Antimicrobial Activity of Chamomile Essential Oil: Effect of Different Formulations.

Essential oils (EOs) are highly lipophilic, which makes the measurement of their biological action difficult in an aqueous environment. We formulated a Pickering nanoemulsion of chamomile EO (C-Pe). Surface-modified Stober silica nanoparticles (20 nm) were prepared and used as a stabilizing agent of C-Pe. The antimicrobial activity of C-Pe was compared with that of emulsion stabilized with Tween 80 (C-T80) and ethanolic solution (C-Et). The antimicrobial effects were assessed by their minimum inhibitory concentration (MIC90) and minimum effective (MEC10) concentrations. Besides growth inhibition (CFU/mL), the metabolic activity and viability of Gram-positive and Gram-negative bacteria as well as Candida species, in addition to the generation of oxygen free radical species (ROS), were studied. We followed the killing activity of C-Pe and analyzed the efficiency of the EO delivery for examined formulations by using unilamellar liposomes as a cellular model. C-Pe showed significantly higher antibacterial and antifungal activities than C-T80 and C-Et. Chamomile EOs generated superoxide anion and peroxide related oxidative stress which might be the major mode of action of Ch essential oil. We could also demonstrate that C-Pe was the most effective in donation of the active EO components when compared with C-T80 and C-Et. Our data suggest that C-Pe formulation is useful in the fight against microbial infections.