The comparison of antimicrobial and antioxidant activity of essential oil of Oliveria decumbens and its nanoemulsion preparation to apply in food industry

The aim of this study was to compare the antibacterial and antioxidant effects of essential oil (Od-EO) and nanoemulsion (Od-NEO) of Oliveria decumbens for practical use in food industry. The plant was collected from the North-East of Khuzestan province and essential oil was extracted by Clevenger device. The components of Od-EO were identified by GC–MS analysis. The Od-NEO was prepared by stirring tween 80, distilled water and Od-EO and then using a sonicator with a power of 200 W and a piezoelectric crystal with a probe diameter of 15 mm. The antibacterial effects of Od-EO and Od-NEO were evaluated on Escherichia coli O157:H7, Pseudomonas aeruginosa, Staphylococcus aureus and Listeria monocytogenes by disk diffusion agar and microdilution methods. Antioxidant effect was also evaluated using DPPH and ABTS scavenging methods. Data showed that thymol (53.4%), γ-terpinene (20.48%), p-cymene (18.02%) and myristicin (2.7%) were the most predominant compounds of Od-EO. The particle size of Od-NEO was 45.71nanometer and the Zeta potential was -36.3 mV. The value of IC50 in the DPPH test for BHT, Od-EO and Od-NEO were 18.57, 1456.95 and 757.29 (μg/ml), respectively. In ABTS method, the IC50 rates were 12.32, 565.83 and 507.89 (μg/ml). The MIC of the Od-EO and Od-NEO ranged between 0.312 to 20 mg/ml. The lowest MIC value was obtained for S. aureus and highest value was obtained for P. aeruginosa. Data showed that the antioxidant activity of Od-NEO was significantly higher than Od-EO (p<0.05). Also, Od-NEO had a greater inhibitory effect on the studied bacteria than Od-EO and gram positive bacteria showed more sensitivity. Due to higher antioxidant and antimicrobial properties of Od-NEO, need for increased attention to this issue and the Od-NEO could potentially be used in the food industry.