Antioxidant activity and hepatoprotective potential of agaro-oligosaccharides in vitro and in vivo

Agaro-oligosaccharides mitigate deoxynivalenol-induced intestinal inflammation by regulating gut microbiota and enhancing intestinal barrier function in mice

Agarose-derived agaro-oligosaccharides (AgaroS) have been extensively studied in terms of structures and bioactivities; they reportedly possess antioxidant and anti-inflammatory activities that maintain intestinal homeostasis and host health. However, the protective effects of AgaroS on deoxynivalenol (DON)-induced intestinal dysfunction remain unclear. We investigated the effects of AgaroS on DON-induced intestinal dysfunction in mice and explored the underlying protective mechanisms. In total, 32 mice were randomly allocated to four treatments (n = 8 each) for 28 days. From day 1 to day 21, the control (CON) and DON groups received oral phosphate-buffered saline (200 μL per day); the AgaroS and AgaroS + DON groups received 200 mg AgaroS per kg body weight once daily by orogastric gavage. Experimental intestinal injury was induced by adding DON (4.8 mg per kg body weight) via gavage from day 21 to day 28. Phosphate-buffered saline was administered once daily by gavage in the CON and AgaroS groups. Herein, AgaroS supplementation led to a higher final body weight and smaller body weight loss and a lower concentration of plasma inflammatory cytokines, compared with the DON group. The DON group showed a significantly reduced ileal villus height and villus height/crypt depth, compared with the CON and AgaroS + DON groups. However, AgaroS supplementation improved DON-induced intestinal injury in mice. Compared with the DON group, ileal and colonic protein expression levels of claudin, occludin, Ki67, and mucin2 were significantly higher in the AgaroS supplementation group. Colonic levels of the anti-inflammatory cytokine IL-1β tended to be higher in the DON group than in the AgaroS + DON group. AgaroS altered the gut microbiota composition, accompanied by increased production of short-chain fatty acids in mice. In conclusion, our findings highlight a promising anti-mycotoxin approach whereby AgaroS alleviate DON-induced intestinal inflammation by modulating intestinal barrier functional integrity and gut microbiota in mice.

Biochemical characterization and key catalytic residue identification of a novel alpha-agarase with CBM2 domain

Agarooligosaccharides have great potential in food industry because of their various bio-activities, while the limited availability and diversity of α-agarases hinder agarooligosaccharides' broader application. To overcome this limitation, a computer-assisted method was used to screen and identify novel agarases. Firstly, one novel α-agarase, AgaB, with an N-terminal CBM2 domain (the first report of this domain in agarases), was discovered. Purified agarases only exhibited activity against agarose, with optimum activity at 40℃ and pH 8.0. Analysis of hydrolysis products indicated that AgaB is an endo-type α-agarase, producing agarotetraose and agarohexaose. Secondly, AgaB truncated CBM2 showed increased Km values, suggesting that CBM2 aids in substrate binding. Thirdly, E468 and D333 are possibly catalytic amino acids, which was supported by molecular docking results and mutants. Biochemical characterization of first reported CBM2-containing agarase and catalytic mechanism study lay the foundation for the exploration and development of α-agarases in the future.

Indigenous fungal strains isolation and molecular identification from coffee pulp for the production of pectic oligosaccharides

Coffee pulp (CP) is a significant agro-industrial waste generated during coffee bean processing, which possess substantial environmental contamination and is rich in pectin. The primary objective of this study was to investigate the conversion of pectin extracted from coffee pulp into pectic oligosaccharides (POS) using native microbial strains. The study aimed to optimize the growing conditions, including temperature, time, and pectin concentration, to assess the productivity of pectinase. Two fungal strains that exhibited the highest growth on CP were isolated and subsequently identified as Aspergillus fumigatus P-1007 and A. fumigatus HA1, employing 5.8S rRNA gene sequencing. The optimization of temperature for the organism was carried out between 25 and 45 °C; compared to the other temperatures at 45 °C the productivity of pectinase was high; the exact temperature was used for the time experiment where we found that compared to the A. fumigatus P-1007, A. fumigates HA1 was showed high enzyme productivity on 6th day. Hence, the highest productivity of endo-pectinase was seen at a temperature of 45 °C on the 6th day using isolated A. fumigates HA1 in the CP with 1% of coffee pectin. Additionally, the produced POS were screened and confirmed through TLC and HPLC analysis. The antioxidant activity of the POS derived from the separated CP demonstrated an effective concentration (EC50) of 400 µg/ml. The study indicates that the efficient utilization of CP waste for producing potentially valuable functional food ingredients, such as POS, holds promise for commercial development.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03811-9.

Anti-obesity effect of Neoagaro-oligosaccharides with overweight and obese subjects: a 16-week, randomized, double-blind, placebo-controlled clinical trial

BACKGROUND

This trial aimed to evaluate the anti-obesity effects and safety of Neoagaro-oligosaccharides (NAOs) in humans in a 16 week, randomized, double-blind, placebo-controlled clinical trial.

METHODS

One hundred overweight or obese subjects with a body mass index of 23 to 34.9 kg/m2 and a percent body fat of > 25% for males or > 30% for females were enrolled. NAOs or placebo products were administered at 3 g (twice a day, four capsules once) each for 16 weeks. Efficacy and safety biomarkers were measured before and after intervention.

RESULTS

After 16 weeks of intervention, the group administered with NAOs had statistically significant decreases in visceral fat area and visceral-subcutaneous fat area ratio compared to the placebo group. The NAOs group suppressed the increase in weight and BMI compared to the placebo group, which was significant between groups. High-density lipoprotein- cholesterol was increased in the group administered with NAOs, which showed a significant trend compared to the placebo group. Clinical changes were not observed for any safety biomarkers.

CONCLUSIONS

These results suggest that NAOs have a beneficial effect on obesity. Thus, NAOs could be used as an anti-obesity supplement without side effects.

TRIAL REGISTRATION

cris.nih.go.kr: (KCT0006640, 07/10/2021).

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.

Rehashing Our Insight of Seaweeds as a Potential Source of Foods, Nutraceuticals, and Pharmaceuticals

In a few Southeast Asian nations, seaweeds have been a staple of the cuisine since prehistoric times. Seaweeds are currently becoming more and more popular around the world due to their superior nutritional value and medicinal properties. This is because of rising seaweed production on a global scale and substantial research on their composition and bioactivities over the past 20 years. By reviewing several articles in the literature, this review aimed to provide comprehensive information about the primary and secondary metabolites and various classes of bioactive compounds, such as polysaccharides, polyphenols, proteins, and essential fatty acids, along with their bioactivities, in a single article. This review also highlights the potential of seaweeds in the development of nutraceuticals, with a particular focus on their ability to enhance human health and overall well-being. In addition, we discuss the challenges and potential opportunities associated with the advancement of pharmaceuticals and nutraceuticals derived from seaweeds, as well as their incorporation into different industrial sectors. Furthermore, we find that many bioactive constituents found in seaweeds have demonstrated potential in terms of different therapeutic attributes, including antioxidative, anti-inflammatory, anticancer, and other properties. In conclusion, seaweed-based bioactive compounds have a huge potential to play an important role in the food, nutraceutical, and pharmaceutical sectors. However, future research should pay more attention to developing efficient techniques for the extraction and purification of compounds as well as their toxicity analysis, clinical efficacy, mode of action, and interactions with regular diets.

Advances on novel iron saccharide-iron (III) complexes as nutritional supplements

Iron deficiency is prevalent worldwide, and iron supplementation is a promising strategy to address iron needs of the body. However, traditional oral supplements such as ferrous sulfate, ferrous succinate, and ferrous gluconate are absorbed in the form of ferrous ions, leading to lipid peroxidation and side effects due to other reasons. In recent years, saccharide-iron (III) complexes (SICs) as novel iron supplements have aroused attention for the high iron absorption rate and no gastrointestinal irritation at oral doses. In addition, research on the biological activities of SICs revealed that they also exhibited good abilities in treating anemia, eliminating free radicals, and regulating the immune response. This review focused on the preparation, structural characterization, and bioactivities of these new iron supplements, as promising candidates for the prevention and treatment of iron deficiency.

Protective effect of agar oligosaccharide on male Drosophila melanogaster suffering from oxidative stress via intestinal microflora activating the Keap1-Nrf2 signaling pathway

Agar oligosaccharide (AOS) is a new kind of marine functional oligosaccharide with generous biological activities. To investigate the antioxidative effects of AOS in vivo, 3 % aqueous hydrogen peroxide (H₂O₂) was used to induce oxidative stress in male Drosophila melanogaster (D. melanogaster) fed 5 % sucrose (SUC). AOS (0.125 %) in the medium extended the lifespan of D. melanogaster suffering from oxidative stress by improving antioxidant capacity and intestinal function. Electron microscopic observation of epithelial cells showed that AOS alleviated the damage caused by H₂O₂ challenge in the intestine of D. melanogaster, including a reduction of gut leakage and maintenance of intestinal length and cell ultrastructure. The Keap1-Nrf2 (analogues of CncC gene in D. melanogaster) signaling pathway was significantly activated based on gene expression levels and a reduction in ROS content in the intestine of D. melanogaster suffering from oxidative stress. The improvement of antioxidant capacity may be related to the regulation of intestinal microflora with AOS supplementation for D. melanogaster. Nrf2-RNAi, sterile and gnotobiotic D. melanogaster were used to validate the hypothesis that AOS activated the Keap1-Nrf2 signaling pathway to achieve antioxidant effects by regulating intestinal microflora. The above results contribute to our understanding of the antioxidative mechanism of AOS and promote its application in the food industry.

Marine enzymes: Classification and application in various industries

Oceans are regarded as a plentiful and sustainable source of biological compounds. Enzymes are a group of marine biomaterials that have recently drawn more attention because they are produced in harsh environmental conditions such as high salinity, extensive pH, a wide temperature range, and high pressure. Hence, marine-derived enzymes are capable of exhibiting remarkable properties due to their unique composition. In this review, we overviewed and discussed characteristics of marine enzymes as well as the sources of marine enzymes, ranging from primitive organisms to vertebrates, and presented the importance, advantages, and challenges of using marine enzymes with a summary of their applications in a variety of industries. Current biotechnological advancements need the study of novel marine enzymes that could be applied in a variety of ways. Resources of marine enzyme can benefit greatly for biotechnological applications duo to their biocompatible, ecofriendly and high effectiveness. It is beneficial to use the unique characteristics offered by marine enzymes to either develop new processes and products or improve existing ones. As a result, marine-derived enzymes have promising potential and are an excellent candidate for a variety of biotechnology applications and a future rise in the use of marine enzymes is to be anticipated.

Probiotic Potential of the Marine Isolate Enterococcus faecium EA9 and In Vivo Evaluation of Its Antisepsis Action in Rats

This study aims to obtain a novel probiotic strain adapted to marine habitats and to assess its antisepsis properties using a cecal ligation and puncture (CLP) model in rodents. The marine Enterococcus faecium EA9 was isolated from marine shrimp samples and evaluated for probiotic potential after phenotypical and molecular identification. In septic animals, hepatic and renal tissues were histologically and biochemically evaluated for inflammation and oxidative stress following the probiotic treatment. Moreover, gene expressions of multiple signaling cascades were determined using RT-PCR. EA9 was identified and genotyped as Enterococcus faecium with a 99.88% identity. EA9 did not exhibit any signs of hemolysis and survived at low pH and elevated concentrations of bile salts. Moreover, EA9 isolate had antibacterial activity against different pathogenic bacteria and could thrive in 6.5% NaCl. Septic animals treated with EA9 had improved liver and kidney functions, lower inflammatory and lipid peroxidation biomarkers, and enhanced antioxidant enzymes. The CLP-induced necrotic histological changes and altered gene expressions of IL-10, IL-1β, INF-γ, COX-2, SOD-1, SOD-2, HO-1, AKT, mTOR, iNOS, and STAT-3 were abolished by the EA9 probiotic in septic animals. The isolate Enterococcus faecium EA9 represents a promising marine probiotic. The in vivo antisepsis testing of EA9 highlighted its potential and effective therapeutic approach.

Enzymatic preparation and potential applications of agar oligosaccharides: a review

Oligosaccharides derived from agar, that is, agarooligosaccharides and neoagarooligosaccharides, have demonstrated various kinds of bioactivities which have been utilized in a variety of fields. Enzymatic hydrolysis is a feasible approach that principally allows for obtaining specific agar oligosaccharides in a sustainable way at an industrial scale. This review summarizes recent technologies employed to improve the properties of agarase. Additionally, the relationship between the degree of polymerization, bioactivities, and potential applications of agar-derived oligosaccharides for pharmaceutical, food, cosmetic, and agricultural industries are discussed. Engineered agarase exhibited general improvement of enzymatic performance, which is mostly achieved by truncation. Rational and semi-rational design assisted by computational methods present the latest strategy for agarase improvement with greatest potential to satisfy future industrial needs. Agarase immobilized on magnetic Fe3O4 nanoparticles via covalent bond formation showed characteristics well suited for industry. Additionally, albeit with the relationship between the degree of polymerization and versatile bioactivities like anti-oxidants, anti-inflammatory, anti-microbial agents, prebiotics and in skin care of agar-derived oligosaccharides are discussed here, further researches are still needed to unravel the complicated relationship between bioactivity and structure of the different oligosaccharides.

Hepatoprotective Effect of Millettia dielsiana: In Vitro and In Silico Study

In silico docking studies of 50 selected compounds from Millettia dielsiana Harms ex Diels (family Leguminosae) were docked into the binding pocket of the PI3K/mTOR protein. In there, compounds trans-3-O-p-hydroxycinnamoyl ursolic acid (1) and 5,7,4'-trihydroxyisoflavone 7-O-β-D-apiofuranosyl-(1→6)-β-D-glucopyranoside (2) are predicted to be very promising inhibitors against PI3K/mTOR. They direct their cytotoxic activity against Hepatocellular carcinoma with binding affinity (BA) values, the pulling work spent to the co-crystallized ligand from the binding site of PI3K/mTOR (W and F_max), and the non-equilibrium binding free energy (∆G_neq^Jar) as BA values = -9.237 and -9.083 kcal/mol, W = 83.5 ± 10.6 kcal/mol with F_max = 336.2 ± 45.3 pN and 126.6 ± 21.7 kcal/mol with F_max = 430.3 ± 84.0 pN, and ∆G_neq^Jar = -69.86074 and -101.2317 kcal/mol, respectively. In molecular dynamic simulation, the RMSD value of the PI3K/mTOR complex with compounds (1 and 2) was in the range of 0.3 nm to the end of the simulation. Therefore, the compounds (1 and 2) are predicted to be very promising inhibitors against PI3K/mTOR. The crude extract, ethyl acetate fraction and compounds (1 and 2) from Millettia dielsiana exhibited moderate to potent in vitro cytotoxicity on Hepatocellular carcinoma cell line with IC₅₀ values of 81.2 µg/mL, 60.4 µg/mL, 23.1 μM, and 16.3 μM, respectively, and showed relatively potent to potent in vitro antioxidant activity on mouse hepatocytes with ED₅₀ values of 24.4 µg/mL, 19.3 µg/mL, 30.7 μM, and 20.5 μM, respectively. In conclusion, Millettia dielsiana and compounds (1 and 2) are predicted to have very promising cytotoxic activity against Hepatocellular carcinoma and have a hepatoprotective effect.

Intestinal permeability of agaro-oligosaccharides: Transport across Caco-2 cell monolayers and pharmacokinetics in rats

Agaro-oligosaccharides (AOSs), even-numbered oligosaccharides prepared from agar, are applied to various food, including supplements, drinks, and jellies because of their biological activities. This study aimed to evaluate the AOS permeation in the gastrointestinal tract in vivo and in vitro. Agarobiose (Abi), agarotetraose (Ate), and agarohexaose (Ahe) were detected in rat plasma after oral administration of AOSs. The detection level of agarobiose in the plasma was higher than that of agarohexaose, which was consistent with the permeation study using Caco-2 cell monolayers. Further, the adenosine triphosphate inhibitor (sodium azide) or endocytosis inhibitor (colchicine) did not inhibit AOS permeation through Caco-2 cell monolayers. Conversely, AOS permeation enhanced upon treatment with cytochalasin B, a tight junction disrupter, suggesting that AOSs might have passed mainly through the tight junctions between the intestinal epithelial cells. These results indicate that AOSs, especially agarobiose, can be absorbed as an intact form via the gastrointestinal tract across the intestinal epithelium through the paracellular pathway.

Characterization of a novel β-agarase from Antarctic macroalgae-associated bacteria metagenomic library and anti-inflammatory activity of the enzymatic hydrolysates

An agarase gene (aga1904) that codes a protein with 640 amino acids was obtained from the metagenomic library of macroalgae-associated bacteria collected from King George Island, Antarctica. Gene aga1904 was expressed in Escherichia coli BL21 (DE3) and recombinant Aga1904 was purified by His Bind Purification kit. The optimal temperature and pH for the activity of Aga1904 were 50°C and 6.0, respectively. Fe³⁺ and Cu²⁺ significantly inhibited the activity of Aga1904. The V_max and K_m values of recombinant Aga1904 were 108.70 mg/ml min and 6.51 mg/ml, respectively. The degradation products of Aga1904 against agarose substrate were mainly neoagarobiose, neoagarotetraose, and neoagarohexaose analyzed by thin layer chromatography. The cellular immunoassay of enzymatic hydrolysates was subsequently carried out, and the results showed that agaro-oligosaccharides dominated by neoagarobiose significantly inhibited key pro-inflammatory markers including, nitric oxide (NO), interleukins 6 (IL-6), and tumor necrosis factor α (TNF-α). This work provides a promising candidate for development recombinant industrial enzyme to prepare agaro-oligosaccharides, and paved up a new path for the exploitation of natural anti-inflammatory agent in the future.

Oligosaccharides from agar extends lifespan through activation of unfolded protein response via SIR-2.1 in Caenorhabditis elegans

PURPOSE

Agaro-oligosaccharides (AGO), hydrolysis products of agarose, is known to have antioxidant and anti-inflammatory properties. Speculating that AGO is effective for preventing aging, we investigated the longevity-supporting effects of AGO and their mechanisms using Caenorhabditis elegans.

METHODS

Caenorhabditis elegans were fed AGO from young adulthood. The lifespan, locomotory activity, lipofuscin accumulation, and heat stress resistance of the worms were examined. To elucidate mechanisms of AGO-mediated longevity, we conducted comprehensive expression analysis using microarrays. Moreover, we used quantitative real-time PCR (qRT-PCR) to verify the genes showing differential expression levels. Furthermore, we measured the lifespan of loss-of-function mutants to determine the genes related to AGO-mediated longevity.

RESULTS

AGO extended the lifespan of C. elegans, reduced lipofuscin accumulation, and maintained vigorous locomotion. The microarray analysis revealed that the endoplasmic reticulum-unfolded protein response (ER-UPR) and insulin/insulin-like growth factor-1-mediated signaling (IIS) pathway were activated in AGO-fed worms. The qRT-PCR analysis showed that AGO treatment suppressed sir-2.1 expression, which is a negative regulator of ER-UPR. In loss-of-function mutant of sir-2.1, AGO-induced longevity and heat stress resistance were decreased or cancelled completely. Furthermore, the pro-longevity effect of AGO was decreased in loss-of-function mutants of abnormal Dauer formation (daf) -2 and daf-16, which are IIS pathway-related genes.

CONCLUSION

AGO delays the C. elegans aging process and extends their lifespan through the activations of ER-UPR and the IIS pathway.

Simultaneous quantification of marine neutral neoagaro-oligosaccharides and agar-oligosaccharides by the UHPLC-MS/MS method: application to the intestinal transport study by using the Caco-2 cell monolayer

A sensitive and robust ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was established for the first time to simultaneously quantify marine neutral neoagaro-oligosaccharides (NAOS) and agar-oligosaccharides (AOS) with different degrees of polymerization (DP) in Hanks' balanced salt solution (HBSS). The separation was achieved on a BEH amide column using a mobile phase of acetonitrile-10 mmol L^-1 ammonium acetate (58 : 42, v/v) with an isocratic elution program. The total analysis time was 3.5 min. The mass spectra were acquired in the multiple reaction monitoring (MRM) pattern by using a heated-electrospray ionization (H-ESI) source operating in the positive ionization mode. The linear range was 40-20 000 nmol L^-1. The accuracy and precision ranged from 91.5 to 110.0% and 0.9 to 10.4%, respectively. The extraction recovery was consistent and reproducible. The stability was within 90.3-110.8%. The matrix effect, carryover, and dilution integrity were all satisfactory. Moreover, the validated method was successfully applied to the intestinal transport study by using the Caco-2 cell monolayer in vitro. The results revealed that neoagarobiose, neoagarotetraose, neoagarohexaose, agarotriose, agaropentose, and agaroheptose were transported by a paracellular pathway.

Multi-Step Enzymatic Production and Purification of 2-Keto-3-Deoxy-Galactonate from Red-Macroalgae-Derived Agarose

2-keto-3-deoxy sugar acids, which have potential as precursors in medicinal compound production, have gained attention in various fields. Among these acids, 2-keto-3-deoxy-l-galactonate (KDGal) has been biologically produced from D-galacturonate originating from plant-derived pectin. KDGal is also found in the catabolic pathway of 3,6-anhydro-l-galactose (AHG), the main component of red-algae-derived agarose. AHG is converted to 3,6-anhydrogalactonate by AHG dehydrogenase and subsequently isomerized to KDGal by 3,6-anhydrogalactonate cycloisomerase. Therefore, we used the above-described pathway to produce KDGal from agarose. Agarose was depolymerized to AHG and to agarotriose (AgaDP3) and agaropentaose (AgaDP5), both of which have significantly higher molecular weights than AHG. When only AHG was converted to KDGal, AgaDP3 and AgaDP5 remained unreacted. Finally, KDGal was effectively purified from the enzymatic products by size-exclusion chromatography based on the differences in molecular weights. These results show that KDGal can be enzymatically produced and purified from agarose for use as a precursor to high-value products.

A Facile In Situ Synthesis of Resorcinol-Mediated Silver Nanoparticles and the Fabrication of Agar-Based Functional Nanocomposite Films

The in situ synthesis of silver nanoparticles (AgNPs) was performed using resorcinol and agar to produce agar-based antioxidant and antimicrobial films. AgNPs were regularly dispersed on the film matrix, and their presence improved the thermal stability of films. Additionally, the addition of AgNPs slightly increased the agar-based film’s tensile strength (~10%), hydrophobicity (~40%), and water vapor barrier properties (~20%) at 1.5 wt% of AgNP concentration. The resorcinol also imparted UV-barrier and antioxidant activity to the agar-based film. In particular, the agar-based film containing a higher quantity of AgNPs (>1.0 wt%) was highly effective against the foodborne pathogenic bacteria L. monocytogenes and E. coli. Therefore, agar-based composite films with improved physicochemical and functional properties may be promising for active packaging.

Algal polysaccharides and derivatives as potential therapeutics for obesity and related metabolic diseases

The potential and challenges of algal polysaccharides and their derivatives as potential therapeutic agents for obesity and its related metabolic diseases.

Characterizing of a new α-agarase AgaE from Thalassomonas sp. LD5 and probing its catalytically essential residues

A new α-agarase AgaE belonging to glycoside hydrolase (GH) family 96 was identified and cloned from marine bacterium Thalassomonas sp. LD5. AgaE consists of 926 amino acids with a theoretical molecular mass of 97 kDa. The optimum temperature and pH for recombinant AgaE were 35 °C and 7.0, respectively. In contrast to known α-agarases, the activity of AgaE does not depend on Ca²⁺, but on Na⁺. Thin-layer chromatography and ¹³C NMR analysis revealed that AgaE endohydrolytic of agarose to produce agarotetraose and agarohexaose as the final main products. Extensive site-directed mutagenesis studies on the conserved carboxylic amino acids of GH96 revealed two essential amino acids for AgaE, D779 and D781. Replacing D779 with G779 leads to complete inactivation of the enzyme, while D781G results in 70% loss of activity. Later studies showed that site D781 involved in the binding of Na⁺, and its mutation raised the optimal concentration of Na⁺ 4 times higher than that of the wild type. However, attempts to rescue the mutant's activities with sodium azide were failed. Kinetic parameters comparison of AgaE, AgaD, another α-agarase from LD5, and their mutants revealed that the former aspartic acid plays critical role in the catalysis.

Advances in agaro-oligosaccharides preparation and bioactivities for revealing the structure-function relationship

Agaro-oligosaccharides originating from red algae have attracted increasing attention in both basic theoretical research and applied fields due to their excellent bioactivities, which indicates the wide prospects of agaro-oligosaccharides for application in the food, pharmaceutical and cosmetic industries. Thus, a considerable number of studies regarding functional agaro-oligosaccharides preparation as well as the bioactivities exploration have been carried out. Based on these studies, this review first introduced different methods that have been used in agar extraction from red algae, and further provided research progress on arylsulfatase. Then, different methods used for agaro-oligosaccharides production were summarized. Moreover, the abundant bioactivities of agaro-oligosaccharides were described in detail. Finally, this review has discussed current research problems and further provided critical aspects, which may be helpful for revealing the structure-function relationship of agaro-oligosaccharide.

Recent advances in marine algae oligosaccharides: structure, analysis, and potential prebiotic activities

Marine algae contain abundant polysaccharides that support a range of health-promoting activities; however, the high molecular weight, high viscosity, and low solubility of marine algae polysaccharides (MAPs) limit their application in food, agriculture and medicine. Thus, as the degradation products of MAPs, marine algae oligosaccharides (MAOs) have drawn increasing attention. Most MAOs are non-digestible by digestive enzyme in the human gastrointestinal tract, but are fermented by bacteria in the gut and converted into short-chain fatty acids (SCFAs). MAOs can selectively enhance the activities of some populations of beneficial bacteria and stimulate a series of prebiotic effects, such as anti-oxidant, anti-diabetic, anti-tumour. However, the exact structures of MAOs and their prebiotic activities are, to a large extent, unexplored. This review summarizes recent advances in the sources, categories, and structure analysis methods of MAOs, emphasizing their effects on gut microbiota and its metabolite SCFAs as well as the resulting range of probiotic activities.

Agar oligosaccharides: A review of preparation, structures, bioactivities and application

Agar, a gelatinous polysaccharide which is in the cell wall of many red algae, is widely used as food and gelling agent. Agar oligosaccharides (AOs), the hydrolysate of agar, show much more kinds of bio-activities because of its lower molecular weight, better water solubility and higher absorption efficiency. It is indicated that AOs with different structure and degree of polymerization, i.e. series of agaro-oligosaccharides and neoagaro-oligosaccharides, can be obtained under different preparation conditions. In addition, the biological activities of AOs are diversely and closely correlated to the composition and structure. This review aims to comprehensively summarize the preparation, structural characteristics and bio-activities of AOs, so as to provide a reference for applications of AOs as marine natural products in pharmacological, cosmetics and nutraceutical fields.

In Vitro Prebiotic and Anti-Colon Cancer Activities of Agar-Derived Sugars from Red Seaweeds

Numerous health benefits of diets containing red seaweeds or agar-derived sugar mixtures produced by enzymatic or acid hydrolysis of agar have been reported. However, among various agar-derived sugars, the key components that confer health-beneficial effects, such as prebiotic and anti-colon cancer activities, remain unclear. Here, we prepared various agar-derived sugars by multiple enzymatic reactions using an endo-type and an exo-type of β-agarase and a neoagarobiose hydrolase and tested their in vitro prebiotic and anti-colon cancer activities. Among various agar-derived sugars, agarotriose exhibited prebiotic activity that was verified based on the fermentability of agarotriose by probiotic bifidobacteria. Furthermore, we demonstrated the anti-colon cancer activity of 3,6-anhydro-l-galactose, which significantly inhibited the proliferation of human colon cancer cells and induced their apoptosis. Our results provide crucial information regarding the key compounds derived from red seaweeds that confer beneficial health effects, including prebiotic and anti-colon cancer activities, to the host.

Overview on Microbial Enzymatic Production of Algal Oligosaccharides for Nutraceutical Applications

Global requirement for algal foods is increasing, as they are progressively consumed for its nutrition and health. Macroalgae is a proven source of metabolites, proteins, pigments, bioactive compounds, and algal polysaccharides. The unique polysaccharides such as agar, carrageenan, porphyran, alginate, fucoidan, laminarin, and ulvan are known for its wide range of bioactivities and extensively used for applications from tissue engineering to drug delivery. However, there are few limitations due to its high molecular size, low compatibility, and hydrocolloid nature. Hence, the enzymatically produced algal oligosaccharides have drawn tremendous attention due to its green synthesis, solubility, and lower molecular size. They are reported to have bioactivities including antioxidant, antiglycemic, immunostimulatory, anti-inflammatory, and prebiotic activities, which can be used in the healthcare and nutraceutical industry for the manufacture of functional foods and dietary supplements. However, identification of potential microorganisms, producing polysaccharide hydrolyzing enzymes, remains a major bottle neck for efficient utilization of bioactive algal oligosaccharides. This review summarizes the recent developments in the identification and characterization of microbial enzymes for the production of bioactive algal oligosaccharides. This can improve our understanding of bioactive algal oligosaccharides and pave way for efficient utilization of macroalgae to prevent various chronic diseases.

Characterization of ACE Inhibitory Peptides Prepared from Pyropia pseudolinearis Protein

More than 7000 red algae species have been classified. Although most of them are underused, they are a protein-rich marine resource. The hydrolysates of red algal proteins are good candidates for the inhibition of the angiotensin-I-converting enzyme (ACE). The ACE is one of the key factors for cardiovascular disease, and the inhibition of ACE activity is related to the prevention of high blood pressure. To better understand the relationship between the hydrolysates of red algal proteins and the inhibition of ACE activity, we attempted to identify novel ACE inhibitory peptides from Pyropia pseudolinearis. We prepared water soluble proteins (WSP) containing phycoerythrin, phycocyanin, allophycocyanin, and ribulose 1,5-bisphosphate carboxylase/oxygenase. In vitro analysis showed that the thermolysin hydrolysate of the WSP had high ACE inhibitory activity compared to that of WSP. We then identified 42 peptides in the hydrolysate by high-performance liquid chromatography and mass spectrometry. Among 42 peptides, 23 peptides were found in chloroplast proteins. We then synthesized the uncharacterized peptides ARY, YLR, and LRM and measured the ACE inhibitory activity. LRM showed a low IC₅₀ value (0.15 μmol) compared to ARY and YLR (1.3 and 5.8 μmol). In silico analysis revealed that the LRM sequence was conserved in cpcA from Bangiales and Florideophyceae, indicating that the novel ACE inhibitory peptide LRM was highly conserved in red algae.

The degradation activities for three seaweed polysaccharides of Shewanella sp. WPAGA9 isolated from deep-sea sediments

Seaweed oligosaccharides possess great bioactivities. However, different microbial strains are required to degrade multiple polysaccharides due to their limited biodegradability, thereby increasing the cost and complexity of production. Shewanella sp. WPAGA9 was isolated from deep-sea sediments in this study. According to the genomic and biochemical analyses, the extracellular fermentation broth of WPAGA9 had versatile degradation abilities for three typical seaweed polysaccharides including agar, carrageenan, and alginate. The maximum enzyme activities of the extracellular fermentation broth of WPAGA9 were 71.63, 76.4, and 735.13 U/ml for the degradation of agar, alginate, and carrageenan, respectively. Moreover, multiple seaweed oligosaccharides can be produced by the extracellular fermentation broth of WPAGA9 under similar optimum conditions. Therefore, WPAGA9 can simultaneously degrade three types of seaweed polysaccharides under similar conditions, thereby greatly reducing the production cost of seaweed oligosaccharides. This finding indicates that Shewanella sp. WPAGA9 is an ideal biochemical tool for producing multiple active seaweed oligosaccharides at low costs and is also an important participant in the carbon cycle process of the deep-sea environment.

Antioxidant Potential of Physicochemically Characterized Gracilaria blodgettii Sulfated Polysaccharides

Marine rhodophyte polysaccharides have a wide range of described biological properties with nontoxic characteristics, and show great potential in prebiotics and the functional foods industries. However, there is a virtual lack of Gracilaria blodgettii polysaccharides (GBP) profiling and their bioactivities. This study was designed while keeping in view the lack of physical and chemical characterization of GBP. This polysaccharide was also not previously tested for any bioactivities. A linear random coil conformation was observed for GBP, which was found to be a polysaccharide. A significant sulfate (w/w, 9.16%) and 3,6-anhydrogalactose (AHG, w/w, 17.97%) content was found in GBP. The significant difference in its setting (27.33 °C) and melting (64.33 °C) points makes it resistant to increasing heat. This, in turn, points to its utility in industrial scale processing and in enhancing the shelf-life of products under high temperatures. A radical scavenging activity of 19.80%, 25.42% and 8.80% was noted for GBP (3 mg/mL) in 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2’-azino-bis (ABTS) and hydroxyl radical (HO) scavenging assays, respectively. Therefore, the findings suggest that Gracilaria blodgettii polysaccharides display a good antioxidant potential and may have potential applications in the functional food industry.

Modulation of green to red photoconversion of GFP during fluorescent microscopy by carbon source and oxygen availability

Studies have reported on the ability of green fluorescent proteins to photoconvert into a red fluorescent form under various conditions, such as the presence of oxidants, hypoxia, as well as under benign conditions using irradiation with a 405 nm laser. Here, we show that in Saccharomyces cerevisiae yeast green fluorescent protein (GFP) (S65T) fused to different cellular proteins can easily photoconvert into a red form when cells are grown in media with nonfermentable carbon sources. This photoconversion occurs during standard microscopy between glass slide and coverslip but is completely prevented by imaging on pads of solid medium or in a large volume of medium on an inverted microscope. The observed effect was due to rapid hypoxia of cells with respiratory metabolism in standard conditions for upright microscopy. Photoconversion could be prevented by antioxidant treatment, suggesting that it proceeds via the effects of reactive oxidative species emerging in response to oxygen deficiency. Our results show the need for caution during upright microscopy imaging in conditions where there is active respiration and demonstrate simple approaches to prevent unwanted GFP photoconversion. They also provide easy means of performing photoconversion experiments on existing GFP-bearing cell lines, at least in the case of yeast.

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.

Production of Neoagaro-Oligosaccharides With Various Degrees of Polymerization by Using a Truncated Marine Agarase

Bioactivities, such as freshness maintenance, whitening, and prebiotics, of marine neoagaro-oligosaccharides (NAOS) with 4-12 degrees of polymerization (DPs) have been proven. However, NAOS produced by most marine β-agarases always possess low DPs (≤6) and limited categories; thus, a strategy that can efficiently produce NAOS especially with various DPs ≥8 must be developed. In this study, 60 amino acid residues with no functional annotation result were removed from the C-terminal of agarase AgaM1, and truncated recombinant AgaM1 (trAgaM1) was found to have the ability to produce NAOS with various DPs (4-12) under certain conditions. The catalytic efficiency and stability of trAgaM1 were obviously lower than the wild type (rAgaM1), which probably endowed trAgaM1 with the ability to produce NAOS with various DPs. The optimum conditions for various NAOS production included mixing 1% agarose (w/v) with 10.26 U/ml trAgaM1 and incubating the mixture at 50°C in deionized water for 100 min. This strategy produced neoagarotetraose (NA4), neoagarohexaose (NA6), neoagarooctaose (NA8), neoagarodecaose (NA10), and neoagarododecaose (NA12) at final concentrations of 0.15, 1.53, 1.53, 3.02, and 3.02 g/L, respectively. The NAOS served as end-products of the reaction. The conditions for trAgaM1 expression in a shake flask and 5 L fermentation tank were optimized, and the yields of trAgaM1 increased by 56- and 842-fold compared with those before optimization, respectively. This study provides numerous substrate sources for production and activity tests of NAOS with high DPs and offers a foundation for large-scale production of NAOS with various DPs at a low cost.

Protective effects of dietary mannan oligosaccharide on heat stress-induced hepatic damage in broilers

Heat stress is a major concern in broiler's production, which can damage liver of broilers. This study investigated the protective effects of mannan oligosaccharide (MOS) on heat stress-induced hepatic injury in broilers. A total of 144 day-old male chicks were allocated into three treatment groups. Broilers raised under normal ambient temperature were fed a basal diet (control group), and broilers under heat stress (32-33 °C for 8 h daily) were given the basal diet supplemented without MOS (heat stress group) or with 1 g/kg MOS (MOS group) for 42 days. Compared with the control group, heat stress reduced liver weight, whereas increased aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities in the serum. It also reduced glutathione peroxidase (GSH-Px) activity in the serum and liver, GSH content, and superoxide dismutase (SOD) activity in the liver, but increased malondialdehyde (MDA) concentration in the serum and liver. Dietary MOS decreased serum ALT activity in heat-stressed broilers. MOS inclusion also decreased serum MDA content, but elevated hepatic GSH-Px and SOD activities, with MDA content and GSH-Px activity still being different from the control group, and SOD activity being similar to the control group. Heat stress increased concentrations of tumor necrosis factor α (TNF-α) in the serum and liver, interleukin-1β (IL-1β) in the liver, and mRNA abundances of HSP70, TLR4, MyD88, TNF-α, and IL-1β in the liver of broilers. Serum TNF-α content and mRNA abundances of hepatic TLR4 and TNF-α in MOS group were lower than the heat stress group, whereas these indexes were still higher than the control group. Our results indicated that dietary MOS ameliorated hepatic damage in heat-stressed broilers through alleviation of oxidative stress and inflammation.

In Silico Analysis of ACE Inhibitory Peptides from Chloroplast Proteins of Red Alga Grateloupia asiatica

Inhibition of angiotensin I-converting enzyme (ACE) is one of the key factors to repress high blood pressure. Although many studies have been reported that seaweed protein hydrolysates showed the ACE inhibitory activity, the comprehensive understanding of the relationship was still unclear. In this study, we employed chloroplast genome for in silico analysis and compared it with in vitro experiments. We first extracted water-soluble proteins (WSP) from red alga Grateloupia asiatica, which contained mainly PE, PC, APC, and Rbc, and prepared WSP hydrolysate by thermolysin, resulting that the hydrolysate showed ACE inhibitory activity. Then, we determined the complete chloroplast genome of G. asiatica (187,518 bp: 206 protein-coding genes, 29 tRNA, and 3 rRNA) and clarified the amino acid sequences of main WSP, i.e., phycobiliproteins and Rubisco, to perform in silico analysis. Consequently, 190 potential ACE inhibitory peptides existed in the main WSP sequences, and 21 peptides were obtained by in silico thermolysin digestion. By comparing in vitro and in silico analyses, in vitro ACE inhibitory activity was correlated to the IC₅₀ value from in silico digestion. Therefore, in silico approach provides insight into the comprehensive understanding of the potential bioactive peptides from seaweed proteins.

Odd-numbered agaro-oligosaccharides alleviate type 2 diabetes mellitus and related colonic microbiota dysbiosis in mice

Agaro- and neoagaro-oligosaccharides with even-numbered sugar units possess a variety of biological activities. However, the effects of the odd-numbered oligosaccharides from Gracilaria agarose (OGAOs) on type 2 diabetes mellitus (T2DM) have not been reported. In this study, we aimed to evaluate the effects of OGAOs on anti-T2DM from different aspects. We found that OGAOs treatment could alleviate oxidative stress, inflammation, and the related hyperglycemia, insulin resistance, lipid accumulation, and obesity in high-fat diet (HFD) induced T2DM. Investigation of the underlying mechanism showed that colitis and colonic microbiota dysbiosis in T2DM mice were ameliorated after OGAOs treatment. First, OGAOs increased the expression of ZO-1, occludin, and AMPK, and suppressed the TLR4/MAPK/NF-κB pathway in colon indicating that OGAOs enhance intestinal integrity and conduct the anti-apoptosis effects to prevent the invasion of toxins and harmful microorganisms. Moreover, the relative abundance of Akkermansia was significantly upregulated in the gut microbiome of T2DM mice associated with a dramatic decrease of the relative abundance of Helicobacter, which are both beneficial for alleviating colitis and T2DM. In addition, Spearman's correlation analysis indicated that changes in the colonic microbiota could regulate oxidative stress, inflammation, and hyperlipidemia. In summary, the underlying mechanism of OGAOs on alleviating colitis and colonic microbiota dysbiosis in T2DM has been intensively studied, illustrating that OGAOs could be further developed as a potential pharmaceutical agent for T2DM.

Marine oligosaccharides originated from seaweeds: Source, preparation, structure, physiological activity and applications

Marine polysaccharides originated from seaweeds, including agar, alginate, carrageenan, and fucoidan, possess various kinds of physiological activities and have been widely used in food, agricultural and medical areas. However, the application has been greatly limited by their poor solubility and low bioavailability. Thus marine oligosaccharides, as the degradation products of those polysaccharides, have drawn increasing attentions due to their obvious biological activities, good solubility and excellent bioavailability. This review will summarize the recent advances on the source, molecular structure and physiological activity of marine oligosaccharides, emphasizing their application as functional food additives. Furthermore, the relationship between the structure and the physiological activity of marine oligosaccharides is also elucidated and highlighted. The review concludes with an outlook toward potential applications for preparing the functional oligosaccharides in food biotechnology and agriculture fields.

Lophenol and lathosterol from resin of Commiphora kua possess hepatoprotective effects in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Drug induced liver damage remains a prevalent concern in healthcare and may reduce the effectiveness of therapy by compromising therapeutic regimens. Many Commiphora species are known for their medicinal properties, and some of them are used traditionally for hepatoprotective effect. In the course of our drugs discovery from natural sources, phytosterols (lophenol (Lop) and lathosterol (Lat)), isolated from Commiphora kua were studied to evaluate their hepatoprotective effects in acetaminophen (APAP) induced hepatotoxicity in mice.

AIMS AND OBJECTIVE

To evaluate the hepatoprotective effects of phytosterols isolated from C. kua using in vivo experimental model.

MATERIALS AND METHODS

Mice of either sex were divided into 7 groups: Vehicle, silymarin (SLY), acetaminophen (APAP), Lop 25, Lop 50, Lat 25, Lat 50 (n = 5). Vehicle group received only vehicle (0.1% DMSO solution) for 7 days, APAP group received single dose of acetaminophen on day 7 and SLY group received silymarin for 7 days. Lop 25 and Lop 50 received low and high doses of Lop (25 μg/kg BW and 50 μg/kg BW), respectively, for 7 days, while Lat 25 and Lat 50 received low and high doses of Lat (25 μg/kg BW and 50 μg/kg BW) for 7 days. On day 7, all animals except Vehicle group kept fasted for 18 h and received APAP i. p. 400 mg/kg BW. After 20 h of APAP administration, the animals anesthetized with light chloroform and scarified by cervical decapitation. The blood serum and liver tissue samples were collected for biochemical and histopathological analysis. Liver function tests (LFTs) including lactate deydrogenase (LDH), alkaline phosphatase (ALP), alanine transaminase (ALT), aspartate transaminase (AST) and direct bilirubin) were used as biochemical parameters. While catalase (CAT), superoxide dismutase (SOD) and reduced glutathione (GSH) were taken as anti-oxidant enzymes.

RESULTS

Significant increase in levels of ALT, AST, ALP, LDH and direct bilirubin, and significant decrease in concentration of anti-oxidant enzymes (SOD, CAT and GSH) was observed in APAP-treated group. Similarly, histological slides showed obvious signs of damage to liver cells, reflecting acetaminophen induced hepatotoxicity. Treatment of test animals with phytosterols resulted in significant recovery of LFTs profile and concentration of anti-oxidant enzymes. Similarly, significant improvement of liver tissues was noted in histological analysis.

CONCLUSIONS

Both phytosterols possessed hepatoprotective potential and should be further evaluated for acute toxicity studies and pharmacokinetics/pharmacodynamics profile.

Beneficial Effects of Low-Calorie-Carbohydrate/High-Agar Diet on Cardiometabolic Disorders Associated with Non-Alcoholic Fatty Liver Disease in Obese Rats

Energy restriction and low carbohydrate diets are recommended as nutrition therapies to prevent becoming overweight or obese. However, their beneficial effects in non-alcoholic fatty liver disease (NAFLD) are less well investigated. In addition, the effects of the type of polysaccharides incorporated into these diets and their contents have been scarcely studied. Therefore, this study aimed to elucidate whether low-calorie-carbohydrate high-agar diets could improve liver metabolic dysfunction, membrane fluidity, oxidative damage, and endothelial dysfunction in obese rats. Obesity was induced by feeding rats a high-fat diet (HFD) for 10 weeks. The obese rats were then divided into two homogenous groups: the first group was fed low-calorie-carbohydrate/high-agar diet (LCC/HA) and the second continued to consume the HFD for 4 weeks [obese control (Ob-C)]. Normo-ponderal rats were fed a normal diet during the entire study, and were used as the control (N-C). Compared with the Ob-C group, body weight, hepatic lipids, low density lipoproteins cholesterol (C), the non esterified cholesterol/phospholipids ratio, serum transaminases activities, and lipid peroxidation markers (thiobarbituric acid reactive substances and lipid hydroperoxides) were reduced in LCC/HA group (P<0.05). However, the serum concentration of high density lipoproteins-C was enhanced (P<0.05). In addition, we observed improved antioxidant defence and endothelial dysfunction associated with antioxidant enzymes, such as superoxide dismutase, glutathione peroxidase, and catalase (P<0.05), and nitric oxide level (P<0.05). These findings suggest that hypocaloric diets low in energy and carbohydrates and rich in agar may be beneficial against HFD-induced hepatic steatosis damage, and may be a promising therapeutic strategy to counteract NAFLD development associated with obesity.

Anti-diabetic activities of agaropectin-derived oligosaccharides from Gloiopeltis furcata via regulation of mitochondrial function

The aim of the present study was to investigate whether agaropectin-derived oligosaccharides from Gloiopeltis furcata (SAOs) exert an anti-diabetic effect in sodium palmitate (PA)-induced insulin resistant HepG2 cells. We found that SAOs were co-localized with mitochondria and regulated mitochondrial function. SAOs reduced respiratory chain activities, which led to reduced respiratory oxygen consumption and increased the cellular ADP/ATP ratio in a certain degree of dose-dependent manner. Thus, SAOs alleviated the oxidative stress state in PA-treated cells and, moreover, concurrently regulated the ROS-JNK-IRS-1 pathway. As a result, SAOs enhanced insulin sensitivity and glucose metabolism by activating the IRS-1-AKT-GSK-3β-GS pathway. Additionally, SAOs activated AMPK through both PKA-LKB1 and mitochondrial-regulated energy metabolism pathways. Therefore, SAOs decreased accumulation of lipids and improved lipid metabolism via regulating HMGCR, ACC and SREBP-1 proteins in HepG2 cells. Taken together, we conclude that SAOs could significantly ameliorate diabetic states in vitro via regulating mitochondria and their downstream signaling pathways.

The Potential of Neoagaro-Oligosaccharides as a Treatment of Type II Diabetes in Mice

Type 2 diabetes mellitus (T2DM) accounts for more than 90% of cases of diabetes mellitus, which is harmful to human health. Herein, neoagaro-oligosaccharides (NAOs) were prepared and their potential as a treatment of T2DM was evaluated in KunMing (KM) mice. Specifically, a T2DM mice model was established by the combination of a high-fat diet (HFD) and alloxan injection. Consequently, the mice were given different doses of NAOs (100, 200, or 400 mg/kg) and the differences among groups of mice were recorded. As a result of the NAOs treatment, the fasting blood glucose (FBG) was lowered and the glucose tolerance was improved as compared with the model group. As indicated by the immunohistochemistry assay, the NAOs treatment was able to ameliorate hepatic macrovesicular steatosis and hepatocyte swelling, while it also recovered the number of pancreatic β-cells. Additionally, NAOs administration benefited the antioxidative capacity in mice as evidenced by the upregulation of both glutathione peroxidase and superoxide dismutase activity and the significant reduction of the malondialdehyde concentration. Furthermore, NAOs, as presented by Western blotting, increased the expression of p-ERK1/2, p-JNK, NQO1, HO-1, and PPARγ, via the MAPK, Nrf2, and PPARγ signaling pathways, respectively. In conclusion, NAOs can be used to treat some complications caused by T2DM, and are beneficial in controlling the level of blood glucose and ameliorating the damage of the liver and pancreatic islands.

Anti-Inflammatory Activities of Marine Algae in Neurodegenerative Diseases

Neuroinflammation is one of the main contributors to the onset and progression of neurodegenerative diseases such as Alzheimer’s and Parkinson’s diseases. Microglial and astrocyte activation is a brain defense mechanism to counteract harmful pathogens and damaged tissues, while their prolonged activation induces neuroinflammation that can trigger or exacerbate neurodegeneration. Unfortunately, to date there are no pharmacological therapies able to slow down or stop the progression of neurodegeneration. For this reason, research is turning to the identification of natural compounds with protective action against these diseases. Considering the important role of neuroinflammation in the onset and development of neurodegenerative pathologies, natural compounds with anti-inflammatory activity could be good candidates for developing effective therapeutic strategies. Marine organisms represent a huge source of natural compounds, and among them, algae are appreciated sources of important bioactive components such as antioxidants, proteins, vitamins, minerals, soluble dietary fibers, polyunsaturated fatty acids, polysaccharides, sterols, carotenoids, tocopherols, terpenes, phycobilins, phycocolloids, and phycocyanins. Recently, numerous anti-inflammatory compounds have been isolated from marine algae with potential protective efficacy against neuroinflammation. This review highlights the key inflammatory processes involved in neurodegeneration and the potential of specific compounds from marine algae to counteract neuroinflammation in the CNS.

Simple Preparation of Diverse Neoagaro-Oligosaccharides

A simple method for obtaining pure and well-defined oligosaccharides was established by hydrolyzing agar with β-agarase from Vibrio natriegens. The conditions for enzymolysis were optimized as follows: a temperature of 45 °C, a pH of 8.5, a substrate concentration of 0.3%, an enzyme amount of 100 U/g and an enzymolysis time of 20 h. Neoagaro-oligosaccharides with different degrees of polymerization were obtained by hydrolyzing agar with β-agarase for different lengths of time. After removing pigments using activated carbon and salts by dialyzing, the enzyme hydrolysis solution was separated with Bio-Gel P2 column chromatography. Neoagaro-oligosaccharides with different degrees of polymerization were acquired. By comparing with authentic standard substances, along with further confirmation by FTIR, MS and NMR, structures of the purified neoagaro-oligosaccharides were identified as neoagarobiose (NA2), neoagaroteraose (NA4), neoagarohexaose (NA6), neoagarooctaose (NA8), neoagaro-decaose (NA10) and neoagarododecaose (NA12) with purities of more than 97.0%. The present study established a method for the preparation of various neoagaro-oligosaccharides that may be of great significance for further study of their bioactivities.

Effectiveness of AOS–iron on iron deficiency anemia in rats

Iron deficiency anemia (IDA) is one of the most serious nutritional problems. This study aimed to evaluate the therapeutic effects of a novel agar oligosaccharide–iron complex (AOS–iron) on rats with IDA, such as iron supplementation and recovery of antioxidant ability. Eighty-four weaned male SD rats were randomly divided into a normal control group (n = 12), which was fed with a standard diet, and an anemia model group (n = 72), which was fed with an iron-deficient diet for 4 weeks to establish a model of IDA. After the model was established, the rats with IDA were divided into six groups, namely, an anemia model group, a ferrous gluconate group, a ferrous sulfate (FeSO₄) group, and low-dose (LD), medium-dose (MD) and high-dose (HD) AOS–iron groups, and fed with an iron-deficient diet and different iron supplements for 4 weeks, respectively. The results showed that HD AOS–iron exerted a significant restorative effect by returning blood parameters to normal levels in rats with IDA, including hemoglobin, red blood cells, hematocrit, mean cell volume, mean cell hematocrit, mean cell hemoglobin concentration, serum iron, total iron binding capacity, transferrin saturation, and serum ferritin. A histological analysis suggested that the liver morphology in the MD and HD AOS–iron groups was similar to that in the normal group. Furthermore, MD and HD AOS–iron improved antioxidant activities in the serum and liver. In general, high-dose (the same dose as those of ferrous gluconate and FeSO₄) AOS–iron exhibited the best effects in terms of iron supplementation and antioxidant activities. The present findings showed that AOS–iron might be a potential new iron supplement.

Iron deficiency anemia (IDA) is one of the most serious nutritional problems.

Beneficial Effects of Marine Algae-Derived Carbohydrates for Skin Health

Marine algae are considered to be an abundant sources of bioactive compounds with cosmeceutical potential. Recently, a great deal of interest has focused on the health-promoting effects of marine bioactive compounds. Carbohydrates are the major and abundant constituent of marine algae and have been utilized in cosmetic formulations, as moisturizing and thickening agents for example. In addition, marine carbohydrates have been suggested as promising bioactive biomaterials for their various properties beneficial to skin, including antioxidant, anti-melanogenic and skin anti-aging properties. Therefore, marine algae carbohydrates have potential skin health benefits for value-added cosmeceutical applications. The present review focuses on the various biological capacities and potential skin health benefits of bioactive marine carbohydrates.

Coimmobilization of β-Agarase and α-Neoagarobiose Hydrolase for Enhancing the Production of 3,6-Anhydro-l-galactose

Here we report a simple and efficient method to produce 3,6-anhydro-l-galactose (l-AHG) and agarotriose (AO3) in one step by a multienzyme system with the coimmobilized β-agarase AgWH50B and α-neoagarobiose hydrolase K134D. K134D was obtained by AgaWH117 mutagenesis and showed improved thermal stability when immobilized via covalent bonds on functionalized magnetic nanoparticles. The obtained multienzyme biocatalyst was characterized by Fourier transform infrared spectroscopy (FTIR). Compared with free agarases, the coimmobilized agarases exhibited a relatively higher agarose-to-l-AHG conversion efficiency. The yield of l-AHG obtained with the coimmobilized agarases was 40.6%, which was 6.5% higher than that obtained with free agarases. After eight cycles, the multienzyme biocatalyst still preserved 46.4% of the initial activity. To the best of our knowledge, this is the first report where two different agarases were coimmobilized. These results demonstrated the feasibility of the new method to fabricate a new multienzyme system onto magnetic nanoparticles via covalent bonds to produce l-AHG.

Model-Based Complete Enzymatic Production of 3,6-Anhydro-l-galactose from Red Algal Biomass

3,6-Anhydro-l-galactose (l-AHG) is a bioactive constituent of agar polysaccharides. To be used as a cosmetic or pharmaceutical ingredient, l-AHG is more favorably prepared by enzymatic saccharification of agar using a combination of agarolytic enzymes. Determining the optimum enzyme combination from the natural repertoire is a bottleneck for designing an efficient enzymatic-hydrolysis process. We consider all theoretical enzymatic-saccharification routes in the natural agarolytic pathway of a marine bacterium, Saccharophagus degradans 2-40. Among these routes, three representative routes were determined by removing redundant enzymatic reactions. We simulated each l-AHG production route with simple kinetic models and validated the reaction feasibility with an experimental procedure. The optimal enzyme mixture (with 67.3% maximum saccharification yield) was composed of endotype β-agarase, exotype β-agarase, agarooligosaccharolytic β-galactosidase, and α-neoagarobiose hydrolase. This approach will reduce the time and effort needed for developing a coherent enzymatic process to produce l-AHG on a mass scale.