lecture 34 - volatile oils 1 [compatibility mode]

8/3/2019 Lecture 34 - Volatile Oils 1 [Compatibility Mode]

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PHARM. DChemical Pharmacognosy- I

Lecture 34May 26th, 2011

Volatile Oils

M. Ahsan KhalidM. Ahsan Khalid, B, B.. PharmPharm, Pharm. D, Pharm. DMM. Phil. Phil Scholar (RIPS/RIU)Scholar (RIPS/RIU)

HIPSHIPS--HUKICHUKIC


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VOLATILE OILS

Volatile or essential oils are volatile in steam.

They differ entirely in both chemical andphysical properties from fixed oils.

They are secreted in:oil cells e.g. CinnamonOil glands e.g. CloveSecretion ducts (vittae) e.g. AniseGlandular hairs e. g. Chamomile

They are frequently associated with othersubstances such as gums ( oleo gum) andresins (oleoresin) or both (oleo gum resin)

They tend to resinify on exposure to air.


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Production and Uses of Volatile Oils

There are about 100 commercially valuable volatileoils directly derived from plants.

Volatile oils are used:

1- For their therapeutic action: antiseptic e.g.

thyme and clove, carminative e.g. Mentha2- Flavoring (e.g. oil of lemon),

3- in perfumery (e.g. oil of rose)

4- starting materials for the synthesis of othercompounds (e.g. oil of turpentine).


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For therapeutic purposes they are administeredas inhalations (e.g. eucalyptus oil), orally (e.g.peppermint oil), as gargles and mouthwashes(e.g. thymol) and transdermally (many essentialoils including those of lavender, rosemary andbergamot are employed in the practice ofaromatherapy).

Those oils with a high phenol content, e.g. cloveand thyme have antiseptic properties, whereas

others are used as carminatives. Oils showingantispasmodic activity, and much used inpopular medicine. e.g. fennel, mentha, caraway,chamomile, anise, rosemary.


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Composition of Volatile Oils

Volatile oils are generally mixtures ofhydrocarbons and oxygenatedcompounds derived from these

hydrocarbons.

The odour and taste of volatile oils ismainly determined by these oxygenated

constituents, which are to some extentsoluble in water but more soluble inalcohol.


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Practically all volatile oils consist of chemical

mixtures that are often quite complex; they varywidely in chemical composition.

Almost any type of organic compound may befound in volatile oils (hydrocarbons, alcohols,ketones, aldehydes, ethers, oxides, esters, and

others). usually volatile oils are classifiedaccording to the type of organic compounds..

It is not uncommon for a volatile oil to containover 200 components, and often the traceconstituents are essential to the odor and flavor.The absence of even one component maychange the aroma.


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Physical PropertiesAlthough volatile oils differ greatly in their chemical

constitution, they have a number of physicalproperties in common:

1. They possess characteristic odors.

2. They are characterized by high refractive indices.

3. Most of them are optically active.

4. Their density is generally lower than that of water (theessential oils of sassafras, clove, or cinnamon are the

exceptions).

5. As a rule, volatile oils are immiscible with water, butthey are sufficiently soluble to impart their odor towater. The aromatic waters are dependent on thisslight solubility.


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Difference between Volatile and

Fixed Oils Several points of differentiation exist between

volatile oils and fixed oils.

1. Volatile oils can be distilled from their naturalsources.

2. Volatile oils do not consist of glyceryl esters offatty acids. Hence, they do not leave apermanent grease spot on paper and cannot besaponified with alkalies.

3. Volatile oils do not become rancid as do thefixed oils, but instead, on exposure to light andair, they oxidize and resinify.


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Preparation of volatile oils

The principal methods used in the preparation ofvolatile oils from plants depend on:

1. Distillation in water or steam.

2. Scarification and expression.3. Extraction with solvents.

4. Enzymatic hydrolysis (for glycosidic volatile oilse.g. mustard oil).

5. Enfleurage (extraction of oils used in perfumery).


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Uses of drugs containing essential oils

Pharmacy

Perfumery

Food technology

Miscellaneous industries(as startingmaterials for the synthesis of the active

principles of medicines, vitamins, andfragrances).


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1- Clove (Caryophylli)Origin: the dried flower buds of

Syzygium aromatica, Eugeniaaromaticumor EugeniacaryophyllusF. Myrtaceae

Morphology: reddish brown, 16-21mm long, the lower stalk likeportion (hypanthiumwhich is an extension of thereceptacle) is about 10-13 mmlong, terminating in 4 triangularsepals and a dome- shaped

head of 4 unexpanded petalsenclosing other parts of theflower.


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Powder: Dark brown, with strongaromatic spicy agreeableodour and warm spicyagreeable taste followed bynumbness sensation in the

mouth1. Epidermal cells of sepals,

petals and hypanthiumshowing anomocyticstomata.

2. Oil glands.

3. Parenchyma with clustercrystals of calcium oxalate.

4. Aerenchyma.

5. Xylem vessels and fibres.

6. Fibrous layer of anther andelongated cells of thefilament.

7. Pollen grains: triangular withtruncate apices.

8. Absence of prisms of calcium

oxalate and starch granules.


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Active constituents:

1. Volatile oil (15 -20%) contains eugenol (85%).2. Pyrogallol tannin.

Uses:

1. Local anesthetic for toothache.

2. Antispasmodic and carminative.

3. Spice.

4. In manufacture of vanillin.

Chemical test: 1- sudan III red colour.2- FeCl3 blue colour.

3- KOH: needle crystals of K eugenate.


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Adulteration of clove:

1. Expanded flower

2. Mother clove (fruit): characterized by

the presence of starch.

3. Exhausted clove: lighter than water.

4. Clove stalk: presence of prisms of

calcium oxalate and pseudo crystalsheath.

lecture 34 - volatile oils 1 [compatibility mode]

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