Encapsulation of essential oils in solid lipid carriers: technological development and applications

Abstract

Essential oils (EOs) are complex mixtures of various volatile molecules (hydrophobic) produced by the plants secondary metabolism. Terpenoids (mono, di- and sesquiterpenes) and oxygenated compounds (eg, alcohols, esters, ethers, aldheydes, ketones, ester and phenolic lactones, and others) are the majors classes of compounds present in EOs. Essential oils have high importance in various industrial sectors, such as pharmaceutical, food, cosmetic, health, agriculture and livestock. Their wide spectrum of use is mainly linked to its proven bactericidal, virucide, fungicide, antiparasitic, insecticidal, analgesic, sedative, anti-inflammatory, spasmolytic and local anesthetic activities, depending of EO composition. Essential oils have also been used in food protection (as antioxidants and preservatives), and also embedded in active food packaging. The volatility is the main feature of EOs, which differentiates them from the fixed oils, mainly due to their characteristic odor. However, besides the high volatility, EOs also present significant instability problems, and may undergo irreversible changes of their physicochemical properties due to exposure to heat, moisture, oxygen and light. Their low water solubility is another limitation for the use of EOs in various applications. In this way, micro and nanoencapsulation technologies of plant derived substances, including EOs, arises as a viable and effective solution, increasing the product physicochemical stability, furnishing protection against environmental factors, reducing volatility, modulate the release, increasing bioavailability, reducing toxicity, among others. This technique involves the inclusion of the active agent in a carrier system, which may be composed of carbohydrates, gums, proteins, lipids, or other natural or synthetic polymeric materials. This technology allows, for example, to transform liquid and volatile substances in solids, alters product water solubility, protecting and modulating the release and functionality of active ingredients, and overcome of instability and incompatibility problems common in natural active ingredients. Encapsulation in lipid carriers has received significant attention in the pharmaceutical and food sectors, mainly due to the several attributed advantages such as low toxicity, capability to encapsulate hydrophilic and lipophilic compounds, low production costs and ease scale up. This research project aims to investigate technologies for production of lipid based systems (micro and nanostructured) to stabilize and modulate the release and functionality of essential oils, focusing on preparation processes, type of excipients, dehydration methods, physicochemical product properties, and evaluation of biological activity (antimicrobial and antioxidant). Emulsification technologies, fusion and others, followed by dehydration steps (with addition of drying carriers), will be investigated. As model for the development of this project were selected EOs from two aromatic plants already under investigation by our group (USP, 2009; REIS et al, 2011), the Rosmarinus officinalis (rosemary) and Lippia sidoides (pepper-rosmarin). These species have shown huge potential of application in the pharmaceutical, food, cosmeceuticals among others, presenting significant antioxidant and antimicrobial properties. These species are also listed in the list of medicinal plants with potential to generate products of interest to the SUS (National List of Medicinal Plants of Interest to SUS - RENISUS). (AU)