2. Introduction to Alkaloids
Extremely difficult to define because these do not represent
homogeneous compounds either from, Chemical, biochemical or
physiological view point.
Term alkaloid is derived from, Alk means alkali Oids means like. They
are alkali like compounds therefore they are called Alkaloids.
Alkaloids are nitrogenous organic molecule that has a
pharmacological effect on humans and animals. They are class of
compounds which typically contain nitrogen and have a complex ring
structure.
4. Occurrence of Alkaloids:
Alkaloids occur in, Seeds (Areca), Fruits (Conium), Leaves
(Coca), Underground stem (Sangunaria), Roots (Belldonna),
Rhizomes (Ipecac), Barks (Cinchona) and Fungi (Ergot)
Alkaloids are found as secondary metabolites
in plants(e.g; Vinca & Datura),
animals (e.g; in Shellfish) and fungi,
and can be extracted from their sources by treatment with
acid (HCl, H2SO4, Malic acid, Citric acid, etc)
5. Physical properties:
Alkaloids are usually bitter in taste
Alkaloids are insoluble or sparingly soluble in water; but alkaloidal salts
are freely soluble in water
Free Alkaloids are usually soluble in ether, chloroform and other
relatively non polar solvents.
Most of the alkaloids are crystalline solids while few are amorphous
Some are liquids (usually oxygen free) like Nicotine, Coniine and
serpentine.
Alkaloidal salts are also crystalline in nature
Alkaloids are generally colourless but few are coloured. E.g.
Sanguinarine is red in colour.
6. Role of Alkaloids in Plants:
They have defensive mechanism against pathogenic substances in
plants, they protect plants from insects and herbivores.
End products of detoxification reactions, so are metabolic locking-up
of compounds harmful to plants
They are metabolic waste products.
They also control metabolism in plants.
They regulate growth factors in plants
Act as reserve substances for supplying Nitrogen and other
necessary elements to plants
7. Pharmacological activities of Alkaloids
Analgesics and Narcotics (Morphine, Codeine)
Central NS Stimulants ( Strychnine, Brucine,
Caffeine and Nicotine )
Mydriatics ( Atropine)
Myotics (Physostigmine, Pilocarpine )
Hypertensive ( Ephedrine)
Antihypertensive ( Reserpine)
Anti malarial ( Quinine )
Antiarrhythmic (Quinidine)
Oxytocic agent (Ergotamine)
Antitumor (Vincristine and Vinblastine)
Muscle relaxant (Tubercurarine and Papaverine)
8. Classification of Alkaloids
Alkaloids are generally classified by;
Their molecular precursors, based on the biological pathway used
to construct the molecule.
From Structural point of view, alkaloids are divided according to
their shape and origins.
9. 1. True Alkaloids:
These are derived from Amino acids. They share heterocyclic ring with
Nitrogen. They are highly reactive substances with biological activity
at low doses. Examples: Nicotine, Morphine
They occur in plants,
1. In Free State
2. As salts
3. As N-oxides
Primary precursors of these Alkaloids are amino acids, like L-ornithin,
L-lysine, L-phenylalanine, L-tyrosine, L-tryptophan, and L-histidine
10. 2-Proto alkaloids:They are derived from Amino acids. The N-atom derived from an amino
acid is not a part of the heterocyclic ring. They are structurally simple
alkaloids. Examples: Colchicine
These are derived from L-tyrosine and L-tryptophan
11. 3-Pseudo alkaloids:
The basic carbon skeletons of which are not derived from amino
acids. In reality, pseudoalkaloids are connected with amino acid
pathways. They are derived from the precursors or post-cursors
(derivatives the indegradation process) of amino acids. They can
also result from the amination and trans-amination reactions of
the different pathways connected with precursors or post-cursors
of amino acids
Example: Aconitine and Caffeine
12. BIOSYNTHESIS OF ALKALOIDS :
• It is well established that alkaloids are derived from Amino acid.
• The most common ones are: phenylalanine, tyrosine, lysine,
ornithine, histidine, tryptophan and anthranilic acid.
13. Extraction of alkaloids
Method A: (for alkaloidal salts)
The powdered material that contains alkaloidal salts is
moistened with alkaline substances like sodium bicarbonate,
ammonia, calcium hydroxide etc. which combines with acids,
tannins, and other phenolic substances and sets free the
alkaloidal bases.
Extraction is then carried out with organic solvent such as
ether or petroleum spirit. The concentrated organic liquid is
then shaken with aqueous acid and allowed to separate.
Alkaloid salts will be present in aqueous liquid, while many
impurities remain behind in the organic liquid.
14. Method B: (for alkaloidal base)
The collected powdered material is extracted with water or
aqueous alcohol containing dilute acid. Chloroform or other
organic solvents are added and shaken to remove the pigments
and other unwanted materials.
The free alkaloids are the precipitated by the addition of
excess alkalis like sodium bicarbonates, or ammonia and
separated by filtration or by extraction with organic solvents.
15. •Volatile liquid alkaloids (nicotine & coniine) are
isolated by distillation. The powdered material that
contains alkaloids is extracted with water and the
aqueous extract is made alkaline with sodium
carbonate or ammonia and alkaloidal base is
distilled off in steam this could be collected and
purified.
18. 1. Pyridine-piperidine alkaloids:
(i) Areca nuts
Synonyms: Betal nuts; Supari (Hindi)
Botanical origin: Areca catechu
Family: Palmaceae
Part used: Areca nut (Seeds) obtained from
fruit.
Habitat:
The tree is cultivated in tropical India, Sri Lanka, South China, Africa,
Bengal and Assam.
19. Constituents:
It contains alkaloids like Arecoline, arecaidene, guvacine,
guvacoline, Fats (14%),Tannin (15%), Lipids,Volatile oils and
Gums .
Medicinal uses:
Powdered Areca is used as anthelmintic, taenifuge and
vermifuge for dogs.
Useful in urinary disorders, as nervine tonic and
emmenagogue.
The chewing of Areca nut may cause mouth cancer.
20. Cultivation and Collection
Areca palm is mostly propagated by seeds. It grows in areas with
heavy rainfall in between temperature of 15–38°C. It is cultivated in
plains, hill slopes and low lying valleys. The seeds are collected from
25–50 years old trees.
Each tree contains about 100 fruits per year which are detached by
means of bamboo poles and the seeds extracted. The pericarp is
fibrous and surrounds a single seed which is easily separated. The
seeds are usually boiled in water with the addition of a little lime and
dried.
21. (ii) Lobelia
Synonyms: Herba lobellae, Indian tobacco, Asthma Weed.
Botanical origin: Lobelia inflata
Family: Lobeliaceae
Part used: Dried leaves and Aerial tops
Habitat: Central United States, Canada and India.
Constituents:
14 different alkaloids have been identified. Major and most important
constituent is lobeline .Other alkaloids are lobelidine, lobelanidine,
lobelanine
Gum, resin, chlorophyll, fixed oil, lignin
Lobeline
22. Cultivation and Collection
Drug is obtained both from cultivated and wild plants. It is
propagated using seeds. For cultivation seeds are sown in rich,
moist soil usually in March to April.
After sowing, seeds are covered with soil and pressure is
applied on them by placing wooden board over them and
walking on it.
Collection is done in August to September when capsular fruits
get inflated. Aerial parts are collected and dried in the shade to
maintain green colour.
23. Medicinal uses:
Mainly used as expectorant, diaphoretic, antiasthmatic
Lobeline is a respiratory stimulant.
The oil of Lobelia is valuable in tetanus.
It is included in some antismoking preparations.
An injection of lobeline hydrochloride is used in the resuscitation of
new-born infants.
In toxic doses the drug has a paralytic effect.
24. 2. Tropane alkaloids:
(i) Belladonna
Synonyms: Belladonna herb; Belladonna leaf;
Deadly night shade leaves; Poison
black cherry
Botanical origin: Atropa belladonna
Family: Solanaceae
Part used: Dried leaves and flowering tops
Habitat:
United States, Canada, UK, Germany and India.
26. Cultivation and Collection:
Seedlings are transplanted in April to moist, calcareous and
loamy soil. During flowering session leaves and flowering tops
are cut at least three times in a year at an interval of two
months from one to three years old plants.
When the plant is four years old, roots are dug out. The
collected drug is dried at 40–50°C. Un-dried leaves deteriorate
and give off ammonia.
Sometimes the leaves are damaged by flea-bettle insect and the
roots by a fungus.
27. Medicinal uses:
In the treatment of the combination therapy of peptic ulcer,
functional digestive disorders including spastic, mucus & ulcerative
colitis.
Due to anticholinergic properties, it is used to control excess motor
activity of GIT and spasm of urinary track.
Anticholinergic, narcotic, sedative, diuretic mydriatic and used as
anodyne
28. (ii) Hyoscyamus
Common Name: Henbane
Botanical origin: Hyoscyamus niger
Family: Solanaceae
Part used: Dried leaves and flowering tops
Habit: Biennial herb
Habitat:
It is found throughout Central and Southern Europe and in Western Asia,
extending to India and Siberia. As a weed of cultivation it now grows also
in North America and Brazil. Apart from these countries, it grows in
Scotland, England
29. Constituents:
• Hyoscyamine, Atropine
hyocine (scopolamine),
mucilage, albumin
and calcium oxalate crystals.
Medicinal uses:
• - It is used as Antispasmodic.
• - It is used as mild Diuretic.
• - It is used as Hypnotic and narcotic medicine
30. (iii) Stramonium
Common Name: Commonly called Jimson Weed
and Devil’s apple
Botanical origin: Datura stramonium
Family: Solanaceae
Part used: Dried leaves and flowering tops
Habitat: Indigenous to Europe, Asia & Africa. Cultivated in England
Germany and Belgium.
31. Constituents:
Hyoscyamine, Atropine, Hyocine (scopolamine).
Other constituents there is proteins i.e. albumin, 6-hydroxy
Hyoscyamine, acetyl derivatives of caffeic acid, feurlic acid and para
coumaric acid.
Medicinal uses:
It is used as antispasmodic.
It is used as anodyne.
It is used as narcotic.
It is used to treat the spasm of bronchioles in asthma.
It is used to treat Parkinsonism, boils, sores and fish bite.
32. 3. Quinoline Alkaloids:
Cinchona
Common name: Cinchona bark
Botanical origin: Cinchona succirubra,
Cinchona officinalis
Family: Rubiaceae
Part used: Dried bark of stem and roots
Habitat: Cinchona is a native of South America, occurring wild there.
At present, it is mainly cultivated in Indonesia (Java), Zaire and India
33. Constituents:
Cinchonidine, cinchonine,quinine, quinidine also consist of
bitter glycoside, starch grains, calcium oxalate crystals and
crystalline acid like quinic acid
Medicinal uses:
as antimalarial drug, analgesic, antipyretic, protoplasmic, bitter
stomachic and tonic.
Quinidine is cardiac depressant and
Cinchonidine is used in rheumatism and neuralgia.
34. 4. Isoquinoline Alkaloids:
(i) Ipecac
Botanical origin:
Cephaelis ipecacuanha,
Cephaelis acuminata
Family: Rubiaceae
Part used: Dried Roots and Rhizomes
Habitat:
It is mainly cultivated in Brazil, Malaysia and India.
35. Constituents:
It contain isoquinoline alkaloids. The major alkaloids are emetine,
cephaeline and psychotrine.
Medicinal uses:
It is used as emetic. Ipecac syrup is available in market which is used for
this purpose.
Expectorant
Amoebic dysentry
36. (ii)Opium
Common name: Post, Afim
Botanical origin: Papaver somniferum
Family: Papveraceae
Part used: Dried milky latex obtained by the incision of fully
grown but unripe capsules.
Habitat: It is mainly found in Turkey, Russia, Yugoslavia,
Tasmania, India, Pakistan, Iran, Thailand, Afghanistan, China
and Burma,
37. Cultivation and Collection:
It is cultivated in October with selective seeds. After growth of about
2cm to 3cm plant out, winter season starts at that time growth
retarded. In spring season, it grows little. When seedlings are of
12cm to 14cm, thinning of seeds are done. Flowers occur in June and
July. Purple white or yellow flower and poppy start growing on each
plant.
When capsule start maturing from purple to yellow the constituents
are at its peak. Cuts are applied so that endocarp don’t get damage.
Latex oozes out, initially it is white but on exposure to sun and it
turns brown.
Latex is converted into kneaded into small box and packed in opium
leaves and is shade dried and these balls are crude opium.
39. Medicinal uses:
Opium and morphine have narcotic, analgesic and sedative
action and used to relieve pain, diarrhoea dysentery, cough and
cause drug addiction.
Poppy capsules are astringent, somniferous, soporific, sedative
and narcotic and used as anodyne and emollient.
Codeine is mild sedative and is employed in cough mixtures.
Noscapine is not narcotic and has cough suppressant action
acting as a central antitussive drug.
Papaverine has smooth muscle relaxant action and is used to
cure muscle spasms.
40. 5. Indol Alkaloids:
(i) Rauwolfia
Common name: Snake root, Chootachand
Botanical origin: Rauwolfia serpentina
Family: Apocynaceae
Part used: Dried roots but sometimes rhizomes and stem cuttings are
also used.
Habitat:
It is found in India, Burma, Sri-Lanka, Vietnam, Malaysia, Indonesia
and Thiland.
41. Constituents:
The genus was named on the name of discovers Dr. Leonard Rauwot,
while serpentina means tapering ends. Reserpine, serpentine,
resepinine, ajmaline, and isoajmaline.
Medicinal uses:
Used as hypotensive sedative agent. Especially, reserpine is
antihypertensive agent. It slows down the pulse rate and produce
euphoria.
Used to treat cardiac arrhythmia.
Used as hypnotic agent.
Used to treat neuro-psychotic disorders.
42. (ii) Catharanthus
Botanical origin: Catharanthus roseus
Family: Apocynaceae
Part used: Dried whole plant parts
Habitat: It is cultivated as ornamental plant cell over the world in tropical
areas.
Constituents: It contain indol-indolene alkaloids in it. The major alkaloids
are vinblastine, vincristine, venerosine and extra. Vincristine and
vinblastine are unstable and need refrigeration 0℃ – 8℃
43. Medicinal uses:
Vinblastin is an antitumour alkaloid used in the treatment of
Hodgkin’s disease.
Vincristine is a cytotoxic compound and used to treat leukaemia in
children.
Vinca is used in herbal practice for its astringent and tonic properties
In cases of scurvy and for relaxed sore throat and inflamed tonsils
Also used in constipation
For bleeding piles.
44. (iv) Physostigma
Botanical origin: Physostigma venenosum
Family: Leguminosae
Part used: Dried Ripe seeds
Habitat: It is found in West Africa and india
Constituents:
It contain alkaloids. The total alkaloidal content is 0.15%. The major
alkaloids are physostigmine (serine), physovenine and esramine
45. Medicinal uses:
They are used as a reversible inhibitors of choline esterase.
0.25% ointment of physostigmine is used topically on conjunctiva 3
to 4 times a day.
Physostigmine potentiated the effects of Acetyl choline.
It is used as antidote for anticholinergic inhibitors.
46. (v) Ergot
Botanical origin: Cleviceps purpurea
Family: Clavicipitaceae
Part used: Dried sclerotium developed on rye
plant
Habitat: It is mainly found in Hungary, Switzerland, Germany, France,
Spain, Russia and India.
Collection: The ergot is formed by the fungus Cleviceps purpurea .
47. Asexual stage:
In spring season one of the fungal spore come in contact with rye plant.
It resides over the ovary. Hyphal strands are produced which penetrate
into the ovary for nutrition. Fungus is parasitic in nature. Hyphal strands
will eventually from a soft white mass called mycelium. Some of the
hyphal strands in mycelium will produce asexual spore called
conidiospores.
These conidiospores will be suspended in honey dew (a secretary
secretion of mycelium). Insects will be attracted to honey dew.
Conidiospore than will be carried to another host plant through the
insect to repeat the cycle. This stage of development is called asexual or
Sphacelial stage.
48. Sexual stage:
In this stage of development the mycelium grown in size and eventually
replace entire ovary to form soft white color mass which over the time
will become hard and purple in color to form Seclerotia. These seclerotia
will fall down on ground over the winter season.
In the start of spring season sexual spores will be produced in
seclerotium and will repeat the entire cycle. This stage of development
is called sexual or Ascigerous cycle.
49. Medicinal uses:
Ergot is oxytocic, vasoconstrictor and abortifacient and used to assist
delivery and to reduce post-partum haemorrhage.
Ergometrine is oxytocic and used in delivery
Ergotamine (dihydroergotamine) salts are used as specific analgesics
for the treatment of migraine.
50. 6. Imidazole Alkaloids:
(i) Pilocarpus
Common name: Jaborandi
Botanical origin: Pilocarpus jaborandi
Family: Rutaceae
Part used: Dried leaflets
Habitat: It is indigenous to Brazil and America.
Constituents: Isopilocarpine, pilocarpidine, pilosine,
pseudopilocarpine and isopilosine.
The range of total alkaloids in different species is between
0.5% and 1%.
51. Medicinal uses:
Pilocarpine is antagonistic to atropine, stimulating the nerve endings
paralysed by that drug, and contracting the pupil of the eye.
It induces also free salivation and excites most gland secretions, some
regarding it as a galactagogue.
In the treatment of glaucoma.
52. 7. Steroidal Alkaloids:
(i) Veratrum
Common name: American hellebore, European hellebore
Botanical origin: Veratrum viride,Veratrum album
Family: Liliaceae
Part used: Dried rhizomes
and roots
53. Constituents:
Basic ring is present in such alkaloids is perhydrocyclopentano
phenantherine ring. Other alkaloids are Cevadine, Germidine,
Veratrine, pseudojervine, veratrosine, Germine, rubijervine and
jervine and Protoveratrine A & B.
Medicinal uses:
Veratrum is used as antihypertensive, cardiac depressant, sedative
and insecticides.
lowers the blood pressure without effecting heart rate.
It is also used for relief in irritationof the nervous system, in
convulsions, mania, neuralgia, headache, febrile and inflammatory
affections of the respiratory organs and acute tonsillitis.
54. 8. Alkaloidal amines:
These alkaloids do not possess nitrogen containing heterocyclic ring.
The nitrogen atom is present outside the ring. They do not possess
alkaloidal properties but they gives positives tests with basic reagents
i.e. Hager’s reagent, Wagner’s reagent etc.
The class includes Ephedra and colchicum. These are simple amines or
their derivatives. They are biosynthesized by the phenyl alanine and
tyrosine.
55. 8.Alkaloidal amines:
(i) Colchicum
Botanical origin: Colchicum luteum,
Colchicum autumnale
Family: Liliaceae
Part used: Dried ripe seeds and corms
Habitat: It is indigenous and cultivated in England, USA, and Africa. In
USA it is cultivated as ornamental plant.
56. Constituents:
Major alkaloid is colchicine, it is present about 0.5% in seeds and 0.6% in
corms.
They also contain resin, called colchicoresin, fixed oil, glucose and starch.
Uses:
Both the corm and the seeds are analgesic, ant rheumatic, cathartic,
diuretic, leukaemia and emetic.
It should not be prescribed for pregnant women or patients with kidney
disease.
57. (ii) Ephedra
Botanical origin:
Ephedra sinica
Family: Ephadreaceae
Part used: Whole herb
Habitat: It is mainly found in China, India, Nepal, Turkey, Pakistan .
Constituents:
It contain Ephedrine, Pseudoephedrine, Norpseudoephedrine,
tannins, saponin, flavone and volatile oils.
58. Uses:
Ephedrine is antiallergenic, antiasthmatic, antispasmodic, decongestant,
cough suppressant, stimulant and vasoconstrictor
As a whole it is decongestant; it opens sinuses, increases sweating,
dilates bronchioles (antiasthmatic use), diuretic, CNS stimulant, raises
blood pressure, alleviates aches and rheumatism, alleviates hay
fever/colds, etc
59. 9. Purine bases:
Purine ring is formed of two rings.
1) Pyrimidine ring 2) Imidazole ring
(i) Coffee
Botanical origin: Coffea arabica
Family: Rubiaceae
Part used: Dried roasted seeds/ beans
Habitat: It is indigenous to Ethiopia, Brazil, India, Vietnam, Mexico,
Indonesia and Sri Lanka.
60. Constituents:
Tea contain xanthine derivatives. Caffeine (1, 3, 7-trimethyl
xanthine), theophylline (1, 3-dimethyl xanthine), tannins
(gallotannic acid), Theobromine (1, 7-dimethyl xanthine),
proteins and volatile oils. Aroma is due to volatile oil.
61. Uses:
The usual cup of tea contain 60mg of caffeine in it.
CNS stimulant.
as stimulent of cardiac and respiratory center.
acts on smooth muscles and kidneys.
astringent due to tannins.
Theophylline is smooth muscle relaxant.
Theophylline is used as bronchodilator in asthma.
Theophylline is used as diuretic in cardiac patients.
Theobromine is also used as smooth muscle relaxant and diuretic but it
is preferred over theophylline because it doesn’t act of CNS system as
theophylline.
