Breaking Down Essential Oils
A typical essential oil contains hundreds of individual compounds, most of which don’t even amount to 1% of the total mixture.
Don’t worry, I’m not going to list all of them. Fortunately, these compounds can be grouped into families. The smaller and therefore lighter compounds have the highest concentration, and the heavier ones tend to be there in lesser amounts.
What’s Inside an Essential Oil?
The majority of compounds found in essential oils are terpenes. I have explained terpenes in other blogs because they are found in many herbs, but I would be surprised if you remembered it, so it bears repeating.
The building blocks of terpenes are called isoterpenes, which can be thought of as half a terpene; in fact, one isoterpene molecule is called a hemiterpene (hemi means half) and has 5 carbons, 8 hydrogens, and 2 double bonds.
Don’t get spinny over these names. It is just a name for a building block. It is no more complicated than building blocks you may have played with when you were young. It’s just that there are a lot of them, and they all have to have a name.
Terpene Naming
So a monoterpene (mono means 1) would have 2 isoprenes, in other words 10 carbons, 16 hydrogens, and 4 double bonds.
And a diterpene (Di means 2) would have 4 isoprenes or 2 terpenes, etc. Chemists write the formula for terpenes like this for short (C₅H₈)ₙ. So a terpene is just a string or any shape that can be made from these (C5H8) building blocks, and the n tells you how many blocks are in that structure
The 'n' is the number of isoterpenes in the structure of a specific family of terpenes. So the number of terpenes in a molecule would be n divided by 2.
What happens when there is an odd number of isoprene units? In those cases, special names had to be invented. For example, between mono- (meaning one) and di- (meaning two), the prefix sesqui- is used to indicate one and a half.
2 and a half = sester-
3 and a half = sesquarter-
Four terpenes would be called a tetraterpene. There are few, if any, terpenes that are bigger than a tetraterpene that could evaporate easily, so we wouldn’t find them in essential oils. But terpenes can get very big and past 50, they are just called polyterpenes.
Hopefully, you feel edified by that explanation, and you will be able to understand what comes next. If you are confused, go back over it and sketch it out till you see the simplicity before going forward. Or if there is a word there that you don’t get, look it up.
Why Terpenes Matter in Essential Oils
The reason I explained all that is because essential oils contain many monoterpenes and sesquiterpenes. And they also contain compounds that are made from these. For instance, there are alcohols made from monoterpenes, and they are called monoterpenols. The suffix -ol means alcohol, which means that somewhere there was an addition of an oxygen and a hydrogen (-OH) added to the molecule.
Can you guess what alcohols are made from the sesquiterpenes? If you said sesquiterpenols, you are tracking!
Now for some real info. The probability is that the food you eat every day contains terpenes, but in essential oils, the concentration of terpenes is what makes them so powerful. It takes a lot of plant matter to create an ounce of essential oil.
Compound Families
Monoterpenes
The monoterpene family of compounds is the most common constituent of essential oils.
The common properties of these substances are:
- Handles biological challenges
- Keeps things germ-free
- Analgesic
- Keeps the Immune system from overreacting
- Decongestant
- Rubefacient
- Stimulant
Exact profiles of monoterpene content or content in general are not possible because this differs between plants and the conditions they are in. These compounds are part of the plant's immune system and depending on their challenges can vary greatly.
I did find a file of one brand that used lab testing over a long period of time to determine the average percent content of their essential oils so you could get some idea.
These are average percentages of monoterpenes found in the following essential oils:
- Grapefruit: 96%
- Mandarin and Bitter Orange: 90%
- Lemon: 87%
- Sweet Orange: 85%
- Juniper Berry: 80%
- Cypress and Nutmeg: 75%
- Lime: 72%
- Pine: 70%
- Black Pepper: 60%
Sesquiterpenes
The sesquiterpene Family is the next most common. The common properties of these are:
- Handles biological challenges
- Keeps things germ free
- Analgesic
- Keeps immune system from overreacting
- Balancing
- Calming
- Cell regenerative - good for healing
Commonly observed percentages include:
- Vetivert: 65%
- Cade and Virginia Cedarwood: 60%
- Ginger: 55%
- Atlas Cedarwood and Patchouli: 50%
- Yarrow: 45%
- Helichrysum and Ylang Ylang: 40%
- Myrrh: 39%
- German Chamomile: 35%
Terpene Alcohols
Next are the Mono- and Sesquiterpene alcohols. Common properties of these:
- Protects against biological challenges
- Keeps things clean and germ-free
- Stimulating
Average concentrations include:
- Rosewood: 90%
- Palmarosa: 85%
- Sandalwood: 80%
- Coriander and Cornmint: 70%
- Geranium: 63%
- Catnip: 62%
- Rose Otto: 60%
- Basil and Sweet Marjoram: 50%
- Tea Tree Oil and Lavandin: 45%
- Peppermint: 42%
- Myrrh, Neroli, and Vetivert: 40%
- Lavender: 36%
- Cedarwood: 30%
Phenols
Phenols are a special family of alcohols. They all contain a six carbon ring with double bonds on every other carbon with an -OH attached. Although they are light, their attraction to each other makes them more resistant to evaporation, and they are found in essential oils.
You probably remember anethole from licorice, eugenol from cinnamon, and thymol from thyme, but in these things they are at a much less concentration, something like 4-12%.
Common properties of phenols are:
- Handles biological challenges
- Keeps things germ free
- Stimulates the immune system
- Mind stimulant
- Rubefacient
Typical percentages found in essential oils include:
- Clove Bud and Basil (of the Methyl Chavicol chemotype, ct for short): 90%
- Cinnamon Leaf: 86%
- Oregano and Tarragon: 70%
- Fennel: 62%
- Thyme ct Thymol: 40%
Certain essential oils are classified into different chemotypes (ct) because members of the same species can vary significantly in composition depending on growing conditions and other environmental factors. Chemotypes are identified by the compound present in the highest concentration within that plant.
Aldehydes
Aldehydes are also present in essential oils. This family has a carbon on the end of a chain of carbons that is double bonded to an oxygen and also bonded to a hydrogen. These are generally very pleasant-smelling compounds and contribute greatly to the overall smell of an essential oil.
Common properties of aldehydes include:
- Handles biological challenges, notably fungal
- Keeps the system from overreacting
- Keeps things germ-free
- Calming yet uplifting
These are percentages of aldehydes found in the following essential oils:
- Citronella, Lemongrass, Lemon Eucalyptus: 80%
- May Chang, Lemon Balm: 50%
Ketones
Ketones have a pleasant and camphorous, distinct smell. The ketone family has a carbon with a double bond to an oxygen, but it is not located at the end. It is always attached to two carbons, one on each side. Aldehydes have it on the end, and ketones have it anywhere within the chain of carbons.
Common properties of ketones are:
- Decongestant
- Expectorant
- Helps wound healing
- Breaks down fat and mucus
- Some are calming
Percentages of ketones found in these essential oils:
- Spearmint: 55%
- Caraway: 54%
- Marigold and Dill: 50%
- Hyssop: 46%
- Eucalyptus dives: 45%
- Sage: 35%
- Rosemary: 25%
Esters
Esters have an intensely fruity aroma. They are found in most essential oils in varying degrees. The Ester family has a carbon double-bonded to an oxygen and a single bond to another oxygen, and both the carbon and the single-bonded oxygen are attached to carbons that can be attached to any other structure.
The common properties of esters are:
- Some kill fungus and some inhibit its growth
- Loosens spasms
- Analgesic
- Calms the body
- Calms the nervous system
- Regenerates cells for healing
- Can help you sleep
Commonly found percentages os esters include:
- Sweet Birch: 99%
- Chamomile: 75%
- Clary Sage and Benzoin: 70%
- Bergamot: 40%
Oxides
And last but not least, we have the oxides. Any compound containing an oxygen attached somewhere falls under an Oxide. They can also be in other families so this just picks up the stragglers. Oxides have the strongest smells of all the molecules if the oxygen that makes them an oxide is attached to an already fragrant molecule. Eucalyptol is an example of this. That is what gives eucalyptus its smell.
Common properties of these types of oxides:
- Tends to dry out a tissue
- Cooling
- Dilates lung passages
- Decongests
- Dissolves mucus
- Cleans out lungs
- Calms down immune overreactions
Percentage of these oxides found in the following essential oils:
- Eucalyptus: 78%
- Ravensara and Niaouli: 60%
- Wild Marjoram: 55%
- German Chamomile: 35%
- Lavender Spike: 34%
- Rosemary: 30%
Conclusion
Thank you for sticking with me. When I set out, I didn’t realize it would take so long, but now you know more about essential oils than most people who sell them.