Xylans from Scinaia hatei: Structural features, sulfation and anti-HSV activity.

Natural compounds offer interesting pharmacological perspectives for antiviral drug development with regard to broad-spectrum antiviral properties and novel modes of action. In this study, we have analyzed alkali-extracted xylan of Scinaia hatei. Alkali extraction of this red alga yielded a xylan shown to have a molecular mass of 120kDa and a linear structure of (1-->4)-linked beta-d-xylopyranosyl residues. Derivatives (S1, S2, S3 and S4) generated by chemical sulfation from this macromolecule had degree of sulfation between 0.93 and 1.95, and contained strong anti-HSV activity with inhibitory concentration 50% (IC(50)) from 0.22 to 1.37mug/ml. Furthermore, they had no direct inactivating effect on virions in a virucidal assay. Sulfate groups account for their in vitro antiviral activity. Interestingly, sulfated xylans already exerted anti-HSV activity when only pre-incubated with the cultured cells prior to infection, thus pointing to a main inhibitory effect on viral entry.