Category: Pharmacognosy and Phytochemistry

Aim

To identify the chemical characters of the given sample.

Chemical Tests and Observations

Test	Observation	Inference
Fiehe’s test: Take about 3ml of honey + 2ml of ether and shake thoroughly and allow the 2 layers to separate and evaporate to dryness. The upper etherial layer is separated and put in a china dish and evaporate, to the residue add 1% resorcinol and HCl.	Transient pink colour Permanent red colour	Pure honey Adulterated honey(Invert sugar)
Molisch’s Test: Honey is treated with alpha Naphthol and concentrated sulphuric acid	Purple colour	Presence of carbohydrate
Reducing Sugar Test: Heat honey to this add a drop of a mixture of Fehling’s solution A & B	The brick red colour of cuprous oxide	Presence of monosaccharide

Conclusion

From the above morphological characters and chemical tests, the given crude drug is identified as Honey.

References

1.Kokate CK. Practical Pharmacognosy, 4 edition, VallabhPrakashan. Delhi; 1994: 98

Aim

To identify the chemical characters of the given sample.

Principle

Amylose forms a colloidal dispersion in hot water whereas amylopectin is completely insoluble. The structure of amylose consists of long polymer chains of glucose units connected by an alpha acetal linkage. Starch – Amylose shows a very small portion of an amylose chain. All of the
monomer units are alpha -D-glucose, and all the alpha acetal links connect C #1 of one glucose and to C #4 of the next glucose. As a result of the bond angles in the αacetal linkage, amylose actually forms a spiral much like a coiled spring. See the graphic below, which show four views
in turning from a side to an end view.

Chemical Test for Starch or Iodine

Amylose in starch is responsible for the formation of deep blue colour in the presence of iodine. The iodine molecule slips inside of the amylose coil. Iodine – KI Reagent: Iodine is not very soluble in water; therefore the iodine reagent is made by dissolving iodine in water in the
presence of potassium iodide. This makes a linear triiodide ion complex with is soluble that slips into the coil of the starch causing an intense blue-black colour.

Conclusion

From the above morphological characters and chemical tests, the given crude drug is identified as starch.

References

1.Kokate CK. Practical Pharmacognosy, 4 edition, VallabhPrakashan. Delhi; 1994: 98

Aim

To identify the chemical characters of the given sample.

Principle

Gelatin is occurred in thin sheets, strips or granular powder. High-grade gelatin light yellow, semi-crystalline substance. It is Odourless and tasteless. In cold water, it swells up and slowly dissolves on warming to form a viscous solution.

Chemical Tests

• When gelatin is heated with soda lime in the dry test tube, ammonia is evolved due to the presence of a nitrogenous compound in gelatin.
• Gelatin solution is added to Million’s reagent to give a white ppt, which turns red on heating.
• Gelatin gives buff white ppt with tannic acid solution.
• Biuret test to 3 ml of test solution of gelatin. NaOH (1ml of 5%) is added whereby white to whitish buff coloured ppt is formed which does not dissolve on heating.
• Yellow ppt. is formed on adding picric acid to solution of gelatin.
• Yellow ppt. is formed on adding picric acid to solution of gelatin.

Conclusion

From the above morphological characters and chemical tests, the given crude drug is identified as Gelatin.

References

1.Kokate CK. Practical Pharmacognosy, 4 edition, VallabhPrakashan. Delhi; 1994: 98

Aim

To identify the chemical characters of a given sample.

Test and Observations

Test	Observation	Inference
Boil 1gm of agar with 10ml of water until the solution is affected, cool to room temperature	A slip jet is formed. (Jelly like mass is formed)	Agar
0.2% solution of agar, + aqueous solution of tannic acid	No Precipitate is formed	Distinction from gelatin
Warm little sample in alcoholic solution of pot. Hydroxide	Canary yellow colour is produced	Agar present
Mount a small quantity of powder in the solution of ruthenium red and examine microscopically	Particles acquire red or pink colour	Presence of the mucilage in agar.
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
Add 0.5ml of conc. HCl to 4ml of 0.5% solution of agar. Heat it on the water bath for 30minutes, cool at room temperature and divide into two portions. a) Add 3ml of 10% NaOH solution and Fehling’s solution A and B in equal quantities and warm over the water bath. b) Add 10% of barium chloride solution.	Red ppt of cuprous oxide is obtained Slight white ppt of barium sulphate is obtained	Reducing sugars are present
Incinerate agar to ash, add a drop of con.HCl observe under the microscope	Fragments of diatoms	Sulphate in agar

Conclusion

From the above morphological characters and chemical tests, the given crude drug is identified as Agar.

References

1.Kokate CK. Practical Pharmacognosy, 4 edition, VallabhPrakashan. Delhi; 1994: 98.

Aim

To identify the chemical characters of a given sample.

Requirements

Gum Arabic consists almost entirely of glycosidic acid named Arabic acid, combined with potassium, magnesium and calcium. By hydrolysis Arabic acid yields 1 molecule of l-rhamnose, 2 molecules of D – galactose and 3 molecules of l– arabinose and an aldobionic acid. It also
contains diastase and an oxidase enzyme.

Proccedure

• Dissolve about 0.25 gm of the coarsely powdered drug in 5 ml of distilled water by shaking in the cold. Add 0.5 ml of hydrogen peroxide and 0.5 ml of benzidine solution, shake and allow to stand for few minutes; a deep blue colour or greenish-blue colour is formed due to the presence of the oxidase enzyme.
• A 10% aqueous solution of acacia fails to produce any precipitate with a dilute solution of lead acetate (a clear distinction from Agar and Tragacanth); it does not give any colour change with Iodine solution (a marked distinction from starch and dextrin), and it never produces a bluish-black colour with FeCl3 solution (an apparent distinction from tannins).
• Hydrolysis of an aqueous solution of acacia with dilute HCl yields reducing sugars whose presence is ascertained by boiling with Fehling’s solution to give a brick-red precipitate of cuprous oxide

Conclusion

From the above morphological characters and chemical tests, the given crude drug is identified as Acacia.

References

1.Kokate CK. Practical Pharmacognosy, 4 edition, VallabhPrakashan. Delhi; 1994: 98

Aim

To identify the chemical characters of a given sample.

Principle

Unorganized drugs, as the name suggests, are drugs that show no definite cellular structure. These are derived from plant, animal or mineral sources by some process of extraction and followed by purification if necessary. Unorganized drugs are fairly homogenous and may be solids, semisolids or liquids. These may be differentiated by observing the solubility in alcohol and then applying other physical and chemical standards. TragacanthTragacanth is the dried gummy exudation from the stem of Astragalusgummifer, Labillardiere and other species of Astragalus (Fam. Leguminosae). It occurs in flat or curved ribbon-shaped flakes. Odourless and almost tasteless, white or pale yellowish-white, somewhat translucent, horny; fracture short.

Chemicals Required

• Hydrochloric acid
• Sodium hydroxide solution
• Fehling’s solution
• Barium chloride solution
• Lead acetate
• Ruthenium red
• Iodine Caustic potash

Proccedure

• To 4 ml of 0.5% w/v solution, add 0.5 ml of hydrochloric acid and heat for 30 minutes on a water bath. Divide the liquid into two parts. (a). To one part, add 1.5 ml of sodium hydroxide solution and Fehling’s solution, warm on water bath: red precipitate is produced. (b). To the the second part, add barium chloride solution (10%): No precipitate is obtained (distinction from agar)
• To a 0.5% w/v solution of the gum, add 20% w/v solution of lead acetate: A voluminous the flocculent precipitate is obtained (distinction from acacia)
• Mount a small quantity of powder in ruthenium red and examine microscopically: Particles do not acquire pink colour (distinction from Indian tragacanth)
• To 0.1 g of powder, add N/50 Iodine: The mixture acquires an olive green colour (distinction from acacia and agar).
• The powder is warmed with 5% aqueous caustic potash: Canary yellow colour will obtain. Indian tragacanth. It is obtained from Sterculiaurens Roxburgh; (Fam: Sterculiaceae). It is insoluble in alkali. It has acetous (acetic acid like) odour and starch is absent. It gives brownish colour when boiled with aqueous KOH. It is stained pink by the solution of Ruthenium red.

Conclusion

From the above morphological characters and chemical tests, the given crude drug is identified as Tragacanth.

References

1.Kokate CK. Practical Pharmacognosy, 4 edition, Vallabh Prakashan. Delhi; 1994: 9