"Fibers" in Pharmacognosy.

Fibers

CLASSIFICATION:

1. Vegetable origin – cotton, jute
2. Animal origin – wool, silk
3. Mineral origin – asbestos, glass wool
4. Synthetic origin – nylon, terylene
5. Regenerated from cellulose – rayon
6. Regenerated from protein – milk protein, groundnut

COTTON / RAW COTTON:

BIOLOGICAL SOURCE: 

• Trichomes of seeds of cultivated species of Gossypium herbaceum
• Family: Malvaceae

GEOGRAPHICAL SOURCE: India, Egypt

Collection:

• The capsule of cotton consists contains large number of seeds covered with trichomes
• The trichomes are separated
• Long trichomes are used in preparation of fabric & short ones are used in preparation of surgical dressings
• This non-absorbent cotton, when treated with dilute soda solution for 10 to 15 hours at a higher pressure, gets free of fats.
• The resulting absorbent cotton is dried, sterilized with gamma radiation

Description:

• White, soft to touch

Chemical Tests:

ABSORBENT COTTON:

1. Fibre when treated with N/50 iodine solution & 80% H2SO4 gives a blue stain
2. Fibre when treated with Cuoxam reagent, swells & dissolves
3. Fibre gives a blue stain with chlorzinc iodide.

NON ABSORBENT COTTON:

1. Fibre when treated with Cuoxam reagent, swells & dissolves with ballooning
2. Fibre gives a violet stain with chlorzinc iodide

Uses:

• Fabrics, surgical dressings.

JUTE

• BIOLOGICAL SOURCE: obtained from phloem fibres of Corchorus capsularis
• Family: Tiliaceae.

Description:

• Brown, rough to touch.

Chemical Test:

1. Fibre, when stained with phloroglucinol & HCl, gives a deep red colour
2. Fibre gives a yellow stain with chlorzinc iodide

Uses:

• Preparation of jute bags.

SILK:

• BIOLOGICAL SOURCE: obtained from secretion/cocoon of Bombyx mori
• Family: Bombycidae.

Description:

• Yellow, smooth to touch.

Uses:

• Sutures & ligatures.

Collection:

• The larvae produce fibroin from the mouth glands which gets united with a gum-like secretion known as sericin to form a cocoon.

• These cocoons are exposed to steam & finally plunged in boiling water to separate the gum & the fibres.

Chemical:

• Proteins & subunits made of alanine & glycine.

Chemical Tests:

1. Fibre does not blacken on treatment with lead acetate
2. On treatment with Millon's reagent, it gives a brick red colour

WOOL

• BIOLOGICAL SOURCE: obtained from fleece of sheep Ovis aries
• Family: Bovidae

Description:

• Soft, lustrous.

Preparation:

• Raw wool is washed with water followed by a second washing with soap solution & then treated with sulphuric acid.

• The wool fat is separated by extracting with acetone.

• Thus wool fibre is obtained.

Chemical Test:

• Fibre blackens with lead acetate. (Contains sulphur containing amino acids)

Uses:

• Fabrication, ligatures & sutures.

GLASS WOOL:

• Source: made up of silica, mixture of silica & oxides of aluminium, calcium, boron & magnesium

Uses:

• Insulating material & in the manufacture of filters.

Chemical Tests:

1. Fibre is partly soluble in 60% sulphuric acid
2. Fibre on ignition forms a hard bead

ASBESTOS:

• Source: consists of hydrated magnesium silicates & occurs as white, yellow or green fibres.

Uses:

• Filtering media

Chemical Test:

• Fibre insoluble in warm HCl

NYLON

• Source: Polymer of adipic acid & hexamethylene diamine.

Description:

• It is dull or lustrous, white in colour.

Uses:

• Preparation of sutures & ligatures, sieves & fabrics.

Chemical Tests:

1. Fibre soluble in warm HCl
2. Forms a hard bead on ignition

TERYLENE:

• Source: Polymer of ethylene glycol & terephthalic acid.

Uses:

• Preparation of artificial grafts.

Chemical Tests:

1. Fibre is soluble in formic acid
2. Forms a hard round bead on ignition

RAYON / VISCOUS RAYON / REGENERATED CELLULOSE:

Preparation:

• Cellulose is treated with sodium hydroxide to yield sodium cellulosate.
• This, when treated with carbon disulphide in sodium hydroxide, gives sodium cellulose xanthate.
• The solution is passed through fine nozzles in a bath of sodium sulphate & H2SO4 to yield filaments of viscous rayon.
• It is further made free of sulphur, bleached & washed.

Uses:

• Preparation of surgical dressings & fabric.

SHORT NOTE ON CELLULOSE:

• Cellulose is obtained from wood or cotton
• It is extracted using hot methanol followed by methanolic NaOH treatment
• The solution is further exposed to an explosion process wherein the high pressure is cut down in a very short interval of time
• The cellulose thus obtained is a polymer of glucose units linked together in a beta- 1,4 linkage

Derivatives:

1. Ester: esterification of cellulose yields products such as cellulose nitrate & cellulose acetate which are used in the preparation of films & plasticizers
2. Ether: etherification yields products such as methyl cellulose, CMC, HPMC, HPC. The solubility of these polymers depends on the degree of substitution of hydroxyl group

Uses:

• Stabilizers, suspending agents & in ophthalmic solutions.