From this post Evaluation of Excipients of Natural origin, we will learn differently chemical tests to identify Tragacanth, Acacia, Starch or Iodine and Honey

Chemical test for Tragacanth

gum tragacanth 220340 960 720

Aim: To identify the chemical characters of a given excipient.

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

Biological Source: A dried exudation obtained from the stems and branches of Astragalus gummifer and other Asiatic species of Astragalus. Family: Leguminosae

Description:

  • Colour: white to slight yellow color
  • Odour: odourless
  • Taste: micilaginous taste
  • Shape: The gum seeps from the plant in twisted ribbons or flakes that can be powdered.
  • Solubility: 1 gm of the sample in 50 ml of water swells to foma smooth, stiff, opalescent mucilage; insoluble in ethanol and does not swell in 60% (w/v) aqueous ethanol.
  • Chemical Constituents: Tragacanthin (water soluble part), Bassorin (water insoluble part)
  • Uses: Demulcent, emollient, thickening agent, emulsifying agent, binding agent.

Procedure:

  1. 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.
    1. To one part, add 1.5 ml of sodium hydroxide solution and Fehling’s solution, warm on water bath: red precipitate is produced.
    2. To the second part, add barium chloride solution (10%): No precipitate is obtained (distinction fromagar)
  2. To a 0.5% w/v solution of the gum, add 20% w/v solution of lead acetate: A voluminous flocculent precipitate is obtained (distinction from acacia).
  3. Mount a small quantity of powder in ruthenium red and examine microscopically. Particles do not acquire pink colour (distinction from Indian tragacanth).
  4. To 0.1 g of powder, add N/50 Iodine: The mixture acquires an olive green colour (distinction fromacacia and agar).
  5. Powder is warmed with 5% aqueous caustic potash Canary yellow colour will obtain Indian tragacanthIt is obtained from SterculiaurensRoxburgh; (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 solution of Ruthenium red.

Report: From the above morphological characters and chemical tests the given excipient is identified as Tragacanth

Chemical test for Acacia

gum arabic 763043 1280

Aim: To identify the chemical characters of given excipient acacia.

Biological Source: Indian gum is the dried gummy exudation obtained from the stems and branches of Acacia Arabica Family: Leguminosae

Description:

  • Colour: white to slight yellow color
  • Odour: Odourless
  • Taste: Bland and mucilaginous taste
  • Shape: Tears are mostly spheroidal or ovoid in shape with approx. diameter of 2.5-3.0 cm
  • Solubility: soluble in water, insoluble in alcohol.
  • Chemical Constituents: Gum Arabic consists almost entirely of glycosidal acid named Arabic acid, combined with potassium, magnesium and calcium By hydrolysis Arabic acid yields 1 molecule of l-sharmose, 2 molecules of D-galactose and 3 molecules of l-arabinose and an aldobionic acid. It also contains diastase and an oxidase enzyme.
  • Uses: Demulcent, emollient, thickening agent, emulsifying agent, binding agent also used to form coacervates for microencapsulation of drug.

Procedures:

  • 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 oxidase enzyme.
  • A 10% aqueous solution of acacia fails to produce any precipitate with 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 are ascertained by boiling with Fehling’s solution to give a brick-red precipitate of cuprous oxide.

Report: From the above morphological characters and chemical tests the given excipient is identified as Acacia.

Chemical test for starch

Starches

Aim: To identify the chemical characters of the given excipient.

Biological Source: Starch consist of polysaccharide granules obtained from the grains of maize Zea mays L. or of rice Oryza sativa L or of wheat Triticum sativum L. Family: Gramine or from the tubers of the potato Solanum tuberosum L. Family: Solanaceae

Description:

  • Colour: white (Rice and maize starch), cream(wheat), slight yellow (potato)
  • Odour: Odourless
  • Test: mucilaginous taste
  • Shape: Fine powder or irregular, angular masses
  • Solubility: It is sparingly soluble in cold water and mostly soluble in hot water after cooling it forms gel.
  • Chemical constituents: Amylose, Amylopectin
  • Uses: Dusting powder, Pharmaceutical aid, protective and demulcent, Tablet disintegrating agent and diluents.

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.

Report: From the above morphological characters and chemical tests the given excipient is identified as starch.

Chemical test for Honey

honey 1006972 960 720

Aim: To identify the chemical characters of the given excipient.

Biological Sources: Honey is the saccharine liquid prepared from the nectar of the flowers by the hive-bee Apis mellifera, Apis dorsata and bees of other species of Apis. Family: Apidae

Description:

  • Colour: slight yellow to brown yellow
  • Odour: pleasant
  • Taste: Sweet
  • Solubility: soluble in water and insoluble in alcohol 
  • Chemical Constituents: Glucose 35% (+3%), fructose 45%(+5%), sucrose 2-3% and water (14-20%). Dextrin, maltose, gum traces of succinic acid, acetic acid, volatile oil, amino acid, protein, coloring matters etc.
  • Uses: Demulcent, nutritive, mild laxative. It is used as an important component of linctuses and cough mixture, sweetening agent, antiseptic and bactericidal. Used as a vehicle in ayurvedic and unani preparations.

Chemical Tests:

TestObservationInference
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


Adultered honey (added sugar)
Molisch’s Test: Honey is treated with alpha Naphthol and concentrated sulphuric acid.Purple colourPresence of carbohydrates
Reducing Sugar Test: Heat honey to add a drop of mixture of Fehling’s solution A & BThe brick red colour of cuprous oxidePresence of monosaccharide

Report: From the above morphological characters and chemical tests the given excipient is identified as Honey.

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