Essential Oils (EOs) are aromatic volatile oils extracted from plants by steam distillation and various solvents. Aromatic oils have distinct aromas or smells, and contain carbons with many double bonds and rings, which makes them very stable. Volatile means that the oil is always both in liquid and vapor form at the same time, so a partially filled cup of EO would have the liquid form at the bottom with vapor above it. They are produced by the plant to protect itself from harmful insects, bacteria, fungi, and viruses.
Since the middle ages, EOs have been widely used for their ability to fight bacteria, fungi, viruses and parasites, and insects, and other medicinal properties such as analgesic, sedative, anti-inflammatory, spasmolytic, and local anaesthetic remedies.Their key ingredients are low molecular weight compounds such as Phenylpropanoids, Terpenoids (ie monoterpenes, sesquiterpenes, oxygenated monoterpenes, oxygenated sesquiterpenes), and Phenolics (among others) which are responsible for their many wide-ranging biotechnological applications and pharmacologic properties: antibacterial, antifungal, antiviral, antiparasitic, antiinflammatory, antiarthritic, antimutagenic, anticarcinogenic, antidiabetic, cardioprotective, gastroprotective, hepatoprotective, and neuroprotective to name a few.
Below is a list of medicinal and other uses of EOs:
- Food storage and preservation: The many compounds present in both the liquid and vapor forms of these oils make them ideal food preservatives because they reduce the level of oxidation, production of free radicals, degradation, and contamination of the food, particularly by fungi and their toxins. EOs have even been shown to have synergistic effects when used along with conventional food additives. EOs from oregano, rosemary, thyme, sage, basilica, ginger, myrtle, and others, when used alone or in combination with others have been shown to extend meat and meat product shelf life by controlling lipid oxidation and improving the meat’s appearance and smell. Their Phenolic constituents act as free radical scavengers and hydrogen donators that prevent lipid oxidation, which causes spoilage.
- Citrus EOs consist mainly of monoterpenes and are widely used as natural food and drug preservatives because of their antifungal activities.
- Myrtle EOs are now also being used as antimicrobial agents in the food and pharmaceutical industries.
- Oregano and other spice EOs contain a core bioactive compound Carvacrol (4-isopropyl-2-methylphenol). Important activities include its antioxidative properties in foods (like lard and sunflower oil) and in vivo, and the inhibition of foodborne and human antibiotic-susceptible and antibiotic-resistant pathogenic bacteria, viruses, pathogenic fungi and parasites, and insects in vitro and in human foods (e.g., apple juice, eggs, leafy greens, meat and poultry products, milk, oysters) and animal feeds and feed wastes.
- The phenylpropanoids found in EOs are now well recognized for their potent anti-inflammatory effects, which supports for their use in virtually all patients with chronic disease.
- The phenylpropanoids, oxygenated sesquiterpenes, and monoterpenes present in EOs have been shown to have killing activity against Diptera (an insect) larvae, the immature stage of the primary vector (carrier) of dengue. This would make them very useful in avoiding or controlling the spread of various viral epidemics.
- EOs containing carvacrol, cinnamaldehyde, cinnamic acid, eugenol and thymol can have a synergistic effect in combination with antibiotics and are beginning to be used together with them in increasing cases of antibiotic resistance (ie MRSA).
- More than 20 compounds found in EOS have been shown to have therapeutic activity against peptic ulcers.
- Cancer prevention and Treatment: Over 100 new in vitro and in vivo studies have shown the beneficial effects of EOs against various cancers through multiple mechanisms. Antioxidant, antimutagenic and antiproliferative, enhancement of immune function and surveillance, enzyme induction and enhancing detoxification, modulation of multidrug resistance and synergism of volatile components have all been demonstrated.
- Accumulating data has revealed anticancer activity in plant-derived monoterpenes.
- Aromatherapy has been studied on surgical patients. Lavender or orange and peppermint essential oils have shown positive results in treatment of nausea and anxiety. Tea tree oil has also shown efficacy in treatment of infections.
- Sleep Enhancement: Many studies have shown that EOs have a positive effect on sleep. Lavender was the most frequently studied and is the most commonly used.
- Encapsulations of EOs in nanoparticles has been proposed to reduce to their volatility (passage into the vapor phase) and improve their efficacy (increased water solubility, stability and bioavailability).