An Introduction to
the Chemistry of Essential Oils

Essential oils are made up of many chemical constituents. No two oils are alike in their structure or their effects. Below is a list of some of the main constituents found in essential oils:

· Alcohols
· Aldehydes
· Esters
· Ethers
· Ketones
· Phenols
· Terpenes

Each of these can be broken down into numerous smaller units. Take terpenes, for example. This classification includes monoterpenes, sesquiterpenes, sesquiterpene lactones, Di-terpenes, etc. Listing them all is beyond the scope of this brief overview.

Each constituent has its own action, or effects. For example, the ketones found in lavender, hyssop and patchouly, stimulate cell regeneration. Whereas, phenols, found in oregano and thyme oil, are highly antimicrobial.

Because the chemistry of essential oils is very complex, essential oils are diverse in their effects. This also supports their antimicrobial effects, because the wide variety of antiseptic compounds in essential oils makes the mutation of microorganisms extremely difficult. In l985, Dr. Jean C. Lapraz stated that no microbe could survive in the presence of the essential oils of cinnamon or oregano.

Basic Chemical Structure

Essential oils molecules are made up primarily of carbon, hydrogen, and oxygen.

The aromatic constituents of essential oils are built from hydrocarbon chains (carbon and hydrogen atoms). They are normally joined together in ring-like chemical structures. The chains are held together by carbon atoms linked together. Oxygen, hydrogen, nitrogen, sulfur, and other carbon atoms attach at various points of the chain, to make up the different oils.

The aromatic-ring structure of essential oils is much more complex than the simpler, linear carbon-hydrogen structure of fatty oils. Essential oils also contain sulfur and nitrogen atoms that fatty oils do not have.

The basic building block of many essential oils is a five-carbon molecule called an isoprene. Most essential oils are built from isoprene. This is the building block that makes up the terpenoids.

When two isoprene units link together, they create a monoterpene; when three join, they create a sesquiterpene; and so forth. Triterpenoids are some of the largest molecules found in essential oils. They consist of 30 carbon atoms -- or six isoprene units linked together.

Different molecules in the same essential oil can exert different effects. For example, the azulene in German chamomile has powerful anti-inflammatory compounds. The bisobolol German chamomile also contains has sedative and mood-balancing properties. Other compounds in German chamomile perform still different functions, such as speeding the regeneration of tissue.

This is because the chemical structure of an essential oil determines its function. Phenols generally create antibacterial activity. Carvacrols have anti-inflammatory activity and Limonines are antiviral.

A single species of plant can have several different chemotypes based on its chemical composition. A plant such as basil grown in one area might produce an essential oil with a completely different chemistry than basil grown in another location.

This discussion is meant as an introduction to a vast field of study that is beyond the scope of this website. For more information, the following publications may be helpful:

Essential Oil Chemistry by D. Williams. Lavandes and Lavandins by Christiane Meunier, Aix-en-Provence 1985. Phytochemical Dictionary edited by Jeffrey B. Harborne and Herbert Baxter. Journal of Essential Oil Research (JEOR) Tel: (630) 653-2155 Fax: 630 653-2192. Aromatherapie by Jean Valnet, M.D., Healing Arts Press, Rochester, VT, 1982. Aromatherapy by René-Maurice Gattefossé, Ph.D., Girardot, Paris 1937. L'aromathérapie exactement by Daniel Pénoël, M.D., and Pierre Franchomme.