EXPERIMENT NO.3 ANALYSIS OF AGAR BY CHEMICAL TEST | PHARMACOGNOSY & PHYTOCHEMISTRY - I PRACTICAL

EXPERIMENT NO.3. ANALYSIS OF AGAR BY CHEMICAL TEST

Aim: Analysis of Agar by chemical tests.

Reference: 1. Mayur R. Bhurat, Md. Rageeb Md. Usman, Sanjay A. Nagdev, Practical Pharmacognosy & Phytochemistry – I, Published by S. Vikas And Company (Medical Publisher) page. No. 14 – 15.

2. Dr. K.R Khandelwal, Dr. Vrunda sethi, Textbook of Practical Pharmacognosy, Pubished by Nirali Prakashan, Twenty-fifth Edition, page. No. 27.1

Requirements:

Apparatus: Test tubes, Beaker, Holder, Burner, Water bath, Tripod stand, Copper gauze etc.

Chemicals: o-naphthol, Conc.H,SO,, Tannic acid, Potassium hydroxide, Ruthenium Red,’ Lodine, Hydrochloric acid, Sodium hydroxide, Barium chloride etc. )

Theory: Biological Source: It is the dried gelatinous substances obtained from Gelidium amansii Lamouroux, and other species of red algae like Pterocladia.

Family: Gelidiaceae.

Description:

Color: White to slight yellow and sometime grayish in color.

Odour: Odourless.

Taste: Mucilagenous taste.

'Shape: Present in various form like strips, sheets, flakes or coarse powder.

Solubility: It is insoluble in cold water and soluble in hot water after cooling it forms gel.

Chemical Constituents: It contains two heterogeneous polysaccharides components.

(a). Agarose (70%): It is a neutral galactose polymer free from sulphate. It is responsible for the gel strength of agar. It is composed of D-galactose and 3, 6 unianhydro L-galactose unit. It contains about 3.5% cellulose and 6 % nitrogen containing substances.

(b) Agaropectin: It is generally responsible for the viscosity of agar solution. An acidic sulphonated component where in 1, 3 linked D-galactose and the galactouronic acid (an uronic acid) are, partly esterified with sulphuric acid.

Uses: It is uses as a bulk laxative (an agent to induce active movement of the bowels) and in chronic constipation (unmanageable constipation), In the preparation of vaginal capsules and suppositories, To prepare nutrient media in bacteriological culture, In industrial applications like emulsion, sizing, silk textiles, adhesives and thickening ice cream.

Chemical Test of Agar: 

SR.NO	CHEMICAL TEST	OBSERVATION	INFERENCE
A)	Preliminary Test.   1. Colour	White	Acacia, Tragacanth, Agar, Starch
	2. Odour	Odorless	Acacia, Tragacanth, Agar, Starch
	3. Taste	Mucilaginous	Agar, Acacia, Tragacanth, Starch
B)	General Test. 1. Mix small quantity with water and allow to stand	Gummy or mucilaginous nature of drugs and does not dissolve completely.	Gums & Mucilage, such as acacia, tragacanth, agar etc.
C)	Solubility in Alcohol	Soluble	Balsams, Aloes
		Insolube	Acacia, tragacanth, agar, gelatin
D)	Insoluble in Alcohol. 1.  Mount in alcohol & irrigate with water	Particles swell and ultimately dissolve or become diffused	Tragacanth, agar, gelatin.
	2. Warm with caustic soda (5%)	Canary yellow	Agar, tragacanth
	3. Mount in N/50 iodine	No colour reaction	Agar,
		Blue specks appears.	Tragacanth
	4.  . Mount in ruthenium red	Stains pink	Agar
	5. Boil about 1 part with 100 parts of water.	Stiff jelly like mass on cooling.	Agar
E)	Confirmatory Test:
	1. Sample solution (Hot)  + BaCl2 reagents	No Precipitate is formed	Agar is present
	2.  Sample solution + Fehling’s solution + Heat	Red ppt.	Agar is present
	3. Add 1 drop of N/10 solution of iodine to, 10ml of decoction of agar: Rapidly cool under tap water to room temperature.	Crimson or Pale yellow colour is produced ~	Agar is present
	4. Incinerate agar to ash, add a drop of conc. HCI, observe under microscope	Fragments of diatoms	Agar is confirmed.

Result: The given Sample of Crude drug was identified by performing chemical test and the sample was found to be Agar.