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Renin Angiotensin Mechanism.

"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.
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