Antiviral activity of the oseltamivir and Melissa officinalis L. essential oil against avian influenza A virus (H9N2).

Lemon balm derivatives are going to acquire a novelty as natural and potent remedy for treatment of viral infections since the influenza viruses are developing resistance to the current antivirals widely. Oseltamivir, Melissa officinalis essential oil (MOEO) and their synergistic efficacy against avian influenza virus (AIV) subtype H9N2 were evaluated in vitro in MDCK cells at different time exposure by using TCID50, HA, Real Time PCR and HI assay. The results showed that MOEO could inhibit replication of AVI through the different virus replication phase (P ≤ 0.05). Also the highest antiviral activity of MOEO was seen when AIV incubated with MOEO before cell infection. The TCID50/ml was reduced 1.3-2.1, 2.3-2.8, 3.7-4.5 log 10 than control group (5.6 log 10), HAU/50 µl was decreased 85-94, 71.4-94, 71.4-94 % and viral genome copy number/µl was brought down 68-95, 90-100, 89.6-99.9 % at pre-infection, post-infection and simultaneous stage, respectively. Hemagglutination inhibition result showed the MOEO was not able to inhibit agglutination of the chicken red blood cell (cRBC). Replication of the AVI was suppressed by the different concentration of oseltamivir completely or near 100 %. Also oseltamivir showed a synergistic activity with MOEO especially when oseltamivir concentration reduced under 0.005 mg/ml. The chemical composition was examined by GC-MS analysis and Its main constituents were identified as monoterpenaldehydes citral a, citral b. In conclusion, the findings of the study showed that lemon balm essential oil could inhibit influenza virus replication through different replication cycle steps especially throughout the direct interaction with the virus particles.