The antimicrobial activity of several essential oils (EOs) and their related microemulsions
(MEs) was investigated. EOs were obtained from Cannabis sativa L. cv CS (C. sativa), Carum carvi L.
(C. carvi), Crithmum maritimum L. (C. maritimum), Cuminum cyminum L. (C. cyminum), x Cupressocyparis
leylandii A.B. Jacks & Dallim. (C. leylandii), Cupressus arizonica Greene (C. arizonica), Ferula assafoetida
L. (F. assa-foetida)., Ferula gummosa Boiss. (F. gummosa), Juniperus communis L. (J. communis),
Juniperus x pfitzeriana (Spath) P.A. Schmidt (J. pfitzeriana), Pimpinella anisum L (P. anisum). Preliminary
screening revealed that Cuminum cyminum, Crithmum maritimum, and Pimpinella anisum
(10%v/v) were effective against all tested microorganisms (Escherichia coli ATCC 35218, Listeria monocytogenes
ATCC 7644, Staphylococcus aureus ATCC 29213, Pseudomonas fluorescens DSM 4358, and
Candida albicans ATCC 10231), with growth inhibition diameter from 10 to 25 mm. These EOs were
used to formulate the MEs with an average size <50 nm and a good stability over 30 days. EOs’
antimicrobial activity was further enhanced in the MEs, with a generalized lowering of minimum
inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values. C. cyminum-
ME reached, in most cases, MIC two times lower (0.312%) than the corresponding EO (0.625%) and
even eight times lower against S. aureus (0.156 vs. 1.25%). A more remarkable microbicide effect was
noted for C. cyminum-ME, with MBC values eight times lower (from 0.312 to 0.625%) than the corresponding
EO (from 2.5 to 5%). Overall, MEs resulted in an efficient system for EOs encapsulation,
enhancing solubility and lowering concentration to exert antimicrobial efficacy.