ALKALOIDS,ISOLATION

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ALKALOIDS,ISOLATION ITS
CLASSIFICATION

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By - Jaspreet Rekhi www.rhombnet.com
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DEFINATION OF ALKALOIDS

• These are the organic products of natural or
  synthetic origin which are basic in nature
  contain one or more than one nitrogen atoms,
  normally of heterocyclic nature possess
  specific physiological actions on human or animal
  body, when used in small quantites.
• The term is derived from the word alkali-like
  hence they resemble some of characters of
  naturally occuring amines.

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TYPES OF ALKALOIDS
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• TRUE ALKALOIDS These contain heterocyclic
  nitrogen, which is derived from amino acids
  always basic in nature. These alkaloids are toxic
  normally present in plants as salts of organic
  acids e.g. Morphine, Codeine

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• PROTO ALKALOIDS These are simple amines in which
  the nitrogen is not in heterocyclic ring. Some
  times these are considered as biological amines.
  These are basic in nature prepared in plants
  from amino acids e.g. Colchicine, Ephedrine

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• PSEUDO ALKALOIDS These includes mainly
  steroidal, terpenoid alkaloids purines. These
  are not derived from amino acids.
• These do not show many of the typical characters
  of alkaloids but give the standard qualitative
  tests for alkaloids
• e.g. caffeine

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PHYSICAL PROPERTIES

• With few exceptions, all the alkaloids are
  colourless, crystalline solids with a sharp
  melting point.
• Some of the alkaloids are amorphous gums, while
  other are liquid volatile in nature.
• Some alkaloids are coloured in nature e.g.
  berberine is yellow.
• Free bases of alkaloids are soluble in organic,
  non-polar, immiscible solvents.
• The salts of most bases are soluble in water.

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• Free bases are insoluble in water.
• The alkaloids containing quarternary bases are
  only water soluble.
• Some of pseudoalkaloids protoalkaloids show
  higher solubility in water e.g. caffeine is
  freely soluble in water.

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CHEMICAL PROPERTIES

• Most of the alkaloids are basic in reaction, due
  to the availability of lone pair of electrons on
  nitrogen.
• The basic character of the alkaloid is enhanced
  if the adjacent functional groups are electron
  releasing.
• The alkaloid turns to be neutral or acidic when
  the adjacent functional groups are electron
  withdrawing like amide group which reduces the
  availability of the lone pair of electrons.

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• Alkaloids exhibiting basic character are very
  much sensitive to decomposition cause a problem
  during storage their salt formation.
• The alkaloids may contain one or more no. of
  nitrogen. It may exist in the form as
• Primary amine (R-NH2) e.g. mescaline
• Secondary amine (R2-NH) e.g. ephedrine
• Tertiary (R3-N) e.g.atropine
• Quartanary ammonium compounds e.g.
  tubocurarine hydrochloride

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CHEMICAL TESTS FOR ALKALOIDS

• MAYERS REAGENT
• (pot. mercuric iodide solution)
• DREGENDORFFS REAGENT
• (pot. bismuth iodide solution)
• WAGNERS REAGENT
• (iodine-pot.iodide solution)
• HAGERS REAGENT (picric acid solution)

• Cream coloured ppt.
• Reddish brown ppt.
• Reddish brown ppt.
• Yellow coloured ppt.

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GENERAL ISOLATION PROCEDURE FOR ALKALOIDS
Ground Plant Material

1. Defat with Hexane
2. Extract with methanol, filter, concentrate

Methanolic Crude Extract

1. Treat with 1 aqueous HCl
2. Partition with diethyl ether

Aqueous-acid phase
Diethyl ether phase Concentrate (neutral
compounds)

1. Alk. with NH4OH
2. Partition with CHCl3

Chloroform extract (primary, secondary
tertiary alkaloids)
Aqueous alkaloids (quarternary Alkaloids)
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ROLE OF ALKALOIDS IN PLANTS

• They are reserve substances with an ability to
  supply nitrogen.
• They might be the defensive mechanisms for plants
  growing in dry regions to protect from grazing
  animals, herbivores insects.
• They might have a possible role as growth
  regulatory factors in the plants.
• These are end products of detoxification
  mechanisms in plants.
• These are present in conjugation with the plant
  acids such as meconic acid hence acting as
  carriers within the plants for transportation of
  such acids.

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PHARMACOLOGICAL ACTIVIES OF ALKALOIDS

• Anticancer e.g. vinca
• Hypotensive e.g. rauwolfia
• Oxytocic e.g. ergot
• Narcotic analgesic e.g. opium
• Anticholinergic e.g. belladona, datura
• Local anasthetic e.g. coca
• Antimalarial e.g. cinchona
• Expectorant e.g. vasaka

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CHEMICAL CLASSIFICATION OF ALKALOIDS

• TRUE ALKALOIDS
• PYRROLE
• PYRROLIDINE
• DERIVATIVES
• e.g. Hygrine, Cocca species

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• Pyrrolizidine Derivatives
• e.g. senecionine, seneciphylline

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• Piperidine pyridine derivativese.g.
  arecoline, lobeline

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• TROPANE DERIVATIVES
• e.g. Atropine, hyoscine, cocaine

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• QUINOLINE
• DERIVATIVES
• e.g. Quinine, quinidine, cinchonine

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• ISOQUINOLINE
• DERIVATIVES
• e.g. Morphine,
• codeine,
• berberine,
• emetine

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• APORPHINE
• (REDUCED
• ISOQUINOLINE-NAPTHALENE)
• DERIVATIVES
• e.g. boldine

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• INDOLE DERIVATIVES
• e.g. ergometrine,
• ergotamine,
• reserpine,
• vincristine,
• vinblastine

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• IMIDAZOLE
• DERIVATIVES
• e.g. Pilocarpine,
• isopilocarpine

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• NORLUPINANE DERIVATIVES
• e.g. Cytisine,
• lupanine

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• PURINE DERIVATIVES
• e.g. Theophylline, caffeine,
• theobromine

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• STEROIDAL
• DERIVATIVES
• e.g. protoveratrine, solanidine

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PSEUDO ALKALOIDS

• DITERPENES
• e.g. Aconitine, aconine, hypoaconitine
• PROTO ALKALOIDS
• ALKYLAMINES
• e.g. Ephedrine,pseudoephedrine, colchicine

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By - Jaspreet Rekhi www.rhombnet.com