November 20, 2020 3 min read

Essential Oils Are Complex Mixtures of Aromatic Compounds

Essential oils are made of volatile aromatic compounds. Volatile aromatic compounds are small organic molecules that tend to change from the liquid state to the gas state at room temperature.

You know, these molecules are so incredibly small that a single drop of essential oil contains a lot of them. The word “volatile” emphasizes their tendency to evaporate quickly at room temperature. This property is what makes them smell so potent.

So, when you first open a bottle of a fragrant essential oil, you instantly notice the aroma, and you can smell it even from a distance.

The physical and chemical properties of volatile aromatic compounds allow them to quickly enter the gas state, move through the air, and directly interact with olfactory sensors in the nose. Essential oils can be made up of anywhere between 1 and 1000 different compounds with different chemical identities. For example, Birch oil is almost entirely composed of one compound: methyl salicylate.

Spikenard Essential Oil, on the other hand, contains hundreds of compounds. Most oils fall somewhere in between these two extremes. For instance, Frankincense essential oil contains over 65 distinct chemical compounds in various quantities. The different compounds in an essential oil are known as constituents.

You know, each and every constituent has its own distinct structure, meaning that the shape, size, and arrangement of chemical bonds in that molecule is unique.

The different constituents in an essential oil determine both the oil’s aroma and the benefits it offers. The exact composition of an essential oil varies between plant species.

When speaking of essential oils, the word “composition” refers to the oil’s constituent makeup or, in other words, what chemical constituents it contains and how much of those constituents are present.

For example, Organic Bergamot essential oil contains over 35 different compounds, but it has especially high levels of two constituents called limonene and linalyl acetate. On the other hand, some oils contain over 50 compounds, with the two most abundant constituents being chamazulene and sabinene.

Monoterpenes are found in some amount in almost all essential oils. They have a structure of 10 carbon atoms derived from two isoprene units. Monoterpenes can have a straight-chain backbone or a single ring. Due to their smaller size, they tend to react quickly to air and heat, and then tend to be broken down more quickly than their more complex sesquiterpene counterparts.

Monoterpenes have strong effects on cell membranes because they are small enough to fit between the fatty molecules that make up the cell membrane. They are also small enough to completely pass through it and affect targets inside the cell. There are believed to be well over 2,000 varieties of monoterpenes, each with its own unique biological activity.

Sesquiterpenes have a structure of 15 carbon atoms derived from three isoprene units. Because of their higher molecular weights, sesquiterpenes are less volatile than monoterpenes and are therefore less prevalent in essential oils overall. It is believed that there are over 10,000 different varieties of sesquiterpenes.

Sesquiterpenes can have a straight-chain backbone, one ring, or two rings. Sesquiterpenes aren’t quite small enough to pass through the cell membrane as efficiently as monoterpenes, but they have unique shapes that allow them to adhere to pockets in three-dimensional protein structures, affecting protein activity. Sesquiterpenes are known to activate various cell surface receptors.