•The alkaloids are defined as ‘basic nitrogenous plant products, mostly
optically active and possessing nitrogen heterocyclic as their structural unit,
with a pronounced physiological action.
•The term alkaloid was coined by W. Meissner, a Germon Pharmacist.
The first alkaloid to be synthesised was Coniine in1886.It was isolated in
•These are organic product of natural and synthetic origin which are basic
in nature and contain one or more nitrogen atom, normally of heterocyclic
nature and posses specific pharmacological action on human or animal
•The true alkaloids are toxic in nature.contain hetrocyclic nitrogen which is
derided from amino acids and always basic in nature.
A.Protoalkaloids:simple amine, nitrogen is absent in ring/biological
amines.ex Mescaline, ephedrine , colchicine
:includes steroids and terpenoids alkaloids, not derived from amino acids.
They donot shows typical charaters of alkaloids by give posative test for
2. Physical Properties
• Colorless, crystalline solids
• Sharp melting points
• Some are amorphous gum
• Some are colored Betanidin is red, Berberine is yellow
• Soluble in organic nonpolor solvents, immiscible solvents
• Salt are soluble in water.
• Chemical nature: Basic in nature due to presence of nitrogen or
avilability of lone pair of electron on N.
5. • Alkaloids
• All the extracts were evaporated separately then the acidic solution
of extracts was prepared by dissolving it in hydrochloric acid & was
then filtered. These extract solutions were then used for different
tests which are as follows:
• a) Dragendorff’s test- 2-3ml of extract solution + few drops of
Dragendorff’s reagent (positive test shows orange brown colored
• b) Mayer’s test- 2-3ml of extract solution + few drops of Mayer’s
reagent (positive test shows cream colored precipitate)
• c) Hager’s test- 2-3ml of extract solution + few drops of Hager’s
reagent (positive test shows yellow colored precipitate)
• d) Wagner’s test- 2-3ml of extract solution + few drops of Wagner’s
reagent (positive test shows reddish brown colored precipitate)
6. Classification of alkaloids on the basis of their
chemical nature is as follows:
• Phenylalkaylamine ( Epherine, Pseudoephedrine, Taxine,
• Pyrrolidines, Piperidines andpyridines
• Tropane alkaloids (Hyoscamine, atropine and hyscine)
• Quinoline alkaloids of Cinchona
• Indole alkaloids (Apocyanaceae, Rubiaceae and Loganiaceae)
• Purine alkaloids (Caffeine, Threobromine, methylated derivatives of
• Tropolone alkaids (Colchicines)
• Isoprenoid alkaloids
• Diterpenoid alkaloids
7. • In the recent past, the alkaloids have been divided
into two major categories based on the analogy that one
containing a non-heterocyclic nucleus, while the other
having theheterocyclic nucleus. These two classes of
alkaloids shall be discussed briefly as under.
• (a) Non-heterocyclic Alkaloids A few
typical alkaloids having non-heterocyclic nucleus are
• Obtained from Atropa bellodona, Datura stramonium, D.
• Generally it is obtained from l-hyosyamine.
• Optically inactive
• Atropine is racemic mixture of Hyosyamine.
• Molecular formula .
• It is mixture of Tropic acid and Tropine.
14. Pharmacological action
• CVS: cause Tachycardia due to blockge of vaginal
impulse to the SA Node, donot have any marked effect
• Eyes: cause Mydriasis, blurring of vission, intraoccular
• Smooth Muscles: relaxed intestinal and stomach
muscles, also relaxed uterine muscles. Produce
• Glands: Decrease sweat, salivary lachrymal secretion.
• Body Temp: Increases at high dose due to inhibition of
sweating and stimulation of temp regulating centers.
15. Therapeutic Uses
• Stimulate vagal vasomotor, respiratory center. Used in
• Scopolamine and Atropine is effective in treatment of
nausea and vomiting or motion scikness.
• Due to their anticholinergic action used in Parkisonium
• Antispasmodic: relax the smooth muscles of intestine,
urinary bilary tract.
• Antisecretory activity: reduce gastric secretion in
• Used as Preanesthetic medication.
• Obtained from Rauwlfia serpentina.
• Methyl ester of Pentacyclic reserpic acid and
is linked through –OH group at position 18 by
ester linkage through Trimethoxy Benzoic
18. Mode of action
• It produce hypotension due to depression of
hypothalamus and induce peripheral depletion of
• Reserpine interfere synthesis of noradrenaline because
it block the uptake of dopamine into the vesicle and this
release stored noradrenaline.
19. Therapeutic Uses
• In Psychotic disorders
• Anxiety, Tention
• In hypertension, it lower the systolic and diostolic B.P.
and cause Bradycardia.
• Obtained from stem of Ephedra
• Fam: Gentiaceae
• It is white, roasted or needle like crystals
soluble in water, chloroform and alcohol.
• Bitter in taste, colorless
21. Mode of action
• Ephedrine is sympathomimetic drug which mimic the
effect of sympathetic nervous stimulation of organ and
structure that contain the adrenergic receptor (alpha and
• Ephedrine is more stable than adrenaline and it cross
blood brain barrier and powerful stimulant effect on CNS.
• Action is slow and long duration.
• Cause stimulation of alpha and beta receptor directly
and release noradrenaline from postganglionic
22. Pharmacological action.
• CVS:Raise the systolic and diostolic B.P. and increase
the cardic output
• CNS: cause stimulation
• Smooth Muscles: retardation of bronchial and uterine
muscle and cause dilation of pupil of eye and increase
the basic metabolic rate.
• In Asthma [Brnchiodialator].
• In allergic condition
• In Hay fever
• Hypotention of arteoles
• Hypnotic action