1. Alkaloids
Definition: the term “alkaloid” (alkali-like) is commonly used to designate basic
heterocyclic nitrogenous compounds of plant origin that are physiologically active.
2. Deviation from Definition:
• Basicity: Some alkaloids are not basic e.g. Colchicine, Quaternary alkaloids.
• Nitrogen: The nitrogen in some alkaloids is not in a heterocyclic ring e.g.
Ephedrine, Colchicine, Mescaline.
• Plant Origin: Some alkaloids are derived from Bacteria, Fungi, Insects,
Frogs, Animals.
3. Classification:
• True (Typical) alkaloids that are derived from amino acids and have
nitrogen in a heterocyclic ring. e.g Atropine, morphine
• Protoalkaloids that are derived from amino acids and do not have
nitrogen in a heterocyclic ring. e.g Ephedrine
• Pseudo alkaloids that are not derived from amino acids but have
nitrogen in a heterocyclic ring. Purine base (purine nucleotides)
alkaloids. e.g Caffeine
4. Distribution and occurrence:
• Rare in lower plants.
• Dicots are more rich in alkaloids than Monocots.
• Families rich in Alkaloids: Apocynaceae, Rubiaceae, Solanaceae and
Papaveracea.
• Families free from Alkaloids: Rosaceae, Labiatae
5. Distribution in Plant:
• All Parts e.g. Datura.
• Barks e.g. Cinchona
• Seeds e.g. Nux vomica
• Roots e.g. Aconite
• Fruits e.g. Black pepper
• Leaves e.g. Tobacco
• Latex e.g. Opium
6. 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.
7. Nomenclature:
Trivial names should end by "ine". These names may refer
to:
•The genus of the plant, such as Atropine from Atropa
belladona.
•The plant species, such as Cocaine from Erythroxylon
coca.
•The common name of the drug, such as Ergotamine from
ergot.
•The name of the discoverer, such as Pelletierine that was
discovered by Pelletier.
•The physiological action, such as Emetine that acts as
emetic, Morphine acts as narcotic.
•A prominent physical character, such as Hygrine that is
hygroscopic.
8. Extraction, Purification and Isolation of Alkaloids from
Powdered plants
• Extraction and purification
Method I:
The powder is treated with alkalis to liberates the free bases that
can then be extracted with water immiscible organic solvents.
Method II:
The powdered material is extracted with water or aqueous alcohol
containing dilute acid. Alkaloids are extracted as their salts
together with accompanying soluble impurities.
Method III:
The powder is extracted with water soluble organic solvents such as
MeOH or EtOH which are good solvents for both salts and free
bases.
9. Plant material and solvent
Extract
Concentration
Acidified Extract (Alk. as salts)
Organic solvent dissove Impurities
Acidification
Alkalinization
Alkaline aqueous layer
Organic solvent dissove Alkaloids
10. According to basicity Alkaloids are classified into:
•Weak bases e.g. Caffeine
•Strong bases e.g. Atropine
•Amphoteric *
Phenolic Alkaloids e.g. Morphine *Alkaloids with
Carboxylic groups e.g. Narceine
•Neutral alkaloids e.g. Colchicine
11. Classification of Alkaloids
Chemical Classification based on basic chemical Skeleton
A. Non Heterocyclic alkaloids
B. Heterocyclic alkaloids
A. Non Heterocyclic alkaloids
Phenylethylamines
e.g. Ephedrine
CH2 CH CH3
NH2
12. B. Heterocyclic Alkaloids
1. Pyrrole and pyrrolidine
eg. Hygrines
2. Pyrrolizidine
eg. Symphitine
3. Pyridine and piperidine
e.g. lobeline, nicotine
4. Tropane
e.g. Atropine.
N N
H
16. Areca Nuts
Synonyms: Betel nuts, Supari
Biological Source: Areca nuts are the seeds of Areca
catechu.
Family: Palmae
Habitat: The tree is cultivated in tropical India, Sri
Lanka, South China, Philippines and East Africa.
17. Chemical constituents:
- Contain a number of alkaloids of piperidine series
- Arecoline (0.1-0.5%)
- Arecaine (N-methyl guvacine)
- Guvacine
- Arecaidine
- Guvacoline
- Arecolidine
- Choline
Also contain fats and tannin.
19. Uses:
1. Powdered areca is used as anthelmintic and vermifuge
for dogs.
2. It has astringent action.
3. It has aphrodisiac action.
4. Useful in urinary disorders, as nervine tonic and
emmenagogue.
20. Conium
Synonyms: Hemlock or poison hemlock
In ancient Greece, hemlock was used to poison condemned prisoners. Socrates, the
most famous victim of hemlock poisoning, was accused of impiety and corrupting the
minds of the young men of Athens in 399 BC and his trial gave down his death sentence.
He decided to take a potent infusion of hemlock
Biological Source: Herbaceous flowering plant of Conium
maculatum.
Family: Apiaceae
Habitat: Native to Europe and North Africa and Naturalized in
North and South America, Australia and West Asia.
21. Chemical constituents
It contains some piperidine alkaloids
• Coniine,
• N-methyl-coniine,
• Conhydrine,
• Pseudoconhydrine,
• γ-coniceine)
CH3
22. Uses:
Hemlock is a very poisonous plant that has a long history of
medicinal use, though it is very rarely used in modern herbalism.
1. It is a narcotic plant that sedates and relieves pain. The plant
contains coniine, an extremely toxic substance that can also
cause congenital defects.
2. The whole plant is analgesic, antispasmodic, emetic and
sedative.
3. It is a traditional folk treatment for cancer and was formerly
widely used internally in very small doses to treat a variety of
complaints including tumours, epilepsy, whooping cough, rabies
and as an antidote to strychnine poisoning.
4. It is still used externally, usually in ointments and oils, in the
treatment of mastitis, malignant tumours (especially breast
cancer) anal fissure and haemorrhoids.
24. Chemical constituents:
- Contain about 0.5-2.0 % total alkaloids
- Chief alkaloid is ephedrine (30-90%)
- Pseudo ephedrine
- 1-methyl ephedrine
- Nor ephedrine
- Dimethyl ephedrine
25. Uses:
1. Liquid extract of ephedra is used for controlling
asthmatic paroxysms.
2. Tincture of Ephedra is useful as cardiac and circulatory
stimulant.
3. Decoction of stems and roots is a remedy for
rheumatism and syphilis in Russia.
4. Ephedrine is sympathomimetic, has been used to
counteract hypotension associated with anaesthesia, as
a mydriatic, in allergic reactions and as a CNS stimulant,
for the relief of asthma, rhinitis, whooping cough and
hay fever.
5. Ephedrine is also a bronchodilator.
26. Colchicum
Synonyms: Colchicum corm/ Wild Saffron/Meadow Crocus.
Biological Source: Colchicum seeds and corm are obtained
from Colchicum autumnale
Family: Liliaceae
Habitat: Annual herb found in England, Poland,
Czechoslovakia, Yugoslavia, USA and Holland.
Corm
27. Chemical constituents
It contains the alkaloids
• Colchicine (0.3-0.8%)
• Colchicein
• Colchicoresin
• Demecolcine
Starch
Colchicine (R=COCH3)
Demecolchine (R=CH3)
28. Uses:
1. Cochicum corm or colchicum is gout depressant and
used to cure gout and rheumatism.
2. It is prescribed to treat myeloid leukemia.
3. Anticancer activity of colchicum has been also reported.
Toxicology
All parts are highly toxic. It may produce severe gastric
distress, shock, and inhibit normal cell growth.
Its higher doses cause vomiting and diarrhea.
