The antioxidant properties of oligo sodium alginates prepared by radiation-induced degradation in aqueous and hydrogen peroxide solutions

NaAlg-g-AA Hydrogels: Candidates in Sustainable Agriculture Applications

Nowadays, the degradation of agricultural soil due to various factors should be a major concern for everyone. In this study, a new sodium alginate-g-acrylic acid-based hydrogel was developed simultaneously by cross-linking and grafting with accelerated electrons to be used as soil remediation. The effect of irradiation dose and NaAlg contents on the gel fraction, network and structural parameters, sol-gel analysis, swelling power, and swelling kinetics of NaAlg-g-AA hydrogels have been investigated. It was demonstrated that NaAlg hydrogels show significative swelling power that is greatly dependent on their composition and irradiation dose; they keep the structure and are not degraded in different pH conditions and different water sources. Diffusion data revealed a non-Fickian transport mechanism (0.61-0.99) also specific to cross-linked hydrogels. The prepared hydrogels were proved as excellent candidates in sustainable agriculture applications.

Preparation and potential applications of alginate oligosaccharides

Alginate, a linear polymer consisting of β-D-mannuronic acid (M) and α-L-guluronic acid (G) with 1,4-glycosidic linkages and comprising 40% of the dry weight of algae, possesses various applications in the food and nutraceutical industries. However, the potential applications of alginate are restricted in some fields because of its low water solubility and high solution viscosity. Alginate oligosaccharides (AOS) on the other hand, have low molecular weight which result in better water solubility. Hence, it becomes a more popular target to be researched in recent years for its use in foods and nutraceuticals. AOS can be obtained by multiple degradation methods, including enzymatic degradation, from alginate or alginate-derived poly G and poly M. AOS have unique bioactivity and can bring human health benefits, which render them potentials to be developed/incorporated into functional food. This review comprehensively covers methods of the preparation and analysis of AOS, and discussed the potential applications of AOS in foods and nutraceuticals.

Konjac Glucomannan (KGM), Deacetylated KGM (Da-KGM), and Degraded KGM Derivatives: A Special Focus on Colloidal Nutrition

Konjac flour, mainly obtained and purified from the tubers ofAmorphophallus konjac C. Koch, yields a high molecular weight (M_w) and viscous hydrocolloidal polysaccharide: konjac glucomannan (KGM). KGM has been widely applied in the food industry as a thickening and gelation agent as a result of its unique colloidal properties of effective viscosity enhancement and thermal-irreversible gelling. This review first narrates the typical commercial KGM source species, the industrial production, and the purification process of KGM flour. The structural information on native KGM, gelation mechanisms of alkali-induced deacetylated KGM (Da-KGM) hydrogel, progress on degraded KGM derivatives, cryoprotection effect, and colloidal nutrition are highlighted. Finally, the regulatory requirements of konjac flour and KGM among different countries are briefly introduced. The fine structure and physicochemical properties of KGM can be regulated in a great range via the deacetylation or degradation reaction. Here, the relationship between the physicochemical properties, such as viscosity, solubility, gelation, and nutritional effects, of native KGM, Da-KGM, and degraded KGM derivatives was preliminary established, which would provide theoretical guidance for designing KGM-based products with certain nutritional needs.

Biophysico-Chemical Properties of Alginate Oligomers Obtained by Acid and Oxidation Depolymerization

The aim of the study was to obtain alginate oligosaccharides by using two degradation methods of sodium alginate (SA): with hydrochloric acid (G—guluronate, M—mannuronate and G + M fractions) and hydrogen peroxide (HAS—hydrolyzed SA), in order to assess and compare their biological activity and physico-chemical properties, with an attempt to produce gels from the obtained hydrolysates. The efficiency of each method was determined in order to select the fastest and most efficient process. The ferric ion reducing antioxidant power (FRAP), the ability to scavenge DPPH free radicals, rheological properties, Fourier Transformed Spectroscopy (FTIR) and the microbiological test against Escherichia coli and Staphylococcus aureus were performed. In order to check the functional properties of the obtained oligosaccharides, the texture profile analysis was assessed. The hydrolysis yield of acid SA depolymerization was 28.1% and from hydrogen peroxide SA, depolymerization was 87%. The FTIR analysis confirmed the degradation process by both tested methods in the fingerprint region. The highest ferric reducing antioxidant power was noted for HSA (34.7 µg), and the highest hydroxyl radical scavenging activity was obtained by G fraction (346 µg/Trolox ml). The complete growth inhibition (OD = 0) of alginate hydrolysates was 1%. All tested samples presented pseudoplastic behavior, only HSA presented the ability to form gel.

Low-energy electron beam sterilization of solid alginate and chitosan, and their polyelectrolyte complexes

Polysaccharidic scaffolds hold great hope in regenerative medicine, however their sterilization still remains challenging since conventional methods are deleterious. Recently, electron beams (EB) have raised interest as emerging sterilization techniques. In this context, the aim of this work was to study the impact of EB irradiations on polysaccharidic macroporous scaffolds. The effects of continuous and pulsed low energy EB were examined on polysaccharidic or on polyelectrolyte complexes (PEC) scaffolds by SEC-MALLS, FTIR and EPR. Then the scaffolds' physicochemical properties: swelling, architecture and compressive modulus were investigated. Finally, sterility and in vitro biocompatibility of irradiated scaffolds were evaluated to validate the effectiveness of our approach. Continuous beam irradiations appear less deleterious on alginate and chitosan chains, but the use of a pulsed beam limits the time of irradiation and better preserve the architecture of PEC scaffolds. This work paves the way for low energy EB tailor-made sterilization of sensitive porous scaffolds.

An Overview of Structural Aspects and Health Beneficial Effects of Antioxidant Oligosaccharides

BACKGROUND

Non-digestible oligosaccharides are versatile sources of chemical diversity, well known for their prebiotic actions, found naturally in plants or produced by chemical or enzymatic synthesis or by hydrolysis of polysaccharides. Compared to polyphenols or even polysaccharides, the antioxidant potential of oligosaccharides is still unexplored. The aim of the present work was to provide an up-to-date, broad and critical contribution on the topic of antioxidant oligosaccharides.

METHODS

The search was performed by crossing the words oligosaccharides and antioxidant. Whenever possible, attempts at establishing correlations between chemical structure and antioxidant activity were undertaken.

RESULTS

The most representative in vitro and in vivo studies were compiled in two tables. Chitooligosaccharides and xylooligosaccharides and their derivatives were the most studied up to now. The antioxidant activities of oligosaccharides depend on the degree of polymerization and the method used for depolymerization. Other factors influencing the antioxidant strength are solubility, monosaccharide composition, the type of glycosidic linkages of the side chains, molecular weight, reducing sugar content, the presence of phenolic groups such as ferulic acid, and the presence of uronic acid, among others. Modification of the antioxidant capacity of oligosaccharides has been achieved by adding diverse organic groups to their structures, thus increasing also the spectrum of potentially useful molecules.

CONCLUSION

A great amount of high-quality evidence has been accumulating during the last decade in support of a meaningful antioxidant activity of oligosaccharides and derivatives. Ingestion of antioxidant oligosaccharides can be visualized as beneficial to human and animal health.

Recent Advances in Pharmaceutical Potential of Brown Algal Polysaccharides and their Derivatives

Marine plants, animals and microorganisms display steady growth in the ocean and are abundant carbohydrate resources. Specifically, natural polysaccharides obtained from brown algae have been drawing increasing attention owing to their great potential in pharmaceutical applications. This review describes the structural and biological features of brown algal polysaccharides, including alginates, fucoidans, and laminarins, and it highlights recently developed approaches used to obtain the oligo- and polysaccharides with defined structures. Functional modification of these polysaccharides promotes their advanced applications in biomedical materials for controlled release and targeted drug delivery, etc. Moreover, brown algal polysaccharides and their derivatives possess numerous biological activities with anticancer, anticoagulant, wound healing, and antiviral properties. In addition, we also discuss carbohydrate- based substrates from brown algae, which are currently in clinical and preclinical studies, as well as the marine drugs that are already on the market. The present review summarizes the recent development in carbohydratebased products from brown algae, with promising findings that could rapidly facilitate the future discovery of novel marine drugs.