Structure and rheology of the polysaccharides from Schizymenia dubyi: Isolation of an unusual glucurono-carrageenan.

The system of polysaccharides from Schizymenia dubyi (Nemastomatales) was investigated. It contains a mixture of hybrid dl galactans (SH-S) and carrageenan-like polysaccharides, which were separated by means of precipitation with KCl at high concentrations. The structural features of the carrageenan-like fraction (SH-I) were investigated by methylation analysis, desulfation, uronic acid reduction, and NMR spectroscopy. It was concluded that the structure has the typical alternance α-(1 â†’ 3), ß-(1 â†’ 4) of d-galactose units, with most of the 3-linked units sulfated in O-2 (and some in O-4), and most of the 4-linked units sulfated in O-3, and substituted in O-2 by single stubs of ß-d-glucuronic acid (partly sulfated in each of the three available positions). This substituent has been only seldom found in red seaweed galactans. Rheological studies of 5 % and 10 % w/v SH, SH-S and SH-I aqueous systems, either without ions, or in KCl or CaCl2 solution gave thickening behaviors. Their random coil conformations justify the pseudoplastic behavior observed in the viscosity versus shear rate curves. As SH-S and SH-I are both contained in SH, an interpenetrating network could form in SH between the glucurono-carrageenan and the agaran, as inferred from the mechanical spectra recorded in water, especially with potassium ion.

Synthetic Studies on the Incorporation of N-Acetylallosamine in Hyaluronic Acid-Inspired Thiodisaccharides.

Two approaches for the synthesis of the thiodisaccharide ß-S-GlcA(1→3)ß-S-AllNAc are described here. The target disaccharide was a C-3 epimer and thio-analogue of the hyaluronic acid repetitive unit, tuned with a thiopropargyl anomeric group for further click conjugation. Thus, we analysed and tested two convenient sequences, combining the two key steps required to introduce the thioglycosidic bonds and consequently reach the target molecule: the SN2 substitution of a good leaving group (triflate) present at C-3 of a GlcNAc derivative and the introduction of the anomeric thiopropargyl substituent. The use of a 2-azido precursor showed to be a convenient substrate for the SN2 step. Nevertheless, further protecting group manipulation and the introduction of the thiopropargyl anomeric residue were then required. This approach showed to provide access to a variety of thiodisaccharide derivatives as interesting building blocks for the construction of neoglycoconjugates.

Recent Evidence of the Beneficial Effects Associated with Glucuronic Acid Contained in Kombucha Beverages.

PURPOSE OF THE REVIEW: Glucuronic acid is contained naturally in kombucha beverages due to the associations between bacteria and yeasts during its fermentation. The purpose of this review is to describe the literature related to the hepatoprotective effect associated with glucuronic acid present in different kombucha beverages. RECENT FINDINGS: Although previous research supports beneficial hepatoprotective effects of glucuronic acid consumption from kombucha, these effects are mainly attributed to the tea phytochemicals. However, there are some improvements in methodological deficiencies in some in vivo studies that should be considered. There is no sufficient evidence to generalize the adverse effects of kombucha consumption. Consumption of kombucha could be considered a safe practice in healthy populations due to its hepatoprotective effects. The content of the beneficial or toxic components is very variable because it depends on its manufacturing process. In persons with side sickness, other conditions such as pregnancy, and hypersensitivity to some kombucha components, a restriction in its consumption must be advisable.

Improving the thrombin inhibitory activity of glycyrrhizin, a triterpenic saponin, through a molecular simplification of the carbohydrate moiety.

Glycyrrhizin, a saponin, and its aglycone glycyrrhetinic acid are natural products found in the Liquorice (Glycyrrhiza glabra L.) root extract. This saponin is known for its in vitro and in vivo thrombin inhibitory activity. The design and synthesis of five glycyrrhizin derivatives were carried out to improve the natural product activity. Compound 3b, a phthalic ester derivative of glycyrrhizin, presented a more pronounced thrombin inhibition (IC50  = 114.4 ± 1.3 µm) than the saponin (IC50  = 235.7 ± 1.4 µm). Molecular docking simulations performed to investigate the molecular interaction between compound 3b and the enzyme indicate that this product is, as previously determined for glycyrrhizin, an allosteric thrombin inhibitor.