Antiviral effect of octyl gallate against DNA and RNA viruses

The effects of gallic acid (3,4,5-trihydroxybenzoic acid) and its alkyl esters on virus growth and virion infectivity were examined. All the compounds tested showed an inhibitory effect on the growth of herpes simplex virus type 1 (HSV-1) in HEp-2 or Vero cells. The antiviral activity of gallic acid alkyl esters was enhanced by increasing the number of carbon in the alkyl moieties of the compounds, reaching maximum at a carbon number of 12 (lauryl gallate), but both cytocidal activity and cytopathic effect of the compounds were also significantly increased simultaneously. Among these compounds, octyl gallate showed a marked antiviral effect with a relatively moderate cytotoxity. In addition, octyl gallate suppressed the multiplication of RNA viruses, such as vesicular stomatitis virus and poliovirus. Quantitative characterization of the HSV-1 infection in the presence of octyl gallate revealed that: (1) this reagent can directly inactivate HSV-1 (virucidal activity), (2) it suppresses both the intracellar multiplication and the release of the virus, (3) it selectively accelerates death of the virus-infected cells and (4) the addition of the reagent even at 6-h post infection completely abolishes the formation of progeny virus in the infected cells.