Volatile oils and related terpenoids-Methods of obtaining volatile oils, chemistry, their medicinal and commercial uses, biosynthesis of some important volatile oils used as drugs.

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Nuzhat Tasnim Amin, Lecturer, Dept. of Pharmacy, Varendra University
Volatile Oil
Volatile oil:
Volatile oil are the odorous constituents of plant parts which evaporates to air at normal
temperature. They are also called essential oils because they represent the essences or the
odoriferous constituents of the plant parts.
Chemically they are composed of hydrocarbon of general formula (C5H8)n and oxygenated,
hydrogenated and dehydrogenated derivatives of hydrocarbon. The odor and taste of volatile
oil is mainly determined by these originated derivatives. All the volatile oils are vegetable
origin.
Properties of volatile oil:
1. Volatile oils are colorless liquid and are lighter than water.
2. Most volatile oil possess very pleasant and characteristic odor which vary from
specimen to another.
3. They have high refractive indices (1.42-1.61)
4. They are generally optically active.
5. They are immiscible with water but are freely soluble in ether, alcohol, chloroform,
acetone etc.
6. When shaken with a sufficient amount of water, the odorous principle of the oil is partly
dissolved.
Uses of volatile oil:
1. Volatile oil is used for their therapeutic action, for flavoring (oil of lemon), in
perfumery (oil of rose) or as starting materials for the synthesis of other compounds (oil
of turpentine).
2. They are used as a counterirritant in inflammation and rheumatism.
3. They have carminative, digestive, spasmolytic, stimulant, bactericidal, antiseptic,
disinfectant, diuretic and anthelmintic properties.
4. The volatile oil is employed widely as flavors for foods and confections and in the spice,
perfume and cosmetic trades.
5. Powdered volatile oil are used as condiments.
6. They are used for the manufacture of soaps and toiletries.
7. It is used as flavoring agents to mask the taste and smell of unpleasant medicines.
Different methods of obtaining volatile oils:
There are four methods available for the extraction of volatile oils from plant parts. These
methods are-
A. Distillation

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Nuzhat Tasnim Amin, Lecturer, Dept. of Pharmacy, Varendra University
B. Expression
C. Extraction by means of volatile solvent
D. Adsorption in purified fat.
A. Distillation: Distillation is a method of separating mixtures based on differences in
volatility of components in a boiling liquid mixture. Distillation is a unit operation, or
a physical separation process, and not a chemical reaction. The method of distillation
depends on the condition of the plant material. Three types of distillation are of
commonly used:
a) Water distillation
b) Direct steam distillation
c) Water and steam distillation.
a) Water distillation: This process is applied to the dried and heat stable plant materials.
Turpentine oil is obtained by this method.
The dried plant parts are placed into the distilling chamber with enough water. Then the mixture
is heated until both the volatile oil and water is condensed in the condensing chamber. Then
the aqueous layer is extracted with a solvent.
Advantages: The overall distillation process is very simple.
Disadvantages:
i. Only dried material can be used in this method.
ii. Decomposition may occur in these substances which are not heat stable.
iii. There is a chance for ester linkage to undergo hydrolysis.

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Nuzhat Tasnim Amin, Lecturer, Dept. of Pharmacy, Varendra University
b) Direct steam distillation: This method is applicable to the fresh plant parts which are
heat stable. Spearmint and peppermint oil are obtained by this method.
In this process the plant material containing oils are cut into small pieces and placed directly
into a metal distillation tank on a truck bed. The truck is driven to a distilling shed where steam
is passed from the bottom of the tank. The plant material is still green and contains considerable
natural moistures, therefore, maceration is unnecessary. Steam is forced through the fresh herb
and carries the oil droplets through a vapor pipe attached at the top of the tank in the condensing
chamber.
Advantages:
i. Lower temperature is used.
ii. Maceration is unnecessary because the plant material contains considerable
amount of natural moisture.
iii. It is a quick process.
iv. Hydrolysis and decomposition are minimum.
Disadvantages:
i. Only fresh plant material is used for this method.
ii. Sophisticated equipment is needed, so it is expensive.
c) Water and steam distillation: This process is employed for either dried or fresh
substances that may be injured by direct boiling. Cinnamon oil and clove oil are
obtained in this method.
In this case, dried material is ground and covered with a layer of water. Steam is passed through
the macerated mixture, because the oil could be impaired by direct boiling. The generated
steam is then piped into the container holding the drug. The oily layer of the condensed
distillate is separated from the aqueous layer or marketed without further processing.

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Nuzhat Tasnim Amin, Lecturer, Dept. of Pharmacy, Varendra University
Advantage:
i. Any type of plant material whether fresh or dried can be used.
ii. Because of avoiding direct boiling, the possibility of decomposition is less than
water distillation.
Disadvantages:
i. Steam temperature is needed to be high.
ii. Maceration is necessary.
B. Expression: Those volatile oils which undergo degradation or decomposition by
distillation are usually obtained by this method. E.g. Lemon oil, orange oil.
Expression involve puncturing the oil glands by rolling the fruit over a lined sharp projection.
The oils from the glands is removed and the oil is washed by a fine spray of water. The resulting
oil water emulsion is separated by centrifugation.

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Nuzhat Tasnim Amin, Lecturer, Dept. of Pharmacy, Varendra University
Advantages: The volatile oil is obtained by this method without degradation or decomposition.
Disadvantages:
i. Due to centrifugation long time is needed.
ii. Dried material cannot be used.
C. Extraction with volatile solvent: In the perfume industry, most of the modern essential
oil is obtained by this costly method. Volatile solvents such as petroleum ether and
benzene are used for this purpose. The volatile oils are soluble in these solvents. The
solvents can be easily evaporated and the dried volatile oil can be obtained.
Advantages:
i. Compared with distillation, solvent extraction has advantages such as
low energy consumption, large production capacity, fast action, easy
continuous operation and ease of automation.
ii. Extracted oil have a more natural odor.
Disadvantages: The disadvantage of Ether is, it is highly flammable and highly volatile.
D. Adsorption in purified fat/ Enfleurage method: This method is extensively used in
the production of perfumes and pomades.
In this method odorless fixed oil and fats are spread in a thin layer on glass plates. The flower
petals are placed on the fat for few hours, then removed and a new layer of petals is introduced
and continue this. After the oil is adsorbed on the fat, it is removed from fat by extraction with
alcohol. This process is known as enfleurage.
Advantages: Chemical decomposition doesn’t occur.
Disadvantages: It is a long-time process.

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Nuzhat Tasnim Amin, Lecturer, Dept. of Pharmacy, Varendra University
Difference between volatile oil, fixed oil and fat are given below:
Volatile oil Fixed oil
Volatile oil is volatile in nature Fixed oil is not volatile in
nature.
Chemically they are hydrocarbon
and their oxygenated,
hydrogenated and
dehydrogenated derivatives.
Fixed oils are esters of long
chain fatty acid and
glycerol.
They are colorless liquid at
normal temperature.
They are liquid at normal
temperature.
Volatile oils cannot be saponified
with alkalis.
Fixed oil can be saponified
with alkalis
They do not become rancid on
exposure to air and light.
They become rancid on
exposure to air and light.
Volatile oils are obtained from
plants by distillation process.
Fixed oils are obtained by
extraction and expression.
On exposure to light and air, they
oxidize and resinify.
They do not oxidize and
resinify but become rancid.
Soybean oil, rapeseed
oil, canola, sunflower oil,
safflower oil, peanut oil,
cottonseed oil
Vegetable oil
Coconut oil, palm oil, rice bran
oils
Tropical oils,
Lemon oil, Cinnamon oil,
Lemongrass oil, Clary sage,
Lavender oil, Tea tree oil,
Eucalyptus, Rosemary oil, Sweet
orange, Peppermint oil
Essential Oil/Volatile oil
Cottonseed oil, linseed oil,
sesame oil, hemp seed oil, castor
beans oil, almond oil
Fixed oil
In chemistry, volatility is a material quality which describes how readily a substance vaporizes.
Saponification is a process that involves conversion of fat, oil or lipid into soap and alcohol by the action of heat
in the presence of aqueous alkali.

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Nuzhat Tasnim Amin, Lecturer, Dept. of Pharmacy, Varendra University
Isoprene unit
Isoprene, or 2-methyl-1,3-butadiene, is a common organic compound with the formula
CH2=C(CH3)-CH=CH2. In its pure form it is a colorless volatile liquid. Isoprene is produced
by many plants, and its polymers are the main component of natural rubber. C.G. Williams
named the compound in 1860 after obtaining it from thermal decomposition (pyrolysis) of
natural rubber; he correctly deduced the empirical formula C5H8.
Terpene:
Terpenes are a large and diverse class of organic compounds produced by a variety of plants.
Terpenes can be defined as the hydrocarbons having the empirical formula (C5H8)n and the
term terpenoids represent the hydrocarbons as well as the oxygenated derivatives.
Types: Terpenes may be classified by the number of isoprene units in the molecule.
1. Hemiterpenes consist of a single isoprene unit. Example: prenol and isovaleric acid.
2. Monoterpenes consist of two isoprene units and have the molecular formula of C10H16.
Example: geraniol, limonene.
3. Sesquiterpenes consist of three isoprene units and have the molecular formula of
C15H24. Example: humulene, farnesol.
4. Diterpenes are composed of four isoprene units and have the molecular formula of
C20H32. Examples: cafestol.
5. Sesterterpenes consist of 25 carbons and five isoprene units. Example:
geranylfarnesol.
6. Triterpenes consist of six isoprene units and have the molecular formula C30H48.
Example: Squalene
7. Tetraterpenes contain eight isoprene units and have the molecular formula C40H64.
Example: lycopene.
8. Polyterpenes consist of long chains of many isoprene units. Example: Natural rubber

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Nuzhat Tasnim Amin, Lecturer, Dept. of Pharmacy, Varendra University
Chemical classification of volatile oils:
TYPE EXAMPLE STRUCTURE
Hydrocarbons
Monoterpene α- pinene
Sesquiterpene α- cadinene
Alcohols Geraniol
Alcohols and esters Borneol
Aldehydes Cinnamaldehyde
Ketones Camphor
Phenols Eugenol

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Nuzhat Tasnim Amin, Lecturer, Dept. of Pharmacy, Varendra University
Phenolic ethers Anethol
Peroxides Ascaridole

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Nuzhat Tasnim Amin, Lecture, Dept. of Pharmacy, Varendra University
Volatile Oil
Alcoholic Volatile Oil
Coriander
Botanical source: Coriandrum sativum
Chemical constituents: Coriander contain volatile oil 1%. The prominent of these are linalool,
pinene, limonene and cymene. It also contains small amount of geraniol, borneol, p-cymene, fixed
oil etc.
Uses:
1. It is used as a flavoring agent to conceal the odor of other medicine.
2. It has stimulant, carminative, diuretic and stomachic effect.
Sandalwood
Botanical source: Santalum album
Chemical constituents: The main odorous and medicinal constituents of Sandalwood is santalol.
The other constituents are hydrocarbon santene, the alcohol santenol and the acid α and β santalic
acid.
Uses:
1. Sandalwood oil is highly used in perfumery creations and as flavoring agent.
2. It has an important place in soaps, face creams, toilet powder etc.
3. It is also used as urinary antiseptic, stimulant and in the treatment of bronchitis.

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Nuzhat Tasnim Amin, Lecture, Dept. of Pharmacy, Varendra University
Aldehyde volatile oil
Cinnamon bark
Botanical source: Cinnamomum cassia
Chemical constituents: The main constituent of the oil is cinnamic aldehyde. The other
component identified are limonene, p-cymene, linalool, β- caryophyllene and eugenol.
Uses:
1. It is used as a flavoring agent.
2. It has carminative, pungent, antiseptic and aromatic properties.
3. It is a powerful germicide.
4. It is employed as counter irritants in the treatment of rheumatism and inflammations.
Lemon peel
Botanical source: Citrus limon
Chemical constituents: Contain vit- C, volatile oil, glycoside and ca- oxalate. The volatile oil
contains limonene, citral, geranyl acetate. Also contain linalool, terpenol.
Use:
1. Stomachic and carminative
2. As a flavoring agent.
3. In medicine and confectionary.

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Nuzhat Tasnim Amin, Lecture, Dept. of Pharmacy, Varendra University
Esters volatile oil
Peppermint
Botanical source: Mentha piperita.
Chemical constituents: Peppermint oil mainly contains menthol (50 – 90) %. The other
compound identified are menthone, limonene, cadinene, cineol, amyl alcohol, acetic acid etc.
Uses:
1. It is used as a flavoring agent in pharmaceutical products, dental preparation, soaps etc.
2. It is used as an antipruritic.
3. Menthol is used on the skin or mucus membrane as a counter irritant, antiseptic and
stimulant.
4. It also has some carminative properties.
Lavender
Botanical source: Lavender intermedia
Chemical constituents: The fresh flowering spikes contain 0.5% of volatile oil of which 30-60%
linalyl acetate, Linalol, cinol and terpene -4 ol.
Uses:
1. In toiletry and perfumery industries.
2. Used in ointment to mask disagreeable odor.

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Nuzhat Tasnim Amin, Lecture, Dept. of Pharmacy, Varendra University
Ketones
Camphor
Botanical source: Cinnamomum camphora.
Chemical Constituents: It contain up to 20% camphor.
Uses:
1. Camphor is readily absorbed through the skin produces a feeling of coolness similar to that
of menthol and acts as slight local anesthetic.
2. Camphor is a topical anti-pruritic, rubefacient.
3. Camphor is used in several cough preparations.
Phenols
Clove
Botanical source: Eugenia caryophyllus
Chemical constituents: Clove oil contains volatile oil 14-21% which are eugenol, acetyl eugenol,
caryophyllene etc.
Uses:
1. Clove oil or eugenol is effective in toothache remedy due to dental cavities.
2. Eugenol is mixed with zinc oxide to form a temporary tooth cavity filling.
3. It is effective for fever reduction, as a mosquito repellent.
4. It has some antiseptic, carminative and counter irritant properties.
5. Also used as a stimulant, aromatic and a flavoring agent.

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Nuzhat Tasnim Amin, Lecture, Dept. of Pharmacy, Varendra University
Ajowan oil
Botanical source: Trachyspermum ammi.
Chemical constituents: The principle constituents of Ajowan oil is phenol mainly thymol,
carvacrol, pinenes and cymene.
Use:
1. It is used as an antiseptic and carminative.
2. It is useful as an expectorant in emphysema, bronchial pneumonia and other respiratory
ailments.
(Emphysema is a long-term, progressive disease of the lungs that primarily causes
shortness of breath due to over-inflation of the alveoli)
Ethers
Fennel
Botanical source: Foeniculum vulgarea
Chemical constituents: It contains volatile oil (2-6) %. The chief constituents are anethol. Also
contains small quantities of pinene, limonene.
Uses:
1. Used as a flavoring agent, carminative and aromatic.
2. Anethol is used in mouth and dental preparations.