No abstract

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.

Fucan is a term used to denominate a family of sulfated polysaccharides rich in sulfated l-fucose. We extracted six fucans from Canistrocarpus cervicornis by proteolytic digestion followed by sequential acetone precipitation. These heterofucans are composed mainly of fucose, glucuronic acid, galactose and sulfate. No polysaccharide was capable of prolonging prothrombin time (PT) at the concentration assayed. However, all polysaccharides prolonged activated partial thromboplastin time (aPTT). Four sulfated polysaccharides (CC-0.3/CC-0.5/CC-0.7/CC-1.0) doubled aPTT with only 0.1 mg/mL of plasma, only 1.25-fold less than Clexane®, a commercial low molecular weight heparin. Heterofucans exhibited total antioxidant capacity, low hydroxyl radical scavenging activity, good superoxide radical scavenging efficiency (except CC-1.0), and excellent ferrous chelating ability (except CC-0.3). These results clearly indicate the beneficial effect of C. cervicornis polysaccharides as anticoagulants and antioxidants. Further purification steps and additional studies on structural features as well as in vivo experiments are needed to test the viability of their use as therapeutic agents.

Seaweed is a rich source of bioactive sulfated polysaccharides. We obtained six sulfated polysaccharide-rich fractions (UF-0.3, UF-0.5, UF-0.6, UF-0.7, UF-1.0, and UF-2.0) from the green seaweed Udotea flabellum (UF) by proteolytic digestion followed by sequential acetone precipitation. Biochemical analysis of these fractions showed that they were enriched with sulfated galactans. The viability and proliferative capacity of 3T3 fibroblasts exposed to FeSO4 (2 µM), CuSO4 (1 µM) or ascorbate (2 mM) was not affected. However, these cells were exposed to oxidative stress in the presence of FeSO4 or CuSO4 and ascorbate, which caused the activation of caspase-3 and caspase-9, resulting in apoptosis of the cells. We also observed increased lipid peroxidation, evaluated by the detection of malondialdehyde and decreased glutathione and superoxide dismutase levels. Treating the cells with the ultrafiltrate fractions (UF) fractions protected the cells from the oxidative damage caused by the two salts and ascorbate. The most effective protection against the oxidative damage caused by iron was provided by UF-0.7 (1.0 mg/mL); on treatment with UF-0.7, cell viability was 55%. In the case of copper, cell viability on treatment with UF-0.7 was ~80%, but the most effective fraction in this model was UF-2.0, with cell viability of more than 90%. The fractions, mainly UF-0.7 and UF-2.0, showed low iron chelating activity, but high copper chelating activity and total antioxidant capacity (TAC). These results suggested that some of their protective mechanisms stem from these properties.

Some antioxidant compounds decrease the amount of intracellular reactive oxygen species (ROS) and consequently reduce the deleterious effects of ROS in osteoblasts. Thus, these compounds fight against osteoporosis. Brown seaweeds are a rich source of antioxidant fucose-containing sulfated polysaccharides (fucans and fucoidans). We obtained six fucoidans (FRFs)—F0.3, F0.5, F0.7, F1.0, F1.5, and F2.1—from Dictyota mertensii by proteolytic digestion followed by sequential acetone precipitation. Except for F0.3, all FRFs showed antioxidant activity in different in vitro tests. In pre- osteoblast-like cells (MC3T3-L1) exposed to H2O2-oxidative stress, caspase-3 and caspase-9 were activated, resulting in apoptosis of the cells. We also observed a decrease in superoxide dismutase (SOD) and alkaline phosphatase (ALP) activity. The antioxidant FRFs protected the cells from the oxidative damage caused by H2O2, decreasing intracellular ROS and caspase activation, and increasing SOD activity. The most effective protection against damage was provided by F0.7, F1.5, and F2.1. At 0.5 mg/mL, these FRFs also suppressed the H2O2-mediated inhibition of ALP activity. The data indicated that FRFs F0.7, F1.5, and F2.1 from D. mertensii were antioxidants that protected bone tissue from oxidative stress and could represent possible adjuvants for the treatment of bone fragility through counteracting oxidative phenomena.