Nanoencapsulation of Zataria multiflora essential oil preparation and characterization with enhanced antifungal activity for controlling Botrytis cinerea, the causal agent of gray mould disease

• Preparation and characterization of Zataria multiflora essential oil (ZEO)-loaded chitosan nanoparticles (CSNPs) have been studied.
• Nanoencapsulation of ZEO enhanced the antifungal activity against Botrytis cinerea.
• The mechanism involved in the ZEO release from ZEO@CSNP displayed Fickian kinetics.
• ZEO loaded in CSNPs completely inhibited in vitro fungal growth at 1500 ppm.
• In vivo trials confirmed the strong antifungal efficacy of ZEO@CSNPs treatment.

This study was undertaken to investigate the nanoencapsulation of Zataria multiflora essential oil (ZEO) in chitosan nanoparticles (CSNPs) in order to enhance antifungal activity and stability of the oils against one isolate of Botrytis cinerea Pers., the causal agent of gray mould disease. ZEO was encapsulated by an ionic gelation technique into CSNPs with an average size of 125–175 nm as observed by transmission electron microscopy (TEM). From UV-vis spectrophotometry results, the drug encapsulation and loading efficiency of ZEO decreased from 45.24% to 3.26% and from 9.05% to 5.22%, respectively, upon increasing initial ZEO content from 0.25 to 1 g/g chitosan. In vitro release studies also demonstrated a controlled and sustained release of ZEO for 40 days. The superior performance of ZEO when encapsulated by CSNPs under both in vitro and in vivo conditions in comparison with unmodified ZEO against B. cinerea was revealed. The in vivo experiment also showed that the encapsulated oils at 1500 ppm concentration significantly decreased both disease severity and incidence of Botrytis-inoculated strawberries during 7 days of storage at 4 °C followed by 2–3 more days at 20 °C. These findings revealed the promising role of CSNPs as a controlled release system for EOs in order to enhance antifungal activities.Industrial relevance: Application of plant essential oil (EOs) treatment at pre- or postharvest stage has been considered as an alternative treatment to the use of synthetic fungicides to prevent fruit postharvest decay and to extend the storage life while retaining the overall quality of different fresh commodities. Although EOs have proved to be good antimicrobial agents, their use for maintaining fruit quality and reducing fungal decay is often limited due to their volatile compounds which can easily suffer degradation under the action of heat, pressure, light and oxygen. Furthermore, they are insoluble in water, and for certain applications a controlled release is required. In this regard, nano-size carriers provide more surface area and can possibly upgrade solubility, enhance bioavailability and improve controlled release and targeting of the encapsulated food ingredients, in comparison to micro-size carriers. These findings revealed the promising role of CSNPs as a controlled release system for EOs in order to enhance their antimicrobial activities.