Abstract This study investigated the antiviral activities of Radix Isatidis polysaccharide (RIP) against type II herpes simplex virus (HSV-2) in vitro. RIP was prepared from the Radix Isatidis root. The toxicity of RIP on Vero cells was detected. The direct killing effect of RIP on HSV-2, inhibitory effect of RIP on HSV-2 replication and inhibitory effect of RIP on HSV-2 adsorption were determined. Results showed that, RIP in concentration range of 25-800 mg/L had no toxic effect on Vero cells. RIP with different concentrations could not directly inactivate the HSV-2. The effective rates on inhibition of HSV-2 replication and adsorption in 800 mg/L RIP group were 71.57% and 48.37%, respectively, which were the highest among different groups. In conclusion, RIP has the antiviral effect against HSV-2 in vitro. This effect mainly occurs in inhibiting the virus duplication and adsorption.

The antifungal properties of eugenol were tested against ten plant pathogenic fungal species and detailed studies were conducted regarding in vitro activity of eugenol on Botrytis cinerea. The EC50 value of eugenol on mycelial radial growth of B. cinerea was 38.6 μg/mL; however, eugenol had no bioactivity against conidia germination. B. cinerea hyphae treated with eugenol showed strong propidium iodide fluorescence in the cytosol. Eugenol increased the concentration of potassium ion and cellular materials in the medium. Furthermore, light and scanning electron microscopy observations on hyphae exposed to eugenol revealed considerable morphological alterations in hyphae, such as cytoplasmic coagulation, vacuolation, and hyphal shriveling. Eugenol induced the generation of H2O2 and increased free Ca2+ in the cytoplasm. These results strongly support the idea that the antifungal activity of eugenol is due to membrane binding and permeability alteration, leading to destabilization and disruption of the plasma membrane.