Euphorbia thymifolia suppresses herpes simplex virus-2 infection by directly inactivating virus infectivity.

1. The ethyl acetate (EtOAc) extract and 3-O-galloyl-4,6-(S)-hexahydroxydiphenoyl-d-glucose (3OG46HG) of Euphorbia thymifolia Linnea have been shown to exhibit anti-herpes simplex virus (HSV)-2 activity in vitro. In the present study, we investigated the mode of action of these two compounds in suppressing HSV-2 multiplication. 2. The results demonstrated that the EtOAc extract and 3OG46HG affected virus infectivity in a dose-dependent manner. The EtOAc extract significantly reduced virus infectivity at a concentration of 4.0 microg/mL, whereas 3OG46HG obviously diminished virus infectivity at concentration of a 0.5 microg/mL. The virucidal ability of the EtOAc extract was affected by the incubation period, but not by the incubation temperature. In the case of the action of 3OG46HG against HSV-2, the effects of incubation time and temperature were negligible. 3. In summary, the EtOAc extract and 3OG46HG of E. thymifolia are concluded to inhibit HSV-2 multiplication by reducing virus infectivity.