Chemical characterization and antibacterial activity of Thymus moroderi and Thymus piperella essential oils, two Thymus endemic species from southeast of Spain

The aim of this work was to determine the following characteristics of the essentials oils (EOs) obtained from two Thymus endemic species such as Thymus moroderi and Thymus piperella: (i) their chemical composition and (ii) their effect on the growth of several bacteria related to food spoilage, such as Listeria innocua, Serratia marcenscens, Pseudomonas fragi, Pseudomonas fluorescens, Aeromonas hydrophila, Shewanella putrefaciens, Achromobacter denitrificans, Enterobacter amnigenus, Enterobacter gergoviae, Alcaligenes faecalis and Leuconostoc carnosum. The EOs were chemically analysed and identified by GC and GC–MS, while the agar disc diffusion method was used to determine their antibacterial activities. The concentration effect was also determined. The major constituents of T. moroderi EO were camphor (26.74%), 1,8-cineol (24.99%) and myrcene (5.63%). In the T. piperella EO the main constituents were carvacrol (31.92%), para-cymene (16.18%) and γ-terpinene (10.11%). T. piperella EO was much more effective than T. moroderi EO, and had a much greater effect on the Gram-positive bacteria than on the Gram-negative bacteria.