Preparation, characterization, optimization, and antibacterial evaluation of nano-emulsion incorporating essential oil extracted from Teucrium polium L

This study was aimed at optimizing the conditions for producing oil-in-water nanoemulsion based on Teucrium polium L. essential oil (TP-EO) with high-pressure homogenization method using mixture of surfactants Tween 80 (Tw80) and Span 20 (Sp20). The experiment was designed based on the Box-Behnken method and the effect of % Sp20, Tw80:Sp20, and %TP-EO on size, polydispersity index (PDI) and zeta potential (ZP) of the prepared nano-emulsions were determined. Micro-broth dilution assay was utilized to determine the in vitro antibacterial effect of the optimized formulation of TP-NE. The results revealed that more desirable TP-NE with minimum particle size (153.75 +/- 1.34 nm) and PDI (0.04 +/- 0.003) and maximum ZP (-6.44 +/- 0.13 mV) were obtained using 0.16%Sp20, 12 Tw80:Sp20 and 0.5%TP-EO. Furthermore, TP-NE had high growth inhibitory effect on S. aureus and MRSA, with IC50 of 8.73 +/- 0.07 and 9.38 +/- 0.07% (v/v), respectively. In addition, TP-EO inhibited the growth of P. aeruginosa, S. sonnei, E. coli, and K. pneumonia, with IC50 of 10.83 +/- 0.09, 16.62 +/- 0.1, 20.50 +/- 0.2, and 28.64 +/- 0.12% (v/v), respectively. The viabilities of S. aureus and MRSA treated with 16.67% (v/v) TP-NE were significantly reduced by 6.88 and 2.3-folds, respectively, relative to when they were treated with equivalent concentration of TP-EO. The growths of P. aeruginosa, E. coli, K. pneumonia, and S. sonnei, were inhibited 3.95, 2, 1.16, and 1.10-fold, respectively, after treatment with 16.67% (v/v) TP-NE, when compared with TP-EO-treated groups. In conclusion, the optimized TP-NE has antibacterial activity above that of pure oil.