O-Succinyl derivative of ι-carrageenan fragments: Synthesis and characterization

Chemically modified seaweed polysaccharides: Improved functional and biological properties and prospective in food applications

Seaweed polysaccharides are natural biomacromolecules with unique physicochemical properties (e.g., good gelling, emulsifying, and film-forming properties) and diverse biological activities (e.g., anticoagulant, antioxidant, immunoregulatory, and antitumor effects). Furthermore, they are nontoxic, biocompatible and biodegradable, and abundant in resources. Therefore, they have been widely utilized in food, cosmetics, and pharmaceutical industries. However, their properties and bioactivities sometimes are not satisfactory for some purposes. Modification of polysaccharides can impart the amphiphilicity and new functions to the biopolymers and change the structure and conformation, thus effectively improving their functional properties and biological activities so as to meet the requirement for targeted applications. This review outlined the modification methods of representative red algae polysaccharides (carrageenan and agar), brown algae polysaccharides (fucoidan, alginate, and laminaran), and green algae polysaccharides (ulvan) that have potential food applications, including etherification, esterification, degradation, sulfation, phosphorylation, selenylation, and so on. The improved functional properties and bioactivities of the modified seaweed polysaccharides and their potential food applications are also summarized.

Formation of Amphiphilic Molecules from the Most Common Marine Polysaccharides, toward a Sustainable Alternative?

Marine polysaccharides are part of the huge seaweeds resources and present many applications for several industries. In order to widen their potential as additives or bioactive compounds, some structural modifications have been studied. Among them, simple hydrophobization reactions have been developed in order to yield to grafted polysaccharides bearing acyl-, aryl-, alkyl-, and alkenyl-groups or fatty acid chains. The resulting polymers are able to present modified physicochemical and/or biological properties of interest in the current pharmaceutical, cosmetics, or food fields. This review covers the chemical structures of the main marine polysaccharides, and then focuses on their structural modifications, and especially on hydrophobization reactions mainly esterification, acylation, alkylation, amidation, or even cross-linking reaction on native hydroxyl-, amine, or carboxylic acid functions. Finally, the question of the necessary requirement for more sustainable processes around these structural modulations of marine polysaccharides is addressed, considering the development of greener technologies applied to traditional polysaccharides.

Investigation of the transport and absorption of Angelica sinensis polysaccharide through gastrointestinal tract both in vitro and in vivo

To investigate the absorption and delivery of ASP in gastrointestinal (GI) tract, cASP was successfully synthesized by chemically modifying with succinic anhydride and then conjugating with a near infrared fluorescent dye Cy5.5. Then, the capacity of oral absorption of cASP was evaluated. The results demonstrated that cASP had low toxicity and no disruption on the integrity of cell membrane. The endocytosis of cASP into the epithelial cells was time- and energy-dependent, which was mediated by macropinocytosis pathway and clathrin- and caveolae (or lipid raft)-related routes. Otherwise, the actin filaments played a relatively weak role at the same time. The transport study illustrated that cASP could penetrate through the epithelial monolayer and mainly mediated by the same routes as that in the endocytosis experiment. Moreover, both in vitro Ussing chamber and in vivo ligated intestinal loops models indicated that cASP could be diffused through the mucus barriers and be absorbed in the whole small intestine. Finally, near-infrared fluorescence imaging presented that cASP could be absorbed and circulated into the blood, then distributed into various organs after oral administration. In conclusion, ASP could be absorbed after oral administration through endocytosis process mainly mediated by macropinocytosis pathway and clathrin- and caveolae (or lipid raft)-related routes, then be absorbed and circulated into blood. This study presents a comprehensive understanding of oral delivery of cASP, which will provide theoretical basis for the clinical application of ASP.

Partial and total C-6 oxidation of gelling carrageenans. Modulation of the antiviral activity with the anionic character

The optimal conditions for the full C-6 oxidation of κ- and ι-carrageenans using (2,2,6,6-tetramethylpiperidinyl)oxy (TEMPO) in the presence of sodium hypochlorite and sodium bromide were assessed. The fully oxidized products were characterized by NMR spectroscopy. Partially oxidized products were also obtained and analyzed by chemical and spectroscopical methods. The antiviral activity of carrageenans against herpes simplex virus HSV-1 and HSV-2 determined by plaque reduction assay, was not largely affected by full oxidation of the polysaccharides, but an increase in activity was detected by partial oxidation. A specific overoxidation on C-2 of the 3,6-anhydrogalactose moiety of κ-carrageenan was identified, solved experimentally and rationalized through the application of molecular modeling.