Antiviral activity of the photoactive plant pigment hypericin.

The polycyclic compound hypericin, a known photodynamic agent, was investigated for antiviral activity in the presence and absence of light. The three viruses tested: murine cytomegalovirus; Sindbis virus; and human immunodeficiency virus type 1, were all susceptible to hypericin; but these antiviral activities were considerably enhanced, in a dose-dependent manner, by exposure to light.