Volatile oils Pharmacognosy I - PowerPoint Presentation

Slide1

Volatile oils

Pharmacognosy I

Mosul University

/ college

of Pharmacy

L.A.

Dilbreen

BarzanjiSlide2

‘

Volatile

’

or ‘

essential’

oils

are the odorous and volatile products of various plant and animal species.

They have a tendency to undergo evaporation on being exposed to air even at an ambient temperature.

They

differ entirely in both chemical and physical properties from fixed oils.

They are secreted in oil cells, in secretion ducts or cavities or in glandular hairs.

They frequently associated with other substances such as gums and resins and themselves tend to

resinify

on exposure to air

.

Large quantities of volatile oils are produced annually; as examples, for lemon oil, eucalyptus oil, clove leaf oil and peppermint oil world production annually runs into several thousand metric tons each

.Slide3

Uses of volatile oils:

Volatile

oils are used for their

therapeutic

action

:

for

flavouring agent (e.g. oil of

lemon)

in

perfumery (e.g. oil of rose

)

starting

materials for the synthesis of other compounds (e.g. oil of turpentine) Slide4

For therapeutic purposes

they are administered as:

Inhalations (e.g. eucalyptus oil)

Orally (e.g. peppermint oil)

Gargles and mouthwashes (e.g.

thymol

)

Transdermaly

(many essential oils including those of lavender, rosemary and bergamot are employed in practice of aromatherapy).

Oils with a high phenol content, e.g. clove and thyme, have antiseptic properties

carminatives

antispasmodicsSlide5

Composition of volatile

oils

with the exception of oils derived from

glycosides

(e.g. bitter almond oil and mustard oil) volatile oils are

generally mixtures of hydrocarbons and oxygenated constituents are present

; in others (e.g. oil of gloves) the bulk of the oil consists of

oxygenated compounds

.

The odour and taste of volatile oils is mainly determined by these oxygenated constituents, which are to some extent soluble in water (note orange-flower water, rose water, etc.) but more soluble in alcohol (note tincture or essence of lemon, etc

.).

Many oils are

terpenoid

in origin; a smaller

number

such as those of cinnamon and clove contain principally aromatic (

benzene

) derivatives mixed with the terpenes. A few compounds (e.g.

thymol

and

carvacrol

),

although aromatic in structure, are terpenoid in origin

.Slide6
Slide7

Note box 1:

terpenoids

Terpenoids

are compounds derived from combination of two or more

isoprene

units, isoprene is a five carbon unit, chemically known as 2-methyl-1,3-butadiene.

According to

isoprene rule

proposed by Leopold

Ruzicka

, terpenoids arise from head-to-tail joining of isoprene units. Carbon 1 is called the ‘head’ and carbon 4 is the ‘tail’.

Terpenoids are classified into:

monoterpenes

,

sesquiterpenes

,

diterpenes

,

triterpenes

,

tetraterpenes

and polymeric terpenoids. Slide8
Slide9

Note box 2:

monoterpenes

Monoterpenes

, 10-carbon containing terpenoids, are composed of 2 isoprene units, and found abundantly in plants, e.g. (+)-limonene from lemon oil, and (-)-linalool from rose oil.

Many

monoterpenes

are the constituents of plant volatile oils or essential oils.

Monoterpenes

occur in plants in various structural forms; some are cyclic while others are acyclic.

They also contain various types of functional group, and depending on their functional group they can be classified as simple hydrocarbons, alcohols, ketones,

aldehydes

, acids or phenols.Slide10

Evaluation of volatile oil

Various

pharmacopoeial

procedures are given for the evaluation of volatile oils.

Odour

and

taste

are obviously important in preliminary examination.

Physical measurements including

optical rotation

,

relative density

and

refractive index

are regularly employed for identification and assessment of purity;

similarly.

thin layer chromatograms (TLC).

Capillary

gas chromatographic

profiles are used to determine the proportions of individual components of certain oils. Advances in gas chromatography have now made possible detection of adulteration with synthetic material or unwanted other oils.

Other general tests described in BP include

examination for fixed or

resinified

oils

(residue after evaporation),

foreign esters

(conversion to a crystalline deposit) and

presence of water

(turbidity of a carbon disulphide solution). Slide11

Preparation of volatile oils:

Modern volatile oils stills contain a raw material on perforated trays or in perforated basket.

The still contains a water at the base which is heated by steam coils, and free steam under pressure may also be passed in

.

Tough materials such as barks, seeds and roots may be comminuted to facilitate extraction

but

flowers are usually placed in the still without further treatment as soon as possible after collection. Distillation is frequently performed in the field.Slide12
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Slide14

The distillate which consist of a mixture of oil and water, is condensed and collected in a suitable receiver which is usually a large glass jar with one outlet near the base and another near the top.

The

distillate separates into 2 layers, the oil being withdrawn through the upper outlet and the water from the lower outlet, or vice versa in the case of oils, such as oil of cloves, which are heavier than water.

The oil-saturated aqueous layer may be returned to the still or may form an article for commerce, as in the case of rose water and orange-flower water.Slide15

Peppermint leaf and peppermint oil

The

fresh

leaves

of

Mentha

piperita

(F.

Labiatae

) is required to contain not less than 1.2% of volatile oil. The oil is obtained from the same plant by steam distillation using the

flowering tops

.

The peppermint oil was required to contain not less than 44% of free alcohols calculated as

menthol

, 15-32% of ketones calculated as

menthone

, and 4.5-10% of esters calculated as

menthyl

acetate

.

Menthol

is

terpene

alcohol occurs as a white crystalline solid, topical application of menthol to the skin causing refreshing cooling sensation followed by a slight burning and pickling sensation.

Uses

:

Peppermint oil used as

inhalation

(for coughs and colds),

decongestant

,

antitussive

, analgesic,

anesthetic

,

counter-irritant

,

anti-

pruritic

, enteric coated capsules containing peppermint oil used for irritable bowel syndrome. Slide16
Slide17

Spearmint oil

Spearmint or ordinary garden mint consists of the dried leaf and flowering top of

Mentha

spicata

.

Oil of spearmint contains

(-)-

carvone

,

(-)-limonene

,

phellandrene

and esters.

Uses:

Oil of spearmint finds wide application especially in the

flavouring

of chewing gums and toothpastes. The oil does not possess the medicinal virtue of peppermint oil.Slide18
Slide19

Natural camphor

Natural camphor is a white, dextrorotatory

ketone

, C

10

H

16

O, obtained from the wood of

Cinnamomum

camphora

.

Camphor occurs in small, colorless crystals or in transparent fibrous blocks. It has a characteristic odour and a pungent, aromatic taste, which is followed by a sensation of cold.

Camphor oil contains in addition to camphor ,

safrole

,

borneol

, vanillin and

terpineol

, a number of

sesquiterpens

.

Uses: camphor is used externally as

rubefacient

, and internally as a mild antiseptic and carminative

.Slide20
Slide21

Eucalyptus oil

Oil

of eucalyptus is distilled from the fresh leaves of various species of Eucalyptus (f.

Myrtaceae

) and rectified.

Only a

ceratin

number of species produce oils suitable for medicinal use.

The chief

requirement

is a high cineole content and the absence of appreciable quantities of

phellandrene

and

aldehydes

.

Suitable oils are derived from

E.

polybractea

,

E.

smithii

,

E. globules

and

E.

australiana

.

Oil of eucalyptus is a colourless or pale yellow liquid. It has an aromatic and

compharaceous

odour; a pungent,

camphoraceous

tast

, which is followed by a sensation of cold. It is required to contain not less than 70.0% of cineole.

Eucalyptus oil is much used for

alleviating the symptoms of nasopharyngeal infections

,

for treating coughs

and as a

decongestant

.

It is taken internally in the form of mixtures, inhalations, lozenges and pastilles and applied externally as ointments and liniments

. Slide22
Slide23

Caraway fruit and oil

Caraway consists of the dried ripe fruits of

Carum

carvi

(f.

Umbelliferae

), a biennial herb about 1 m high. It occurs both wild and cultivated in central and

noerthern

Europe.

Caraway contains about 3-7% of volatile oil.

Caraway oil consists largely of the

ketone

carvone

and the

terpene

limonene

.

Uses: the fruits and oil are used in medicine for

flavouring

and as

carminatives

. The carminative and antispasmodic properties have been experimentally verified

.Slide24
Slide25

Dill oil

Dill consists of the dried, ripe fruits of

Anethum

graveolens

(f.

Umbelliferae

), a small annual indigenous to southern Europe.

The Dill oil resembles oil of caraway in containing

carvone

and

limonene

. The European fruits yield about 3-4% of volatile oil, which should contain from 43-63% of

carvone

.

Uses: dill is used as

carminative

and

flavor

; it is much used in

infant’s gripe water

.Slide26
Slide27

Coriander and coriander oil

Coriander is the dried nearly ripe fruit of

Coriandrum

sativum

, an annually about 0.7 m high with white pinkish flower.

Coriander fruit contain up to 1.8% of volatile oil.

The distilled oil contains 65-70% of

(+)-linalool

(

coriandrol

), depending on the source, and smaller amounts of

α-

pinene

,

γ-

terpinene

,

limonene

and

p

-cymene

together with various non-linalool alcohols and esters.

The unripe plant has an pleasant, mousy odour, which is also present in oil distilled from unripe fruits (mainly

aldehydes

such as n-decanal ).

Uses: pharmaceutically coriander and its oils are used as

flavouring agent

and

carminative

.Slide28