Disaccharides obtained from carrageenans as potential antitumor agents

Structural Insights into the Substrate Recognition and Catalytic Mechanism of a GH16 βκ-Carrageenase from Wenyingzhuangia fucanilytica

Understanding the substrate specificity of carrageenases has long been of interest in biotechnology applications. So far, the structural basis of the βκ-carrageenase that hydrolyzes furcellaran, a major hybrid carrageenan, remains unclear. Here, the crystal structure of Cgbk16A_Wf, as a representative of the βκ-carrageenase from GH16_13, was determined, and the structural characteristics of this subfamily were elucidated for the first time. The substrate binding mode was clarified through a structure analysis of the hexasaccharide-bound complex and molecular docking. The binding pocket involves a conserved catalytic motif and several specific residues associated with substrate recognition. Functions of residues R88, E290, and E184 were validated through site-directed mutagenesis. Comparing βκ-carrageenase with κ-carrageenase, we proposed that their different substrate specificities are partly due to the distinct conformations of subsite -1. This research offers a comprehensive understanding of the recognition mechanism of carrageenases and provides valuable theoretical support for enzyme modification and carrageenan oligosaccharide preparation.

Systematic review on carrageenolytic enzymes: From metabolic pathways to applications in biotechnology

Carrageenan, the major carbohydrate component of some red algae, is an important renewable bioresource with very large annual outputs. Different types of carrageenolytic enzymes in the carrageenan metabolic pathway are potentially valuable for the production of carrageenan oligosaccharides, biofuel, and other chemicals obtained from carrageenan. However, these enzymes are not well-developed for oligosaccharide or biofuel production. For further application, comprehensive knowledge of carrageenolytic enzymes is essential. Therefore, in this review, we first summarize various carrageenolytic enzymes, including the recently discovered β-carrageenase, carrageenan-specific sulfatase, exo-α-3,6-anhydro-D-galactosidase (D-ADAGase), and exo-β-galactosidase (BGase), and describe their enzymatic characteristics. Subsequently, the carrageenan metabolic pathways are systematically presented and applications of carrageenases and carrageenan oligosaccharides are illustrated with examples. Finally, this paper discusses critical aspects that can aid researchers in constructing cascade catalytic systems and engineered microorganisms to efficiently produce carrageenan oligosaccharides or other value-added chemicals through the degradation of carrageenan. Overall, this paper offers a comprehensive overview of carrageenolytic enzymes, providing valuable insights for further exploration and application of these enzymes.

Marine algae-derived characterized bioactive compounds as therapy for cancer: A review on their classification, mechanism of action, and future perspectives

In 2022, there were around 20 million new cases and over 9.7 million cancer-related deaths worldwide. An increasing number of metabolites with anticancer activity in algae had been isolated and identified, which were promising candidates for cancer therapy. Red algae are well-known for the production of brominated metabolites, including terpenoids and phenols, which have the capacity to induce cell toxicity. Some non-toxic biological macromolecules, including polysaccharides, are distinct secondary metabolites found in many algae, particularly green algae. They possess anticancer activities by inhibiting tumor angiogenesis, stimulating the immune response, and inducing apoptosis. However, the structure-activity relationship between these components and antitumor activity, as well as certain taxa within the algae, remains relatively unstudied. This work is based on the reports published from 2003 to 2024 in PubMed and ISI Web of Science databases. A comprehensive review of the characterized algal anticancer active compounds, together with their structure and mechanism of action was performed. Also, their structure-activity relationship was preliminarily summarized to better assess their potential properties as a natural, safe bioactive product to be used as an alternative for the treatment of cancers, leading to new opportunities for drug discovery.

Carrageenan in the Diet: Friend or Foe for Inflammatory Bowel Disease?

While the exact pathogenesis of IBD remains unclear, genetic, environmental and nutritional factors as well as the composition of the gut microbiome play crucial roles. Food additives, which are increasingly consumed in the Western diet, are being investigated for their potential effects on IBD. These additives can affect gut health by altering the composition of the microbiota, immune responses, and intestinal permeability, contributing to autoimmune diseases and inflammation. Despite the growing number of studies on food additives and IBD, the specific effects of carrageenan have not yet been sufficiently researched. This review addresses this gap by critically analyzing recent studies on the effects of carrageenan on the gut microbiota, intestinal permeability, and inflammatory processes. We searched the MEDLINE and SCOPUS databases using the following terms: carrageenan, carrageenan and inflammatory bowel disease, carrageenan and cancer, food additives and microbiome, food additives and intestinal permeability, and food additives and autoimmune diseases. In animal studies, degraded carrageenan has been shown to trigger intestinal ulceration and inflammation, highlighting its potential risk for exacerbating IBD. It can affect the gut microbiota, reduce bacterial diversity, and increase intestinal permeability, contributing to "leaky gut" syndrome. Some studies suggest that carrageenan may inhibit the growth of cancer cells by influencing the progression of the cell cycle, but the anti-cancer effect is still unclear. Carrageenan may also increase glucose intolerance and insulin resistance. Further research is needed to determine whether carrageenan should be excluded from the diet of individuals with IBD.

Therapeutic bacteria and viruses to combat cancer: double-edged sword in cancer therapy: new insights for future

Cancer, ranked as the second leading cause of mortality worldwide, leads to the death of approximately seven million people annually, establishing itself as one of the most significant health challenges globally. The discovery and identification of new anti-cancer drugs that kill or inactivate cancer cells without harming normal and healthy cells and reduce adverse effects on the immune system is a potential challenge in medicine and a fundamental goal in Many studies. Therapeutic bacteria and viruses have become a dual-faceted instrument in cancer therapy. They provide a promising avenue for cancer treatment, but at the same time, they also create significant obstacles and complications that contribute to cancer growth and development. This review article explores the role of bacteria and viruses in cancer treatment, examining their potential benefits and drawbacks. By amalgamating established knowledge and perspectives, this review offers an in-depth examination of the present research landscape within this domain and identifies avenues for future investigation.

Antioxidant and antiproliferative effect of a glycosaminoglycan extract from Rapana venosa marine snail

Marine glycosaminoglycans (GAG) isolated from different invertebrates, such as molluscs, starfish or jellyfish, have been described as unique molecules with important pharmacological applications. Scarce information is available on GAG extract from Rapana venosa marine snail. The aim of this study was to isolate a GAG extract from R. venosa marine snail and to investigate its physicochemical, antioxidant and antiproliferative properties for further biomedical use. The morphology, chemical and elemental composition of the extract were established as well as the sulfate content and N- to O-sulfation ratio. Fourier transform infrared (FTIR) spectra indicated that GAG extract presented similar structural characteristics to bovine heparan sulfate and chondroitin sulfate. The pattern of extract migration in agarose gel electrophoresis and specific digestion with chondroitinase ABC and heparinase III indicated the presence of a mixture of chondroitin sulfate-type GAG, as main component, and heparan sulfate-type GAG. Free radical scavenging and ferric ion reducing assays showed that GAG extract had high antioxidant activity, which slightly decreased after enzymatic treatment. In vitro MTT and Live/Dead assays showed that GAG extract had the ability to inhibit cell proliferation in human Hep-2 cell cultures, at cytocompatible concentrations in normal NCTC clone L929 fibroblasts. This capacity decreased after enzymatic digestion, in accordance to the antioxidant activity of the products. Tumoral cell migration was also inhibited by GAG extract and its digestion products. Overall, GAG extract from R. venosa marine snail exhibited antioxidant and antiproliferative activities, suggesting its potential use as novel bioactive compound for biomedical applications.

Sulfation of furcellaran and its effect on hemocompatibility in vitro

In this study, furcellaran (FUR) obtained from Furcellaria lumbricalis was firstly employed for sulfation via various methods, including SO3-pyridine (SO3∙Py) complex in different aprotic solvents, chlorosulfonic acid and sulfuric acid with a "coupling" reagent N,N'-Dicyclohexylcarbodiimide. Structural characterization through FT-IR, GPC, XPS and elemental analyses confirmed the successful synthesis of 6-O-sulfated FUR derivates characterized by varying degrees of sulfation (DS) ranging from 0.15 to 0.91 and molecular weight (Mw) spanning from12.5 kDa to 2.7 kDa. In vitro clotting assays, partial thromboplastin time (aPTT), thrombin time (TT), and prothrombin time (PT) underscored the essential role of sulfate esters in conferring anticoagulant activity whereas FUR prepared via chlorosulfonic acid with DS of 0.91 reached 311.4 s in aPPT showing almost 4-fold higher anticoagulant activity than native FUR at the concentration 2 mg/mL. MTT test showed all tested samples decreased cell viability in a dose dependent manner while all of them are non-cytotoxic up to the concentration of 0.1 mg/mL. Furthermore, sulfated derivates deposited onto polyethylene terephthalate surface presented substantial decrease in platelet adhesion, as well as absence of the most activated platelet stages. These findings support the pivotal role of O-6 FUR sulfates in enhancing hemocompatibility and provide valuable insights for a comparative assessment of effective sulfating approaches.

Enzymatically-derived oligo-carrageenans interact with α-Gal antibodies and Galectin-3

Carrageenans are linear sulfated galactans synthesized in the Gigartinales, Rhodophyceae species with a varied range of biological properties that are of value to the pharmaceutical and cosmetic sectors. It is unknown how the fine structure of carrageenans dictates their capacity to affect molecular and cellular responses important to wound healing, or the ability to mitigate oxidative, hemostatic and inflammatory processes. Here we use specific endo-carrageenases, from the marine bacterium Zobellia galactanivorans, to produce enzymatically defined neo-series oligosaccharides from carrageenans with 3,6-anhydro-D-galactose on the non-reducing end. Further enzymatic modification of the oligosaccharides was done by treating with the 3,6-anhydro-D-galactosidases from the same bacterium which hydrolyze non-reducing end 3,6-anhydro-D-galactose moieties from neo-carrageenan oligosaccharides. Using the enzymatically produced oligosaccharides, we demonstrate binding to natural human serum antibodies and a monoclonal anti-αGal Ab (m86). The significant interactions with the Galα(1,3)Gal reactive antibodies produced by humans makes them potential potent inducers of complement-dependent reactions and attractive for therapeutic applications. We also demonstrate modulation of the galectin selectivity for the Gal-3 Carbohydrate Recognition Domain (CRD) relative to Gal-1 which has implications to targeting specific biological pathways regulated by the galectins.

Enzymatic hydrolysates of κ-carrageenan by κ-carrageenase-CLEA immobilized on amine-modified ZIF-8 confer hypolipidemic activity in HepG2 cells

κ-Carrageenase can degrade κ-carrageenan to produce bioactive κ-carrageenan oligosaccharides (KCOs) that have potential applications in pharmaceutical, food, agricultural, and cosmetics industries. Immobilized enzymes gain their popularity due to their good reusability, enhanced stability, and tunability. In this study, the previously characterized catalytic domain of Pseudoalteromonas purpurea κ-carrageenase was covalently immobilized on the synthesized amine-modified zeolitic imidazolate framework-8 nanoparticles with the formation of cross-linked enzyme aggregates, and the immobilized κ-carrageenase was further characterized. The immobilized κ-carrageenase demonstrated excellent pH stability and good reusability, and exhibited higher optimal reaction temperature, better thermostability, and extended storage stability compared with the free enzyme. The KCOs produced by the immobilized κ-carrageenase could significantly decrease the TC, TG, and LDL-C levels in HepG2 cells, increase the HDL-C level in HepG2 cells, and reduce the free fatty acids level in Caco-2 cells. Biochemical assays showed that the KCOs could activate AMPK activity, increase the ratios of p-AMPK/AMPK and p-ACC/ACC, and downregulate the expression of the lipid metabolism related proteins including SREBP1 and HMGCR in the hyperlipidemic HepG2 cells. This study provides a novel and effective method for immobilization of κ-carrageenase, and the KCOs produced by the immobilized enzyme could be a potential therapeutic agent to prevent hyperlipidemia.

Expanding the application range of the κ‑carrageenase OUC-FaKC16A when preparing oligosaccharides from κ-carrageenan and furcellaran

Carrageenan oligosaccharides are important products that have demonstrated numerous bioactivities useful in the food, medicine, and cosmetics industries. However, the specific structure-function relationships of carrageenan oligosaccharides are not clearly described due to the deficiency of high specific carrageenases. Here, a truncated mutant OUC-FaKC16Q based on the reported κ-neocarratetrose (Nκ4)-producing κ-carrageenase OUC-FaKC16A from Flavobacterium algicola was constructed and further studied. After truncating the C-terminal Por_Secre_tail (PorS) domain (responsible for substrate binding), the catalytic efficiency and temperature stability decreased to a certain extent. Surprisingly, this truncation also enabled OUC-FaKC16Q to hydrolyze Nκ4 into κ-neocarrabiose (Nκ2). The offset of Arg265 residue in OUC-FaKC16Q may explain this change. Moreover, the high catalytic abilities, the main products, and the degradation modes of OUC-FaKC16A and OUC-FaKC16Q toward furcellaran were also demonstrated. Data suggested OUC-FaKC16A and OUC-FaKC16Q could hydrolyze furcellaran to produce mainly the desulfated oligosaccharides DA-G-(DA-G4S)2 and DA-G-DA-G4S, respectively. As a result, the spectrum of products of κ-carrageenase OUC-FaKC16A has been fully expanded in this study, indicating its promising potential for application in the biomanufacturing of carrageenan oligosaccharides with specific structures.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-023-00181-2.

A Screening Approach to Assess the Impact of Various Commercial Sources of Crude Marine λ-Carrageenan on the Production of Oligosaccharides with Anti-heparanase and Anti-migratory Activities

Oligosaccharides derived from λ-carrageenan (λ-COs) are gaining interest in the cancer field. They have been recently reported to regulate heparanase (HPSE) activity, a protumor enzyme involved in cancer cell migration and invasion, making them very promising molecules for new therapeutic applications. However, one of the specific features of commercial λ-carrageenan (λ-CAR) is that they are heterogeneous mixtures of different CAR families, and are named according to the thickening-purpose final-product viscosity which does not reflect the real composition. Consequently, this can limit their use in a clinical applications. To address this issue, six commercial λ-CARs were compared and differences in their physiochemical properties were analyzed and shown. Then, a H₂O₂-assisted depolymerization was applied to each commercial source, and number- and weight-averaged molar masses (M_n and M_w) and sulfation degree (DS) of the λ-COs produced over time were determined. By adjusting the depolymerization time for each product, almost comparable λ-CO formulations could be obtained in terms of molar masses and DS, which ranged within previously reported values suitable for antitumor properties. However, when the anti-HPSE activity of these new λ-COs was screened, small changes that could not be attributed only to their small length or DS changes between them were found, suggesting a role of other features, such as differences in the initial mixture composition. Further structural MS and NMR analysis revealed qualitative and semi-quantitative differences between the molecular species, especially in the proportion of the anti-HPSE λ-type, other CARs types and adjuvants, and it also showed that H₂O₂-based hydrolysis induced sugar degradation. Finally, when the effects of λ-COs were assessed in an in vitro migration cell-based model, they seemed more related to the proportion of other CAR types in the formulation than to their λ-type-dependent anti-HPSE activity.

Biochemical Characteristics and Potential Biomedical Applications of Hydrolyzed Carrageenans

Seaweed contains a variety of bioactive compounds; the most abundant of them are polysaccharides, which have significant biological and chemical importance. Although algal polysaccharides, especially the sulfated polysaccharides, have great potential in the pharmaceutical, medical and cosmeceutical sectors, the large molecular size often limits their industrial applications. The current study aims to determine the bioactivities of degraded red algal polysaccharides by several in vitro experiments. The molecular weight was determined by size-exclusion chromatography (SEC), and the structure was confirmed by FTIR and NMR. In comparison to the original furcellaran, the furcellaran with lower molecular weight had higher OH scavenging activities. The reduction in molecular weight of the sulfated polysaccharides resulted in a significant decrease in anticoagulant activities. Tyrosinase inhibition improved 2.5 times for hydrolyzed furcellaran. The alamarBlue assay was used to determine the effects of different Mw of furcellaran, κ-carrageenan and ι-carrageenan on the cell viability of RAW264.7, HDF and HaCaT cell lines. It was found that hydrolyzed κ-carrageenan and ι-carrageenan enhanced cell proliferation and improved wound healing, whereas hydrolyzed furcellaran did not affect cell proliferation in any of the cell lines. Nitric oxide (NO) production decreased sequentially as the Mw of the polysaccharides decreased, which indicates that hydrolyzed κ-Carrageenan, ι-carrageenan and furcellaran have the potential to treat inflammatory disease. These findings suggested that the bioactivities of polysaccharides were highly dependent on their Mw, and the hydrolyzed carrageenans could be used in new drug development as well as cosmeceutical applications.

The Antitumor Potential of λ-Carrageenan Oligosaccharides on Gastric Carcinoma by Immunomodulation

Gastric carcinoma is a frequently detected malignancy worldwide, while its mainstream drugs usually result in some adverse reactions, including immunosuppression. λ-carrageenan oligosaccharides (COS) have attracted increasing attention as potential anticancer agents due to their ability to enhance immune function. Our current work assessed the antitumor mechanism of λ-COS using BGC-823 cells. Our findings indicated that λ-COS alone did not have a significant impact on BGC-823 cells in vitro; however, it was effective in inhibiting tumor growth in vivo. When THP-1 cells were pre-incubated with λ-COS and used to condition the medium, BGC-823 cells in vitro displayed a concentration-dependent induction of cell apoptosis, nuclear damage, and the collapse of mitochondrial transmembrane potential. These findings suggested that the antineoplastic effect of λ-COS was primarily due to its immunoenhancement property. Treatment with λ-COS was found to significantly enhance the phagocytic capability of macrophages, increase the secretion of TNF-α and IFN-γ, and improve the indexes of spleen and thymus in BALB/c mice. In addition, λ-COS was found to inhibit the growth of BGC-823-derived tumors in vitro by activating the Par-4 signaling pathway, which may be stimulated by the combination of TNF-α and IFN-γ. When used in combination with 5-FU, λ-COS demonstrated enhanced anti-gastric carcinoma activity and improved the immunosuppression induced by 5-FU alone. These findings suggested that λ-COS could be used as an immune-modulating agent for chemotherapy.

Carrageenans and Their Oligosaccharides from Red Seaweeds Ahnfeltiopsis flabelliformis and Mastocarpus pacificus (Phyllophoraceae) and Their Antiproliferative Activity

Comparative structural analysis of gelling polysaccharides from A. flabelliformis and M. pacificus belonging to Phyllophoraceae and the effect of their structural features and molecular weight on human colon cancer cell lines (HT-29, DLD-1, HCT-116) was carried out. According to chemical analysis, IR and NMR spectroscopies, M. pacificus produces kappa/iota-carrageenan with a predominance of kappa units and minor amounts of mu and/or nu units, while the polysaccharide from A. flabelliformis is iota/kappa-carrageenan (predominance of iota units) and contains negligible amounts of beta- and nu-carrageenans. Iota/kappa- (Afg-OS) and kappa/iota-oligosaccharides (Mp-OS) were obtained from the original polysaccharides through mild acid hydrolysis. The content of more sulfated iota units in Afg-OS (iota/kappa 7:1) was higher than in Mp-OS (1.0:1.8). The poly- and oligosaccharides up to 1 mg/mL did not show a cytotoxic effect on all tested cell lines. Polysaccharides showed an antiproliferative effect only at 1 mg/mL. Oligosaccharides had a more pronounced effect on HT-29 and HCT-116 cells than the original polymers, while HCT-116 cells were slightly more sensitive to their action. Kappa/iota-oligosaccharides exhibit a greater antiproliferative effect and more strongly decrease the number of colonies forming in HCT-116 cells. At the same time, iota/kappa-oligosaccharides inhibit cell migration more strongly. Kappa/iota-oligosaccharides induce apoptosis in the SubG0 and G2/M phases, while iota/kappa-oligosaccharides in the SubG0 phase.

Sulfated polysaccharides as multi target molecules to fight COVID 19 and comorbidities

The majority of research to combat SARS-CoV-2 infection exploits the adaptive immune system, but innate immunity, the first line of defense against pathogenic microbes, is equally important in understanding and controlling infectious diseases. Various cellular mechanisms provide physiochemical barriers to microbe infection in mucosal membranes and epithelia, with extracellular polysaccharides, particularly sulfated polysaccharides, being among the most widespread and potent extracellular and secreted molecules blocking and deactivating bacteria, fungi, and viruses. New research reveals that a range of polysaccharides effectively inhibits COV-2 infection of mammalian cells in culture. This review provides an overview of sulfated polysaccharides nomenclature, its significance as immunomodulators, antioxidants, antitumors, anticoagulants, antibacterial, and as potent antivirals. It summarizes current research on various interactions of sulfated polysaccharide with a range of viruses, including SARS-CoV-2, and their application for potential treatments for COVID-19. These molecules interact with biochemical signaling in immune cell responses, by actions in oxidative reactions, cytokine signaling, receptor binding, and through antiviral and antibacterial toxicity. These properties provide the potential for the development of novel therapeutic treatments for SARS-CoV-2 and other infectious diseases from modified polysaccharides.

Recent advances in exploiting carrageenans as a versatile functional material for promising biomedical applications

Carrageenans are a group of biopolymers widely found in red seaweeds. Commercial carrageenans have been traditionally used as emulsifiers, stabilizers, and thickening and gelling agents in food products. Carrageenans are regarded as bioactive polysaccharides with disease-modifying and microbiota-modulating activities. Novel biomedical applications of carrageenans as biocompatible functional materials for fabricating hydrogels and nanostructures, including carbon dots, nanoparticles, and nanofibers, have been increasingly exploited. In this review, we describe the unique structural characteristics of carrageenans and their functional relevance. We summarize salient physicochemical features, including thixotropic and shear-thinning properties, of carrageenans. Recent results from clinical trials in which carrageenans were applied as both antiviral and antitumor agents and functional materials are discussed. We also highlight the most recent advances in the development of carrageenan-based targeted drug delivery systems with various pharmaceutical formulations. Promising applications of carrageenans as a bioink material for 3D printing in tissue engineering and regenerative medicine are systematically evaluated. We envisage some key hurdles and challenges in the commercialization of carrageenans as a versatile material for clinical practice. This comprehensive review of the intimate relationships among the structural features, unique rheological properties, and biofunctionality of carrageenans will provide novel insights into their biomedicine application potential.

Microwave-Assisted Extraction of Carrageenan from Sarcopeltis skottsbergii

The development of greener processes for the sustainable utilization of raw materials is increasingly demanded for environmental and economic reasons. A rapid and chemical-free technique was proposed for the extraction of hybrid kappa/iota (6/4) carrageenan from Sarcopeltis (ex Gigartina) skottsbergii. After separation, carrageenans were analyzed by Fourier transform infrared attenuated total reflectance, high-performance size-exclusion chromatography, and rheology. Maximum carrageenan extraction yields up to 63-64% were obtained operating at 110 or at 160 °C, for 5-7 min considering the sum of the heating and cooling periods, but the extraction of the phenolic fraction was favored at 220 °C. The recovered carrageenan showed apparent viscous values around 10³ mPa at the lowest tested shear rates (0.1 1/s) and could be suitable to formulate films. Furthermore, those carrageenans obtained under 140 °C showed gel characteristics without previous separation from the liquid extract, avoiding ethanolic precipitation and energy consumption. The antiradical properties correlated with the phenolic content in the liquid phase, but no influence of temperature on the reducing properties was observed. The microwave-assisted hydrothermal treatment could be an efficient tool without needing chemicals for the extraction of carrageenans, which showed adequate rheological properties for commercial uses.

Enzymatic Process for the Carrageenolytic Bioconversion of Sulfated Polygalactans into β-Neocarrabiose and 3,6-Anhydro-d-galactose

Oligosaccharides and anhydro-sugars derived from carrageenan have great potential as functional foods and drugs showing various bioactivities, including antioxidant, anti-inflammatory, antiviral, antitumor, and cytotoxic activities. Although preparation of sulfated carrageenan oligosaccharides by chemical and enzymatic processes has been widely reported, preparation of nonsulfated β-neocarrabiose (β-NC2) and the rare sugar 3,6-anhydro-d-galactose (d-AHG) was not reported in the literature. Based on the carrageenan catabolic pathway in marine heterotrophic bacteria, an enzymatic process was designed and constructed with recombinant κ-carrageenase, GH127/GH129 α-1,3 anhydrogalactosidase, and cell-free extract from marine carrageenolytic bacteria Colwellia echini A3^T. The process consisted of three successive steps, namely, (i) depolymerization, (ii) desulfation, and (iii) monomerization, by which carrageenan oligosaccharides, β-NC2, and d-AHG were obtained from κ-carrageenan. Unlike the chemical process, enzymatic hydrolysis yields oligosaccharides with the desired degree of polymerization facilitates specific removal of sulfated groups, free of toxic byproducts, and avoids chemical modifications. The final optimized enzymatic process produced 0.52 g of β-NC2 and 0.24 g of d-AHG from 1 g of κ-carrageenan. The carrageenolytic process designed for the enzymatic hydrolysis of κ-carrageenan can be scaled up for the mass production of bioactive carrageeno-oligosaccharides.

κ- and λ-Carrageenans from Marine Alga Chondrus armatus Exhibit Anticancer In Vitro Activity in Human Gastrointestinal Cancers Models

The carrageenans isolated from red algae demonstrated a variety of activities from antiviral and immunomodulatory to antitumor. The diverse structure and sulfation profile of carrageenans provide a great landscape for drug development. In this study, we isolated, purified and structurally characterized κo- and λo- oligosaccharides from the marine algae Chondrus armatus. We further examined the tumor suppressive activity of both carrageenans in gastrointestinal cancer models. Thus, using MTT assay, we could demonstrate a pronounced antiproliferative effect of the carrageenans in KYSE-30 and FLO-1 as well as HCT-116 and RKO cell lines with IC₅₀ 184~405 μg/mL, while both compounds were less active in non-cancer epithelial cells RPE-1. This effect was stipulated by the inhibition of cell cycle progression in the cancer cells. Specifically, flow cytometry revealed an S phase delay in FLO-1 and HCT-116 cells under κo-carrageenan treatment, while KYSE-30 demonstrated a pronounced G₂/M cell cycle delay. In line with this, western blotting revealed a reduction of cell cycle markers CDK2 and E2F2. Interestingly, κo-carrageenan inhibited cell cycle progression of RKO cells in G₁ phase. Finally, isolated κo- and λo- carrageenans induced apoptosis on adenocarcinomas, specifically with high apoptosis induction in RKO cells. Overall, our data underline the potential of κo- and λo- carrageenans for colon and esophageal carcinoma drug development.

The synergistic effect of physicochemical in vitro microenvironment modulators in human bone marrow stem cell cultures

Modern bioengineering utilises biomimetic cell culture approaches to control cell fate during in vitro expansion. In this spirit, herein we assessed the influence of bidirectional surface topography, substrate rigidity, collagen type I coating and macromolecular crowding (MMC) in human bone marrow stem cell cultures. In the absence of MMC, surface topography was a strong modulator of cell morphology. MMC significantly increased extracellular matrix deposition, albeit in a globular manner, independently of the surface topography, substrate rigidity and collagen type I coating. Collagen type I coating significantly increased cell metabolic activity and none of the assessed parameters affected cell viability. At day 14, in the absence of MMC, none of the assessed genes was affected by surface topography, substrate rigidity and collagen type I coating, whilst in the presence of MMC, in general, collagen type I α1 chain, tenascin C, osteonectin, bone sialoprotein, aggrecan, cartilage oligomeric protein and runt-related transcription factor were downregulated. Interestingly, in the presence of the MMC, the 1000 kPa grooved substrate without collagen type I coating upregulated aggrecan, cartilage oligomeric protein, scleraxis homolog A, tenomodulin and thrombospondin 4, indicative of tenogenic differentiation. This study further supports the notion for multifactorial bioengineering to control cell fate in culture.

Advances in anti-cancer effects and underlying mechanisms of marine algae polysaccharides

Cancer is a leading cause of death in both developing and developed countries. With the increase in the average global life expectancy, it has become a major health problem and burden for most public healthcare systems worldwide. Due to the fewer side effects of natural compounds than of chemotherapeutic drugs, increasing scientific attention is being focused on the development of anti-cancer drugs derived from natural sources. Marine algae are an interesting source of functional compounds with diverse health-promoting activities. Among these compounds, polysaccharides have attracted considerable interest for many years because of their excellent anti-cancer abilities. They improve the efficacy of conventional chemotherapeutic drugs with relatively low toxicity to normal human cells. However, there are few reviews summarising the unique anti-cancer effects and underlying mechanisms of marine algae polysaccharides (MAPs). Thus, the current review focuses on updating the advances in the discovery and evaluation of MAPs with anti-cancer properties and the elucidation of their mechanisms of action, including the signalling pathways involved. This review aims to provide a deeper understanding of the anti-cancer functions of the natural compounds derived from medicinal marine algae and thereby offer a new perspective on cancer prevention and therapy with high effectiveness and safety.

Marine Bioactive Compounds Derived from Macroalgae as New Potential Players in Drug Delivery Systems: A Review

The marine algal ecosystem is characterized by a rich ecological biodiversity and can be considered as an unexploited resource for the discovery and isolation of novel bioactive compounds. In recent years, marine macroalgae have begun to be explored for their valuable composition in bioactive compounds and opportunity to obtain different nutraceuticals. In comparison with their terrestrial counterparts, Black Sea macroalgae are potentially good sources of bioactive compounds with specific and unique biological activities, insufficiently used. Macroalgae present in different marine environments contain several biologically active metabolites, including polysaccharides, oligosaccharides, polyunsaturated fatty acids, sterols, proteins polyphenols, carotenoids, vitamins, and minerals. As a result, they have received huge interest given their promising potentialities in supporting antitumoral, antimicrobial, anti-inflammatory, immunomodulatory, antiangiogenic, antidiabetic, and neuroprotective properties. An additional advantage of ulvans, fucoidans and carrageenans is the biocompatibility and limited or no toxicity. This therapeutic potential is a great natural treasure to be exploited for the development of novel drug delivery systems in both preventive and therapeutic approaches. This overview aims to provide an insight into current knowledge focused on specific bioactive compounds, which represent each class of macroalgae e.g., ulvans, fucoidans and carrageenans, respectively, as valuable potential players in the development of innovative drug delivery systems.

Carrageenan From Kappaphycus alvarezii (Rhodophyta, Solieriaceae): Metabolism, Structure, Production, and Application

Carrageenan is a polysaccharide derived from red algae (seaweed) with enormous economic potential in a wide range of industries, including pharmaceuticals, food, cosmetics, printing, and textiles. Carrageenan is primarily produced through aquaculture-based seaweed farming, with Eucheuma and Kappaphycus species accounting for more than 90% of global output. There are three major types of carrageenan found in red algae: kappa (κ)-, iota (ι)-, and lambda (λ)-carrageenan. Kappaphycus alvarezii is the most common kappa-carrageenan source, and it is primarily farmed in Asian countries such as Indonesia, the Philippines, Vietnam, and Malaysia. Carrageenan extracted from K. alvarezii has recently received a lot of attention due to its economic potential in a wide range of applications. This review will discuss K. alvarezii carrageenan in terms of metabolic and physicochemical structure, extraction methods and factors affecting production yield, as well as current and future applications.

Beneficial effects of seaweed-derived dietary fiber: Highlights of the sulfated polysaccharides

Seaweeds and their derivatives are important bioresources of natural bioactive compounds. Nutritional studies indicate that dietary fibers derived from seaweeds have great beneficial potentials in human health and can be developed as functional food. Moreover, sulfated polysaccharides are more likely to be the main bioactive components which are widely distributed in various species of seaweeds including Phaeophyceae, Rhodophyceae and Chlorophyceae. The catabolism by gut microbiota of the seaweeds-derived dietary fibers (DFs) may be one of the pivotal pathways of their physiological functions. Therefore, in this review, we summarized the latest results of the physiological characteristics of seaweed-derived dietary fiber and highlighted the roles of sulfated polysaccharides in the potential regulatory mechanisms against disorders. Meanwhile, the effects of different types of seaweed-derived dietary fiber on gut microbiota were discussed. The analysis of the structure-function correlations and gut microbiota related mechanisms and will contribute to further better applications in food and biotherapeutics.

Chondrus crispus treated with ultrasound as a polysaccharides source with improved antitumoral potential

Ultrasound-assisted extraction was used to recover gelling biopolymers and antioxidant compounds from Chondrus crispus with improved biological potential. The optimal processing conditions were evaluated using a Box-Behnken design, and the impact on the biological and thermo-rheological properties of the carrageenan fraction and on the bioactive features of the soluble extracts were studied. The optimum extraction parameters were defined by extraction time of ~34.7 min; solid liquid ratio of ~2.1 g/100 g and ultrasound amplitude of ~79.0% with a maximum power of 1130 W. The dependent variables exhibited maximum carrageenan yields (44.3%) and viscoelastic modulus (925.9 Pa) with the lowest gelling temperatures (38.7 °C) as well as maximum content of the extract in protein (22.4 mg/g), gallic acid (13.4 mg/g) and Trolox equivalents antioxidant capacity (182.4 mg TEAC/g). Tested hybrid carrageenans exhibited promising biological activities (% of growth inhibition around 91% for four human cancer cellular lines: A549; A2780; HeLa 229; HT-29).

Ambroxol Hydrochloride Loaded Gastro-Retentive Nanosuspension Gels Potentiate Anticancer Activity in Lung Cancer (A549) Cells

This study aimed to develop gastro-retentive sustained-release ambroxol (ABX) nanosuspensions utilizing ambroxol-kappa-carrageenan (ABX-CRG_K) complexation formulations. The complex was characterized by differential scanning calorimetry, powder x-ray diffractometer, and scanning electron microscopy. The prepared co-precipitate complex was used for the development of the sustained-release formulation to overcome the high metabolic and poor solubility problems associated with ABX. Furthermore, the co-precipitate complex was formulated as a suspension in an aqueous floating gel-forming vehicle of sodium alginate with chitosan, which might be beneficial for targeting the stomach as a good absorption site for ABX. The suspension exhibited rapid floating gel behaviour for more than 8 h, thus confirming the gastro-retentive effects. Particle size analysis revealed that the optimum nanosuspension (ABX-NS) had a mean particle size of 332.3 nm. Afterward, the ABX released by the nanoparticles would be distributed to the pulmonary tissue as previously described. Based on extensive pulmonary distribution, the developed nanosuspension-released ABX nanoparticles showed significant cytotoxic enhancement compared to free ABX in A549 lung cancer cells. However, a significant loss of mitochondrial membrane potential (MMP) also occurred. The level of caspase-3 was the highest in the ABX-NS-released particle-treated samples, with a value of 416.6 ± 9.11 pg/mL. Meanwhile, the levels of nuclear factor kappa beta, interleukins 6 and 1 beta, and tumour necrosis alpha (NF-kB, IL-6, IL-1β, and TNF-α, respectively) were lower for ABX-NS compared to free ABX (p < 0.05). In caspase-3, Bax, and p53, levels significantly increased in the presence of ABX-NS compared to free ABX. Overall, ABX-NS produced an enhancement of the anticancer effects of ABX on the A549 cells, and the developed sustained-release gel was successful in providing a gastro-retentive effect.

A Marine λ-Oligocarrageenan Inhibits Migratory and Invasive Ability of MDA-MB-231 Human Breast Cancer Cells through Actions on Heparanase Metabolism and MMP-14/MMP-2 Axis

Sugar-based molecules such as heparins or natural heparan sulfate polysaccharides have been developed and widely studied for controlling heparanase (HPSE) enzymatic activity, a key player in extracellular matrix remodelling during cancer pathogenesis. However, non-enzymatic functions of HPSE have also been described in tumour mechanisms. Given their versatile properties, we hypothesized that sugar-based inhibitors may interfere with enzymatic but also non-enzymatic HPSE activities. In this work, we assessed the effects of an original marine λ-carrageenan derived oligosaccharide (λ-CO) we previously described, along with those of its native counterpart and heparins, on cell viability, proliferation, migration, and invasion of MDA-MB-231 breast cancer cells but also of sh-MDA-MB-231 cells, in which the expression of HPSE was selectively downregulated. We observed no cytotoxic and no anti-proliferative effects of our compounds but surprisingly λ-CO was the most efficient to reduce cell migration and invasion compared with heparins, and in a HPSE-dependent manner. We provided evidence that λ-CO tightly controlled a HPSE/MMP-14/MMP-2 axis, leading to reduced MMP-2 activity. Altogether, this study highlights λ-CO as a potent HPSE “modulator” capable of reducing not only the enzymatic activity of HPSE but also the functions controlled by the HPSE levels.

Food-grade carrageenans and their implications in health and disease

Food additives, often used to guarantee the texture, shelf-life, taste, and appearance of processed foods, have gained widespread attention due to their increased link to the growing incidence of chronic diseases. As one of the most common additives, carrageenans have been used in human diets for hundreds of years. While classified as generally recognized as safe (GRAS) for human consumption, numerous studies since the 1980s have suggested that carrageenans, particularly those with random coil conformations, may have adverse effects on gastrointestinal health, including aggravating intestinal inflammation. While these studies have provided some evidence of adverse effects, the topic is still controversial. Some have suggested that the negative consequence of the consumption of carrageenans may be structure dependent. Furthermore, pre-existing conditions may predispose individuals to varied outcomes of carrageenan intake. In this review, structure-function relationships of various carrageenans in the context of food safety are discussed. We reviewed the molecular mechanisms by which carrageenans exert their biological effects. We summarized the findings associated with carrageenan intake in animal models and clinical trials. Moreover, we examined the interactions between carrageenans and the gut microbiome in the pathogenesis of gastrointestinal disorders. This review argues for personalized guidance on carrageenan intake based on individuals' health status. Future research efforts that aim to close the knowledge gap on the effect of low-dose and chronic carrageenan intake as well as interactions among food additives should be conducive to the improved safety profile of carrageenans in processed food products.

Ultrasound-Assisted Water Extraction of Mastocarpus stellatus Carrageenan with Adequate Mechanical and Antiproliferative Properties

Ultrasound-assisted water extraction was optimized to recover gelling biopolymers and antioxidant compounds from Mastocarpus stellatus. A set of experiments following a Box–Behnken design was proposed to study the influence of extraction time, solid liquid ratio, and ultrasound amplitude on the yield, sulfate content, and thermo-rheological properties (viscoelasticity and gelling temperature) of the carrageenan fraction, as well as the composition (protein and phenolic content) and antiradical capacity of the soluble extracts. Operating at 80 °C and 80 kHz, the models predicted a compromise optimum extraction conditions at ~35 min, solid liquid ratio of ~2 g/100 g, and ultrasound amplitude of ~79%. Under these conditions, 40.3% carrageenan yield was attained and this product presented 46% sulfate and good mechanical properties, a viscoelastic modulus of 741.4 Pa, with the lowest gelling temperatures of 39.4 °C. The carrageenans also exhibited promising antiproliferative properties on selected human cancer cellular lines, A-549, A-2780, HeLa 229, and HT-29 with EC₅₀ under 51.9 μg/mL. The dried soluble extract contained 20.4 mg protein/g, 11.3 mg gallic acid eq/g, and the antiradical potency was equivalent to 59 mg Trolox/g.

Metabolic profiling of cytotoxic metabolites from five Tabebuia species supported by molecular correlation analysis

Tabebuia is the largest genus among the family Bignoniaceae. Tabebuia species are known for their high ornamental and curative value. Here, the cytotoxic potential of extracts from the leaves and stems of five Tabebuia species was analyzed. The highest activity was observed for T. rosea (Bertol.) DC. stem extract against HepG2 cell line (IC₅₀ 4.7 µg/mL), T. pallida L. stem extract against MCF-7 cell line (IC₅₀ 6.3 µg/mL), and T. pulcherrima stem extract against CACO2 cell line (IC₅₀ 2.6 µg/mL). Metabolic profiling of the ten extracts using liquid chromatography–high-resolution mass spectrometry for dereplication purposes led to annotation of forty compounds belonging to different chemical classes. Among the annotated compounds, irridoids represent the major class. Principle component analysis (PCA) was applied to test the similarity and variability among the tested species and the score plot showed similar chemical profiling between the leaves and stems of both T. pulcherrima and T. pallida L. and unique chemical profiling among T. rosea (Bertol.) DC., T. argentea Britton, and T. guayacan (Seem.) Hemsl. leaf extracts and the stem extract of T. rosea (Bertol.) DC. Additionally, a molecular correlation analysis was used to annotate the bioactive cytotoxic metabolites in the extracts and correlate between their chemical and biological profiles.

Expression and Characterization of a Thermostable Carrageenase From an Antarctic Polaribacter sp. NJDZ03 Strain

The complete genome of Polaribacter sp. NJDZ03, which was isolated from the surface of Antarctic macroalgae, was analyzed by next-generation sequencing, and a putative carrageenase gene Car3206 was obtained. Car3206 was cloned and expressed in Escherichia coli BL21(DE3). After purification by Ni-NTA chromatography, the recombinant Car3206 protein was characterized and the antioxidant activity of the degraded product was investigated. The results showed that the recombinant plasmid pet-30a-car3206 was highly efficiently expressed in E. coli BL21(DE3). The purified recombinant Car3206 showed a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, with an apparent molecular weight of 45 kDa. The optimum temperature of the recombinant Car3206 was 55°C, and it maintain 60-94% of its initial activity for 4-12 h at 55°C. It also kept almost 70% of the initial activity at 30°C, and more than 40% of the initial activity at 10°C. These results show that recombinant Car3206 had good low temperature resistance and thermal stability properties. The optimum pH of recombinant Car3206 was 7.0. Car3206 was activated by Na+, K+, and Ca2+, but was significantly inhibited by Cu2+ and Cr2+. Thin-layer chromatographic analysis indicated that Car3206 degraded carrageenan generating disaccharides as the only products. The antioxidant capacity of the degraded disaccharides in vitro was investigated and the results showed that different concentrations of the disaccharides had similar scavenging effects as vitamin C on O 2 • - , •OH, and DPPH•. To our knowledge, this is the first report about details of the biochemical characteristics of a carrageenase isolated from an Antarctic Polaribacter strain. The unique characteristics of Car3206, including its low temperature resistance, thermal stability, and product unity, suggest that this enzyme may be an interesting candidate for industrial processes.

Semi-synthesis of N-alkyl-kappa-carrageenan derivatives and evaluation of their antibacterial activity

In this article, we describe the semi-synthesis of N-alkyl-kappa-carrageenan derivatives and their antibacterial activity against Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC 8739), and Pseudomonas aeruginosa (ATCC 9027). Kappa-carrageenan was submitted to partial acid hydrolysis promoting the selective cleavage of α-glycosidic bonds involving 3,6-anhydro-α-D-Galp units, giving rise to reducing low-molecular weight polysaccharide fragments, which were reacted with alkylamines of varying chain lengths by reductive amination. The carrageenan derivatives were characterized by HPSEC-MALLS-RID and 1D and 2D ¹H and ¹³C NMR spectroscopy. The antibacterial activity of N-alkyl-kappa-carrageenan derivatives was compared with N-alkyl-(1-deoxylactitol-1-yl)-amines using a microdilution test, which indicated that inhibitory activity was dependent on the degree of substitution by hydrophobic groups at the polysaccharide structure. Comparing the effect of different N-alkyl chains, those with longer chains showed higher activity.

Carrageenan: Drug Delivery Systems and Other Biomedical Applications

Marine resources are today a renewable source of various compounds, such as polysaccharides, that are used in the pharmaceutical, medical, cosmetic, and food fields. In recent years, considerable attention has been focused on carrageenan-based biomaterials due to their multifunctional qualities, including biodegradability, biocompatibility, and non-toxicity, in addition to bioactive attributes, such as their antiviral, antibacterial, antihyperlipidemic, anticoagulant, antioxidant, antitumor, and immunomodulating properties. They have been applied in pharmaceutical formulations as both their bioactive and physicochemical properties make them suitable biomaterials for drug delivery, and recently for the development of tissue engineering. This article provides a review of recent research on the various types of carrageenan-based biomedical and pharmaceutical applications.

Macroalgal dietary glycans: potential source for human gut bacteria and enhancing immune system for better health

Macroalgae are the diverse group of photosynthetic algae found at the intertidal regions of oceans. Recent advances suggest that macroalgal derived glycans have tremendous potential to maintain gut microbiome and immune system. The human gut bacteria harbor unique arsenals for utilizing a variety of macroalgal glycans, and produce a variety of oligosaccharides in vivo. Those oligosaccharides interact with immune cell receptors, and also are available for microbial fermentation, thus play magnificent roles in balancing the gut homeostasis. However, this area of research is still in infancy condition in term to understand their molecular interactions. For wooing this area, we urge to emphasize more studies on mechanistic level sympathetic of depolymerizing marine dietary glycans by gut bacteria and elucidating molecular aspect of glycans to cell receptors interactions. This will invent new nutraceutical strategies to purposefully manipulate the microbial composition to improve health. Therefore, review focuses on the recent development of mechanistic understanding of human gut bacterial communities for utilizing macroalgal derived glycans. Recent trends of application of glycans in modulating immune system at mechanistic level and their available evidences are discussed.

Complete genome sequence of Bacillus sp. N1-1, a κ-selenocarrageenan degrading bacterium isolated from the cold seep in the South China Sea

κ-Selenocarrageenan is made from natural κ-carrageenan, in which Se partially replaces Sulfur (S). The underlying mechanism of κ-selenocarrageenan degradation remain unreported so far. Here, we describe the complete genome of a cold seep bacterium, Bacillus sp. N1-1, which can degrade κ-selenocarrageenan. The strain has a circular genome of 4,497,340 bp and 40.48 mol% G + C content, consisting of 4272 protein-coding sequences (CDSs), 87 tRNAs, as well as 28 rRNA operons as 5S-16S-23S rRNA. N1-1 genome contains several protein-coding genes relating to polysaccharide degradation and the potential of this bacterium to produce enzymes for the hydrolysis of κ-selenocarrageenan on the basis of complete genome analysis could be discovered.

Antitumour Potential of Gigartina pistillata Carrageenans against Colorectal Cancer Stem Cell-Enriched Tumourspheres

Gigartina pistillata is a red seaweed common in Figueira da Foz, Portugal. Here, the antitumour potential of G. pistillata carrageenan, with a known variable of the life cycle, the female gametophyte (FG) and tetrasporophyte (T) was evaluated against colorectal cancer stem cell (CSC) -enriched tumourspheres. FTIR-ATR analysis of G. pistillata carrageenan extracts indicated differences between life cycle phases, being FG a κ/ι hybrid carrageenan and T a ʎ/ξ hybrid. Both carrageenan extracts presented IC50 values inferior to 1 μg/mL in HT29-derived CSC-enriched tumourspheres, as well as reduced tumoursphere area. The two extracts were also effective at reducing cellular viability in SW620- and SW480-derived tumourspheres. These results indicate that carrageenans extracted from two G. pistillata life cycle phases have antitumour potential against colorectal cancer stem-like cells, specially the T carrageenan.