Background: Lemon balm (Melissa officinalis) is one of the most valuable species of Labiateae family. In order to optimize producing secondary metabolisms in balm, the study was conducted to examine producing of dried material and medicinal substances by using methanol and MgSO4 spraying.

Objective: According to provide maximum photosynthesis potential  through new carbon and Mg sources and reduce loss of metabolic energies, it is probable to have maximum active substance by using the best recommendation of methanol and MgSO4 spraying on Melissa officinalis.

Methods: A factorial experiment using the randomized complete design was conducted in the Science and Research Unit of the Islamic Azad University in 2013 with 12 treatments and 3 replications. The factors included 4 levels of methanol (0, 10, 20, and 40%) and 3 levels of manganese sulfate (0, 0.5, and 1 g/l). After seedling transplantation and establishment, methanol was sprayed three times at 15-intervals at midday (one of these sprays was carried out together with the first methanol spray). At the start of flowering, plant organs were harvested and foliage extraction was performed. The essential oil in each treatment was analyzed using GC and GC/MS.

Results: The table of ANOVA showed the mutual effects of methanol and manganese sulfate on percentage essential oil and on its performance were significant at the 1% probability level.

Conclusion: Results of GC and GC/MS indicated the maximum percentages of lemon balm essential oil constituents were those of the treatment in which 40% methanol and 0.5 g/l manganese sulfate were applied.