Light-mediated activities of thiarubrines against human immunodeficiency virus

Two thiarubrines (dithiacyclohexadienes), which were isolated recently from species of Asteraceae, were investigated for light-mediated antiviral activity against human immunodeficiency virus (HIV-1). Both compounds (thiarubrines A and D) showed good anti-HIV activity, in micromolar concentrations, which was dependent upon UVA radiation. They showed no anti-viral activity in the dark, and only weak visible light-mediated activity, despite the significant absorbance of these compounds in the 480 nm region. The resulting inactivated virus was unable to replicate in cell cultures, as indicated by loss of cytopathogenicity, the absence of cells expressing HIV-1 antigens and lack of production of HIV-1 p24 protein. Although this antiviral activity was not as efficient as that shown by the photoactive plant thiophene, alpha-terthienyl, both thiarubrines demonstrated increased activity when the serum component of the virus stock was reduced. This suggested that a component of bovine serum interfered to some extent with the anti-HIV activity.