Alginates –A Seaweed product: Its Properties and Applications

Alginates are natural polysaccharides available as seaweed products. They possess several properties due to their molecular structure made of bipolymeric α-L-Guluronic acid and β-D-Mannuronic acid polymers. Alginates have several properties such as film-forming ability, pH responsiveness, and gelling, hydrophilicity, biocompatibility, biodegradability, non-toxic, processability and ionic crosslinking. They’re commonly used in several industries, including food, pharmaceuticals, dental applications, welding rods and scaffolding. Due to their gelling and non-toxic properties, as well as their abundance in nature, the cosmetics and healthcare industries have shown a great deal of interest in biodegradable polymers in general and alginates particularly over the last few decades.

The evaluation of safety property and apoptotic efficacy of α-L-Guluronic Acid (G2013), as a novel NSAID, under in vitro examination on L929 and hepatocellular carcinoma cell lines

Background: Many investigations have expanded this concept that liver chronic inflammation has an essential role in persistent cell damages along with altering the liver microenvironment leading to fibrosis, cirrhosis, and finally, hepatocellular carcinoma (HCC). To reduce inflammation and relieve symptoms, non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used; however, their long-term usage can lead to severe adverse events on vital organs like the liver. Interestingly, the α-L-Guluronic Acid (G2013), as a novel NSAID with immunomodulatory properties, has shown the inhibitory effects on inflammation and metastasis in experimental models. Objective: This study was conducted to determine the effects of G2013 on cytotoxicity and induction of apoptosis, as a new therapeutic target for cancer therapy, in the HepG2 cell line and the mouse fibroblast cell line L929, as a control. Methods: MTT assay and flow cytometry method were carried out using the different concentrations of G2013 (5, 15, 25, 50, 100, 200 and 400 μg/ml) in 3 distinct incubation times. Results: Our data showed that treatment of HepG2 cells with high concentration (400µg/mL) of G2013 could effectively cause a decrease in cell viability, so that they were statistically different after 72 hours compared to other concentrations (5 to 200 μg/ml) (P<0.05 and P<0.01, respectively). Moreover, the proportion of apoptosis of HepG2 cells at the dose of 200µg/mL considerably increased, suggesting that the induction of apoptosis by G2013 in HepG2 cells is dose- and time-dependent, which could promote its anticancer properties. Conclusion: The present study revealed that G2013 could induce apoptosis in the liver cancer model. Therefore, based on these findings, G2013 might be considered as a therapeutic option in cancer therapy.

Rheology and Water Absorption Properties of Alginate–Soy Protein Composites

Composite materials based on proteins and carbohydrates normally offer improved water solubility, biodegradability, and biocompatibility, which make them attractive for a wide range of applications. Soy protein isolate (SPI) has shown superabsorbent properties that are useful in fields such as agriculture. Alginate salts (ALG) are linear anionic polysaccharides obtained at a low cost from brown algae, displaying a good enough biocompatibility to be considered for medical applications. As alginates are quite hydrophilic, the exchange of ions from guluronic acid present in its molecular structure with divalent cations, particularly Ca2+, may induce its gelation, which would inhibit its solubilization in water. Both biopolymers SPI and ALG were used to produce composites through injection moulding using glycerol (Gly) as a plasticizer. Different biopolymer/plasticizer ratios were employed, and the SPI/ALG ratio within the biopolymer fraction was also varied. Furthermore, composites were immersed in different CaCl2 solutions to inhibit the amount of soluble matter loss and to enhance the mechanical properties of the resulting porous matrices. The main goal of the present work was the development and characterization of green porous matrices with inhibited solubility thanks to the gelation of alginate.

Expression and Characterization of a Cold-Adapted Alginate Lyase with Exo/Endo-Type Activity from a Novel Marine Bacterium Alteromonas portus HB161718T

The alginate lyases have unique advantages in the preparation of alginate oligosaccharides and processing of brown algae. Herein, a gene alg2951 encoding a PL7 family alginate lyase with exo/endo-type activity was cloned from a novel marine bacterium Alteromonas portus HB161718T and then expressed in Escherichia coli. The recombinant Alg2951 in the culture supernatant reached the activity of 63.6 U/mL, with a molecular weight of approximate 60 kDa. Alg2951 exhibited the maximum activity at 25 °C and pH 8.0, was relatively stable at temperatures lower than 30 °C, and showed a special preference to poly-guluronic acid (polyG) as well. Both NaCl and KCl had the most promotion effect on the enzyme activity of Alg2951 at 0.2 M, increasing by 21.6 and 19.1 times, respectively. The TCL (Thin Layer Chromatography) and ESI-MS (Electrospray Ionization Mass Spectrometry) analyses suggested that Alg2951 could catalyze the hydrolysis of sodium alginate to produce monosaccharides and trisaccharides. Furthermore, the enzymatic hydrolysates displayed good antioxidant activity by assays of the scavenging abilities towards radicals (hydroxyl and ABTS+) and the reducing power. Due to its cold-adapted and dual exo/endo-type properties, Alg2951 can be a potential enzymatic tool for industrial production.

Structural characterization of cocktail-like targeting polysaccharides from Ecklonia kurome Okam and their anti-SARS-CoV-2 activities invitro

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiological agent responsible for the worldwide coronavirus disease 2019 (COVID-19) outbreak. Investigation has confirmed that polysaccharide heparan sulfate can bind to the spike protein and block SARS-CoV-2 infection. Theoretically, similar structure of nature polysaccharides may also have the impact on the virus. Indeed, some marine polysaccharide has been reported to inhibit SARS-Cov-2 infection in vitro, however the convinced targets and mechanism are still vague. By high throughput screening to target 3CLpro enzyme, a key enzyme that plays a pivotal role in the viral replication and transcription using nature polysaccharides library, we discover the mixture polysaccharide 375 from seaweed Ecklonia kurome Okam completely block 3Clpro enzymatic activity (IC50, 0.48 µM). Further, the homogeneous polysaccharide 37502 from the 375 may bind to 3CLpro molecule well (kD value : 4.23 × 10−6). Very interestingly, 37502 also can potently disturb spike protein binding to ACE2 receptor (EC50, 2.01 µM). Importantly, polysaccharide 375 shows good anti-SARS-CoV-2 infection activity in cell culture with EC50 values of 27 nM (99.9% inhibiting rate at the concentration of 20 µg/mL), low toxicity (LD50: 136 mg/Kg on mice). By DEAE ion-exchange chromatography, 37501, 37502 and 37503 polysaccharides are purified from native 375. Bioactivity test show that 37501 and 37503 may impede SARS-Cov-2 infection and virus replication, however their individual impact on the virus is significantly less that of 375. Surprisingly, polysaccharide 37502 has no inhibition effect on SARS-Cov-2. The structure study based on monosaccharide composition, methylation, NMR spectrum analysis suggest that 375 contains guluronic acid, mannuronic acid, mannose, rhamnose, glucouronic acid, galacturonic acid, glucose, galactose, xylose and fucose with ratio of 1.86 : 9.56 : 6.81 : 1.69 : 1.00 : 1.75 : 1.19 : 11.06 : 4.31 : 23.06. However, polysaccharide 37502 is an aginate which composed of mannuronic acid (89.3 %) and guluronic acid (10.7 %), with the molecular weight (Mw) of 27.9 kDa. These results imply that mixture polysaccharides 375 works better than the individual polysaccharide on SARS-Cov-2 may be the cocktail-like polysaccharide synergistic function through targeting multiple key molecules implicated in the virus infection and replication. The results also suggest that 375 may be a potential drug candidate against SARS-CoV-2.

Functionalization of an Alginate-Based Material by Oxidation and Reductive Amination

This research focused on the synthesis of a functional alginate-based material via chemical modification processes with two steps: oxidation and reductive amination. In previous alginate functionalization with a target molecule such as cysteine, the starting material was purified and characterized by UV-Vis, 1H-NMR and HSQC. Additionally, the application of FT-IR techniques during each step of alginate functionalization was very useful, since new bands and spiked signals around the pyranose ring (1200–1000 cm−1) and anomeric region (1000–750 cm−1) region were identified by a second derivative. Additionally, the presence of C1-H1 of β-D-mannuronic acid residue as well as C1-H1 of α-L-guluronic acid residue was observed in the FT-IR spectra, including a band at 858 cm−1 with characteristics of the N-H moiety from cysteine. The possibility of attaching cysteine molecules to an alginate backbone by oxidation and post-reductive amination processes was confirmed through 13C-NMR in solid state; a new peak at 99.2 ppm was observed, owing to a hemiacetal group formed in oxidation alginate. Further, the peak at 31.2 ppm demonstrates the presence of carbon -CH2-SH in functionalized alginate—clear evidence that cysteine was successfully attached to the alginate backbone, with 185 μmol of thiol groups per gram polymer estimated in alginate-based material by UV-Visible. Finally, it was observed that guluronic acid residue of alginate are preferentially more affected than mannuronic acid residue in the functionalization.