Essential oils are the aromatic liquids extracted from various parts of plants, flowers, trees and bushes. These extracts contain a variety of chemicals that determine the fragrance and properties of the oils. According to Julia Lawless, author of "The Illustrated Encyclopedia of Essential Oils," essential oils are generally made up of chemicals that use carbon, hydrogen and oxygen, which can be subdivided into hydrocarbons and oxygenated compounds.
Terpenes
Terpenes are hydrocarbons that possess anti-inflammatory and anti-bacterial properties. Terpenes can be found as monoterpenes, sesquiterpenes and diterpenes. According to the Institute of Chemistry in Berlin, terpenes include pinene, nerol, citral, camphor, menthol, limonene, nerolidol and farnesol. Essential oils that contain terpenes include the majority of citrus oils, such as lemon and grapefruit, as well as pine, rosemary and chamomile.
Esters
Esters are found in almost all essential oils and are a subgroup of the oxygenated compounds. Esters include linalyl acetate, geranyl acetate, bornyl acetate, eugenyl acetate and lavendulyl acetate. Esters are often fungicidal and relaxing and have a fruity aroma. Essential oils that contain esters include bergamot, clary sage, lavender, geranium, orange and sweet marjoram.
Aldehydes
Aldehydes are another subgroup of the oxygenated compounds. Aldehydes are very calming and have antiseptic properties. They are common in lemon-scented essential oils. Citral, citronellal, neural, benzaldehyde, cinnamic aldehyde, cuminic aldehyde and perillaldehyde are aldehydes found in many common essential oils such as cinnamon, cassia, lemon eucalyptus, lemon verbena, melissa, lemongrass and citronella.
Ketones
Although some ketones, an oxygenated compound, are toxic, such as those found in mugwort, tansy and wormwood, nontoxic ketones are found in jasmine, hyssop and fennel oil. Ketones are considered beneficial in relieving respiratory conditions since they aid the flow of mucus. Camphor, carvone, methone, methyl nonyl ketone and pinocamphone are all ketones found in essential oils.
Alcohols
Not to be confused with alcoholic beverages such as vodka and tequila, alcohols found in essential oils are compounds that tend to have antiseptic and antiviral properties. Common alcohols include linalol, geraniol and citronellol, which yields the aldehyde, citronellal. Essential oils that contain these alcohols are citronella, rosewood, lavender, rose, lemon, eucalyptus and palmarosa.
Phenols
Phenols tend to have strong antibacterial properties. Phenols found in essential oils include eugenol, thymol, carvacrol, methyl eugenol, methyl chavicol and anethole. Essential oils of clove, West Indian bay, thyme, oregano and savory contain phenols.
Oxides
Oxides are generally found in essential oils that are of a camphoraceous nature. Oils containing oxides include eucalyptus, which contains one of the most important oxides, cineol, as well as rosemary, cinnamon, melissa and basil. Cineol is important because of its expectorant effect, making it helpful in treating colds, cough and congestion.
Other ingredients
Other constituents of essential oils include coumarins, furocoumarins and ethers. Coumarins tend to aid in lowering blood pressure and are calming and refreshing. Coumarins are found in cinnamon, cassia and lavender. Furocoumarins are derivatives of coumarins and can cause skin sensitivity. Ethers are rare, but can be found in aniseed, basil and tarragon oils.
References
- Institute of Chemistry: Terpenes
- Esoteric Oils: The Chemistry of Essential Oils
- Wiley Interscience: Trans-Cinnamaldehyde from Cinnamomum zeylanicum Bark Essential Oil Reduces the Clindamycin Resistance of Clostridium difficile in vitro
- Abundant Health: Essential Oils Constituents
- Carnegie Mellon: Essential Oils - The Aromatic Compound
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