Semisynthesis of new sulfated heterorhamnan derivatives obtained from green seaweed Gayralia brasiliensis and evaluation of their anticoagulant activity.

Marine green algae produce sulfated polysaccharides with diverse structures and a wide range of biological activities. This study aimed to enhance the biotechnological potential of sulfated heterorhamnan (Gb1) from Gayralia brasiliensis by chemically modifying it for improved or new biological functions. Using controlled Smith Degradation (GBS) and O-alkylation with 3-chloropropylamine, we synthesized partially water-soluble amine derivatives.

Semisynthesis and characterization of versatile azide intermediates using sodium alginate and its homopolymeric derivatives as starting material.

Alginate, a polyuronic biopolymer composed of mannuronic and guluronic acid units, contain hydroxyl and carboxyl groups as targeting modification sites to obtain structures with new and/or improved biological properties. The copper-catalyzed azide-alkyne cycloaddition (CuAAC) is a versatile click reaction for polymer functionalization, but it typically requires a "pre-click" modification to introduce azide or alkyne groups. Here, we described a straightforward chemical path to selectively modify alginate carboxyl groups producing versatile azido derivatives through N-acylation using 3-azydopropylamine.

A new porphyrin as selective substrate-based inhibitor of breast cancer resistance protein (BCRP/ABCG2).

The ABCG2 transporter plays a pivotal role in multidrug resistance, however, no clinical trial using specific ABCG2 inhibitors have been successful. Although ABC transporters actively extrude a wide variety of substrates, photodynamic therapeutic agents with porphyrinic scaffolds are exclusively transported by ABCG2. In this work, we describe for the first time a porphyrin derivative (4B) inhibitor of ABCG2 and capable to overcome multidrug resistance in vitro.

Chemical structure of native and modified sulfated heterorhamnans from the green seaweed Gayralia brasiliensis and their cytotoxic effect on U87MG human glioma cells.

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.

Synthesis of C6-amino agarose and evaluation of its antibacterial activity.

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 H and C NMR and FT-IR analysis.

Semi-synthesis of hybrid ulvan-kappa-carrabiose polysaccharides and evaluation of their cytotoxic and anticoagulant effects.

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; M = 208 kg mol) and F-DAH (N% = 1.

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

In this article, we describe the semi-synthesis of N-alkyl-kappa-carrageenan derivatives and their antibacterial activity against Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC 8739), and Pseudomonas aeruginosa (ATCC 9027). Kappa-carrageenan was submitted to partial acid hydrolysis promoting the selective cleavage of α-glycosidic bonds involving 3,6-anhydro-α-D-Galp units, giving rise to reducing low-molecular weight polysaccharide fragments, which were reacted with alkylamines of varying chain lengths by reductive amination. The carrageenan derivatives were characterized by HPSEC-MALLS-RID and 1D and 2D H and C NMR spectroscopy.

Conformational analysis of ulvans from Ulva fasciata and their anticoagulant polycarboxylic derivatives.

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 (NaSO 21.

Effects of carboxyl group on the anticoagulant activity of oxidized carrageenans.

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 H and C NMR spectroscopy. The influence of the sulfate and carboxyl groups onto anticoagulant activity was evaluated using Activated Partial Thromboplastin Time (aPTT) in vitro assay.

Monitoring of κ-carrageenan depolymerization by capillary electrophoresis and semisynthesis of oligosaccharide alditols.

Different hydrolysis conditions to produce κ-carrageenan oligosaccharide alditols were studied and the depolymerization process monitored by capillary electrophoresis (CE). Semisynthesis, ion-exchange and exclusion chromatography were used to obtain and isolate sulfated di-, tetra- and hexasaccharide alditols, the last being fully characterized for the first time. Those derivatives were used as standards to validate a new quantitative CE analytical method which was used to compare two different partial hydrolysis methodologies: an acid hydrolysis followed by reduction and a one-pot reductive hydrolysis using 4-methylmorpholine borane.

Modification of ulvans via periodate-chlorite oxidation: Chemical characterization and anticoagulant activity.

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.

Aqueous semisynthesis of -glycoside glycamines from agarose.

Agarose was herein employed as starting material to produce primary, secondary and tertiary -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.

Photodynamic effect of meso-(aryl)porphyrins and meso-(1-methyl-4-pyridinium)porphyrins on HaCaT keratinocytes.

Sixteen porphyrins, including neutral, anionic and cationic meso-(aryl)porphyrins and meso-(1-methyl-4-pyridinium)porphyrins were herein evaluated in terms of their photosensitizing properties against HaCaT keratinocytes. After an initial screening, the cationic porphyrins were studied in more details, by both determining their log P and performing PDT assays in lower porphyrin concentrations. Porphyrins presenting two or more adjacent positively charged groups, directly linked to the macrocycle meso positions, appeared to be the most effective photosensitizers.

On the phosphorylase activity of GH3 enzymes: A β-N-acetylglucosaminidase from Herbaspirillum seropedicae SmR1 and a glucosidase from Saccharopolyspora erythraea.

A phosphorolytic activity has been reported for beta-N-acetylglucosaminidases from glycoside hydrolase family 3 (GH3) giving an interesting explanation for an unusual histidine as catalytic acid/base residue and suggesting that members from this family may be phosphorylases [J. Biol. Chem.

In vitro photodynamic inactivation of conidia of the phytopathogenic fungus Colletotrichum graminicola with cationic porphyrins.

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.

Acid heteropolysaccharides with potent antileishmanial effects.

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%.

Investigation of anti-inflammatory and anti-proliferative activities promoted by photoactivated cationic porphyrin.

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.

Sulfated heterorhamnans from the green seaweed Gayralia oxysperma: partial depolymerization, chemical structure and antitumor activity.

Sulfated heterorhamnans produced by Gayralia oxysperma were utilized for the preparation of two homogeneous and highly sulfated Smith-degraded products (M(w) of 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.

Glucogalactan: a polysaccharide isolated from the cell-wall of Verticillium lecanii.

A water-soluble polysaccharide was extracted with alkali from the cell wall of Verticillium lecanii (also called Lecanicillium lecanii). After freezing and thawing, the water-soluble fraction was purified by gel filtration chromatography on Sepharose CL-6B and eluted as one peak by HPSEC/RID. Monosaccharide analysis showed galactose and glucose (1.

Selective sulfation of carrageenans and the influence of sulfate regiochemistry on anticoagulant properties.

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.

Chemical structure of the complex pyruvylated and sulfated agaran from the red seaweed Palisada flagellifera (Ceramiales, Rhodophyta).

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.

Differential inhibition of dengue virus infection in mammalian and mosquito cells by iota-carrageenan.

The antiviral activity against dengue virus-2 (DENV-2) of carrageenans reported here has shown a differential susceptibility of C6/36 HT and Vero cells, taken as models of mosquito and mammalian cells, depending on the structural class of polysaccharides: all polysaccharides blocked DENV-2 infection in monkey Vero cells, but only iota-carrageenans were virus inhibitors in mosquito cells. However, iota-carrageenans were less effective in mosquito cells in comparison with mammalian cells with effective concentration 50 % (EC(50)) values in C6/36 HT cells 4.9-17.

ESI-MS differential fragmentation of positional isomers of sulfated oligosaccharides derived from carrageenans and agarans.

We have prepared a number of isomeric red seaweed galactan-derivative sulfated oligosaccharides to determine whether there were diagnostic differences among the isomeric mass spectra obtained using ESI CID MS/MS (triple quadrupole instrument). Fragmentation of the single or multicharged molecular ions from di-, tetra-, and hexasaccharides indicated that the relative positioning of the sulfate groups and type of monosaccharide unit affect the rate of cleavage of the glycosidic bonds. We also performed a comparative [M-Na](-) fragmentation study of positional isomers of sulfated disaccharides that present all four monosulfation possibilities on the galactopyranosidic ring.

Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry analysis of oligosaccharides and oligosaccharide alditols obtained by hydrolysis of agaroses and carrageenans, two important types of red seaweed polysaccharides.

MALDI-TOF mass spectrometry analyses of several oligosaccharides (aldoses) and oligosaccharide alditols derived from agaroses, kappa- and iota-carrageenans using different matrices (2,5-dihydroxybenzoic acid, nor-harmane, ferulic acid, and the ionic liquid matrices 2,5-dihydroxybenzoic acid-n-butylamine and ferulic acid-n-butylamine) were conducted. These carbohydrates were selected as model compounds to study the MALDI prompt and post-source decay (PSD) fragmentation processes of both families of oligosaccharides. Sulfated alditols showed in the negative-ion mode the molecular ion as [M-Na](-) together with the species yielded by their prompt fragmentation (mainly desulfation) while the sulfated oligosaccharides (aldoses) showed mainly glycosidic prompt fragmentation (glycosidic C-cleavages and desulfation).

Galactans from Cryptonemia species. Part II: studies on the system of galactans of Cryptonemia seminervis (Halymeniales) and on the structure of major fractions.

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.