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The class of essential oils includes compounds of similar physical and chemical properties. Essential oils consist of several ingredients, mainly of monoterpenes. They are liquid and volatile. They contain fragrances that give the essential oil and thus their plant its characteristic scent.
Essential oils are substances from plants. The plants contains - with some exceptions - the essential oil in a low single-digit percentage. In the plants, depending on the plant and vegetation phase, the proportion of essential oil in different plant parts varies greatly. Thus, in the flowers often found more essential oil than in the roots of the plant.
Essential oils are generally extracted by steam distillation. With this method on gets only the essential oil of the plant. With an extraction, for example, fats, waxes, and other plant materials are dissolved, which must be isolated from the essential oil.
Other variations of the extraction of essential oils is the pressing of fruit peels, especially with citrus fruits, or the “Enfleurage” method. Here, the plant material is deposited on a layer of fat. Alcohol is then used to dissolve the essential oil, which not solves the fat.
The essential oil contains several ingredients. Therefore, there are no common properties. But in some cases there are a similar chemical behavior. Most of the ingredients are volatile and have a boiling point between 50°C and 320°C. Especially the monoterpens have a low boiling point. Essential oils can be dissolved in most of the organic solvents and in fats and oils.
Furthermore, the properties of the individual ingredients are variable. Thus, esters, ethers, epoxides, alcohols, acids and aldehydes are found in essential oils.
With a few exceptions it is generally possible to divide the ingredients of essential oils in three groups. On the one hand we find the terpenes and of these most cyclic monoterpenes and in addition also acyclic monoterpenes and sesquiterpenes like bisabolol find as a part of the essential oil of bergamot orange.
The phenylpropanoids are the second group. They consists of a benzene ring (= phenyl), which may be substituted, and a modified propyl group (= propanoid). Well-known representatives are the cinnamic aldehyde which is found in cinnamon bark oil, as well as the estragole which is found in many essential oils such as the tarragon, basil, chervil and anise.
Unbranched alkanes and alkenes with a long chain are the third group. Among these for example the polyketides. Nonanal for example is represented in cinnamon and orange essential oil represented. Another member of this group is the unsaturated undecantriene.
The composition of the essential oil is highly dependent on several factors. Here, the interplay of these factors lead to differences in the composition of the essential oil even in the same plant species. The following factors play a role:
According to a study of Hans Krüger from the Julius Kühn Institute, for example, the amount of methyl eugenol is reducing with advancing harvest date.
Essential oils are mainly synthesized in young tissue, which possesses an intense metabolism. From there it is directed into the storage locations. Since the concentrated essential oil can be toxic to cells, there are specific locations that protects the surrounding cells from this toxic effect. Here it is possible to store the essential oil without damaging the plant.
Due to their aroma essential oils are used in various products. As a fragrance it is used in perfumes and cosmetics. Today, the essential oil (which is expensive) is displaced by synthetic materials, mainly a mixture of the monoterpenes of the essential oil. Furthermore, they are used for the flavoring of foodstuffs. Especially the spices spices, which contains essential oils, are widely used in the kitchen.
Essential oils can generally show several effects:
Due to their ingredients, such as the terpenes, essential oils can lead to skin irritation after application to mucous membranes and skin. With the inhalation of essential oils the outflow of mucus is facilitated. This effect, however, strongly depends on the concentration of the essential oil. The antimicrobial effect supports the healthy at revenge diseases. The inhalation of, for example eucalyptus oil is considered as a home remedy for cough and dry mucous membranes.
Essential oils exhibit an antimicrobial effect on micro-organisms, which may vary depending on the essential oil. One of the highest antimicrobial activity shows thyme oil.
Aromatherapy is the practice of using essential oils as fragrances. It is used as a support of psychotherapeutic processes. The fragrances are used to trigger associations that act either relaxing or stimulating. Essential oils use the sense of smell. In addition - and this represents the difference to a scent therapy - the essential oils have pharmacological effects, such as those shown in the previous paragraph.
Esoteric concepts such as energy fields, the balance of influence of body, mind and soul will not be discussed.
The perception of odors is done via the olfactory epithelium and the classification of these odors is learned. Thus, it is possible to refine his sense of smell through exercises, but the sense of smell can also result from environmental influences or other influences (such as smoking). The body arranges smells of different mechanisms:
The body is able to evaluate subjectively pleasant or unpleasant odors. While some scents this review is genetically predetermined (eg, the unpleasant odor of rotten meat), these perceptions are shaped in the course of development of a person by social constraints.
By storing fragrance experience in long-term memory of the brain directly with the related, other experiences, such as time, space and emotions, fragrances can contribute to change the mood.
The deliberate use of essential oils can be supportive to a psychotherapeutic treatment. In addition to these effects, the inhalation of essential oils can lead to physiological effects in your body. As an example, the jasmine oil can reduces stress-related high blood pressure and has an antispasmodic effect.
Krüger, Hans; Ätherische Öle–Variabilität in Arznei-und Gewürzpflanzen; Julius-Kühn-Archiv, 422 (2010): S-70.