Pharmacognosy

9. Casein
Source: It is the main protein in milk and constitutes 80 % of milk proteins.
Available in two types:
1. Acid casein: Warm skimmed milk is acidified with dilute acid, the whey is separated, curd is washed several
times, dries and pulverized.
2. Rennet Casein: Skimmed milk treated with an enzyme (curdled milk from the stomach of an unweaned
calf, containing rennin and used in curdling milk for cheese)., rennet extract product is separated and
purified.
Description: White, slightly yellowish, tasteless, odorless, amorphous solid, hygroscopic in nature. Stable
when dry but deteriorates rapidly when wet.
Insoluble in water, soluble in dilute alkalies, concentrated acids. Precipitates from dilute acidic solutions.
Chemical composition: Casein is a phosphor protein containing 0.85% phosphorus and 0.75% sulfur. It has 15
amino acids.
Uses: Dietary supplement source of protein. Base for standardization of proteolytic enzymes. Emulsifying
agent. For sizing of textiles and paper. As an adhesive, preparation of casein plastic and casein paints.

10. Gelatin
Synonyms: Gelatina, gel foam, Puragel
Biological Source: It is a protein extracted by partial
hydrolysis of animal collagenous tissue like skin, bones,
tendons and ligaments boiled in water.
Description: In the form of flakes, sheets, shreds or a
fine or coarse powder. Pale yellow to amber color. Faint
odor.
Insoluble in cold water but soluble in hot water. In cold
water, it swells, softens and absorbs water about 5-10
times of its weight. With hot water it forms a jelly upon
cooling. Soluble in a mixture of glycerine and water.
Insoluble in fixed oils and volatile oils, alcohol,
chloroform and ether. Stable in the dry condition. Upon
getting moist, it degrades due to microbial attack.

11. Preparation of Gelatin:
• Bones are defatted and decalcified with organic solvents and mineral
acids.
• The defatted matter is treated with water at 85⁰ C in successive quantities
during which the collagen dissolves into gelatin.
• It is bleached and concentrated under reduced pressure .
• It is allowed t settle in trays and dry in a drying room.
Gelatin quality:
Bloom Strength: Weight in gm, which upon applying to a plunger of 11.7 mm
diameter under controlled conditions, produce a depression of 4mm deep in
a jelly maintained at 10 ⁰ C and containing 6.66 % gelatin in water.
BP mentions jelly strength of NLT 150 blooms for coating of pills, as vehicles
for suppositories and as emulsifying agent.
Gelatin for capsule manufacture and microbial culture media, higher jelly
strengths are used.

12. Chemical constituents: Various amino acids. Mainly lysine. Tryptophan is absent. Gluten
protein is also present.
Identification:
1. Upon heating with sodalime it evolves ammonia.
2. Upon treating with mercuric nitrate, it gives a white ppt which upon warming forms a
brick red color change.
3. It is precipitated by trinitrophenol and tannic acid solution.
4. It is not precipitated by alum, lead acetate or acids indicating that it does not have
chondrin.
Chondrin is a bluish-white gelatin-like substance, being a protein-carbohydrate complex
and can be obtained by boiling cartilage in water. The cartilage is a connective tissue that
contains cells embedded in a matrix of chondrin. Chondrin is made up of
two proteins chondroalbunoid and chondromucoid.

13. Uses:
• Manufacture of hard and soft gelatin capsule
shells.
• Preparing of pessaries, pastes, pastilles and
suppositories.
• As a hemostatic in the form of absorbable gelatin
sponge.
• Treatment of brittle finger and nail defects.
• Vehicle for some injections like heparin.
• Bacteriological culture media
• Absorbable gelatin sponge and gelatin film