Chemically sulfated natural galactomannans with specific antiviral and anticoagulant activities

• Naturally occurring galactomannans were sulfated to give sulfated galactomannans.
• Sulfated galactomannans had moderate anticoagulant, 13.4–36.6 units/mg, and high anti-HIV and anti-Dengue virus activities, 0.04–1.1 μg/mL.
• The cytotoxicity on MT-4 and LCC-MK2 cells was low.
• Strong interaction of sulfated galactomannans with poly-l-lysine revealed by SPR.
• Sulfated galactomannans effectively prevented the infection of cells by viruses.

Naturally occurring galactomannans were sulfated to give sulfated galactomannans with degrees of substitution of 0.7–1.4 per sugar unit and molecular weights of M¯n = 0.6 × 104–2.4 × 104. Sulfated galactomannans were found to have specific biological activities in vitro such as anticoagulant, anti-HIV and anti-Dengue virus activities. The biological activities were compared with those of standard dextran and curdlan sulfates, which are polysaccharides with potent antiviral activity and low cytotoxicity. It was found that sulfated galactomannans had moderate to high anticoagulant activity, 13.4–36.6 unit/mg, compared to that of dextran and curdlan sulfates, 22.7 and 10.0 unit/mg, and high anti-HIV and anti-Dengue virus activities, 0.04–0.8 μg/mL and 0.2–1.1 μg/mL, compared to those curdlan sulfates, 0.1 μg/mL, respectively. The cytotoxicity on MT-4 and LCC-MK2 cells was low. Surface plasmon resonance (SPR) of sulfated galactomannans revealed strong interaction with poly-l-lysine as a model compound of virus proteins, and suggested that the specific biological activities might originate in the electrostatic interaction of negatively charged sulfate groups of sulfated galactomannans and positively charged amino groups of surface proteins of viruses. These results suggest that sulfated galactomannans effectively prevented the infection of cells by viruses and the degree of substitution and molecular weights played important roles in the biological activities.