| Abstract (english) | Essential oils (volatile oils, ethereal oils) are the odorous principles
found in various plant parts. Depending on the plant family, essential oils may occur
in specialized secretory structures such as glandular hairs (Lamiaceae), modified parenchyma
cells (Piperaceae), oil-tubes called vitae (Umbelliferae), or in lysigenous or
schyzogenous passages (Pinaceae). Chemical constituents of essential oils can be divided
into 2 broad classes, based on their biosynthetic origin: (1) terpene derivatives,
and (2) compounds formed via the shikimic acid-phenylpropanoid route. Although essential
oils differ greately in their chemical constitution, they have a number of physical
properties in common. They possess characteristic odors, they are characterized
by high refractive indices, most of them are optically active, and their specific rotation
is often a valuable diagnostic property. They are immiscible with water, but they
are sufficiently soluble to impart their odor to water. The aromatic waters are dependent
on this slight solubility. However, they are soluble in ehter, alcohol and most organic
solvents.
Essential oils are usually obtained by distillation of the plant parts containing oil.
Three types of distillation are used by industrial firms: (1) water, (2) water and
steam, and (3) direct steam. In the parfume industry, most of the modern essential oil
production is accomplished by extraction, using solvent system based on such volatile
solvents as petroleum ether or benzene. The process known as enfleurage was formerly
used extensively in the production of parfumes and pomades and was based on
absorption of essential oil by purified fat.
The volatile oil drugs and the separated oils are most commonly used for flavoring
purposes, but some of them possess additional therapeutic properties (antimicrobial,
antifungal, anthelmintic, carminative, expectorant, diuretic, antiphlogistic etc.).
In addition to their pharmaceutic uses, essential oils are employed widely as flavors
for foods and confections and in the spice, parfume and cosmetic trades. |
