Chemical composition and in vitro antibacterial activities of Cuminumcyminum L. and Eucalyptus globulus essential oil extracts against three lactobacillus strains

Antibacterial agents are considered one of the adjuncts for caries prevention. Due to side effects and bacterial resistance with the use of chemical agents, use of herbal medications has attracted a lot of attention. This study evaluated the antibacterial effects of essential oil extracts of C. cyminum L. and E. globulus against three common oral lactobacilli involved in tooth caries. In this study, essential oils were extracted by hydrodistillation. C. cyminum L. and E. globulus were characterized by means of gas chromatography‒mass specrtophotometry (GC‒MS). Antibacterial activity indices including MIC, MBC and zone of inhibition for the above essential oils against three bacterial strains (Lactobacillus casei, Lactobacillus plantarum and Lactobacillus rhamnosus) were determined using broth macrodilution and agar well diffusion methods. Data analysis was performed using one-way ANOVA and Tukey HSD tests (α=0.05). The main components of the essential oils of C. cyminum L. and E. globulus were cuminic alcohol (30.23%) and 1.8 cineol (40.18%), respectively. MIC for all the bacterial strains was 6.71 μg/mL for C. cyminumand and 110 μg/mL for E. globulus. MBC values for L. casei, L. plantarum and L. rhamnosus were 13.43 μg/mL, 26.87 μg/mL and 26.87 μg/mL for C. cyminum and 110 μg/mL, 220 μg/mL and 110 μg/mL for E. globulus, respectively. An increase in the concentration of essential oils resulted in an increase in zone of inhibition (p value = 0). In both essential oils the maximum zone of inhibition was observed at a concentration of 880 mg/mL. L. casei had maximum and L. plantrum had minimum sensitivity to these oils (p value = 0.02). Zones of inhibition at different time intervals (24-48 h) showed no significant differences (p value = 0.78). Zone of inhibition of C. cyminum was more than that of eucslyptus (p value = 0.02). Both essential oils exhibited antibacterial effects against the bacterial strains evaluated. C. cyminum had higher antibacterial efficacy.