Interaction between sulfated 3-O-octadecyl-α-(1→6)-d-glucan and liposomes analyzed by surface plasmon resonance.

To elucidate the role of long alkyl group in sulfated poly- and oligosaccharides on anti-HIV activity, the interaction between sulfated 3-O-octadecyl-(1→6)-α-d-glucopyranan with potent anti-HIV activity and liposomes with diameters of 58 ± 20 nm and 107 ± 28 nm as models of HIV were investigated. SPR measurements of sulfated 3-O-octadecyl-(1→6)-α-d-glucopyranans bearing 2.8 mol% of the octadecyl group and the liposome (diameter = 58 ± 20.0 nm and ζ=0 mV) resulted in an apparent association- ka = 6 × 105 1/M, a dissociation-rate kd = 4 × 10-4 1/s, and a dissociation constants KD = 8 × 10-10 M. The particle size of the sulfated 3-O-octadecyl-(1→6)-α-d-glucopyranan (67 ± 14 nm) measured by DLS increased to 104 ± 25 nm, whereas the ζ potential (-29 mV) was unchanged (-33 mV). For dextran sulfate without an alkyl group, no interaction was observed. These results suggest that the long octadecyl group penetrated into the liposome and sulfated glucopyranan was covered on the liposome to increase the anti-HIV activity. The 107 nm liposome exhibited similar results.

Ring-opening polymerization of new 3-O-branched 1, 6-anhydro glucopyranose di- and trisaccharide monomers.

New 3-O-branched 1, 6-anhydro glucopyranose disaccharide monomers, 1, 6-anhydro-2, 4-di-O- benzyl-3-O-(2', 3', 4', 6'-tetra-O-benzyl-α-D-mannopyranosyl)- (LGM 6) and -glucopyranosyl)-ß-D- glucopyranose (LGG 7), and a trisaccharide monomer, 1, 6-anhydro-2, 4-di-O-benzyl-3-O-α-(2', 3', 6', 2″, 3″, 4″, 6″-hepta-O-benzyl- α-D-maltopyranosyl)-ß-D-glucopyranose (LGMAL 8), were synthesized and polymerized. It was found that the 3-O-branched1, 6-anhydro disaccharide monomers were polymerized. However, the polymerizability was lower than that of the 4-O-branched disaccharide monomers reported previously, and the trisaccharide monomer was not polymerizable, probably due to the steric hindrance of the branched bulky mono and disaccharide units at the 3-O position in 1, 6-anhydro glucopyranose. Debenzylation of the resulting polymers gave 3-O-gluco- and mannopyranosidic (1 â†’ 6)-α-D-glucopyranans in moderate yields. These results are the first reports of the polymerization of 3-O-branched 1, 6-anhydro glucopyranose disaccharide monomers to give 3-O-branched polysaccharides.

Chemically sulfated natural galactomannans with specific antiviral and anticoagulant activities.

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=0.6×10(4)-2.4×10(4). 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, 13.4-36.6unit/mg, compared to that of dextran and curdlan sulfates, 22.7 and 10.0unit/mg, and high anti-HIV and anti-Dengue virus activities, 0.04-0.8µg/mL and 0.2-1.1µg/mL, compared to those curdlan sulfates, 0.1µg/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.

Synthetic galactomannans with potent anti-HIV activity.

Ring-opening polymerization of a new 1,6-anhydro disaccharide monomer, 1, 6-anhydro-2, 3-di-O-benzyl-4-O-(2', 3', 4', 6'-tetra-O-benzyl-α-d-galactopyranosyl)-α-d-mannopyranose, was carried out using PF5 as a catalyst under high vacuum at -60°C to give galactose branched mannopyranan (synthetic galactomannan), 4-O-α-d-galactopyranosyl-(1→6)-α-d-mannopyranan, after debenzylation with Na in liquid NH3. The ring-opening copolymerization with 1, 6-anhydro-tri-O-benzyl-α-d-mannopyranose in various feeds was also performed to give synthetic galactomannans with various proportions of galactose branches. After sulfation, sulfated synthetic galactomannans were found to have anti-HIV activity and cytotoxicity as high and low as those of standard curdlan and dextran sulfates, respectively, which are potent anti-HIV sulfated polysaccharides with low cytotoxicity. The anti-HIV mechanism of sulfated synthetic galactomannans used by poly-l-lysine as a model peptide of the HIV surface protein was estimated by using SPR, DSL, and zeta potential measurements, revealing the electrostatic interaction between negatively charged sulfate groups and positively charged amino groups.