Microemulsions: an effective encapsulation tool to enhance the antimicrobial activity of selected EOs

Since the Middle Age, essential oils (EOs) have been widely used thanks to their antibacterial, antifungal, antioxidant, medical and cosmetic properties. Nowadays, there is a growing interest to develop novel and effective botanical products. Although the interesting perspective of EOs, their use, spread and marketing are still restricted due to several drawbacks: volatility, lipophilicity, physico-chemical instability and thermal degradation. One of the approaches suggested to overcome these limitations is the so-called encapsulation process through the preparation of aqueous nano-dispersions. The small size of the dispersed phase confers them many potential benefits for several applications: enhanced long-term stability (thermodynamic stability), increased solubility, thus increased bioavailability of active ingredients and improved handling. The aim of this work was to apply this technology to improve the real-world use of some EOs with known biological activity. We selected three EOs from the Apiaceae family of commercial interest, i.e. Pimpinella anisum L., Trachyspermum ammi (L.) Sprague and Crithmum maritimum L., to developed eco-friendly MEs. These EOs and their relative MEs were examined as antimicrobial agents against fungal (Microsporum canis and Candida albicans) and bacterial isolates (Escherichia coli and Staphylococcus aureus), obtained from veterinary sources. MEs resulted to be more active than the pure EOs, showing MIC values of two orders of magnitude higher. Thus, the encapsulation of EOs into the formulation increases the efficacy thanks to their stabilization, providing a better dispersibility and enhancing the interaction with the target.