Selenium-Containing Polysaccharides—Structural Diversity, Biosynthesis, Chemical Modifications and Biological Activity

Abstract

Selenosugars are a group of sugar derivatives of great structural diversity (e.g., molar masses, selenium oxidation state, and selenium binding), obtained as a result of biosynthesis, chemical modification of natural compounds, or chemical synthesis. Seleno-monosaccharides and disaccharides are known to be non-toxic products of the natural metabolism of selenium compounds in mammals. In the case of the selenium-containing polysaccharides of natural origin, their formation is also postulated as a form of detoxification of excess selenium in microorganisms, mushroom, and plants. The valency of selenium in selenium-containing polysaccharides can be: 0 (encapsulated nano-selenium), IV (selenites of polysaccharides), or II (selenoglycosides or selenium built into the sugar ring to replace oxygen). The great interest in Se-polysaccharides results from the expected synergy between selenium and polysaccharides. Several plant- and mushroom-derived polysaccharides are potent macromolecules with antitumor, immunomodulatory, antioxidant, and other biological properties. Selenium, a trace element of fundamental importance to human health, has been shown to possess several analogous functions. The mechanism by which selenium exerts anticancer and immunomodulatory activity differs from that of polysaccharide fractions, but a similar pharmacological effect suggests a possible synergy of these two agents. Various functions of Se-polysaccharides have been explored, including antitumor, immune-enhancement, antioxidant, antidiabetic, anti-inflammatory, hepatoprotective, and neuroprotective activities. Due to being non-toxic or much less toxic than inorganic selenium compounds, Se-polysaccharides are potential dietary supplements that could be used, e.g., in chemoprevention.

Selenium-Containing Exopolysaccharides Isolated from the Culture Medium of <em>Lentinula edodes</em>: Structure and Biological Activity

“…The results of numerous studies on the effects of selenium incorporation into polysaccharides have indicated a significant increase in their biological activity, particularly immunomodulating, anti-cancer, and antioxidant effects [52]. In our previous study on the activity of water-soluble Se-polysaccharides isolated from the L. edodes mycelium, we have also observed significant activity enhancement related to the incorporation of selenium [20].…”

“…Another interesting, but still poorly studied, problem is the selenium bonding to the structure of polysaccharides. When the chemical methods are used to enrich natural polysaccharides with selenium, the degree of oxidation of selenium and its bonding ability in Se-polysaccharides are easy to predict [52]. On the other hand, when using biotechnological methods for obtaining the Se-polysaccharides, these important structural features are practically unpredictable and impossible to reliably determine by simple spectral analysis methods (IR, UV, 13 C and 1 H NMR, etc.)…”

Selenium-Containing Exopolysaccharides Isolated from the Culture Medium of Lentinula edodes: Structure and Biological Activity

“…The results of numerous studies on the effects of selenium incorporation into polysaccharides have indicated a significant increase in their biological activity, particularly immunomodulating, anti-cancer, and antioxidant effects [ 18 ]. In our previous study on the activity of water-soluble Se-polysaccharides isolated from the L. edodes mycelium, we also observed significant activity enhancement related to the incorporation of selenium [ 25 ].…”

“…Another interesting, but still poorly studied, problem is the selenium bonding to the structure of polysaccharides. When the chemical methods are used to enrich natural polysaccharides with selenium, the degree of oxidation of selenium and its bonding ability in Se-polysaccharides are easy to predict [ 18 ]. On the other hand, when using biotechnological methods for obtaining the Se-polysaccharides, these important structural features are practically unpredictable and impossible to reliably determine by simple spectral analysis methods (IR, UV, 13 C and 1 H NMR, etc.)…”

“…Therefore, it has been hypothesized that the introduction of selenium to the polysaccharide structure would increase the immunomodulatory activity. Although the increased activity of polysaccharides resulting from selenium incorporation has been confirmed by studies conducted in many research laboratories, the mechanism of this action is still unclear [ 18 ].…”