Essential oils are concentrated plant extracts that are used for their various therapeutic properties. These oils are made up of a complex mixture of chemical constituents, each of which contributes to the oil’s unique aroma and therapeutic effects.

Essential oils are made of several different chemical compounds which are responsible for their scent profiles. Each plant has a unique scent profile often called a top, middle or base note.  Top notes are the initial and uplifting scents in essential oils that evaporate quickly, middle notes provide a balancing effect and last longer, while base notes are the deep and grounding scents that last the longest and help anchor the fragrance.

Here are the 10 most common chemical constituents found in essential oils and the specific compounds that make them up:

Monoterpenes: These are hydrocarbons that are found in a variety of essential oils, including pine, lemon, and frankincense. Monoterpenes are known for their antibacterial, antiviral, and anti-inflammatory properties. Specific compounds include limonene, alpha-pinene, and beta-pinene. Some essential oils that contain this compound include Lemon essential oil (contains limonene), Frankincense essential oil (contains alpha-pinene and beta-pinene), Pine essential oil (contains alpha-pinene and beta-pinene).

Sesquiterpenes: These are hydrocarbons that are found in essential oils such as frankincense, patchouli, and ginger. Sesquiterpenes have anti-inflammatory, antispasmodic, and sedative properties. Specific compounds include alpha-humulene, beta-caryophyllene, and valencene. Some essential oils that contain this compound include Frankincense essential oil (contains alpha-humulene and beta-caryophyllene), Patchouli essential oil (contains alpha-bulnesene and patchoulol), Ginger essential oil (contains alpha-zingiberene and beta-sesquiphellandrene).

Phenols: These are compounds that are found in essential oils such as thyme, clove, and basil. Phenols are known for their antibacterial and antiviral properties. Specific compounds include thymol, carvacrol, and eugenol. Some essential oils that contain this compound include Clove essential oil (contains eugenol), Thyme essential oil (contains thymol), Basil essential oil (contains methyl chavicol).

Esters: These are compounds that are found in essential oils such as lavender, chamomile, and fennel. Esters have relaxing and calming properties. Specific compounds include linalyl acetate, geranyl acetate, and benzyl acetate. Some essential oils that contain this compound include Lavender essential oil (contains linalyl acetate), Roman chamomile essential oil (contains isobutyl angelate), Clary sage essential oil (contains linalyl acetate).

Aldehydes: These are compounds that are found in essential oils such as citronella, lemongrass, and tea tree. Aldehydes have antimicrobial and insect repellent properties. Specific compounds include citral, citronellal, and neral. Some essential oils that contain this compound include Cinnamon essential oil (contains cinnamaldehyde), Citronella essential oil (contains citronellal), Lemongrass essential oil (contains citral).

Ketones: These are compounds that are found in essential oils such as rosemary, thyme, and peppermint. ketones have expectorant and anti-inflammatory properties. Specific compounds include camphor, menthone, and pulegone. Some essential oils that contain this compound include Peppermint essential oil (contains menthone and pulegone), Rosemary essential oil (contains camphor and verbenone), Hyssop essential oil (contains pinocamphone and isopinocamphone).

Lactones: These are compounds that are found in essential oils such as German chamomile and yarrow. Lactones have anti-inflammatory and sedative properties. Specific compounds include gamma-bisabolol, delta-bisabolol, and gamma-curcumene. Some essential oils that contain this compound include German chamomile essential oil (contains alpha-bisabolol oxide A), Yarrow essential oil (contains chamazulene), Sweet fennel essential oil (contains anethole).

Coumarins: These are compounds that are found in essential oils such as tonka bean and bergamot. Coumarins have antispasmodic and sedative properties. Specific compounds include coumarin, tonkolide, and bergapten. Some essential oils that contain this compound include Tonka bean essential oil (contains coumarin), Sweet woodruff essential oil (contains coumarin), Bergamot essential oil (contains bergapten).

Terpenoids: These are compounds that are found in essential oils such as ginger and pine. Terpenoids have anti-inflammatory and analgesic properties. Specific compounds include zingiberene, gingerol, and phellandrene. Some essential oils that contain this compound include Ginger essential oil (contains gingerol), Juniper berry essential oil (contains alpha-pinene and myrcene), Pine essential oil (contains alpha-pinene and beta-pinene).

Oxides: These are compounds that are found in essential oils such as eucalyptus and tea tree. Oxides have expectorant and decongestant properties. Specific compounds include 1,8-cineole, trans-anethole, and camphor oxide. Some essential oils that contain this compound include Eucalyptus essential oil (contains 1,8-cineole), Tea tree essential oil (contains 1,8-cineole), Ravintsara essential oil (contains 1,8-cineole).

It’s important to note that different essential oils may contain different combinations of these chemical constituents, and the specific chemical makeup of an essential oil can vary depending on factors such as the plant species, growing conditions, and extraction method. Additionally, essential oils should always be used with caution and diluted properly, as they are highly concentrated and can be irritating to the skin.

In review, essential oils are derived from plant extracts and contain a mixture of chemical compounds, each with unique properties that contribute to the oil’s aroma and therapeutic benefits. These compounds, such as monoterpenes, phenols, and ketones, are responsible for the various effects essential oils can have on the body, including antibacterial, antiviral, anti-inflammatory, and sedative properties. It’s important to note that each plant has its own unique scent profile, with top notes providing an initial uplifting scent, middle notes balancing the aroma, and base notes offering a deep and grounding scent. Always use essential oils with caution, as they are highly concentrated and can be irritating to the skin when not properly diluted.