Antiviral activity of a derivative of the photosensitive compound Hypericin

Eight synthetic compounds related to the photosensitive antiviral quinonic plant compound hypericin were screened for light-mediated antiviral activity. The compound 2,5,9,12-tetra(carboxyethylthiomethyl) hypericin was found to have activity against membrane-enveloped Sindbis virus and murine cytomegalovirus but not against the non-enveloped poliovirus. The activity of this compound was investigated in more detail. The mechanism of action appeared to be of the photosensitive singlet oxygen type and the activity could be reduced by the presence of a singlet oxygen quencher molecule. The membrane proteins of Sindbis virus were found not to be altered by treatment with this compound or hypericin, although the derivative did affect the electrophoretic mobility of the capsid protein.