Chemical modifications of algal mannans and xylomannans: Effects on antiviral activity

The structures of two sulfated xylomannans extracted from the red alga Nemalion helminthoides were determined. These two fractions plus a sulfated mannan, isolated from the same alga and whose structure was previously reported, were subjected to chemical modification. The mannan was oversulfated with SO3-pyridine in dimethyl sulfoxide at 60 degrees C during two and three hours and the xylomannans were subjected to Smith degradation in order to eliminate xylose side-chains. Structural analysis of all derivatives was carried out by methylation analysis and C-13 NMR spectroscopy. Antiviral activity against herpes simplex virus type 1 and 2, and dengue virus type 2 of native and modified mannans and xylomannans was estimated. Anticoagulant effect of the active fractions was also determined. (C) 2011 Elsevier Ltd. All rights reserved.