Antimicrobial activity, cytotoxicity and bioactive constituents by GC/MS analysis of essential oils

Abstract

Objectives: The study objective was to select natural essential oils that can act as antimicrobial and flavoring agents, to determine the antimicrobial effect, and to evaluate the possibility of its use as a component of mouthwash through toxicity evaluation. Methods: Disc-diffusion test, Minimal inhibition concentration (MIC) and Minimum bactericidal concentration (MBC) were measured to evaluate the antimicrobial effect against Streptococcus mutans and Candida albicans by selecting Cinnamon bark, Lemongrass, Clove bud, Tea tree, Eucalyptus and Girofle (Clove) from natural essential oils commercially available. By analyzing the exact components by gas chromatography mass spectrometry (GC/MS) of six kinds of essential oils, it was possible to identify the major components showing antimicrobial effect. Cell cytotoxicity test was performed using Agar overlay test oil which showed excellent antibacterial effect against Streptococcus mutans and Candida albicans. Findings: The antimicrobial effect of C. albicans was measured among S. mutans and oral flora causing periodontal disease, and Cinnamon bark and Lemongrass oil showed the highest MBC of 3.13 mg/mL (0.313%), followed by Girofle (Clove) and Clove bud oil (MBC: 6.25 mg/mL (0.625%)) showing significant antimicrobial effects. The major components were identified by analyzing the ingredients using GC-MS. Cinnamon bark was identified as cinnamaldehyde and eugenol, and Lemongrass was identified as a major ingredient of antimicrobial activity through the analysis of essential oils, such as citral components, neral and geranial, and Girofle (Clove), eugenol. It was confirmed that information on the concentration of major components can be obtained according to the concentration used and the evaluation of the antimicrobial effect can be accurately performed. The concentration of MBC (0.313%) of cinnamon bark oil measured in this experiment was higher than the recommended concentration of not more than 0.1%. Therefore, the toxicity test was carried out with an agar overlay test according to the concentrations of Lemongrass and Girofle (Clove) essential oils known to be non-toxic and found to be non-toxic at concentrations below 0.313%. Improvements/Applications: Antimicrobial activity and safety evaluation of Lemongrass and Girofle (Clove) oils were able to determine the optimum concentration for use. These natural oils have an antibacterial effect against C. albicans in S. mutans and oral flora, and it is expected that further research on other pathogenic bacteria and oral flora of periodontal disease and component analysis and safety evaluation study can be applied to the development of safe and antimicrobial natural mouthwash.