Volatile Oils

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VOLATILE OILS
ESSENTIAL OILS
AROMATIC OILS
ETHEREAL OILS

Volatile oils are usually responsible for the odor of a plant. Volatile, or essential, oils evaporate with air. They can contain hundreds of constituents, the highest of which are terpenes. Hydrocarbons (as with acillin, from garlic), alcohols, aldehydes (this group includes cinnamon oil, orange oil, lemon peel, lemon oil, hamamelis water, and citronella oil, whose medicinal purposes include the astringent quality of witch hazel). Therapeutically, volatile oils have many uses. They can serve as a mode of transportation, to distribute a medicine equally throughout the body. They can act as antiseptics. Volatile oils tend to stimulate tissues they come in contact with, hence they can be rubefacients, counter-irritants, and/or vasodilators. Internally, volatile oils may cause an increase in saliva, perspiration, peristalsis, and/or stimulate the heart muscle (Cabrera, 40).
Brief Introduction to Essential Oil Chemistry

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.
Biosynthesis of Essential Oils
The basic building block of many essential oils is a five-carbon molecule called an isoprene (C5H8 ). Most essential oils are built from isoprene units . 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; ; forth create Diterpene ; five create sesterterpene . 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.
In Pharmacology
Although there is currently something of a dismissive attitude concerning essential oils in pharmacology, various essential oils retain considerable popular use, partly in fringe medicine and partly in popular remedies. Unfortunately, this makes it difficult to obtain reliable references concerning their pharmacological merits.
Taken by mouth, many essential oils can be dangerous in high concentrations. Typical effects begin with a burning feeling, followed by salivation. In the stomach, the effect is carminative, relaxing the gastric sphincter and encouraging eructation (belching). Further down the gut, the effect typically is antispasmodic.
Typical ingredients for such applications include eucalyptus oils, menthol, capsaicin, anise and camphor. Other essential oils work well in these applications, but it is notable that others offer no significant benefit. This illustrates the fact that different essential oils may have drastically different pharmacology. Those that do work well for upper respiratory tract and bronchial problems act variously as mild expectorants and decongestants. Some act as locally anaesthetic counterirritants, and thereby exert an antitussive effect.
Some essential oils, such as those of juniper and agathosma are valued for their diuretic effects. With relatively recent concerns about the overuse of antibacterial agents, many essential oils have seen a resurgence in off-label use for such properties and are being examined for this use clinically.
Many essential oils affect the skin and mucous membranes in ways that variously are valuable or harmful. They are used in antiseptics and liniments in particular. Typically, they produce rubefacient irritation at first, and then counterirritant numbness. Turpentine oil and camphor are two typical examples of oils that cause such effects. Menthol and some others produce a feeling of cold followed by a sense of burning. This is caused by its effect on heat-sensing nerve endings. Some essential oils, such as clove oil or eugenol, were popular for many years in dentistry as antiseptics and local anaesthetics. Thymol also is well known for its antiseptic effects.

Use in aromatherapy
Aromatherapy is a form of alternative medicine in which healing effects are ascribed to the aromatic compounds in essential oils and other plant extracts. Many common essential oils have medicinal properties that have been applied in folk medicine since ancient times and are still widely used today. For example, many essential oils have antiseptic properties. Many are also claimed to have an uplifting effect on the mind. Such claims, if meaningful, are not necessarily false, but are difficult to quantify in the light of the sheer variability of the materials used in the practice .

Professor Dr. Saad Ali Ihsan
Ph.D. in Pharmacognosy & Medicinal Plants