1. Volatile oil

2. Volatile oil
Volatile oils are the odorous and volatile products of various plant and animal species. As they have a tendency to undergo evaporation on being exposed to the air even at an ambient temperature, they are invariably termed as volatile oils, essential oil or ethereal oils. They mostly contribute to the odoriferous constituents or ‘essences’ of the aromatic plants that are used abundantly in enhancing the aroma by seasoning of eatables.
These volatile oils are usually formed by two modes namely-
first, by hydrolysis of some glycosides; and
secondly, by the protoplasm directly.
Volatile oils may be present in particular secretor parts such as in mesophyl (Eucalyptus leaves), sub-epidermal tissues of lemon and orange, in petals (rose), in bark and leaves (cinnamon) and in rind (orange).

3. Properties/Characteristics of volatile oil:
Physical Characteristics of Volatile Oils
It is a well known fact that the volatile oils usually differ from each other with regard to their chemical constitutions. However, they invariably possess a number of physical characteristics as stated below, namely:
(a) Odour: Most volatile oils do possess very pleasant and characteristic odour which vary considerably from one specimen to another.(Detection When a drop of the volatile oil is soaked on a filter paper, an expert may judge its quality and genuinity and may also differentiate between the authentic pure sample from the adulterated one by their individual odours.)
(b) Nature: In general, the volatile oils are mobile liquids at ordinary temperatures. However, there are a few exceptions, for instance:(i) Anise Oil: It solidifies at 15oC and melts at 17oC,

4. Physical Characteristics of Volatile Oils (con.)
(c) Volatility: The essential oils are mostly volatile completely, with the exception of a few of them e.g., ‘oil of lemon’, ‘oil of orange’, that contain also an additional non-volatile substance of gummy nature. Both the volatile and their pure components do possess high vapor pressures, and hence evaporate completely and rapidly when exposed to atmosphere.(Detection Volatile oils do not leave a stain when soaked on a piece of filter paper, whereas a fixed oil does. Thus, it also checks its adulteration.) (d) Colour: Invariably, the colour of freshly obtained volatile oils are more or less colorless, but on prolonged storage they usually undergo both oxidation and resinification thereby rendering it dark in colour. The darkened volatile oil can be redistilled to obtain once again the colorless sample.(Prevention The volatile oils must be stored in a cool, dry place and preferably filled upto the brim in amber glass bottle having an airtight stopper.)

5. Physical Characteristics of Volatile Oils (con.)
(e)Refractive Index: The refractive index of volatile oils vary from 1.42 to They are mostly characterized by high refractive indices. Detection The pure authentic volatile oils have definite refractive index as specified in official compendia, whereas the adulterated oils will show different values.
(f ) Optical Rotation: A large number of volatile oils exhibit optical activity by virtue of the chemical constitution of the oil(s) or its constitution. It gives some vital information with regard to the source and authenticity of the oil sample,
(g) Specific Gravity: The specific gravity of volatile oils ranges between 0.8 to 1.17.
(h) Solubility: The majority of volatile oils are immiscible with water, but are soluble in absolutealcohol and several other organic solvents e.g., ether, chloroform, carbon disulphide, acetone,hexane, ethyl acetate etc.
Exceptions:Oil of Rose gives a turbid solution due to the presence of paraffin hydrocarbons that are very sparingly soluble in alcohol.
(i)Rancidity: No rancidity occurs in case of volatile oil.
In addition to the above stated physical parameters there are certain other equally valuable and important characteristic data for the identification as well as detection of adulteration in a sample of volatile oil, namely: boiling range, flash point, evaporation residue, molecular refraction

6. Chemical Characteristics of Volatile Oils
It has been observed that plethora of volatile oils are found to be more or less ‘complex mixtures’ essentially comprising of different class of chemical constituents. Therefore, they are found to vary widely in the chemical composition and vis-à-vis their therapeutic applications.The chemical constituents of volatile oils are recognized as ‘terpenes’ that may contain one or several isoprene units.

7. Functions of volatile oil:
Functions in plants:
They sometimes protect plants from harmful effects of animals and insects.
Sometimes helps in pollination through insects
B.Therapeutic function:
Carminative; e.g. clove oil
Antispasmodic; Bitter almond oil
Antibacterial; e.g. Pine tar oil
Aromatic stimulant; e.g. peppermint oil
Anthelmintic; e.g. thymol
Expectorant e.g. turpentine oil
Antiseptic; e.g. Eucalyptus oil
Diuretic; e.g. Juniper oil
Antipruritic; e.g. Camphor
C.Pharmaceutical use
As a flavoring agent
As a preservative

8. Give the differences Between Volatile oil and Fixed oils.
Features
Fixed oil
Volatile oil
Chemical composition
Ester of long chain fatty acid and glycerol
Oxygenated or dehydrogenated or hydrogenated derivatives of hydrocarbons
Evaporation
Do not evaporate at room temperature or ordinary temperature
Evaporate at room temperature
Flavor
Fixed oil has mild odor
Strong characteristics odor
Rancidity
May occur
Does not occur
Greasiness
They are greasy and leave stain when evaporated
They are greasy but do not leave stain when evaporated
Process of collection
They are mainly collected through expression from seed
Usually they are collected by distillation process
examples
Soybean oil, castor oil
Cinnamon oil, clove oil

9. Classification of Volatile Oils
Example
Source
Hydro-carbon
α-pinine
Turpentine oil
2. Alcohol-volatile oil
Linalool-
Peppermint oil
3. Aldehyde-volatile oil
Cinnamaldehyde-
Cinnamon oil
4. Ketone-volatile oil
Carvone-
Spearmint oil
5. Phenol-volatile oil
Eugenol-
Clove oil

10. Classification of Volatile Oils
Example
Source
6. Phenolic-ether-volatile oil
Safrole-
Nutmeg oil
7. Oxide-volatile oil
Cineol-
Eucalyptus oil
8.Ester-volatile oil
Menthyl acetate-
Oil of wintergreen
9.Peroxide-volatile oil
Ascardiol-
Chenopodium oil
10. others
Methyl salicylate-

11. Chemistry of volatile oil:
Volatile oil consists of the following compounds:
Terpene type compounds
Aromatic type compounds
A.Terpene type compounds: Terpenes are defined as natural products whose structure may be divided into isoprene units. These units arise from acetate-mevalonate pathway and are branched chain of 5-carbon units containing two unsaturation in head and tail fusion.

12. Follwing types of isoprenes are usually found-
Monoterpene(C10H16): composed of 2 isoprene units
Sesquiterpene(C15H24): composed of 3 isoprene units
Diterpene(C20H32): composed of 4 isoprene units
Triterpene(C30H48): composed of 6 isoprene units
Tetraterpene(C40H64): composed of 8 isoprene units
 Most of the volatile oil are composed of monoterpenes are classified into two groups.
Acyclic; e.g. Geraniol

13. Cyclic monoterpenes are classified into-
i.Monocyclic; e.g. Limonene
ii.Dicyclic; e.g. α-pinine

14. 2.Aromatic type compounds: Volatile oils having benzene ring with a propane side chain belong to these group of compounds. These type of compounds are generally biosynthesized by a Shikimic acid pathway; e.g. Cinnamaldehyde,
Anethole

15. Preparation of Volatile Oils
There are in all four established methods whereby the preparation of volatile oils from various plant sources may be accomplished, namely:
(i) Direct Steam Distillation,
(ii) Expression,
(iii) Extraction and
(iv) Enzymatic Hydrolysis.

16. Direct Steam Distillation
In case of direct steam distillation, the freshly cut drug is introduced into the distillation flask. The generated steam is made to pass through the drug material as shown in Fig. 5.1, and the volatile oil content along with the steam on being passed through the water condenser is collected in Florentine Flasks of the type FLW or FHW depending on whether
the resulting oil is lighter than water or heavier than water.

17. E2 = Florentine Flask for oils heavier than water (OHW), and
The various parts of the assembly for the preparation of volatile oils by steam distillation are as follows:
A = Steam generator (Copper),
B = Distillation Flask,
C = Sand bath,
D = Water condenser,
E1 = Florentine Flask for oils lighter than water (OLW),
E2 = Florentine Flask for oils heavier than water (OHW), and
F = Beaker

18. Different modes of distillation
In actual practice, however, there are three different modes of distillation depending exclusively on the condition of the plant substance, namely:
(a) Water Distillation: It is mostly applicable to such plant material which is dried initially in air and the constituents are not degraded by boiling upto 100oC.
Example: Turpentine Oil—In this instance, the crude turpentine oleoresin is added directly into the distillation flask and subsequently subjected to distillation.
(b) Water and Steam Distillation: It is often suitable for such plant material, constituents of which undergo degradation by direct boiling.
Example: Clove Oil, Cinnamon Oil—In this case, the crude drug is first macerated with water for several hours, prior to steam distillation.
(c) Direct Steam Distillation: It is invariably applicable to fresh drugs that is loaded with sufficient natural moisture and hence no maceration is required.
Example: Pippermint Oil, Spearmint Oil—In this instance the freshly cut drug is added directly into the distillation flask prior to steam distillation.

19. Expression
A number of volatile oils mostly undergo decomposition on being subjected to distillation. Likewise, volatile oils found in the rind of the fruit, such as: orange, lemon and bergamot peel, are best obtained by extrusion i.e., by the application of pressure. Even on a commercial scale these oils are produced by extrusion so as to preserve the natural fragrance that otherwise get deteriorated by distillation process. In actual practice, however, the expression may be accomplished by any one of the four following processes, namely:
(a) Sponge Method: The citrus fruit (e.g., orange, lemon, grape fruit, bergamot) is first washed to remove the dirt, and then cut into halves to remove the juice completely. The rind is turned inside out by hand and squeezed when the secretary glands rupture. The oozed volatile oil is collected by means of the sponge and subsequently squeezed in a vessel. The oil floating on the surface is separated.

20. (b) Scarification Process (Ecuelle a Piquer):
Ecuelle a piquer is a specially designed apparatus (Fig. 5.2) first introduced on the Revieras in France, which is nothing but a large bowl meant for pricking the outer surface of citrus fruits. It is more or less a large funnel made of copper having its inner layer tinned properly. The inner layer has numerous pointed metal needles just long enough to penetrate the epidermis. The lower stem of the apparatus serve two purposes; first, as a receiver for the oil; and secondly, as a handle. Now, the freshly washed lemons are placed in the bowl and rotated repeatedly when the oil glands are punctured (scarified) thereby discharging the oil right into the handle. The liquid, thus collected, is transferred to another vessel, where on keeping the clear oil may be decanted and filtered.

21. (c) Raspings Process: In this process the outer surface of the peel of citrous fruits containing the oil gland is skillfully removed by a grater. The ‘raspings’ are now placed in horsehair bags and pressed strongly so as to ooze out the oil stored in the oil glands. Initially, the liquid has a turbid appearance but on allowing it to stand the oil separates out which may be decanted and filtered subsequently.
(d) Mechanical Process: A substantial quantum of volatile oil across the globe is now prepared by various mechanical means solely based on the above principles. However, the use of heavy duty centrifugal devices may also be incorporated so as to ease the separation of oil/water emulsions invariably formed. It is pertinent to mention here that with the advent of modern mechanical devices the oil output has increased appreciably and the older methods have only remained for the sake of history.

22. (3) Extraction
The extraction process is particularly useful for such plant sources which either contain very small amount of volatile oils or the oil contents are extremely susceptible to decomposition by the exposure to steam. In such cases the recovery of volatile oils is not commercially feasible.
Examples: Volatile oils obtained from various flowers like Jasmine ; Sweat violet ; Gardenia; Acacia.
 In general, the extraction of volatile oil from natural sources is carried out by two different methods, namely:
(a) Extraction with volatile solvents e.g., Hexane, Benzene and
(b) Extraction with non-volatile solvents e.g., Tallow, Lard, Olive oil

23. (a) Extraction with Volatile Solvents The plant material containing the volatile oil is usually extracted with a low boiling volatile solvent, such as n-hexane, benzene, petroleum ether etc., either by adopting the method of hot continuous extraction (Soxhlet extraction) or by percolation. The resulting volatile oil containing solvent is removed under reduced pressure when the volatile oil will remain in the flask.
(b) Extraction with Non-Volatile Solvents This process is usually employed for the preparation of the finest brands of perfume oil i.e., the natural flower oils. In this instance, the volatile oil content usually present in the fresh plant sources eg., flower petals, is so scanty that oil removal is not commercially viable by any other methods. Grassein Southern France, is the well known centre for the extraction of flower volatile oil in the world. There are three methods that are used for the extraction of volatile oils from flowers with nonvolatile solvents, namely:
(i) Enfleurage Method,
(ii) Pneumatic Method, and
(iii) Meceration Method.

24. (i) Enfleurage Method:
A thick layer of molten lard and tallow (beef fat) is applied on either surfaces of pre-cleaned glass plates that are securely placed in a covered wooden frame (or the chasis) Each glass plate is liberally sprinkled with fresh flower petals to cover its top surface only. These plates are now stacked one over the other and enclosed in the wooden frame, whereby each layer of the flower shall be enclosed between two layers of the fat. Such batteries of loaded plates are allowed to remain for 24hours, after which the flowers are removed and recharged with fresh lots. This very process is repeated religiously for several weeks till the fatty layers appear to be fully saturated with the essential oils of the flowers or until a certain desired concentration of it is accomplished. Example: Jasmine flowers —The whole process lasts nearly seventy days.

25. (ii) Pneumatic Method: The basic principle of this method is very much like the ‘enfleurage method’. In this particular instance, the current of warm-air is made to pass through the flowers , and the subsequent air loaded with suspended volatile oil particles is then routed through a fine spray of molten fat in a closed chamber wherein the volatile oil gets absorbed promptly.
(iii) Maceration Method: The fresh flower petals are gently and carefully heated in molten fat (lard, tallow, or fixed oil), stirred frequently until complete exhaustion takes place. The flowers are then strained, squeezed and the exuded fat is returned to the main bulk of the fat, unless and until a desired concentration is achieved. The volatile oil containing fat is allowed to cool and is recovered by three successive extractions with absolute alcohol.

26. (4)Enzymatic Hydrolysis
It has been observed that the volatile oil is normally found in plant substances in the form of odourless glycosidal combinations. However, the odoriferous components are liberated free only by hydrolysis of such aforesaid glycosides. A few typical examples of such volatile components are given below:
a.Volatile Oil of Bitter Almond (Benzaldehyde) It is found to be present in the kernels of bitter almond in the form of the glyoside amygdalin:
b. Volatile Oil of Black Mustard The volatile oil component is present is allylisothiocyanate in the form of the naturally occurring glycosides sinigrin:

27. Turpentine oil
Common names:Turpentine , gum turpentine, gum thus, turpentine oil , turpentine balsam
Biological name:Turpentine oil or spirits of turpentine is the volatile oil obtained by distillation of Oleoresin present in Pinus palustris and other species of Pinus Family: Pinaceae
Habitat: Portugal, Greece, Poland, France
Constituents: It contains-(65%)α-pinine, (30%) β -pinine and 5% other including α-terpenene, β-terpenene
Uses: Carminative;Stimulant;Tonic;Expectorant;Diuretic;Antiseptic;
Counter irritant;Flavouring agent, as wax solvent.

28. Peppermint oil
Common names: Peppermint , menthol
Botanical name: peppermint oil is obtained from the dried leaves and flowering tops of the plant Mentha piperita and Mentha arvensis; Family: Lamiaceae
Habitat: Indigenous to Europe and naturalized in Northern USA,Canada
Use: Carminative;Stimulant; Counter irritant;Flavouring agent; in production of peppermint water;in chewing gum, candy toothpaste.

29. Constituents
Constituents:It contains 1% volatile oil, resin and tannin. Following volatile oils are found-
1.Menthol(Alcohol volatile oil)
2.Ester
i. Menthyl acetate
ii.Methyl isovalerate
3.Ketone
i.Menthone
ii.Mentholfuran
ii. Neomenthone
iv. Isomenthone

30. i.Acetc acid;ii. Valeric acid
4.Terpenes
α-pinine
Limonene
β-phellandrene
Aldehyde
i. Acetaldehyde-CH3CHO
ii. Isovaleraldehyde-
iii.Cinnamaldehyde-
Acid
i.Acetc acid;ii. Valeric acid

31. Cinnamon oil
Common Name(s): Cinnamon , cinnamomon , ceylon cinnamon , Chinese cinnamon ,Chinese cassia , Saigon cinnamon .
Biological source: Cinnamon oil is derived from various parts of Cinnamomum zeylanicum; Cinnamomum lourerii, Cinnamomum cassia. Family: Lauraceae
Habitat---Indigenous to China. Cochin-China and Annam. Also cultivated in Sumatra, Ceylon, Japan, Java, Mexico and South America.
Constituents:The principle constituent of this volatile oil is cinnamadehyde. The volatile oil also contains terpenes such as pinene,phellandrene etc. It also contains tannin, mannitol, Manganese
Use: Blood Sugar Control; Candida Yeast Infections; Stomach Bug/Flu; Irritable Bowel Syndrome; Cancer Preventer; Arthritis/Osteoporosis; Anti-Bacterial/Anti Microbial; Food Preservative; Odor Neutralizer; Alertness, Memory & Cognitive Development; Anti-oxidant , Lowering LDL cholesterol & triglycerides; Insect Repellant, Alzheimer’s Disease, cold sore throat.

32. Spearmint oil  
Common names: Curled Mint, Fish Mint, Garden Mint, Green Mint,
Biological source: Spearmint oil is extracted by steam distilling the flowering tops of Mentha spicata and Mentha cardiac; Family: Labiaceae
Habitat: It is native to Europe and southwest Asia, but has become naturalized in other parts of the world. It is naturalized throughout the United States and Canada.
Chemical composition:The main chemical components of spearmint oil are α-pinene, β-pinene, carvone, 1,8-cineole, linalool, limonene, myrcene, caryophyllene and menthol (0.5% compared to the 40% in peppermint)
Use: The therapeutic properties of spearmint oil are antiseptic, antispasmodic, carminative, cephalic, emmenagogue, insecticide, restorative and stimulant.

33. Clove oil Common name: Clove , caryophyllus
Biological source: it is the volatile oil obtained from steam distillation of dried flower buds of Eugenia caryophyllus; Family: Myrtaceae
Habitat: A tree native to the Molucca Islands beside New Guinea and southern Philipinnes. Mainly imports from Madagascar and Indonesia
Constituents: 15-20% volatile oil with eugenol as main component ( 85-90%); Flavonoids (quercetin and kaemferol derivatives);Tannins,furfural,ketone
Use: Primarly as spice;The essential oil has marked antibacterial activity and is used as antiseptic and local anaesthetic (eugenol) in dentistry;Has a moderate role as carminative stomachic and tonic

34. Nutmeg oil Common name: Myristica oil , jatiphala
Biological source: It is the volatile oil obtained from steam distillation of dried kernels of the ripe-seed of Myristica fragrans; Family: Myristicaceae
Constituents: The main chemical components of nutmeg oil are α-pinene, camphene, β-pinene, sabinene, myrcene, a-phellandrene, α -terpinene, limonene, 1,8-cineole, γ-terpinene, linalool, terpinen-4-ol, safrole, methyl eugenol and myristicin.
Use: The therapeutic properties of Nutmeg oil are analgesic, antirheumatic, antiseptic, antispasmodic, carminative, digestive, emmenagogue, laxative, parturient, stimulant and tonic.

35. Eucalyptus oil
Common name: Blue gum, stringy bark tree, Tasmanian blue gum
Biological source: It is the volatile oil obtained from steam distillation of fresh leaves of Eucalyptus Globulus Family: Myrtaceae
Habitat: A tall evergreen tree native to Australia and Tasmania and cultivated elsewhere.
Constituents: Up to 3.5% volatile oil (with up to 70% eucalyptol/cineole, plus terpineole and pinene, geraniol), polyphenolic acids (including caffeic and gallic), flavonoids (including eucalyptin, hyperoside and rutin), tannins, aldehydes, bitter resin.
Use: Antiseptic, deodorant, antispasmodic, febrifuge, expectorant, stimulant, reduces blood sugar levels, vermifuge, aromatic, secretolytic, rubefacient, decongestant

36. Oil of wintergreen
Synonym: Wintergreen , teaberry , checkerberry , gaultheria oil , boxberry , deerberry , mountain tea , Canada tea , partridgeberry
Biological source: Wintergreen essential oil is created by steam distilling the leaves of Gaultheria procumbens family: Ericaceae
Habitat: Gaultheria isnative to northeastern North America from Newfoundland west to southeastern Manitoba, and south to Alabama
Chemical compositionThe main chemical components of wintergreen oil are menthyl salicylate and gaultherilene.
Use:
Analgesic; Anti-inflammatory; Anti-rheumatic; Antiseptic; Antispasmodic, Disinfectant; Diuretic; Stimulant (bone); Warming

37. Chenopodium oil
Synonym: American Wormseed oil, Chenopodiol; Chenoposan
Biological source: Chenopodium oil is the essential oil collected by steam distillation of fresh aerial parts of Chenopodium ambrosioides and Chenopodium anthlmenticum
Constituents: There are many compounds in Chenopodium. The compound considered to be the active ingredient is ascaridole, a monoterpene. The major components of oil of chenopodium are: ascaridole (60-80%), isoascaridole, p-cymene, limonene. The level of the different compounds varies depending on the part of the plant, age of the plant, and whether it is dried or fresh plant material.
Use: Oil of Chenopodium and paste from fresh plant are primarily used to treat internal parasites in humans and non-ruminant animals.