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Terpenoids are the hydrocarbons of plant origin having general formula (C5H8)n.
Terpenoids are a group of naturally occurring compounds,
In leaves
Fruits of higher plants, conifers, citrus, and eucalyptus
A few of them are solids e.g. camphor.
They are also oxygenated, hydrogenated and dehydrogenated derivatives.
Basically, terpenoids are volatile substances that give fragrance or aroma to plants.
They are also known as essential oils because they represent essence.
The term ‘terpene’ was assigned to the compounds after the isolation of volatile liquid turpentine from pine trees.
Physical Properties
They are colourless, fragrant liquids lighter than water and volatile in nature impart fragrance to plants and flowers.
They are soluble in organic solvents, alcohol and fixed oils and usually insoluble in water.
On thermal decomposition, most of the terpenoids yield isoprene as one of the product.
They are optically active.
It becomes darker in colour upon long-standing in air or sunlight.
Volatile oils should be stored in well-closed airtight umber colour containers or bottles.
Chemical Properties
They are open-chain or cyclic unsaturated compounds having one or more double bonds.
They give addition reaction with hydrogen, halogen, acids, etc and addition products possess antiseptic properties.
They undergo polymerization and dehydrogenation.
They are easily oxidized nearly by all the oxidizing agents.
A mixture of isomeric hydrocarbons (molecular formula C10H16)
The simpler mono- and sesquiterpenes are the chief constituents of essential oils obtained from sap and tissues of some plants and trees.
The di- and tri- terpenoids are not steam volatile, and are obtained from plant and tree gums and resins.
Tetraterpenoids form a separate group of compounds called carotenoids.
Myrcene
Isoprene Unit
Pinene
Limonene
References
1. W.C.Evans, Trease and Evans Pharmacognosy, 16th edition, W.B. Sounders & Co., London, 2009.
2. Mohammad Ali. Pharmacognosy and Phytochemistry, CBS Publishers & Distribution, New Delhi.
3. Text book of Pharmacognosy by C.K. Kokate, Purohit, Gokhlae (2007), 37th Edition, Nirali Prakashan, New Delhi.
4. Herbal drug industry by R.D. Choudhary (1996), Ist Edn, Eastern Publisher, New Delhi.
5. Essentials of Pharmacognosy, Dr.SH.Ansari, IInd edition, Birla publications, New Delhi, 2007
6. Herbal Cosmetics by H.Pande, Asia Pacific Business press, Inc, New Delhi.
7. A.N. Kalia, Textbook of Industrial Pharmacognosy, CBS Publishers, New Delhi, 2005.
8. R Endress, Plant cell Biotechnology, Springer-Verlag, Berlin, 1994.
9. Pharmacognosy & Pharmacobiotechnology. James Bobbers, Marilyn KS, VE Tylor.
10. The formulation and preparation of cosmetic, fragrances and flavours.
11. Remington‘s Pharmaceutical sciences. 12. Text Book of Biotechnology by Vyas and Dixit. 13. Text Book of Biotechnology by R.C. Dubey.
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