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 Stöber 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 (MIC(90)) and minimum effective (MEC(10)) 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.