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

VOLATILE OILS• Volatile or essential oils are volatile in steam.

• They differ entirely in both chemical and physical 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 other substances such as gums ( oleo gum) and resins (oleoresin) or both (oleo gum resin)

• They tend to resinify on exposure to air.

Production and Uses of Volatile OilsThere are about 100 commercially valuable volatile

oils 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 other

compounds (e.g. oil of turpentine).

• For therapeutic purposes they are administered as inhalations (e.g. eucalyptus oil), orally (e.g. peppermint oil), as gargles and mouthwashes (e.g. thymol) and transdermally (many essential oils including those of lavender, rosemary and bergamot are employed in the practice of aromatherapy).

• Those oils with a high phenol content, e.g. clove and thyme have antiseptic properties, whereas others are used as carminatives. Oils showing antispasmodic activity, and much used in popular medicine. e.g. fennel, mentha, caraway, chamomile, anise, rosemary.

Composition of Volatile Oils

• Volatile oils are generally mixtures of hydrocarbons and oxygenated compounds derived from these hydrocarbons.

• The odour and taste of volatile oils is mainly determined by these oxygenated constituents, which are to some extent soluble in water but more soluble in alcohol.

• Practically all volatile oils consist of chemical mixtures that are often quite complex; they vary widely in chemical composition.

• Almost any type of organic compound may be found in volatile oils (hydrocarbons, alcohols, ketones, aldehydes, ethers, oxides, esters, and others). “usually volatile oils are classified according to the type of organic compounds”.”.

• It is not uncommon for a volatile oil to contain over 200 components, and often the trace constituents are essential to the odor and flavor. The absence of even one component may change the aroma.

Physical PropertiesAlthough volatile oils differ greatly in their chemical

constitution, they have a number of physical properties 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 (the essential oils of sassafras, clove, or cinnamon are the exceptions).

5. As a rule, volatile oils are immiscible with water, but they are sufficiently soluble to impart their odor to water. The aromatic waters are dependent on this slight solubility.

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 natural sources.

2. Volatile oils do not consist of glyceryl esters of fatty acids. Hence, they do not leave a permanent grease spot on paper and cannot be saponified with alkalies.

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

Preparation of volatile oils

• The principal methods used in the preparation of volatile 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 oils

e.g. mustard oil).5. Enfleurage (extraction of oils used in perfumery).

Uses of drugs containing essential oils

• Pharmacy• Perfumery• Food technology• Miscellaneous industries (as starting

materials for the synthesis of the active principles of medicines, vitamins, and fragrances).

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

Syzygium aromatica , Eugenia aromaticum or Eugenia caryophyllus F. Myrtaceae

Morphology: reddish brown, 16-21 mm long, the lower stalk like portion (hypanthium which is an extension of the receptacle) is about 10-13 mm long, terminating in 4 triangular sepals and a dome- shaped head of 4 unexpanded petals enclosing other parts of the flower.

Powder: dark brown, with strong aromatic spicy agreeable odour and warm spicy agreeable taste followed by numbness sensation in the mouth

1. Epidermal cells of sepals, petals and hypanthium showing anomocytic stomata.

2. Oil glands.

3. Parenchyma with cluster crystals of calcium oxalate.

4. Aerenchyma.

5. Xylem vessels and fibres.

6. Fibrous layer of anther and elongated cells of the filament.

7. Pollen grains: triangular with truncate apices.

8. Absence of prisms of calcium oxalate and starch granules.

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.

Adulteration of clove:1. Expanded flower2. 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 crystal sheath.

2- German chamomileOrigin: the dried expanded

flower heads of Matricaria chamomilla F. Compositae (Asteraceae).

Morphology: flower head (capitulum) is hemispherical with hollow receptacle carrying two types of small sessile flowers called florets:

Marginal or ray florets (white in colour)

Central or disc florets (yellow in colour)

Surrounded by an involucre.

Active constituents: 1- volatile oil contains matricarin which converted to chamazulene by heating.

2- flavonoid glycosides.

Uses: 1- carminative, antispasmodic.2- tranquilizer.3- local anti-inflammatory for sun burns and

diaper rashes.

Chemical test: sudan III : red colour

3- Anise Fruit(Fructus Anisi, Aniseed)

Origin: the dried ripe fruits of Pimpinella Anisum F. Umbelliferae

Morphology: cremocarp, partly separated into its mericarps, often entire attached to a slender pedicel, 2-12 mm long, ovoid, enlarged at the base and tapering at the apex, grayish or greenish grey in colour rough to touch due to the presence of hairs, each mericarp with 5 raised ridges.

Powder: grey, greenish brown or yellowish brown, having strong aromatic agreeable characteristic taste and sweet strongly aromatic taste, showing fragments of:

1. non-glandular, unicellular warty hairs.

2. Branching vitta usually crossed by the cells of the endocarp.

3. Aleurone grains.4. Microrosette crystals of

calcium oxalate.5. Few fibres and pitted

parenchyma.

Active constituents: 1- volatile oil containing anethol

2- fixed oil and protein.

Uses: stimulant, carminative and flavoring agent.

Chemical test: Sudan III

4- Cinnamon Bark(Cortex Cinnamomi)

Origin: the dried bark of the branches of the coppiced trees of Cinnamomum zylanicum F. Lauraceae. deprived of most of its cork and cortex and known as Ceylon Cinnamon.

Morphology: occurs in long, slender sticks about 1 meter in length, compound quills.

Powder: a reddish brown powder with a characteristic pleasant and aromatic odour and taste, showing fragments of:

1. Sclereids, isodiametric, thick wall, lignified, the outer wall is less thickened than the others.

2. Fibres, thick walled lignified, narrow lumen, slit-shaped pits and pointed apices.

3. Starch granules and needle crystals of calcium oxalate.

4. Oil cells.

5. Cork cells are rare.

Active constituents: 0.5-1% volatile oil contains cinnamaldehyde and eugenol

Mucilage and tannins.

Uses: 1- carminative and flavoring agents2- Antiseptic and mild astringent.3- Emmenagogue.

Chemical test: Sudan III, Rhuthenium red, FeCl3 and KOH for eugenol.

5- Cassia Bark(Chinese Cinnamon)

Origin: the dried stem bark of Cinnamomum cassia F. Lauraceae

Morphology: channeled or single quills, up to 40 cm long, earthy brown colour with patches of the thin grayish cork.

Powder: differs than cinnamon in:

1. Odour is less delicate, taste as cinnamon but slightly mucilaginous.

2. Numerous fragments of cork cells, polygonal with slightly thick wall, contains reddish brown content.

3. Fibres are shorter and thicker.

Active constituents: volatile oil contains cinnamaldehyde and no eugenol.

Uses: substitute for cinnamon.

Chemical test: all as cinnamon but negative test for eugenol

6- Cardamom Seed(Semen Cardamomi) الھیل -حب الھال -حبھان

Origin: the dried ripe or nearly ripe seeds of Elettaria cardamomumF. Zingiberaceae, recently separated from the fruit.

Morphology: cardamom has a strong aromatic odour and agreeable aromatic pungent taste. Fruit is ovoid or oblong capsule, green to pale buff in colour contains many seeds. Seed is oblong, ovoid pale ornge to dark reddish brown usually enveloped by a thin colourless membranous arillus.

Active constituents: 1- volatile oil contains terpinyl acetate and cineole.

2- starch, fixed oil and calcium oxalate

Uses: 1- flavoring agent in pharmaceutical industry.2- spice

Chemical test: Sudan III

Adulterants:1. Loose seeds: they yield less volatile oil than those

which stored in the pericarp until required for use.2. Cardamom husk: characterized by the presence

of fibres, sclereids and large vessels which are absent in the seeds.

7- Mentha Herb (Peppermint)(Herba Mentha Piperitae)

Origin: the dried leaves and flowering tops of Mentha piperita F. Labiatae

Powder: green to light olive green, with an aromatic characteristic odour and an aromatic taste followed by a sensation of cold in the mouth. It is characterized microscopically by the presence of fragments of:

1. Epidermal cells with wavy walls and diacytic stomata.

2. Non-glandular hairs.

3. Glandular labiaceous hair, unicellular stalk multicellular head consists of 8-16 cells radiating from a common center.

4. Different types of xylem vessels, fibres and wood parenchyma.

5. Smooth spherical pollen grains.

6. NO CALCIUM OXALATE.

Active constituents: 1- volatile oil contains menthol2- tannin.

Uses:1. carminative, flavoring agent and aromatic

stimulant.2. Menthol is used in pharmaceutical preparations

as local antipruritic, counter irritant and antiseptic.

3. Used in tooth paste, mouth wash and similar oral preparations.

4. Recently the oil is used for treatment of colitis.

Chemical test: Sudan III

8- Ginger, Zingiber, Zanjabeel(Rhizoma Zingiberis)

Origin: the dried rhizome of Zingiber officinale F. Zingiberaceae, deprived of the dark outer tissues and known as unbleached Jamaica ginger.

Morphology: ginger occurs in horizontal laterally flattened branching pieces, 4-16 cm long,1.5-6.5 cm wide and up to 2 cm thick, pale buff or light brown, longitudinally striated. It has an agreeable aromatic odour and an agreeable pungent aromatic taste.

Powder: powdered ginger is yellowish white having an agreeable aromatic odour and an agreeable aromatic pungent taste. Microscopically, it is characterized by the presence of:

1. thin walled parenchyma containing starch granules.

2. Starch granules: simple, flat, oval, oblong with terminal protruberance in which eccentric hilum is situated with transverse striations.

3. Thin walled septate fibres.

4. Non-lignified xylem vessels.

5. Yellowish brown oleo-resin masses, free or in cells.

6. Absence of scleried cells or calcium oxalate.

Active constituents:1. volatile oil contains monoterpenes

(phellandrene, camphene, cineole, citral and borneol) and sesquiterpenes (zingiberene and bisabolene).

2. Resin, starch and mucilage.

Uses:1. carminative and stimulant.2. Antiemetic.3. Antirheumatic.4. Condiment.