Herbal Analysis Lab

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Phytochemistry Lab How to Identify the
Phytoconstituents?
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• The medicinal plants are in use for the treatment
  of various diseases since ages. Therapeutic
  properties are present in various parts of the
• plant such as the leaf, bark, roots, stem,
  flowers, seeds, and fruits.
• The plants owe these therapeutic properties to
  the presence of medically active chemical
  components known as phytoconstituents or
• phytochemicals.
• The phytoconstituents are known for their
  antibacterial, antimicrobial,
• antiprotozoal and other pharmaceutical functions.
• But, how will you identify the phytoconstituents
  in a medicinal plant?

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• The identification process is carried out in a 
• phytochemistry lab. Here are the steps to
  identify
• the different phytoconstituents.

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Alkaloids

• Alkaloids are naturally occurring compounds which
  contain nitrogen and carbon atoms. They are
  primarily found in plants, but also occur in
  bacteria, fungi, and animals. To detect the
  alkaloid in a medicinal plant
• Dissolve the plant extract in chloroform
• Evaporate the chloroform and add acid to the
  residue
• Add different types of reagents to get different
  colour precipitates
• Mayers reagent gives a creamy white precipitate
• Wagners reagent gives an orange precipitate
• Dragendroffs reagent gives an orange-red
  precipitate
• Hagers reagent gives a yellow crystalline
  precipitate.

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Lactones

• Lactones are the class of organic compounds
  containing a cyclic ester and formed by the
  intramolecular condensation of the
  hydroxycarboxylic acid. They are
• known to exhibit anti-inflammatory properties.
  There are two tests to
• detect lactones in a medicinal plant
• 1) Legals test
• Add a mixture of pyridine and sodium
  nitroprusside to the plant extract.
• Then, add sodium hydroxide. The solution will
  turn deep red in colour.
• 2) Bal Jets test
• Treat the plant extract with a solution of sodium
  picrate. The mixture turns yellowish-orange in
  colour indicating the presence of a lactone ring.

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Glycosides

• Glycosides are compounds formed from a simple
  sugar and another non-sugar compound by
• replacement of the hydroxyl group in the sugar
  molecule. Glycosides can be detected in plants by
  two
• methods
• 1) Bal Jets test
• Treat the plant extract with a solution of sodium
  picrate. The mixture turns yellowish-orange in
  colour indicating the presence of glycosides.
• 2) Keller-Killani test
• Add few drops of ferric chloride and 1 ml of
  glacial acetic acid to the plant extract.
• Slowly add concentrated sulphuric acid to the
  above mixture.
• If glycosides are present, a reddish brown ring
  will appear at the intersection point of the two
  liquids

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Tannins

• Tannin is a yellowish coloured derivative of
  gallic acid. It is bitter tasting organic
  substance found in
• the galls, barks, and other plant tissues. Detect
  the presence of tannins with these two tests
• 1) Ferric Chloride test
• Take 2 ml of the plant extract in a test tube.
• Add a solution of ferric chloride drop by drop.
• A blue-black precipitate indicates the presence
  of tannins
• 2) Gelatine test
• Take 1 of gelatine solution containing 10
  sodium chloride.
• Add few drops of it to the plant extract.
• A white precipitate at the bottom of the
  test tube confirms the presence of tannins.

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Proteins

• Proteins are commonly present in many
• medicinal plants and show their presence with
• the Biuret test.
• Add 40 sodium hydroxide and diluted copper
• sulphate solution to the plant extract. Pink,
  blue or violet change in the colour of the
  solution
• indicates the presence of proteins.

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Flavonoids

• Flavonoids are a group of biologically active and
  water-soluble plant compounds responsible for the
  
• colour of the fruits and vegetables. They
  indicate their presence with these tests
• 1) Ferric Chloride test
• Prepare an alcoholic solution of the plant
  extract.
• Take a small quantity of this alcoholic solution
  and add some drops of neutral ferric chloride
  solution
• If flavonoids are present, the solution will turn
  green.
• 2) Shinoda test
• Prepare an alcoholic solution of the plant
  extract.
• Add some pieces of magnesium ribbon to the
  alcoholic solution.
• Add concentrated hydrochloric acid drop by drop.
• Magenta colour of the solution confirms the
  presence of flavonoids.

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Triterpenes

• Triterpenes are the class of chemical compounds
• produced by the plants as a part of their
  self-defence
• mechanism. They can be detected by Salkaowski
  test
• Add concentrated sulphuric acid in drops to the
• chloroform solution of the plant extract. Shake
  well
• and allow it to stand. In few minutes, the lower
  layer will turn yellow in colour.

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Saponins

• Saponins are the chemical compounds with
  soap-like qualities and are found in
• abundance in various plant species.
• When you add plenty of water to the plant extract
  and shake it thoroughly, saponins
• produce foam which remains for about ten
• minutes.

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Volatile Oils, Fixed oils, Fats

• Prepare a solution of the plant extract.
• Put a drop of this solution on the filter paper.
• Lack of permanent stain shows the existence of a
  volatile oil.
• Use two filter papers and crush the extract
  between them.
• A permanent stain shows the presence of fixed
  oils.
• Treat the extract with few drops of
  phenolphthalein and 0.5 N potassium
• hydroxide. Heat the mixture.
• Resulting soap formation shows the existence of
  fats and fixed oil.

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Know more

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