Volatile Oils & Terpenoids.

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.


  • 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 classNo. of Isoprene units(C5H8 )Formula
Isoprene1C5 H8
Monoterpenes2C10 H16
Sesquiterpens3C15 H24
Diterpenes4C20 H32
Triterpenes6C30 H48
Tetraterpenes8C40 H64
Pentaterpens9C50 H80
PolyterpensN(C5 H8 )n
  • Uses: -

  • They are used as carminatives, flavoring agents, counter-irritants, deodorants, analgesics, stimulants, and diuretics. etc.

Topics u may like to read