In Vitro Antitumor Potential of Sulfated Polysaccharides from Seaweed Caulerpa cupressoides var. flabellata.

Seaweeds are important source of bioactive compounds, including sulfated polysaccharides (SP). Because of their structural heterogeneity, these compounds are promising sources of anticancer compounds. SP from brown and red seaweeds have shown antimelanoma activity in different in vitro and in vivo models. However, SP from green seaweed are still poorly evaluated. Therefore, SP were extracted from the green alga Caulerpa cupressoides var. flabellata, and their antiproliferative, anti-migratory, and inhibitory effect on melanin production on B16-F10 melanoma cells was evaluated. Cell assays, including flow cytometry, demonstrated that SP (100-1000 µg mL-1) are non-cytotoxic, do not induce apoptosis or necrosis, and do not interfere with cell cycle. However, SP (1000 µg mL-1) were found to significantly inhibit cell colony formation (80-90%), cell migration (40-75%), and melanin production (~ 20%). In summary, these results showed that SP inhibited important melanoma development events without cytotoxicity effects, suggesting that C. cupressoides may be an important source of SP with antitumor properties.

Immunostimulatory Effect of Sulfated Galactans from the Green Seaweed Caulerpa cupressoides var. flabellata.

Sulfated polysaccharides (SPs) obtained from green seaweeds are structurally heterogeneous molecules with multifunctional bioactivities. In this work, two sulfated and pyruvated galactans were purified from Caulerpa cupressoides var. flabellata (named SP1 and SP2), and their immunostimulatory effect was evaluated using cultured murine macrophage cells. Both SPs equally increased the production of nitric oxide, reactive oxygen species, and the proinflammatory cytokines TNF-α and IL-6. NMR spectroscopy revealed that both galactans were composed primarily of 3)-ß-d-Galp-(1→3) units. Pyruvate groups were also found, forming five-membered cyclic ketals as 4,6-O-(1'carboxy)-ethylidene-ß-d-Galp residues. Some galactoses are sulfated at C-2. In addition, only SP2 showed some galactose units sulfated at C-4, indicating that sulfation at this position is not essential for the immunomodulatory activity of these galactans. Overall, the data showed that the galactans of C. cupressoides exhibited immunostimulating activity with potential therapeutic applications, which can be used in the development of new biomedical products.

Gallic Acid-Dextran Conjugate: Green Synthesis of a Novel Antioxidant Molecule.

A novel derivative of dextran, dextran-gallic acid (Dex-Gal), obtained from simple conjugation with gallic acid, was synthesized by an efficient free radical-mediated method. To verify the synthesis of Dex-Gal, 1H-nuclear magnetic resonance (1H-NMR), Fourier transform infrared (FTIR) spectrometry, and high-performance size-exclusion chromatography (HPSEC) were employed. The results revealed the conjugation of gallic acid with the 15.5 kDa dextran from Leuconostoc mesenteroides. Dex-Gal had a molecular weight of 11.2 kDa, indicating that the conjugation reaction was accompanied by a minor degradation of Dex-Gal. In addition, Dex-Gal contained 36.8 ± 1.4 mg gallic acid per gram dextran. These molecules were also evaluated as antioxidants using total antioxidant capacity (TAC), reducing power, ferric chelation, and superoxide radical-scavenging assays. Both polysaccharides had no ferric chelation activity. In addition, Dex-Gal was more efficient as an antioxidant agent in TAC (13 times) and was more efficient than dextran in superoxide radical-scavenging (60 times) and reducing power (90 times) assays. These data demonstrate that Dex-Gal is a natural-compound-based antioxidant with potential applications in the pharmaceutical, cosmetic, and food industries.

Pharmacological prospection and structural characterization of two purified sulfated and pyruvylated homogalactans from green algae Codium isthmocladum.

Two sulfated polysaccharides (SPs), F2 and F3, isolated from Codium isthmocladum were found to contain galactose, sulfate, and pyruvate. The apparent molecular weights of F2 and F3 were determined to be 62 and 61 kDa, respectively. NMR spectroscopy combined with chemical analysis showed that F2 and F3 have the same structural features. However, F3 showed higher sulfate/sugar ratio (1/2.6) than F2 (1/4). F2 and F3 are essentially (1 → 3)-ß-D-galactans with some branching at C6. Pyruvylation occurs at O3 and O4, forming 3,4-O-(1-carboxyethylidene)-ß-D-Galp residues; some of these pyruvylated residues contain sulfate groups at C6. Some non-branching residues contain sulfate at C4. None of the SPs exhibited antioxidant activity. MTT results indicated that 1 mg/mL of both SPs about 40% of PANC-1 cell viability. At 10 µg/mL, F2 and F3 had 1.7-fold longer clotting times compared to that of Clexane® at the same concentration. The higher sulfate content of F3 is not a determining factor for pharmacological activities of galactans, considering that both F2 and F3 exerted the effects.

Antiproliferative xylan from corn cobs induces apoptosis in tumor cells.

Xylan is one of the most abundant hemicellulose constituents in the plant kingdom. We extracted xylan from corn cobs (XCC) using ultrasound. The structure of XCC was determined by NMR analysis, which revealed a composition of xylose:glucose:arabinose:galactose:mannose:glucuronic acid in a molar percentage ratio of 48:21:16:10:2.5:2.5. XCC induced the proliferation of murine macrophage cells (RAW 264.7) and inhibited the proliferation of human lung adenocarcinoma epithelial cells (A549) by 20% and human cervical adenocarcinoma cells (HeLa) by 60%. Several cell death-associated morphological changes were observed after the exposure of HeLa cells to XCC for 24 h. In addition, by using fluorescent probes, we observed a larger number of irregular and pyknotic nuclei with condensed chromatin bodies (nuclear condensation). FACS analysis showed an increase in the number of annexin V-positive and propidium iodide (PI)-positive cells (37.0%) in the presence of XCC compared with that of the negative control cells (5.0%). XCC also increased the ratio of Bax:Bcl-2 (3.5:1) and the levels of cytochrome c, caspase 3, and apoptosis-inducing factor (AIF) in treated cells. Therefore, the results demonstrated the antiproliferative potential of XCC, which induced apoptosis in HeLa cells.

Chemical structure, antiproliferative and antioxidant activities of a cell wall α-d-mannan from yeast Kluyveromyces marxianus.

Cell wall polysaccharides from filamentous fungi and yeasts have been reported as antioxidant and antiproliferative polymers. Thus, we evaluated these activities from cell wall polysaccharides from Kluyveromyces marxianus CCT7735. By using a centrifugal filter, a 203kDa α-d-mannan (KMM-5) was obtained. KMM-5 exhibited no effect on HeLa cells and a weak antiproliferative activity against Hep-G2 cells. In addition, at higher concentrations, it presented a cytotoxicity to the normal cell line, 3T3. However, KMM-5 showed copper- and iron-chelating abilities, the latter of which presented improved activity. By using 2D-NMR COSY, HSQC edited and HMBC experiments, a structure arrangement was proposed. The main chain was formed by 6)-α-d-Manp-(1→6) units substituted at the 2-O-position by non-reducing terminals α-d-Manp-(1→2) and by a branched tetrasaccharide. The latter was formed by an internal 2)-α-d-Manp-(1→2) unit with linked to it a 2,3)-α-d-Manp-(1→2) unit substituted at the 2-O-position by a non-reducing terminal α-d-Manp-(1→2), and at the 3-O-position by a non-reducing terminal α-d-Manp-(1→3). In conclusion, we considered K. marxianus CCT7735 a source of natural and renewable polysaccharides with pharmacological properties.

Anticoagulant, antioxidant and antitumor activities of heterofucans from the seaweed Dictyopteris delicatula.

In the present study, six families of sulfated polysaccharides were obtained from seaweed Dictyopteris delicatula by proteolytic digestion, followed by acetone fractionation and molecular sieving on Sephadex G-100. Chemical analyses demonstrated that all polysaccharides contain heterofucans composed mainly of fucose, xylose, glucose, galactose, uronic acid, and sulfate. The fucans F0.5v and F0.7v at 1.0 mg/mL showed high ferric chelating activity (∼45%), whereas fucans F1.3v (0.5 mg/mL) showed considerable reducing power, about 53.2% of the activity of vitamin C. The fucan F1.5v presented the most prominent anticoagulant activity. The best antiproliferative activity was found with fucans F1.3v and F0.7v. However, F1.3v activity was much higher than F0.7v inhibiting almost 100% of HeLa cell proliferation. These fucans have been selected for further studies on structural characterization as well as in vivo experiments, which are already in progress.