Chemistry. Already getting nervous? The chemistry chapters of essential oil texts are the most frequently skipped, even by natural health professionals. But it can be fun and useful…really! Knowing what essential oils are made of, and how this affects their aroma and therapeutic value can have a big impact on the efficacy of your aromatherapy practice. Understanding the basics can help you make better choices in essential oils, and better choices in their application. Plus, this can give you the foundation for further understanding of true “medical aromatherapy”, as practiced in much of the rest of the world. So here's a primer on the chemistry of essential oils, with some common examples and important tips to help you grow as a holistic medicine practitioner.
So what is it that makes an essential oil different than every other oil we're familiar with? They don't feel the same, they don't act the same, and they certainly don't smell the same. Essential oils and the so-called “fixed” oils (you may also know them as carrier or base oils – like Sweet Almond, Apricot Kernel, Evening Primrose, etc) are distinctly different in their molecular structure. While both essential and fixed oils share common basic atomic elements of Carbon and Hydrogen, that's really where the similarity ends. Fixed oils are made of triglyceride structures – three long chains of carbon atoms, with hydrogens bonded at various places. The length of the chains and the position and number of hydrogens define the nature of the oil; if hydrogens are bonded to every available location, the oil is “saturated', for example. One missing hydrogen is “mono-unsaturated', more than one is “poly-unsaturated'. The long chains and relative consistency of the molecular structures makes fixed oils “oily', and does not allow them to evaporate quickly.
Essential oils are “volatile” oils – oils that DO easily evaporate. Their chains of carbon atoms to which the hydrogens attach are not as long or heavy, but are much more complex. Many essential oil structures are not really chains, but ring, or multi-ringed shapes with diverse sub-units – called “functional groups” – sticking out in various directions. Like their fixed oil counterparts, essential oils are lipophillic – meaning “fat liking”. The fat-liking nature of both fixed and essential oils makes them easily absorbed by our bodies. Because of their typically smaller structures however, essential oils are absorbed more rapidly than fixed oils, and can easily penetrate deep into the body.
Most of the therapeutic activity of an essential oil can be attributed to the functional groups of the individual chemicals that make up the oil. There can be over a hundred identifiable molecules in one essential oil. Each of these molecules, as mentioned earlier, is a chain or ring (or multiple-ring) structure of carbon atoms linked together with hydrogen atoms bonded to them in various configurations. Every chain or ring has a functional group attached – a functional group is defined by Salvatore Battaglia in “The Complete Guide to Aromatherapy” as: “a single atom or group of atoms that…has a profound influence upon the properties of the molecule as a whole. It is often referred to as the chemically active center of the molecule”.
As you can see, essential oils are really very complex in their chemical nature. There are nearly infinite possibilities of functional group and ring or chain combinations. And ONE essential oil alone can be made up of HUNDREDS of these different molecular arrangements. Don't worry, though! While it sounds complex, one needn't know all the precise chemical details to use essential oils therapeutically. When selecting between varieties of an essential oil, It IS helpful to know that any particularly oil is often composed of one or more primary molecular forms, with many minor or “trace” constituents, and that ALL these molecules contribute to the oil's aroma and therapeutic action.
The essential oil with the most perfect balance of natural chemical constituents will have the finest aromas and the most potent therapeutic action. Many factors in an essential oil's production affect this balance. These include where the plant was grown, soil and climate conditions, time of harvest, distillation equipment, as well as the equipment settings and skill of the distiller. This can give you an idea as to why two varieties of the same oil can smell so different: The wonderful aroma of a fine essential oil will contain an array of notes in a lovely balance, telling you that all natural components are present in the correct amounts.
As an example, let's look at Lavender, the most commonly used of all essential oils. More than 50 individual molecules are present in a high-quality Lavender. As noted earlier, all of these chemicals work together to produce a therapeutic effect. For example, “linalool” is antiviral and antibacterial; “linalyl acetate” is also emotionally calming; other constituents including cineol, limonene, alpha-pinene and others are all noted for specific biologic and aromatic activity. It is the combined, balanced action of these chemicals that make lavender such a useful healing agent – no one chemical can be singled out and used to give the same profound results.
What does this mean to the lay-practitioner? That it's important to find a nice smelling lavender oil! Each of the individual chemicals has a distinct smell, talked about in terms of “notes” within the overall lavender aroma. A precise amount of each will create a certain Lavender aroma. Some Lavenders are more sweet (and therefore more relaxing), others are more herbaceous (and more anti-microbial). There can be significantly different aromas from the same species of plant, even when the essential oils are of the highest quality. It is most often the essential oil that smells the most “true” to you that will be the most beneficial. Your senses can naturally detect what is good for you and what is not, if you're willing to listen to them impartially.
For the most therapeutic benefit, it is always best to use true, carefully-made essential oils. To do this, find a source that is dedicated to supplying only the highest grades of oils. Examine their product's aromatic quality and business practices and so that you are comfortable with their dedication to your health. Listen to your intuition and your own nose; they won't lie to you! With experience, your ability to discern between subtly different grades of oils will become more astute. And you'll understand what it is about the oil, chemically, that makes it unique.
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