chemical composition and in vitro antibacterial activity of native men tha longifolia essential oil from ardabil, iran on streptococcus mutans, lactobacillus rhamnosus and actinomyces viscosus

background: most of the population in the different areas of world is affected by bacterial infections responsible for dental caries. due to the importance of traditional medicines derived from herbs used for dental problems, this study investigated in vitro antibacterial activity of mentha longifolia essential oil from ardabil, iran, on streptococcus mutans, lactobacillus rhamnosus and actinomyces viscosus,bacteria that cause tooth decay. materials and methods: the volatile oil of mentha longifolia leaves was extracted by hydrodistillation method using a clevenger-type apparatus  and analyzed by gc and gc/ms system.the antibacterial activity was evaluated by the disk diffusion susceptibility in dilutions of 62.5, 125, 250, 500, 1000 and 2000μg/μl and broth macrodilution test methods. results: the oil was particularly rich in pulegone (31.78%), 1,8-cineole (15.99%), menthoforan (11.25%), cis-isopulegon (10.5%) and paramenth-3-n-8-l (6.85%). the medicinal plant essential oil could prevent the growth of the bacteria, and the rates of mic and mbc of native pennyroyal essential oil on streptococcus mutans, lactobacillus rhamnosus and actinomyces viscosus were 110, 165, 80, 120, 450 and 650μg/μl, respectively. the maximum inhibition zone diameter was about 12.2, 27.2 and 4.8 mm, for streptococcus mutans, lactobacillus rhamnosus and actinomyces viscosus respectively, at the concentration of 500μgμl-1. conclusion: in this work, the essential oil of medicinal plant containing effective ingredients could prevent the growth of bacteria and may be used as an affordable and available source for medicinal purposes.