Essential Oil: A Concentrated Hydrophobic Liquid

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Essential Oil

  • Essential oil is a concentrated hydrophobic liquid containing volatile aroma compounds from plants.
  • They are usually lipophilic (literally: oil-loving) compounds that usually are not miscible with water. Also, they can be diluted in solvents like pure ethanol and polyethylene glycol.
  • They are also known as volatile oils, ethereal oils or aetherole.
  • They carry a distinctive scent or essence of the plant.
  • They are used in perfumes, cosmetics, soaps, lotions and other products. For flavoring food and drinks and for adding scents to incense and household cleaning products.
  • It is used medicinally for skin treatments to remedies for cancer.
  • Essential oils are derived from various sections of plants barriers – all spices, juniper etc.
SeedsAlmond, cumin
BarkCassia
LeavesBasil, cinnamon, lemon grass
FlowersCannabis, clove, chamomile, lavender
WoodSandalwood
RhizomesValerian
PellOrange
  • Families particularly rich in essential oils includes Compositae (Sunflower), Labiataceae/Lamiaceae (mint), Oleaceae, Myrtaceae (eucalyptus all sp.) etc.
  • Some best essential oils are lemon oil, cinnamon oil, clary sage, lemongrass oil, lavender oil, tea tree oil, eucalyptus.

 

Classification of Essential Oils

Essential oils can be divided into 2 groups-

  1. Monoterpenes
  2. Sequiterpenes
1. Monoterpenes
  • They contain 10 Carbon atoms.
  • They are built up of 2 isoprene units.
  • They are open ring.
  • Simple monoterpenes are widely spread.
  • They tend to occur as component of majority of essential oils.

Monoterpenes can be further divided into 2 groups. They are:

1. Monocyclic Monoterpenes: e.g. Limnonene, menthol, thymol etc. Menthol is a chief monoterpene compound and source of pipermint oil.

2. Bicyclic Monoterpenes: e.g. α-pinene, β-pinene, camphor etc.

https://www.researchgate.net/figure/Fig-2-Natural-products-with-strong-AChE-inhibitory-potency-a-pinene-1-8-cineol_fig2_318012340
2. Sequiterpenes
  • They contain 15 Carbon atoms.
  • They consist of 3 isoprene units. 

    Abscisic Acid
    https://www.sigmaaldrich.com/catalog/substance/2cis4transabscisicacid264321437545211?lang=en&region=US

According to the basic Carbon skeleton, they can be further divided into 3 groups. They are-

  1. Acyclic sequiterpenes
  2. Monocyclic sequiterpenes (Abscisic Acid)
  3. Bicyclic sequiterpenes

 

References:
www.slideshare.net
www.terpenoids.net
www.dictionary.com
Class lecture of Rifat Samad Mam, Assistant Professor, Department of Botany, University of Dhaka