-based solvents and activators on the sulfation of galactomannan guar gum with sulfamic acid. It has been shown that 1,4-dioxane is the most effective solvent, while urea is the most effective activator of the sulfation process. The numerical optimization (the Box‒Behnken design) of sulfation of galactomannan guar gum with sulfamic acid in the presence of the most effective activator has been carried out. It has been established that the optimal conditions for obtaining the galactomannan sulfates are a sulfamic acid amount of 34 mmol per 1 g of galactomannan, a temperature of 85 °C, and a time of 2.6 h. The introduction of a sulfate group into a galactomannan molecule has been proven by Fourier transform infra-red spectroscopy. It has been found that the Fourier transform infra-red spectrum of sulfated galactomannan contains absorption bands at 1249 and 817 cm ‒1 , which correspond to vibrations of the sulfate group. It has been demonstrated using gel permeation chromatography that, during sulfation of guar gum galactomannan by a complex of sulfamic acid and 1,4-dioxane, the molecular weight decreases from 8.5 × 10 5 to 3.0 × 10 5 g/mol and the polydispersity value increases from 1.816 to 2.049.

To ensure the high quality of water, it is necessary to remove toxic pollutants. At present, purification of water is implemented using various sorbents. The efficient sorption materials are modified polysaccharides. In this study, we report on a new environmentally friendly method for modifying larch hemicellulose—arabinogalactan (AG)—with polybasic carboxylic acids (citric, succinic, oxalic, and adipic) to obtain composite materials. The synthesized AG derivatives have been explored by a complex of physicochemical methods, including gel permeation chromatography (GPC), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffractometry (XRD), scanning electron microscopy (SEM), and sorption capacity investigations. It is shown that the heat treatment results in the formation of additional inter- and intramolecular bonds between carboxylic acids and polysaccharide molecules. The formation of ester bonds has been confirmed by the appearance of absorption bands in the IR spectra in the range of 1750–1690 cm−1. It has been found, using the TGA study, that the most thermally stable (up to 190 °C) sample is arabinogalactan oxalate obtained under heat treatment. The SEM study of the synthesized AG films has shown that the modified samples have the homogeneous film surface ensured by cross-linking. It has been established, when studying the sorption properties of the AG derivatives, that AG succinate (82.52%) obtained by lyophilization has the highest sorption capacity, due to the developed mesoporous surface, which, in turn, makes the synthesized films promising eco-friendly materials for use as drug carriers, sorbents, and water treatment agents.

Cellulose sulfates are important biologically active substances with a wide range of useful properties. The development of new methods for the production of cellulose sulfates is an urgent task. In this work, we investigated ion-exchange resins as catalysts for the sulfation of cellulose with sulfamic acid. It has been shown that water-insoluble sulfated reaction products are formed in high yield in the presence of anion exchangers, while water-soluble products are formed in the presence of cation exchangers. The most effective catalyst is Amberlite IR 120. According to gel permeation chromatography, it was shown that the samples sulfated in the presence of the catalysts KU-2-8, Purolit s390 plus, and AN-31 SO42− underwent the greatest degradation. The molecular weight destribution profiles of these samples are noticeably shifted to the left towards low-molecular-weight compounds with an increase in fractions in the regions Mw ~2.100 g/mol and ~3.500 g/mol, indicating the growth of microcrystalline cellulose depolymerization products. The introduction of a sulfate group into the cellulose molecule is confirmed using FTIR spectroscopy by the appearance of absorption bands at 1245–1252 cm−1 and 800–809 cm−1, which correspond to the vibrations of the sulfate group. According to X-ray diffraction data, amorphization of the crystalline structure of cellulose is observed during sulfation. Thermal analysis has shown that with an increase in the content of sulfate groups in cellulose derivatives, thermal stability decreases.

Water-soluble azo derivatives of lignin were synthesized by the azo coupling reaction using organosolv ethanol lignin and diazonium salts based on sulfanilic acid and p-nitroaniline. The structure of azo derivatives of lignin were studied by nuclear magnetic resonance, Fourier-transform infrared spectroscopy, and gel permeation chromatography. It was found that the azobenzene bonds formed in the azo coupling reaction of macromolecules impart the photosensitive properties to the synthesized polymers via cis–trans photoisomerization of the diazobenzene group. It was shown experimentally that the synthesized polymers exhibited good solubility both in the aqueous media in a wide (2–12) pH range and in DMSO and THF organic solvents, which opens up new prospects for their application.

A new method for extractive-catalytic fractionation of aspen wood to produce microcrystalline (MCC), microfibrillated (MFC), nanofibrilllated (NFC) celluloses, xylan, and ethanollignin is suggested in order to utilize all of the main components of wood biomass. Xylan is obtained with a yield of 10.2 wt.% via aqueous alkali extraction at room temperature. Ethanollignin was obtained with a yield of 11.2 wt.% via extraction with 60% ethanol from the xylan-free wood at 190 °C. The lignocellulose residue formed after the extraction of xylan and ethanollignin was subjected to catalytic peroxide delignification in the acetic acid-water medium at 100 °C in order to obtain microcrystalline cellulose. MCC is hydrolyzed with 56% sulfuric acid and treated with ultrasound to produce microfibrillated cellulose and nanofibrillated cellulose. The yields of MFC and NFC were 14.4 and 19.0 wt.%, respectively. The average hydrodynamic diameter of NFC particles was 36.6 nm, the crystallinity index was 0.86, and the average zeta-potential was 41.5 mV. The composition and structure of xylan, ethanollignin, cellulose product, MCC, MFC, and NFC obtained from aspen wood were characterized using elemental and chemical analysis, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) analyses, Gas chromatography (GC), Gel permeation-chromatography (GPC), Scanning electron microscopy (SEM), Atomic force microscopy (AFM), Dynamic light scattering (DLS), Thermal gravimetric analysis (TGA).

Spruce (Piceaabies) wood hemicelluloses have been obtained by the noncatalytic and catalytic oxidative delignification in the acetic acid-water-hydrogen peroxide medium in a processing time of 3–4 h and temperatures of 90–100 °C. In the catalytic process, the H2SO4, MnSO4, TiO2, and (NH4)6Mo7O24 catalysts have been used. A polysaccharide yield of up to 11.7 wt% has been found. The hemicellulose composition and structure have been studied by a complex of physicochemical methods, including gas and gel permeation chromatography, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The galactose:mannose:glucose:arabinose:xylose monomeric units in a ratio of 5:3:2:1:1 have been identified in the hemicelluloses by gas chromatography. Using gel permeation chromatography, the weight average molar mass Mw of hemicelluloses has been found to attain 47,654 g/mol in noncatalytic delignification and up to 42,793 g/mol in catalytic delignification. Based on the same technique, a method for determining the α and k parameters of the Mark–Kuhn–Houwink equation for hemicelluloses has been developed; it has been established that these parameters change between 0.33–1.01 and 1.57–472.17, respectively, depending on the catalyst concentration and process temperature and time. Moreover, the FTIR spectra of the hemicellulose samples contain all the bands characteristic of heteropolysaccharides, specifically, 1069 cm−1 (C–O–C and C–O–H), 1738 cm−1 (ester C=O), 1375 cm−1 (–C–CH3), 1243 cm−1 (–C–O–), etc. It has been determined by the thermogravimetric analysis that the hemicelluloses isolated from spruce wood are resistant to heating to temperatures of up to ~100 °C and, upon further heating, start destructing at an increasing rate. The antioxidant activity of the hemicelluloses has been examined using the compounds simulating the 2,2-diphenyl-2-picrylhydrazyl free radicals.

Sulfation of wheat straw soda lignin by the sulfamic acid-urea mixture in different solvents has been investigated for the first time. The effect of a catalyst used in the lignin sulfation process on the yield of the lignin sulfates and sulfur content in them has been explored. It has been found that the optimal medium for the lignin sulfation with sulfamic acid is dioxane and, in the presence of a catalyst, urea. Although the sulfated lignins obtained using the reaction in dimethyl sulfoxide and diglyme have the maximum sulfur contents (11.2% and 9.9%, respectively), these products are difficult to isolate and purify, which complicates the use of these solvents. Sulfated lignin obtained in the dioxane medium has a high (10.1%) sulfur content and is easy to isolate and purify. The incorporation of sulfate groups into the lignin structure has been confirmed by the infrared and nuclear magnetic resonance spectroscopy investigations. In the infrared spectra of sulfated lignin, characteristic absorption bands at 800-860 and 1260-1200 cm(-1) appear. The dominant substitution of aliphatic hydroxyl groups has been confirmed by the nuclear magnetic resonance spectroscopy study. It has been found that, during the modification and purification of lignin, the latter is fractionated, which results in the redistribution of molecular weights toward the high molecular-weight region, as well as the removal of some low-molecular-weight components, which is reflected in a decrease in the number of signals in the nuclear magnetic resonance spectra.

In this study, hemicelluloses of aspen wood (Pópulus trémula) were obtained by oxidative delignification in an acetic acid-water-hydrogen peroxide medium at temperatures of 70–100 °C and a process time of 1–4 h. The maximum polysaccharide yield of up to 9.68 wt% was reported. The composition and structure of the hemicelluloses were studied using a complex of physicochemical methods: gas and gel permeation chromatography, Fourier-transform infrared spectroscopy, 2D nuclear magnetic resonance spectroscopy, and thermogravimetric analysis. The xylose, mannose, galactose, and glucose monomer units were identified in the hemicelluloses by gas chromatography. The weight average molecular weight Mw of the products determined by gel permeation chromatography was found to range within 8932–33,142 g/mol. The reported Fourier-transform spectra of the hemicelluloses contain all the bands characteristic of heteropolysaccharides; a weak lignin absorption signal in the spectra at 1500–1510 cm−1 is attributed to a minor content of phenolic fragments in the structure of the obtained hemicelluloses. The use of thermogravimetric analysis established that the hemicelluloses isolated from aspen wood are resistant against heating to temperatures of up to 90–100 °C and, upon further heating up to 400 °C, start destructing at an increasing rate. The antioxidant activity of the hemicelluloses was examined using the compounds that mimic free radicals (1,1-diphenyl-2-picrylhydrazyl) and hydroxyl radicals (salicylic acid). It was found that the activity of all polysaccharides in neutralizing DPPH and hydroxyl radicals is lower than the absorption capacity of vitamin C at all the tested concentrations (0.5, 2, and 5 mg/mL) and attains 81.7 and 82.9%, respectively.

Arabinogalactan is a biologically active water-soluble polysaccharide contained in great amounts in larch wood. A sulfate group introduced into the arabinogalactan molecule increases its biological activity and imparts new anticoagulant and hypolipedemic properties. A new method for the catalytic sulfation of arabinogalactan with ammonium sulfamate is proposed. The catalytic activity in the reaction of arabinogalactan sulfation with ammonium sulfamate has been investigated for both the base activators (urea and thiourea) and oxidants (KMnO4 and K2Cr2O7). It has been shown that, in this process, the most effective activator is KMnO4, which ensures the highest (11.3 wt

Polysaccharides are important structural components of all plant species. Gel-like polysaccharides have found wide application in various fields, including medicine, construction, and the food industry. In the present work, galactomannan and galactoglucomannan gel-like polysaccharides were modified with sulfate groups and their anticoagulant activity was studied. Sulfation with chlorosulfonic acid in pyridine and with sulfamic acid in pyridine and a sulfamic acid–urea deep eutectic solvent were used as synthesis routes. The resulting gel-like polysaccharide sulfates were studied by elemental analysis, Fourier-transform infrared spectroscopy, and gel permeation chromatography. It was established that the anticoagulant effect of sulfated galactoglucomannan (SGGM) and galactomannan (SGM-1 and SGM-2) is related to an independent antithrombin-independent decrease in the amidolytic activity of thrombin and factor Xa. It is shown that the inhibitory activity of SGGM and SGM-2 against the collagen-induced platelet aggregation can be an additional factor in selecting compounds that are most promising for modifying polymer surfaces to ensure resistance to blood clotting.

Betulin is an important triterpenoid substance isolated from birch bark, which, together with its sulfates, exhibits important bioactive properties. We report on a newly developed method of betulin sulfation with sulfamic acid in pyridine in the presence of an Amberlyst®15 solid acid catalyst. It has been shown that this catalyst remains stable when being repeatedly (up to four cycles) used and ensures obtaining of sulfated betulin with a sulfur content of ~10%. The introduction of the sulfate group into the betulin molecule has been proven by Fourier-transform infrared, ultraviolet-visible, and nuclear magnetic resonance spectroscopy. The Fourier-transform infrared (FTIR) spectra contain absorption bands at 1249 and 835–841 cm−1; in the UV spectra, the peak intensity decreases; and, in the nuclear magnetic resonance (NMR) spectra, of betulin disulfate, carbons С3 and С28 are completely shifted to the weak-field region (to 88.21 and 67.32 ppm, respectively) with respect to betulin. Using the potentiometric titration method, the product of acidity constants K1 and K2 of a solution of the betulin disulfate H+ form has been found to be 3.86 × 10–6 ± 0.004. It has been demonstrated by the thermal analysis that betulin and the betulin disulfate sodium salt are stable at temperatures of up to 240 and 220 °C, respectively. The density functional theory method has been used to obtain data on the most stable conformations, molecular electrostatic potential, frontier molecular orbitals, and mulliken atomic charges of betulin and betulin disulfate and to calculate the spectral characteristics of initial and sulfated betulin, which agree well with the experimental data.