in vitro evaluation of antiviral activity of essential oil from zataria multiflora boiss. against newcastle disease virus

introduction: the study aimed to investigate the antiviral activity of zataria multiflora (zm) essential oil against newcastle disease virus (ndv) on vero cells. methods: the cytotoxicity of zm essential oil was evaluated by mtt assay. cells were infected with 100 tcid50 of a field isolate of virulent ndv (jf820294.1). zm essential oil at concentrations of 1/5000, 1/25 000, 1/125 000 or 1/625 000 was added at different times of infection: 60 minutes pre infection, simultaneously and 60 minutes post infection. cells were evaluated morphologically. the tcid50, neutralizing index (ni) and ha titer were determined. results: cells treated with zm essential oil in all concentrations 1 hour before or after infection, showed cpe similar to control virus cells. in simultaneous use, cells treated with 1/5000 concentration of the essential oil, remained morphologically normal. tcid50 values of all treatments were very close to that of control virus except for simultaneous administration at concentration of 1/5000 which was about 1000 folds lower. virus titer in different treatments was exactly the same as control virus titer in haemagglutination (ha) test. conclusion: zm essential oil has some antiviral activity on ndv in vitro, which is possibly by destruction of virus infectivity or inhibition of early phases of viral proliferation cycle.