Pennyroyal (Mentha pulegium L.) is an important medicinal plant of the family Lamiaceae. It is native species of Europe, North Africa and in Asia Minor and near East. Leaves, flowers and the stems of Pennyroyal are frequently used due to their antiseptic properties. The major components of Mentha pulegium essential oil are menthone and pulegone. Viruses that infect plants are responsible for reduction in both yield and quality of crops around the world, and are thus of great economic importance. Tobacco mosaic virus (TMV) one of the most important viruses infecting vegetables and ornamental plants. Nicotiana tabacum is particular importance in the historiography of TMV. The antiviral effect of pennyroyal against TMV was studied in Nicotiana tabacum model plants. under controlled conditions (16:8 h L:D at 25 ± 1 C and 65 ± 5% RH). The ethanolic extracts of pennyroyal were prepared. Five concentrations (0%, 1.25%, 2.5%, 5%, and 10%) were used with the control, which was treated with ethanol. This project was designated in a experiments based on completely randomized design with three replication. DAS-ELISA (double antibody sandwich ELISA) was used with a polyclonal antiserum to determine the viral infection in model plants. A 200 µl aliquot of IgG was added to coat each well of plates. Each step of ELISA was followed by a 4-hr incubation at 37ºC or a 12-hr incubation at 4ºC. This was followed by three washes with a washing buffer. Ten milliliters of sample buffer, pH 7.4, was added to 1gr tissue samples that had been ground in liquid nitrogen, and 200 µl of this extracted was added to each well. The reaction was read using a colorimeter at 405 nm after adding conjugate incubation with substrate for about one hour. Results of serological assay showed lower absorbance values for the pennyroyal treated samples as compared with non-treated. Also the ethanolic extract of pennyroyal, at level of 0.10, had an inhibitory effect against TMV infection in tobacco model plants wi
