Opportunities and challenges of algal fucoidan for diabetes management

Algal Active Ingredients and Their Involvement in Managing Diabetic Mellitus

Diabetes mellitus (DM) is becoming increasingly prominent, posing a serious threat to human health. Its prevalence is rising every year, and often affects young people. In the past few decades, research on marine algae has been recognized as a major field of drug discovery. Seaweed active substances, including algal polysaccharides, algal polyphenols, algal unsaturated fatty acids, and algal dietary fiber, have unique biological activities. This article reviews the effects and mechanisms of the types, structures, and compositions of seaweed on inhibiting glucose and lipid metabolism disorders, with a focus on the inhibitory effect of active substances on blood glucose reduction. The aim is to provide a basis for the development of seaweed active substance hypoglycemic drugs.

Systematic Characteristics of Fucoidan: Intriguing Features for New Pharmacological Interventions

Fucoidan, a sulfated polysaccharide found primarily in brown algae, is known for exhibiting various biological activities, many of which have been attributed to its sulfate content. However, recent advancements in techniques for analyzing polysaccharide structures have highlighted that not only the sulfate groups but also the composition, molecular weight, and structures of the polysaccharides and their monomers play a crucial role in modulating biological effects. This review comprehensively provides the monosaccharide composition, degree of sulfation, molecular weight distribution, and linkage of glycosidic bonds of fucoidan, focusing on the diversity of its biological activities based on various characteristics. The implications of these findings for future applications and potential therapeutic uses of fucoidan are also discussed.

Algae-derived compounds: Bioactivity, allergenicity and technologies enhancing their values

As a rapidly growing source of human nutrients, algae biosynthesize diverse metabolites which have promising bioactivities. However, the potential allergenicity of algal components hinder their widespread adoption. This review provides a comprehensive review of various macro and micronutrients derived from algal biomass, with particular focus on bioactive compounds, including peptides, polyphenols, carotenoids, omega-3 fatty acids and phycocyanins. The approaches used to produce algal bioactive compounds and their health benefits (antioxidant, antidiabetic, cardioprotective, anti-inflammatory and immunomodulatory) are summarised. This review particularly focuses on the state-of-the-art of precision fermentation, encapsulation, cold plasma, high-pressure processing, pulsed electric field, and subcritical water to reduce the allergenicity of algal compounds while increasing their bioactivity and bioavailability. By providing insights into current challenges of algae-derived compounds and opportunities for advancement, this review contributes to the ongoing discourse on maximizing their application potential in the food nutraceuticals, and pharmaceuticals industries.

Advances in the treatment of type 2 diabetes mellitus by natural plant polysaccharides through regulation of gut microbiota and metabolism: A review

The prevalence and impact of type 2 diabetes mellitus (T2DM) is a major global health problem. The treatment process of T2DM is long and difficult to cure. Therefore, it is necessary to explore alternative or complementary methods to deal with the various challenges brought by T2DM. Natural plant polysaccharides (NPPs) have certain potential in the treatment of T2DM. However, many studies have not considered the relationship between the structure of NPPs and their anti-T2DM activity. This paper reviews the relevant anti-T2DM mechanisms of NPPs, including modulation of insulin action, promotion of glucose metabolism and modulation of postprandial glucose levels, anti-inflammation and modulation of gut microbiota (GM) and metabolism. This paper provides an in-depth study of the conformational relationships of NPPs and facilitates the development of anti-T2DM drugs or dietary supplements with NPPs.

Fucoidan from the cell wall of Silvetia siliquosa with immunomodulatory effect on RAW 264.7 cells

Silvetia siliquosa, the only species of the family Fucaceae in China, is used as a medicine food homology. Fucoidan from S. siliquosa was extracted by hot water twice thoroughly (13 % of total yield), and a purified fucoidan SSF with a molecular weight of 93 kD was obtained. Chemical composition analysis demonstrated that SSF was primarily composed of sulfate (21.68 wt%) and fucose (84 % of all neutral monosaccharides). IR, methylation analysis, NMR and ESI-MS results indicated SSF had the backbone of mainly (1 → 3)-α-L-fucopyranose and minor (1 → 4)-α-L-fucopyranose, with little 1,3 and 1,4 branched β-D-Xylp and β-D-Galp. The in vitro immunomodulatory test on RAW 264.7 cells showed that SSF could up-regulate the expression of immune related factors and proteins in a concentration-dependent manner, but the immunomodulatory effect disappeared from desulfated SSF. This research indicated that highly sulfated fucan possessed immunomodulatory effect and the importance of sulfate groups in the activity of SSF.

Marine Compounds and Age-Related Diseases: The Path from Pre-Clinical Research to Approved Drugs for the Treatment of Cardiovascular Diseases and Diabetes

Ageing represents a main risk factor for several pathologies. Among them, cardiovascular diseases (CVD) and type 2 diabetes mellitus (T2DM) are predominant in the elderly population and often require prolonged use of multiple drugs due to their chronic nature and the high proportion of co-morbidities. Hence, research is constantly looking for novel, effective molecules to treat CVD and T2DM with minimal side effects. Marine active compounds, holding a great diversity of chemical structures and biological properties, represent interesting therapeutic candidates to treat these age-related diseases. This review summarizes the current state of research on marine compounds for the treatment of CVD and T2DM, from pre-clinical studies to clinical investigations and approved drugs, highlighting the potential of marine compounds in the development of new therapies, together with the limitations in translating pre-clinical results into human application.

An Update on the Chemical Constituents and Biological Properties of Selected Species of an Underpinned Genus of Red Algae: Chondrus

Macroalgae, particularly red seaweeds, have attracted significant attention due to their economic and health benefits. Chondrus, a red algae genus, despite its economic importance, seems to be undervalued. Among all its species, Chondrus crispus has been meticulously documented for its biological properties, and little is known about other species. No comprehensive review of the biological properties of this genus has been acknowledged. Thus, this review aimed to summarize the available information on the chemical constituents and biological properties of a few selected species, including Chondrus crispus, Chondrus ocellatus, Mazzaella canaliculata, and Chondrus armatus. We compiled and discovered that the genus is offering most of the important health-promoting benefits evidenced from in vitro and in vivo studies focused on antimicrobial, immunomodulation, neuroprotection, anti-atopic, anti-inflammatory, anti-viral, anti-diabetic, cytoprotective, antioxidant, anti-coagulation, nephroprotective, anti-tumor, and anti-venom activity, which speaks about the potential of this genus. Data on clinical studies are limited. Further, around 105 chemical constituents have been reported from Chondrus spp. Given its significance, further investigation is warranted, in the form of meticulously planned cell, animal, and clinical studies that concentrate on novel health-enhancing endeavors, in order to unveil the full potential of this genus. The review also outlines challenges and future directions.

Algae in Biomedicine

Algae, which live in marine or freshwater, are photosynthetic organisms. They vary greatly in size, morphology, and degree of complexity of their body structures. Algae are generally divided into two main groups, microalgae, which are small in size, and macroalgae, which are larger in size. These aquatic organisms have rich and valuable compounds including sterols, polysaccharides, pigments, fatty acids, proteins, enzymes, minerals, and vitamins that could be used in different application fields due to their bioactive functions. In recent years, algae and their components have attracted interest in biomedicine and health applications as their bioactive components could show antioxidant, anticancer, anti-inflammatory, antiviral, antiangiogenic, antidiabetic, antiobesity, immunostimulatory, vaccine adjuvant, and hypolipidemic activities. In this chapter, these activities and bioactive components underlying these properties are reviewed.

Primary structural features, physicochemical and biological properties of two water-soluble polysaccharides extracted from the brown Tunisian seaweed Halopteris scoparia

Marine algae are the most abundant resource in the marine environment and are still a promising source of bioactive compounds including hydrocolloids. This study contributes to the evaluation of the biological and biotechnological potentials of two water soluble polysaccharides, namely alginates (AHS) and fucoidan (FHS), extracted and purified from Halopteris scoparia, an abundant Tunisian brown macroalgae collected in Tunisia (Tabarka region). The total sugars, neutral monosaccharides, uronic acids, proteins, polyphenols, and sulfate groups contents were quantified for both fractions, as well as their functional groups and primary structural features by Fourier transform infrared spectroscopy, ionic and/or gas chromatography and nuclear magnetic resonance analyses. AHS and FHS showed significant anti-inflammatory (IC50 ≈ 1 mg/mL), anticoagulant (e.g., 27-61.7 for the activated partial thromboplastin time), antihyperglycemic (0.1-40 μg/mL) and anti-trypsin (IC50 ≈ 0.3-0.4 mg/mL) effects. FHS and a hydrolyzed fraction showed a very promising potential against herpes viruses (HSV-1) (IC50 < 28 μg/mL). Besides, AHS and two hydrolyzed fractions were able to stimulate the natural defenses of tomato seedlings, assessing their elicitor capacity, by increasing the activity of phenylalanine ammonia-lyase (66-422 %) but also significantly changing the polyphenol content in the leaves (121-243 %) and roots (30-104 %) of tomato plants.

A review on the hypoglycemic effect, mechanism and application development of natural dietary polysaccharides

Diabetes mellitus (DM) as one chronic metabolic disease was greatly increased over recent decades. The major agents treating diabetes have noticeable side effects as well as the tolerability problems. The bioactive dietary polysaccharides from abundant natural resources exhibit good hypoglycemic effect with rare adverse effects, which might serve as a candidate to prevent and treat diabetes. However, the correlations between the hypoglycemic mechanism of polysaccharides and their structure were not mentioned in several studies, what's more, most of the current hypoglycemic studies on polysaccharides were based on in vitro and in vivo experiments, and there was a lack of knowledge about the effects in human clinical trials. The aim of this review is to discuss recent literature about the variety of dietary polysaccharides with hypoglycemic activity, as well the mechanism of action and the structure-function relationship are highlighted. Meanwhile, the application of dietary polysaccharides in functional foods and clinical medicine are realized with an in-depth understanding. So as to promote the exploration of dietary polysaccharides in low glycemic healthy foods or clinical medicine to prevent and treat diabetes.

Marine algal polysaccharides as future potential constituents against non-alcoholic steatohepatitis

Non-alcoholic steatohepatitis (NASH) is one of the most chronic and incurable liver diseases triggered mainly by an inappropriate diet and hereditary factors which burden liver metabolic stress, and may result in liver fibrosis or even cancer. While the available drugs show adverse side effects. The non-toxic bioactive molecules derived from natural resources, particularly marine algal polysaccharides (MAPs), present significant potential for treating NASH. In this review, we summarized the protective effects of MAPs on NASH from multiple perspectives, including reducing oxidative stress, regulating lipid metabolism, enhancing immune function, preventing fibrosis, and providing cell protection. Furthermore, the mechanisms of MAPs in treating NASH were comprehensively described. Additionally, we highlight the influences of the special structures of MAPs on their bioactive differences. Through this comprehensive review, we aim to further elucidate the molecular mechanisms of MAPs in NASH and inspire insights for deeper research on the functional food and clinical applications of MAPs.

Fucus vesiculosus polysaccharide alleviates type 2 diabetes in rats via remodeling gut microbiota and regulating glycolipid metabolism-related gene expression

The antidiabetic activity and underlying mechanisms of Fucus vesiculosus polysaccharide (FVP) were studied in type 2 diabetic rats. Our results exhibited that FVP intervention reversed body weight loss, alleviated hyperglycemia and insulin resistance in diabetic rats. FVP also had the potential to ameliorate dyslipidemia, liver and kidney dysfunction, decrease oxidative stress, promote glycogen synthesis, and boost short-chain fatty acid production and total bile acid excretion. 16S rRNA gene sequencing analysis suggested that FVP interfered with the gut microbiota in a beneficial manner. Moreover, RT-qPCR results demonstrated that the antidiabetic activity of FVP in connection with the acceleration of blood glucose absorption and glycogen synthesis, the inhibition of gluconeogenesis, and the regulation of lipid metabolism in the liver. These findings suggested that FVP had antidiabetic effects on high-fat diet and STZ-induced diabetic rats and could be a potential resource for treating type 2 diabetes mellitus.

Potential Application of Marine Fucosyl-Polysaccharides in Regulating Blood Glucose and Hyperglycemic Complications

Diabetes mellitus (DM) has become the world's third major disease after tumors and cardiovascular disease. With the exploitation of marine biological resources, the efficacy of using polysaccharides isolated from marine organisms in blood glucose regulation has received widespread attention. Some marine polysaccharides can reduce blood glucose by inhibiting digestive enzyme activity, eliminating insulin resistance, and regulating gut microbiota. These polysaccharides are mainly fucose-containing sulphated polysaccharides from algae and sea cucumbers. It follows that the hypoglycemic activity of marine fucosyl-polysaccharides is closely related to their structure, such as their sulfate group, monosaccharide composition, molecular weight and glycosidic bond type. However, the structure of marine fucosyl-polysaccharides and the mechanism of their hypoglycemic activity are not yet clear. Therefore, this review comprehensively covers the effects of marine fucosyl-polysaccharides sources, mechanisms and the structure-activity relationship on hypoglycemic activity. Moreover, the potential regulatory effects of fucosyl-polysaccharides on vascular complications caused by hyperglycemia are also summarized in this review. This review provides rationales for the activity study of marine fucosyl-polysaccharides and new insights into the high-value utilization of marine biological resources.

Purification and Characterization of the Enzyme Fucoidanase from Cobetia amphilecti Utilizing Fucoidan from Undaria pinnatifida

Fucoidanase is an unstable enzyme with high specificity that requires a large about of time to screen it from microorganisms. In this study, enzymatic hydrolysis was used to produce low-molecular-weight fucoidan from microorganisms via the degradation of high-molecular-weight fucoidan without damage to the sulfate esterification structure of oligosaccharide. The microbial strain HN-25 was isolated from sea mud and was made to undergo mutagenicity under ultraviolet light. Fucoidanase was extracted via ultrasonication and its enzymatic activity was improved via optimization of the ultrasonic conditions. The enzymatic properties and degradation efficiency of fucoidanase were characterized. The microbial strain HN-25 is a Gram-negative aerobic and rod-shaped-cell bacterium, and therefore was identified as Cobetia amphilecti via 16s rDNA. The results proved that fucoidanase is a hydrolytic enzyme with a molecular weight of 35 kDa and with high activity and stability at 30 °C and pH 8.0. The activity of fucoidanase was significantly enhanced by sodium and calcium ions and inhibited by a copper ion and ethylenediaminetetraacetate (EDTA). There was a significant decrease in the molecular weight of fucoidan after enzymatic hydrolysis. The low-molecular-weight fuicodan was divided into four fractions, mainly concentrated at F3 (20~10 kDa) and F4 (≤6 kDa). These consequences suggest that fucoidanase obtained from Cobetia amphilecti is stable and efficient and could be a good tool in the production of bioactive compounds.

A versatile modification strategy for functional non-glutaraldehyde cross-linked bioprosthetic heart valves with enhanced anticoagulant, anticalcification and endothelialization properties

Valvular heart disease is a major threat to human health and transcatheter heart valve replacement (THVR) has emerged as the primary treatment option for severe heart valve disease. Bioprosthetic heart valves (BHVs) with superior hemodynamic performance and compressibility have become the first choice for THVR, and more BHVs have been requested for clinical use in recent years. However, several drawbacks remain for the commercial BHVs cross-linked by glutaraldehyde, including calcification, thrombin, poor biocompatibility and difficulty in endothelialization, which would further reduce the BHVs' lifetime. This study developed a dual-functional non-glutaraldehyde crosslinking reagent OX-VI, which can provide BHV materials with reactive double bonds (CC) for further bio-function modification in addition to the crosslinking function. BHV material PBAF@OX-PP was developed from OX-VI treated porcine pericardium (PP) after the polymerization with 4-vinylbenzene boronic acid and the subsequent modification of poly (vinyl alcohol) and fucoidan. Based on the functional anti-coagulation and endothelialization strategy and dual-functional crosslinking reagent, PBAF@OX-PP has better anti-coagulation and anti-calcification properties, higher biocompatibility, and improved endothelial cells proliferation when compared to Glut-treated PP, as well as the satisfactory mechanical properties and enhanced resistance effect to enzymatic degradation, making it a promising candidate in the clinical application of BHVs. STATEMENT OF SIGNIFICANCE: Transcatheter heart valve replacement (THVR) has become the main solution for severe valvular heart disease. However, bioprosthetic heart valves (BHVs) used in THVR exhibit fatal drawbacks such as calcification, thrombin and difficulty for endothelialization, which are due to the glutaraldehyde crosslinking, resulting in a limited lifetime to 10-15 years. A new non-glutaraldehyde cross-linker OX-VI has been designed, which can not only show great crosslinking ability but also offer the BHVs with reactive double bonds (CC) for further bio-function modification. Based on the dual-functional crosslinking reagent OX-VI, a versatile modification strategy was developed and the BHV material (PBAF@OX-PP) has been developed and shows significantly enhanced anticoagulant, anti-calcification and endothelialization properties, making it a promising candidate in the clinical application of BHVs.

The therapeutic potential for senescence-associated diabetes of green alga Enteromorpha prolifera polysaccharide

DEAE-52 and Sephadex G-100 columns were used to isolate Enteromorpha prolifera polysaccharide (EPP), which contains α-L-Rhap-(1 → 4)-α-L-Arap-(1 → 2)-α-L-Rhap-(1 → 3)-β-D-Galp-(1 → structural fragment, along with α-L-Rhap-(1 → and →2)-α-L-Rhap-(1 → 3)-β-D-GlcpA-(1 → side bonds that connect to →3,6)-β-D-Galp-(1→. The anti-ageing and hypoglycemic activities of EPP were assessed using an ageing diabetic mice model, and the revealed that EPP could improve glucose metabolism-associated parameters and inhibit the expression of ageing associated genes, including p16^INK4a, p38 MAPK, NOX-1, VEGF, and AGER, thus preventing liver damage. Moreover, gut microbiota profiling revealed that EPP significantly increased the abundances of o_Lactobacillaceae, c_Bacilli, f_Lactobacillaceae, g_Lactobacillus, and p_Firmicutes, showing that EPP has a probiotic effect on enhancing the beneficial microbiota in ageing diabetic mice. In summary, EPP might serve as a potential bioactive compound to alleviate hyperglycaemia and ageing in diabetic in mice and further clinical studies are required to verify these effects.

Biopharmaceutical applications of microbial polysaccharides as materials: A review

Biological characteristics of natural polymers make microbial polysaccharides an excellent choice for biopharmaceuticals. Due to its easy purifying procedure and high production efficiency, it is capable of resolving the existing application issues associated with some plant and animal polysaccharides. Furthermore, microbial polysaccharides are recognized as prospective substitutes for these polysaccharides based on the search for eco-friendly chemicals. In this review, the microstructure and properties of microbial polysaccharides are utilized to highlight their characteristics and potential medical applications. From the standpoint of pathogenic processes, in-depth explanations are provided on the effects of microbial polysaccharides as active ingredients in the treatment of human diseases, anti-aging, and drug delivery. In addition, the scholarly developments and commercial applications of microbial polysaccharides as medical raw materials are also discussed. The conclusion is that understanding the use of microbial polysaccharides in biopharmaceuticals is essential for the future development of pharmacology and therapeutic medicine.

Development and characterization of a fucoidan-based nanoemulsion using Nigella sativa oil for improvement of anti-obesity activity of fucoxanthin in an obese rat model

The anti-obesity activity of encapsulated fucoxanthin in fucoidan-based nanoemulsion was investigated. Then, high-fat diet (HFD) induced-obese rats were fed along with different treatments including administration of encapsulated fucoxanthin (10 mg/kg and 50 mg/kg/day), fucoidan (70 mg/kg), Nigella sativa oil (250 mg/kg), metformin (200 mg/kg), and free form of fucoxanthin (50 mg/kg) by oral gavage daily for 7 weeks. The study discovered that fucoidan-based nanoemulsions with a low and high dose of fucoxanthin had droplet size in the range of 181.70-184.87 nm and encapsulation efficacy of 89.94-91.68 %, respectively. Also exhibited 75.86 % and 83.76 % fucoxanthin in vitro release. The TEM images and FTIR spectera confirmed the particle size and encapsulation of fucoxanthin, respectively. Moreover, in vivo results revealed that encapsulated fucoxanthin reduced body and liver weight compared with a HFD group (p < 0.05). Biochemical parameters (FBS, TG, TC, HDL, LDL) and liver enzymes (ALP, AST, and ALT) were decreased after fucoxanthin and fucoidan administration. According to the histopathological analysis, fucoxanthin and fucoidan attenuated lipid accumulation in the liver.

Nano-Sized Fucoidan Interpolyelectrolyte Complexes: Recent Advances in Design and Prospects for Biomedical Applications

The marine polysaccharide fucoidan (FUC) is a promising polymer for pharmaceutical research and development of novel drug delivery systems with modified release and targeted delivery. The presence of a sulfate group in the polysaccharide makes FUC an excellent candidate for the formation of interpolyelectrolyte complexes (PECs) with various polycations. However, due to the structural diversity of FUC, the design of FUC-based nanoformulations is challenging. This review describes the main strategies for the use of FUC-based PECs to develop drug delivery systems with improved biopharmaceutical properties, including nanocarriers in the form of FUC-chitosan PECs for pH-sensitive oral delivery, targeted delivery systems, and polymeric nanoparticles for improved hydrophobic drug delivery (e.g., FUC-zein PECs, core-shell structures obtained by the layer-by-layer self-assembly method, and self-assembled hydrophobically modified FUC particles). The importance of a complex study of the FUC structure, and the formation process of PECs based on it for obtaining reproducible polymeric nanoformulations with the desired properties, is also discussed.

A Review of the Effects of Puerarin on Glucose and Lipid Metabolism in Metabolic Syndrome: Mechanisms and Opportunities

Chronic diseases, including metabolic syndrome related to sugar and lipid metabolic disorders, are the leading causes of premature death around the world. Novel treatment strategies without undesirable effects are urgently needed. As a natural functional ingredient, puerarin is a promising alternative for the treatment of sugar and lipid metabolic disorders. However, the applications of puerarin are limited due to its poor solubility and short half-life. Various drug delivery systems have been investigated to improve the bioavailability of puerarin. This review summarizes the mechanisms involved in the beneficial action of puerarin: suppressing the release of glucose and FFA; regulating the transport of glucose and fatty acids; acting on the PI3K-Akt and AMPK signaling pathways to decrease the synthesis of glucose and fatty acids; acting on the PPAR signaling pathway to promote β-oxidation; and improving insulin secretion and sensitivity. In addition, the preparation technologies used to improve the bioavailability of puerarin are also summarized in this review, in the hope of helping to promote the application of puerarin.

Sanghuangporus vaninii fruit body polysaccharide alleviates hyperglycemia and hyperlipidemia via modulating intestinal microflora in type 2 diabetic mice

The disease of type 2 diabetes mellitus (T2DM) is principally induced by insufficient insulin secretion and insulin resistance. In the current study, Sanghuangporus vaninii fruit body polysaccharide (SVP) was prepared and structurally characterized. It was shown that the yield of SVP was 1.91%, and SVP mainly contains small molecular weight polysaccharides. Afterward, the hypoglycemic and hypolipidemic effects and the potential mechanism of SVP in T2DM mice were investigated. The results exhibited oral SVP could reverse the body weight loss, high levels of blood glucose, insulin resistance, hyperlipidemia, and inflammation in T2DM mice. Oral SVP increased fecal short-chain fatty acids (SCFAs) concentrations of T2DM mice. Additionally, 16S rRNA sequencing analysis illustrated that SVP can modulate the structure and function of intestinal microflora in T2DM mice, indicating as decreasing the levels of Firmicutes/Bacteroidetes, Flavonifractor, Odoribacter, and increasing the levels of Weissella, Alloprevotella, and Dubosiella. Additionally, the levels of predicted metabolic functions of Citrate cycle, GABAergic synapse, Insulin signaling pathway were increased, and those of Purine metabolism, Taurine and hypotaurine metabolism, and Starch and sucrose metabolism were decreased in intestinal microflora after SVP treatment. These findings demonstrate that SVP could potentially play hypoglycemic and hypolipidemic effects by regulating gut microflora and be a promising nutraceutical for ameliorating T2DM.

Inhibitory Potential of Six Brown Algae from the Persian Gulf on α-Glucosidase and In Vivo Antidiabetic Effect of Sirophysalis Trinodis

Background

Brown algae have gained worldwide attention due to their significant biological activities, such as antidiabetic properties. In the present study, the antidiabetic properties of six brown algae from the Persian Gulf were investigated.

Methods

An experimental study was conducted from 2017 to 2019 to examine the inhibitory effects of six brown algae against the α-glucosidase activity. Methanol (MeOH) and 80% MeOH extracts of Colpomenia sinuosa, Sargassum acinaciforme, Iyengaria stellata, Sirophysalis trinodis, and two accessions of Polycladia myrica were analyzed. The effect of 80% MeOH extracts of Sirophysalis trinodis on blood glucose levels in streptozotocin-induced diabetic rats was evaluated. Chemical constituents of brown algae were analyzed using thin-layer chromatography and liquid chromatography-mass spectrometry techniques. Data were analyzed using SPSS software, and P<0.05 was considered statistically significant.

Results

The 80% MeOH extracts of Iyengaria stellata (IC50=0.33±0.15 μg/mL) and Colpomenia sinuosa (IC50=3.50±0.75 μg/mL) as well as the MeOH extracts of Colpomenia sinuosa (IC50=3.31±0.44 μg/mL) exhibited stronger inhibitory effect on α-glucosidase than the acarbose (IC50=160.15±27.52 μg/mL, P<0.001). The 80% MeOH extracts of Sirophysalis trinodis reduced postprandial blood glucose levels in diabetic rats compared to the control group (P=0.037). Fucoxanthin was characterized as the major antidiabetic agent in most of the algal extracts.

Conclusion

Sirophysalis trinodis is recommended as a novel source for isolation and identification of potential antidiabetic compounds due to its high in vivo and in vitro antidiabetic effects.

Therapeutic potential of non-starch polysaccharides on type 2 diabetes: from hypoglycemic mechanism to clinical trials

Non-starch polysaccharides (NSPs) have been reported to exert therapeutic potential on managing type 2 diabetes mellitus (T2DM). Various mechanisms have been proposed; however, several studies have not considered the correlations between the anti-T2DM activity of NSPs and their molecular structure. Moreover, the current understanding of the role of NSPs in T2DM treatment is mainly based on in vitro and in vivo data, and more human clinical trials are required to verify the actual efficacy in treating T2DM. The related anti-T2DM mechanisms of NSPs, including regulating insulin action, promoting glucose metabolism and regulating postprandial blood glucose level, anti-inflammatory and regulating gut microbiota (GM), are reviewed. The structure-function relationships are summarized, and the relationships between NSPs structure and anti-T2DM activity from clinical trials are highlighted. The development of anti-T2DM medication or dietary supplements of NSPs could be promoted with an in-depth understanding of the multiple regulatory effects in the treatment/intervention of T2DM.

Expression and Biochemical Characterization of a Novel Fucoidanase from Flavobacteriumalgicola with the Principal Product of Fucoidan-Derived Disaccharide

Fucoidan is one of the main polysaccharides of brown algae and echinoderm, which has nutritional and pharmacological functions. Due to the low molecular weight and exposure of more sulfate groups, oligo-fucoidan or fucoidan oligosaccharides have potential for broader applications. In this research, a novel endo-α-1,4-L-fucoidanase OUC-FaFcn1 which can degrade fucoidan into oligo-fucoidan was discovered from the fucoidan-digesting strain Flavobacterium algicola 12,076. OUC-FaFcn1 belongs to glycoside hydrolases (GH) family 107 and shows highest activity at 40 °C and pH 9.0. It can degrade the α-1,4 glycosidic bond, instead of α-1,3 glycosidic bond, of the fucoidan with a random tangent way to generate the principal product of disaccharide, which accounts for 49.4% of the total products. Therefore, OUC-FaFcn1 is a promising bio-catalyst for the preparation of fucoidan-derived disaccharide. These results further enrich the resource library of fucoidanase and provide the basis for the directional preparation of fucoidan-derived oligosaccharide with specific polymerization.

Purification, Chemical Characterization and Immunomodulatory Activity of a Sulfated Polysaccharide from Marine Brown Algae Durvillaea antarctica

An immunomodulatory polysaccharide (DAP4) was extracted, purified, and characterized from Durvillaea antarctica. The results of chemical and spectroscopic analyses demonstrated that the polysaccharide was a fucoidan, and was mainly composed of (1→3)-α-l-Fucp and (1→4)-α-l-Fucp residues with a small degree of branching at C-3 of (1→4)-α-l-Fucp residues. Sulfate groups were at C-4 of (1→3)-α-l-Fucp, C-2 of (1→4)-α-l-Fucp and minor C-6 of (1→4)-β-d-Galp. Small amounts of xylose and galactose exist in the forms of β-d-Xylp-(1→ and β-d-Gal-(1→. The immunomodulatory activity of DAP4 was measured on RAW 264.7 cells, the results proved that DAP4 exhibited excellent immunomodulatory activities, such as promoted the proliferation of spleen lymphocytes, increased NO production, as well as enhanced phagocytic of macrophages. Besides, DAP4 could also produce better enhancement on the vitality of NK cells. For the high immunomodulatory activity, DAP4 might be a potential source of immunomodulatory fucoidan with a novel structure.

Elucidation of the interaction effect between dietary fiber and bound polyphenol components on the anti-hyperglycemic activity of tea residue dietary fiber

Dietary fiber intake is beneficial for the prevention of some chronic metabolic diseases. Considering the characteristic that dietary fiber from tea residues (TRDF) is rich in bound polyphenols, the study aimed to elucidate the interaction effect between dietary fiber components (TRDF-DF) and bound polyphenol components (TRDF-BP) on the anti-hyperglycemic activity of TRDF. A type 2 diabetes (T2D) rat model induced by high-fat diet and streptozotocin injection was applied in this study. The results showed that bound polyphenol components rather than dietary fiber components were essential for the anti-hyperglycemic activity of TRDF, as evidenced by remarkable differences in fasting blood glucose (FBG), the insulin resistance index (HOMA-IR) and the levels of serum oxidative stress between the TRDF and TRDF-DF groups, as well as the up-regulation of the expression of insulin signaling pathway-related proteins in the liver after TRDF and TRDF-BP administration. In addition, the synergistic effect between TRDF-BP and TRDF-DF components modulated gut microbiota dysbiosis and increased the content of short chain fatty acids (SCFAs) via enriching beneficial bacteria and inhibiting harmful bacteria. The role of TRDF-BP and TRDF-DF as well as their interaction effect on the anti-hyperglycemic activity of TRDF are elucidated, which can provide theoretical basis for TRDF as a dietary supplement to manage T2D.

Nutraceutical potentials of algal ulvan for healthy aging

Several theories for aging are constantly put forth to explain the underlying mechanisms. Oxidative stress, DNA dysfunction, inflammation, and mitochondrial dysfunction, along with the release of cytochrome c are some of these theories. Diseases such as type 2 diabetes mellitus, intestinal dysfunction, cardiovascular diseases, hepatic injury, and even cancer develop with age and eventually cause death. Ulva polysaccharides, owing to their special structures and various functions, have emerged as desirable materials for keeping healthy. These polysaccharide structures are found to be closely related to the extraction methods, seaweed strains, and culture conditions. Ulvan is a promising bioactive substance, a potential functional food, which can regulate immune cells to augment inflammation, control the activity of aging-related genes, promote tumor senescence, enhance mitochondrial function, maintain liver balance, and protect the gut microbiome from inflammatory attacks. Given the desirable physiochemical and gelling properties of ulvan, it would serve to improve the quality and shelf-life of food.