Abstract

Objective: To evaluate the antiviral activity of Melissa officinalis (MO) extract against the influenza virus H1N1 in vitro. Methods: The cytotoxicity of MO extract was identified on Madin-Darby canine kidney (MDCK) cell culture by MTT assay. The virus was inoculated to the cells (multiplicity of infection = 0.1) in two protocols. In protocol 1, the MO extracts at concentrations of 0.005, 0.050, 0.010, 0.100 and 0.500 mg/mL were incubated with the virus for one hour preinoculation. In protocol 2, the mentioned concentrations of MO extracts were added to the cells one-hour post infection. Furthermore, the antiviral effect of oseltamivir with different concentrations was tested as the positive controls. The 50% tissue culture infective dose, neutralizing index and hemagglutination titer were determined. Results: The medicine oseltamivir and MO extracts were not toxic for MDCK at concentrations less than 1 mg/mL. All utilized concentrations of MO extracts were vigorously efficient to decrease the viral yield in both experiments. The 50% tissue culture infective dose of the groups containing up to 0.100 mg/mL of MO extracts in the first experiment in compare with 0.050 mg/mL in the second experiment reduced to 0. Although hemagglutination tests showed little titers, the viral quantity significantly decreased in both experiments. By the way, the medicine oseltamivir could completely suppress viral replication in MDCK. Conclusions: The present study suggests that MO extracts have a potent anti-influenza effect in cell culture.

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