Abstract
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.
Highlights
Polysaccharides isolated from plant, animal, and bacterial raw materials have biocompatible, non-toxic, and biodegradable properties
The xanthan sulfation process was optimized, the process activators based on urea were investigated, the initial and sulfated xanthan gum was analyzed by FTIR spectroscopy, XRD, AFM, thermal analysis, and GPC
We studied the effect of the sulfating complex amount, temperature, and duration of the process on the sulfur content in xanthan sulfates
Summary
Polysaccharides isolated from plant, animal, and bacterial raw materials have biocompatible, non-toxic, and biodegradable properties. Due to these qualities, they are actively used in pharmaceutical, biomedical, food, and cosmetic purposes [1]. Modification of XG with various functional groups opens up new possibilities for its use. Modification of xanthan leads to the production of derivatives with specified characteristics of hydrophilic-hydrophobic properties for use in various fields. There is an alternative to the traditional method for the preparation of polysaccharide sulfates, based on the use of sulfamic acid in the presence of organic bases, both in the presence of organic solvents [19,20] and without them [21,22,23]. The xanthan sulfation process was optimized, the process activators based on urea were investigated, the initial and sulfated xanthan gum was analyzed by FTIR spectroscopy, XRD, AFM, thermal analysis, and GPC
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