Essential oils in nanocarriers: sustainable solution for waste and food management within a one health approach

Essential oils (EOs), natural compounds with high chemical complexity, are characterized by a wide range of bioactive molecules. This thesis aims to explore their potential use in different fields, such as pharmaceuticals, food, environmental, and agricultural sectors. These applications align with the One Health concept, which promotes an integrated approach to human, animal, and environmental health, thanks to EO properties such as antibacterial and antioxidant activities. However, despite their numerous positive aspects, essential oils have some intrinsic limitations. They are highly susceptible to environmental conditions such as light, oxygen, and heat, which compromise their stability. Additionally, their volatile, hydrophobic nature and strong irritating activity make their direct use impractical. To overcome these limitations, it is necessary to dilute and encapsulate them in nanocarriers—structures designed to protect them and enhance their bioactivities. The research presented in this thesis aim to evaluate their efficacy in different but complementary contexts. Specifically, nanoemulsions based on Thymus essential oil were prepared and characterized from a physicochemical perspective, with the goal of formulating a sprayable formulation to treat compost. Compost, being obtained through bacterial fermentation of food waste, is characterized by the presence of numerous microorganisms. Among these, some can be pathogenic and cause diseases. Another drawback of compost is its characteristic unpleasant odor, which limits its application in more sensitive contexts. To address these issues, this study tested Thymus essential oil-based nanoemulsions to reduce the microbial load and improve its odor. Subsequently, the efficacy of liposomes capable of simultaneously carrying Thymus essential oil and resveratrol was evaluated against infections caused by Listeria spp., pathogens of public health relevance. The listeriosis is a severe disease characterized by symptoms ranging from gastrointestinal disturbances to invasive infections such as meningitis, sepsis, and spontaneous abortion. The ability of Listeria spp. to survive extreme environmental conditions, makes these bacteria particularly problematic and capable of forming biofilms that are difficult to eradicate. Treating contamination and eliminating biofilms on foods is essential to protect public health, but the excessive use of conventional antimicrobials has led to the emergence of resistant strains, making alternative and sustainable solutions necessary. For this purpose, liposomes containing Thymus essential oil and resveratrol were formulated and characterized. Another area of study focused on the use of formulations, specifically chitosan- and soy lecithin-based nanoformulation containing essential oils such as fennel and basil essential oils, to develop an edible coating capable of extending the shelf life of tomatoes, preserving their freshness and reducing deterioration, with the aim of minimizing food waste. Finally, a study was conducted to understand the interaction mechanism between Satureja essential oil and phospholipid monolayer membranes, which represent simplified models of cellular membranes, using lipids with different polar heads and structures such as DMPC, DMPE, DMPG, and cardiolipin. Through the Langmuir monolayer technique, complemented by fluorescence anisotropy and differential scanning calorimetry on lipid bilayers, the packing conditions of the monolayers were studied. The comprehensive analysis of the results demonstrated that essential oils, thanks to their versatile chemical composition and the protection provided by nanocarriers, possess broad application potential in various fields such as public health, food safety, and environmental protection. This confirms the importance of a multidisciplinary and integrated approach to address global health challenges.