Alkaloid is one of the secondary metabolites produced by the plants which helps indirectly in their normal growth, development and reproduction. Alkaloid is defined as naturally occurring organic compounds which is basic in nature and contains one or more Nitrogen atom in their heterocyclic ring. E.g Atropine, Morphine, Quinine etc. Alkaloids are classified into different categories as mentioned below: 1. Based on amino acid precursor used for synthesis: a. True alkaloid: It is synthesized from amino acid precursor and have nitrogen atom in its heterocyclic ring b. Proto alkaloid: It is derived from amino acid precursor but do not contain nitrogen atom in their basic heterocyclic ring. c. Pseudo alkaloid: It is not derived from amino acid precursor but contains heterocyclic nitrogen atom in their ring. 2. Based on chemical nature: a. Indole alkaloid b. Quinoline alkaloid c. Pyridine alkaloid etc...

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D.Pharm 1
st
Year
Pharmacognosy
Subject Teacher: Ms. Pranita Sunar
Chapter IV: Brief outline of occurrence, distribution, isolation, identification tests,
therapeutic activity and pharmaceutical application of alkaloids, terpenoids,
glycosides, volatile oils, tannins and resins.
ALKALOIDS
Introduction
Alkaloids are group of naturally occurring organic compound which are
basic in nature, containing one or more Nitrogen atom in their heterocyclic
ring and possess specific physiological action on human or animal body.
Alkaloids are “Alkali like” means the word alkaloid is derived from the word
Alkali.
The term alkaloid was introduced by a German Pharmacist Carl Friedrich
Wilhelm Meissnerin in 1819. The first alkaloid of opium (morphine) was
isolated by German chemist Friedrich Serturner.
Properties of Alkaloids
1. Some alkaloids are colorless and crystalline solids while some are
amorphous gums and some are liquid and volatile in nature (Coniine
and Nicotine).
2. They are generally insoluble in water but the salt formed on reaction
with acids is usually freely soluble. (Example: atropine sulphate,
morphine hydrochloride).
3. They are freely soluble in ether, chloroform or other organic solvents.

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Occurrence and Distribution of Alkaloids
Plants have been a rich source of alkaloids but some are found in animals
(muscopyridine in muskdeer), fungi (Ergot alkaloids in Claviceps purpurea),
insect (scopolamine in Apis mellifera), and bacteria (pyocyamine in
Pseudomonas aeruginosa), practically alkaloids are also obtained in the
laboratory by chemical synthesis. In the plant kingdom, among the
angiosperms the Leguminosae, Papaveraceae, Ranunculaceae, Rubiaceae,
Solanaceae, and Berberidaceae are outstanding alkaloids yielding plants.
The gymnosperm rarely contains the alkaloids.
On the basis of chemical nature of alkaloids it is divided in three types
A. True alkaloids: They are derived from amino acid precursors and they
share a heterocyclic ring with nitrogen. These alkaloids are highly reactive
substances with biological activity even in low doses. The primary
precursors of true alkaloids are amino acids such as L-ornithine, L-lysine, L-
tryptophan and L-histidine. Examples of true alkaloids include biologically
active alkaloids like cocaine, quinine, dopamine and morphine.
B. Proto/Amino alkaloids: They are compounds, in which the N atom
derived from an amino acid is not a part of the heterocyclic ring. Such kinds
of alkaloid include compounds derived from L-tyrosine and L-tryptophan.
Example- Hordenine, colchicine, ephedrine.
C. Pseudo Alkaloids: They are the compound which contains heterocyclic
Nitrogen atom which does not originate from amino acids precursors.
Examples: Purine alkaloid such as Caffeine, steroidal alkaloid such as
solanidine.
Isolation of Alkaloids
Isolation of alkaloids is performed by following process:
Stas-otto process.
 Initially powdered materials are defatted with non-polar solvents and
moist with water and treated with NH3 (free alkaloids).

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 Then extract is obtain by the mixing of organic solvent (chloroform,
ether) and concentrate it.
 Then dissolved the alkaloid salt and basified with ammonia or
sodium bicarbonate.
 Finally obtained the organic phase free alkaloids and dry them.
Identification Test for alkaloids
1. Mayer’s reagent (Potassium Mercuric Iodide solution):
Take the alkaloid materials → Mix with the Mayer’s reagent → then
obtained cream color ppt.
2. Wagner’s reagent (Solution of Iodine in Potassium Iodide)
Take the alkaloid materials → Mix with the Wagner’s reagent → then
obtained brown or reddish brown ppt.
3. Hager’s reagent (Saturated Solution of Picric Acid)
Take the alkaloid materials → Mix with the Hager’s reagent → then
obtained yellow color ppt.
4. Dragendroff’s reagent (Potassium Bismuth Iodide)
Take the alkaloid materials → Mix with the Dragendroff’s reagent → then
obtained reddish brown ppt.
5. Murexide reagent (Ammonium purpurate)
Take the alkaloid materials → Mix with the murexide reagent → then
obtained purple color ppt.
6. Vitali Morin Test:
2-3ml solution of sample is treated with fuming HNO3, followed by
evaporation to dryness and addition of Methanolic KOH solution to an
acetone solution of nitrated residue. White coloration takes place.

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7. Thalleoquine Test for Quinoline alkaloids:
To the powder drug, when Br2 water and dilute NH2 solution is added. Gives
emerald green colour, indicates the presence of Quinoline alkaloids.
Therapeutic / Pharmaceutical Application of Alkaloids
1. Acts on CNS: Depressant(morphine), Stimulant(caffeine)
2. Local Anaesthetic or Analgesic ( cocaine, morphine)
3. Antitumor : vinblastine
4. Antimalarial: quinine
5. Antibacterial : berberine
6. Antiseptic : scopolamine