In-vitro antimicrobial activity and chemical composition of Sardinian Thymus essential oils

Essential oils and their components are becoming increasingly popular as na turally occurring antimicrobial agents. In this work the chemical compositi on and the antimicrobial properties of Thymus essential oils and of their m ain components were determined. Three essential oils obtained from differen t species of Thymus growing wild in Sardinia and a commercial sample of Thy mus capitatus oil were analysed. The essential oil components were identifi ed by GC/MS analysis. The antimicrobial activity of the oils and components was determined against a panel of standard reference strains and multiple strains of food-derived spoilage and pathogenic bacteria, using a broth mic rodilution method. The GC/MS analysis showed that the major constituents of the oils were monoterpene hydrocarbons and phenolic monoterpenes, but the concentration of these compounds varied greatly among the oils examined. Th e results of the antimicrobial assay showed that essential oils extracted f rom Sardinian Thymus species have an antimicrobial activity comparable to t he one observed in other thyme oils. It seems also confirmed that the antim icrobial properties of thyme essential oils are mainly related to their hig h phenolic content. Among the single compounds tested carvacrol and thymol turned out to be the most efficient against both reference strains and food -derived bacteria. The results of this study confirmed the possibility of u sing thyme essential oils or some of their components in food systems to pr event the growth of foodborne bacteria and extend the shelf-life of process ed foods.