Isolation, structural features, in vitro antioxidant activity and assessment of complexation ability with ß-lactoglobulin of a polysaccharide from Borassus flabellifer fruit.

This research was intended to investigate the structural feature, antioxidative activity and interaction with ß-lactoglobulin (ß-lg) of a polysaccharide (P) isolated from Borassus flabellifer fruit thru aqueous extraction, protein elimination and chromatographic techniques. Polysaccharide P (molecular weight: 21,000 g mol-1) was constituted of arabinose, galactose, glucose, and rhamnose in a 50:24:20:6 M ratio alongside 9% (w/w) galacturonic acid. It encompassed a petite backbone entailing galacturonopyranosyl and rhamnopyranosyl units substituted with sizable side chains comprising of arabinofuranosyl, galactopyranosyl and esterified coumaric acid (CA) residues. Various series of oligosaccharides including (i) Gal1,2,4-9Ac5-29, (ii) Ara2-3Ac6-8, (iii) Gal3Ara1-3Ac13-17, (iv) Gal4-6Ara2Ac18-24, (v) Gal6Ara1Ac22 and (vi) Gal1Ara2CA1Ac7 and Gal1Ara3CA1Ac9 epitomizing polysaccharide structure were generated and characterised. Fraction P exhibited dose-dependent antioxidant activity and possessed a strong ß-lactoglobulin binding capability. Accordingly, B. flabellifer fruit offers an antioxidative polysaccharide having novel structure that can associate with ß-lg and, hence, useful in formulating novel food possessing adjustable composition.

Chemically sulfated polysaccharides from natural sources: Assessment of extraction-sulfation efficiencies, structural features and antiviral activities.

The provisioning of compound libraries with a high degree of diversity and attractive pharmacological properties is a limiting step in drug development. This study reports the production of highly bioactive sulfated polysaccharides, originally present in a nonsulfated, dormant state in natural sources, and demonstrates their antiviral activity (human cytomegalovirus EC50 values of 2.34-7.77 µg/mL) at a low degree of cytotoxicity. Furthermore, data strongly suggested the inhibition of virus entry as the main mode of antiviral action. Remarkably, the utilized oleum-DMF reagent was able to generate a range of sulfated polysaccharides from various natural sources, possessing varying saccharide compositions, degrees of sulfation (0.4-1.7) and molecular masses (38-94,000 g/mol). Typically, in a matter of minutes, this reagent not only solubilized polysaccharides but also chemically converted their hydroxyl functionality into sulfates. The most active sulfated polysaccharide (EC50 of 2.62 µg/mL) proved to be a 94,000 g/mol branched glucan with sulfates at C-6/C-3,6/C-2,3,6 positions. In conclusion, the important determinants of such compounds' antiviral activity are: (i) degree of sulfation, (ii) molecular mass and (iii) structural features. Thus, our approach offers a huge prospect for the improvement of natural source-derived libraries based on biologically active polysaccharides with diversified chemical profiles.

Assessment of antiherpetic activity of nonsulfated and sulfated polysaccharides from Azadirachta indica.

Azadirachta indica leaf is used by Indian population for the healing of various diseases including viral infection. Herein, we analyzed the antiherpetic (HSV-1) activity of two polysaccharides (P1 and P2) isolated from the leaf of A. indica and their chemically sulfated derivatives (P1S and P2S). The molecular weights of P1S and P2S are 41 and 11 kDa, respectively. Sulfate groups are located at positions C3 of the Araf and C6 of both Galp and Glcp residues of the most active polysaccharide (P1S). These compounds were not cytotoxic in HEp-2 cells, up to 1000 µg/mL. Both P1S and P2S exhibited antiviral activity when used simultaneously to HSV-1, with 50% inhibitory concentration/selectivity index, respectively, of 31.1 µg/mL/>51.4 and 80.5 µg/mL/>19.8. P1S showed better inhibitory effect (91.8%) compared to P1 (50%), P2 (71.1%) and P2S (70%) at 200 µg/mL. Synthesis of viral protein showed a dose-dependent response and the nucleic acid synthesis was inhibited up to 25 µg/mL, by P1 and P1S and up to 50 µg/mL, by P2 and P2S. The antiviral effect is probably due to the interference of polysaccharides at the early stages of HSV-1 replication, including adsorption. Further studies are under way to get insight into the mechanism of action of the substances.