Antiviral effect of pyridinium formate, a novel component of coffee extracts.

N-methyl-pyridinium formate, a novel component of coffee extracts, inhibited the multiplication of both DNA and RNA viruses. In the presence of the compound, the progeny viral yields of both herpes simplex virus type 1 (HSV-1) and poliovirus in HEp-2 cells and those of influenza virus type A in MDCK cells decreased with increasing concentrations of the compound, although the degree of viral sensitivity to this compound differed. In addition, none of these viruses were directly inactivated by the compound at the concentrations tested. Characterization of the mode of action of this compound against HSV-1 multiplication revealed that it inhibits the viral growth primarily at the initial step of virus multiplication, i.e., within 2 h after the onset of multiplication, although the virus multiplication was affected by the compound throughout the multiplication cycle. In addition, this compound showed a significant cytotoxic effect, although the observed antiviral effect was unlikely to be attributed to the cytotoxic effect.