Comparison of chemical composition and antimicrobial activities ofMentha longifolia L. ssp.longifolia essential oil from two Tunisian localities (Gabes and Sidi Bouzid)

Abstract

This study was conceived to evaluate the difference in the chemical composition of the essential oil ofMentha longifolia ssp.longifolia from two ecotypes (Sidi Bouzid and Gabes) as well as the difference of the composition of the oils extracted from the leaves and stems. The antimicrobial activity was also tested against 16 human pathogenic microorganisms. The chemical composition of the hydrodistilled essential oils ofMentha longifolia ssp.longifolia were analysed by GC and GC/MS system. Remarkable differences were recorded between the percentages of the few constituents from leaves and stems and between plants from the two geographical provinces. The chemical analysis of the essential oil obtained from leaves and stems showed the presence of 34 compounds. The most important ones were consecutively: 1,8-cineole (5.6–10.8%), menthone (20.7–28.8%), terpineol-4 (3.1–4.9%), menthol (19.4–32.5%), pulegone (7.8–17.8%) and piperitone (2.2–3.3%). These major components occur in different amounts depending on the organs (leaves or stems) and the geographical origin of the plant. The antimicrobial activity of the essential oil was tested using the disc-diffusion assay and minimal inhibition concentration (MIC) values were estimated according to the microdilution method. The results showed that the essential oil ofMentha longifolia ssp.longifolia had great potential of antimicrobial activity against all 8 bacteria and 8 yeast species tested. The (MIC) for bacteria was ranging from 0.195 to 3.12 × 103 μg/ml.