The herpes simplex virus (HSV) is a widespread human pathogen and for many reasons the
development of anti-herpetic drugs from natural products has been encouraged. Adenanthera pavonina
(Ap) is a medicinal plant widely used in Brazil, among other uses. Herein, a native Ap seed polysaccharide
(PLSAp) and its chemically sulfated derivate (SPLSAp) were studied by Fourier transform IR
spectra (FT-IR), gel permeation chromatography (GPC) for molar mass determination and their intrinsic
viscosity [η]. Biologically, the compounds were evaluated for anti-HSV activity, in HEp2 cell cultures.
The cytotoxic concentrations (CC50) and the inhibitory concentrations (IC50) of the polysaccharides were determined
by the colorimetric assay (dimethyl-thiazolyl-diphenyltetrazolium bromide) and plaque reduction assay (PRA), respectively.
The SPLSAp showed a better antiviral activity when compared to the PLSAp with a CC50 of 500 μg/ml, the
IC50 equal to 15μg/ml and the selectivity index (SI) of 33.3. The time-of-addition and the time-of-removal assays demonstrated
the highest inhibitory activity between 8-16h after the infection. The inhibition of viral DNA and protein syntheses
by SPLSAp monitored by PCR and immunofluorescence assay (IFA), respectively, has also demonstrated. These findings
demonstrated that the SPLSAp inhibited HSV-1 infection in different steps of the replication and, therefore, represents a
valuable compound for preclinical studies in anti-herpetic therapy.