It is an introductry lecture to the 3rd year pharmacy students. It shows the importances, preparation and uses of essential oils.

1. Introduction to volatile oils
resins and terpenoids
Dr. MOSA E. O. AHMED

2. agenda
PRODUCTION AND USES
OF VOLATILE OILS
COMPOSITION OF
VOLATILE OILS
PREPARATION OF
VOLATILE OILS
EXTRACTION OF OILS
USED IN PERFUMERY
MODE OF ACTION OF
TERPENOIDS
SUMMARY

3. What is volatile oils?
• Volatile oils are generally mixtures of
hydrocarbons and oxygenated
compounds derived from these
hydrocarbons.
• Volatile (essential oils) are volatile in
steam.
• They differ in chemical and physical
properties from fixed oils.
• They are secreted in oil cells, in
secretion ducts or cavities or in
glandular hairs.
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4. What is volatile oils?
• EOs occur in plant as oil, except of
oils such as oil of bitter almonds,
which are produced by the
hydrolysis of glycosides.
• They are frequently associated
with other substances such as
gums and resins.
• EOs tend to resinify on exposure to
air.
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5. Production of
volatile oils
• Large quantities of volatile
oil are produced annually;
as examples, world
production of lemon oil,
eucalyptus oil, clove leaf
oil and peppermint oil
runs into several thousand
tons.
• India and china now
produce large quantities of
oil for export.

6. Uses of volatile oils
• Essential oils are for their:
1. Therapeutic action
2. Flavoring (e.g. Oil of
lemon)
3. Perfumery (e.g. oil of rose)
4. Starting material for
synthesis of other
compounds (e.g. oil
turpentine)

7. Therapeutic uses
of volatile oils
• For therapeutic purposes,
Eos are administered as:
1. Inhalation (e.g.
Eucalyptus oil)
2. Orally (e.g.
Peppermint oil)
3. Gargle and
mouthwash (e.g.
Thymol)
4. Transdermal (e.g.
Lavender, rosemary,
bergamot) in practice
of aromatherapy.

8. Therapeutic uses
of volatile oils
• For therapeutic purposes
they are administered as:
1. Antiseptic (e.g. clove
and thyme)
2. Carminative and
antispasmodic (e.g.
caraway, fennel,
chamomile, peppermint)
• Eos constituents have
antioxidant effects of
bacteria, hence used
as:
1. Food preservative
2. Cosmetic preparation

9. Composition of
volatile oils
• Volatile oils are generally
mixtures of hydrocarbons and
oxygenated compounds
derived from these
hydrocarbons, except oils
derived from glycosides (e.g.
bitter almond and mustard oil).
• In some oil the hydrocarbons
are abundant (e.g. turpentine
oil)
• In other oils (e.g. clove oil) the
bulk of oil consist of
oxygenated constituents.

10. Composition of
volatile oils
• The odour and taste of volatile
oils is mainly determined by
these oxygenated constituents.
• The oxygenated principles are
to some extent soluble water
but more soluble in alcohol.
• Originally many E oils are
terpenoid, smaller number are
benzene derivative mixed with
the terpene (e.g. cinnamon
and clove oils).
• A few compounds (e.g.
Thymol, carvacrol), although
aromatic in structure, are
terpenoid in origin.

11. Composition of volatile oils
• Evaluation:
Various pharmacopoeial procedures are given for the evaluation of
volatile oils.
1. Preliminary examination (Odour and taste)
2. Physical measurements (optical rotation, relative density and
refractive index).
3. Thin-layer chromatograms and capillary gas chromatographic
profiles are used to determine the proportions of individual
components of certain oils.
4. Advances in gas chromatography allow determination of chiral
components of volatile oils (e.g. carvone in caraway oil), thus
detecting adulteration.
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12. Composition of volatile oils
• Evaluation:
Various pharmacopoeial procedures are given for the evaluation of volatile
oils.
1. Ketone and aldehyde content oil are determined by reaction with
hydroxylamine hydrochloride (oxime formation) and titration of the
liberated acid.
2. Presence of fixed oil and resinified oil are detected by residue after
evaporation.
3. Presence of foreign esters is detected by conversion to a crystalline
deposit.
4. Presence of water is detected by turbidity of a carbon disulphide solution.
5. Volatile oil content of crude drugs is commonly determined by distillation
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13. • Biosynthesis:
• Terpenoids are originate form
mevalonic acid or deoxy xylulose
phosphate pathway.
• Only the (R)-form of mevalonic acid
gives rise to the terpenoids
• Monoterpenes arise at the geranyl
pyrophosphate (GPP) level of
terpenoid synthesis.
• There are three groups of
monoterpenoid structures: (1) acyclic;
(2) monocyclic; and (3) bicyclic.
• In the plant they are derived from
limonene.
• Relatively few enzymes, termed
cyclases, appear to determine the
skeletal class (e.g. menthanes,
pinanes, thujanes etc.).
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Composition of volatile oils

14. Composition of volatile oils
Name Botanical name Constituents
1. Terpenes or sesquiterpenes
Turpentine Pinus spp. Terpenes (pinenes, camphene)
2. Alcohol
Coriander
Sandalwood
Coriandrum sativum
Santalum album
Linalool (65–80% alcohols); terpenes
Santalol (sesquiterpene alcohols),
esters, aldehydes
3. Esters and alcohols
Bergamot
Lavender
---
Peppermint
-
Citrus bergamia
Lavandula officinalis
-
Mentha piperita
--
Linalyl acetate, linalool
Linalool; linalyl acetate (much); ethyl-
pentyl ketone.
Menthol (about 45%); menthyl acetate
(4–9%)
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15. Composition of volatile oils
Name Botanical name Constituents
4. Aldehydes
Cinnamon bark
Lemon grass
-
Cinnamomum verum
Cymbopogon spp.
-
Cinnamaic aldehyde (60–75%); eugenol; terpenes
Citral and citronellal (75–85%); terpenes
5. Ketones
Caraway
Dill
-
Carum carvi.
Anethum graveolens
-
Carvone (60%); limonene, etc
Carvone (50%); limonene, etc.
6. Phenols
Clove
-
Thyme
-
Syzygium aromaticum
-
Thymus vulgaris
--
Eugenol (85–90%); acetyl eugenol, methylpentyl
ketone, vanillin
Thymol (20–30%)
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16. Composition of volatile oils
Name Botanical name Constituents
7. Ethers
Eucalyptus
Nutmeg
-
Eucalyptus globulus
Myristica fragrans
-
Cineole (over 70%); terpenes, etc.
Myristicin (methoxysafrole) up to 4%; terpenes
(60–85%); alcohols, phenols
8. Peroxides
Chenopodium
-
Chenopodium
ambrosioides var.
anthelmintica
-
Ascaridole (60–77%), an unsaturated
terpene peroxide
9. Non-terpenoid and
derived from glycosides
Mustard
Bitter almond
-
-
Brassica spp.
Prunus communis var.
amara
--
-
Glucosinolates
-
Benzaldehyde and HCN (from amygdalin)
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17. • All the official volatile oils are
extracted by distillation.
• The distillation of volatile oils has
been practiced by means of water
or steam.
• The distillate, consists of a mixture
of oil and water, is condensed and
collected in a suitable receiver
(florentine flask).
• The distillate separated into two
layers, oil being separated form
water based on their density.
Preparation of volatile oils
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18. Preparation of
volatile oils
• Certain oils (e.g. Oil of cajuput,
oil of caraway, oil of turpentine
and oil of Australian sandalwood)
are rectified.
• Rectification usually takes the
form of a second distillation in
steam, which frees the oil from
resinous and other impurities.
• Light and atmospheric oxygen
have adverse effect on volatile
oils and official instruction for
storage of Eos should be
followed.

19. Extraction of oils used
in perfumery
• Certain oils (e.g. oil of rose)
used in perfume are prepared
by steam distillation but many
of flowers require other
treatment.
• These oils are extracted by:
1. Enfleurage
2. Pneumatic methods
3. Digestion in melted fats.
4. Means of solvents.

20. Extraction of oils used in perfumery
• Enfleurage method:
1. In this process glass plates are
covered with a thin layer of fixed oil or
fat upon which the fresh flowers are
spread.
2. The volatile oil gradually passes into
the fat and the exhausted flowers are
removed and replaced by a fresh
supply.
3. The volatile oil is obtained by three
successive extractions with alcohol.
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21. Extraction of oils used
in perfumery
• Pneumatic method:
1. Is similar in principles to the
Enfleurage process,
involves the passage of a
current of warm air through
the flowers.
2. The air loaded with
suspended volatile oil, is
then passed through a spray
of melted fat in which the
volatile oil is absorbed.
3. The volatile oil is obtained
by three successive
extractions with alcohol.

22. Extraction of oils used
in perfumery
• Digestion method:
1. In this process the flowers
are gently heated in
melted fat until
exhausted, then they are
strained out and the
perfume-containing fat is
allowed to cool.
2. The volatile oil is obtained
by three successive
extractions with alcohol.

23. Extraction of oils used
in perfumery
• Solvent extraction:
• It is based on the
Soxhlet principles
(studied in semester
5).

24. • Bio-membrane prevent leakage of fluids
from living organism to the surrounding
environment.
• If 2nd met. come into contact with a cell,
the lipophilic compounds will bind to the
lipophilic inner core of the membrane
bilayer. At high concentration these
compounds will change membrane
permeability.
• Bio-membrane is lysed or disrupted by
lipophilic 2nd met. (several mono- and
sesquiterpenes) and as consequence
necrotic death.
• By this mechanism essential oils shows
antimicrobial and cytotoxic activity.
Mode of action of terpenes
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25. Distribution of essential oils in plants
• EOs are widely distributed among the following families:
• Myrtaceae (e.g. eucalyptus)
• Lamiaceae (e.g. mint)
• Rutaceae (e.g. lemon)
• Umbelliferae (e.g. fennel)
• Lauraceae (e.g. cinnamon)
• Zingiberaceae (e.g. ginger)
• Asteraceae (e.g. chamomile)
• Many EOs have been extracted and studied extensively, such as those from:
• Ginger
• Cinnamon
• Lemon
• Clove
• Thyme
• Oregano
• Lavender
• Mint
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26. Resins
• Resins are complex mixtures of resin acids, resin alcohols
(resinols), resin phenols (resinotannols), esters and
chemically inert compounds known as resenes.
• Solubility:
• They soften and finally melt by heating.
• They are insoluble in water and petroleum spirit but dissolve
more or less completely in alcohol, chloroform and ether.
• Classification of resins:
1. Resins associated with volatile oils (oleoresins).
2. Resins associated with gums (gum-resins).
3. Resins associated with oil and gum (oleo-gum-resins).
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27. Resins
• Resins are often preformed in plants as normal physiological
products.
• The yield of resins is usually increased by injury (e.g. in the
case of Pinus).
• Many products (e.g. benzoin and balsam of Tolu) are not
formed by the plant until it has been injured (they are of
pathological origin).
• The gums which are associated with resins and volatile oils
usually resemble acacia gum in chemical nature and they
are often accompanied by oxidase enzymes.
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28. Resin: Resins usually contained in:
FENNEL BOOLDROOT ​ GUAIACUM INDIAN HEMP
Schizogenous duct Resin cells Elements of the heartwood External glands
MALE FERN LAC INSECT
. .
Internal gland Glands on the surface
. .
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29. Resins
• Balsams:
• Balsams are type of resin which contain a high proportion
of aromatic balsamic acids (benzoic and cinnamic acids)
• Examples for balsams: balsam of Peru, balsam of Tolu
and storax.
• Solubility:
• Balsams containing free acids (benzoic and cinnamic
acids) are partially soluble in hot water.
• Balsams containing aromatic esters and resins (e.g.
benzoin) are insoluble in hot water.
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30. Takeaway note
PINUS SPP CORIANDER ​BERGAMOT CINNAMON BARK
Terpene hydrocarbon Alcohol Ester Aldehyde
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31. Takeaway note
CARAWAY CLOVE ​FENNEL CHENOPODIUM
ketones phenol Ether peroxide
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32. summary
• Volatile oils are a mixture of hydrocarbons
and oxygenated compounds.
• China and India are the main producers of
essential oils.
• Various pharmacopoeial methods are given
to assess the quality of essential oils.
• Official volatile oils are extracted by steam
distillation.
• Several methods are used for extraction of
volatile oils for perfumes.
• The mode of action of Mono- and
sesquiterpenes, lipophilic, base on affecting
the bio-membrane permeability and as
consequence result in necrotic cell death.
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33. REFERENCES
1. Trease and Evans 2009. In the pharmacopoeial and related drug of biological
origin. Text book of pharmacognosy (pp. 263-267). USA or UK: Saunders
Elsevier
2. Mode of action of Eos:
Wink. 2015 Modes of Action of Herbal Medicines and Plant Secondary Metabolites.
Medicines , 2(3), 251-286; https://doi.org/10.3390/medicines2030251
3. Distribution of Eos in plants:
Zhi-Jing Ni, Xin Wang, Yi Shen, Kiran Thakur, Jinzhi Han, Jian-Guo Zhang, Fei Hu, Zhao-Jun
Wei, Recent updates on the chemistry, bioactivities, mode of action, and industrial applications
of plant essential oils, Trends in Food Science & Technology, Volume 110, 2021, Pages 78-
89,ISSN 0924-2244, https://doi.org/10.1016/j.tifs.2021.01.070
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34. thank you
MOSA AHMED
Mosa.elhady@neelain.edu.sd