Nano-emulsion of denak (Oliveria decumbens Vent.) essential oil: ultrasonic synthesis and antifungal activity against Penicillium digitatum

Denak (Oliveria decumbens Vent.) is an endemic aromatic plant belonging to Apiaceae family. This study evaluated the antifungal activity of denak essential oil (EO) nano-emulsions formulated by ultrasonic emulsification on Penicillium digitatum, the main causal agent of postharvest decay of citrus fruit. EO chemical compositions detected by gas chromatography demonstrated that thymol (28.5%), carvacrol (26.2%), myristicin (17.5%) and elemicin (9.9%) were the dominant components. Denak EO nano-emulsions with droplet diameter of 26.9 nm formulated by ultrasonic emulsification. Inhibition of mycelial growth was observed at EO concentrations higher than 0.5 µL mL−1. The antifungal activity of the EO increased with increasing the concentration of EO. The minimal inhibitory concentration of EO nano-emulsion was found to be 0.5 µL mL−1. These results demonstrate the potential of ultrasonication for preparing denak EO nano-emulsion which could be used as a suitable treatment to control postharvest diseases caused by P. digitatum and possibly other pathogens. This newly formulated denak EO nano-emulsion can be applied as a useful treatment for prevention of citrus losses.