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An essential oil is not the only aromatic substance used in aromatherapy; concretes, absolutes, resins, resinoids and oleoresins are not essential oils but do have aromatic uses, especially for perfumery purposes.

Therapeutic Oils in Aromatherapy Use

Essential oils are often open to adulteration in aromatherapy use; in addition, fragrance oils and hydrosols are also in general “aromatherapy” use, although they therapeutically different in their use to essential oils (if at all).  The chemistry of an essential oil is complex and, depending from which plant it was extracted or distilled from, the properties of an essential oil can vary.

Furthermore, some plant material is used to produce essential oils and other substances such as concretes, absolutes, resins, resinoids and oleoresins; some plants are capable of producing the material for one or more of these substances, whereas some not are not.  Therefore, it is not surprising to have difficulty in deciding if an essential oil really is an essential oil
What is an Essential Oil?

Essential oils are obtained through a process of extraction or steam distillation of the various parts of a plant; essential oils are obtained from the roots, flowers, leaves, seeds and bark of a plant.  A pure essential oil is obtained from a single species and is “adulterated” with other botanical species.  It is the “aroma” of the plant (from tiny glands, sacs and hairs) that is captured in an essential oil and used therapeutically in aromatherapy.

Solvent Extraction : Concretes and Absolutes

Some plants are used to produce concretes and absolutes; concretes and absolutes are not essential oils, although some plant material can be used to produce both essential oils and concretes and absolutes.  Due to methods of production, concretes and absolutes are not “pure” like essential oils and therefore do not hold the same therapeutic properties.

Concretes are prepared from plant material by the use of a hydrocarbon solvent to produce a waxy, solid substance which is widely used in the perfumery industry; absolutes are prepared from a concrete by alcohol extraction and are again of much use to the perfumery industry.

Resins, Resinoids and Oleoresins

Resins are the natural material (a gum substance) exuded from the bark of a tree when it is cut; resinoids are the result of a resin extraction, by use of a hydrocarbon solvent.  Absolute resins are also produced using an alcohol solvent.  Oleoresins are the natural material exuded from plants and extracted using a solvent; oleoresins produce an end result of essential oils and resins (and solvents).

Plants That Produce Concretes and Absolutes

Examples of plants that produce concretes and absolutes include:

- Mimosa (Acacia dealbata)
-  Cassie (Acacia farnesiana)
- Marigold (Calendula officinalis) – absolute
-Tonka (Dipteryx odorata)
- Oakmoss (Evernia prunastri)
- Gardenia (Gardenia jasminoides)
- Jasmine (Jasminum officinale) – note, an 'essential oil' is steam distilled from the absolute, and not the plant, resulting in jasmine absolute and not jasmine essential oil, as many believe
- Melilotus (Melilotus officinalis)
- Narcissus (Narcissus poeticus)
- Linden (Tilia x vulgaris)
- Violet (Viola odorata).

Plants That Produce Resinoids and Oleoresins

Examples of plants that produce resinoids and oleoresins include:

- Deertongue (Carphephorus odoratissimus) -oleoresin
- Opopanax (Commiphora erythraea) – resinoid in addition to an essential oil
- Myrrh (Commiphora myrrha) – resinoid in addition to an essential oil
- Nutmeg (Myristica fragrans) – oleoresin (from mace) in addition to an essential oil
- Patchouli (Pogostemon cablin) – resinoid in addition to an essential oil
- Benzoin (Styrax benzoin) – resinoid (or resin absolute)
- Vanilla (Vanilla planifolia) – resinoid.

Identifying Essential Oils, Absolutes and Resins

In aromatherapy, pure essential oils are primarily used for therapeutic use; a plant material that has been solvently extracted will not be “pure” and will not hold the same therapeutic powers of a pure essential oil.  However, concretes and absolutes have a place in the perfumery world and resinoids and oleoresins have uses too.

It is important to identify which plants are capable of producing essential oils, concretes, absolutes, resins, resinoids and oleoresins; some plants can be extracted to produce all of these substances, some only produce an essential oil, and some only produce concretes and/or absolutes or resinoids.

References:

- Lawless, Julia 1995 The Illustrated Encyclopedia of Essential Oils UK:Thorsons
- Price, Shirley 2000 Aromatherapy Workbook UK:Thorsons

This article was written by Sharon Falsetto and appeared in its original format on Suite101 as When is an Essential Oil Not an Essential Oil?

It is expressively prohibited to copy or use this article in any way unless written permission is given by the author Sharon Falsetto.  If it is discovered that copyright laws have not been complied with, legal action will be pursued by the author Sharon Falsetto.


CopyrightSharonFalsetto2010 All Rights Reserved
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