Carrageenan of Red Algae Eucheuma gelatinae: Extraction, Antioxidant Activity, Rheology Characteristics, and Physicochemistry Characterization

Carrageenan is an anionic sulfated polysaccharide that accounts for a high content of red seaweed Eucheuma gelatinae. This paper focused on the extraction, optimization, and evaluation of antioxidant activity, rheology characteristics, and physic-chemistry characterization of β-carrageenan from Eucheuma gelatinae. The extraction and the optimization of β-carrageenan were by the maceration-stirred method and the experimental model of Box-Behken. Antioxidant activity was evaluated to be the total antioxidant activity and reducing power activity. The rheology characteristics of carrageenan were measured to be gel strength and viscosity. Physic-chemistry characterization was determined, including the molecular weight, sugar composition, function groups, and crystal structure, through GCP, GC-FID, FTIR, and XRD. The results showed that carrageenan possessed antioxidant activity, had intrinsic viscosity and gel strength, corresponding to 263.02 cps and 487.5 g/cm², respectively. Antioxidant carrageenan is composed of rhamnose, mannose, glucose, fucose, and xylose, with two molecular weight fractions of 2.635 × 10⁶ and 2.58 × 10⁶ g/mol, respectively. Antioxidant carrageenan did not exist in the crystal. The optimization condition of antioxidant carrageenan extraction was done at 82.35 °C for 115.35 min with a solvent-to-algae ratio of 36.42 (v/w). At the optimization condition, the extraction efficiency of carrageenan was predicted to be 87.56 ± 5.61 (%), the total antioxidant activity and reducing power activity were predicted to 71.95 ± 5.32 (mg ascorbic acid equivalent/g DW) and 89.84 ± 5.84 (mg FeSO₄ equivalent/g DW), respectively. Purity carrageenan content got the highest value at 42.68 ± 2.37 (%, DW). Antioxidant carrageenan from Eucheuma gelatinae is of potential use in food and pharmaceuticals.

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.

Seaweed Polysaccharide Based Products and Materials: An Assessment on Their Production from a Sustainability Point of View

Among the various natural polymers, polysaccharides are one of the oldest biopolymers present on the Earth. They play a very crucial role in the survival of both animals and plants. Due to the presence of hydroxyl functional groups in most of the polysaccharides, it is easy to prepare their chemical derivatives. Several polysaccharide derivatives are widely used in a number of industrial applications. The polysaccharides such as cellulose, starch, chitosan, etc., have several applications but due to some distinguished characteristic properties, seaweed polysaccharides are preferred in a number of applications. This review covers published literature on the seaweed polysaccharides, their origin, and extraction from seaweeds, application, and chemical modification. Derivatization of the polysaccharides to impart new functionalities by chemical modification such as esterification, amidation, amination, C-N bond formation, sulphation, acetylation, phosphorylation, and graft copolymerization is discussed. The suitability of extraction of seaweed polysaccharides such as agar, carrageenan, and alginate using ionic solvent systems from a sustainability point of view and future prospects for efficient extraction and functionalization of seaweed polysaccharides is also included in this review article.

Algae-Derived Bioactive Molecules for the Potential Treatment of SARS-CoV-2

The recently emerged COVID-19 disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has adversely affected the whole world. As a significant public health threat, it has spread worldwide. Scientists and global health experts are collaborating to find and execute speedy diagnostics, robust and highly effective vaccines, and therapeutic techniques to tackle COVID-19. The ocean is an immense source of biologically active molecules and/or compounds with antiviral-associated biopharmaceutical and immunostimulatory attributes. Some specific algae-derived molecules can be used to produce antibodies and vaccines to treat the COVID-19 disease. Algae have successfully synthesized several metabolites as natural defense compounds that enable them to survive under extreme environments. Several algae-derived bioactive molecules and/or compounds can be used against many diseases, including microbial and viral infections. Moreover, some algae species can also improve immunity and suppress human viral activity. Therefore, they may be recommended for use as a preventive remedy against COVID-19. Considering the above critiques and unique attributes, herein, we aimed to systematically assess algae-derived, biologically active molecules that could be used against this disease by looking at their natural sources, mechanisms of action, and prior pharmacological uses. This review also serves as a starting point for this research area to accelerate the establishment of anti-SARS-CoV-2 bioproducts.

Carrageenans as Broad-Spectrum Microbicides: Current Status and Challenges

Different kinds of red algae are enriched with chemically diverse carbohydrates. In particular, a group of sulfated polysaccharides, which were isolated from the cell walls of red algae, gained a large amount of attention due to their broad-spectrum antimicrobial activities. Within that group, carrageenans (CGs) were expected to be the first clinically applicable microbicides that could prevent various viral infections due to their superior antiviral potency and desirable safety profiles in subclinical studies. However, their anticipated beneficial effects could not be validated in human studies. To assess the value of a second attempt at pharmacologically developing CGs as a new class of preventive microbicides, all preclinical and clinical development processes of CG-based microbicides need to be thoroughly re-evaluated. In this review, the in vitro toxicities; in vivo safety profiles; and in vitro, ex vivo, and in vivo antiviral activities of CGs are summarized according to the study volume of their target viruses, which include human immunodeficiency virus, herpesviruses, respiratory viruses, human papillomavirus, dengue virus, and other viruses along with a description of their antiviral modes of action and development of antiviral resistance. This evaluation of the strengths and weaknesses of CGs will help provide future research directions that may lead to the successful development of CG-based antimicrobial prophylactics.

Inhibitory Effects of Carrageenans on Endotoxin-Induced Inflammation

The inhibitory effects of carrageenans (CRGs) on lipopolysaccharide (LPS) induced inflammation in a mouse model of endotoxemia and in complex therapy of patients with enteric infections of Salmonella etiology were studied. The atomic force microscopy (AFM) examination of LPS and its mixture with CRGs showed that the LPS morphology is significantly changed under the action of κ- and κ/β-CRGs. CRGs were able to increase the synthesis of anti-inflammatory interleukin 10 (IL-10) in vitro, and, at low concentrations, their activity in the mixture with LPS was higher. The protective effect of CRGs against Escherichia coli LPS was studied in vivo by monitoring the biochemical and pathomorphological parameters. The κ- and κ/β-CRGs and food supplement "Carrageenan-FE" increased the nonspecific resistance of mice to E. coli LPS at the expense of the inhibition of processes of thymus involution, adrenals hypertrophy, thyroid atrophy, hypercorticoidism, glycogenolysis, and lactate acidosis. The estimation of the therapeutic action of food supplement Carrageenan-FE in complex therapy of patients with enteric infections of Salmonella etiology is given. Carrageenan-FE restores the system of hemostasis and corrects some biochemical indicators and parameters in the immune systems of patients. These results allow us to hope for the practical application of CRGs for lowering the endotoxemia level in patients under the development of the infectious process caused by Gram-negative bacteria.

Carrageenans from the Red Seaweed Sarconema filiforme Attenuate Symptoms of Diet-Induced Metabolic Syndrome in Rats

Carrageenans are thickening and gelling agents that may provide health benefits. Iota (ι)-carrageenan, a linear sulfated polysaccharide, is produced by the red seaweed, Sarconema filiforme. This study investigated the potential of this seaweed as a functional food for the reversal of metabolic syndrome and possible mechanisms. Male Wistar rats were divided into four groups in a 16-week protocol: corn starch diet-fed rats (C); C rats supplemented with 5% S. filiforme for the last 8 weeks (CSF); high-carbohydrate, high-fat diet-fed rats (H); and H rats supplemented with 5% S. filiforme for the last 8 weeks (HSF). S. filiforme was produced in tank-based aquaculture yielding 27 g dry weight/day/m2 of culture area. H rats developed obesity, hypertension, dyslipidaemia, glucose intolerance, fatty liver and increased left ventricular collagen deposition. S. filiforme supplementation decreased body weight, abdominal and liver fat, systolic blood pressure, plasma total cholesterol concentrations, and plasma activities of alanine transaminase and aspartate transaminase. S. filiforme supplementation modulated gut microbiota without changing the Firmicutes to Bacteroidetes ratio. S. filiforme improved symptoms of high-carbohydrate, high-fat diet-induced metabolic syndrome in rats. Possible mechanisms include a reduced infiltration of inflammatory cells into organs as well as prebiotic actions in the gastrointestinal tract.

Integral Utilization of Red Seaweed for Bioactive Production

The hydrocolloids carrageenan and agar are the major fraction industrially extracted and commercialized from red seaweeds. However, this type of macroalgae also contains a variety of components with nutritional, functional and biological properties. In the context of sustainability and bioeconomy, where the integral utilization of the natural resources is incentivized, the sequential separation and valorization of seaweed components with biological properties of interest for food, nutraceuticals, cosmeceuticals and pharmaceuticals is proposed. In this work, a review of the available conventional and alternative greener and efficient extraction for obtaining red seaweed bioactives is presented. The potential of emerging technologies for the production of valuable oligomers from carrageenan and agar is also commented, and finally, the sequential extraction of the constituent fractions is discussed.

Evaluation of Prebiotic Potential of Three Marine Algae Oligosaccharides from Enzymatic Hydrolysis

Alginate oligosaccharides (AlgO), agarose oligosaccharides (AO), and κ-carrageenan oligosaccharides (KCO) were obtained by specific enzymatic hydrolysis method. The molecular weight distributions of the three oligosaccharides were 1.0⁻5.0 kDa, 0.4⁻1.4 kDa, and 1.0⁻7.0 kDa, respectively. The culture medium was supplemented with the three oligosaccharides and fermented by pig fecal microbiota in vitro, for 24 h. Each oligosaccharide was capable of increasing the concentration of short-chain fatty acids (SCFAs), especially butyric acid, and altering the microbiota composition. Linear discriminant analysis effect size (LEfSe) analysis results showed that the opportunistic pathogenic bacteria Escherichia, Shigella, and Peptoniphilus, were significantly decreased in AlgO supplemented medium. AO could improve the gut microbiota composition by enriching the abundance of Ruminococcaceae, Coprococcus, Roseburia, and Faecalibacterium. Besides, KCO could increase the abundance of SCFA microbial producers and opportunistic pathogenic flora. Therefore, these results indicate that AlgO and AO can be used as gut microbial regulators and can potentially improve animal/human gastrointestinal health and prevent gut disease, whereas the physiological function of KCO needs further evaluation.

Effects of Carrageenans on Biological Properties of Echinochrome

Sea urchin pigment echinochrome A (Ech), a water-insoluble compound, is the active substance in the cardioprotective and antioxidant drug Histochrome® (PIBOC FEB RAS, Moscow, Russia). It has been established that Ech dissolves in aqueous solutions of carrageenans (CRGs). Herein, we describe the effects of different types of CRGs on some properties of Ech. Our results showed that CRGs significantly decreased the spermotoxicity of Ech, against the sea urchin S. intermedius sperm. Ech, as well as its complex with CRG, did not affect the division and development of early embryos of the sea urchin. Ech reduced reactive oxygen species production (ROS) in neutrophils, caused by CRG. The obtained complexes of these substances with pro- and anti-activating ROS formation properties illustrate the possibility of modulating the ROS induction, using these compounds. The CRGs stimulate the induction of anti-inflammatory IL-10 synthesis, whereas Ech inhibits this synthesis and increases the production of the pro-inflammatory cytokines IL-6 and TNFα. The inclusion of Ech, in the complex with the CRGs, decreases Ech's ability to induce the expression of pro-inflammatory cytokines, especially TNFα, and increases the induction of anti-inflammatory cytokine IL-10. Thus, CRGs modify the action of Ech, by decreasing its pro-inflammatory effect. Whereas, the Ech's protective action towards human epithelial HT-29 cells remains to be unaltered in the complex, with κ/β-CRG, under stress conditions.

Ultrasound-assisted extraction and structural characterization by NMR of alginates and carrageenans from seaweeds

Polysaccharides from seaweeds are interesting materials for food and pharmaceutical applications such as drug delivery due to their biocompatibility and biodegradability. Extraction of these biopolymers is usually performed during several hours to obtain a significant extraction yield. In this paper, we report on a new process to extract alginates from brown seaweeds (Sargassum binderi and Turbinaria ornata) and carrageenans from red seaweeds (Kappaphycus alvarezii and Euchema denticulatum) with the assistance of ultrasound. The effect of several parameters (pH, temperature, algae/water ratio, ultrasound power and duration) was investigated to determine optimal extraction conditions. The extracted polysaccharides represented up to 55% of the seaweeds dry weight and were obtained in a short time (15-30min) as compared to 27% in 2h for conventional extraction. NMR, FTIR and SEC analysis were used to characterise the extracted polymers. Ultrasound allowed the reduction of extraction time without affecting the chemical structure and molar mass distribution of alginates and carrageenans.

New horizons in the extraction of bioactive compounds using deep eutectic solvents: A review

With the rapid development of ionic liquid analogues, termed 'deep eutectic solvents' (DESs), and their application in a wide range of chemical and biochemical processes in the past decade, the extraction of bioactive compounds has attracted significant interest. Recently, numerous studies have explored the extraction of bioactive compounds using DESs from diverse groups of natural sources, including animal and plant sources. This review summarizes the-state-of-the-art effort dedicated to the application of DESs in the extraction of bioactive compounds. The aim of this review also was to introduce conventional and recently-developed extraction techniques, with emphasis on the use of DESs as potential extractants for various bioactive compounds, such as phenolic acid, flavonoids, tanshinone, keratin, tocols, terpenoids, carrageenans, xanthones, isoflavones, α-mangostin, genistin, apigenin, and others. In the near future, DESs are expected to be used extensively for the extraction of bioactive compounds from various sources.

The Experimental Research (In Vitro) of Carrageenans and Fucoidans to Decrease Activity of Hantavirus

The effect of carrageenans and fucoidans on the activity of Hantavirus is studied. It has been found that among carrageenans a significant antiviral effect is exerted by the ι-type, which decreases the viral titer by 2.5 log focus forming units per mL; among fucoidans, by a preparation from Laminaria cichorioides, which reduces the number of infected cells from 27.0 to 5.3 after pretreatment of both the macrophage culture and Hantavirus. The antiviral effect of fucoidan from Laminaria japonica is shown to grow in direct proportion to the increase of dose of the preparation.

Sulfated Seaweed Polysaccharides as Multifunctional Materials in Drug Delivery Applications

In the last decades, the discovery of metabolites from marine resources showing biological activity has increased significantly. Among marine resources, seaweed is a valuable source of structurally diverse bioactive compounds. The cell walls of marine algae are rich in sulfated polysaccharides, including carrageenan in red algae, ulvan in green algae and fucoidan in brown algae. Sulfated polysaccharides have been increasingly studied over the years in the pharmaceutical field, given their potential usefulness in applications such as the design of drug delivery systems. The purpose of this review is to discuss potential applications of these polymers in drug delivery systems, with a focus on carrageenan, ulvan and fucoidan. General information regarding structure, extraction process and physicochemical properties is presented, along with a brief reference to reported biological activities. For each material, specific applications under the scope of drug delivery are described, addressing in privileged manner particulate carriers, as well as hydrogels and beads. A final section approaches the application of sulfated polysaccharides in targeted drug delivery, focusing with particular interest the capacity for macrophage targeting.

Seaweed hydrocolloid production: an update on enzyme assisted extraction and modification technologies

Agar, alginate, and carrageenans are high-value seaweed hydrocolloids, which are used as gelation and thickening agents in different food, pharmaceutical, and biotechnological applications. The annual global production of these hydrocolloids has recently reached 100,000 tons with a gross market value just above US$ 1.1 billion. The techno-functional properties of the seaweed polysaccharides depend strictly on their unique structural make-up, notably degree and position of sulfation and presence of anhydro-bridges. Classical extraction techniques include hot alkali treatments, but recent research has shown promising results with enzymes. Current methods mainly involve use of commercially available enzyme mixtures developed for terrestrial plant material processing. Application of seaweed polysaccharide targeted enzymes allows for selective extraction at mild conditions as well as tailor-made modifications of the hydrocolloids to obtain specific functionalities. This review provides an update of the detailed structural features of κ-, ι-, λ-carrageenans, agars, and alginate, and a thorough discussion of enzyme assisted extraction and processing techniques for these hydrocolloids.

Electrospray ionization mass spectrometric analysis of κ-carrageenan oligosaccharides obtained by degradation with κ-carrageenase from Pedobacter hainanensis

κ-Carrageenan was degraded with a novel κ-carrageenase isolated from Pedobacter hainanensis, which was first isolated from seaside soil under the stacks of red algae in Hainan province of China. The κ-carrageenase was detected with a molecular weight of ∼55 kDa estimated from SDS-PAGE and yielded enzymatic activity of 700.53 units/mg of protein under the conditions of pH 7.0 and 40 °C. Analysis of the degradation products by TLC and HPLC indicated that the enzyme degraded κ-carrageenan to sulfated oligosaccharides with even-numbered degree of polymerization, of which the tetrasaccharide was the major product. All the degradation components during different time courses were analyzed by ESI-MS, and their structures were assigned. Structural analysis by CID MS/MS revealed that each carrageenan oligosaccharide was composed of An-G4S-type neocarrabiose units, which consisted of a 3,6-anhydro-α-d-galactose (An) residue in the nonreducing end and a β-d-galactose-4-sulfate (G4S) residue in the reducing end. These results demonstrated that the κ-carrageenase cleaved κ-carrageenan at the internal β-1,4 linkage of κ-carrageenan. This enzymatic degradation offers an alternative approach to prepare κ-carrageenan oligosaccharides, which could be used as a powerful tool for further study on biological activity-structure relationship and thorough industrial exploitation of κ-carrageenan.

Characterization of a κ-carrageenase from marine Cellulophaga lytica strain N5-2 and analysis of its degradation products

A carrageenan-degrading marine Cellulophaga lytica strain N5-2 was isolated from the sediment of carrageenan production base. A κ-carrageenase (EC 3.2.1.83) with high activity was purified to electrophoretic homogeneity from the culture supernatant by a procedure of ammonium sulfate precipitation, dialyzing and gel filtration on SephadexG-200 and SephadexG-75. The purified enzyme was verified as a single protein on SDS-PAGE, and whose molecular weight was 40.8 kDa. The κ-carrageenase yielded a high activity of 1170 U/mg protein. For κ-carrageenase activity, the optimum temperature and pH were 35 °C and pH 7.0, respectively. The enzyme was stable at 40 °C for at least 2.5 h. The enzyme against κ-carrageenan gave a K_m value of 1.647 mg/mL and a V_max value of 8.7 μmol/min/mg when the reaction was carried out at 35 °C and pH 7.0. The degradation products of the κ-carrageenase were analyzed by thin layer chromatography (TLC), high performance liquid chromatography (HPLC), electrospray ionization time-of-flight mass spectroscopy (ESI-TOF-MS) and ¹³C-NMR spectroscopy, and the results indicated that the enzyme was specific of the β-1,4 linkage and hydrolyzed κ-carrageenan into κ-neocarraoctaose-sulfate and κ-neocarrahexaose-sulfate first, and then broke κ-neocarraoctaose-sulfate into κ-neocarrabiose-sulfate and κ-neocarrahexaose-sulfate.

Marine compounds with therapeutic potential in gram-negative sepsis

This paper concerns the potential use of compounds, including lipid A, chitosan, and carrageenan, from marine sources as agents for treating endotoxemic complications from Gram-negative infections, such as sepsis and endotoxic shock. Lipid A, which can be isolated from various species of marine bacteria, is a potential antagonist of bacterial endotoxins (lipopolysaccharide (LPSs)). Chitosan is a widespread marine polysaccharide that is derived from chitin, the major component of crustacean shells. The potential of chitosan as an LPS-binding and endotoxin-neutralizing agent is also examined in this paper, including a discussion on the generation of hydrophobic chitosan derivatives to increase the binding affinity of chitosan to LPS. In addition, the ability of carrageenan, which is the polysaccharide of red alga, to decrease the toxicity of LPS is discussed. We also review data obtained using animal models that demonstrate the potency of carrageenan and chitosan as antiendotoxin agents.

The antiviral activities and mechanisms of marine polysaccharides: an overview

Recently, the studies on the antiviral activities of marine natural products, especially marine polysaccharides, are attracting more and more attention all over the world. Marine-derived polysaccharides and their lower molecular weight oligosaccharide derivatives have been shown to possess a variety of antiviral activities. This paper will review the recent progress in research on the antiviral activities and the mechanisms of these polysaccharides obtained from marine organisms. In particular, it will provide an update on the antiviral actions of the sulfated polysaccharides derived from marine algae including carrageenans, alginates, and fucans, relating to their structure features and the structure-activity relationships. In addition, the recent findings on the different mechanisms of antiviral actions of marine polysaccharides and their potential for therapeutic application will also be summarized in detail.

Postharvest culture in the dark: An eco-friendly alternative to alkali treatment for enhancing the gel quality of kappa/iota-hybrid carrageenan from Chondrus crispus (Gigartinales, Rhodophyta)

After harvesting from natural stocks, female gametophytes of the red seaweed Chondrus crispus were cultured for several days under a light-deprived regime in order to determine if dark treatment can improve the gel quality of carrageenan extracted from the seaweed. An increase in the gel strength of native carrageenan was observed after dark treatment for 10d, but not after 5d, as compared to that of freshly harvested (baseline) seaweed. Corresponding decrease in sulfate and increase in 3,6-anhydrogalactose (3,6-AG) contents of the carrageenan extract were also observed. We posit that during dark treatment, the production of sulfated carrageenan precursor units was prevented while the enzymatic conversion of the prevailing precursor units to the gelation-promoting 3,6-AG was allowed to proceed. The observed increase in carrageenan gel strength with a 10-d dark treatment was comparable to the effect of the widely-used industrial procedure of alkali treatment in improving the extract's gel quality. Hence, postharvest culture in the dark for 10d can be an eco-friendly alternative to alkali treatment.

Matrix-assisted laser desorption/ionization mass spectrometric analysis of polysulfated-derived oligosaccharides using pyrenemethylguanidine

A better understanding of the biological roles of carbohydrates requires the use of tools able to provide efficient and rapid structural information. Unfortunately, highly acidic oligomers-such as polysulfated oligosaccharides-are very challenging to characterize because of their high polarity, structural diversity, and sulfate lability. These features pose special problems for matrix-assisted laser desorption/ionization mass spectrometric (MALDI-MS) analysis because polysulfated carbohydrates exhibit poor ionization efficiency and usually do not produce any signal. The present report demonstrates how MALDI-MS can be used to derive structural and compositional information from pure and mixed fractions of polysulfated oligosaccharides. Indeed, pyrenemethylguanidine (pmg, a derivatizing agent and ionization efficiency enhancer) was used for the analysis of di- to decasaccharides, carrying from two to nine sulfate groups. The method is applied to various highly sulfated chondroitin and carrageenan oligosaccharides as well as to the analysis of mixtures of compounds. In the mass spectra, the observation of a unique pmg-complexed ladder of peaks in both ionization modes allows an easy and rapid determination of both the number of sulfate groups carried by the analyte and its molecular weight. Moreover, we have developed a software tool for the rapid and automatic structural elucidation of carrageenans based on the mass spectra obtained.

Effect of genipin, a naturally occurring crosslinker on the properties of kappa-carrageenan

Genipin-fixed kappa-carrageenan was prepared in ambient conditions in aqueous solution using genipin, a naturally occurring crosslinker with kappa-carrageenan (kappaC). The crosslinked kappaC showed the greatest swelling capacity in acidic medium having pH 1.2 when compared to those in neutral and alkaline media. Enhanced stability of the crosslinked product with respect to the non-modified kappaC was confirmed by degradation studies in Ringer's solution, rheological and thermogravimetric measurements. Genipin fixation of kappaC was confirmed by measuring the bulk density, true density, pore volume, porosity, intrinsic viscosity, UV absorbance and optical rotation of the crosslinked kappaC, and as well as by optical microscopy, SEM, and MS/MS studies. The crosslinked product may be useful as super absorbent and sustained release formulation in biomedical applications.

Degradation of lambda-carrageenan by Pseudoalteromonas carrageenovora lambda-carrageenase: a new family of glycoside hydrolases unrelated to kappa- and iota-carrageenases

Carrageenans are sulfated galactans found in the cell walls of red seaweeds. They are classified according to the number and the position of sulfate ester groups. lambda-Carrageenan is the most sulfated carrageenan and carries at least three sulfates per disaccharide unit. The sole known depolymerizing enzyme of lambda-carrageenan, the lambda-carrageenase from Pseudoalteromonas carrageenovora, has been purified, cloned and sequenced. Sequence analyses have revealed that the lambda-carrageenase, referred to as CglA, is the first member of a new family of GHs (glycoside hydrolases), which is unrelated to families GH16, that contains kappa-carrageenases, and GH82, that contains iota-carrageenases. This large enzyme (105 kDa) features a low-complexity region, suggesting the presence of a linker connecting at least two independent modules. The N-terminal region is predicted to fold as a beta-propeller. The main degradation products have been purified and characterized as neo-lambda-carratetraose [DP (degree of polymerization) 4] and neo-lambda-carrahexaose (DP6), indicating that CglA hydrolyses the beta-(1-->4) linkage of lambda-carrageenan. LC-MALLS (liquid chromatography-multi-angle laser light scattering) and (1)H-NMR monitoring of the enzymatic degradation of lambda-carrageenan indicate that CglA proceeds according to an endolytic mode of action and a mechanism of inversion of the anomeric configuration. Using 2-aminoacridone-labelled neo-lambda-carrabiose oligosaccharides, in the present study we demonstrate that the active site of CglA comprises at least 8 subsites (-4 to +4) and that a DP6 oligosaccharide binds in the subsites -4 to +2 and can be hydrolysed into DP4 and DP2.

Effect of extraction parameters on the chemical structure and gel properties of κ/ι-hybrid carrageenans obtained from Mastocarpus stellatus

Extraction parameters (temperature, pH, duration) and alkaline pre-treatment duration have been systematically varied in the aim of exploring their impact on both chemical structure and gelling properties of carrageenan biopolymers obtained from Mastocarpus stellatus seaweeds, collected on the Northern coast of Portugal. Increasing the alkaline pre-treatment duration PT leads to kappa/iota-hybrid carrageenans containing less sulphate groups and biological precursor monomers. As a result, gel properties in the presence of KCl are improved as demonstrated by the increase in the Young's modulus with parameter PT. Increasing the extraction duration t ameliorates the biopolymer yield with no significant change in the complex kappa/iota-hybrid carrageenan chemical structure. However, smaller molecular weights are obtained and gel properties are seen to be negatively affected. Extraction temperature and pH have dramatic effects on the biopolymer gel strength, and a set of extraction parameters optimized with respect to extraction yield and gel properties is reported. In addition, kappa/iota-hybrid carrageenans obtained throughout this study exhibit a wide range of gel strengths in KCl, and allow us to present correlations between gel thermal properties and the kappa/iota-hybrid carrageenans chemical structure.

Antiviral activity of a carrageenan from Gigartina skottsbergii against intraperitoneal murine herpes simplex virus infection

The partially cyclized mu/nu-carrageenan 1C3, isolated from the red seaweed Gigartina skottsbergii, was previously shown to be a potent inhibitor of the in vitro replication of Herpes simplex virus types 1 (HSV-1) and 2 (HSV-2). Here the protective effect of 1C3 in a murine model of intraperitoneal ( i. p.) HSV-1 infection was evaluated. OF1 mice were i. p. infected with 5 x 10 (5) PFU of HSV-1 KOS strain, and the effects of different treatments with 1C3 were studied. When 30 mg/kg of body weight of 1C3 was administered by the i. p. route immediately after HSV-1 infection, 87.5 % survival of the animals was achieved (p < 0.005), associated with a delay in the mean day of death in 1C3-treated non-surviving mice. Animal survival was not improved when multiple doses of 1C3 were also given in the period 1 - 48 h post-infection, and no protection was afforded when treatment was started after 24 h of infection. When virus and compound were injected by different routes, i. p. and intravenous ( i. v.), respectively, a still significant protection was achieved (40 % survival, p < 0.05). No toxicity of 1C3 for the animals was recorded. The pharmacokinetic properties were analyzed after injection of 1C3 into the tail vein by monitoring of [ (3)H]-1C3 in plasma and organs and by a bioassay of the anti-HSV-1 activity remaining in serum after non-radioactive 1C3 inoculation. A very rapid disappearance of the compound from the blood was observed since only 5.9 - 0.9 % of the radioactivity of the initially administered [ (3)H]-1C3 appeared in the plasma between 5-300 minutes after administration. A transient peak of radioactivity was detected in the kidney 15 minutes after inoculation. The bioassay confirms the presence of the compound circulating in a biologically active form up to 1 hour after injection.

Effect of low molecular lambda-carrageenan from Chondrus ocellatus on antitumor H-22 activity of 5-Fu

Lambda-carrageenan is a kind of sulfated galactan isolated from some red algae and reported to have more biological activities than other types, such as K-type [Güven KC, özsoy Y, Ulutin ON. Anticoagulant, fibrinolytic and antiaggregant activity of carrageenans and alginic acid. Bot Mar 1991; 34: 429-432]. The molecular weight (MW) of lambda-carrageenan reaches up to 600-700 kDa, the high MW decreased their solubility and limited their bioactivities. At the same time, the production and applications of lambda-carrageenan are limited for its some characteristics, such as the high viscosity, and the experiments of antitumor and immunomodulation also indicated that MW of polysaccharides had notably effect on the activities [Zhou G, Sun YP, Xin H, Zhang Y, Li Z, Xu Z. In vivo antitumor and immunomodulation activities of different molecular weight lambda-carrageenans from Chondrus ocellatus. Pharmacol Res 2004; 50(1) 47-53, Zhou G, Xin H, Sheng W, Sun Y, Li Z, Xu Z. In vivo growth-inhibition of S180 tumor by mixture of 5-Fu and low molecular lambda-carrageenans from C. ocellatus. Pharmacol Res 2005; 51(2) 153-157]. In this research, lambda-carrageenan was extracted from C. ocellatus, an important economic alga in China. Then some small MW samples of 650, 240, 140, 15 and 9.3 kDa are obtained by the method of microwave degradation, respectively. The tumor inhibiting activities of the low MW lambda-carrageenan and mixture of it and 5-Fu on transplanted H-22 tumor mice were investigated. The weight of immune organ, proliferation ratio of lymphocyte and concentration of Tumor Necrosis Factor-alpha (TNF-alpha) and histopathology of tumor from transplanted H-22 tumor mice were also determined. The results indicated that the degraded lambda-carrageenan could add the antitumor activities of 5-Fu and improve the immunocompetence damaged by 5-Fu.

Comparative study of carrageenans from reproductive and sterile forms of Tichocarpus crinitus (Gmel.) Rupr (Rhodophyta, Tichocarpaceae)

A comparative study of the structure and properties of the sulfated polysaccharides (carrageenans) isolated from the vegetative and reproductive forms of the red alga Tichocarpus crinitus was performed. The polysaccharides were separated into the gelling (KCl-insoluble) and non-gelling (KCl-soluble) fractions by precipitation with 4% KCl. The total content of polysaccharides extracted from the reproductive form of the alga was 1.8-fold more than that extracted from the vegetative form, and in the first case, the gelling polysaccharides mostly accumulated. The gelling polysaccharides from the vegetative form have the highest molecular weight (354 kD). According to the results of FT-IR and 13C-NMR spectroscopy, the gelling polysaccharide fractions from both forms are kappa/beta carrageenans. The differences concern the content of the kappa- and beta-disaccharide units and the presence of a small content of the sulfated disaccharide segments (precursors of the kappa-carrageenans) in the polysaccharide from the reproductive form of the alga. The non-gelling polysaccharide fractions from both forms of the plant are mixtures of sulfated galactans with a low content of 3,6-anhydrogalactose.

Seaweed processing using industrial single-mode cavity microwave heating: a preliminary investigation

A single-cavity microwave heating system has been designed and fabricated for microwave-assisted extraction of carrageenans from seaweed. The system comprises a single mode (TE101) waveguide fitted with power and temperature controls, together with a continuous-flow-recycle reactor operating at atmospheric pressure. The system has been tested by extraction of E. cottonii and E. spinosum in aqueous organic solvents. Even without purification, the extraction products were found to have virtually identical FTIR and 13C and 1H NMR spectra to the reference samples of kappa- and iota-carrageenan, respectively. The principal advantages of the microwave system are substantial reduction of extraction time and low consumption of organic solvents.

In vivo growth-inhibition of S180 tumor by mixture of 5-Fu and low molecular lambda-carrageenan from Chondrus ocellatus

Lambda-carrageenan is a sulfated galactan isolated from some red algae and have been reported to have many kinds of biological activities. Chondrus ocellatus is an important economic alga in China and many other parts of the world. The sample was obtained after lambda-carrageenan from the alga was degraded by microwave and its molecular weight is 9.3 kDa. In this study, tumor inhibiting activity of low molecular weight lambda-carrageenan and its mixture with 5-Fu on mice transplanted with S180 tumor was investigated. Weight of immune organ, proliferation ratio of lymphocyte concentration of TNF-alpha and histopathology of spleen and tumor from the transplanted S180 tumor mice were also determined. Results indicated that the degraded lambda-carrageenan could enhance antitumor activity of 5-Fu and improve immunocompetence damaged by 5-Fu.

A nearly idealized 6′-O-methylated η-carrageenan from the Australian red alga Claviclonium ovatum (Acrotylaceae, Gigartinales)

The polysaccharides extracted from Claviclonium ovatum were studied by a combination of compositional assays, reductive partial hydrolysis, linkage analysis, Fourier Transform infrared (FTIR) spectroscopy, and 13C, 1H, and 13C/1H heteronuclear multiple quantum correlation (HMQC) two-dimensional nuclear magnetic resonance (NMR) spectroscopy. The chemical and spectroscopic data showed that the alkali-modified C. ovatum polysaccharides are composed of a nearly idealized repeating unit of 6'-O-methylcarrabiose 2,4'-disulfate (the repeating unit of 6'-O-methylated iota-carrageenan), although some minor components were also present. The C. ovatum galactans are the most highly methylated carrageenans reported.

Tensile and tear strength of carrageenan film from Philippine eucheuma species

The tensile and tear strength of carrageenan film from Philippines Eucheuma species were investigated using NEC tensilon universal-testing machine according to American Society for Testing Materials methods. These properties are important for assessing carrageenan film as packaging material. The kappa and iota types were used in the study. The effect of glycerine on the tensile and tear strength including elongation was also evaluated. Addition of glycerine tended to lower the tensile strength of the film and increase its elongation properties including the tear strength. Carrageenan film without glycerine was much stronger. Glycerine made the film more flexible and easy to deform. The composite film of carrageenan and konjac gum did not exhibit elongation. It also showed higher tensile strength than did the composite film of carrageenan and xanthan gum. Compared with iota-type carrageenan film, kappa-type carrageenan film without glycerine was more comparable to low-density polyethylene (LDPE) film in terms of tensile strength as was the composite film of carrageenan-konjac gum. The kappa-type carrageenan film with glycerine was more comparable to LDPE film in terms of tear strength. The elongation reading for carrageenan film was lower than that for LDPE film. Morphologic studies showed that the carrageenan film had sets of pores distributed randomly at different places as compared to LDPE film. It also showed that the carrageenan film was more fibrous than LDPE film.

Coil-helix transition of iota-carrageenan as a function of chain regularity

A series of iota-carrageenans containing different amounts of nu-carrageenan (0-23 monomer %) have been prepared from neutrally extracted carrageenan of Eucheuma denticulatum. nu-Carrageenan is the biochemical precursor of iota-carrageenan. The conformational order-disorder transition and rheological properties of these carrageenans were studied using optical rotation, rheometry, size exclusion chromatography coupled to multiangle laser light scattering, and high-sensitivity differential scanning calorimetry. The helix forming capacity of iota-carrageenan turns out to decrease monotonously with increasing amount of nu-units. In contrast, the rheological properties of iota-carrageenan are remarkably enhanced by the presence of a small amount of nu-units, yielding a maximum twofold increase in G' at 3% nu-units. It is concluded that the structure-forming capacity of iota-carrageenan, containing a small amount of nu-carrageenan, is significantly higher than that of pure iota-carrageenan. This phenomenon is explained in terms of the balance between the helical content and the number of cross-links between chains, taking into consideration the fact that nu-units introduce "kinks" in the chain conformation enabling neighboring chains to connect. Increasing amounts of nu-units increase the number of cross-links in the network, resulting in increased gel strength. On the other hand, a reduced length of the helical strands weakens the cross-links between the different chains and, consequently, the gel.

Isotropic-nematic phase equilibrium and phase separation of kappa-carrageenan in aqueous salt solution: experimental and theoretical approaches

The behavior of chiral-nematic and isotropic phases of helical kappa-carrageenan in aqueous solution of sodium iodide was compared with that of the anisotropic biphasic phase that contains both these phases. On the basis of birefringence, rheology, chemical analysis, average molecular weight, and polydispersity index measurements, we derived a number of characteristic differences as well as similarities between these phases, over a range of polysaccharide concentrations obtained by the dilution of each phase. For example, we assessed the critical concentration of an isotropic-anisotropic transition (C(i)), the temperature of the anisotropic-isotropic phase shift during thermal heating-cooling cycles, and the viscosity changes due to the phase shift and due to the diminishing of the helical conformation. We also demonstrated how the different phases and their dilutions behave under the effect of shear and frequency of oscillation and how the viscoelastic properties vary in each phase and discussed the isotropic and anisotropic liquid crystal controlling behavior mechanisms. From a theoretical point of view, we propose to combine the wormlike chain model for semiflexible polyelectrolytes interacting via both hard-core and electrostatic repulsion to assess the concentration of isotropic-nematic transition, to assess the coexistence concentration range, and to determine the effects of charge by applying the effective diameter and a twisting effect.

Structural studies on kappa-carrageenan derived oligosaccharides

Oligosaccharides were prepared through mild hydrochloric acid hydrolysis of kappa-carrageenan from Kappaphycus striatum carrageenan. Three oligosaccharides were purified by strong-anion exchange high-performance chromatography. Their structure was elucidated using mass spectral and NMR data. Negative-ion electrospray ionization (ESI) mass spectra at different fragmentor voltages provided the molecular weight of the compounds and unraveled the fragmentation pattern of the kappa-carrageenan oligosaccharides. 2D NMR techniques, including 1H-(1)H COSY, 1H-(1)H TOCSY and 13C-(1)H HMQC, were performed to determine the structure of a trisulfated pentasaccharide. 1D NMR and ESIMS were used to determine the structures of a kappa-carrageenan-derived pentasaccharide, heptasaccharide, and an undecasaccharide. All the oligosaccharides characterized have a 4-O-sulfo-D-galactopyranose residue at both the reducing and nonreducing ends.

Carrageenan gel and aberrant crypt foci in the colon of conventional and human flora-associated rats

Carrageenans (CAR) are sulfated polymers from seaweed used as gelling agents in foods. Chemical carcinogen induction of tumors in the colon of rats is enhanced by CAR. We speculated that gut microflora is involved in this effect. We thus studied the initiating and promoting effects of undegraded CAR-kappa (345,000 mol wt) in conventional rats and in germ-free rats associated with a human fecal flora. The initiating effect of CAR was studied by scoring aberrant crypt foci (ACF) in the colon of Fischer 344 rats given CAR (10% in water). The promoting effect of CAR was studied by comparing the multiplicity of ACF (number of crypts/focus) in rats receiving pure water or CAR (0.25% and 2.5% in water) for 100 days, starting 7 days after azoxymethane initiation (1 dose of 20 mg/kg i.p.). Duplicate studies were conducted in conventional rats and in human flora-associated rats maintained in isolators. Results show that CAR did not initiate ACF. In conventional rats, the 2.5% CAR gel promoted the growth of ACF: 2.98 +/- 0.29 and 3.44 +/- 0.48 crypts/ACF in control and treated rats, respectively (p < 0.02). The 0.25% CAR gel did not promote ACF. CAR can thus enhance intestinal tumors in this rat model, but only at a high dose level. In contrast, we did not observe any promoting effect of the administration of the 2.5% CAR gel in human flora-associated rats: 2.81 +/- 0.18 and 2.78 +/- 0.38 crypts/ACF in control and treated rats, respectively (p = 0.80). The specific microflora of rats, but not the human gut flora, might be involved in colon tumor enhancement by CAR.

Separation of iota-, kappa and lambda-carrageenans by capillary electrophoresis

The present study reports a novel method for the separation of the high-molecular-weight anionic polysaccharides, iota, kappa, and lambda carrageenans, in capillary electrophoresis (CE). Carrageenan samples are first derivatised with 9-aminopyrene-1,4,6-trisulfonic acid (APTS), separated in an ammonium acetate background electrolyte (BGE) and detected with laser-induced fluorescence (LIF). The effects of changes of instrumental parameters (temperature, injection mode, field strength) and the composition of the BGE (concentration and pH) are reported, and are explained in terms of the physical chemistry of the BGE and the biopolymers. Optimal separation conditions for kappa, iota, and lambda carrageenans, including an APTS internal standard, were found in a polyvinyl alcohol coated capillary with an ammonium acetate BGE of low concentration (25 mM) and moderate pH (8.0). This BGE gave the best reproducibility in tests on iota/kappa mixtures, with relative standard deviations (RSDs) in migration times and normalised peak areas (relative to the APTS internal standard) of less than 0.1% and 1%, respectively. Using this BGE at 50 degrees C and a voltage of 30 kV, all three carrageenan subtypes were separated in a run time of 3 min.

DL-Galactan hybrids and agarans from gametophytes of the red seaweed gymnogongrus torulosus

Seaweeds from the genus Gymnogongrus are known to be carrageenophytes; nevertheless, fractionation techniques used previously for the separation of gel-forming and 'soluble' carrageenans, applied to the galactans of Gymnogongrus torulosus together with enantiomeric analysis of the sugar components and (when possible) of the structural units, suggested that the system of galactans biosynthesized by the seaweed was formed by DL-galactan hybrids having major amounts of carrageenan-type or agaran-type chains, with minor quantities of agarans with unusual structural details.

Optimization of lambda-carrageenan as a chiral selector in capillary electrophoresis separations

Lambda-carrageenan, a linear high molecular weight sulfated polysaccharide, was employed as a chiral selector in capillary electrophoresis for the separation of enantiomers of weakly basic pharmaceutical compounds. In order to improve the utility of the chiral selector, the purity and concentration of the lambda-carrageenan and other important capillary electrophoresis method parameters were investigated. The results indicated that the purity and concentration of the lambda-carrageenan, ionic strength of the buffer, and temperature were critical to successful enantioseparation. These new method conditions were then applied to previously investigated beta-blockers (such as propranolol HCl and pindolol) and racemic tryptophan derivatives. These studies were successful in identifying important method conditions for the improved enantioselectivity with lambda-carrageenan.

The system of low-molecular-weight carrageenans and agaroids from the room-temperature-extracted fraction of Kappaphycus alvarezii

The room-temperature-extracted fraction from the red seaweed Kappaphycus alvarezii consists mainly of low-molecular-weight carrageenans, with structural dispersion around a basic kappa-pattern. This dispersion results from: (a) low percentages of 3,6-anhydrogalactose and the presence of precursor units; (b) important quantities of 6-O-methyl beta-D-galactose (4-sulfate) residues; (c) significant amounts of iota-repeating structure, and (d) small amounts of non-sulfated and disulfated beta-D-galactose residues. Significant quantities of alpha-L-galactose units suggest the presence of agaroids, as it has been reported in several other carrageenophytes.

Antiherpetic activity and mode of action of natural carrageenans of diverse structural types

The lambda-carrageenan 1T1, the kappa/iota-carrageenan 1C1 and the mu/nu-type 1C3, isolated from the red seaweed Gigartina skottsbergii, proved to be potent and selective inhibitors of herpes simplex virus (HSV) types 1 and 2. The antiviral IC50 values determined by virus yield inhibition assay in different cell lines ranged from 0.4 to 3.3 microg/ml, and no cytotoxic effects, measured by trypan blue exclusion on stationary or proliferating cells, tetrazolium salt method or cell protein synthesis, were observed. Time of addition and attachment studies suggested that the main target for antiviral action of the three carrageenans was virus adsorption, whereas no effect on virus internalization, or early or late protein synthesis was detected. However, the lambda-carrageenan 1T1 was still significantly inhibitory when added any time after adsorption. The pretreatment of virions with the carrageenans showed that 1C1 and 1C3 lacked direct inactivating effect at concentrations near the antiviral IC50 but 1T1 exerted virucidal action. The cyclization of 1T1 to afford the derivative 1T1T1 maintained the antiviral activity but eliminated the virucidal properties. Thus, the structure of 1T1 seems to be responsible for its differential behavior from 1C1 and 1C3, probably allowing a more stable binding to HSV, leading to virion inactivation. In contrast, 1C1 and 1C3 fail to bind with high affinity to virus alone, but are able to interfere with the interaction between HSV particles and the cell.

Antiherpetic and anticoagulant properties of carrageenans from the red seaweed Gigartina skottsbergii and their cyclized derivatives: correlation between structure and biological activity

The antiviral activity against herpes simplex virus types 1 and 2 of kappa/l-, partially cyclized mu/v-, and lambda-carrageenans isolated from the red seaweed Gigartina skottsbergii and their cyclized derivatives was analyzed. lambda-Carrageenans and the partially cyclized mu/v-carrageenan were the most potent inhibitors of herpes viruses (including acyclovir-resistant variants and clinical isolates), with IC50 values lower than 1 microgram ml-1 against both serotypes and selectivity indices higher than 10(3). kappa/l-Carrageenans were slightly less effective than the other two types with IC50 values in the range 1.6-4.1 micrograms ml-1. Antiherpetic activity was directly correlated to the amount of alpha-D-galactose 2,6-disulfate residues in the natural carrageenans. The cyclization of the alpha-D-galactose 6-sulfate and 2,6-disulfate units into 3,6-anhydro-alpha-D-galactose and 3,6-anhydro-alpha-D-galactose 2-sulfate residues in these polysaccharides, in general, lowers the antiherpetic activity of the derivatives with respect to the natural carrageenans. Some carrageenans showed a very reduced anticoagulant activity only at concentrations that were considerably higher than the IC50, whereas others were totally devoid of anticoagulant properties. Among natural carrageenans, the mu/v-type IC3 shows the best relationship between antiviral efficacy and lack of anticoagulant action, resulting a very promising compound.

Agarose-carrageenan hybrid polysaccharides from Lomentaria catenata

Two polysaccharide fractions, PS1 and PS2 from Lomentaria catenata consisted of D-Gal, L-Gal, D-Glc, D-Xyl, D-GlcA and sulphate. Partial hydrolysis led to the isolation and identification of oligosaccharides indicating the co-existence of an agarose and carrageenan backbone structure, in which D-Glc and D-GlcA residues occur as single units branching at O-3 of -->4)alpha-D-Gal(1--> and O-4 of -->3)beta-D-Gal(1-->, respectively.

Temperature and salt optimization of kappa-carrageenan fractionation by DEAE-cellulose

Carrageenans play an important role in many medical and food technology applications. However, the study of their properties has been hampered by a lack of well-defined samples (fractions). In this paper, a new principle is presented by which well-defined fractions can be obtained. It is based on batch adsorption to DEAE-cellulose combined with careful control of temperature and salt content. The parameters have been pre-optimized in an analytical column.

87Rb+ spin relaxation in enzymically purified and in untreated iota-carrageenan

The temperature dependences of the transverse (R2) and longitudinal (R1) n.m.r. relaxation rates of 87Rb+ in aqueous 5% iota-carrageenan have been compared with similar data for a sample purified by treatment with kappa-carrageenase. In each sample, the relaxation rates were sensitive to the conformation (helix or random coil). In the intact sample, the small (less than or equal to 5%) fraction of kappa-carrageenan (which, in its helical state, specifically binds rubidium ions) was solely responsible for the pronounced line-broadening that has been observed hitherto for 87Rb in iota-carrageenan gels. In the purified sample, the effects on the relaxation of 87Rb induced by iota-carrageenan are similar to those found in comparable systems in the absence of site-binding of the ions. Thus, there was a modest enhancement of the relaxation with R1 approximately R2 for the flexible coil conformation and a comparably larger effect, with significant contributions from dynamic processes on the time-scale of the inverse resonance frequency or longer, for the thicker, more highly charged and rigid helix conformation of iota-carrageenan.

Lymphocyte activation by purified carrageenan

The induction of polyclonal antibody production and mitogenic response by purified carrageenan was studied in vitro by using spleen cells. It was shown that kappa-CGN, lambda-CGN, and iota-CGN induced significant responses in mice, hamsters, and rats. The less purified CGN also exhibited the polyclonal antibody production in mice. In addition, purified CGN exhibited mitogenic action on B cells and to a lesser extent, on thymocytes. Polyclonal antibody responses induced by purified CGN were not affected by removal of T cells, adherent cells, or iron powder phagocytic cells. These results suggest that CGN may activate B cells resulting in polyclonal antibody responses.

IR studies on carrageenan of Ahnfeltia concinna, a marine red alga

The principal polysaccharide of Ahnfeltia concinna gave IR absorptions at 1240, 930, 845-850, and 805 cm-1, all typical of a carrageenan. The polysaccharide was separated into soluble and insoluble fractions with potassium chloride.