Download Understanding the Chemical of Essential Oils

ACP-2 Lesson Three
Essential Oil Chemistry
Essential oils contain a complex amalgamation of natural compounds
which determines their fragrance and therapeutic properties. Like all
other living matter, essential oils contain chemical compounds made
up of oxygen, carbon and hydrogen which together create a synergy
of different constituents that endow them with antibacterial, antiviral,
antifungal, and antiseptic properties.
The average essential oil contains around 100 to 300 components,
along with thousands of other trace compounds that have yet to be
identified by scientists. While attempts have been made to single out and synthetically duplicate identifiable
components, nature far exceeds laboratory efforts and continues to remain mostly a mystery in their unique
makeup.
In fact, the specific chemistry of an individual essential oil is influenced by such a diverse range of factors that it
is impossible to synthetically recreate its components in a laboratory. The chemical composition of an essential
oil can be affected by its climatic conditions, pollutant exposure, extraction process and other factors that can
influence its aroma and therapeutic powers.
Understanding the Chemical of Essential Oils
Understanding the components of an essential oil can help you to assess its suitability for treating a specific
condition. For example, to treat inflammation it is helpful to use oils that contain azulene or bisabolol, as these
have recognized anti-inflammatory qualities. Determining the chemistry of essential oils is therefore vital when
creating an aromatherapy blend.
This knowledge can also help you to devise a treatment plan – for example, whether you require strong, shortterm treatment, or milder treatment over a longer period. Certain chemicals are suited for working in different
ways.
However, it is important to realize that aromatherapy is not purely based on chemical analysis – essential oils
are intricate and are not a simple product of their base ingredients. Geranium is known to have certain qualities
that cannot be explained by its known chemical ingredients – the overall synergy of constituents is what ultimately
determines an essential oil’s unique character.
When studying essential oil components, it is always imperative to consider the oil as a whole. Some chemicals
may only be responsible for a tiny percentage of the oil’s composition, yet play a large part in its unique character.
A good example of this is B-damascenone, which makes up only 0.14% of Rose essential oil, but is responsible
for its distinctive rose fragrance.
Note: Kurt Schnaubelt, Ph.D., author of Advanced Aromatherapy, states that the classification system based on
chemical components of oils is the most effective way to determine which oils to use in an essential oil blend. In
addition, combining oils that share the same constituents reinforces their effectiveness and offers support by the
trace components.
Similarly, when considering the potential contra-actions of using an essential oil, it is necessary to consider its
ingredients as part of the overall blend. Scientific tests have shown that skin-sensitizing aldehydes can be
neutralized when balanced within the blend of other chemicals in the essential oil.
It’s important to remember too which adds to the complexity of their chemical makeup, is that when essential oils
are combined a new formula is created, often enhancing the effectiveness of the individual oils.
Classification of Essential Oils by Chemical Groups
Essential oil compounds may be categorized into two distinct chemical groups: hydrocarbons, which are made
up of terpenes (monoterpenes, sesquiterpenes, diterpenes, and triterpenes) and oxygenated compounds, which
includes esters, aldehydes, ketones, alcohols, phenols, and oxides.
1) Hydrocarbons
When hydrogen and carbon atoms are arranged in a chain formation they form compounds known as terpenes.
This is an umbrella term that includes a group of chemicals such as monoterpenes, sesquiterpenes and
diterpenes. Essentially, terpenes are known for their detoxifying properties by preventing toxin accumulation in
the body and aiding their elimination. Terpineols formed from acetyl-coenzyme A, plays an important role in the
production of hormones, vitamins, and energy in the body.
Monoterpenes – e.g. pinene
Found in most essential oils, monoterpenes are composed of 10 carbon atoms and two isoprene units.
Monoterpenes can help to rebalance malfunction in cellular memory, as well as unify the other molecules that
are contained in an essential oil. Around 90% of citrus oils contain limonene, which has the ability to kill viruses.
Although potential skin irritants, monoterpenes have many positive abilities – they are generally antibacterial and
antiseptic, with stimulating, expectorant and decongestant properties. One of monoterpenes most valuable
capabilities is its ability to reprogram miswritten information in the cellular memory.
Oils high in monoterpenes include Angelica Root, Pine, Cypress, Galbanum, Hyssop, Juniper Berry,
Frankincense, Cistus Labdanum and most citrus oils.
Sesquiterpenes – e.g. bisabolene
These are molecules that contain 15 carbon atoms and three isoprene units. With a unique ability to cross the
blood-brain barrier, they can increase the oxygen level of brain tissue and stimulate the pineal and pituitary
glands. Sesquiterpenes are generally calming, cooling, antiseptic, antibacterial, analgesic and anti-inflammatory.
They can also help to repair miswritten DNA code, which can be particularly effective on cancerous cells.
Oils high in sesquiterpenes include Sandalwood, Cedarwood, Vetiver, Patchouli and Ginger.
Diterpenes – e.g. camphorene
Diterpenes rarely survive the steam distillation extraction process, so they are usually only found in a few oils, in
very small quantities. Clary Sage is an example of one of the more common essential oils that contain diterpenes.
Containing 20 carbon atoms and four isoprene units, they are antibacterial, antiviral and antifungal. Diterpenes
can also balance hormones, stimulate the immune system and – as expectorants – effectively rid the body of
mucus.
2) Oxygenated Compounds
This second group of chemical constituents includes compounds such as esters, aldehydes, ketones, alcohols,
phenols and oxides.
Alcohols
The mild nature of alcohols makes them generally safe to use on children or the elderly. Alcohols are usually
non-toxic and not known to cause skin irritation, despite being highly germicidal against bacteria, viruses, and
fungi. With a pleasant, uplifting fragrance, they are considered to be extremely therapeutic in aromatherapy.
They also provide antiviral, antifungal and antibacterial properties.
Oils high in alcohols include Citronella, Geranium, Lavender, Rosewood and Clary Sage.
Monoterpenols – e.g. linalool
Monoterpene alcohols, also known as monoterpenols, are common among the essential oils used by
aromatherapists due to their mild yet therapeutic qualities. They are generally known to be antimicrobial,
stimulating, warming, strengthening and diuretic. Monoterpenols are particularly useful in skin care, due to their
gentle anti-inflammatory properties.
Oils containing monoterpenols include Citronella, Geranium, Rosewood, Lavender, Eucalyptus, Juniper Berry,
Palmarosa, Peppermint, Tea Tree and Marjoram.
Sesquiterpenols – e.g. bisabolol
The properties of sesquiterpene alcohols, also known as sesquiterpenols, may be antispasmodic, antiphlogistic,
anti-inflammatory and sedative. Dr. David Hill in his book, Frankincense, speaks of oils heavy in sesquiterpenes
being helpful with arthritis since they inhibit inflammatory response.
Oils high in sesquiterpenols include German and Roman Chamomile, Helichrysum, Carrot Seed, Sandalwood,
Ginger, Patchouli, Vetiver and Valerian.
Diterpenols – e.g. sclareol
Diterpene alcohols, also known as diterpenols, are not commonly found in essential oils due to the higher weight
and boiling point of their molecules. Sclareol is found in Clary Sage, in an amount small enough to survive the
steam distillation process. Being similar in structure to human hormones, diterpenols can have a balancing effect
on the endocrine system.
Phenols – e.g. thymol
Phenols are known to be powerful, so they should only be used in a low concentration for a short period. Highly
antiseptic, phenols are effective at both killing and preventing the growth of bacteria, fungi and viruses. They can
also stimulate the immune system and aid depression. Due to their strength, phenols can be highly irritating to
the skin and may cause liver toxicity with long-term use. Thyme and Oregano are known as ‘hot oils’ due to the
burning sensation they can produce on the skin.
Oils high in phenols include Thyme and Oregano.
Aldehydes – e.g. citronellal
Known for their citrus-like – and sometimes aphrodisiac – fragrances, aldehydes are generally calming, antiinflammatory and hypotensive. Aldehydes consist of an oxygen atom double bonded to a carbon atom at the end
of the carbon chain. Their effectiveness is most beneficial when used in a lower concentration, such as 1% or
less. Aldehydes can also be strongly antifungal, antiviral, and antiseptic, although they may cause skin irritation.
Oils high in aldehydes include Lemongrass, Lemon Verbena, Melissa, Eucalyptus and Citronella.
Ketones – e.g. camphor
Although ketones can be toxic in high doses, they offer therapeutic benefits when used with care. Ketones are
known for their expectorant and decongestant properties that help the flow of mucus from the body. They can be
calming and sedative, helping to reduce pain, aid digestion, reduce inflammation, improve scar healing and
regenerate new tissue.
Oils high in ketones include Jasmine, Hyssop, Camphor, and Clary Sage.
Some Common Questions Regarding Ketones
1)
Should I avoid oils containing ketones?
Essential oils that are high in ketones can potentially irritate the nervous system or cause neurotoxicity in high
doses, so individuals who suffer with a seizure disorder such as epilepsy should avoid these. In particular, Thuja
and Wormwood oils are rarely used in aromatherapy at all, due to their high ketone content.
2)
What is the best way to use oils containing ketones?
It is important to adhere to the recommended dosage of essential oils that contain ketones, as they are potentially
harmful substances that can accumulate in the body. It is advised to use such oils for a short-term period to avoid
possible neurotoxicity.
3)
Are all essential oils containing ketones toxic?
Not all essential oils that contain ketones are necessarily toxic. Some popular essential oils such as Rosemary,
Eucalyptus and Helichrysum contain a moderate amount of ketones but can still be of therapeutic benefit when
moderated in a blend.
Esters – e.g. linalyl acetate
These are chemical compounds formed when alcohols react with acids. Most plant acids are water-soluble, so
they are not abundant in steam-distilled essential oils but instead are more commonly found in hydrosols. Esters
are not usually the main component of an essential oil – however, even in minute amounts they play a key role
in the fruity note of their fragrance. They are also antifungal, anti-inflammatory, sedative and calming to the skin
and nervous system.
Oils containing esters include Lavender, Clary Sage, Geranium, Petitgrain and Roman Chamomile.
Oxides – e.g. cineol
Oxides can aid the respiratory system due to their expectorant properties – a common example is cineol, which
is the main component of Eucalyptus oil. They may also have diuretic, antiseptic and immune-stimulating actions.
Oxides are molecules where an oxygen atom is included in the structure to make a ring. The most common
molecule is 1, 8-cineole, known as eucalyptol. Oxides are commonly found in essential oils from plants in the
Myrtaceae family.
Oils containing oxides include Eucalyptus, Hyssop, Rosemary and Tea Tree.
Ethers
Ethers are antispasmodic and carminative in nature. As molecules, they result when oxygen is not integrated in
a ring system but are between two unconnected carbon chains.
Oils containing anethol include Aniseed and Fennel and methyl chavicol is found in Basil and Tarragon.
Lactones – e.g. bergapten
Lactones are an ester group derived from lactic acid. Although lactones can be neurotoxic, essential oils usually
only contain extremely low quantities. They are known primarily for their balancing and decongestant properties,
making them suitable for treating conditions such as chronic bronchitis. They may cause photo-sensitivity, such
as bergapten, which is found in Bergamot.