Essential Oils are a complex combination of: Carbon, oxygen, and hydrogen, with some constituents containing nitrogen and sulfur, they can be divided into two specific groups based on chemical constituents: 

  1. Hydrocarbons
  2. Oxygenated compounds

1. Hydrocarbon Essential Oils
The hydrocarbons consist mainly of monoterpenes and sesquiterpenes.
Monoterpenes cleanse and stimulate our moods while supporting our bodily systems with their antioxidant power. Cellular vitality can be supported by using monoterpenes containing limonene, pinene, terpinene, and cymene. 
Commonly used Essential Oils: Citrus oils, frankincense, black pepper, dill, fennel, white fir, juniper berry, coriander, cypress, rosemary, melaleuca, and marjoram.
Sesquiterpenes: Cleanse our bodies by supporting circulation and digestion while also giving emotional balance allowing for mental clarity and a sense of well-being.
Commonly used Essential Oils: Cedrene, zingiberene, himachalene, and caryophyllene found in cedarwood, ginger, helichrysum, and Melissa.

2. Oxygenated Essential Oils
Oxygenated compounds consist of several subgroups, including alcohols, phenols, aldehydes, esters, ketones, and oxides, The major compounds, or constituents, that are found in essential oils can be classified as follows:

COMPOUNDS  PROPERTIES EXAMPLES

Aldehydes

Responsible for the characteristic fragrance, or aroma, of many essential oils. Protect us from environmental threats to support healthy bodily and immune function while calming our emotions and moods. 
Properties: Anti-infectious // tonic // anti-inflammatory // vasodilating // hypotensive // antiseptic // fever-reducing // calming

Cinnamaldehyde - Cassia & Cinnamon
Geranial - Lemongrass & Melissa
Neral - Lemongrass
Citronellal - Tea tree, Eucalyptus

Alcohols

Cleanse skin & protect from environmental threats while simultaneously supporting our moods & cellular growth. Alcohols are uplifting and energising.
Properties: Antiseptic// Antiviral //Anti-fungal

Santalol - Sandalwood
Linalool - Basil, Marjoram, Coriander,
Menthol - Peppermint

 

Alkanes

Only a few essential oils contain alkanes and usually in very small quantities. Rose oil appears to have the highest concentration of alkanes at up to 19%. The purpose of alkanes in plants is to protect the plant from harmful organisms and predators, as well as decrease water and mineral loss. Rose oil contains significant amounts of alkanes.

Tricosane - Wild Sweet William
Undecane - Ginger
Dodecane - Ginger 
Decanal - Corriander Lemongrass & Mandarin

Alkenes

Abundant in trees and other plants, alkenes influence the characteristic odor of essential oils. These compounds can be identified by their “-ene” ending. 
Properties: Anti-inflammatory //relaxant // anticancer // analgesic //anti-fungal // antimicrobial.

Limonene - Grapefruit
Myrcene - Parsley
Humulene - Sage
Chamazulene - Blue Tansy
Thujene - Eucalyptus

 

Carboxylic Acids

Organic acids formed by the oxidation of aldehydes that usually end in “-ic acid.” They are rarely found in essential oils because they are not very volatile. 
Properties: Anti-inflammatory // Antiallergenic.

Rosmarinic Acid - Rosemary Chamazulene - Blue Tansy 
Carboxylic Acid - Yellow Fleabane

 

Coumarins

Typically phototoxic and should not be used immediately prior to sun or UV exposure. They are not easily extracted during the distillation process because they are not very volatile.
Properties:  Blood thinning // hypotensive // antispasmodic // anticonvulsant // antimicrobial

Bergapten - Bergamot
Psoralen - Babchi
Angelicine - Angelica Root
Bergaptol -  Lime

Esters

Generally very fragrant, often producing a fruity aroma, Calm our moods, emotions, and muscles while supporting hormones, nourishing skin, and supporting restful sleep.
Properties: Antispasmodic // anti-inflammatory // antifungal // relaxant, antimicrobial // skin-nourishing.

Methyl Salicylates - Birch & Wintergreen
Linalyl Acetate - Clary Sage & Lavender
Neryl Acetate - Helichrysum

 Ethers

Have similar properties and characteristics to esters but are considered much stronger compounds. Because of their powerful effect, essential oils that contain ethers should not be taken in high doses or used for extended periods.
Properties: Antiseptic // anti-infectious // anti-inflammatory // antispasmodic // expectorant // stimulant // diuretic // nervine.

Estragole - Tarragon
Anethole - Fennel 

 

Ketones

Calm our moods to support restful sleep but afford us mental clarity with powerful antioxidants that support our digestion and respiration. Not easily metabolised by the liver, so those with liver diseases should use very small quantities of essential oils high in ketones and only for short periods
Properties: Aid the reduction of mucous // stimulate cell and tissue regeneration // promote healing of scar tissue // anti- inflammatory // relieve pain // reduce fever // may inhibit coagulation of blood // calming.

Carvone - Dill
Camphor - Rosemary
Methone - Peppermint. Jasmine, Fenchone, & Isomenthone are considered nontoxic.
Camphor, borneol, & eucalyptol are monoterpene ketones evidence suggests may be toxic to the nervous system depending on dosage

 

Lactones

They are primarily found in expressed oils, but are sometimes found in solvent-extracted oils as well.
Properties: Antimicrobial // antiviral, anti-inflammatory // relaxing // analgesic // fever reducing // may lower blood pressure

Bergaptene - Bergamot
Furanogermacrene - Myrrh
Coumarin - Lavender
Alantolactone - Horse-heal & Elfdock

 

Oxides

Promote healthy immune function and protect against environmental threats as well, supporting healthy respiration and easing our feelings of tension. They can be recognized by their suffix "-oxide" or "-ol," Known to cause skin irritation and sensitivity, so they should be used with caution topically
Properties: Expectorants // mildly anti-infectious // antiseptic // anesthetic

Eucalyptol (also called 1, 8-cineole) - Eucalyptus, Rosemary, Peppermint & Thyme
Rose oxide - Rose
Linalool oxide - Rosewood
Pinene oxide - Ironwort

 

 Phenols

This is a very specialised group packed with powerful antioxidants that protect us from environmental threats and promoting cellular growth, though they are very potent leading to the potential for skin irritation.
Properties: Tonic // antimicrobial // anti-parasitic // anti-inflammation // Aids rheumatic conditions // diuretic // antiseptic.

Thymol & Carvacrol - Oregano 
Thyme & Eugenol - Clove

 

 

Terpenes

Can be subdivided into monoterpenes, sesquiterpenes & diterpenes based on their structure. Terpenes can influence both the initiation and progression of cancerous cells, have the ability to cross the blood-brain barrier and enter brain tissue. According to research, terpenes increase cerebral blood flow, thus indirectly enhancing delivery of oxygen to the brain.
Properties: Antiviral // antibacterial // antifungal // antiseptic // analgesic // protective of DNA // antitumoral // anti-inflammatory // antispasmodic // expectorant // anti-allergenic // stimulative of organs // oxygenating of the tissues // detoxification // both uplifting & relaxing.

Limonene - Lemon, Lime
Pinene - Frankincense, 
Myrcene - Ylang-ylang,
Camphene - Cypress, Neroli
Beta-caryophyllene - Basil, Rosemary
Farnesene - Cedarwood, Sandalwood
Cedrene - Cedar
Cadinene - Ylang-ylang
Sabinene - Carrot seed

 

NB: All Essential oils should always be diluted with a carrier oil and used at the recommended dilution amounts.

REFERENCES:

  • Johnson, Dr. Scott A.. Evidence-Based Essential Oil Therapy: The Ultimate Guide to the Therapeutic and Clinical Application of Essential Oils
  • The Complete Guide to Aromatherapy - Salvatore Battaglia (Second Edition)