The Plant-Derived Naphthoquinone Droserone Inhibits In Vitro Measles Virus Infection

Abstract

The naphthoquinone droserone (<b>1</b>) is a natural product occurring in dicotyledonous plants. We have now observed that the addition of <b>1</b> during infection of tissue culture cells with measles virus considerably reduced the infection. Interestingly, the infection was inhibited only when droserone (<b>1</b>) was added during virus entry, but not when added to the cells prior to virus uptake or after virus uptake. These findings suggest that <b>1</b> interacts with viral particles to reduce infectivity. The formation of progeny measles virus particles was inhibited to 50 % by droserone (<b>1</b>) at a concentration (IC₅₀) of approximately 2 µM with a half-maximal cytotoxicity (CC₅₀) of about 60 µM for Vero cells. Other tested naphthoquinone derivatives, among them the likewise natural plumbagin (<b>2</b>), but also synthetic analogs, were either more cytotoxic or not as effective as <b>1</b>. Thus, our data do not support the development of naphthoquinone derivatives into antiviral compounds, but suggest that they may be interesting research tools to study measles virus entry into cells.