The inhibitory effect of
Lippia alba
and
Lippia citriodora
essential oils
on dengue virus serotypes replication in vitro was investigated. The cytotoxicity (CC
50) was evaluated by the MTT assay and the mode of viral
inhibitory effect was investigated with a plaque reduction assay. The virus was treated with the essential oil for 2 h at 37°C before cell
adsorption and experiments were conducted to evaluate inhibition of untreated-virus replication in the presence of oil. Antiviral activity
was defined as the concentration of essential oil that caused 50% reduction of the virus plaque number (IC
50).
L. alba oil
resulted in less cytotoxicity than
L. citriodora oil (CC
50: 139.5 vs. 57.6 μg/mL). Virus plaque reduction for all four dengue
serotypes was observed by treatment of the virus before adsorption on cell. The IC
50 values for
L. alba oil were between
0.4-32.6 μg/mL and between 1.9-33.7 μg/mL for
L. citriodora oil. No viral inhibitory effect was observed by addition of the essential
oil after virus adsorption. The inhibitory effect of the essential oil seems to cause direct virus inactivation before adsorption on host cell.
