Volatile Oils (or Essential Oils

Volatile oils are the odorous and volatile products of various plant and animal species. As they have a tendency to undergo evaporation on being exposed to the air even at an ambient temperature, they are invariably termed as volatile oils, essential oil or ethereal oils. There were specialized secretary structures within the plants which are primarily responsible for the generation of volatile constituents, as shown in the following.

In nature, essential oils play very important roles in plant defense and signaling processes for example, essential oils are involved in plant defense against microorganisms, insects, and herbivores, attraction of pollinating insects and fruit-dispersing animals, water regulation and allelopathic interactions . Also, they are valuable natural products used as raw materials in many fields, such as pharmaceutical, agronomic, food, sanitary, cosmetic, and perfume industries

Physical properties of Essential Oils
1. Liquid at ambient temperature
2. Volatile, (c.f. fixed oils)
3. Colorless liquids with the exception of chamomile oil
4. Their density is lower than water, with the exception clove or cinnamon heavier than water) 5.They have a high refractive index and most of them rotate
6. They are soluble in common organic solvent and liposoluble (lipophilic)

Therapeutic action:
1- Antispasmodic. Ex: Rosmarinus officinalis, Mentha piperita Matricaria chamomilla.
2- Food preservation and cosmetic preparations

3- Flavors for foods and confections and in the spice, perfume, and cosmetic trades.

BASIC CHEMISTRY OF ESSENTIAL OILS
Essential oils consist of various chemical constituents that contribute to their aroma and therapeutic properties. They are made by plants in order to protect them from predators, pests, bacteria and fungi, and to attract pollinators. Generally, the chemical constituents contained in essential oils are made up of blocks of hydrogen, carbon and oxygen molecules. Several different classes of molecules can be found in essential oils; each varying in structure, solubility, evaporation rate and therapeutic properties.