Essential oils (EOs) of Thymus species have been known to possess antimicrobial properties and therefore are of
great interest in pharmaceutical, food and cosmetic industry. However, they are poorly
soluble in water, unstable and susceptible to degradation. Encapsulation of EOs in
different nanocarriers represents a valid strategy to overcome these limitations as
well as to enhance their biological activity [1], [2]. The present study aimed to evaluate the antibacterial potential of liposomally-encapsulated
phenol rich EOs from T. longicaulis C. Presl, T. pulegioides L. and T. vulgaris L. originating from Croatia. The commercial T. vulgaris EO was used for the optimization of liposomes’ composition and preparation procedure.
Based on the high encapsulation of EO and satisfied physical properties achieved,
liposomes containing 20 mg/mL of soy phosphatidylcholine, 2 mg/mL of cholesterol and
5 mg/mL of EO were selected as optimal for testing the antibacterial activities against
S. aureus, E. faecalis and E. coli. The mean diameters of liposomes were 187–216 nm with polydispersity indexes from
0.43 to 0.53, while encapsulation efficiency varied between 51% and 57%. The obtained
minimal inhibitory concentrations (MICs) were in the range 0.25–2 mg/mL. Encapsulation
of the Thymus EOs in liposomes improved their solubility, stability and enhanced their antibacterial
activities exhibiting MICs two-fold lower than the MICs of the corresponding pure
EOs against S. aureus and E. coli. Liposomally-encapsulated T. longicaulis EO demonstrated the strongest antibacterial effect showing four-fold increase of
activity against E. faecalis, thus indicating its potential use as biopreservative and natural remedy.
