Optimization of guar gum galactomannan sulfation process with sulfamic acid

Progress in galactomannan-based materials for biomedical application

Galactomannan-based biomaterials display a unique behavior in aqueous media due to their mechanical, rheological and solubility properties, which are increasingly attracting their applicability into the biomedical area. The physical-chemical features of galactomannans extracted from different botanical sources provide diverse applicability for the developed systems, which can deliver active substances and be applied in wound healing and bone replacement. Galactomannans have an essential biological role and can be easily chemically modified due to their reactive chemical structure. Besides, their biocompatibility and capacity to be applied in the form of film, hydrogel, micro, nanoparticles, and printed material, could revolutionize personalized medicine. Scientists are investigating ways to functionalize galactomannans with bioactive molecules to enhance their biological performance. This is the first review of galactomannans that combines their chemical modifications with biological activities, presenting various biomaterial possibilities with a focus on biomedical applications. The rising demand for renewable-source materials in the medical field underscores their importance, driving ongoing research to explore their full capabilities. As studies progress, the scope of clinical applications for galactomannan-based materials is expected to broaden. To maximize the bioactive potential of galactomannan-based materials, emphasis should be placed on clinical translation to facilitate its effective incorporation into biomedical applications.

A comprehensive study of experimental and theoretical characterization and in silico toxicity analysis of new molecules

In this study, for the first time in the literature, a 2-(3-methoxyphenylamino)-2-oxoethyl acrylate (3MPAEA) molecule was synthesized in two steps, and a 2-chloro-N-(3-methoxyphenyl)acetamide (m-acetamide) was obtained in the first step. Experimental results were obtained using FTIR, 1H, and 13C NMR spectroscopy methods for m-acetamide and 3MPAEA compounds created in the laboratory environment and compared with theoretical results. Band gap (BG) energy, chemical hardness, electronegativity, chemical potential, and electrophilicity index were calculated. With vibration spectroscopic analysis, atom-molecule vibrations of the theoretical and experimental peaks of the spectrum were observed. The locations of C and H atoms were determined by nuclear magnetic resonance spectroscopy. The green, blue, and red regions of the potential energy map (MEP) map were examined. Some observed that the energy thermal, heat capacity, and entropy graphs increased in direct proportion to increasing the temperature in Kelvin, which is known as thermochemistry. The changes in the rotation, translation, and vibration of the molecule as its temperature increased were examined. When the thermochemistry surface map was examined, some observed that the temperature was high in the middle binding site of the molecules. Covalent interactions were graphed using the non-covalent interactions (NCIs) calculation method. In silico toxicity studies were carried out for m-acetamide and 3MPAEA molecules: fathead minnow LC50 (96 h), Daphnia magna LC50 (48 h), Tetrahymena pyriformis IGC50 (48 h), oral rat LD50, water solubility, bioconcentration factor, developmental toxicity, mutation, normal boiling point, flash point, melting point, density, thermal conductivity, viscosity, vapor pressure, etc. parameters were investigated.

Comprehensive analysis of the electronic, thermodynamic, and spectroscopic properties of a Cu(II)-based complex with 1,10-phenanthroline and L-glutamine

This study reports additional information's of geometric, electronic, thermodynamic, and vibrational properties of a Cu(II) complex with 1,10-phenanthroline and L-glutamine ligands. The experimental spectroscopic analyses were corroborated by density functional theory (DFT). Furthermore, these properties were evaluated using an implicit solvation method with water and methanol solvents, including vacuum condition. The theoretical predictions provided a deeper understanding of the frontier molecular orbitals, chemical reactivity indices, dipole moment, and electrostatic potential maps. A computational analysis of the intermolecular interactions using Hirshfeld surfaces was also performed, which demonstrated that the H⋯O/O⋯H and H⋯H interactions are mainly responsible for the structural and thermal stability of the complex. The calculated intramolecular vibration bands showed a good correlation with the experimental Raman and infrared (IR) data, although solvation effects caused some wavenumber shifts. In vitro, antitumor assays were performed to evaluate the cytotoxic effects of the complex against prostate (PC-3) and glioblastoma (SNB-19) cancer cells. Absorption, distribution, metabolism, and excretion (ADME) parameters, along with drug-like properties, are also presented in this work.

Assessing the Noncovalent Interaction of Deucravacitinib and Ethanol with Special Reference to an Independent Gradient Model Based on Hirshfeld Partition

The current study begins by optimizing the deucravacitinib molecule in the gas phase at the ωB97XD/cc-pVDZ level of theory using density functional theory and proceeds to study its intramolecular interactions. Further, a molecule of EtOH was introduced at different locations on the deucravacitinib molecule, and the noncovalent interactions arising from them were also investigated using several computational tools. In this way, eight deucravacitinib-EtOH systems (1-8) were identified and their electronic environment was studied after evaluating their binding energy. Using natural bond orbital analysis, the localization of charges between the donor and acceptor fragments in these interacting systems was examined. The nature of interactions was analyzed using the reduced gradient approach (NCI analysis), and few hydrogen bonding interactions (intermolecular and intramolecular) were found in each system. The strength of these hydrogen bonding interactions was further investigated by using theoretical tools such as atoms in molecules analysis and independent gradient model based on Hirshfeld partition analysis. The binding energy of deucravacitinib with EtOH was decomposed into energy components based on the domain-based local pair natural orbital coupled cluster technique using LED analysis. The results from the hydrogen bonding interaction analysis using different computational tools were found to be consistent with the calculated order of binding energy of systems 1-8 and they also pointed toward the higher stability of system 3.

Siberian Federal University, Svobodny Pr. 79, Krasnoyarsk 660041, Russia, KAZACHENKO ALEKSANDRS, FETISOVA OLGAYU, Institute of Chemistry and Chemical Technology, Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences, Akademgorodok 50, Blvd. 24, Krasnoyarsk 660036, Russia, KARACHAROV ANTONA, Institute of Chemistry and Chemical Technology, Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences, Akademgorodok 50, Blvd. 24, Krasnoyarsk 660036, Russia, BEREZHNAYA YAROSLAVAD, Institute of Chemistry and Chemical Technology, Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences, Akademgorodok 50, Blvd. 24, Krasnoyarsk 660036, Russia, ISSAOUI NOUREDDINE, Laboratory of Quantum and Statistical Physics (LR18ES18), Faculty of Sciences, University of Monastir, 5079, Tunisia, LUTOSHKIN MAKSIMA, Institute of Chemistry and Chemical Technology, Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences, Akademgorodok 50, Blvd. 24, Krasnoyarsk 660036, Russia, SYCHEV VALENTINV, Institute of Chemistry and Chemical Technology, Krasnoyarsk Scientific Center, Siberian Branch, Russian Academy of Sciences, Akademgorodok 50, Blvd. 24, Krasnoyarsk 660036, Russia, KAZACHENKO ANNAS, Siberian Federal University, Svobodny Pr. 79, Krasnoyarsk 660041, Russia, AL-DOSSARY OMARM, "Department of Physics and Astronomy, College of Science, King Saud University, PO Box 2455, Riyadh 11451, Saudi Arabia", BOUSIAKOU LEDAG, IMD Laboratories Co, R&D Section, Lefkippos Technology Park, NCSR Demokritos PO Box 60037, Athens 15130, Greece. DIFFERENT APPROACHES TO AGAROSE SULFATION WITH SULFAMIC ACID

Sulfated polysaccharides are important promising biologically active substances with anticoagulant properties. Biological activity is affected by the method of preparation, as well as the type of the polysaccharide and its molecular structure. In this work, we have considered various methods for the synthesis of promising anticoagulants – polysaccharide sulfates using the example of obtaining agarose sulfate. We compared various sulfating agents: chlorosulfonic acid, sulfamic acid, with various activators, and a deep eutectic solvent mixture of sulfamic acid with urea (in the melt). It has been shown that when urea is used as an activator of the process of sulfation of agarose with sulfamic acid in 1,4-dioxane, agarose sulfate with a high sulfur content (up to 14.5 wt%) is formed, which is close to the use of chlorosulfonic acid as a sulfating agent (with the production of agarose sulfate with 15.0 wt% sulfur). The use of solid catalysts in the process of sulfation of agarose with sulfamic acid leads to the production of agarose sulfate with a sulfur content of up to 14.1 wt% (for a catalyst based on the oxidized carbonaceous material Sibunit-4®). Sulfation of agarose in a deep eutectic solvent – a mixture of sulfamic acid with urea – leads to the production of agarose sulfate with a sulfur content of up to 13.7 wt%. The resulting agarose sulfates were characterized by FTIR spectroscopy, X-ray diffraction, elemental analysis, atomic force microscopy and DFT.

Sulfation on polysaccharides from Zizania latifolia extracted using ultrasound: Characterization, antioxidant and anti-non-small cell lung cancer activities

Zizania latifolia is a highly nutritious vegetable being praised as "Ginseng in Water". Polysaccharides are the main bioactive ingredients in Z. latifolia, but there have been no reports on the yield- and activity-guided ultrasonic-assisted extraction (UAE), sulfation and anti-non-small cell lung cancer (NSCLC) activity. In this study, Z. latifolia polysaccharides (ZLP) were extracted using UAE under an optimized power, followed by sulfation to give three derivatives (SZLP-1 ∼ 3). After characterization, the antioxidant and anti-NSCLC activities were evaluated. The optimal ultrasonic power for ZLP extraction was screened out to be 300 W, under which the yield was 16.9 ± 2.10 %, and the scavenging rate against 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical was 63.3 ± 5.71 %, significantly higher than those of other powers and hot-water extraction. A series of characterizations fully confirmed the sulfated modification of ZLP. Sulfation improved the antioxidation of ZLP and was positively proportional to the degree of substitution (DS), of which SZLP-2 with a DS of 15.1 ± 2.50 elicited strong hydroxyl and DPPH radicals-scavenging capacities. Meanwhile, SZLP-2 also exerted promising anti-NSCLC potency via inhibiting A549 cell proliferation, with a median inhibition concentration (IC50) of 0.57 ± 0.01 mg/mL at 72 h, markedly smaller than that of unmodified ZLP (0.78 ± 0.04 mg/mL). In summary, the yield- and activity-guided UAE led to the ZLP with high yield and strong antioxidation. Further sulfation enhanced the bioactivities and produced the promising SZLP-2, which showed great potential in the development of novel antioxidant and anti-NSCLC drug.

Chemical Modification of Polysaccharides: A Review of Synthetic Approaches, Biological Activity and the Structure-Activity Relationship

Natural polysaccharides are macromolecular substances with great potential owing to their wide biological activity and low toxicity. However, not all polysaccharides have significant pharmacodynamic activity; hence, appropriate chemical modification methods can be selected according to the unique structural characteristics of polysaccharides to assist in enhancing and promoting the presentation of their biological activities. This review summarizes research progress on modified polysaccharides, including common chemical modification methods, the change in biological activity following modification, and the factors affecting the biological activity of chemically modified polysaccharides. At the same time, the difficulties and challenges associated with the structural modification of natural polysaccharides are also outlined in this review. Thus, research on polysaccharide structure modification is critical for improving the development and utilization of sugar products.

Guar Gum as an Eco-Friendly Corrosion Inhibitor for N80 Carbon Steel under Sweet Environment in Saline Solution: Electrochemical, Surface, and Spectroscopic Studies

In this study, the corrosion inhibition performance of the natural polysaccharide guar gum (GG) for N80 carbon steel in CO2-saturated saline solution at different temperatures and immersion times was investigated by weight loss and electrochemical measurements. The results have revealed that GG showed good inhibition performance at lower and higher temperatures. The inhibition efficiency observed via weight loss measurements reached 76.16 and 63.19% with 0.4 g L-1 of GG, at 25 and 50 °C, respectively. The inhibition efficiency of GG increased as the inhibitor concentration and immersion time increased but decreased with increasing temperature. EIS measurements have shown that, even after prolonged exposure, GG was still able to protect the metal surface. Potentiodynamic measurements showed the mixed-type nature of GG inhibitive action. The Temkin and Dubinin-Radushkevich adsorption isotherm models give accurate fitting of the estimated data, and the calculated parameters indicated that the adsorption of GG occurred mainly via an electrostatic or physical adsorption process. The associated activation energy (Ea) and the heat of adsorption (Qa) supported the physical adsorption nature of GG. FTIR analysis was used to explain the adsorption interaction between the inhibitor and the N80 carbon steel surface. SEM-EDS and AFM confirmed the adsorption of GG and the formation of an adsorptive layer of GG on the metal surface.

Thrombin and Factor Xa Hydrolysis of Chromogenic Substrates in the Presence of Sulfated Derivatives of Galactomannan and Galactoglucomannan Natural Gels

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.

Composition and Structure of Aspen (Pópulus trémula) Hemicelluloses Obtained by Oxidative Delignification

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.

Numerical Modeling of Damage Caused by Seawater Exposure on Mechanical Strength in Fiber-Reinforced Polymer Composites

Fiber-reinforced polymer composites are frequently used in marine environments which may limit their durability. The development of accurate engineering tools capable of simulating the effect of seawater on material strength can improve design and reduce structural costs. This paper presents a numerical-based approach to predict the stress–strain response of fiber-reinforced polymer composites exposed to different seawater immersion times, ranging from 0 to 900 days. A three-dimensional numerical model has been implemented using a static implicit finite element analysis along with a user-defined material (UMAT) subroutine. Puck’s failure criterion was used for ultimate failure analysis of the laminates, while Fick’s first diffusion law was used to predict the seawater absorption rate. Overall, the simulated stress–strain curves were close to those obtained experimentally. Moreover, the model agreed well with the experimental data regarding the maximum stress and the strain at failure leading to maximum errors lower than 9% and 11%, respectively. Additionally, the simulated strain fields agreed well with the experimental results measured by digital image correlation. Finally, the proposed procedure was also used to identify the most critical surfaces to protect the mechanical components from marine environments.

Design and Preparation of a Biobased Colorimetric pH Indicator from Cellulose and Pigments of Bacterial Origin, for Potential Application as Smart Food Packaging

Nowadays, worldwide challenges such as global warming, pollution, unsustainable consumption patterns, and scarcity of natural resources are key drivers toward future-oriented bioeconomy strategies, which rely on renewable biobased resources, such as bacterial pigments and bacterial cellulose (BC), for materials production. Therefore, the purpose of this study was to functionalize bacterial cellulose with violacein, flexirubin-type pigment, and prodigiosin and test their suitability as pH indicators, due to the pigments’ sensitivity to pH alterations. The screening of the most suitable conditions to obtain the BC-pigment indicators was achieved using a full factorial design, for a more sustainable functionalization process. Then, the pH response of functionalized BC to buffer solutions was assessed, with color changes at acidic pH (BC-violacein indicator) and at alkaline pH (BC-violacein, BC-prodigiosin, and BC-flexirubin-type pigment indicators). Moreover, the indicators also revealed sensitivity to acid and base vapors. Furthermore, leaching evaluation of the produced indicators showed higher suitability for aqueous foods. Additionally, color stability of the functionalized BC indicators was carried out, after light exposure and storage at 4 °C, to evaluate the indicators’ capacity to maintain color/sensitivity. Thus, BC membranes functionalized with bacterial pigments have the potential to be further developed and used as pH indicators.

Sulfation of Wheat Straw Soda Lignin with Sulfamic Acid over Solid Catalysts

Soda lignin is a by-product of the soda process for producing cellulose from grassy raw materials. Since a method for the industrial processing of lignin of this type is still lacking, several research teams have been working on solving this problem. We first propose a modification of soda lignin with sulfamic acid over solid catalysts. As solid catalysts for lignin sulfation, modified carbon catalysts (with acid sites) and titanium and aluminum oxides have been used. In the elemental analysis, it is shown that the maximum sulfur content (16.5 wt%) was obtained with the Sibunit-4® catalyst oxidized at 400 °C. The incorporation of a sulfate group has been proven by the elemental analysis and Fourier-transform infrared spectroscopy. The molecular weight distribution has been examined by gel permeation chromatography. It has been demonstrated that the solid catalysts used in the sulfation process causes hydrolysis reactions and reduces the molecular weight and polydispersity index. It has been established by the thermal analysis that sulfated lignin is thermally stabile at temperatures of up to 200 °C. According to the atomic force microscopy data, the surface of the investigated film consists of particles with an average size of 50 nm. The characteristics of the initial and sulfated β-O-4 lignin model compounds have been calculated and recorded using the density functional theory.

Sulfation of Wheat Straw Soda Lignin with Sulfamic Acid over Solid Catalysts

Soda lignin is a by-product of the soda process for producing cellulose from grassy raw materials. Since a method for the industrial processing of lignin of this type is still lacking, several research teams have been working on solving this problem. We first propose a modification of soda lignin with sulfamic acid over solid catalysts. As solid catalysts for lignin sulfation, modified carbon catalysts (with acid sites) and titanium and aluminum oxides have been used. In the elemental analysis, it is shown that the maximum sulfur content (16.5 wt%) was obtained with the Sibunit-4® catalyst oxidized at 400 °C. The incorporation of a sulfate group has been proven by the elemental analysis and Fourier-transform infrared spectroscopy. The molecular weight distribution has been examined by gel permeation chromatography. It has been demonstrated that the solid catalysts used in the sulfation process causes hydrolysis reactions and reduces the molecular weight and polydispersity index. It has been established by the thermal analysis that sulfated lignin is thermally stabile at temperatures of up to 200 °C. According to the atomic force microscopy data, the surface of the investigated film consists of particles with an average size of 50 nm. The characteristics of the initial and sulfated β-O-4 lignin model compounds have been calculated and recorded using the density functional theory.

Catalytic Sulfation of Betulin with Sulfamic Acid: Experiment and DFT Calculation

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.

Catalytic Sulfation of Betulin with Sulfamic Acid: Experiment and DFT Calculation

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.

Food Xanthan Polysaccharide Sulfation Process with Sulfamic Acid

Xanthan is an important polysaccharide with many beneficial properties. Sulfated xanthan derivatives have anticoagulant and antithrombotic activity. This work proposes a new method for the synthesis of xanthan sulfates using sulfamic acid. Various N-substituted ureas have been investigated as process activators. It was found that urea has the greatest activating ability. BBD of xanthan sulfation process with sulfamic acid in 1,4-dioxane has been carried out. It was shown that the optimal conditions for the sulfation of xanthan (13.1 wt% sulfur content) are: the amount of sulfating complex per 1 g of xanthan is 3.5 mmol, temperature 90 °C, duration 2.3 h. Sulfated xanthan with the maximum sulfur content was analyzed by physicochemical methods. Thus, in the FTIR spectrum of xanthan sulfate, in comparison with the initial xanthanum, absorption bands appear at 1247 cm-1, which corresponds to the vibrations of the sulfate group. It was shown by GPC chromatography that the starting xanthan gum has a bimodal molecular weight distribution of particles, including a high molecular weight fraction with Mw > 1000 kDa and an LMW fraction with Mw < 600 kDa. It was found that the Mw of sulfated xanthan gum has a lower value (~612 kDa) in comparison with the original xanthan gum, and a narrower molecular weight distribution and is characterized by lower PD values. It was shown by thermal analysis that the main decomposition of xanthan sulfate, in contrast to the initial xanthan, occurs in two stages. The DTG curve has two pronounced peaks, with maxima at 226 and 286 °C.