Partial and total C-6 oxidation of gelling carrageenans. Modulation of the antiviral activity with the anionic character

Abstract

The optimal conditions for the full C-6 oxidation of - and -carrageenans using (2,2,6,6- tetramethylpiperidinyl)oxy (TEMPO) in the presence of sodium hypochlorite and sodium bromide were assessed. The fully oxidized products were characterized by NMR spectroscopy. Partially oxidized products were also obtained and analyzed by chemical and spectroscopical methods. The antiviral activity of carrageenans against herpes simplex virus HSV-1 and HSV-2 determined by plaque reduction assay, was not largely affected by full oxidation of the polysaccharides, but an increase in activity was detected by partial oxidation. A specific overoxidation on C-2 of the 3,6-anhydrogalactose moiety of -carrageenan was identified, solved experimentally and rationalized through the application of molecular modeling.