In the variety of the plant world a man took a note of the plants with a pleasant or sharp smell in the antiquity already. Later when the man learned to extract separate aromatic substances from the plants, he found out the valuable properties of these substances.
So what are "essential oils"?
Essential oils are fragrant volatile matters, which are contained in different parts of plants, mainly in flowers, leaves, fruit, roots. The content of the essential oils depends on a number of reasons (place of growth, weather conditions, the time of collection of raw material and others) and varies from 0,1% to 4%.
Most of the essential oils represent liquids at the normal temperature, but can be solid and semi-fluid as well( iris), depending on the temperature (rose). Some of them solidify at the room temperature or a little bit lower, others at 0° or a less and very little essential oils do not solidify at all. At the same time congelation is never complete, because not all the oil becomes solid, just one or several components of it do. Specific gravity of the essential oils, with the exception of some essential oils, varies between 0,8 - 0,98. There are oils which are heavier than water. Their specific gravity however never exceeds 1,2. All the essential oils are volatile, especially at heating. The boiling temperature of the essential oils varies in rather wide limits. Oils are sublimated from 140° to 260° C. They all can be distilled at lowered pressure or with water steam.
The chemical content of essential oils is not homogeneous, but, summarizing, one can speak about the presence of:
vitamins (К, А, Е, F, С, РР, Р, В, D and others),
macro- and microelements (phosphorus, potassium, magnesium, copper, etc.),
acids (ascorbic, gallic, stearic, palmitic acids and etc.),
alkaloids and so on.
All the essential oils have an ability to absorb oxygen from the air. At oxidation most of the oils change their smell, namely, with little exception, worsen it. Essential oils practically don't dissolve in water, but form with it the emulsion. All the essential oils easily dissolve in organic dissolvent (ether, chloroform, sulphureous carbon, acetone, methyl chloride, fats and fatty oils).
The presence of antiphlogistic, antibacterial, antiviral and antihelminthic activity are the most typical pharmacological properties. Besides some essential oils influence on the activity of cardiovascular, respiratory, digestive, urogenital, immune, central nervous systems, have tranquilizing and sedative properties. Essential oils stimulate nervous system, help at nervous situations, reduce irritability, emotional excitability, normalize sleep, remove impulsive obsession, raise capacity for work. Some essential oils contain hundreds of components which haven't been completely studied yet. Oils have synergistic action - their healing properties are based on a certain combination of components, and a certain complex is important.
Nowadays there are a lot of methods of manufacture of essential oils. Which one to choose, depends on the properties of the vegetable raw material.
The main ways are: cold pressing (for citrus fruit, including lemon and bergamot) and steam distillation (anise, clove, mint and other oils). Besides extraction by organic solvent can be used (hexane, alcohol, methanol).
In addition to 100% of natural oils there are plenty of so-called "natural identical" products on the market today. As a matter of fact these are essential oils, but manufactured not from the plants, but synthetically. The reason is that perfumery and aromatizers production demand the constancy of fragrance, while natural raw material is subjected to changes depending on weather conditions. Most of the natural identical oils are identical to 96% only, and the rest 4% are practically impossible to reproduce. These oils have no therapeutic effect. The only irrefutable advantage of artificial essential oils is low price in comparison with natural oils.