ADVANCED HERBOLOGY Volatile Oils Lesson 6 · Extraction methods employ various solvents other than...

ADVANCED HERBOLOGY Volatile Oils Lesson 6

©2017 Wild Rose College of Natural Healing 1 Terry Willard Cl.H PhD.

Lesson 6

Volatile Oils

In this lesson we shall take a closer look at the valuable role that volatile oils can play in our health and well-being. This is one of the most complex groups from a chemical standpoint, and perhaps the most fascinating from a herbalist's point of view. Use of volatile oils varies from the esoteric to the practical pharmaceutical uses. The key feature of volatile oils is the obvious one - they can easily vaporize from the source material. In this gaseous state they stimulate the olfactory senses to present odor. This gives us two pieces of useful information; firstly, it is easy to tell if the plant has volatile oil and secondly, that attribute is escaping. This, of course, means that quality control is essential when using plants for their volatile attributes. Excessive boiling or prolonged storage can severely reduce the volatile quality of the plant material. Let's begin by first understanding what volatile oils are, methods of obtaining them, their various classifications and some clinical applications.

Please read from Introduction, p. 215, to the bottom of p. 216



Volatile oils, also known as essential oils, are odorous compounds found within a variety of different plant parts. They are incredibly complex substances, with some fragrances comprised of hundreds of individual components. It is because of their evaporation potential at ordinary temperatures that essential oils are also called ‘volatile.’ Volatile oils provide a number of different physiological functions for the plant from which they are produced. These functions range from environmental protection, natural pesticide control and inhibition of growth of other nearby plants, to a role in the plant's fertilization process. Some authors feel that the terpenoid structure might support some form of ‘communication', especially since their structural variety allows for the transfer of selective ‘biological messages'.

Please read from top of p. 217 to p. 219, The Modern use of Aromatherapy

Methods Of Obtaining Essential Oils The most common methods used to produce essential oils are based on the principles of water-steam distillation, cold pressing and extraction. 1. Distillation

a) Water b) Water and Steam c) Direct Steam

2. Cold Pressing (Expression) 3. Extraction

a) Enfleurage (Cold Fat Extraction) b) Maceration (Hot Fat Extraction) c) Solvents d) Hyper/Supercritical Carbon Dioxide

Water Distillation The most common method for obtaining essential oils is simple water distillation. The plant material (whole or crushed) is completely covered with water and brought to a boil. The steam that is produced contains both water and volatile oil and is collected in the condensing chamber. The oil is then separated from the water.



Water distillation is performed for those oils with constituents which may be affected by heat, such as Rose and Orange Blossom.

Water and Steam Distillation In this process, steam is generated in a separate chamber and then passed through the compartment, which contains plant material and water. This ensures that the temperature of the water in the maceration mixture does not reach the boiling point. The essential oil floats to the surface of the mixture and is then separated.

Direct Steam Direct steam is employed primarily for industrial production of essential oils from fresh plant material, e.g. Peppermint. Because of the high water content of the fresh material, no maceration is necessary. The fresh plant is placed on a grid or suspended in a basket and steam is forced through the material. Oil droplets are carried, along with steam, to the condensing chamber and then separated.

Cold Pressing and Extraction Other methods for obtaining volatile oils, as described in the text, are necessary depending on which particular oils are to be extracted. Citrus oils, for example, are collected exclusively by the process of cold pressing (expression).



Extraction methods employ various solvents other than water, e.g., hexane, petroleum, ether, benzene or acetone. Cold and hot enfleurages are extraction methods, which use animal fat as the solvent.

Hyper/Supercritical carbon dioxide (CO2) extraction is a technique, which allows for the extraction of extremely heat-sensitive essential oils such as Lilac and Lily-of-the-Valley. It is carried out at a very low temperature but very high pressure (200 times Atmospheric.) Under these situations, carbon dioxide gas behaves as a liquid.

(Please refer to p 348 of text for more detail).

Please read from p 219, The Modern use of Aromatherapy to the bottom of page 223.

Aromatherapy Aromatherapy is an art and science that involves the skilled use of essential oils for their physical, psychological and aesthetic influences. Even though this course is not meant to teach the student aromatherapy (we have other courses for that), many students in the past have been interested in a basic knowledge of it. One of our instructors, Blaine



Andrusek, who teaches Aromatherapy, shared with me a simple diagram he uses as a general rule for therapeutics of an aroma based on its physical location in a plant.

I am not suggesting that all aromatherapy can be ‘distilled' down into this basic picture, but it can give a simple overview.

Anatomy of Aromatherapy Our sense of smell links directly with the limbic region of our brain. This region has been likened to a ‘reptile brain', as it generates emotional and physiological responses on an instinctual level. It is because of the limbic region that a certain fragrance can take us "back in a flash" to the days of our childhood, and trigger memories, both pleasant and unpleasant. Pheromones, powerful ‘scent messengers' unique to each individual, play a significant role in sexual stimulation.

Please read from p. 224, Division of Volatile Oils, to Hydrocarbon Volatile Oils, p.225

In this section we will be reviewing essential oils based upon their functional groups. First, let's take a closer look at the basic structure of volatile oils.

Structure of Volatile Oils Volatile oils are built from the isoprene building block, C5H8, a functional unit of many plant constituents. We were first introduced to this structure in Chapter 2 (Glycosides) - you may wish to review that section at this time.



The majority of essential oils are monoterpenoids ( C10H16, two isoprene units; e.g., limonene), though many are sesquiterpenoids (C15H24) and diterpenoids (C20H32), (three and four isoprene units, respectively.) Beyond this number of isoprene units, the essential oil molecule becomes too heavy to be considered ‘volatile.' It should be noted that the complexity of volatile oils makes it so there can be many types of chemicals to make up the scent signature of a plant. Even more important is the fact that varieties of different “chemotypes” (a chemically distinct entity in a plant or microorganism, with differences in the composition of the secondary metabolites) can cause variation within a given species. Distinguishing between chemotypes can be most accurately confirmed by using gas chromatography, but some individuals have developed organoleptic ‘skills’ in this area. One of the major attributes of monoterpenes is their antiseptic effect. The following list gives you the antiseptic power in relative terms:

Divisions of Volatile Oils As with many other plant molecules, the attached functional group confers bioactivity to the volatile oils and also determines their nomenclature. Let's now review classifications of volatile oils based upon their functional groups, as outlined in the text:

1. Hydrocarbon 2. Alcohol 3. Aldehyde 4. Ketone 5. Phenol 6. Phenolic Ester 7. Oxide 8. Ester

Phenol carvone citronella menthol linalol citral geraniol thymol

= 1 (standard) = x 1.5 (the strength of phenol) = x 3.8 = x 4.0 = x 5.0 = x 5.2 = x 7.1 = x 20.0

Isoprene Unit



Please read from Hydrocarbon Volatile Oils, p. 225, to Alcohol Volatile Oils, p. 229

Hydrocarbon Volatile Oils These are the simplest of the terpene structures, consisting solely of hydrogen and carbon atoms arranged in either a linear or cyclic form. One of the most common monoterpene hydrocarbons (2 isoprene units) is limonene, a monocyclic volatile oil present in Citrus, Bergamot and Turpentine. Pinene is a dicyclic monoterpene found in conifers, Black Pepper, Nutmeg and Angelica. Hydrocarbon volatile oils also occur as sesquiterpenes, such as zingiberene and selinene present in Ginger and Celery, respectively. Humulene is a sesquiterpene volatile oil present in the cones (strobiles) of Hops.

Hops (Humulus lupulus)

Hops is used primarily for its calming, sedating action, whether on the digestive tract or the nervous system. It is a very useful aid to digestion or to assist in falling asleep. Hops is considered to have an estrogenic-like influence and, as such, may be beneficial in addressing some menopausal symptoms.

Please read from Alcohol Volatile Oils, p. 229, to Aldehyde Volatile Oils, p.232

Alcohol Volatile Oils Alcohol terpenoids can be identified because of the attachment of a hydroxyl (-OH) group to a carbon of the terpene molecule. Alcohol volatile oils are generally toning and energizing, e.g., Peppermint, Eucalyptus and Tea Tree oils. Many alcohol volatile oils are valued for their antiseptic and anti-inflammatory properties. Essential oil of German Chamomile is especially noted for its anti-inflammatory effect due to the high content of the sesquiterpene alcohol bisabolol.

Peppermint (Mentha piperita)

Menthol, a monoterpene alcohol, is the major component of the volatile oil of Peppermint and gives Peppermint its distinctive fragrance. Menthol is very useful as a counterirritant and an antiseptic. It is also antiviral and aids in decongesting blocked respiratory passages. The stimulating property of essential oil of Peppermint benefits mental fatigue.

Hops (Humulus lupulus)

Peppermint (Mentha piperita)



Cardamon (Elettaria cardamomum) The essential oil of the seed of Cardamom is comprised primarily of the alcohol monoterpenoid borneol. It is mainly used as a carminative and to promote digestion. Cardamon essential oil is also used in perfumery and for flavouring liqueurs.

Juniper (Juniperus communis)

Essential oil of Juniper is obtained from the dried berries of this botanical and is both diuretic and antiseptic. Whereas Juniper oil alone can be irritating to the kidneys, especially if they are inflamed, preparations of the whole berry are considered to be soothing. It is advisable to include demulcents such as Marshmallow root in all formulations for kidney and bladder conditions.

Please read from Aldehyde Volatile Oils, p. 232, to Ketone Volatile Oils, p.235

Aldehyde Volatile Oils Aldehydes are formed when there is a double-bond between an oxygen atom and the end-carbon it is attached to (note: the carbon cannot be in the middle of a chain.) Hydrogen is attached to at least one of the other carbon bonds. The familiar fragrance of Lemon Balm (Melissa officinalis) is due to the aldehyde terpenoids citral and citronellal. In contrast to the energizing property of Peppermint and other alcohol volatile oils, essential oils of the aldehyde category are generally sedating.

Cinnamon (Cinnamomum spp.)

Essential oil of Cinnamon is derived from the leaves, bark, stems, and roots of this evergreen tree. The leaf oil is antiseptic and warming and can be used to treat nausea, indigestion and hypertension. It is best, though, to avoid this essential oil for nausea or vomiting associated with pregnancy.

Citronella (Andropogon nardus, Cymbopogon nardus)

Cardamon (Elettaria cardamomum)

Juniper (Juniper communis)

Cinnamon (Cinnamomum spp.)



The main use of this essential oil is as an insect repellant and an anti-viral agent. Please read from Ketone Volatile Oils, p. 235, to Phenol Volatile

Oils, p. 238

Ketone Volatile Oils Like aldehydes, ketones are comprised of an oxygen double-bonded to a carbon atom. Ketones differ from aldehydes in that the bonding is not to an end-carbon but to one within the carbon chain or aromatic (cyclic) ring. Please Note Errata in Text: Ketones (1st paragraph p. 235), say "Ketone terpenoids... This is called a carboxyl group." should be a carbonyl group. (Carboxyl groups are COOH (carboxylic acid); carbonyl is a carbon with a double-bonded oxygen - no hydroxy group.) Ketones are primarily employed for their mucolytic action (ability to decongest mucous secretions.) Because some ketone-containing essential oils are potentially neurotoxic, proper dosing of these oils is necessary. Thujone (Wormwood, Sage, Thuja), pulegone (Pennyroyal) and pinocamphone (Hyssop) are examples of such essential oils. An extremely beneficial effect of certain ketone-containing essences is their ability to stimulate the formation of healthy new tissue. Helichrysum (Helychrisum italicum) essential oil is especially noted for its exceptional wound healing properties.

Buchu (Barosma betulina)

The major component of the essential oil of Buchu is the ketone terpenoid diosphenol, which gives Buchu its antiseptic property. Buchu is very effective for genito-urinary tract disorders such as cystitis and prostatitis.

Wormwood (Artemisia absinthium)

Thujone in essential oil of Wormwood is known to be a potent neurotoxin when used inappropriately. Wormwood is an effective vermifuge and digestive aid, with herbal preparations containing low or no thujone still used for these purposes. Please read from Phenol Volatile Oils, p. 238, to Phenylpropane

Volatile Oils, p. 239

Citronella (Andropogon/Cymboprogon sp.)

Buchu (Barosma betulina)

Wormwood (Artemisia absinthium)



Phenol Volatile Oils Phenols are formed when an alcoholic hydroxyl group (OH) attaches to an aromatic benzene ring. Since pure phenol does not occur in nature, essential oils, which contain phenols, also have a carbon side chain attached to the benzene ring. Phenol-containing essential oils are generally invigorating, immuno-stimulating and strongly antiseptic. All phenolic compounds are potentially hepatotoxic, a concern only if they are used in high doses for extended periods of time.

Thyme (Thymus vulgaris)

Thyme essential oil contains thymol, which is greater than 20 times more antiseptic than most phenols (see the table above on page 6). Thyme also contains lesser amounts of essential oil carvacrol. Thyme oil is excellent in steam inhalations for respiratory conditions and as a general stimulant. Please read from Phenylpropane Volatile Oils, p. 239, to Oxide

Volatile Oils, p.243

Phenylpropane Volatile Oils Phenylpropane essential oils occur either as esters or ethers and contain an aromatic phenyl group with a propane (three carbon) side chain. This side chain contains a double bond that creates more reactivity with the aromatic ring. Phenylpropane essential oils are stimulating and antiseptic but can be irritating to the skin.

Clove (Eugenia caryophyllus)

Clove bud oil is composed of 85% phenolic substances, primarily the phenylpropane eugenol. Eugenol has a free hydroxyl group attached, which confers antiseptic properties similar to those of the phenols (e.g., thymol.) Clove oil is a time-honoured remedy for toothaches due to its local anesthetic quality. It is also employed in aromatherapy for its antiseptic, stimulant and carminative properties. Other important phenylpropane essential oils include anethole (Anise, Fennel), cinnamic aldehyde (Cinnamon), apiole (Parsley) and safrole (Sassafras.) Apiole is considered abortificient and should therefore not be

Thyme (Thymus vulgaris)

Clove (Eugenia caryophyllus)



used during pregnancy. Safrole, in large amounts used over an extended time, can cause systemic fatty tissue degeneration of the heart, liver and kidneys. Because the essential oil of Sassafras contains 80% safrole, this herb has been subjected to restrictions and is no longer used to flavour root beer.

Please read from Oxide Volatile Oils, bottom p. 243, to Ester Volatile Oils, p.245

Oxide Volatile Oils Oxide volatile oils, as the name implies, contain oxygen in their structure. Terpene oxides have as their functional group a single oxygen bonded into the terpene ring. The most common of the terpene oxides is eucalyptol (also known as cineol.) Eucalyptol is found in many essential oils, especially those of the Myrtaceae family (Eucalyptus, Tea Tree.) Ethers may also be considered a type of oxide. They occur when oxygen forms a link between two unconnected carbon chains, as opposed to being incorporated into the ring structure. The medicinally important ether volatile oils were covered under the previous section on phenylpropanoids (e.g., anethole from Anise.)

Eucalyptus (Eucalyptus spp.)

Best known for its ability to relieve chest and sinus congestion, essential oil of Eucalyptus is an excellent expectorant and antiseptic. The volatile oil contains up to 70% of the terpene oxide eucalyptol. Its invigorating and balancing properties also make it a useful addition in rubs for rheumatism and arthritis.

Please read from Ester Volatile Oils, p. 245, to beginning of Summary, p. 247

Ester Volatile Oils Esters are produced from the reaction of an alcohol with an acid. Esterification often produces very fragrant oil; hence the practice of aging perfumes to improve their bouquet. Common characteristics of ester-containing volatile oils are their soothing and balancing actions, as well as general anti-inflammatory and spasmolytic effects. Esters are also very noteworthy for their antifungal property.

Eucalyptus (Eucalyptus spp.)



Lavender (Lavandula angustifolia)

Errata - typo p. 245 of the text. - botanical name for Lavender is missing the ‘a' in angustifolia Linalyl acetate is one of the most common ester volatile oils and is found in sizeable concentrations in Lavender essential oil (up to 35% linalyl acetate.) It contributes to Lavender's relaxing nervine and anti-inflammatory properties. Lavender oil is an excellent first-aid treatment for burns.

Rosemary (Rosmarinus officinalis)

Bornyl acetate is another commonly encountered ester essential oil. It is found in the essential oil of Rosemary and has a general stimulant effect upon the entire circulation. Rosemary has long been renowned for its memory-enhancing ability.

Wintergreen (Gaultheria procumbens)

Methyl Salicylate is the esterified form of salicylic acid and is present in Wintergreen (and also Meadowsweet, from which it was first isolated.) Oil of Wintergreen (98% methyl salicylate) is used topically for its aspirin-like, pain-relieving action.

Lavender (Lavandula angustifolia)

Rosemary (Rosmarinus officinalis)

Wintergreen (Gaultheria procumbens)



Summary In this lesson we looked at the increasing importance of essential or volatile oils and many of their therapeutic applications. Methods of obtaining essential oils and their classifications based upon chemical structure were discussed, as were the individual properties of each of these categories along with specific botanical examples. The potential neurotoxicity of some ketone volatile oils was noted, as exemplified by thujone in Wormwood, Thuja and Sage. Potential hepatoxicity of certain phenol essential oils, such as thymol in Thyme, was also discussed. The relationship between the sense of smell and the limbic system was highlighted to portray the immediate impact that essential oils can also have upon our emotional health and well being.

Please read from Summary to end of chapter

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