Volatile oils Definition

• It is a distilled oils obtained from plant tissue or animal sources.

• They are widely used in perfumes, flavoring and medicines.

• Their chemical composition differs, for

example, terpenes, aldehydes, ketons or phenols, oxygen, sulfur, nitrogen.

Volatile OilsVolatile OilsFixed OilsFixed Oils

VolatileVolatile Non-volatileNon-volatile

HydrocarbonsHydrocarbons

not leave permanent stain

on filter paper

TriglyceridesTriglycerides

leave permanent stain on

filter paper

Non-greasyNon-greasyGreasyGreasy

On storage Not rancid Not rancid but but

rather rather resinifyresinify

On storage rancidrancid upon upon

exposure to Oexposure to O22

Kinds of Essential Oils

The principal components of essential oils are terpenes and aromatic compounds.

Why do plants produce essential oils?

• Attraction effectTo insects, birds and other animals for pollination and seed dispersal.

• Repellant effectPlants produce offensive odors or bitter substances to repel pests or predators, or inhibit the growth of molds or harmful bacteria. (Protection against insects and fungi).

• Waste products of metabolism.

Characters of volatile oils

1.Physical characters: • Colorless volatile liquid• Have high refractive index and optically

active• Immiscible with water• Soluble in organic solvent• Resinification when storage due to darken in

color when exposed to light

2. Chemical characters:

• It is a mixture of hydrocarbons and oxygenated compounds (such as alcohol, ketons, aldehydes, phenol, esters).

• Some oils consists of one main component as oil of clove (eugenol). oil of menthe (menthol).

• The properties of the volatile oils are determined by the number of isoprene units.

• Terpenes and terpenoides are the primary constituents of the essential oils of many types of plants and floweres.

What are terpenes ?• Terpenes are defined as natural products

whose structures may be divided into isoprene units.

• Hemiterpenes: consists of a single isoprene units have the molecular formula C5H8

• Monoterpenes: consists of a two isoprene units have the molecular formula C10H16

• Sesquiterpenes: consists of a three isoprene units have the molecular formula C15H24

• Diterpene: consists of a four isoprene units have the molecular formula C20H32

• Sesterterpenes: consists of a five isoprene units have the molecular formula C25H40

• Triterpenes: consists of a six isoprene units have the molecular formula C30H48

Classes of Terpenes present in V.O.:A.Monoterpenes1. Acyclic.2. Monocyclic.3. Bicyclic.4. Aromatic.B. Sesquiterpenes1. Monocyclic.2. Bicyclic.C. Oxygenated hydrocarbons: (oxygenated

terpenes) e.g. alcohols, esters, phenols, oxides, peroxides, aldehydes and ketones.

Chemical constituents and odour of volatile oils

According to the major constituents, volatile oils acquired different odour as:

• Fruity odors of ester and lactones• Pleasant odor of ketones• Bitter almond odor of nitrile

Chemical constituents and action• Sesquterpene hepatic and glandular

stimulant, anti-inflammatory, antiallergic and nasal decongestant.

• Monoterpene hydrocarbon antiviral, stimulant, irritant and immuno-stimulant.

• Esters spasmolytic, fungicidal, soothing to the skin, anti-inflammatory.

• ketones cell regenerative, mucolytic and neurotoxic.

• Aldehyde sedative, anti-inflammatory, antiviral and relaxing.

• Oxides expectorant and antiviral.• Esters soothing.

Pharmacological importance of volatile oils:

1.Antiseptic and preservative as Lavender, thyme, clove

2.Antispasmodic as Anise, fennel, menthe, chamomile

3.Sedative as clove4.Irritating agent , externally increase in

capillary blood flow as eucalyptus. Internally

5.Stimulates mucus cell , so used as expectorant

Medicinal uses • As infusion or separated volatile oils and their isolates by inhalation or

orally as gargles • Local stimulants• Carminatives• Mild antiseptic • Bacteriostatics• Local irritants• Anthelmentics• Local analgesic• In powder form used as spices and condiments in food to impart aroma

and flavor and act as preservative • In perfume industries , cosmetic preparation • Insecticides

Preparation of volatile oils:

Methods

DistillationWater dist.

Water and steam dist.

Steam dist.

ExpressionSponge methodScarificationRasping processMachines

ExtractionVolatile solventNon-volatile solvent

Methods for preparation of Volatile Oils:

1.Distillation.2.Scarification and expression.3.Solvent extraction.4.Enzymatic hydrolysis of glycosides.

1. Distillation Methods Principle: When two immiscible liquid are heated they

will boil at a temperature below the boiling point of either one.

Types of distillation:A.Simple steam distillation (water-

distillation).B.Saturated stem distillation (water and

steam).

A. Simple steam distillation (water distillation):

1.Immersing the plant directly in a container filled with water, then boiled.

2.Heterogeneous vapors are condensed on a cold surface and collected in a special receiver.

3.Oil separates from water on the bases of difference in density and immiscibility.

Cohobation: is the return of the aromatic water to still to be

redistilled in order to improve the yield of oil.

19

B. Saturated stem distillation:

1.Saturated stem.2.The plant not contact with water.3.Stem pressure and temperature could be

modified according to the composition of the oil.Thermolabile as esters – need lower pressure and

temperature.High boiling point as sesquiterpenoids – need

higher pressure and temperature.

B. Scarification and expression:

• It based on puncturing and/or squeezing of the plant material to liberate the oil.

• It is used for heat sensitive oils which are present in large amounts in outer peels of fruits as citrus fruits.

Preparation and purification of oil The peel consist of two parts Outer part: colored, rich in waxes and pigments

and oil glands. Inner part: white, formed of pectin and cellulose.

The method includes:

I. Squeezing Methods.II.Scarification (Ecuelle - a - piquer method).III.Expression Method.

I. Squeezing Methods

a) Squeezing with water:

1. Squeezing of the peel under stream of water, yield emulsion of oil, water, pectin, cellulose, pigment and wax.

2. Removal of water, pectin and cellulose by centrifugation.

3. Removal of wax by strong cooling, followed by filtration or decantation.

b) Sponge Method:

1. Fruits are washed, cut into halves and fleshy part removed.

2. Peels are soaked in water and pressed between a convex projection and a sponge.

3. Saturated sponge is squeezed in vessel and emulsion centrifuged and cooled.

II. Scarification (Ecuelle - a - piquer method)

Based on puncturing (scarifying ) the surface of whole fruits

Instrument used is funnel-shaped, consisting of a shallow bowl with a tubular projection at the center.

The bowl-like part bears internally numerous pins long enough to scarify the oil glands and release the oil.

III.Expression Method

1. Removing the outer layer of the peel, collecting in special bags followed by strong pressing.

2. Oil obtained is collected, left to stand, decant, and filtered.

Machine processesIt based on whole fruits are charged into

machines in which the peels are removed, sprayed with water, squeezed or pressed and oil collected through wool filters

C. Extraction methods

It is used for preparation of delicate flower oils such as Jasmine, which contain either

Small amounts of oils. Oils which decompose by heat. According to the solvent used they classified into:

• Non- volatile solvent extraction• Volatile solvent extraction• Extraction with supercritical gas

Volatile oils

Hydrocarbon

Alcohol

Phenols and

phenolic ethers

Monohhydric e.g.

Thymol, Carvacro

l ,Anisol

Aldehyd and

ketones

Aldehydes

AliphaticAcyclic

e.g Citronellol, Citral

Alicyclice.g.

Perillaldehyde

Aromatice.g

Benzaldehyde,Va

nillin

Ketonesc

Acyclice.g

aceton

Alicyclic

Aromatic

Bicyclice.g.

Camphor,Fenchon

e

EstersOxide & Peroxide

s

�ُEster of

aliphaticE,geranyl acetate

Aromatice.g

Benzyl benzoate

Containing

nitrogene.g.

Anthranilate

Oxide Peroxide

Monoterpene

e.g 1,8-cineole

Sesquiterpenee.g.

Bisabolol

Aliphatic AlicyclicAcyclic Alicyclic Aromatic

Monoe.g

Myrecene

Ocimene

Sesquiterpene

.e.g Farnecen

e

Bicyclic

Monoterpene

Tricyclice.g

Santalene

Monoe.g.

Limonene

Sesquiterpenee.g

Cadinenes

3,6 membere

d ringe.g

Thajone, Carvone

AromaticBenzyl alcohol

Bicyclicl

MonocMenthol

Dihydrice.g.

Eugenolisoeugen

ol

TrihydricMyristinisomyrist

in

Tetrahydric

Parsely camphor

TricyclicSantalol

Monoterpene

Borneol

SesquiterCarotol

Volatile Oils

Hydrocarbon AlcohoslPhenols&

Phenolicethers

Aldehyde& Ketones

EstersOxides &

Preoxides

HydrocarbonV.O.

Acyclic

Monoterpinee.g. Myrecene

Ocimene

Sesquiterpenee.g. Farnesene

Alicyclic Aromatic

MonoLimonene

BicyclicTricyclic

e,.g. Santtalene

Monoterpene

Sesquiterpenee.g. naphthalene derivative

cadinene

3,6 membered ringe.g. Thajane

carane

4,6 membered ring e.G pinane

AlcoholV.O.

Aliphatic Alicyclic Aromatic

Benzyl alcohol

Monocyclice.g. Menthol

BicycliclTricyclic

SesquterpenoidSantalol

MonoterpeneBorneol

SesquiterpeneCarotol

Saturatedd Unsaturated

Phenols and phenoliccomponds

Monohhydric e.g .

ThymolCarvacrol

AnisolAnathole9 Anise camphor0

Dihydrice.g. EugenolIsoeugenol

TrihydricMyristin

TetrahydricParsely apiole

Parsley camphor

Aldehyd and ketones

Aldehydes Ketonesc

AliphaticAcyclic

e.G citronellolcitral

Alicyclice.g .

Perill aldehyde

Aromatice.g benzaldehydeSalicylaldehyde

Vanillin

Alicyclic Aromatic

Monocyclice.g.carvoneMenthone

Acyclice.g. Acetone

Bicyclice.G Fenchone

Camphore

Esters

�ُEster of aliphatice.g. geranyl acetate

Benzyl acetate

Aromatice.g

Benzyl salicylateMethyl salicylate

Containing nitrogene.g methyl anthranilate

Oxide & Peroxi

Oxide Peroxide

Monoterpenee.g 1,8 -

Sesquiterpenee.g .

Hydrocarbon V. O.

Acyclic, Monoterpene

Myrcene and OcimeneOccurrence: in Lemon grass, Cympobogon Isolation: By fractional distillation, Purification by H2O soluble

phenate with NaOH non- phenolic fraction (insoluble part) fractional distillation.

Detection of Myrecene in the presence of Ocimene:

Myrecene with Potassium permanganate in acetone Succinic acid + Lead

1. Myrecene (Lead succinate) needle crystals.

2. Ocimene (Lead succinate) rhomboidal crystals.

Sesquiterpene

Farnesene Occurrence: Humulous lupulusPreparation: by fractional distillation.Uses: flavoring agent

Monocyclic, Alicyclic Hydrocarbon

Limonene Occurrence: in OrangePreparation: by fractional distillation.Uses: Flavoring agent.

Alicyclic, bicyclic monoterpene hydrocarbon

α-Pinene

Occurrence: coniferous oil, lemon, corianderIsolation: 1. By fractional distillation. 2. By precipitation as nitroso chloride crystal then aniline

α-pinene.Uses: • Manufacture of borneol and camphor.• Mucolytic in cough mixture.

Alicyclic, monocyclic, sesquiterpene hydrocarbon

Zingiberene

Occurrence: GingerIsolation: 1. By fractional distillation under vacuum. Test: • Zingiberene + Hydrochloric acid crystal of

dihydrochloride .

Alicyclic bicyclic sesquiterpene hydrocarbon

Azulene (coloured H.C.) e.g. Chamazulene

Test: Azulene + mineral acid ( H2SO4)

Crystalline derivatives, then decompose by water.

Uses Anti-inflammatory - Cosmetic preparation

Aromatic hydrocarbon P-cymeneOccurrence: lemon, lavanderIsolation: by fractional distillation.• Purification from terpenoid by oxidation with

cold dil. KMnO4.

• From limonene or pinene by dehydration, heating with sulphur p-cymene

Test: With Potassium permanganate crystal of P – hydroxyisopropyl benzoic acid.

Uses: Perfuming soaps.

AlcoholsPreparation1. By additive products: using Cacl2 solid,

regeneration by water, ext. with ether or benzene.2. Chromatography.3. Derivatization: depending upon the presence of functional

alc. gp., addition reaction as oxidation, halogenation, hydration for unsaturated as borneol & geraniol

4. Estrification using either:1- Phthalic anhydride.2- Boric acid –1ry are more react than 2ry, 3ry not react3- Succenic anhydride.5. Dehydration: 3ry more react then 2ry, 1ry resistant except

geraniol using ZnCl2.

•Acyclic terpene alcohol

Citronellol

Occurrence: Oil of rose and citronella.

Preparation:1.By fractional distillation of the hydro distilled oil.2.Semi synthetically from geraniol or nerol by hydrogenation.

Uses: In Cosmetic preparation.

Geraniol and Nerol

Occurrence:Geraniol In oils of palme rosa, rose, geranium.Nerol In oils of Neroli, bergamot.Preparation: Nerol is difficult to be obtained in a pure form. Geraniol formed a solid derivatives with calcium chloride , while nerol does not form a complex. Geraniol heated with dehydrating agent, diterpenUses:•In perfume, cosmetic preparation.

LinaloolOccurrence: In oil of Lavander , Lemon, Rose,  Preparation: Fractional distillation Heating with glacial acitic acid -------mixture of geraniol, nerol and terpeniolWith chromic acid -------------- citralWith halogen acids ---------- Linalyl derivative (linalyl chloride) Uses:In perfume, cosmetic preparation

Alicyclic terpene alcoholAlicyclic Monocyclic Monoterpene alcohol Menthol Occurrence: In oil of peppermint Preparation:Naturally: From oils by cooling and deposited crystals by centrifuge. Synthesis: Catalytic reduction of thymol using cupper chromate.  Test of identityCrystals + conc. Sulphuric acid + vanillin sulphuric reagent ----orange yellow color + water -------violet Crystals + glacial acetic acid + three drops of conc. Sulphuric acid + one drop of conc. Nitric acid ----no green or bluish color (thymol gives green color)  Uses : Antiseptic, Counter irritant, Carminative, gastric sedative, Flavoring agents in mouthwashes & toothpastes

• Alicyclic bicyclic monoterpene alcohol Borneol, Isoborneol Source: Nutmeg, lavender, coriander Preparation: By fractional dist, Purification by acidphethalate Synthesis: 1. From α-pinene + HCL gas at -10 o α-pinene HCL,

Isomerization bornyl chloride + KOH borneol

2. From camphor using Na amalgam in alc. borneol

Separation of Borneol and Camphor:Phethalic anhydride with NaOH Sod. Salt which

soluble in water, extract with org. solvent camphor in org. solvent and Sodium Salt of borneol in aq.

Separation of Mixture Of α-pinene, borneol and camphor: 1. α-Pinene by fractional distillation.2. Camphor by oxime.3. Borneol by acid phthalate ester. Uses Sedative, Antiseptic, Counter irritant and room sprays.

Aromatic alcohol-Benzyl alcohol (low volatility) Source: Jasmin, balsamPreparation By fractional dist -Bad storage bitter almond odor + crystal

of benzoic acid• Test Oxidation with chromic acid + H2SO4

benzoic acid • Uses Perfume and Cosmetic

Phenols and phenolic esters: Uses: Antiseptic, germicidal, Properties: acidic, unstable, sol. In alkali. With FeCl3 blue, violet color With Br bromo derivativePreparation: By cooling. By shaking the oil with dil. KOH aq.

Layer ext. by ether or steam distillation.

Monohydric phenols

1-Thymol 2- Anethol ( Anise camphor)Source: F. Labiatae Anise, FennelPreparation: Cooling if in large amounts. Fractional distillation.Uses: Flavoring, cosmetic, mouth wash gargleTests:

• FeCl3+ H2SO4---blue + KMnO4 -----P-anisald.

• Na OH ---pale red color dark when left.

• Synthesis of Thymol 1- Menthone + Bromin/quinolin

Thymol 2- Piperitone Thymol • Synthesis of Anethol Alc. anisole + propionald/ Hcl, H2SO4/ pyridine Anethol

Dihydric phenol Eugenol (pale yellow oily liquid)Source: Clove, Cinnamon, NutmegPreparation: Oil + aq. NaOH , ext. with ether, Phenolic

insol. Salt, acidify, then stem distillation or ext. with ether

Test: • with alc. Fecl3 blue• with aq. FeCl3 grayish yellow• with KOH needle crystal

Uses: – Local anesthetic in toothache (inhibit nerve conducting),

Anti-inflamatory , Bactericidal, Preparation of vanillin.

Ald. and KetonsPreparation:1. By fractional dist.2. By cooling if solid & in large amounts Assay 1- Condensation Reaction with hydroxylamine oxime Exss. Hydroxylamine HCL is added to known

weight of oil, release HCL is titrated against standared. alc. KOH using methyl red for ald & dimethyl yellow for ketons

Acyclic monoterpene ald.

Citronellal Citral Source: Lemone oil CitrusPreparation: Fractional distillation.

Uses: Perfumes Not used in perfume Insect repellent but in Cosmetic preparation.Separation of citral a from citral b by sodium bisulfate,

citral a is sparingly soluble but citral b is readily soluble.

Aromatic ald.

Benzald. Vanillin Source Oil of bitter almond Vanilla podPrep. Enzymatic hyd. Fermentation of vanilla podsStem dist., pur. By calc. hyd. Ext. with ether ,cryst. From alc /ferric sulphate , redistillation Uses Manuifacture of dye flavoring, perfumes Perfumes Synthesis of vanillin• from lignin ( biproduct of paper)• from Eugenol

Alicyclic bicyclic monoterpeneFenchone Camphor Fennel lavender, rosmary

Preparation:By fractional dist. Steam dist, solidify on the wall (cooling)Uses:Counter irritant preservative Flavoring agents antisepticPerfumes• Synthesis of camphor 1- from pinene 2- borneolReaction Camphor + sod. Metal in alc borneol & isoborneol

Ketons• Acyclic (acetone)• Alicyclic monoterpene Menthone Carvone Diosphenol (Buchu camphor)• Mentha, mentha buchu caraway Buchu• By oxime by NaHSO3 cooling

• Regene. By acid recover by NaOH• Carminatives, antiseptic.

• Alicyclic bicyclic monoterpeneFenchone Camphor Fennel lavender, rosmaryBy fractional dist. Steam dist, solidify on the wall(cooling) Counter irritant preservative Flavoring agents antisepticPerfumes• Syntesis of camphor 1- from pinenen 2- borneolReaction Camphor + sod. Metal in alc. borneol & isoborneol

Test to differ. Bet. Natural & synthetic camphor• + vanillin / HCL yellow /green /blue

colour in natural Yellow only in synthetic• Test for chloride negative with natural Positive with syntheticSeparation of camphor & borneol• + hydroxylamine oxime formation

of camphor• Then add dil acid, oxime dissolved & borneol

removed by ext with solvent

Oxide & peroxide

Monoterpene oxide Cineol ( eucalyptol)Source EucalyptusPrep. Fractional distillation, then coolingTest + hydroquinone colorless prism

or rhomboid crystalUses Local anesthetic, Antiseptic, anti-inflammatory,expectorant

Monoterpenoid peroxideAscaridoleSources oil of chenopodiumPrep. Fractional dist under vacuum ( avoid high temp. to prevent explosion)

Uses Anthelementic

Organosulpher compounds Allyl isothiocyanate Source black mustered Prep. Enzymatic hydrolysis. ,then distillation

( heaver than water)Uses Local rubefacient in plasters Flavoring agents