Determining the Antibacterial Effect of Mentha Longifolia Essential Oil on Cariogenic Bacteria and Its Compounds: an in vitro Study

Statement of the Problem:

 Continuous use of chemical agents to reduce the number of cariogenic bacteria leads to adverse effects; therefore, in recent years, many studies have focused on plant-based substances.

This study explores the antibacterial effects of Mentha Longifolia (M. longifolia) essential oil on Streptococcus mutans (S. mutans), Streptococcus sobrinus (S. sobrinus), and Lactobacillus as cariogenic microorganisms and determines the compounds in it.

In this experimental study, S. mutans, S. sobrinus, and Lactobacillus isolates were collected from the saliva samples of five children with severe early childhood caries (S-ECC). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of M. longifolia essential oil were determined by Broth microdilution method. Chlorhexidine 0.2% and phosphate-buffered normal saline (pH= 7.0) were used as positive and negative controls, respectively. The chemical composition of M. longifolia essential oil was evaluated by gas chromatography-mass spectrometry. The data were analyzed with a paired t-test and the p below 0.05 was considered significant.

The MIC and MBC ratios for S. mutans were 3.12% and 6.25%, for S. sobrinus were 6.25% and 12.5%, ​​and Lactobacillus were 3.12% and 6.25%, respectively. Chemical analysis of M. longifolia essential oil showed that 34 various compounds. Piperitone oxide (27.59%), Transcariophylline (14.55%), and 2-cyclohexane-1-one (12.24%) were the major constituents.

M. longifolia essential oil has both growth inhibitory and bactericidal effects on all the three species of bacteria. This antibacterial effect was similar against S. mutans and Lactobacillus, which was greater than S. sobrinus, thus, it can be used as a supplementary for caries prevention compounds.