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Porphyrins have exquisite photophysical and electronic properties that enable their use in photodynamic therapy. Even though the thermodynamic behavior relates to the aforementioned properties, the thermal degradation of non-mesomorphic porphyrins behavior has been little explored. Here, we demonstrated the thermoanalytical profiles of common porphyrins, using differential scanning calorimetry (DSC) and thermogravimetric analysis (TG/DTG). The thermal behavior was also evaluated from the perspective of molecular modeling and energy minimization. In our series, porphyrins embedding pyridyl, amino-phenyl, and nitro-phenyl moieties, that confer different physicochemical and electronic properties to the macrocycle, were studied. Tetrapyridylporphyrin presents symmetric and parallel lowest unoccupied molecular orbitals (LUMOs) and was the most thermostable compound (DTGpeak = 473.26 °C), while β-nitrotetraphenylporphyrin presents LUMOs drastically shifted toward the electron-withdrawing group –NO2 group and was the least stable upon heating (DTGpeak1 = 357.16 °C). DSC profiles showed phase change/crystalline transitions and endothermic degradation events for phenyl-, aminophenyl- and pyridyl-containing porphyrins, whereas nitro-porphyrins exhibited a high energetic exothermic degradation event (p-nitrophenyl-triphenylporphyrin: Tpeak = 406.84 °C, ∆H = 147.28 J g−1; β-nitro-tetraphenyl-porphyrin Tpeak = 375.25 °C, ∆H = 849.52 J g−1).

Microalgae have been shown to be useful in several biotechnological fields due to their feasible cultivation and high-value biomolecules production. Several substances of interest produced by microalgae, such as: proteins, lipids, and natural colorants, have already been explored. Based on the continuing demand for new natural molecules, microalgae could also be a valuable source of polysaccharides. Polysaccharides are extremely important in aquaculture, cosmetics, pharmaceutical, and food industries, and have great economic impact worldwide. Despite this, reviews on microalgal polysaccharide production, biological activity, and chemical structure are not abundant. Moreover, techniques of microalgal cultivation, coupled with carbohydrate production, need to be clarified in order to develop forward-looking technologies. The present review provides an overview of the main advances in microalgal cell wall polysaccharide production, as well as their associated potential biological applications and chemical structure. Several studies on future prospects, related to microalgae are presented, highlighting the key challenges in microalgal polysaccharide production.

This study investigates conformational aspects of ulvans (F2) and their polycarboxyl derivatives obtained through periodate–chlorite oxidation (C3) followed by DEAE-Sephacel fractioning (C3b and C3c). Size exclusion chromatography coupled with laser light scattering and viscometric detection, in addition to circular dichroism (CD) and molecular modeling analyses, suggested that F2 had a compact sphere conformation with a helical motif as secondary structure. In contrast, all the polycarboxyl ulvans showed a random coil conformation, although C3c (NaSO3− 21.0%; COO− 1.81 mmol·g−1; Mw 18 kg·mol−1) had a more rigid and constrained backbone than C3 (NaSO3− 21.0%; COO− 1.81 mmol·g−1; Mw 49 kg·mol−1), largely due to its higher sulfate and carboxyl content. Despite the higher ionic character of C3c, its anticoagulant activity (ACA), determined by activated partial thromboplastin time (APTT) assay, was not improved compared to that of C3. Moreover, C3b (NaSO3− 14.1%; COO− 1.23 mmol·g−1; Mw 8.1 kg·mol−1) had higher activity than F2 (NaSO3− 20.6.%; COO− 0.36 mmol·g−1; Mw 123 kg·mol−1), even with its lower sulfate content and molar mass. These results suggest that the ACA of polycarboxyl ulvans relies on carboxyl and sulfate content and may depend, in addition, on a proper flexible conformation.

Melanoma is a form of skin cancer with high mortality owing to its fast progression and metastatic capacity. The treatments available nowadays are only palliative in advanced stages of the disease. Thus, alternative therapies for cancer treatment are in demand, and molecules from natural sources, such as polysaccharides, could represent new possible therapeutic approaches. Polysaccharides of freshwater and marine algae with biological activities, such as antitumor properties, are greatly reported in the scientific literature. In the present study, a sulfated heterorhamnan obtained from the green seaweed Gayralia brasiliensis (Gb1 fraction) was chemically characterized and its biological activities in the B16-F10 murine melanoma cell line were evaluated. The Gb1 polysaccharidic fraction tested concentrations presented low or absence of cytotoxicity to B16-F10 cells and neither cell proliferation nor cell cycle were altered. Interestingly, Gb1 treatment decreased B16-F10 cells migration and invasion capabilities and CD44 labeling, showing to be a promising compound for further in vitro and in vivo antitumor studies.

Natural elicitors from macroalgae may affect plant secondary metabolites. Ulvan is a sulfated heteropolysaccharide extracted from green seaweed, acting as both a plant biotic protecting agent, and a plant elicitor, leading to the synthesis of signal molecules. In this work, the aqueous extract of Ulva intestinalis L., mainly composed of ulvan, was used as foliar-spraying treatment and its eliciting effect was investigated in basil (Ocimum basilicum L.) and parsley (Petroselinum crispum L.). Antioxidant metabolites (polyphenols and carotenoids), volatile compounds (both in headspace emissions and hydrodistilled essential oils), and hormones (jasmonic acid, salicylic acid, salicylic acid 2-O-β-D-glucoside, abscisic acid, and azelaic acid) were quantified. The foliar-spraying treatment with U. intestinalis extract increased salicylic acid and its β-glucoside in parsley, in basil, it induced the accumulation of jasmonic and abscisic acids, indicating the presence of a priming effect. In basil, the elicitation caused a change of the essential oil (EO) chemotype from methyl eugenol/eugenol to epi-α-cadinol and increased sesquiterpenes. In parsley EO it caused a significant accumulation of 1,3,8-p-menthatriene, responsible of the typical “parsley-like” smell. In both species, the phenylpropanoids decreased in headspace and EO compositions, while the salicylic acid concentration increased, this could indicate a primarily defensive response to U. intestinalis extract. Due to the evidenced significant biological activity, U. intestinalis extract used as an elicitor may represent a suitable tool to obtain higher amounts of metabolites for optimizing plant flavor metabolites.

Carbohydrates are known to act as analog receptors for bacteria and therefore are promising alternatives for the control and prevention of bacterial infections. The present study evaluated the chemical structure of modified soybean meal polysaccharides and their capacity to adhere enterobacteria (Salmonella Typhimurium) and to interfere with the bacteria adhesion to the known analogue receptors, using in vitro assays. For this, soybean meal suspensions were subjected to a thermochemical extraction process and structural analyses showed that the fraction with higher adhesion and adhesion-inhibition potential, SAP, was constituted by two types of polysaccharides: a partially depolymerized pectin, of high molar mass, composed of xylogalacturonan and rhamnogalacturonan regions (SAP1, 545.5 kDa), and a (1 → 4)-linked-β-D-galactan of low molar mass (SAP2, 8.7 kDa). The results showed a high affinity of Salmonella for galactans, while high molar mass pectins showed no adhesion capacity. The chemical compositions of the fractions suggested that galactose could be responsible for the recognition process in the adhesion process. Other factors, such as structure and degree of polymerization of the polymers, may also be influencing the adhesion process. Modified soybean meal polysaccharides appear to be a promising alternative agent to antibiotics for the control and prevention of foodborne diseases.

Aqueous and KCl-soluble polysaccharides were extracted from Laurencia dendroidea (Rhodomelaceae, Ceramiales) and their chemical profile was accessed by anion-exchange chromatography, chemical and spectroscopic analyses. The homogeneous agaran DHS-4 (181.3 × 103 g. mol−1, 21.3% of NaSO3) presents A units mostly 2-sulfated (18.9 mol%), nonsubstituted (15.3 mol%) and 6-O-methylated (10.1 mol%), while B units are l -sugars composed predominantly by galactose 6-sulfate precursor units (19.2 mol%) and 3,6-anhydrogalactose (13.8 mol%), besides non-precursor galactose 6-sulfate units bearing d -xylose substituents on C-3 (8.1 mol%). The crude KCl-soluble DHS agaran (20.5% of NaSO3) inhibited proteolysis and hemolysis induced by Lachesis muta and Bothrops jararaca venoms. DHS was able to inhibit up to 75% the L. muta venom hemorrhagic effect and to reduce the lethality displayed by B. jararaca venom, increasing the mice survival time up to 3 times. Therefore, this agaran has high potential to be used as an additional tool to treat snakebite envenomation.

A water-soluble sulfated heterorhamnan (Gb1) was isolated from the green seaweed Gayralia brasiliensis and purified by ultrafiltration, yielding a homogeneous polysaccharide (Gb1r). Both fractions contained rhamnose, xylose, galacturonic and glucuronic acids, galactose, and glucose. Chemical and spectroscopic methods allowed the determination of Gb1 and Gb1r chemical structure. Their backbones were constituted by 3-, 2-, and 2,3-linked rhamnosyl units (1:0.49:0.13 and 1:0.58:0.17, respectively), which are unsulfated (13.5 and 14.6%), disulfated (16.6 and 17.8%) or monosulfated at C-2 (8 and 8.6%) and C-4 (24.5 and 23.4%). Gb1 was oversulfated giving rise to Gb1-OS, which presented ~2.5-fold higher content of disulfated rhamnosyl units than Gb1, as determined by methylation analyses and NMR spectroscopy. Gb1 and Gb1-OS potently reduced the viability of U87MG human glioblastoma cells. Gb1 caused cell cycle arrest in the G1 phase, increased annexin V-stained cells, and no DNA fragmentation, while Gb1-OS increased the percentage of cells in the S and G2 phases and the levels of fragmented DNA and cells double-stained with annexin V/propidium iodide, suggesting an apoptosis mechanism. The results suggest that the different effects of Gb1 and Gb1-OS were related to differences in the sulfate content and position of these groups along the polysaccharide chains.

The current global and economic scenario has driven the search for alternative source of natural colorants produced by microalgae. Astaxanthin (3,3′-dihydroxy-β,β′-carotene-4,4′-dione) is a secondary carotenoid widely used in food, pharmaceutical, and aquaculture industries with antioxidant effects. The green microalga Haematococcus pluvialis is the richest source worldwide of natural astaxanthin, produced with lower cost than the synthetic molecules currently used. This chapter reviews some laboratory parameters related to H. pluvialis cell enhancement, astaxanthin production, and cost. The review begins with an introduction about astaxanthin-producing H. pluvialis cells followed by upstream process conditions (e.g., microalgal media effects on biomass productivity and carotenogenesis). Subsequently, downstream process parameters are evaluated (e.g., astaxanthin extraction methods and efficiency), and laboratory production cost and future prospects of this topic are presented. Economic challenges and laboratory conditions of astaxanthin production by H. pluvialis have been reviewed and discussed in view of a cost-effective astaxanthin facility.

The development of new strategies in microalgal studies represents an outstanding opportunity to mitigate environmental problems coupled with biomass production at a reduced cost. Here we present a combined bioprocess for the treatment of rice vinasse using immobilized cyanobacteria Synechococcus pevalekii in alginate beads followed by the use of the treated vinasse as a culture medium for Dunaliella salina biomass production. Cyanobacterial-alginate beads showed a chlorophyll a production of 0.68 × 10–3 mg bead−1 and a total carotenoid production of 0.64 × 10–3 mg bead−1. The first step showed a decrease in nitrate (91%), total solids (29%), and ions. Addition of treated vinasse into D. salina cultivation resulted in a significant increase in cell replication of about 175% (optimized cultivation). The use of natural seawater drastically reduced the medium cost to US$4.75 per m3 and the addition of treated vinasse has the potential to reduce it even more (up to 69%). This study not only provides an insight on the use of cyanobacteria for rice vinasse treatment but also demonstrates a promising lower-cost medium for marine microalgal biomass production with biotechnological purposes.

Different molecules have been tested as analog receptors due to their capacity to bind bacteria and prevent cell adhesion. By using in vitro assays, the present study characterized the aqueous and alkaline extracts from microalgae Pavlova lutheri and Pavlova gyrans and evaluated the capacity of these extracts to adhere to enterobacteria (Salmonella Typhimurium). The aqueous and alkaline extracts of both species were fractionated via freeze-thawing, giving rise to soluble and insoluble (precipitate) fractions in cold water. The obtained fractions were studied using thermogravimetric, methylation analyses, and using 1D and 2D NMR techniques. The cold-water-soluble fractions obtained from the aqueous extracts were mainly composed of highly branched (1&rarr, 3),(1&rarr, 6)-&beta, glucans, whereas the cold-water-precipitate fractions were constituted by (1&rarr, 3)-&beta, glucans. The alkaline extract fractions showed similar compositions with a high protein content, and the presence of glycosides (sulfoquinovosylglycerol (SQG), digalactosylglycerol (DGG)), and free fatty acids. The linear (1&rarr, glucans and the alkaline extract fractions showed an adhesion capacity toward Salmonella. The chemical composition of the active fractions suggested that the presence of three-linked &beta, glucose units, as well as microalgal proteins and glycosides, could be important in the adhesion process. Therefore, these microalgal species possess a high potential to serve as a source of anti-adhesive compounds.

Native (F2) and carboxyl-reduced (R) ulvans from Ulva fasciata were sequentially oxidized with periodate-chlorite affording the polycarboxyl ulvans C1, C2 and C3 (1.20, 1.41 and 1.81 mmol g−1 of COOH, respectively; 19.7, 21.3 and 21.0% of NaSO3, respectively) and R-C3 (1.86 mmol g−1 of COOH; NaSO3 = 22.7%), respectively. APTT assay (polysaccharide fractions at 150 μg mL−1) showed clotting time of 45.6 s for F2 fraction. For polycarboxyl ulvans C1, C2, C3 and R-C3 the clotting times were 101.0, 122.2, 222.0 and 227.0 s, respectively. Comparison of the APTT assay results using ulvans chemically modified by carboxyl-reduction, desulfation, periodate oxidation and/or chlorite oxidation showed the anticoagulant activity of polycarboxyl ulvans is dependent of the sulfate groups present in the native polymer. In addition, the increase of the anticoagulant activity was accompanied by the increasing of the carboxyl groups and the content of this acidic substituent seems to be more important than its positioning.

Microalgal biomass production has been investigated since the 1950s by academic and industry sectors due to its potential and for biodiesel production. One of the main bottlenecks in microalgae production is biomass recovery and its separation from aqueous medium. For this reason, the use of a flocculation process is an important step to promote microalgae recovery in large scale. Here we provide a strategy for the harvesting of microalgal biomass using chitosan as flocculating agent in pilot scale cultures performed in flat plate photobioreactor. The results show that chitosan was effective in inducing microalgae flocs and separating them by settling. In the jar test scale the best clarification efficiency was around 99% and when scaled up using a 100-L photobioreactor, the biomass recovery efficiency was close to 98%. Comparison of the compositions of biomasses obtained by flocculation and centrifugation indicates no significant differences in terms of carbohydrates, proteins, lipids, and ashes, showing that the flocculation process is not affecting the biomass characteristics and its potential biotechnological applications. Based on the presented results, flocculation using chitosan as flocculant agent can be considered as an efficient method to harvest Desmodesmus subspicatus biomass cultured in pilot scale photobioreactors.

Crude extracts using hexane, dichloromethane, methanol, 80% methanol or water of two agarophytes (Gracilaria caudata and Gracilaria domingensis) and their phase partitions were evaluated on early growth of lettuce. Hexane, methanol, 80% methanol and aqueous extracts of G. caudata and dichloromethane and aqueous extracts of G. domingensis were biostimulants. Palmitic acid, the major compound of non-polar extracts and phase partition, showed a significant stimulant activity in the concentrations tested (ranging from 0.49 mM to 1.95 mM), increasing 83% of lettuce root length, comparing to control, at the highest concentration. The promoting effect of the aqueous extracts is probably related to the presence of agaran, a typical hydrocolloid polysaccharide from red algae, which is mostly an exclusive constituent of these extracts. The agarans of G. domingensis and G. caudata promoted an increase in lettuce root length of 60% and 40%, respectively (both at 1 mg·mL−1 of extract). Differences in the effects promoted by these two agarans are probably related to the different content of sulfate groups (higher for polysaccharide from G. domingensis). These results suggest that structural features of agaran-type polysaccharides can elicit distinct responses. To the best of our knowledge, this is the first report on the identification of compounds with biostimulating potential from Gracilaria.

The plant biostimulant activity of the green microalga Desmodesmus subspicatus was investigated, focusing on its potential application to organic crops. Different concentrations of D. subspicatus biomass suspensions were applied to tomato seedlings (Solanum lycopersicum) via a foliar spray. The treatments promoted root growth and foliar area, which increased when the suspension was applied at concentrations of 1 g L−1 and 0.4 g L−1, respectively. To elucidate the major constituents responsible for this potential activity, the biomass of D. subspicatus was submitted to aqueous extraction and dialysis (1 kDa cut-off), giving rise to the non-dialyzable fraction E (12.3%). Size-exclusion chromatography performed on fraction E using a Bio-Gel P-2 column yielded six subfractions. Gas chromatography-mass spectrometry (GC–MS) and nuclear magnetic resonance (NMR) analyses of the E subfractions revealed the presence of glycosides as major constituents (approx. 81%), including one acidic glycoside, [6-sulfo-α- D -quinovopyranosyl-(1→1)-glycerol], and two neutral galactosyl glycosides, [α- D -galactopyranosyl-(1→6)-β- D -galactopyranosyl-(1→1)-glycerol] and [β- D -galactopyranosyl-(1→1)-glycerol]. Ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS) analyses of fraction E resulted in the identification of the phytohormone zeatin (35 μg g−1). To evaluate the biostimulant potential of fraction E, different concentrations (0.5, 1.0, 1.5, and 2.0 g L−1) were tested for their effects on tomato seed germination, hypocotyl volume, and length. All tested concentrations induced increased hypocotyl lengths and volumes compared with standard treatment (water), at rates equivalent to those in response to a commercial product derived from Ascophyllum nodosum brown seaweed. These results indicated that the biomass suspension and aqueous extract of D. subspicatus showed plant growth biostimulant activity. Glycosides, together with zeatin, may play important roles in biostimulant activity.

In this study we described the synthesis of a hybrid polysaccharide harboring moieties of ulvan and kappa-carrabiose. Alkylamines (1,3-diaminopropane and 1,6-diaminohexane) were selectively inserted into β-D-GlcAp and α-L-IdoAp units in the ulvan structure via an amide bond formation producing ulvan-amide derivatives F-DAP (N% = 1.77; Mw = 208 kg mol−1) and F-DAH (N% = 1.77; Mw = 202 kg mol−1), which were reacted with kappa-carrabiose via reductive amination to produce hybrid ulvan-kappa-carrabiose polysaccharides F-DAP-Kb (N% = 1.56; Mw = 206 kg mol−1) and F-DAH-Kb (N% = 1.16; Mw = 200 kg mol−1). All the ulvan derivatives were characterized by 1H and 13C NMR spectroscopy and did not show cytotoxicity against human dermal fibroblasts (HDFa) at the concentrations of 25, 100, and 500 μg mL−1, neither anticoagulant properties at the range of 10–150 μg mL−1. Therefore, the ulvan-amide derivatives and the hybrid ulvan-kappa-carrabiose polysaccharides showed good biocompatibility in vitro, presenting as worthy candidates for tailoring scaffolds for biomedical applications.

In this paper, the biologically inert agarose was selectively modified at C6 of β- d -Galp units to produce an amino derivative with antibacterial property. The synthetic route involved the preparation of tosyl and azido agarose intermediates. All the polysaccharide derivatives were characterized by mono- and bidimensional 1H and 13C NMR and FT-IR analysis. A water-soluble amino polymer (Mw = 39,000 g mol−1, DSamino = 0.50) was produced by partial acid hydrolysis showing bactericidal and bacteriostatic activity against P. aeruginosa (ATCC 9027), S. aureus (ATCC 6538), and E. coli (ATCC 25922), with MIC values lower than 2.5 mg mL−1 and MBC values ranging from 2.5 to 5.0 mg mL−1.

Agarose was herein employed as starting material to produce primary, secondary and tertiary C-glycoside glycamines, including mono- and disaccharide structures. The semisynthetic approach utilized was generally based on polysaccharide-controlled hydrolysis followed by reductive amination. All reactions were conducted in aqueous media and without the need of hydroxyl group protection. We were able to identify optimal conditions for the reductive amination of agar hydrolysis products and to overcome the major difficulties related to this kind of reaction, also extending it to reducing anhydrosugars. The excess of ammonium acetate, methyl- or dimethylamine, and the use of a diluted basic (pH 11) reaction media were identified as important aspects to achieve improved yields, as well as to decrease the amount of byproducts commonly related to reductive amination of carbohydrates. This strategy allowed the transposition of the 3,6-anhydro-α-L-galactopyranose unit (naturally present in the agarose structure) to all glycamines synthesized, constituting an amino-substituted C-threofuranoside moiety, which is closely related to (+)-muscarine.

Colletotrichum gloeosporioides biomass was submitted to ethanolic extraction (78 ºC, 12 h) to remove low molecular weight compounds followed by hot aqueous extraction (100 ºC, 4 h, 4x) to obtain polysaccharides. Consecutive freezing/thawing treatments of the aqueous extract yielded a soluble fraction in cold water that was separated on five components (PI to PV) by gel exclusion chromatography on Sepharose CL-6B. The PIV was homogeneous on HPSEC/RID, with apparent MW of 2.8 x 104 g mol-1, Mw/Mn 1.17, 100% of total sugar. The PIV was composed by galactose (61%), glucose (34%) and mannose (5%). 1H and 13C NMR analysis mono- and two-dimensional, homo- (COSY) and heteronuclear (HSQC and HMBC) showed that PIV is a heteropolysacharide with a main chain constituted by β-D-galactofuranosidic units (1→5) and (1→6) linked with some of the β-D-galactofuranosidic (1→6) units substituted in O-3 by α-D-glucopiranosidic residues. Cytotoxic assays (MTT) indicated that the viability of CHO-K1 cells, when exposed to different heteropolysaccharide concentrations, did not show significant differences when compared to the viability of the negative control (CN), in the experimental times of 24 and 48 hours. These results suggest the possibility of new cytotoxic assays in other normal cell lines as well as in tumor cells.

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.

Snakebite is a serious occupational hazard affecting mainly rural populations of tropical and subtropical developing countries. Lachesis muta (Bushmaster) bites are extremely serious but are rarely reported in the literature. Bushmaster envenomings are characterized by intense local pain, edema, neurotoxicity, hypotension, local hemorrhage, and dramatic systemic alterations. Antivenom treatment has regularly been used for more than a century; however, it fails to neutralize local tissue damage and hemorrhage, leading to morbidity or disabilities in victims. Thus, the production and clinical use of antivenom must be improved. The present work characterizes, for the first time, a sulfated polysaccharide from the red seaweed, Laurencia aldingensis, including its neutralizing effect on some toxic activities of L. muta venom. Chemical and spectroscopic analyses showed that L. aldingensis produces sulfated agarans with the A-units partially C-2 sulfated or 6-O-methoxylated presetting the B-units in the cyclized (3,6-anhydro-α-L-galactose) or in the non-cyclized form (α-L-galactose). The latter is significantly substituted by sulfate groups on C-6. In vitro and in vivo assays showed that this sulfated agaran inhibited hemolysis, coagulation, proteolysis, edema, and hemorrhage of L. muta venom. Neutralization of hemorrhagic activity was also observed when the agaran was administered by different routes and after or before the venom injection. Furthermore, the agaran blocked the edema caused by a phospholipase A2 isolated from the L. muta venom. Experimental evidence therefore indicates that the sulfated agaran of L. aldingensis has potential to aid antivenom therapy of accidents caused by L. muta venom and may help to develop more effective antivenom treatments of snake bites in general.

Graphical abstract, Highlights • Comparison among well-known marine microalgae culture media was performed. • Conway medium increased cellular growth of Dunaliella salina. • Johnson medium improved accumulation of photosynthetic pigments. • Microalgal biomass showed a cost variation of US$4.64–301.61 per kg in lab scale. • Monitoring of pigment profile proved to be essential in microalgal parameters., Microalgal cultivation system depends on optimal parameters obtained from laboratory conditions to overcome high-value compounds production and decrease cost. In this study, the laboratory-scale cultivation of Dunaliella salina was performed to explore the cost and biochemical effects on biomass cultivated using F/2, Conway, and Johnson media. D. salina cultivation was monitored by cell counting, dry biomass measurements and biochemical analyses. Photosynthetic pigment profiles were identified and quantified through high-performance liquid chromatography (HPLC) whereas economic evaluation was based on media cost. Cellular growth parameters were significantly improved by Conway medium, whereas maximum accumulation of pigments, especially violaxanthin (0.855 mg g−1) and chlorophyll a (14.255 mg g−1) were observed when Johnson medium was used. Conway-biomass showed 43 % of total lipid content. This value represents 1.5 and 1.4 times higher than lipid content found in Johnson- and F/2-biomass, respectively. Furthermore, media cost presented a variation of US$1.17–49.62 for each 103 L of media mainly due to NaNO3, KNO3, and cyanocobalamin supplementation. Thus, biomass production showed a cost variation of US$4.64–301.61 per kg on a dry weight basis. These outcomes emphasize the suitability of laboratory parameters and cost comparison among biomass produced by different media.

In this paper, carrageenans having distinct sulfation patterns (κ-, ι-, ι/ν-, θ- and λ-carrageenans), were fully or partially oxidized at C-6 of the β-d-Galp units using 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and trichloroisocyanuric acid (TCCA) in bicarbonate buffer. The modified carrageenans were characterized by mono- and bidimensional 1H and 13C NMR spectroscopy. The influence of the sulfate and carboxyl groups onto anticoagulant activity was evaluated using Activated Partial Thromboplastin Time (aPTT) in vitro assay. The results showed a synergic effect of the carboxyl groups on the anticoagulant activity, which was dependent on the regiochemistry of the sulfate groups in the polysaccharide backbone. Sulfate groups at C2 of the β-d-GalAp units appeared to positively influence the anticoagulant effect in comparison to C4-sulfate samples. Also, the partially oxidized κ-carrageenan derivative (κLO) showed better anticoagulant effect than the fully oxidized carrageenan (κHO).

The present study investigated in vitro the effects of sulphated heterorhamnan (Go3), iota-/nu-carrageenans (G3d and EHW-I) and arabinogalactan (ARAGAL) polysaccharides on macrophage activation and inhibition of intracellular amastigotes of Leishmania (L.) amazonensis . All the sulphated polysaccharides (Go3, G3d and EHW-I) promoted increased nitric oxide production varying from 71 to 110%. The leishmanicidal activity of all compounds was compared to the inhibition effect of Meglumine Antimoniate at 300 μg/mL (∼79%), used as positive control. Inhibition of Leishmania ( L.) amazonensis growth was 55% with 5 μg/mL of Go3, 50% and 98% to G3d and EHW-I, respectively at 10 μg/mL, and 88% with 10 μg/mL of ARAGAL. The superoxide anion scavenging activity for the sulphated polysaccharides varied from approximately 30–55% at 10 μg/mL. In conclusion, the results of the present study indicate the promising potential of these polysaccharides for the development of new alternative therapeutic agents against leishmaniasis.

This review covers the preparation, characterization, properties, and applications of methylcelluloses (MC). In particular, the influence of different chemical modifications of cellulose (under both heterogeneous and homogeneous conditions) is discussed in relation to the physical properties (solubility, gelation) of the methylcelluloses. The molecular weight (MW) obtained from the viscosity is presented together with the nuclear magnetic resonance (NMR) analysis required for the determination of the degree of methylation. The influence of the molecular weight on the main physical properties of methylcellulose in aqueous solution is analyzed. The interfacial properties are examined together with thermogelation. The surface tension and adsorption at interfaces are described: surface tension in aqueous solution is independent of molecular weight but the adsorption at the solid interface depends on the MW, the higher the MW the thicker the polymeric layer adsorbed. The two-step mechanism of gelation is confirmed and it is shown that the elastic moduli of high temperature gels are not dependent on the molecular weight but only on polymer concentration. Finally, the main applications of MC are listed showing the broad range of applications of these water soluble cellulose derivatives.

Sulfated heterorhamnans produced by Gayralia oxysperma were utilized for the preparation of two homogeneous and highly sulfated Smith-degraded products (Mwof 109 and 251 kDa), which were constituted principally by 3-linked α- l -rhamnosyl units 2- or 4-sulfate and 2-linked α- l -rhamnosyl units 4- or 3,4-sulfate, in different percentages. The homogeneous products and the crude extracts containing the sulfated heterorhamnans showed cytotoxic effect against U87MG cells. These sulfated polysaccharides induced an increase in the number of cells in G1 phase with concomitant increase of the mRNA levels of p53 and p21. The presence of 2-linked disulfated rhamnose residues together with the molecular weight could be important factors to be correlated with the inhibitory effect on human glioblastoma cells.

Agarose was herein employed as starting material to produce primary, secondary and tertiary C-glycoside glycamines, including mono- and disaccharide structures. The semisynthetic approach utilized was generally based on polysaccharide-controlled hydrolysis followed by reductive amination. All reactions were conducted in aqueous media and without the need of hydroxyl group protection. We were able to identify optimal conditions for the reductive amination of agar hydrolysis products and to overcome the major difficulties related to this kind of reaction, also extending it to reducing anhydrosugars. The excess of ammonium acetate, methyl- or dimethylamine, and the use of a diluted basic (pH 11) reaction media were identified as important aspects to achieve improved yields, as well as to decrease the amount of byproducts commonly related to reductive amination of carbohydrates. This strategy allowed the transposition of the 3,6-anhydro-α-L-galactopyranose unit (naturally present in the agarose structure) to all glycamines synthesized, constituting an amino-substituted C-threofuranoside moiety, which is closely related to (+)-muscarine.

In the present work, we have synthesized new porphyrin conjugates bearing thiourea, thiocarbamate and carbamate linkers using conventional and ultrasound-assisted methods. These molecules were synthesized by addition reactions using isothiocyanate derivates and amino- or hydroxyl-functionalized meso-tetra(aryl)porphyrins to give porphyrin analogs linked to glycosyl or benzyl moieties. Glycoporphyrin derivates could be obtained with better yields than their respective benzyl analogs. Thiourea and carbamate glycoporphyrins were also successfully synthesized through an ultrasound protocol with a remarkable decreasing of the reaction time. By NMR experiments we were able to evaluated the linker conformations which showed a preferred Z,Z conformation for the thiourea and carbamate derivatives. In addition, porphyrins were evaluated in terms of their UV–Vis spectra, singlet oxygen production, photostability and aggregation properties. Correlations between the linker type and the corresponding photophysical properties were observed. Carbamate porphyrins seem to be the most promising photosensitizers among the studied molecules due to their high singlet oxygen production, photostability and absence of self-assembling behavior in aqueous media.

The anti-HMPV (human metapneumovirus) activity was determined for sulfated dl -hybrid galactans obtained from the red seaweed Cryptonemia seminervis and their depolymerized products obtained by reductive partial hydrolysis. Structural studies carried out in three homogeneous depolymerized fractions DS-1, DS-2e and DS-3 (Mw of 51.6–63.8 kDa) showed that these galactans present different chemical characteristics, as monosaccharide composition, content of sulfate groups (14.1–29.9%) and agaran:carrageenan molar ratio diads, 2.7:1 for DS-1 and DS-2e and 1:1 for DS-3. The sulfate groups are located principally on C-2 of β- d -galactopyranose and 4,6-O-(1′-carboxyethylidene)-β- d -galactopyranose residues and on C-6 of α-galactose residues. Sulfated dl -galactans and their depolymerized products exhibited antiviral activity at a very early stage of the viral infection cycle. All fractions, except DS-2e inhibited HMPV replication by binding to the viral particle. Besides depolymerized galactans DS-2e and DS-3 inhibited the recognition of cell receptor by HMPV and penetration to the host cell, respectively.

The aim of this study was to conduct an economic analysis and evaluate the physiological features and growth performance of the biomass produced from Haematococcus pluvialis at vegetative stage using CHU, BG-11 and WC media under batch culture. Higher cell density was achieved by using CHU and BG-11 media by the 16th day of cultivation, whereas CHU medium promoted the highest pigment content during the microalgae cultivation period. Biochemical analysis showed an increase of 26.3% on protein production when cells were cultivated on BG-11 medium compared to WC medium cultivation. Economic analysis showed that the NPK components contributed to the major participation cost in the media composition. Media cost had shown a variation of US$2.61–18.36 each 103 L of produced medium with a biomass production cost of US$6.20 (WC medium), US$21.73 (CHU medium), and US$40.36 (BG-11 medium)/kg in a dry basis.

Sulfated polysaccharides are recognized for their broad range of biological activities, including anticoagulant properties. The positions occupied by the sulfate groups are often related to the level of the inherent biological activity. Herein the naturally sulfated galactans, kappa-, iota- and theta-carrageenan, were additionally sulfated by regioselective means. The anticoagulant activity of the resulting samples was then studied using the aPTT in vitro assay. The influence of sulfate regiochemistry on the anticoagulant activity was evaluated. From kappa-carrageenan three rare polysaccharides were synthesized, one of them involved a synthetic route with an amphiphilic polysaccharide intermediate containing pivaloyl groups. Iota- and theta-carrageenan were utilized in a selective C6 sulfation at β-d-Galp units to produce different structures comprising trisulfated diads. All the samples were characterized by NMR (1D and 2D). The resulting aPPT measurements suggested that sulfation at C2 of 3,6-anhydro-α-d-Galp and C6 of β-d-Galp increased the anticoagulant activity.

Photodynamic inactivation (PDI) is an efficient approach for the elimination of a series of microorganisms; however, PDI involving phytopathogenic filamentous fungi is scarce in the literature. In the present study, we have demonstrated the photoinactivating properties of five cationic meso-(1-methyl-4-pyridinio)porphyrins on conidia of the phytopathogen Colletotrichum graminicola. For this purpose, photophysical properties (photostability and (1)O2 singlet production) of the porphyrins under study were first evaluated. PDI assays were then performed with a fluence of 30, 60, 90 and 120 J cm(-2) and varying the porphyrin concentration from 1 to 25 μmol L(-1). Considering the lowest concentration that enabled the best photoinactivation, with the respective lowest effective irradiation time, the meso-(1-methyl-4-pyridinio)porphyrins herein studied could be ranked as follows: triple-charged 4 (1 μmol L(-1) with a fluence of 30 J cm(-2))double-charged-trans2 (1 μmol L(-1) with 60 J cm(-2))tetra-charged 5 (15 μmol L(-1) with 90 J cm(-2))mono-charged 1 (25 μmol L(-1) with 120 J cm(-2)). Double-charged-cis-porphyrin 3 inactivated C. graminicola conidia in the absence of light. Evaluation of the porphyrin binding to the conidia and fluorescence microscopic analysis were also performed, which were in agreement with the PDI results. In conclusion, the cationic porphyrins herein studied were considered efficient photosensitizers to inactivate C. graminicola conidia. The amount and position of positive charges are related to the compounds' amphiphilicity and therefore to their photodynamic activity.

A homogeneous agaran fraction from Palisada flagellifera (Laurencia complex, Rhodomelaceae, Ceramiales) was obtained by aqueous room-temperature extraction, followed by ion-exchange chromatography. This galactan presents a highly complex structure with at least 18 different types of derivatives. The A units were found mostly pyruvylated, 2-sulfated (∼34%), and 6-methylated (∼34%), with the latter partially 2- and 2,4-sulfated. Minor amounts of β-D-galactopyranosyl units 2-, 6- and 2,6-sulfated, 6-glycosylated, and non-substituted are also present. The B-units are L-sugars composed predominantly of their cyclized derivatives, 3,6-anhydrogalactose and 3,6-anhydro-2-O-methylgalactose (∼56%). The former are linked to β-D-galactosyl (6-methyl) (6-glycosylated) units, as well as to 4,6-O-(1-carboxyethylidene)-β-D-galactose 2-sulfate in the proportion of 3:1.8, respectively. A significant amount (∼18%) of the α-L-galactopyranosyl units are linked to pyruvylated β-D-galactose 2-sulfate residues. An important part of the B-units (20%) is represented by α-L-galactose 6-sulfate substituted on C-3 by xylosyl, galactosyl and/or 2,3-di-O-methylgalactose units or sulfate groups that preclude their cyclization to 3,6-anhydrogalactosyl derivative. The precursor units are present in relatively low percentages. Kinetic studies suggest that in P. flagellifera agaran the cyclizable units are linked to 6-O-methyl-β-D-galactosyl and/or β-D-galactosyl units (6-glycosylated). The structural complexity of this polysaccharide is increased by the presence of 2- and 3,6-sulfated α-L-galactoses, with the latter additionally 2-O-methylated. Therefore, the major subfraction obtained from the cold extract contains structurally complex sulfated, methylated, and pyruvylated agaran.

Seaweed compounds can play important roles in either plant growth promoting or plant-pathogen interactions. The aim of this study was to evaluate the potential of crude extracts and sulfated polysaccharides isolated from the green macroalga Ulva fasciata in the control of bean anthracnose caused by Colletotrichum lindemuthianum as well the influence in the plant growth. Sulfated polysaccharides, called ulvan, were extracted with hot water, precipitated in ethanol and identified by chemical and spectroscopic methods (13C NMR). The contents of sulfate, uronic acid, protein and monosaccharides were determined. In order to obtain the crude extracts, the dried alga was extracted with methanol in Soxhlet apparatus or with ethanol at room temperature. The effect of ulvan (0.1; 1; and 10 mg ml−1) and crude extracts were tested in vitro on conidial germination and mycelial growth of C. lindemuthianum and also on the seed germination and seedling length of bean. Under greenhouse conditions, bean plants (Phaseolus vulgaris L.) were sprayed twice with ulvan or extracts and inoculated two days after the second application. The anthracnose severity was evaluated 7 days and aerial plant dry weight 14 days after inoculation. The soluble methanolic extract inhibited the mycelial growth of C. lindemuthianum in vitro, but did not reduce the disease severity under greenhouse conditions. Foliar spray of methanolic extracts enhanced the dry weight of bean plants by 20%. In contrast, ulvan increased in vitro the mycelium growth and the conidia germination of the fungus, but in greenhouse, the spray of 10 mg ml−1 ulvan reduced the anthracnose severity by 38% without affecting plant growth. The results indicate that ulvan is probably able to induce resistance to bean anthracnose.

Cryptonemia seminervis biosynthesizes a family of D,L-hybrid galactans based on the classical 3-linked beta-D-galactopyranosyl--4-linked alpha-D- and alpha-L-galactopyranosyl alternating sequence (A-units--B-units) with major amounts of alpha-D- and alpha-L-galactose and 3,6-anhydro-D- and L-galactose and lesser percentages of 3,6-anhydro-2-O-methyl-L-galactose, 2-O-methyl-, 4-O-methyl- and 6-O-methylgalactoses. The dispersion of structures in this family is based on five structural factors, namely: (a) the amount and position of substituent groups as sulfate (major), pyruvic acid ketals, methoxyl and glycosyl side-chain (4-O-methyl galactopyranosyl and/or xylosyl); (b) the ratio galactose/3,6-anhydrogalactose in the B-units; (c) the ratio D,L-galactoses and D,L-3,6-anhydrogalactoses also in the B-units, (d) the formation of diads and (e) the sequence of the diads in the linear backbone. Considering these variables it is not unexpected to find in the fractions studied at least 18 structural units producing highly complex structures. Structural studies carried out in two major fractions (S2S-3 and S2S-4) showed that these galactans were formed mainly by beta-D-galactopyranosyl 2-sulfate (20 and 11.9 mol%), beta-d-galactopyranosyl 2-sulfate 4,6-O-(1'-carboxyethylidene) (8.9 and 6.0 mol%) and beta-D-galactopyranosyl 2,6-sulfate (5.4 and 18.6 mol%), together with 3,6-anhydro-alpha-l-galactopyranosyl (11.4 and 7.3 mol%) and 3,6-anhydro-alpha-L-galactopyranosyl 2-sulfate (4.9 and 15.4 mol%) and minor quantities of 12-15 other structural units. Preparative alkaline treatment carried out on fraction (S2S-3) produced a quantitative formation of 3,6-anhydro alpha-L-galactopyranosyl units from precursor units (alpha-L-galactose 6-sulfate and alpha-L-galactose 2,6-sulfate). Kinetic studies on this 3,6-anhydro cyclization show a rate constant of 5.2 x 10(4)s(-1) indicating diads of the type G--L6S/2,6S. Data from chemical, spectroscopic and kinetic studies suggest that, in S2S-3, the agaran block in the D,L-hybrid galactan is composed of the following diads: G(6R)--L6S/2,6S and G2S(P)(2,6S)--LA(2S)(2R)(2M) and the carrageenan block of G2S(P)--D(2S)(2,3S)(3S)(3,6S) in a molar ratio of agaran to carrageenan structures of approximately 2:1.

A homogeneous sulfated heterorhamnan was obtained by aqueous extraction, then by ultrafiltration from the green seaweed Gayralia oxysperma. Besides α-l-rhamnose it contains glucuronic and galacturonic acids, xylose and glucose. The structure was established by methylation analyses of the carboxyl-reduced, carboxyl-reduced/desulfated, carboxyl-reduced/Smith-degraded, and carboxyl-reduced/Smith-degraded/desulfated products and 1D, 2D NMR spectroscopy analyses. The heterorhamnan backbone is constituted by 3- and 2-linked rhamnosyl units (1.00:0.80), the latter being ∼50% substituted at C-3 by side chains containing 2-sulfated glucuronic and galacturonic acids and xylosyl units. The 3- and 2-linked rhamnosyl units are unsulfated (20%), disulfated (16%), and mostly monosulfated at C-2 (27%) and C-4 (37%). The branched and sulfated heterorhamnan had high and specific activity against herpes simplex virus. Fil: Cassolato, Juliana E. F.. Universidade Federal do Paraná; Brasil Fil: Noseda, Miguel D.. Universidade Federal do Paraná; Brasil Fil: Pujol, Carlos Alberto. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Pellizzari, Franciane M.. Universidade Federal do Paraná; Brasil Fil: Damonte, Elsa Beatriz. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Duarte, Maria E. R.. Universidade Federal do Paraná; Brasil

We studied the chemical structure and yield of low-molecular-mass carbohydrates (LMMC) and soluble polysaccharides produced by green and red morphs of Gracilaria domingensis. Red plants had higher amounts of the LMMC floridoside than green morphs (324.4±8.1 and 220.1±6.0 μmol g-1 dry biomass, respectively). The yield of polysaccharides was similar between morphs (46.3±5.8% for the red and 41.4±8.3% for the green) as was the monosaccharide composition. The same agaran (6-O-methylated and sulphated) was isolated from both morphs, as determined by 13C NMR spectroscopy analysis. The floridean starch content (mg g-1 dry biomass) for the green morphs (116.2±1.7) was lower than that of the red morphs (143.9±1.8). This study showed that green and red morphs of G. domingensis are similar in their polysaccharide composition, but differ in the short-term storage compounds, starch and floridoside. These differences may be related to light and shade photosynthetic strategies, which lead to different storage accumulation.

Long-chain alkyl ether derivatives of sulfated oligosaccharides were semisynthesized as follows: two naturally occurring red seaweed galactans (neutral agarose and kappa-carrageenan) were submitted to partial reductive hydrolysis to give neutral and sulfated oligosaccharide alditols. The neutral disaccharide alditol (1) and its trityl ether (5) were sulfated and/or alkylated through formation of their dibutylstannylene or (bis)dibutylstannylene acetals. In these reactions, the dibutylstannylene acetals of the terminal 1,2-diols in the alditol units were more reactive than those formed on the cis-diols of the galactopyranosidic units. This property allowed the regioselective monoalkylation of a neutral tetrasaccharide alditol (2), which contained eleven free hydroxyl groups, the highest selectivity ever observed with dibutylstannylene acetals. An alkylated/sulfated derivative (11) was also obtained through the regioselective alkylation of a naturally sulfated disaccharide alditol (10, a kappa-carrageenan derivative).

In Brazil, snakebites are a public health problem and accidents caused by Lachesis muta have the highest mortality index. Envenomation by L. muta is characterized by systemic (hypotension, bleeding and renal failure) and local effects (necrosis, pain and edema). The treatment to reverse the evolution of all the toxic effects is performed by injection of antivenom. However, such therapy does not effectively neutralize tissue damage or any other local effect, since in most cases victims delay seeking appropriate medical care. In this way, alternative therapies are in demand, and molecules from natural sources have been exhaustively tested. In this paper, we analyzed the inhibitory effect of a sulfated galactan obtained from the red seaweed Palisada flagellifera against some toxic activities of L. muta venom. Incubation of sulfated galactan with venom resulted in inhibition of hemolysis, coagulation, proteolysis, edema and hemorrhage. Neutralization of hemorrhage was also observed when the galactan was administered after or before the venom injection, thus mimicking a real in vivo situation. Moreover, the galactan blocked the edema caused by a phospholipase A2 isolated from the same venom. Therefore, the galactan from P. flagellifera may represent a promising tool to treat envenomation by L. muta as a coadjuvant for the conventional antivenom.

The present work aimed to evaluate the defense responses induced by chemically sulfated ulvans in Arabidopsis thaliana plants against the phytopathogenic fungi Alternaria brassicicola and Colletotrichum higginsianum. Derivatives with growing sulfate content (from 20.9 to 36.6%) were prepared with SO3-pyridine complex in formamide. NMR and FTIR spectroscopic analyses confirmed the increase of sulfate groups after the chemical sulfation process. The native sulfated polysaccharide (18.9% of sulfate) and its chemically sulfated derivatives similarly reduced the severity of both pathogenic fungi infections. Collectively, our results suggest that ulvans induce resistance against both fungal pathogens independently of its sulfation degree.

Summary Background Photodynamic therapy (PDT) is a technique that uses light and a photosensitizer, converting local molecular oxygen into singlet oxygen, which eliminates a target unhealthy tissue. It has been increasingly used for the treatment of several diseases including skin disorders. Psoriasis is a chronic inflammatory skin disease expressing immune and hyperproliferative features. Objective This study aimed to evaluate the effect of the photosensitizer 5,10-diphenyl-15,20-di( N -methylpyridinium-4-yl)porphyrin (Di- cis -Py+) in in vivo models whereby some psoriasis-like parameters could be investigated. Methods The antiinflammation and antiproliferative activities of Di- cis -Py+ photoactivated was measured by myeloperoxidase (MPO) and N -acetyl-β- d -glucosaminidase (NAG) enzyme activity assay, measurement of IL-6, IL-1β and TNF-α levels, evaluation of proliferating cell nuclear antigen (PCNA) levels by immunohistochemistry and by Western blot. Results Treatment involving PDT and Di- cis -Py+ resulted in reduction of edema, cellular infiltration, proinflammatory cytokines, as well as reduced hyperproliferation of the epidermis. All the evaluated parameters were promoted by topical application of phlogistic agents and are similar to that observed in lesions of psoriatic skin. Conclusion The results shows the advantage of topical application, do not cause apparently photosensitivity and have effects comparable to dexamethasone, a first-line drug for the treatment of the disease.

In this study, thermogelation of methylcelluloses is investigated in relation to the molar mass and concentration in aqueous medium. A large hysteresis between heating and cooling ramps was observed whatever the conditions. The heating process in particular was studied to analyze the two steps of gelation using rheometry. At low temperature, in the sol state, viscosity depends on the concentration and molar mass. Over 30°C a gel-like behavior was observed including two steps (the second step is a strong gel with phase separation) having storage moduli that are nearly independent of polymer molar mass but are directly related to polymer concentration.

The phycocolloid iota-carrageenan (ι-CAR) was extracted from the Brazilian seaweed Meristiella gelidium . At a concentration of 5 mg ml −1 it was mixed with solutions of common corn starch (CS), high amylose starch (MS), waxy corn starch (WS) and YS starch (YS), to give systems at a final concentration of 25 g l −1 , which were subjected to rheological measurements. Each mixture gave rise to a different behaviour under dynamic rheological conditions showing a distinct degree of interaction between ι-CAR and the starch. The presence of ι-CAR in ι-CAR-WS, ι-CAR-MS and ι-CAR-CS systems resulted in synergy manifested as enhancements in thermal stability (absence of hysteresis), resulting in thermoreversible gels softer and more stable between 45 and 85 °C. In the ι-CAR-YS system, the synergistic effect occurred as an improvement in solid character, increasing the elastic nature of the gel, suggesting that the structural characteristic of YS, more regular structure with amylopectin having a low molar mass, can contribute to enhanced intermolecular binding.

Two homogeneous sulfated polysaccharides obtained from the red seaweeds Gymnogongrus griffithsiae and Cryptonemia crenulata, the kappa/iota/nu carrageenan G3d and the dl-galactan hybrid C2S-3, were assayed for their antiviral properties against the four serotypes of dengue virus (DENV) in different host cell types. Both seaweed derivatives were selective inhibitors of DENV-2 multiplication in Vero cells with inhibitory concentration 50% (IC50) values around 1 microg/ml and selectivity indices > 1000. The compounds had a lower antiviral effect against DENV-3 (IC50 values in the range 13.9-14.2 microg/ml), an even lower effect against DENV-4 (IC50 values in the range 29.3 to > 50 microg/ml) and were totally inactive against DENV-1. With respect to the host cell, the polysulfates were inhibitors of DENV-2 and DENV-3 in the human hepatoma HepG2 and foreskin PH cells, with similar antiviral effectiveness as in Vero cells, but were totally inactive in mosquito C6/36 HT cells. Mechanistic studies demonstrated that G3d and C2S-3 were active DENV-2 inhibitors only when added together with the virus or early after infection, and both initial processes of virus adsorption and internalization are the main targets of these compounds. Therefore, the variations in antiviral activity of the polysaccharides depending on the viral serotype and the host cell may be ascribed to differences in the virus-cell interaction leading to virus entry.

A homogeneous iota/nu-hybrid carrageenan (71% iota- and 21% nu-) isolated from Eucheuma denticulatum was used as a model compound to study the cyclization reaction of α- d -galactose 2,6-disulfate units to 3,6-anhydro-α- d -galactose 2-sulfate. The rate of cyclization, at 70 °C, of this carrageenan is about 50 times faster than that of a porphyran (non-sulfated β- d -galactose linked to α- l -galactose 6-sulfate) and 210 times faster when compared with a lambda-carrageenan (2-sulfated β- d -units linked to α- d -galactose 2,6-disulfate). The use of this model compound confirms the previous hypothesis of the accelerating effect of the β- d -4-sulfate group as well as suggests the influence of the 2-sulfate of the α- d -galactose units on the 4 C 1 → 1 C 4 chair forms interchange. The easy of cyclization indicates that to produce commercial iota-carrageenans milder alkaline treatments could be used, avoiding degradation and increasing the gel strength.

Carbohydrates containing galactopyranosyl and mannopyranosyl units with vicinal cis-diols were treated with NaVO(3) in D(2)O, and complexation was determined by (51)V NMR spectroscopy. Me alpha-Galp, Me beta-Galp (3,4-cis-diols), and Me alpha-Manp (2,3-cis-diol) complexed, but Me beta-Manp barely did so. This low degree of complexation also occurred with a beta-mannan containing alternate (1--3)- and (1--4)-linkages and an alginate having beta-ManpA blocks. In contrast, branched alpha-mannans complexed readily, although the (51)V resonances for one with side chains terminated with alpha-Manp-(1--3)-alpha-Manp-(1--differed from another with only alpha-Manp-(1--2)-alpha-Manp-(1--groups. The anomeric configuration of Me alpha-Galp and Me beta-Galp, each with 3,4-cis-diols remote from C-1, gave rise to three (51)V signals of complexes with similar shifts and proportions. The shifts of a galactomannan with terminal alpha-Galp-(1--2)-alpha-Manp- were the same as those with alpha-Galp-(1--6)-beta-Manp- groups, but fewer complexes were formed with the former structure, probably due to greater steric crowding of the vanadate esters. Most of the complexes gave rise to a signal in the delta515 region, consistent with the dimeric trigonal-bipyramidal structure.