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Chapter-9
Terpenoids
INTRODUCTION:
Essential oil or ethereal oil is defined as the volatile oil obtained by the
steam distillation of plants. There is a distinction between fixed or fatty oils and
volatile oils. Their volatility (boiling point) and plant origin are characteristic properties
of these oils.
BITTER ALMOND AND MUSTARD OIL -- Obtained enzymatically followed by
steam distillation
LEMON OILS AND ORANGE OILS -- Obtained by pressing the fruits.
OCIMUM OR EUCALYPTUS OIL -- Extraction by organic solvents.
All are included in essential oils.
The oldest of volatile oil ` EAU DE COLOGNE’ prepared in 1725 by Johann
Maria Farina in Cologne is still extracted in same fashion and is being used in the
cosmetics. It was found that the oils contain chiefly liquid and more or less volatile
compounds of many classes of organic substances. Thus, we find, acyclic and
isocyclic hydrocarbons and their oxygenated derivatives. Some contain sulphur or
nitrogen.
Essential can be broadly classified in to four groups depending upon the
reactive groups.
1. ESTERS: This group include Methyl esters of salicylic acid; Oil of
winter green.
2. ALDEHYDES: This group include cinnamic aldehyde of cinnamon.
3. ETHERS: This group contain oil of clove (eugenol)
4. TERPENES: Camphor, menthol , oil of lemon etc. are included in this group.
There are basic differences between fixed or fatty oils and volatile or essential
oils.
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DIFFERENCE BETWEEN ESSENTIAL OIL AND FATTY OIL
Sr. No.
ESSENTIAL OR
FIXED OR FATTY OIL
VOLATILE OIL
1.
Boiling points are less than 100 0C
1. Boiling points are higher than
100 0C
2.
Can be steam distilled without
2. Decompose prior to volatisation.
any change in its biological property
3.
Produce temporary greasy spot on
3. Produce permanent greasy spot on
paper
4.
paper.
Example: Eugenol, cinnamic aldehyde
4. Example: Linoleic acid, Arachidonic
etc.
5.
Uses: Fragrance, perfume etc
acid etc.
5. Uses: Edible oil in food
preparation
________________________________________________________
There are four classes of essential oils .
1. TERPENES RELATED TO ISOPRENE OR ISOPENTENE.
2. STRAIGHT CHAIN COMPOUNDS NOT CONTAINING SNY SIDE CHAIN
3. BENZENE DERIVATIVES
4. MISCELLANEOUS GROUP HAVING
INCLUDED IN FIRST THREE GROUPS.
(1)
VARIED
STRUCTURES
NOT
TERPENES:
They are either hydro carbons ( C 10 H 16 ) or oxygen containing compound ( C 10
H 16 O ) or ( C 10 H 18 O ). The name terpene was given by KEKULE.
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THYME CAMPHOR ---- THYMOL
PEPPERMINT ------------ MENTHOL
There are compounds which have less number of carbon and hydrogens. The
common isoprene i.e. ( C
5
H
8
). Members of the C
group are often referred as
10
mono-terpenes. Compounds having a more distant connection with the terpenes, but
still containing features which link them with terpene structures are sometimes called
terpenoids or isoterpenoids.
There are several difficulties in studying the terpenes.
1.
Terpenes are unstable and tend to re-arrange intra-molecular groups. This
property is an obstacle in their studies.
2.
They are liquids so that thorough fractionation is necessary to separate the
constituents, which boil within a restricted range.
3.
The boiling point difference between several essential oils is vary narrow leading
to improper purification of active principles.
O.WALLACH who is considered as `MESIAH OF TERPENES’ differentiated around
500 essential oils on the basis of their crystallisation properties.
C – C - C -C
1. HEMI-TERPENES
C5

C
2. TERPENES
3. SESQUI-TERPENE
C – C - C - C ------- C – C - C - C


C
C
3 X
C – C - C -C
C 10
C 15

C
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4. DI-TERPENE
4
X
C – C - C -C
C 20

C
5. TRI-TERPENE
6
X
C – C - C -C
C 30

C
6. TETRA-TERPENE
8 X
C – C - C -C
C 40

C
7. POLY-TERPENE
n X
C – C - C -C
Cn

C
Geraniol ( C10 H18 O ) : Chief constituent of rose and geranium oil.
Linalool ( C10 H18 O ) : Component of Lavender oil
α- terpeniol : Oil of hyacinth
There are several isomers of geraniol also. Lycopene, a red pigment of tomato
also falls under the group of terpene. It is a tetra-terpene having a molecular formula
of C
40
H
56
having 32 carbon atoms in the ring with 8 methyl side chain having 14
double bonds. The β- carotene and Vitamin E also falls under this group of terpenes
with several isoprene ring structure.
2. STRAIGHT CHAIN HYDROCARBONS AND
THEIR OXYGEN DERIVATIVES:
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These essential oils of hydro carbons from n- haptane; which forms 90 % of oil
of Pinus sabiniana and Pinus jeffreyi to compounds with 15 – 35 carbon atoms. The
higher paraffin-like material may be crystallise during cooling and storage are called
`stereoptenes’ . The alcohols, aldehyde and ketones are quite often contained in the
low boiling fractions of the volatile oils. The typical example is Leaf alcohol ( cis or
trans – hexen- 3 ol-1 ).
CH3 – CH2 - CH = CH – CH2 – CH2 – OH
This alcohol is responsible for the odour of grasses, green leaves etc.
In this group, there are also included many fatty acids which occur free or
esterified with alcohol with different degree of saturation. They are present in the
VOLATILE OILS OF FRUITS.
3. BENZENE DERIVATIVES:
The third major group comprise a number of flavour and perfume constituents
derived from benzene specifically from n – propyl benzene. The aromatic ring may
carry hydroxy, methoxy and methylene dioxy groups; the propyl side chain ma y
contain hydroxyl or carboxyl group. e.g. Coumarin
STRUCTURE OF COUMARIN
Many members of this group are related through chemical reaction. On
isomerisation, eugenol can be converted to Vanillin, the flavouring principle of
Vanilla bean.
ISOMERISATION OF EUGENOL TO VANNILIN
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The propyl benzene derivatives take part in the synthesis of plant pigments
such as anthocyanins and flavones. In view of their structural similarity, straight chain
hydrocarbons are generally considered connected with fatty acid metabolism, while
benzene and propyl benzene derivatives are connected with carbohydrate
metabolism.
4. MISCELLANEOUS GROUP:
The representatives of this group are the compounds, which are not included in
the above mentioned three groups. They are incidental and often rather specific for a
few spp. or genera of the plants.
1. Allyl isothiocyanate : CH2 = CH – CH2 – N = C = S
2.Di-allyl
sulphide:CH2
=
CH
–
CH2
–
S
-CH2
MUSTARD OIL
–
CH
=
CH2
OIL
OF
GARLIC
3. Butyl propenyl di-sulphide : CH3 –CH2 – CH – S – S – CH = CH – CH3

CH3
ASAFOETIDA
4. INDOLE:
STRUCTURE
METHYL ANTHRANILATE
Note: No. (4) and (5) are pleasant smelling principle of orange blossom and
jasmine flavour respectively.
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FUNCTIONS OF ESSENTIAL OILS :
PLANTS:
1. Some of the oil-bearing plants are attractive to certain animals / insects,
whereas, some are repellent. This property is useful in more effective
cross-pollination through insects’ frequent visits.
2. Some of the essential oil producing plants imparts protection against
insect / animal predation. The presence of essential oils in the plant
makes the plant unpalatable e.g. there is little insect / animal damage to
Ocimum plants because of the presence of eugenol.
3. In some cases, these oils act as reserve food material.
4. It also helps in sealing a wound of the plant.
5. It acts as varnish (oily layer) to prevent excessive evaporation of water.
They cause reversible lowering of permeability of water and water-soluble
substances, thereby decreasing the transpiration in plants.
6. Act as bactericidal/ fungicidal agent in some cases.
MEDICINAL USES:
1. Terpenes act as mild irritant.
2. It acts as bactericidal and fungicidal agent used in the preparation of
ointments.
3. Volatile oils are employed for the treatment of urogenital infections.
4. It stimulates repair of tissues and assist in the removal of mucous from
trachea or bronchia. Relieves the tension of the stomach and colon.
5. It acts as anthelmintic (Anti-worms) agent. e.g. Chenopodium oil is used
to remove round-worms, hook-worms and intestinal amoebas (santonine
which is sesqui-terpene used for this purpose).
6. When the action of heart muscle is depressed, camphor may improve
cardiac conditions and remove arrhythmia (Any deviation from the
normal rhythm of heart).
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INDUSTRIAL USES OF ESSENTIAL OILS:
They have a wide and varied use in perfumery, cosmetics and additive in
food industry. In the course of a single day, from morning to night, we use or
consume a great variety of volatile oils either in spices and condiments or in
perfumes or in toilet soap or as scent or in food.
Here is the list some industries, wherein, the essential oils are used. Please take
note; the list is still not complete.
1.
ANIMAL FEED INDUSTRY : Cat food, cattle feed, dog foods etc.
2.
BAKING GOODS INDUSTRY:
Biscuit, cake, icings,
minced meat,
puddings, sandwich, pies etc.
3.
CANNING INDUSTRY: Meat, fish, sauces, soups
4.
CHEWING GUM INDUSTRY: Variety of chewing gums and chocolates.
5. CONDIMENTS: Chilli sauces, salad dressing, pickled
fish, table sauce,
vinegar etc.
6. CONFECTIONARY : Chocolates, jellies, soft centre candies.
7.FOOD INDUSTRY: Cheese, puddings, dehydrated
soups, rennet desserts.
8.HOUSEHOLD: Deodorant, furniture polish, laundry
soap, room spray.
9.
ICE-CREAM INDUSTRY: Used in the preparation of
ice-cream.
10. INSECTICIDE INDUSTRY: Attractants, insect
repellents. Disinfectant sprays.
11.PAINT INDUSTRY: Bituminous paint, enamels, paint and varnish removers,
synthetic coatings, varnish
12.PHARMACEUTICAL
INDUSTRY:
Cough drops, antacids, elixir, hospital
sprays, laxatives, ointments, tonic, vitamin flavour preparation.
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13.PERFUME AND TOILET INDUSTRY: Baby soap, Face cream, cologne, lipstick, lotion, shaving cream, eye shadow, mask etc.
14.PICKLE INDUSTRY: Sweet and sour pickle preparation
15.WINE INDUSTRY: Rum, whisky, wine etc.
16.RUBBER INDUSTRY: Toys, waterproofing, glove,
surgical supplies.
17.
SOAP INDUSTRY: All kind of ordinary and luxury
soaps.
18. SOFT DRINK: Cola drinks, syrups and soft drink
powder.
19.TOBACCO INDUSTRY: Chewing and smoking
tobacco.
The list of industries, where the essential and volatile oils are used, is
endless suggesting its industrial demand and the potential in driving the
economy of the country.
REFERENCE BOOKS:
THE ESSENTAIL OILS : HISTORY, ORIGIN AND PRODUCTION IN PLANTS
: VOLUME
I AND II (1948)
by D. Ernest Gunther , D. Van Nostrand
Company Ltd, New Jersy, USA.
*******
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Enlist INDUSTRIAL USES OF ESSENTIAL OILS ( any five)
What is FUNCTIONS OF ESSENTIAL OILS ?
Compound presence in different crops
1. Allyl isothiocyanate : CH2 = CH – CH2 – N = C = S
2.
MUSTARD OIL
Di-allyl sulphide:CH2 = CH – CH2 – S -CH2 – CH = CH2
OIL OF
GARLIC
3. Butyl propenyl di-sulphide : CH3 –CH2 – CH – S – S – CH = CH – CH3

CH3
ASAFOETIDA
Geraniol ( C10 H18 O ) : Chief constituent of rose and geranium oil.
Linalool ( C10 H18 O ) : Component of Lavender oil
α- terpeniol : Oil of hyacinth
DIFFERENCE BETWEEN ESSENTIAL OIL AND FATTY OIL
Define essential oil
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