Phytochemistry essential oils intro

PhytochemistryPhytochemistry
Volatile oilsVolatile oils
IntroductionIntroduction
By
Dr. Mostafa Mahmoud Hegazy ( PH.D.)
Pharmacognosy Dept.

IntroductionIntroduction
1- Definition
2- Occurrence
3- Importance
4- Preparation
5- Quality control

DefinitionsDefinitions
“volatile oils”, “Ethereal oils” or Essential oils”
Volatile oils: Complex liquid mixtures of odoriferous compounds of varying chemical
composition, which easily evaporate when exposed to air at room temperature, and
which are used for either their specific therapeutic activity or their aroma.
Aromatherapy is a branch of complementary medicine, which depends on the use
of aromatic plants, their extracts, mainly their essential oils to promote health, beauty
and vitality.
Volatile Oil Fixed Oil
Volatile at room temperature ….
(distillable)
Non volatile at R.T. (grease on filter paper)
… (non distillable)
Mixture of oxygenated and non-oxygenated
terpene hydrocarbons
Mixture of fatty acid esters (Soap
formation)
Resinify in light and air Rancidify in light and air
secondary metabolite primary metabolite

OccurrenceOccurrence
I- Mostly in plants in specific structures
Glandular hairs e.g. Labiatae
Oil cells e.g. Lauraceae
Oil ducts or vittae e.g. Umbelliferae
oil glands (cavities) e.g.Rutaceae
ImportanceImportance
I- Physiological Significance
1- Detoxification products.
2- Solvents for wound healing resins
3- Attractants: insects attraction aiding in
cross pollination of the flowers.
4- Protectants: as defensive agent for
repelling of insects and herbivorous.
II- Animal sources:
e.g. musk
Ambergris
Physiological Significance
Attractants
Protectants
II- Uses :
1- Therapeutic uses: local stimulants, local analgesic, anthelmintic, diuretic,
Carminatives, Mild antiseptics, Local irritants and Anthelmintic.
2- Perfumery.
3- Spices and condiments.
4- Flavoring agents: for food, pharmaceuticals, cosmetics, and tobacco.

PREPARATION OF VOLATILE OILS
The following methods are commonly used for preparation of volatile oils:
Expression method Extraction method Enzymatic hydrolysisDistillation method
Water Distillation
Water and Steam
Distillation
Direct Steam
Distillation
Extraction with Volatile
Solvents
Extraction with Non-Volatile
Solvents
The Enfleurage Method
The Pneumatic Method
The Maceration Method
Sponge Method
Scarification Process
Expression of Rasping Process
Machine Processes
The method depends on:
1- The condition of the plant material i.e. intact, crushed or powdered.
2- The location of the oil in the plant (superficial or deep).
3- The amount of the oil.
4- The nature of the constituents.
Principle of Distillation Methods
• The boiling point of most volatile oil constituents range between 150o
C-300o
C.
• Distillation at such high temperatures may cause either decomposition or polymerisation.
• The presence of water during distillation allows the process to be carried out at a
temperature below 100o
C.
• This is explained by Dalton’s law of partial pressure which states that:
“When two immiscible liquids are heated together, they will boil at a temperature below
the boiling point of either one”

Distillation apparatusDistillation apparatus
1- The body of the still (distillation flask on laboratory scale) : usually made of copper lined
with stainless steel. The use of Fe is to be avoided as any Fe+++
ions may catalyze hydrolytic
and oxidative degradation of the oil constituents.
2- The condensing system (condenser).
3- The receiver (collecting flask) (e.g. Florentine receivers).
Cohobation is the return of the aromatic water (water saturated with volatile oil) to the body
of the still to be redistilled in order to improve the yield of oil.
Rectification of hydrodistilled oils (Purification):
Removal of bad smelling, irritating and / or colored impurities is carried by Redistillation.
Removal of water and moisture is done by filtration over anhydrous sodium sulfate.

Water Distillation Water and Steam Distillation Direct Water Distillation
process material is boiled with
water in the distilling
chamber until the
volatile matter is
condensed.
steam is passed through the
macerated mixture. Since the
oil might be impaired by
direct boiling, the steam is
generated elsewhere and is
piped into the mixture.
Steam is forced through the
fresh material carrying.
(contain considerable
amount of moisture, no
maceration).
Plant Material 1- Dried e.g. powders
of Barks and wood
2- Petals which may
lump with steam.
Dried and fresh especially
herbs and leaves that their
volatile oils may be affected by
boiling.
Fresh materials containing
sufficient moisture
leaf, stem and flowers
Mode of charging Material completely
covered with H2O
H2O is present in the still but
steam alone is in contact with
the plant.
N. B.: Dried material should be
wet.
H2O is completely absent.
Steam is forced through the
material which is placed on
perforated trays.
Hydrodiffusion Better when material
moves freely in H2O
Better when charging is even Better when charging is
even
Steam Pressure About atmospheric About atmospheric Can be modified according
to plant condition and
nature of oil
Temperature About 100 o
C About 100 o
C Can be modified according
to plant condition and
nature of oil

Water Distillation Water and Steam Distillation Direct Water Distillation
Rate of
Distillation
Low Good High
Yield of Oil Relatively Low, since:
1-Esters may be
hydrolyzed.
2-Water soluble and high
boiling point constituents
remain in the still.
Better since hydrolysis is
diminished
The best if no lumping or
chanelling
Commercial
preparations
1- Oils of terpentin stable
oil
2-Oil of rose
*Oils of Cloves and
Cinnamon
*Oil of Citronella
* Oils of Pippermint
Advantages 1-Low priced and portable
still.
2-Could be carried near
production area.
Hydrolysis is prevented since
no excessive wetting of
material.
1-Stills are more durable
and suitable for large
scale production.
2-Suitable for oils rich in
esters and high boiling
point constituents.
Disadvantages 1- Burning of plant.
2- Cohobation must be
carried.
3- Not used for oils rich in
saponifiable, water soluble
or high boiling point
constituents.
Hydrodiffusion could be
hindered by fine
comminution, uneven
charging or excessive wetting
resulting in low yield.
1-Powders could not be
used since easy
chanelling.
2-Superheated steam is
not used since it results
in plant drying therefore
wet steam is prefered

Scarification and Expression MethodsScarification and Expression Methods
Principle
Mechanical procedures, carried at room temperature and based on puncturing
and or squeezing of the plant material to liberate the oil.
The classical process includes:
1- Squeezing of the peel (zest) under a stream of water yielding an emulsion
formed of essential oil, water, pectin, cellulose, pigments and traces of waxes.
2- Removal of water, pectin and cellulose by centrifugation.
3- Removal of waxes by strong cooling (chilling) followed by filtration or
decantation.
Applications:
This method is used for the preparation of oil of lemon, oil of orange, and oil of
bergamot which present in large amounts in outer peels of fruits e.g. epicarps.
The two principal methods of scarification are:
1- The “Sponge Method"
2- Ecuelle-à-piquer Method (Scarification).
3- Expression of rasping
4- Machine processes

Sponge Method
1- Fruits (e.g. Citrus fruits) are washed, cut into halves and peels collected.
2) Pericarp are soaked in water, turned inside out “squeezed”, by means of sponge
3) The saturated sponge with exuded aqueous and oily mixture is squeezed in a vessel and
the emulsion obtained centrifuged and cooled and then the upper oily layer is separated.
Ecuelle-à-piquer method (Scarification):
It is based on puncturing (Scarifying) the surface of
whole fruits and thus allowing exudation of the oil from the outer colored zone of their
peels. This is formed in funnel made of copper and tinned inside. The upper part bears on its
inside surface numerous strong long metal pins, which penetrate the epidermis. The oil is
then collected and leaves to separate from water.
Expression of rasping: the outer layer of the peel with a grater, collecting the rasping in
special bags (horsehair bags) followed by strong pressing.
Machine processes: whole fruits are charged into machines in which the peels are
removed, sprayed with water, squeezed or pressed and the oil collected through wool filters.

Extraction MethodsExtraction Methods
Applications:
For delicate flowers e.g. Jasmine which contain either:
1- Small amounts of oils. 2- Oils which decompose by the action of heat (stem).
I- Extraction by Volatile Solvent
e.g. Petroleum ether, n-hexane, Benzene.
The solvent should be:
1- Dissolves the oil with the least amount of
impurities.
2- Dose not react with any of the oil constituents.
3- Has a low boiling point.
4- Leaves no residue on evaporation.
II- Extraction by Non-Volatile Solvent
This processes are used for
preparation of natural flower oils
producing perfumes.
Solvent used are:
1- Fats e.g. Lard and tallow.
2- Fixed oils e.g. Olive oil.
Extraction by Volatile Solvent of low boiling
points e.g. benzene, or hexane in a continuous
extraction apparatus “Soxhlet”. The volatile oil
solution obtained is then evaporated under
reduced pressure, where the volatile solvent will
evaporate, leaving the volatile oil behind.
the following procedures are used:
1- The Enfleurage Method
2- The Pneumatic Method
3- The Maceration Method

Enfleurage Process
Flower Petals
Add fat mixture
[Lard & tallow (2 : 1)]
1) Enfleurage Product
[Fat saturated with oil]
* Add absolute alcohol
* Successive extraction
* Cooling to remove most of fat
2) Triple extract
[alc. solution of vol. oil + pigments + traces of fats]
Evaporation of alcohol
or fractional distillation
Dilution with
H2O + NaCl
3) Absolute of Enfleurage
[Semi-solid, alcohol-free product]
4) Volatile oil

The Pneumatic Method:
• This method is similar in principle to the Enfleurage Method , and involves the
passage of a current of warm air through the flowers.
• The air laden with suspended volatile oil is then passed through a spray of
melted fat in which the volatile oil is absorbed.
The Maceration Method:
• The flowers are gently heated and rotated with melted fat “lard or fixed oil” until
complete exhaustion. They are then stained out, squeezed and the process is
repeated until a special concentration is reached.
• The oil-containing fat is allowed to cool and the oil can be obtained from the
mixture by successive extraction with alcohol.
Super critical fluid extraction [Extraction by supercritical gases]
The oil components are not subjected to hydrolysis or deterioration.

Methods of Preparation of Volatile oilsMethods of Preparation of Volatile oils
Process Applications Advantages Disadvantages
Distillation Suitable for dried and
fresh plant material rich
in volatile oils with
constituents mostly
unaffected by heat.
Cheapest commercial
technique (as regards
apparatus, solvents
and source of heat).
The use of high
temperature and water
may affect
constituents.
Scarification
and Expression
Suitable for preparation
of oils present in large
amounts in outer peels of
fruits and rich in heat-
sensitive constituents.
1)Carried at room
temperature heat
sensitive oils.
2)Yields oils with
more natural
odors.
High cost due to need
of high number of
workers.
Extraction Usually for fresh
materials with heat-
sensitive oils present in
small amounts.
1)Carried at room
temperature.
2)Yields oils with
more natural
odors.
High cost due to use
of solvents and or/
great number of
workers.

Plant name

Non-volatile
Glycoside

Volatile aglycone

Other hydrolytic
products

Hydrolytic enzyme

Gaultheria
procumbens
(Ericaceae)&

Gaultherin

& / or
Monotropin

Methyl salicylate

Methyl salicylate
Primeverose
(Xylose+glucose)

Glucose
Gaultherase

Gaultherase
Geum urbanum
(Rosaceae)
Gein Eugenol Glucose β-Glucosidase
Brassica nigra
(Brassicaceae)
Sinigrin Allyl isothiocyanate Glucose +Potassium
acid sulfate
Myrosin
Vanilla planifolia
(Orchidaceae)
Glucovanillin Vanillin Glucose β-Glucosidase
Amygdala amara
(Rosaceae)
Amygdalin Benzaldelhyde Gentiobiose (2
glucose units) +HCN
Emulsin
Preparation of Volatile Oil AfterEnzymatic HydrolysisPreparation of Volatile Oil AfterEnzymatic Hydrolysis
• Occasionally the volatile oil is found in the plant in a glycosidal form.
• The odoriferous substance is set free only by hydrolysis of certain odorless glycosides
present in the plant.
• The following are examples of such oils:

Quality control
Quality control of drugs containing essential oils
1- Morphological and microscopic examinations in order to determine the genuinety and detect
adulteration of the plant material. Microscopically, the presence of volatile oils could be detected by
using lipophilic dyes (Sudan III).
2- Determination of the percentage of the essential oil (Quantitation).
3- Preliminary analysis of the oil by HPTLC (Finger-print chromatogram)
Quality control of essential oils
A- Label of commercial products of essential oils and concretes should specifically include the
following: the source organ, the geographical origin, and the Latin binomial name of the plant
in order to avoid any confusion.
It should be noticed that the common name of the plant is not sufficient to precisely identify the
oil in most cases, e.g. oregano oils are obtained from different species according to localities; thus
Greek oregano (Origanum vulgare), Turkish oregano from Origanum onites, Spanish oregano
from Corydothymus capitatus and Mexican oregano from Lippia graveolens.
B- In addition, Pharmacopoeias require different tests including:
1- Evaluation of the miscibility with alcohol.
2- Measurement of physical constants such as refractive index, optical rotation, relative density
(specific gravity) and solidification temperature.
3- Determination of various indices such as the acid, ester, carbonyl and iodine values.
4- Chromatographic analysis.

Determination of the Percentage of a volatile oils in a plant materials
(Quantitation, Clevenger’s apparatus)
Description It consists of a round bottom Pyrex distillation flask attached to a special
graduated trap designed for collection of oils lighter or heavier than water.
Procedure:
1- Introduce a known weight of the entire or powdered  drug with 3-6 times of water or water
+ glycerin why…? in the distillation flask.
2- Allow the process to be carried over a period of 5-6 hours. till ?
3- The distillate, received in the graduated trap, is allowed to cool till  a constant volume of
oil could be recorded.
4- The percentage v/w is calculated (on dry weight) from the following formula:
% v/w   (i.e. mL of oil / 100 gm dry plant material) =  (V  x 100)/ W
Where  V  =  volume of oil   W  =  weight of plant material
If the apparatus available to be used for oils heavier than water, Xylene should be added…?
in the measuring side tube and % of oil calculated as follows:
                                                           %  v/w    =  (V2  -  V1)  x 100
            W

Pharmacopoeial requirements for essential oils

1- Miscibility with alcohol
Most volatile oils are completely miscible with absolute alcohol.
1- The higher the miscibility with alcohol of low concentrations the higher the % of
oxygenated constituents.
2- The miscibility with alcohol of low concentration is decreased on adulteration with non-
polar solvents such as petroleum ether (turbidity).
2- Physical Examination
For evaluation of the sample or detection of adulterants.

I- Odor
The detection of any abnormal odor by smelling 1 or 2 drops of the oil applied on a filter
paper indicates either adulteration or deterioration during storage (e.g. orange oil acquires a
caraway odor on bad storage since limonene is autoxidized to carvone and carveol)
II- Solubility
The solubility in non-polar solvents such as benzene, carbon disulfide
and light petroleum is tested. Any turbidity indicates the presence of moisture.

III- Relative density (specific gravity)
The apparatus used for determination is a pycnometer.
The specific gravity of a volatile oil may give an indication on its composition e.g.
Oils with specific gravity < 0.9 are usually rich in hydrocarbons.
Oils with specific gravity > 1.0 are mostly rich in aromatic compounds.

IV-IV- Optical rotation Optical rotation
Determination of optical rotation is carried out by using a polarimeter and is helpful in
detection of adulteration and identification of the variety of the sample.

1- For oils
a- French oil of turpentine is levorotatory [l (-)] since l- pinene is present in the oil in high
concentration.
b- American oil of turpentine is dextroratory [d (+)] because d- pinene is its major
constituent.
2- For oil isolate: The optical rotation gives also an indication on the method of preparation
of the volatile :
I- All synthetic compounds are racemic (dl).
II- Natural compounds are generally optically active. They may occur in (l) or (d) forms.
-Example: natural camphor is (l) or (d) while synthetic camphor is (dl).
4- Chromatographic analysis4- Chromatographic analysis: :
TLC is used routinely for quality control purposes. GLC is the most suitable method due to
the volatility of the constituents. It can be used for qualitative and quantitative purposes.

"The chromatographic profile is a list of constituents selected among those that are
representative and characteristic of an essential oil."

Removal of terpenoid hydrocarbonsRemoval of terpenoid hydrocarbons
(Terpeneless oils of dill, lemone and orange)(Terpeneless oils of dill, lemone and orange)

Oils rich in terpenoid hydrocarbons are liable to rapid deterioration on storage through oxidation
and polymerization to yield bad smelling (generally with turpentine-like odor) and resinified
products.
The process of elimination of terpenoid hydrocarbons could be considered as a specific
procedure for rectification. Thus a considerable amount of the terpenoid hydrocarbons could be
removed by any of the following methods to produce "terpeneless-oils":
1- Fractional distillation under reduced pressure; hydrocarbons have lower boiling points than
oxygenated compounds and therefore, distill first and are discarded.
2- Column chromatography on silica gel, by eluting hydrocarbons with n-hexane then oxygenated
compounds with absolute alcohol.
3- Selective extraction of the oxygenated components with dilute alcohol followed by distillation.
Terpeneless oils are more expensive than natural oils, and
are characterized by being:
1- Richer in oxygenated compounds.
2- More soluble in low-strength alcohols.
3- Employed in smaller quantities to give the same strength of odor.
4- More stable being less liable to deterioration

Physical Characters of Volatile Oils
1- Strongly refractive liquids.        2- Many of them are optically active.
3- Readily volatile in steam or at ordinary temperatures.
4- They are characterized by a pleasant smell.        5- Insoluble in water.
Storage of Volatile Oils
• Deterioration of volatile oils during storage is attributed to changes in their constituents.
• Reactions such as oxidation, polymerization, hydrolysis and interaction of functional
groups should be avoided.
• They are enhanced by evaluation of temperature, oxygen, moisture, light and traces of
metals.
Precautions before and during storage
1- Oils should be free from metallic impurities ( iron containers ).
2- Oils are dried over anhydrous Sodium sulphate to get rid of any traces of moisture.
3- Containers used for storage should be dark colored and tightly closed sometimes under
CO2 or N2 (inert gases).
4- The oils are kept away from light and at low temperature.

Chemistry of Volatile OilsChemistry of Volatile Oils
• volatile oils are complex mixture of hydrocarbon and related oxygenated compounds.
• The hydrocarbons mentioned here are collectively known as “terpenes”. The formula
“C10H16” is called now true terpenes.
• In practice the term “terpene” is applied to all the C10 isoprenoid compounds, including
those containing oxygen. They were collectively called "terpenes", however, the suffix –oid
is more logical, the –ene suffix should be restricted to the unsaturated hydrocarbons of the
class.
Determination the Structure of Terpenes and the Isoprene Rule:
• The molecule structure of terpenes, are built theoretically from “isoprene” unit.
• Each molecule is made up of the union of two or more isoprene units.
• These units are usually united in a “head to tail manner”.
• They yield isoprene as final product of destructive distillation (i.e. pyrolysis).
CH3 CH3
OPP
Isoprene Unit (C5) "Active Isoprene"
Isopentyldiphosphate
1
2
3
4
1
2
3
4
5 5
Head
Tail
Myrcene

isopentenyl PP
(IPP) (C5)
Mevalonic acid Deoxyxylulose
phosphate
OPP
dimethylallyl PP
(DMAPP) (C5)
OPP
Monoterpenes (C10)
Iridoids
C10
IPP
C15
Sesquiterpenes (C15)
C20 Diterpenes (C20)
C25 Sesterterpenes (C25)
X 2
Triterpenoids (C30)C30
Steroids (C18-C30)
C40 Tetraterpenes (C40)
Carotenoids
Hemiterpenes (C5)
X 2
IPP
IPP
pathways leading to terpenoids
The union of two or more of isoprene units gives different
classes of compounds

CLASSIFICATION OF CONSTITUENTS
OF VOLATILE OILS
(1) Terpene Hydrocarbons
(A) Terpene Alcohols
(B) Terpene Phenols & Ethers.
(C) Terpene Aldehydes.
(E) Esters.
(F) Terpene Ox ides.
(G) Terpene Perox ides.
(3) Sulfur-containing compounds.
(4) Nitrogen-containing compounds.
(2) Oxygenated Terpene Compounds (D) Terpene Ketones

For more educational lectures
cognosy4all.blogspot.com

cognosy4all.blogspot.com
Pharmacognosy and Herbal Medicine Dr. Mostafa

Phytochemistry essential oils intro

More Related Content

What's hot (20)

Similar to Phytochemistry essential oils intro (20)

More from Mostafa Mahmoud Hegazy (20)

Recently uploaded (20)

Phytochemistry essential oils intro