In vitro anti-influenza virus activity of a plant preparation from Geranium sanguineum L.

A polyphenolic complex (PC), isolated from the Bulgarian medicinal plant Geranium sanguineum L., was shown to have selective anti-influenza activity in vitro. Expression of HA on the surface of cells infected with A/chicken/Rostock/34, virus-induced cytopathic effect, infectious virus yield and plaque formation were all reduced at non-toxic concentrations of PC. Synthesis of virus proteins was also selectively inhibited. High concentrations of PC (> 200 microg/ml) exhibited a strong virucidal effect. Although the action was directed against an early stage of infection (within 3 h of infection), the process directly affected was not identified. The selectivity of antiviral action was confirmed by the variation in sensitivity of different influenza viruses to PC and the selection of variants with reduced drug sensitivity.