Comparison of antioxidant and antibacterial activities of various herbal essential oils: An In vitro study

Background and Aims: Herbal essential oils (EOs) have antimicrobial and antioxidant activities due to the high amount of bioactive compounds; therefore, they are considered good candidates for applications in the food and pharmaceutical industries. The present study aimed to assess the total phenolic content and in vitro comparative study of the biological activities of EOs from different plants (e.g., clove, common sage, savory, and organum). Materials and Methods: In this experimental study, total phenolic content in EOs was determined, and their antioxidant capacity was measured by the DPPH free radical scavenging method. The components of essential oil were identified using a Gas chromatography-mass spectrometry (GC-MS) device. Moreover, the antibacterial activity of EOs was evaluated by the disk diffusion method, and minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were evaluated by the broth macro dilution method. Data were analyzed using one-way analysis of variance (ANOVA) and Duncan's multiple range test. Results: The highest content of total phenol (157.07±2.37 mg GAL/g dry weight) was recorded for EO of organum. Moreover, the highest percentage of free radical scavenging was determined at 98.142% for organum. The results of GC/MS analysis depicted that monoterpenes were the main compounds of Eos of organum, and the highest value was obtained for the alpha-pinene (74.04%). Furthermore, the results of antibacterial activity of EOs demonstrated that the highest zone of inhibition with a diameter of 44±0.81 mm was observed for the EO of organum. The lowest values of MIC and MBC were reported as 0.275 and 0.55 mg/mL for the EOs of organum and savory against gram-positive Bacillus cereus, respectively. Conclusion: As evidenced by the results of the current study, the assessed Eos, specifically those of organum, have effective antioxidant and antibacterial activity against bacteria strains, especially gram-positive ones, and can be used as safe antimicrobial compounds in food and health products.