The document discusses secondary plant metabolites called alkaloids. It begins by defining alkaloids as basic, nitrogen-containing organic compounds found in plants and some other organisms. The document then covers classification of alkaloids based on their origin, plant source, pharmacological effects and chemical structure. Various alkaloid groups are described along with examples. Physical properties and exceptions are outlined. Detection tests for alkaloids include Mayer's, Dragendorff's, Wagner's and Hager's tests. The functions of alkaloids in plants include protection against herbivores and insects as well as roles in growth regulation and nutrient storage.

1. Dr Payal Rahul Dande
SVKM’s NMIMS
School of Pharmacy & Technology Management
Shirpur Campus
Introduction to Secondary Metabolites
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2. Contents
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Definition, classification, properties and test for identification of
• Alkaloids
• Glycosides,
• Flavonoids,
• Tannins,
• Volatile oil and
• Resins

3. Alkaloids-Introduction
• Definition- Alkaloids are organic products of natural origin, basic in
nature, containing one or more ‘Nitrogen’ atom in heterocyclic ring
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4. Alkaloids
Deviation from Definition
• Definition- Alkaloids are organic products of natural origin, basic in
nature, containing one or more ‘Nitrogen’ atom in heterocyclic ring
• Deviation from Definition
1. Basicity: Some alkaloids are not basic e.g. Colchicine, Piperine
2. Nitrogen: The nitrogen in some alkaloids is not in a heterocyclic
ring e.g. Ephedrine, Colchicine, Mescaline.
3. Plant Origin: Some alkaloids are derived from Bacteria, Fungi,
Insects, Frogs, Animals. Eg. Muskopyridine, Ergotamine
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5. Occurrence and Distribution
• Higher Plants: Alkaloids are distributed in Higher plants: Nearly 34 orders contain
alkaloids, some orders are-Rosales, Rubiales
• In angiosperms (flowering plants): Leguminosae, Papaveraceae, Solanaceae,
Rubiaceae, Liliaceae Apocyanaceae, etc. are some of the families containing
alkaloids .
• Also present in microorganisms, marines organisms, insects, animals and some
lower plants (Shrubs and bushes)
• Alkaloids from animal kingdom eg. Muscopyridine- from Musk Deer
• 47% species of bacteria contains alkaloids. e.g. Pyocyanine from Pseudomonas
aeruginosa
• Lower Plants:
• Ergot Fungus: Peptide alkaloids such as Ergometrine, Ergotamine,
• Lycopodium: a Club Moss (Small Green Seedless plant, growing on ground)
contain Lycopodine.
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6. Distribution in Plant:
• All Parts e.g. Datura
• Barks e.g. Cinchona
• Seeds e.g. Nux vomica
• Roots e.g. Aconite, Rauwolfia
• Fruits e.g. Black pepper
• Leaves e.g. Tobacco, Cocoa, belladonna
• Latex e.g. Opium
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7. Classification: based on Definition
• True (Typical) alkaloids that are derived from amino acids
and have nitrogen in a heterocyclic ring. e.g. Atropine
• Protoalkaloids that are derived from amino acids and do
not have nitrogen in a heterocyclic ring.(six membered ring
of five carbons and one nitrogen atom) e.g. Ephedrine
• Pseudo alkaloids that are not derived from amino acids but
have nitrogen in a heterocyclic ring. e.g. steroidal and
terpenoidal alkaloids and purines e.g Caffeine
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8. Classification of Alkaloids
1. Biogenetic/Biosynthetic: Based on the biogenetic/biosynthetic
pathway that form the alkaloids.
2. Taxonomic: According to the plant source of alkaloids.
3. Pharmacological: Based on its pharmacological activity
4. Basic Chemical Skeleton: Chemical structure of alkaloids
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9. Biosynthetic Classification
 The precursor from which the alkaloids are produced in the plant
biosynthetically.
 It is quite convenient and also logical to group together all alkaloids having
been derived from the same precursor but possessing different taxonomic
distribution and pharmacological activities.
(i) Indole alkaloids derived from tryptophan.
(ii) Piperidine alkaloids derived from lysine.
(iii) Pyrrolidine alkaloids derived from ornithine.
(iv) Phenylethylamine alkaloids derived from tyrosine.
(v) Imidazole alkaloids derived from histidine.
(vi) Amino alkaloids derived from Phenylalanine.
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10. Biosynthetic Classification
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Sr No. Biosynthetic
precursor
Alkaloid group Example
1 Tryptophan Indole
Quinoline
Ergotamine, Vincristine, vinblastine, Reserpine
Quinine, quinidine, cinchonine
2 Lysine Piperidine &pyridine
Quinazolidine
Coniine, Lobeline
Lupinine
3 Ornithine Pyrrolidine
Tropane
Hygrine, Nicotine
Atropine, Hyoscyamine
4 Tyrosine Phenylethylamine
Isoquinoline
Amino
Mescaline
Morphine
Colchicine
5 Histidine Imidazole Pilocarpine
6 Phenylalanine Amino Ephedrine

11. (b)Taxonomic Classification: This particular classification essentially deals
with the ‘Taxon’ i.e., the taxonomic category.
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• A few typical examples of plant families and the various species
associated with them are stated below, namely:
(i) Cannabinaceae: are k/as Cannabinaceous Alkaloids: e.g., Cannabis
sativa Linn.,
(ii) Rubiaceae: are k/as Rubiaceous Alkaloids: e.g., Cinchona
Sp., Mitragyna speciosa , Pausinystalia johimbe
(iii) Solanaceae: are k/as Solanaceous Alkaloids: e.g., Atropa
belladonna,Capsicum annum, Datura candida,Datura metel
• Invariably, they are grouped together according to the name of
the genus wherein they belong to.

12. (c) Pharmacological Classification
• Interestingly, the alkaloids exhibit a broad range of very specific
pharmacological characteristics.
• This can also be used as a strong basis for the general classification of the
wide-spectrum of alkaloids derived from the plant kingdom,
• Such as: Analgesics, cardio-vascular drugs, CNS-stimulants and depressants,
mydriatics, anticholinergics, sympathomimetics, antimalarials, purgatives,
and the like.
• However, such classification is not quite common and broadly known.
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14. (d) Chemical Classification
• It is probably the most widely accepted and common mode
of classification of alkaloids for which the main criterion
is the presence of the basic heterocyclic nucleus (i.e.,
the chemical entity).
A. 11 types true alkaloids
B. 1 class of proto alkaloids
C. And three of psuedoalkaloids
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16. 11 Phenanthrene Eg. Morphine, thebaine
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Lupanine

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18. Function in Plants
• They may act as protective against insects and herbivores
due to their bitterness and toxicity.
• They are, in certain cases, the final products of
detoxification (waste products).
• Source of nitrogen in case of nitrogen deficiency.
• They, sometimes, act as growth regulators in certain
metabolic systems.
• They may be utilized as a source of energy in case of
deficiency in carbon dioxide assimilation.
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19. Detection of alkaloids
• Mayer’s test: Alkaloids give cream color precipitate with potassium
mercuric iodide solution.
• Dragendorff’s test: Alkaloids gives reddish brown precipitate with
potassium bismuth iodide solution.
• Wagner’s test: Alkaloids give reddish brown precipitate with Iodine-
potassium iodide solution.
• Hager’s test: Alkaloids give yellow precipitate with picric acid
solution.
• Tannic acid: Alkaloids give buff color with tannic acid solution
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Physical & Chemical
Properties of alkaloids

21. Physical Properties of alkaloids
• Alkaloids are colourless, crystalline, non volatile and bitter
solids
• Most of them are optically inactive and if active they are
generally laevo-rotatory.
• Both alkaloidal bases and their salts are soluble in alcohol.
• Generally, the bases are soluble in organic solvents and
insoluble in water
• Salts are usually soluble in water and, insoluble or sparingly
soluble in organic solvents.
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22. Exceptions to Physical Properties:
I- Condition:
• Most alkaloids are crystalline solids.
• Few alkaloids are amorphous solids e.g. Emetine.
• Some are liquids that are either:
Volatile e.g. nicotine and coniine, or
Non-volatile e.g. pilocarpine and hyoscine.
II- Color:
The majority of alkaloids are colorless but some are colored
• Colchicine and berberine are yellow.
• Canadine is orange.
• The salts of sanguinarine are copper-red.
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23. III- Solubility:
• Generally, the bases are soluble in organic solvents and insoluble in water
Exceptions:
• Bases insoluble or sparingly soluble in certain organic solvents: morphine in
ether, theobromine and theophylline in benzene.
• Bases soluble in water: caffeine, ephedrine, codeine, colchicine, pilocarpine and
quaternary ammonium bases.
Salts are usually soluble in water and, insoluble or sparingly soluble in organic
solvents.
Exceptions:
• Salts insoluble in water: quinine monosulphate.
• Salts soluble in organic solvents: lobeline and apoatropine hydrochlorides are
soluble in chloroform.
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Exceptions to Physical Properties:

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27. Thank you
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