volatile oils - eopcw.com
TRANSCRIPT
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Volatile Oils
By Yenesew Wudu
March, 2020
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Outline
Definition and classification
Chemical composition
Uses
Extraction methods
Examples of drug containing volatile oils
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Learning objectives
After completing this unit you will be able to:
Define and classify volatile oils
Summarize biosynthesis and constituents of volatile oils
Discuss volatile oils extraction methods
Describe crude drug containing volatile oils
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Definition
Volatile oils are:
odorous volatile principles of plant and animal source,
evaporate when exposed to air at ordinary temperature
the concentrated extracts of volatile, non-water-soluble aroma
compounds from plants.
are also called essential oil or ethereal oil
In most instances volatile oil preexists in the plant contained in
special secretory tissues, oil ducts, oil cells, or oil glands .
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Cont...
In few cases they didn't preexist, but formed by the
decomposition of a glycoside.
For example, whole black mustard seeds are odourless,
crushing the seeds and adding water to it gives a strong
odour
due to formation of allyl isothiocyanate by
decomposition of Sinigrin by an enzyme myrosin.
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Properties
Soluble in alcohol and other organic solvents
Practically insoluble in water
Lighter than water (clove oil is heavier)
Possess characteristic odour
Have high refractive index
Most of them are optically active
Can dissolve fixed oils, fats, resins, camphor, and free
alkaloids.
Are highly sensitive to heat, moisture, and oxygen.6
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Cont...
Colourless liquids, but when exposed to air and direct
sunlight these become darker due to oxidation.
Differ from fixed oil in various ways:
can be distilled from their natural source
are not glyceryl esters of fatty acids
don’t leave permanent grease spot on paper
not saponified with alkalis.
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Essential oils Fixed oils
Secondary metabolites Primary metabolite
Mixture of terpenes, sesquiterpenes, & their oxygenated derivatives
Mixture of fatty acids
Can evaporate at room temperature Can’t evaporate at room temperature
Obtained from leaves, roots, in petals, & bark.
Obtained from seed of plant & animal
Possess high refractive index Possess low refractive index
These are optically active. These are optically inactive.
No permanent stain left after evaporation Permanent stain left after evaporation
They are unable to undergo saponification Can be easily saponified.
do not rancid, rather they oxidize & lose their therapeutic benefit
Can go rancid (stale) over time
Colorless Some possess colors (yellowish)
Have characteristic odor May or may not possess odor
Low boiling point High boiling point
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Properties …
Constituents
Hydrocarbons: exclusively made from terpenes(mono-,
sesqui-, & diterpenes)
Oxygenated compounds (esters, alcohols, aldehydes, ketones,
phenoles, and oxides
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Classification Volatile oils are classified on the basis of functional groups present
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Terpenoids
Terpenoids are plant origin hydrocarbons of the general formula (C5H8)n as
well as their oxygenated, hydrogenated, and dehydrogenated derivatives.
Terpinoids are responsible for the fragrance of plants and flowers.
Isoprene rule states that the terpenoid molecules are constructed from two
or more isoprene units joined in a ‘head to tail’ fashion.
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Terpenoids....
However; carotenoids are joined tail to tail and carbon atom is not
a multiple of five.
Classification of Terpenoids
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S. No
No of carbon atoms
Value of n
Class
1 10 2 Monoterpenes (C10H16)
2 15 3 Sesquiterpenoinds (C15H24)
3 20 4 Triterpenoids (C20H32)
4 25 5 Sesterpenoids (C25H40)
5 30 6 Triterpenoids (C30H48)
6 40 8 Tetraterpenoids (C40H64)
7 >40 >8 Polyterpenoids (C5H8)n
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Chemical Composition
Many of them are terpenoid in origin
A smaller number such as those of cinnamon and clove
contain principally aromatic
A few compounds (e.g. thymol, carvacrol), although
aromatic in structure, are terpenoid in origin
Very few are glycosides (bitter almond oil and mustard oil)
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Storage of volatile oils
Volatile oils are liable to oxidation on storage in presence of air, moisture,
and light.
Oxidation is followed by the change in colour, odour, and increase in
viscosity.
Hence, they must be stored
in well-closed and well filled containers away from light in cool places
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Pharmaceutical applications
In pharmaceutical, foods, beverages, and cosmetic industries
flavouring agent, perfuming agent
For therapeutic purposes
Carminative (e.g. Umbilliferous fruits)
Anthelminitic (e.g. Chenopodium oil)
Diuretics (e.g. Juniper)
Antiseptic (e.g. Eucalyptus)
Counter irritant (e.g. Oil of winter green)
Local anesthetic (e.g. Clove)
Sedative (e.g. Jatamansi)
Local irritant (e.g. Turpentine)
Insect repellent (e.g. Citronella)
Source of vitamin A (e.g. Lemongrass)
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Extraction methods
Distillation
Due to the influence of hot water and steam, the essential
oil is freed from the oil glands in the plant tissue
The vapour mixture of water and oil is condensed
From the condenser, distillate flows into a separator, where oil
separates automatically from the distillate water.
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Extraction…
Three type of distillation
Water distillation (hydrodistillation)
Water and steam distillation
Steam distillation
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Extraction…
Water (hydro) distillation
the material is completely immersed in water, which is
boiled by applying direct heat.
there is direct contact between boiling water and plant
material.
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19 Hydro-distillation set-up
Condenser
Clevenger-apparatus
Round-bottom flask
Heating mantle
Rubber tube
Clamp
Iron stand
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Extraction…
Advantages
inexpensive,
easy to construct
suitable for field operation
Disadvantages
complete extraction is not possible
Hydrolysis
polymerization
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Extraction…
Water and steam distillation
The equipment used is generally similar to that used in
water distillation,
but the plant material is supported above the boiling water on a
perforated grid.
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Extraction… Steam distillation
plant material with steam generated outside the still in a
satellite.
the plant material is supported on a perforated grid above
the steam inlet
It is the most widely accepted process for the production of
essential oils on large scale.
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Extraction…
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Extraction…
Advantages
Amount of steam can be readily controlled
No thermal decomposition of oil constituents.
Most widely accepted process for large-scale oil
production, superior to the other two processes.
Disadvantage
Much higher capital expenditure needed
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Extraction…
Expression method
refers to any physical process in which the essential oil
glands in the peel are crushed or broken to release the oil
Used for extraction of thermolabile VO’s such as lemon
peel oil.
yields a product of superior quality (natural odour)
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Extraction…Enfleurage method
Also called cold fat extraction
glass plates are covered with a thin layer of fixed oil or
fat up on which the fresh flowers are spread.
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Extraction…Modern Methods Very expensive, so
used in certain casecostly essential oils in a natural state without any
alteration of their
thermo sensitive components or
the extraction of essential oils for micro-analysis
examples
Solid phase micro-extraction (SPME)
Supercritical fluid extraction (SFE)
Microwave distillation
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Examples of VO Containing Drugs
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Camphor oil
Obtained from the wood of Cinnamomunt
camphor (Lauraceae),
A tree widely grown in Taiwan, Japan and
south China:
Constituent
camphor, cineol, pinene, and diterpenes
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Camphor…
Uses:
Externally as a rubefacient
Internally as a mild antiseptic and carminative
It finds many non-pharmaceutical uses.
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Eucalyptus oil
distilled from the fresh leaves of various species of
Eucalyptus (Myrtaceae)
Constituent
cineole (Eucalyptol) (major)
pinene,
camphene
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Eucalyptus oil…Use
For Alleviating The Symptoms Of Nasopharyngeal
Infections,
For Treating Coughs And As A Decongestant.
Solution Of Eucalyptus Oil Is Used As Nasal Drops.
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Peppermint oil
Volatile oil obtained by steam
distillation from the fresh flower
tops of menthe piperita (lamiaceae)
and other species of mentha
Constituent
contains chiefly menthol
Other important constituents
menthone, menthofuran, Jasmone
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Peppermint oil…
Uses
Carminative, stimulant, counter irritant and flavoring agent.
It has mild anti- septic properties.
It is also used in to the paste, and tooth powders, shaving
creams, tobacco
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Clove oil ‘kirunfud’
From dried flowering buds of Eugenia caryophllus (Myrtaceae).
It contains not less than 15% V/W of clove oil
Constituent
eugenol (70-90%),
eugenol acetate,
carrophyllens
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Clove oil…Uses:
dental analgesic, stimulant, aromatic, flavoring agent
and anti- septic
The sesquiterpenes of clove have been cited as potential
anti- carcinogenic compounds.
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Garlic oil Obtained from the bulb of Allium sativum (Liliaceae).
ConstituentsAllicin
the most important of the biologically active components in the
crushed bulb.
produced when the precursor alliin is cleaved by the action of the
enzyme alliinase upon crushing the tissue.
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Garlic …Uses:
as antimicrobial activity,
effects on lipid metabolism,
antithrombotic agent through inhibition of platelet
aggregation.
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Lavender oil It is the volatile oil obtained by steam distillation of fresh
flowering tops of Lavandula officinalis (Lamiaceae).
Constituent
30-40% Esters calculated as linalyl acetate
linalool, pinene, geraniol, and cineol to some extent.
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Lavender oil ...
Uses
Hypnotic in aromatherapy
For treatment of flatulent dyspepsia and topically for
rheumatic pain.
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Corainder oil “dimblal”
From the dried, ripe fruits of Coraindrum satvum
(Umbelliferae).
Constituent
65-70% of (+)-linalool
flavonoids, coumarins, isocoumarins and phenolic acids.
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Coriander oil…Use
Pharmaceutically coriander and its oils are used as a
flavoring agent and carminative.
The oil is used along with purgatives to prevent intestinal
gripping
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Cardamom
From dried ripe seeds of Elettaria cardemomum
(Zingiberaceae).
Constituent
oil contains a high proportion of terpinyl acetate and
cineole
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Cardamom…
Use
Cardamom is aromatic, stimulant, carminative, diuretics
used as flavoring agent
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Cinnamon oil “Kerefa”
From the dried bark of the shoots of Cinnamomun
zeylanicum (Lauracea).
Constituent
contains about 60-75% w/w of cinnamic aldehyde
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Cinnamon oil …
Use
as a flavouring agent and mild astringent
The oil has carminative properties
A powerful germicide
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Thyme oil “Tosign”
Thyme oil is produced from the fresh aerial part by seam
distillation from Thymus vulgaris and other spices of
Thyme (Lamiaceae).
Constituent
Thymol is the principal (30-35%)
Others such as carvacrol 1-4%, cymene 15-28%, terpinene 5-
10%
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Thyme oil …
Use
used as antiseptic, antitussive and expectorant.
spasmolytic effect is also reported
which may be due to the flavonoids of the leaves
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