Salt Effect on the Antioxidant Activity of Red Microalgal Sulfated Polysaccharides in Soy-Bean Formula

Sulfated polysaccharides produced by microalgae, which are known to exhibit various biological activities, may potentially serve as natural antioxidant sources. To date, only a few studies have examined the antioxidant bioactivity of red microalgal polysaccharides. In this research, the effect of different salts on the antioxidant activities of two red microalgal sulfated polysaccharides derived from Porphyridium sp. and Porphyridium aerugineum were studied in a soy bean-based infant milk formula. Salt composition and concentration were both shown to affect the polysaccharides’ antioxidant activity. It can be postulated that the salt ions intefer with the polysaccharide chains’ interactions and alter their structure, leading to a new three-dimensional structure that better exposes antiooxidant sites in comparison to the polysaccharide without salt supplement. Among the cations that were studied, Ca2+ had the strongest enhancement effect on antioxidant activities of both polysaccharides. Understanding the effect of salts on polysaccharides’ stucture, in addition to furthering knowledge on polysaccharide bioactivities, may also shed light on the position of the antioxidant active sites

Green Procedure for Aerobic Oxidation of Benzylic Alcohols with Palladium Supported on Iota-Carrageenan in Ethanol

The search for selective heterogeneous catalysts for the aerobic oxidation of alcohols to ketones and aldehydes has drawn much attention in the last decade. To that end, different palladium-based catalysts have been proposed that use various organic and inorganic supports. In addition, supports that originate from a biological and renewable source that is also nontoxic and biodegradable were found to be superior. We heterogenized palladium chloride or acetate complexes with triphenylphosphine trisulfonate on iota-carrageenan xerogel by simple mixing of the complex and the polysaccharide in water. The resulting polysaccharide-catalyst mixture then underwent deep freeze and lyophilization, after which the catalyst was characterized by TEM, XPS and SEM-EDS and tested in aerobic oxidation. The new heterogeneous catalysts were successfully used for the first time in the aerobic oxidation of benzylic alcohols. Moreover, they were easily removed from the reaction mixture and recycled, yielding an increase in activity with each subsequent reuse. As determined by TEM and XPS, the reduction in palladium and the formation of nanoparticles during the reaction in ethanol yielded more active species and, therefore, higher conversion rates. A SEM-EDS analysis indicated that the palladium was thoroughly dispersed in the xerogel catalysts. Moreover, the xerogel catalyst was observed to undergo a structural change during the reaction. To conclude, the new heterogeneous catalyst was prepared by a simple and straightforward method that used a non-toxic, renewable and biodegradable support to yield an active, selective and recyclable heterogeneous system

Pd-Based Polysaccharide Hydrogels as Heterogeneous Catalysts for Oxidation of Aromatic Alcohols

Immobilization of Pd(OAc)2(TPPTS)2 in various renewable polysaccharides hydrogels, yielded heterogeneous catalysts that were successfully used, for the first time, in the aerobic oxidation of benzylic alcohol. The new catalysts were easily removed from the reaction mixture and recycled with some loss of activity. Among all tested polysaccharides, iota-carrageenan was found to be the most suitable support, using calcium chloride as a gelation agent

Studying the Relationship between the Antiviral Activity and the Structure of ἰ-Carrageenan Using Ultrasonication

ἰ-carrageenan is a linear macroalgal polysaccharide that is well known for its antiviral bioactivity. Although it is considered a candidate for antiviral therapeutics, its application is highly limited due to its low solubility and high viscosity, which lower its adsorption efficiency. With the aim of deriving an active ἰ-carrageenan fragment with an improved adsorption capacity, we studied the effects of ultrasonication on structural changes in ἰ-carrageenan with respect to changes in its bioactivity against herpesviruses. An FTIR analysis revealed that ultrasonication increased the hydrophilicity of ἰ-carrageenan without changing its functional groups, and a rheological analysis demonstrated that it gradually decreased the strength of the polysaccharide gel, which completely lost its gel structure and formed small nanoparticles after 30 min of ultrasonication. Concomitantly with these physicochemical changes, a plaque assay revealed that longer ultrasonication increased the antiviral activity of ἰ-carrageenan against two herpesviruses, namely, HSV-1 and VZV. Finally, we separated the 30-min ultrasonicated ἰ-carrageenan into four fractions and found that fractions with a lower molecular weight were significantly less active against both herpesviruses than those with a higher molecular weight. Our findings show that ultrasonication induces physicochemical changes in ἰ-carrageenan that increase its antiviral bioactivity

Renewable Polysaccharides as Supports for Palladium Phosphine Catalysts

The investigation of the use of polysaccharides derived from natural sources to support metal catalysis has been the focus of several studies. Even though these molecules seem to be attractive materials, their full potential for use in support of heterogeneous catalysis still needs to be revealed. To that end, we developed a new preparation technique for polysaccharide-based palladium catalysts by immobilizing the palladium phosphine complexes on various renewable polysaccharides. The Suzuki cross-coupling in ethanol, using PdCl2(TPPTS)2 supported by various polysaccharides, was determined by gas chromatography and compared to homogeneous free-catalyst support. The PdCl2(TPPTS)2, that was immobilized on red algae supports, was successfully used as a heterogeneous catalyst in the Suzuki cross-coupling reaction, yielding high activity, higher than that of the homogeneous complex, without leaching. The FTIR spectrometry of representative heterogeneous polysaccharide-based TPPTS–PdCl2 catalysts was compared to that of native polysaccharide and polysaccharide-based TPP–PdCl2 catalysts, indicated on new bands, suggesting that the heterogenization occurs via interactions between the sulfonate group on the TPPTS and the hydroxyl groups on the polysaccharides. EDS and XPS analysis were also performed, confirming that the Pd complex was embedded within the i-carrageenan. A comparison of SEM images of i-carrageenan preparations also shed light on the interaction occurring between the polysaccharides and the TPPTS

Fragmentation of negative ions from N-linked carbohydrates: Part 6. Glycans containing one <i>N</i>-acetylglucosamine in the core

RATIONALE: Negative ion collision-induced dissociation (CID) spectra of N-glycans contain many diagnostic ions that provide more structural information than positive ion spectra. EndoH or endoS release of glycans from glycoproteins, as used by many investigators, cleaves glycans between the GlcNAc residues of the chitobiose core leaving the glycan without the reducing-terminal GlcNAc residue. However, their negative ion CID spectra do not appear to have been studied in detail. This paper examines the CID and ion mobility properties of these endoH-released glycans to determine if the missing GlcNAc influences the production of diagnostic fragment ions. METHODS: N-Glycans were released from ribonuclease B, ovalbumin and gp120 with endoH to give high-mannose and hybrid glycans, and from IgG with endoS to produce biantennary complex glycans, all missing the reducing-terminal GlcNAc residue. Negative ion CID and travelling wave ion mobility spectra were recorded with a Waters Synapt G2 mass spectrometer using nanospray sample introduction. RESULTS: The majority of glycans yielded CID spectra exhibiting the same diagnostic fragments, which were equivalently informative, as the fully released structures. However, the ability of ion mobility to separate isomers was generally found to be inferior to its use with the full glycans despite the smaller nature of the compounds. The exception was the partial resolution of a pair of biantennary monogalactosylated glycans from IgG where, as chloride adducts, slight separation of the isomers was observed. CONCLUSIONS: The results show that the CID spectra of endoH- and endoS-released glycans are as useful as the corresponding spectra of the intact glycans (as released by PNGase F) in providing structural information on N-glycans