Improved antioxidant and immunomodulatory activities of enzymatically degraded Porphyra haitanensis polysaccharides

Directed preparation of algal oligosaccharides with specific structures by algal polysaccharide degrading enzymes

Seaweed polysaccharides have a wide range of sources and rich content, with various biological activities such as anti-inflammatory, anti-tumor, anticoagulant, and blood pressure lowering. They can be applied in fields such as food, agriculture, and medicine. However, the poor solubility of macromolecular seaweed polysaccharides limits their further application. Reports have shown that some biological activities of seaweed oligosaccharides are more extensive and superior to that of seaweed polysaccharides. Therefore, reducing the degree of polymerization of polysaccharides will be the key to the high value utilization of seaweed polysaccharide resources. There are three main methods for degrading algal polysaccharides into algal oligosaccharides, physical, chemical and enzymatic degradation. Among them, enzymatic degradation has been a hot research topic in recent years. Various types of algal polysaccharide hydrolases and related glycosidases are powerful tools for the preparation of algal oligosaccharides, including α-agarases, β-agaroses, α-neoagarose hydrolases and β-galactosidases that are related to agar, κ-carrageenases, ι-carrageenases and λ-carrageenases that are related to carrageenan, β-porphyranases that are related to porphyran, funoran hydrolases that are related to funoran, alginate lyases that are related to alginate and ulvan lyases related to ulvan. This paper describes the bioactivities of agar oligosaccharide, carrageenan oligosaccharide, porphyran oligosaccharide, funoran oligosaccharide, alginate oligosaccharide and ulvan oligosaccharide and provides a detailed review of the progress of research on the enzymatic preparation of these six oligosaccharides. At the same time, the problems and challenges faced are presented to guide and improve the preparation and application of algal oligosaccharides in the future.

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.

Recent progress in Porphyra haitanensis polysaccharides: Extraction, purification, structural insights, and their impact on gastrointestinal health and oxidative stress management

Porphyra haitanensis, a red seaweed species, represents a bountiful and sustainable marine resource. P. haitanensis polysaccharide (PHP), has garnered considerable attention for its numerous health benefits. However, the comprehensive utilization of PHP on an industrial scale has been limited by the lack of comprehensive information. In this review, we endeavor to discuss and summarize recent advancements in PHP extraction, purification, and characterization. We emphasize the multifaceted mechanisms through which PHP promotes gastrointestinal health. Furthermore, we present a summary of compelling evidence supporting PHP's protective role against oxidative stress. This includes its demonstrated potent antioxidant properties, its ability to neutralize free radicals, and its capacity to enhance the activity of antioxidant enzymes. The information presented here also lays the theoretical groundwork for future research into the structural and functional aspects of PHP, as well as its potential applications in functional foods.

Polysaccharides from Porphyra haitanensis: A Review of Their Extraction, Modification, Structures, and Bioactivities

Porphyra haitanensis (P. haitanensis), an important food source for coastal residents in China, has a long history of medicinal and edible value. P. haitanensis polysaccharides are some of the main active ingredients in P. haitanensis. It is worth noting that P. haitanensis polysaccharides have a surprising and satisfactory biological activity, which explains the various benefits of P. haitanensis to human health, such as anti-oxidation, immune regulation, anti-allergy, and anticancer properties. Hence, a systematic review aimed at comprehensively summarizing the recent research advances in P. haitanensis polysaccharides is necessary for promoting their better understanding. In this review, we systematically and comprehensively summarize the research progress on the extraction, purification, structural characterization, modification, and biological activity of P. haitanensis polysaccharides and address the shortcomings of the published research and suggest area of focus for future research, providing a new reference for the exploitation of polysaccharides from P. haitanensis in the fields of medicine and functional foods.

Impact of Simulated Human Gastrointestinal Digestion on the Functional Properties of Dietary Fibres Obtained from Broccoli Leaves, Grape Stems, Pomegranate and Tomato Peels

This study aimed to analyse the impact of a simulated human digestion process on the composition and functional properties of dietary fibres derived from pomegranate-peel, tomato-peel, broccoli-stem and grape-stem by-products. For this purpose, a computer-controlled simulated digestion system consisting of three bioreactors (simulating the stomach, small intestine and colon) was utilised. Non-extractable phenols associated with dietary fibre and their influence on antioxidant capacity and antiproliferative activity were investigated throughout the simulated digestive phases. Additionally, the modifications in oligosaccharide composition, the microbiological population and short-chain fatty acids produced within the digestion media were examined. The type and composition of each dietary fibre significantly influenced its functional properties and behaviour during intestinal transit. Notably, the dietary fibre from the pomegranate peel retained its high phenol content throughout colon digestion, potentially enhancing intestinal health due to its strong antioxidant activity. Similarly, the dietary fibre from broccoli stems and pomegranate peel demonstrated anti-proliferative effects in both the small and the large intestines, prompting significant modifications in colonic microbiology. Moreover, these fibre types promoted the growth of bifidobacteria over lactic acid bacteria. Thus, these results suggest that the dietary fibre from pomegranate peel seems to be a promising functional food ingredient for improving human health.

In vitro-simulated intestinal flora fermentation of Porphyra haitanensis polysaccharides obtained by different assisted extractions and their fermented products against HT-29 human colon cancer cells

Herein, we studied the in vitro-simulated intestinal flora fermentation of Porphyra haitanensis polysaccharides (PHPs) with microwave, ultrasonic, ultra-high pressure-assisted extraction and the protective effect of their fermented products against HT-29 human colon cancer cells. The results showed that PHPs were largely degraded at the 18 h stage of ascending colon fermentation, further greatly increasing the contents of reducing sugars and short-chain fatty acids (p < 0.05). Particularly, the PHPs subjected to ultra-high pressure-assisted extraction (UHP-PHP) showed the highest reducing sugar content of 1.68 ± 0.01 mg mL-1 and butyric acid content of 410.77 ± 7.99 mmol mL-1. Moreover, UHP-PHP showed a better effect in increasing the ratio of Bacteroidetes/Firmicutes and decreasing the abundance of Proteobacteria and Escherichia coli. PHPs could protect against HT-29 cells by increasing the ROS levels in a concentration-dependent manner, especially UHP-PHP fermented in a descending colon for 24 h. This was related to the up-regulated apoptosis-related genes (Bax and Bak), down-regulated protein expression of Bcl-2 and activation of the p-AKT protein, thereby promoting the apoptosis of HT-29 cells. Our results can facilitate the modification of PHPs and their practical application in the development of intestinal health improving products.

Exploring the partial degradation of polysaccharides: Structure, mechanism, bioactivities, and perspectives

Polysaccharides are promising biomolecules with lowtoxicity and diverse bioactivities in food processing and clinical drug development. However, an essential prerequisite for their applications is the fine structure characterization. Due to the complexity of polysaccharide structure, partial degradation is a powerful tool for fine structure analysis, which can effectively provide valid information on the structure of backbone and branching glycosidic fragments of complex polysaccharides. This review aims to conclude current methods of partial degradation employed for polysaccharide structural characterization, discuss the molecular mechanisms, and describe the molecular structure and solution properties of degraded polysaccharides. In addition, the effects of polysaccharide degradation on the conformational relationships between the molecular structure and bioactivities, such as antioxidant, antitumor, and immunomodulatory activities, are also discussed. Finally, we summarize the prospects and current challenges for the partial degradation of polysaccharides. This review will be of great value for the scientific elucidation of polysaccharide fine structures and potential applications.

Porphyra haitanensis Polysaccharides Attenuates Blood Lipid via Gut-Liver Axis in Diet-Induced High-Fat Mesocricetus auratus through Multiple Integrated Omics

SCOPE

Hyperlipidemia is currently a global public health problem severely affecting people's physical and mental health, as well as their quality of life.

METHODS AND RESULTS

The present study is aimed at revealing the mechanism of Porphyra haitanensis polysaccharide (PHP) in decreasing blood lipids by acting through gut-liver axis in Mesocricetus auratus fed a high-fat diet. PHP significantly prevented increases in serum total cholesterol, triglycerides and low-density lipoprotein cholesterol, and alleviated damage to liver cells induced by a high-fat diet M. auratus, in a dose-dependent manner. PHP promotes proliferation of Muribaculaceae and Faecalibaculum, thereby enhancing the production of butyric acid both in the colon and liver, particularly high-dose PHP (HPHP). Low-dose PHP (LPHP) promotes the expression of phosphatidylcholine metabolites and fatty acid transport genes, and inhibits the expression of genes involved in fat degradation (Abhd5), adipogenesis (Me1), fatty acid synthesis (Fasn and Pnpla3), and fatty acid chain elongation (Elovl6) in the liver. However, HPHP inhibits the expression of triglyceride metabolites and promotes the expression of fatty acid transporter (CD36), fatty acid oxidation (Acacb), and peroxisome proliferator-activated receptor gamma (PPARg) genes in the liver.

CONCLUSION

PHP regulates lipid metabolism through the gut microbiota, and the gut-liver axis plays an important role in its hypolipidemic effects.

Polysaccharides Derived from Mushrooms in Immune and Antitumor Activity: A Review

Mushrooms are full of nutrition and have beneficial properties for human health. Polysaccharides are the main component of edible and medicinal mushrooms, especially β-glucans, which have attracted much more attention for their complex structure and diverse biological activities. Among all the diverse medicinal activities of mushroom polysaccharides, antitumor and immune-enhancing activities are two excellent bioactivities that have much more potential and deserve application. Their bioactivities are highly dependent on their structural features, including molecular weight, monosaccharide composition, degree of branching, type and configuration of glycosidic bonds, substituent pattern, and chain conformation. This review summarizes the current method for obtaining polysaccharides from mushrooms, chemical characterizations of the structures and their roles in immune and antitumor activities. In addition, the methods for preparation of the polysaccharide derivatives and the potential medicinal clinical application are also discussed in this review, which may provide new guidance for mushroom polysaccharide development.

Extraction optimization, purification, and biological properties of polysaccharide from Chinese yam peel

In this study, the Chinese yam peel polysaccharide (CYPP) was obtained under the extraction conditions optimized by the Response Surface Methodology (RSM). Further biological properties of CYPP-1 purified from CYPP were also determined. The results indicated that the optimum extraction conditions were an extraction temperature of 90.5°C, a liquid-solid ratio of 28.0 ml/g, and an extraction time of 2.94 h, along with a yield of 8.81 ± 1.48%. CYPP-1 was identified as a kind of heteropolysaccharide mostly composed of glucose and galactose (59.4:1.0). The molecular weights were two main parts of 50.5 kDa (54.77%) and 4.4 kDa (21.02%), and the triple-helix conformation was not formed in CYPP-1. Besides, CYPP-1 showed good biological properties including in vitro antioxidant activity and immunomodulatory function on RAW264.7 cells, as well as favorable hypoglycemic effect. Overall, the high-value utilization of CYPP-1 reveals a broad application prospect in the industrial production of functional foods and pharmaceuticals. PRACTICAL APPLICATIONS: Yam peel, which is discarded in large quantities during postharvest processing, results in the production of tremendous by-products and is a great waste of resources. In this study, the yield of water-soluble polysaccharide from yam peel reached 8.81 ± 1.48%. Besides, the purified CYPP-1 exhibited excellent antioxidant activity, favorable immunomodulatory function, and hypoglycemic effect. The high productivity and bioactive effects are both great merits for Chinese yam peel polysaccharide as a promising candidate for foods and medicines industrial production.

A deep eutectic solvent magnetic molecularly imprinted polymer for extraction of laminarin from seaweeds

Magnetic molecular imprinted polymers (MIPs) based on 4-vinylbenzyltrimethylammonium chloride (VBTAC) and 4-vinylbenzoic acid (VBA) deep eutectic solvent as dual functional monomers was successfully synthesized for the specific recognition of laminarin. The MIPs were characterized by transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis, and vibrating sample magnetometer analysis. The results showed that the MIPs were spheres of a uniform size, with the surface rich in cavities and excellent superparamagnetism properties. The adsorption experiments showed that MIPs conform to pseudo-second-order kinetics and Langmuir isotherm adsorption. The maximum adsorption capacity under optimal conditions was 322.58 μg·mg^-1 and the imprinting factor was 2.13. Under the optimized conditions, the limit of detection (LOD) of the developed material was 6.6 µM. Linearity of the material was obtained within the range 20-800 µM with a coefficient of determination (r²) being better 0.999. Relative standard deviations (RSDs) were less than 3.96%, and satisfactory recoveries were between 94.55 and 97.39%. The actual sample analysis manifested that MIPs could effectively separate laminarin from Laminarin japonica Aiesch.

Bioinformatic Prediction and Characterization of Proteins in Porphyra dentata by Shotgun Proteomics

Porphyra dentata is an edible red seaweed with high nutritional value. It is widely cultivated and consumed in East Asia and has vast economic benefits. Studies have found that P. dentata is rich in bioactive substances and is a potential natural resource. In this study, label-free shotgun proteomics was first applied to identify and characterize different harvest proteins in P. dentata. A total of 13,046 different peptides were identified and 419 co-expression target proteins were characterized. Bioinformatics was used to study protein characteristics, functional expression, and interaction of two important functional annotations, amino acid, and carbohydrate metabolism. Potential bioactive peptides, protein structure, and potential ligand conformations were predicted, and the results suggest that bioactive peptides may be utilized as high-quality active fermentation substances and potential targets for drug production. Our research integrated the global protein database, the first time bioinformatic analysis of the P. dentata proteome during different harvest periods, improves the information database construction and provides a framework for future research based on a comprehensive understanding.

Statistical Optimization of Novel Medium to Maximize the Yield of Exopolysaccharide From Lacticaseibacillus rhamnosus ZFM216 and Its Immunomodulatory Activity

The traditional media used for the fermentation of Lactobacilli always contain carbohydrate polymers, which interfere with the analysis of the exopolysaccharide (EPS) produced by the bacteria. In this investigation, a novel medium formulation that could avoid such interference was successfully developed. The beef extract, yeast extract, and peptone used in this formulation were subjected to the removal of polysaccharides before use. The factors affecting the EPS production were optimized by a single factor test, Plackett–Burman design, and Box–Behnken design. The optimum formula was ascertained as: 7.5 g L–1 yeast extract, 12.5 g L–1 beef extract, 10 g L–1 peptone, 21.23 g L–1 maltose, 5.51 g L–1 yeast nitrogen base, 2 g L–1 K2HPO4, 5 g L–1 anhydrous sodium acetate, 2 g L–1 ammonium citrate, 0.58 g L–1 MgSO4⋅7H2O, 0.25 g L–1 MnSO4⋅H2O, and 1 mL L–1 Tween 80. The initial pH of the medium was 6.5. The optimized conditions for fermentation of the strain to produce EPS were as follows: seed size 1%, culture temperature 37°C, and culture time 20 h. Optimum results showed that EPS yield was 496.64 ± 3.15 mg L–1, being 76.70% higher than that of unoptimized conditions (281.07 ± 5.90 mg L–1). The EPS was mainly comprised of glucose and guluronic acid, with a weight average molecular weight of 19.9 kDa; it was also characterized by Fourier transform infrared spectroscopy and UV analysis. EPS was found to significantly enhance the phagocytic capacity, promote the NO, TNF-α, IL-1β, and IL-6 secretion, and improve mRNA expression of cytokines in RAW 264.7 macrophages, indicating its considerable immunomodulatory activity. Western bolt and immunofluorescence results demonstrated that the EPS was able to increase p65 nuclear translocation in the macrophages, indicating that EPS enhanced immunity via the NF-κB signaling pathway. EPS investigated in this work has potential as an attractive functional food supplement candidate for the hypoimmunity population.

Antiviral Activities of Algal-Based Sulfated Polysaccharides

An antiviral agent is urgently needed based on the high probability of the emergence and re-emergence of future viral disease, highlighted by the recent global COVID-19 pandemic. The emergence may be seen in the discovery of the Alpha, Beta, Gamma, Delta, and recently discovered Omicron variants of SARS-CoV-2. The need for strategies besides testing and isolation, social distancing, and vaccine development is clear. One of the strategies includes searching for an antiviral agent that provides effective results without toxicity, which is well-presented by significant results for carrageenan nasal spray in providing efficacy against human coronavirus-infected patients. As the primary producer of sulfated polysaccharides, marine plants, including macro- and microalgae, offer versatility in culture, production, and post-isolation development in obtaining the needed antiviral agent. Therefore, this review will describe an attempt to highlight the search for practical and safe antiviral agents from algal-based sulfated polysaccharides and to unveil their features for future development.

Bioactive polysaccharides from red seaweed as potent food supplements: a systematic review of their extraction, purification, and biological activities

Most marine macroalgae such as red seaweeds are potential alternative sources of useful bioactive compounds. Beside serving as food source, recent studies have shown that red seaweeds are rich sources of bioactive polysaccharides. Red seaweed polysaccharides (RSPs) have various physiological and biological activities, which allow them to be used as immunomodulators, anti-obesity agents, and prebiotic ingredients. Lack of summary information and human clinical trials on the various polysaccharides from red seaweeds, however limits industrial-scale utilization of RSPs in functional foods. This review summarizes recent information on the approaches used for RSPs extraction and purification, mechanistic investigations of their biological activities, and related molecular principles behind their purported ability to prevent diseases. The information here also provides a theoretical foundation for further research into the structure and mechanism of action of RSPs and their potential applications in functional foods.

Degraded polysaccharides from Porphyra haitanensis: purification, physico-chemical properties, antioxidant and immunomodulatory activities

To explore effect of the structural properties of porphyra haitanensis polysaccharide on its biological activity, degraded porphyra polysaccharides were separated and purified by Cellulose DEAE-52 and Sephadex G-100 chromatography, obtaining three purified components (P1, P2 and P3). All the three components were sulfate polysaccharides containing the repeating units of → 3) β-D-galactose (1 → 4) 3,6-anhydro-α-L-galactose (1 →, and → 3) β-D-galactose (1 → 4) α-L-galactose-6-S (1 →, and → 3) 6-O-methyl-β-D-galactose (1 → 4) 3,6-anhydro-α-L-galactose (1 →. The molecular weight of the three fractions was measured to be 300.3, 130.4 and 115.1 kDa, respectively. Their antioxidant activity was investigated by the determination of the free radical scavenging effect and ferric reducing power. It was found that P1, P2 and P3 possessed marked antioxidant activity. It was also found that they appreciably enhanced the proliferation, phagocytic ability and nitric oxide secretion in RAW264.7 cells. Lower molecular weight and higher sulfate content were beneficial to bioactivities of P. haitanensis polysaccharides. Overall, P2 and P3 possess superior immuno-modulatory activity to that of P1 and PHP. Thus, the current work will provide the basis for the better utilization of P. haitanensis to develop the related functional foods.

Seaweed polysaccharides: Emerging extraction technologies, chemical modifications and bioactive properties

Nowadays, consumers are increasingly aware of the relationship between diet and health, showing a greater preference of products from natural origin. In the last decade, seaweeds have outlined as one of the natural sources with more potential to obtain bioactive carbohydrates. Numerous seaweed polysaccharides have aroused the interest of the scientific community, due to their biological activities and their high potential on biomedical, functional food and technological applications. To obtain polysaccharides from seaweeds, it is necessary to find methodologies that improve both yield and quality and that they are profitable. Nowadays, environmentally friendly extraction technologies are a viable alternative to conventional methods for obtaining these products, providing several advantages like reduced number of solvents, energy and time. On the other hand, chemical modification of their structure is a useful approach to improve their solubility and biological properties, and thus enhance the extent of their potential applications since some uses of polysaccharides are still limited. The present review aimed to compile current information about the most relevant seaweed polysaccharides, available extraction and modification methods, as well as a summary of their biological activities, to evaluate knowledge gaps and future trends for the industrial applications of these compounds.Key teaching pointsStructure and biological functions of main seaweed polysaccharides.Emerging extraction methods for sulfate polysaccharides.Chemical modification of seaweeds polysaccharides.Potential industrial applications of seaweed polysaccharides.Biological activities, knowledge gaps and future trends of seaweed polysaccharides.

Molecular weight effects of low acyl gellan gum on antioxidant capacity and rheological properties

The current study investigated the antioxidant capacity of enzymatically cleaved low acyl gellan gum (LA-GAGR) fragments, named midi-GAGR (MW_v : 1.2 × 10⁵  Da) and mini-GAGR (MW_v : 2.5 × 10⁴  Da). Three different methods-hydroxide assay, superoxide assay, and DPPH assay-were used to measure the antioxidant capacity of the low acyl gellan gum fragments. Both mini-GAGR and midi-GAGR showed similar antioxidant capacities, 27.1% and 25.6%, respectively, for hydroxide radicals, whereas ascorbic acid showed 9.8%. For superoxide radicals, the fragments scavenged 41.7% (mini) and 35.6% (midi) of free radicals compared to 10.6% removal by ascorbic acid. Mini- and midi-GAGR displayed modest scavenging capabilities with DPPH radicals (8.5% and 6.6%, respectively) as compared to ascorbic acid (96.3%). Both midi- and mini-GAGR showed less gel-like behaviors than LA-GAGR. Midi-GAGR was observed to have a transition from liquid to gel at 63 rad/s. PRACTICAL APPLICATION: The results in the manuscript are helpful when gellan gum and its derivatives are directly applied to food processing as a dietary fiber supplement or a stabilizer for functional beverages. The antioxidant capacity results can be used to promote the functionality of gellan gum as a food additive and for controlling cell adhesion and growth on gellan gum scaffolds. The rheology results will be useful for synthesis of scaffolds for bone tissue generation and facilitating clinical treatments when gellan gum is injected as an adsorbent or a filler for treating bone fractures. In the pharmaceutical industry, they are useful when controlling the therapeutic effects of drug delivery systems.

Structural characterization and in vitro fermentation by rat intestinal microbiota of a polysaccharide from Porphyra haitanensis

A sulfated polysaccharide (PHP1) produced by the marine red alga Porphyra haitanensis was structurally characterized, and its effect on rat fecal microbiota fermentations and short chain fatty acids production were investigated. PHP1 was mainly composed of galactose and the main linkage types were identified as → 3)G4Sβ(1 → 3)G(1 → 6)G4Sα(1 → 4)LA(1 → 6)G4Sα(1→. The surface morphology of dried PHP1 films appears to be related to its chemical structure. PHP1 promoted the growth of both propionic acid-producing bacteria and propionic acid production, as well as influencing the composition and abundance of beneficial microbiota species in rats, which may be related to its high level of sulfation. The molecular weight of PHP1 decreased significantly after fermentation, which may result from hydrolysis of the galactan (with α- and β-linkages between galactose residues) by α- or β-galactosidase secreted by the microbiota. These results provided new insights into the structure-activity relationships between P. haitanensis polysaccharide and its regulation of microbiota in vivo.

Strategies to Increase the Biological and Biotechnological Value of Polysaccharides from Agricultural Waste for Application in Healthy Nutrition

Nowadays, there is a growing interest in the extraction and identification of new high added-value compounds from the agro-food industry that will valorize the great amount of by-products generated. Many of these bioactive compounds have shown beneficial effects for humans in terms of disease prevention, but they are also of great interest in the food industry due to their effect of extending the shelf life of foods by their well-known antioxidant and antimicrobial activity. For this reason, an additional research objective is to establish the best conditions for obtaining these compounds from complex by-product structures without altering their activity or even increasing it. This review highlights recent work on the identification and characterization of bioactive compounds from vegetable by-products, their functional activity, new methodologies for the extraction of bioactive compounds from vegetables, possibly increasing their biological activity, and the future of the global functional food and nutraceuticals market.

On the Health Benefits vs. Risks of Seaweeds and Their Constituents: The Curious Case of the Polymer Paradigm

To exploit the nutraceutical and biomedical potential of selected seaweed-derived polymers in an economically viable way, it is necessary to analyze and understand their quality and yield fluctuations throughout the seasons. In this study, the seasonal polysaccharide yield and respective quality were evaluated in three selected seaweeds, namely the agarophyte Gracilaria gracilis, the carrageenophyte Calliblepharis jubata (both red seaweeds) and the alginophyte Sargassum muticum (brown seaweed). It was found that the agar synthesis of G. gracilis did not significantly differ with the seasons (27.04% seaweed dry weight (DW)). In contrast, the carrageenan content in C. jubata varied seasonally, being synthesized in higher concentrations during the summer (18.73% DW). Meanwhile, the alginate synthesis of S. muticum exhibited a higher concentration (36.88% DW) during the winter. Therefore, there is a need to assess the threshold at which seaweed-derived polymers may have positive effects or negative impacts on human nutrition. Furthermore, this study highlights the three polymers, along with their known thresholds, at which they can have positive and/or negative health impacts. Such knowledge is key to recognizing the paradigm governing their successful deployment and related beneficial applications in humans.

Purification and Biological Activities of Enzymatically Degraded Sargassum fusiforme Polysaccharides

Enzymatic hydrolysate of the crude polysaccharide (SFP) extracted from Sargassum fusiforme was purified by column DEAE-52 and Sephadex G-100 to yield four components, namely, ESFP1, ESFP2, ESFP3 and ESFP4. These components were characterized by chemical composition assay, GC/MS, HPGPC, UV and FT-IR techniques. The in vitro antioxidant activities of the four purified fractions were investigated by measuring their radical scavenging activity and reducing power. The results suggested that all the four components possess good antioxidant activities. Among them, ESFP1 was found to possess the strongest 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and hydroxyl radical-scavenging activity, and the greatest ferric reducing power. The immunomodulatory effect of these four polysaccharides was demonstrated by their ability to promote proliferation, and to enhance both phagocytic activity and NO release in a macrophage RAW264.7 model. The results revealed that the bioactivities of the polysaccharides are related to their molecular weight, and the uronic acid and sulfate contents.

Purification, structural characterization, and biological activities of degraded polysaccharides from Porphyra yezoensis

The degraded polysaccharides from Porphyra yezoensis (DPPY) prepared using the H₂ O₂ -Vc method under optimized conditions were isolated and purified by DEAE Cellulose-52, and Sephadex G-100, providing four pure components, namely, DPPY-0, DPPY-0.1, DPPY-0.3, and DPPY-0.5. Their relative molecular weights were measured to be 10.8, 10.7, 18.7, and 35.5 kDa, respectively. GC-MS analysis revealed that all the four fractions were mainly composed of galactose, together with a small portion of glucose, mannose, xylose, and rhamnose. Structural analysis revealed that the purified polysaccharides mainly possess a backbone of (1 → 3)-β-D-galactose (1 → 4)-3,6-anhydro-α-L-galactopyranose (G-A) units and (1 → 3)-β-D-galactose (1 → 4)-α-L-galactose-6-sulfate (G-L6S) units. They were found to promote the proliferation of RAW264.7 macrophages and enhance phagocytosis of the RAW264.7 cells. Antioxidant assays indicated that DPPY-0.5 possessed the most potent reducing power and free radical scavenging ability among the four purified polysaccharides. High sulfate content and proper molecular weight of these fractions are favorable to their immunomodulatory and antioxidant activities. PRACTICAL APPLICATIONS: Porphyra yezoensis, common economic red algae widely distributed in East Asian countries, contains a high content of polysaccharides with a variety of biological activities. However, P. yezoensis polysaccharide (PPY) has not been well utilized due to the relatively low biological activities and lack of understanding of its structure-activity relationship. Thus, it is necessary to improve the bioactivities and elucidate the structure-activity relationship of this polysaccharide for its practical use. In the present work, four purified fractions (DPPY-0, DPPY-0.1, DPPY-0.3, and DPPY-0.5) were isolated from the degraded P. yezoensis polysaccharide, and were investigated for their antioxidant and immunoregulatory activities. The results of the present work will lay a foundation for the application of the degraded P. yezoensis polysaccharide in the food industry as a functional food ingredient.

Porphyran and oligo-porphyran originating from red algae Porphyra: Preparation, biological activities, and potential applications

Porphyra is one of the most economically important red algae in the world. The functional components extracted from Porphyra such as porphyrans, proteins, lipids, and minerals have strong physiological activities. Porphyran, a sulfated galactan, is composed of alternating 1,4-linked α-l-galactopyranose-6-sulfate (L6S) and 1,3-linked β-d-galactopyranose (G). Porphyran and oligo-porphyran have a series of pharmacological and biological functions, such as antioxidation, anticancer, antiaging, antiallergic, immunomodulatory, hypoglycaemic, and hypolipidemic effects. Thus, red algae Porphyra-derived porphyran and oligo-porphyran have various potential applications in food, medicine, and cosmetic fields. For better application, this review introduces and summarizes the structure and source of porphyran as well as the preparation methods, biological activities, and potential applications of porphyran and oligo-porphyran. Moreover, the future research directions and emphasis of porphyran and oligo-porphyran preparation as well as their functional activities and applications are highlighted and prospected.

Increased antioxidant activity and improved structural characterization of sulfuric acid-treated stepwise degraded polysaccharides from Pholiota nameko PN-01

The aim of this study was to investigate sulfuric acid degradation of the Pholiota nameko polysaccharide (AIPS-1). Three stepwise degraded polysaccharides (AIPS-2, AIPS-3, and AIPS-4) were obtained by sequentially increasing the strength of sulfuric acid treatment. Structural characterization showed that sulfuric acid treatment significantly decreased molecular weight, increased the content of uronic acid and changed the molar ratio of monosaccharide composition, while the major functional groups and the triple helical conformation of polysaccharides did not change significantly. In vitro experiments proved that the antioxidation ability of the stepwise degraded polysaccharides gradually increased (AIPS-1 < AIPS-2 < AIPS-3 < AIPS-4). An oxidative stress zebrafish model was established, which demonstrated that the ability of AIPS-3 and AIPS-4 to scavenge free radicals in zebrafish was significantly improved compared to AIPS-1. In conclusion, sulfuric acid treatment is an effective method for improving the antioxidant activity of polysaccharides, and increased antioxidant activity was closely related to the changes in their structural characteristics.