Volatile oils, also known as essential oils, are liquid, volatile compounds found in plants and animals. They evaporate at ordinary temperatures. Chemically, they are derived from terpenes and their oxygenated compounds. Common examples include oils from clove, cinnamon, fennel, and coriander. Distillation is a widely used method to extract volatile oils from plant material, while other methods include solvent extraction, mechanical expression, and enzymatic hydrolysis. Volatile oils have various medicinal and industrial uses such as flavoring agents, fragrances, and antimicrobials.

1. VOLATILE OILS
• Definition :
• The odorous, volatile principles of plant and
animal sources are known as volatile oils. They
are liquid, volatile oils will evaporate or volatize
when exposure at an ordinary temperature and so
they are called ethereal oils. They are also called
as essential oils as they are essences or
concentrated constituents of the plants.

2. General properties of volatile oils
1.They are soluble in alcohol, ether and
other lipid solvents and practically insoluble
in water.
2. They are usually lighter than water.
3. They possess characteristic odours and
they have high refractive index

3. • 4. Most of them are optically active.
• 5. They are secreted in special
structuree such as duct, cell,
schzogenous or lysigenous gland,
trichomes.
• 6. They are commonly found in the
species of Labiatate, Rutaceae,
Piperaceae, Zingeberaceae,

4. • 7. They are present in entire plant or in
any part of the plant.

5. • CHEMICAL NATURE:
• Chemically , they are derived from
terpenes and their oxygenated
compounds. They are made up of isoprene
units ( C5H8) and are usually mono-,
sesqui-, and diterpenes with empirical
formulae as C10H16,C15H24, and C20H32
respectively.

6. • Classification of volatile oils:
• 1. Alcohol volatile oils –Eg Cardamom, Coriander
• 2. Aldehyde volatile oils – Eg Cinnamon, Lemon
peel
• 3. Ester volatile olis – Eg Lavender, Mustard
• 4. Hydrocarbon volatile oils – Eg Turpentine,
Black pepper
• 5. Ketone volatile olis – Eg Caraway, Camphor

7. • 6. Oxide volatile oils – Eg Eucalyptus,
Chenapodium
• 7. Phenolic ether volatile oils – Eg Fennel, Nutmeg
• 8. Phenol volatile oils – Eg Clove

8. Biosynthesis and chemical
composition
• Chemical constituents of volatile oils may
be divided into 2 broad classes, based on
their biosynthetic origin:
1. Terpene derivatives formed via the acetate-
mevalonic acid pathway.
2. Aromatic compounds formed via the
shikimic acid-phenylpropanoid route.

9. Aromatic compounds
OH
OCH3
Eugenol
(clove oil)
OCH3
CH3
Anethole
(anise oils)
CHO
Cinnamaldehyde
(cinnamon oil)
CH2

10. Uses of drugs containing essential oils
Pharmacy
Perfumery
Food technology
Miscellaneous industries (as starting
materials for the synthesis of the active
principles of medicines, vitamins, and
fragrances).

11. Preparation of volatile oils
 The principal methods used in the
preparation of volatile oils from plants
depend on:
1. Distillation in water or steam.
2. Mechanical methods
3. Extraction with solvents.
4. Enzymatic hydrolysis
5. Supercritical fluid extraction

12. 1. Distillation method
• This is the most widely used method for
the extraction of volatile oil
• PROCEDURE – The plant material is
macerated and then steam distilled, when
the essential oils go into distillate from
which they are extracted by pure organic
volatile solvents.

14. • Like Light Petroleum ether.
• However , the method should be used with
a great care , since some essential oils
are decomposed during distillation and
some are hydrolyzed to none or less
fragrant compounds

15. 2. Mechanical methods
• A) Enfleurage method
• B) Eculle method
• Enfleurage method
• It is also known as cold fat extraction

16. Enfleurage method
• It is also known as cold fat extraction
• Used for the extraction of delicate
perfumes from Flower petals

17. Method -
• The fresh flower petals are mechanically
spread on a layer of fatty material, ( A
glass plate is covered with a thin coating
of especially prepared and odourless fat)
allowed to imbibe and the exhausted
petals are replaced by fresh material.

19. • The process is continued till the fatty layer
is saturated with volatile principles, which
are then extracted with lipid solvent like
ethyl alcohol.
• The extract having ethyl alcohol and
essential oils is distilled under reduced
pressure to remove the solvent.

20. • Advantages –
• In case of distillation method , volatile oil
may undergoes hydrolysis, polymerization
or resinification or delicate oils becomes
lost in large volumes of water or where the
flowers continue to produce fragrance
after the harvest effleurage is usually
practiced

21. Ecuelle method ( Expression method)
• It is also known as expression method
• Used for the extraction of citrus oils from
citrus fruits.

22. Method –
• Here oil cells in rind are ruptured
mechanically using pointed projections by
twisting the raw material over them in
Clockwise direction either mechanically
or manually.

23. • The oil is then separated from the juice by
centrifugation.
• The other half of the oil is generally not
extracted and such residue is used for the
isolation of inferior quality of oil by
distillation.

24. • Eg citrus, lemon and grass oils are
extracted by this method

26. 3. Extraction with solvents.•
• Here they are using volatile solvents to
extract the volatile oil. i.e Petroleum ether,
benzene

27. Method –
• Fresh flowers are transferred into specially
constructed extractors at room
temperature and carefully treated with
purified solvent , usually petroleum ether.

28. • The solvent penetrates the flowers and
dissolves the natural perfume together
with some waxes and other albuminous
and coloring matter
• This solution is pumped into an evaporator
and concentrated at low temperature. After
complete evaporation of solvent the flower
oil is obtained.

29. • Application –
• This method is used in perfume industry
for the production of volatile oils using lipid
solvents like petroleum ether or benzene
• Advantages-
• It is quick
• Quality assured and economical method

30. • The decomposition of volatile oil is less as
compared to hydro distillation method
• The solvent distilled off may be reused for
extraction

31. 4. Enzymatic extraction
• Here , the volatile oil is normally found in
plants substances in the form of
odourless glycosidal combination.
However , the odoriferous compounds
are liberated free only by hydrolysis.
• Volatile oil of bitter almond (
Benzaldehyde)

32. CLOVE
• Biological source : It consists of the dried
flower buds of Eugenia caryophyllus
• Family : Myrtaceae
• Chemical constituents :
• 1. Volatile oil ( 16-21%)- Phenol chiefly
Eugenol ( 80-88), Acetyl eugenol (10-15)
and α and β Caryophyllene

33. • 2. Tannins (10 – 13%) – Pyrogallol tannins
• 3. Others substances are Methyl furfural
and dimethyl furfural.

34. Medicinal uses
• Used as an antiseptic
• Used as a stimulant
• Used as a carminative
• Used as flavouring agent
• Used as Local anaesthetic ( eugenol)

35. • Used as spice
• Used in tooth ache
• Used in dental preparations, mouth
washes, oil used in perfumery
• Clove oil and zinc oxide are used in
temporary filling of dental cavities

36. Diagnostic characters
• Odour : Aromatic
• Pollen grains : Small, biconvex with
rounded or triangular
• Oil glands : Fragments of parenchyma
with entire or portion of oil glands
• Aerenchyma : Portion of loose
parenchyma

37. • Fibres : Sclerenchymatous fibres
associated with parenchymatous cells
• Sclerieds : Oval to sub rectangular,
thickened walls having numerous simple or
branched pits
• Calcium oxalate : In the form of cluster
crystals
• When starch is present then it is from

38. CINNAMON
• Biological source:
• It consists of dried inner bark of the plant
cinnamomum zeylanicum .
• Family : Lauraceae
• It contains not less than 1% of volatile oil.

39. Chemical constituents :
• It contains about 0.5 to 1.0% of volatile oil.
• 1.2% of tannins (Phlobatannins)
• Mucilage
• Calcium oxalate
• Starch
• Sweet substance known as mannitol
• Cinnamon oil contains 60-70% of cinnamic
aldehyde, 5-10% of eugenol, and benzaldehyde,
cumminaldehyde and other terpines.

40. Uses :
• Carminative
• Stomachic
• Mild astringent
• Flavouring agent
• Aromatic
• Used as a spice and condiment
• Preparation of candy, dentrifies and perfumes
• Oil is powerful germicide

41. Diagnostic characters :
• 1. Organoleptic characters:
▫ Colour - reddish brown powder
▫ Odour - characteristic, pleasant and aromatic
▫ Taste - characteristic, pleasant and aromatic
2. Phloem fibres : Isolated bast fibres , strongly
lignified, slender , measures 250- 600 microns
in

42. • 3. Stone cells :
• Almost U shaped as one wall is thinner than the
other three, strongly lignified
• 4.Starch grains :
• Abundant starch grains which does not measure
more than 10 microns
• 5.Calcium oxalate crystals:
• Presence of small acicular raphides in the
parenchyma
• 6. Oil cells :
• Big and isolated

43. FENNEL
• Biological source :
• Drug consists of dried ripe fruits of Foeniculum
vulgare
• Family : Umbelliferae

44. Chemical constituents :
• Fennel contains volatile oil (1-4%), fixed oil (9-
12%)and proteins (20%)
• The chief constituents of volatile oil are a
phenolic ether anethole (50-60%) and ketone
fenchone (18-20%)
• Volatile oil also contains anisic aldehyde, alpha ,
ß – pinene, ascorbic acid, niacin etc

45. Uses:
• Carminative
• Stomachic
• Expectorant
• Flavouring agent
• Aromatic
• Stimulant
• Anthelmintic
• Useful in dental and mouth wash preparation
• Fennel water is useful in colic and flatulence in
children

46. Diagnostic characters :
• Mesocarp :
• Lignified and reticulate nature of the
parenchyma
• Endocarp :
• Cells showing parquetry arrangement
• Endosperm:
• Polyhedral, thick walled cells containing
aleurone grains, minute calcium oxalate crystals
and oil globules
• Vittae :
• Many in the form f yellowish brown fragments

47. CORIANDER
• Biological source :
• Drug consists of dried ripe fruits of Coriandrum
sativum
• Family : Umbelliferae

48. Chemical constituents :
• It contains volatile oil (1-4%), fixed oil (9-
12%)and proteins (20%)
• The chief constituents of volatile oil are
limonene, p- cymene, camphor, coriandrol etc
• Malic acid,
• Tannin,
• Vitamin A

49. USES :
• Carminative
• Stomachic
• Expectorant
• Flavouring agent
• Aromatic
• Stimulant
• Diuretic
• Anthelmintic
• Aphrodisiac

50. Diagnostic characters :
• Sclerenchymatous layer :
• Group of fusiform fibres of sclerenchyma
running way and at times crossing with each
other .
• Endocarp :
• Cells showing parquetry arrangement
• Endosperm:
• Polyhedral, thick walled cells containing
aleurone grains, minute calcium oxalate crystals
and oil globules
• Vittae :
• Many in the form f yellowish brown fragments

51. MENTHA
• Synonym: Peperimint
• Biological source: It consists of fresh
flowering tops or aerial parts of the plants
known as Mentha piperita
• Family : Labiatate

52. • Chemical constituents:
• The chief constituent of peppermint is
volatile oil (0.7-1.5%) and 6-12% of
Tannin.
• The chief constituent of volatile oil are
menthol (50-60%), menthyl acetate,
menthone ,cineole and small amounts of
terpenes

53. • Diagnostic characters :
• Covering trichomes : Thick, coarse,
uniseriate with many cells
• Glandular trichomes: Unicellular stalk and
a head with 1-8 cells (yellow colour)
• Stomata : Diacytic

54. • Epidermis:
• Cells with wavy walls
• Negative characters:
• Absence of calcium oxalate crystals in the
mesophyll tissue
• Uses: carminative, stimulant, spasmolytic
and antiseptic

55. QUESTIONS
• Define volatile oils and add a note on
various methods of extraction of volatile oils.
(10)
• Define and classify essential oils with
examples. Write the pharmacognosy of
Clove. (10)
• Explain in detail the method of manufacture

56. • Define and describe volatile oils by
physical and chemical properties. (10)
• Give the source, diagnostic characters,
active constituents and uses of Cinnamon
and Fennel. (10)

57. • Give the powdered microscopical
characters of Coriander and Clove. (5)
• Write a note on Supercritical fluid extraction
method (SCFE) and its significances. (5)
• Write a note on method of preparation and
analysis of Clove. (5)

58. • Differentiate microscopically the Fennel and
Coriander. (5)
• Give the source, active constituents and
uses of Eucalyptus and Sandal wood. (5)
• Define and classify with examples volatile oils.
(5)
• Enfleurage method of extraction of volatile
oils and its significances. (5)

59. • Write a note on general properties and
chemical nature of essential oils. (5)
• Give the source, active constituents and
uses of Mentha and Coriander. (5)
• Write the chemical structures for the
following (a) Eugenol (b) Menthol
• (c) Limonene (d) Cinnamic aldehyde. (5)

60. • Advantages of Supercritical fluid extraction.
(2)
• Diagnostic characters of Mentha piperita. (2)
• Write a note on Eculle method and its
applications. (2)
• Chemical tests for volatile oils. (2)
• Analysis of Eucalyptus oil. (2)