Volatile Oils.
- Synonyms: (Ethereal oils, Essential oils)
- Volatile oils are odorous principles of plants & animal origin chemically they are made of isoprene units (C5H8).
- Isoprene units (C5H8) combines to form monoterpenes (C10H16), Sesquiterpenes (C15H24) & diterpenes (C20H32).
- The characteristic odor of volatile oil is due to oxygenated compounds of terpenes.
- They evaporate of room temp without producing stain on the paper.
- As they evaporate at room temperature they are called as "Ethereal Oils".
- As they represent an essence of the plant they are also called as "Essential Oils."
- Physical Properties
• They are insoluble in water, soluble in organic solvent. Except for clove oil they are lighter than H2O
• They have a high refractive index.
• They are found in various plant families like, Zingiberaceae, Lauraceae, Umbelliferae, Labiatae. - Uses: -
- They are used as a carminative,
- Favoring agent,
- Counter-irritant,
- Dental analgesic,
- Diuretic.
- Classification of volatile oils:
1. Alcohol: Peppermint, Cardamom, rose, sandalwood.
2. Aldehyde: Cinnamon, lemon, Orange peel lemon grass, bitter almond.
3. Ester: Gaultheria, lavender, mustard.
4. Hydrocarbons: Turpentine, black pepper, hops
5. Ketones: Caraway, spearmint, buchu, camphor.
6. Oxides: Chenopodium, eucalyptus
7. Phenolic ether: Anise, fennel, nutmeg.
8. Phenol volatile oil: Clove, thyme, creosotes. - Chemical Tests for Volatile oil
- The presence of volatile of oil can be detected by the following tests.
1) Take a thin section of the drug & add a drop of tincture alkana. The red color is produced which indicates the presence of volatile oil.
2) Take a thin Section of drug & add an alcoholic solution of Sudan III – Red color, which indicates the presence of volatile oil.
Extraction of Volatile Oils:
1. Hydro distillation Method: -
- The drug is powdered & kept in a distillation plant, which is made of copper or stainless steel.
- The steam is introduced into the boiler around the crude drug.
- The volatile oil comes out with the steam, which is collected. The layer of volatile oil is separated from the water.
2. Enfleurage method: -
- This method is used for extraction delicate volatile oil.
- Petals of the flower are spread on a layer of fat present on glass sheets.
- The fat absorbs the volatile oil.
- After few days old petals are removed & fresh petals are spread on the fat.
- This process is continued till fat becomes saturated with the volatile oil, the fat with the volatile oil is known as the pomade.
- The volatile oil is extracted from the pomade.
3) Ecuelle Method: -
- In this method, there is round bowl to which a hollow pipe is attached. Inside the bowl, there are pointed projections Peel of lemon or orange is kept in a bowl.
- Bowl is rotated with the machine.
- The projections break oil glands of the peel.
- The volatile oil and liquid are collected from the pipe.
- The volatile oil is separated from the liquid.
- e.g. Household juice extractors.
4) Sponge Method: -
- The sponge is kept in water.
- Peel of lemon or orange is brought near the sponge by hands and squeezed mechanically.
- The sponge is removed & pressed to collect volatile oil & water. The volatile oil is separated from water by distillation.
TERPENOIDS
- The term Terpene represents hydrocarbons (C5 H8 )n.
- While terpenoids include hydrocarbons, as well as their oxygenated derivatives.
- Terpenes & Terpenoid are found in all volatile oil.
- Properties of terpenes & terpenoid: -
- Terpenes and terpenoid are found in all essential oils.
- Therefore their properties are similar to them.
Classification of terpenoids
| Name of class | No. of Isoprene units(C5H8 ) | Formula |
| Isoprene | 1 | C5 H8 |
| Monoterpenes | 2 | C10 H16 |
| Sesquiterpens | 3 | C15 H24 |
| Diterpenes | 4 | C20 H32 |
| Triterpenes | 6 | C30 H48 |
| Tetraterpenes | 8 | C40 H64 |
| Pentaterpens | 9 | C50 H80 |
| Polyterpens | N | (C5 H8 )n |
- Uses: -
- They are used as carminatives, flavoring agents, counter-irritants, deodorants, analgesics, stimulants, and diuretics. etc.