Essential oils are complex mixtures of volatile compounds derived from plants where they play aromatic, communicative and defensive roles. For a long period they have been used in medicine, agriculture and industry due to their wide spectrum of biological activity. They exhibit antimicrobial, antiviral, anti-inflammatory, antioxidant and smooth muscle relaxant properties. With high lipophilicity and low molecular weight, essential oil components easily pass biological membranes, bringing on therapeutic effects. Currently, the use of these oils is considered under studies that could possibly use the above factors against viral infections, prevent cancer, and diseases caused by inflammation. This could be an alternative option of some value compared to conventional treatments due to their natural origin and high tolerance. However, they must be of the right quality and standardization to be effective and used safely. The aim of the paper is to provide an overview of the nature of essential oils, the method applied in obtaining them, the composition and finally, their medical and therapeutic applications.
Introduction
Essential oils are very complex mixtures of volatile substances that are derived from plant materials. The composition of these oils is dependent on various factors, including the plant species and species, the parts of the plant used for extraction, soil composition, time of harvest, stage of the vegetation cycle, and extraction methods (Wigan 2010). The biggest role of essential oils is to provide fragrance and flavor in plants. It plays an extremely important role in communication, such as attracting pollinators and repelling insects. Some of them are also used for communication between members of the same species of plant (Gershenzon et al., 2007). For decades, aromatic plants and extracts produced from them have been associated with antiseptic, bactericidal, fungicidal, antiviral, and medicinal properties (Swamy et al., 2016; Bassole et al., 2012). in agriculture and for antimicrobial, antispasmodic, sedative, topical anesthetic and anticancer agents (Kowalski et al., 2023; Mustafa et al., 2023). Relevant to the present day, in the last years, the mechanisms of actions of essential oils, at the level of antimicrobials, were revealed more deeply (Basillet., 2000; Sienkiewicz et al., 2013). In connection with the constantly growing interest for "natural" treatment methods, with the re-emergence of folk medicine, essential oils appear to be a promising source of a universal remedy for basic patient pathologies. In addition to these, other discoveries may open ways to discover more antimicrobial, antiviral and anticancer drugs.Methods of preparation and formulation
There are various methods through which essential oils are extracted from plant materials. Some of these methods include steam distillation, solvent extraction, supercritical CO2 extraction, and cold pressing (Aziz et al., 2018). Steam distillation is a process in which plant material is mixed with water and boiled, so volatile aromatic compounds are distilled from there. Such vapor is passed through a condenser where condensation occurs. The oil collects in liquid and the water runs back to the distillation kettle. This is the most common process (Tongnunchhan et al., 2014), but its disadvantage is the possibility of thermal degradation of parts of the oil (Raut et al., 2014). Solvent extraction means passing a solvent organic into the plant material to dissolve the oil.The solvent then evaporates, and thus the essentia oil is left behind (Castro et al., 1999). This method does not involve heating, but adds additional chemicals. Supercritical CO2 extraction relies on carbon dioxide, in a supercritical state, as a selective solvent (Vron et al., 2017). This allows soft oil extraction without high temperatures and other solvents. The technique is expensive but highly effective (Elsayed et al., 2023). Cold pressing is a mechanical extraction of oil from plant material (Kitajima et al., 2004).
For example, it is performed on the peel of citrus fruits. It is not very laborious, but quite unproductive. The extraction process also determines the constitution and character of the essential oil obtained. Essential oils are considered to be mixtures of tens or hundreds of other chemical compounds (Bek Kali et al., 2008). Primary classes of compounds: • Terpenes and terpenoids, such as limonene and menthol; • aromatic compounds, such as cinnamate, • phenols, such as thymol, eugenol, • aliphatic alcohols, such as linalool and geraniol, • aliphatic ketones, such as camphor, • esters of aliphatic acids, that is, acetates and propionates. Generally, the major 2-3 components will take up a large percentage, which can range from 20 - 70%, while trace components make up the remainder (Dhifi et al., 2016). Different mixtures of essential oils account for considerable differences in biological activities and diverse ranges of uses (Driss et al., 2007). The chemical composition of an oil sample can be determined through chromatographic techniques (Shelly et al., 2000).
