Investigation of chemical compounds and antibacterial activity of pennyroyal, mint and thyme essential oils

Nowadays, considering the undesirable effects of chemical antimicrobials on human health and the growing willingness of consumers to consume natural ingredients, efforts to replace synthetic preservatives with naturally occurring forms are increasing. Because one of the best sources of antimicrobial compounds is the plant compounds, in the present study, the three essential oils of pennyroyal, mint and thyme were identified as an effective antimicrobial compound. GC / MS was used for the analysis and identification of essential oils of pennyroyal, mint and thyme. The antibacterial properties of these essential oils were investigated on some Gram-Negative and Gram-Positive bacteria compared with the common antibiotics. Such as chloramphenicol and tetracycline using disc diffusion method. In this study, 40 compounds were identified in thyme essential oil which thymol (30.61%), carvacrol (22.18%), p-cymene (37.34%), gama-terpinene (66.6%), and linalool (5.26%) were the major components. 31 chemical compounds were identified in pennyroyal essential oil that piperitone (32.16%), piperitenone (29.62%) and alpha-terpineol (6.40%) were the main constitutes. In addition, 27 compounds were identified in the mint essential oil that carvon (51.03%) and limonene (21.12%) were the major oil compounds. The results of this study showed that Gram-Positive bacteria were more susceptible to the essential oils than Gram-Negative bacteria. In addition, thyme essential oil has a more inhibitory effect compared to pennyroyal and mint oil, which is probably due to the presence of more thymol and carvacrol in leaves of this plant. The results of this study revealed that thyme essential oil could be used as natural preservative in foods.