Essential Oils: The Aromatic Compound

The essential oil is the small portion of plant material, which imparts the identifying flavor, and odor most closely associated with the plant itself. The delicate aroma of rose, the refreshing lift of pine or wintergreen, the pungent, sometimes offensive odor and flavor of garlic are the sensatory properties of these unseen oils.

There are two basic chemical building blocks in essential oils. These are molecules on which atoms are added to make more complex structures that create the specifics of each type of oil. The building blocks are the aliphatic or chain building block type called Isoprene Units and the aromatic or ring building block type called the benzene or more commonly phenyl rings:

Isoprene Units - This is a molecule consisting of 5 carbon atoms that form a basic chain or unit. These chains or units combine to form progressively heavier and more volatile chemicals. Generally they are 10, 15 or 20 carbon atoms long. These molecules form Terpene class chemicals, including Monoterpenes, Sesquiterpenes, Diterpenes and others.

Benzene Rings - This molecule consists of six carbon atoms formed into a ring. These rings can form phenols with the addition of other chemical groups.

In addition to the above building blocks, essential oils consist of chemical compounds, which have hydrocarbon, hydrogen and oxygen as their main structures or groups. These can be subdivided into two main groups: hydrocarbons. Which are made up almost exclusively of terpenes, monoterpenes, sesquiterpenes, and diterpens, and oxygenating compounds, mainly esters, aldehydes, ketones, alcohols, phenols oxides. Hydrocarbons are compounds subdivided into Alkanes, Alkenes and Cycloalkanes.

Terpenes

Terpenes are an important family or unsaturated naturally occurring compounds base on the isoprene molecule, thus, they are decomposed by heat, light and oxygen to produce undesirable compound which can give off-flavors and off aromas. They commonly have up to 10 carbon atoms in the molecule. They have omen aroma and may be therapeutic. They can have a citrus, fresh, green to an herbaceous, woody odor and analgesic, hypotensive and hormone balancing. Examples of terpenes are: Limonene in bergamont and orange; Phellandrene in eucalyptus and spearmint; Pinene in pine and eucalyptus; Sabinene in black pepper and cardamom. Generally, terpenes can be further classified into 3 groups, which are:

1) Monoterpene - are molecules made up of two Isoprene or 10 carbon atoms. They are slightly analgesic, antiseptic in the air bactericidal, expectorant and stimulating. Some are antiviral and some help break down gall stones.

2) Sesquiterpenes - are molecules made of three Isoprenes or 15 carbon atoms. They are slightly antiseptic, bactericidal, slightly hypotensive, calming and anti-inflammatory. In addition, some are analgesic and/or spasmolytic. They contribute to the lasting odour of the essential oil or the base note as most sequiterpenes consist of large slowly evaporating molecules and are antiseptic, calming and exhibit antihistamine action.

3) Diterpenes - are molecules made up of four Isoprenes or 20 carbon atoms. They are slightly bactericidal, expectorant and purgative. Some are antifungal, antiviral and may have a balancing effect on hormones.

Other Compounds and Combinations

Acids and Esters. Acids are either organic or inorganic. Inorganic acids (sulphuric acid) are dangerous and are not found in essential oils. Organic acids are can be beneficial and are found in oils but only in very small amounts. They are usually located in a combined state with esters. One therapeutic benefit is that they are anti-inflammatory. They have no contra-indications. Esters (sweet smelling and give smell to the oils) (anti-fungal, spasmolytic, and sedative) are formed as a result of a reaction between acids and alcohol. Their therapeutic benefit is they are anti-inflammatory, calming, good balancers, fungicidal, relaxing, effective against skin rashes, uplifting and act as a tonic. Esters are very common and found in a large number of essential oils. They include linalyl acetate, which is found in clary sage, bergamot, lavender and geraniol acetate in sweet marjoram. Of course bergamot has kind of fruity aroma. Clary sage has a sweet flowering aroma as well as lavender. Some of the other esters include bornyl acetate eugenol acetate, and lavendulyl acetate. The esters are generally safe to use, except for methyl salicylate which is found in wintergreen and birch.

Oxides. Another family group is the oxides. By far the most important oxide is cineol, which is found in eucalyptol, and in rosemary, cinnamon, melissa, basil. Oxides are rare in the oils except for eucalyptol. Some oxides have "oxide" at the end of their name, making identification easier.

Unfortunately, not all do. Their therapeutic benefit is they are mucolytic, making it useful for coughs, colds and congestion. The oxides can irritate skin and if the content is 1O% or higher, and therefore it should be used with care. Use them as you would phenols.

Lactones. These molecules are large and difficult to distill into oil. Therefore they are usually found in pressed oils or in absolutes. The two most common and important in essential oils are coumarins and their derivatives. Their therapeutic benefit is that they are good for lowering temperature and releasing catarrh. The only contra-Indication is photosensitization.

Coumarins are sedative and calming while uplifting and refreshing. They are anti-coagulating and hypotensive.

Furocoumarins are a derivative of coumarins. They have a contra-indication in that they are photosensitizers. A good example is bergaptene in bergamot oil.

Ethers are rarely found in the oils but when they are their therapeutic values are that they are analgesic, anti-depressant, anti-spasmodic, balancing, calming, relaxing, sedative, stimulating, and soothing.