2. The term “alkaloid” (alkali-like) is commonly used to
designate basic heterocyclic nitrogenous compounds of plant
origin that are physiologically active and generally possessing
a marked physiological action on man or animals even in small
The nitrogen is usually contained in a heterocyclic ring system
and it mainly derived from amino acids
There are three main types of alkaloids:
(1) True alkaloids
(2) protoalkaloids and
True alkaloids and protoalkaloids are derived from
whereas pseudoalkaloids are not derived from these
5. True alkaloids derive from amino acid and they share a
heterocyclic ring with nitrogen.
These alkaloids are highly reactive substances with biological
activity even in low doses.
All true alkaloids have a bitter taste and appear as a white solid,
with the exception of nicotine which has a brown liquid.
True alkaloids form water-soluble salts.
Moreover, most of them are well-defined crystalline substances
which unite with acids to form salts.
True alkaloids may occur in plants (1) in the free state (2) as
salts and (3) as N-oxides. Examples of true alkaloids include
such biologically active alkaloids as cocaine, quinine, dopamine
6. Protoalkaloids or Biological amines
Protoalkaloids are compounds, in which the N atom derived from an amino acid
is not a part of the heterocyclic ring system. Nitrogen is present in side chain eg
Ephedrine, mescaline and yohimbine
Such kinds of alkaloid include compounds derived from L-tyrosine and L-
Pseudoalkaloids are compounds, the basic carbon skeletons of which are not
derived from amino acids.
These are not derived from amino acids but have nitrogen in a heterocyclic ring.
These alkaloids can also be derived from nonamino acid precursors. The N atom
is inserted into the molecule at a relatively late stage, for example, in the case of
steroidal or terpenoid skeletons.
Examples of pseudoalkaloids include such compounds as caffeine and theobromine,
7. QUALITATIVE CHEMICAL TESTS FOR ALKALOIDS
General tests answered by all alkaloids are as follows:
Drug solution + Dragendroff’s reagent (Potassium Bismuth Iodide),
formation of Orange red colour
Drug solution + few drops of Mayer’s reagent (potassium mercuric iodide),
formation of creamy-white precipitate
Drug solution + few drops of Hagers reagent (Saturated aq. Solution of
Picric acid), formation of crystalline yellow precipitate
Drug solution + few drops of Wagner’s reagent (dilute Iodine solution),
formulation of reddish-brown precipitate
Tannic Acid Test
Drug solution + few drops of tannic acid solution, formation of buff
8. Physical Properties:
◦ Most alkaloids are crystalline solids.
◦ Few alkaloids are amorphous solids e.g. opium
◦ Some are liquids that are either:
Volatile e.g. nicotine and coniine, or
Non-volatile e.g. pilocarpine and hyoscine.
The majority of alkaloids are colorless but some are
◦ Colchicine and berberine are yellow.
◦ betanidine is orange.
The salts of sanguinarine are copper-red
9. III- Solubility:
Both alkaloidal bases and their salts are soluble in
Generally, the bases are soluble in organic solvents and
insoluble in water
Bases soluble in water: caffeine, ephedrine, codeine, colchicine,
pilocarpine and quaternary ammonium bases.
Bases insoluble or sparingly soluble in certain organic solvents:
morphine in ether, theobromine and theophylline in benzene.
Salts are usually soluble in water and, insoluble or
sparingly soluble in organic solvents.
Salts insoluble in water: quinine monosulphate.
Salts soluble in organic solvents: lobeline and apoatropine
hydrochlorides are soluble in chloroform
10. IV- Isomerization:
Optically active isomers may show different physiological
activities. l-ephedrine is 3.5 times more active than
l-ergotamine is 3-4 times more active than d-ergotamine.
d- Tubocurarine is more active than the corresponding l- form.
Quinine (l-form) is antimalarial and its d- isomer quinidine is
The racemic (optically inactive) dl-atropine is physiologically
11. Chemical Properties
Most of the alkaloids are basic in nature, due to the availability of
lone pair of electrons on nitrogen.
The basic character of the alkaloid compound is enhanced if the
adjacent functional groups are electron releasing.
The alkaloid turns to be neutral or acidic when the adjacent functional
groups are electron withdrawing like amide group which reduces the
availability of the lone pair of electron.
Their salt formation with an inorganic acid prevents many a time their
In the natural form, the alkaloids exist either in Free State, as amine or
as salt with acid or alkaloid N-oxides.
13. ◦ Narcotic analgesic e.g.Morphine
◦ Antimalarial e.g. Quinine
◦ Reflux excitability e.g.Strychnine
◦ Respiratory stimulant e.g.Lobeline
◦ Neuralgia e.g. Aconitine
◦ Oxytocic e.g. Erogotometrine
◦ Bronchodilator e.g. Ephedrine, vasicine
◦ Anticholinergic e.g. Atropine
◦ CNS stimulant e.g. Caffeine
◦ Antitussive e.g. Codeine
◦ Antiarrythmic e.g.Quinidine
◦ Antihypertensive e.g. Reserpine
◦ Anticancer e.g. Vincristine
◦ Antiglucoma e.g. Pilocarpine
14. Synonyms: Vinca rosea, Catharanthus, Madagascar periwinkle
Vinca is the dried entire plant of Catharanthus roseus Linn., belonging
to family Apocynaceae.
C.C. The important alkaloids in Catharanthus are the dimer indole
indoline alkaloids Vinblastine and Vincristine and they possess definite
anticancer activity. Vindoline and Catharanthine are indole monomeric
alkaloids. It also contains monoterpenes, sesquiterpene, indole and
Use:It's cytotoxic used for hodgkins and non hodgkins disease.
Vinblastin is an antitumour alkaloid used in the treatment of Hodgkin’s
Vincristine is a cytotoxic compound and used to treat leukaemia in
Anticancer single or combination therapy.
M.O.A: bind to protein (tubulin) which inhibits mitosis in
Sarpagandha, Chandrika; Chootachand; Indian snake root.
Rauwolfia consists of dried roots of Rauwolfia serpentina Benth.,
belonging to family Apocynaceae.
Chemical Constituents: It contains about 0.7–2.4% total
alkaloidal bases from which more than 80 alkaloids have been
isolated. The prominent alkaloids isolated from the drug are
reserpine, rescinnamine, ψ-reserpine, rescidine, raubescine and
The other alkaloidal components are ajmalinine, ajmaline,
ajmalicine (8-yohimbine), serpentine, serpentinine,
tetrahydroreserpine, raubasine, reserpinine, isoajamaline and
Rauwolfia in used as hypnotic, sedative and
It is specific for insanity, reduces blood pressure and
cures pain due to affections of the bowels.
It is given in labours to increase uterine contractions
and in certain neuropsychiatric disorders.
Ajmaline, which has pharmacological properties
similar to those of quinidine, is marketed in Japan for
the treatment of cardiac arrhythmias.
18. Marketed Products
It is one of the ingredients of the preparations known as
Confido, Lukol, Serpina (Himalaya Drug Company)
and Sarpagandhan bati (Baidyanath).
Belladonna herb; Belladonna leaf; Deadly night shade leaves; Banewort;
Death’s herb, Dwale; Poison black cherry; Folia belladonnae.
Belladonna consists of dried leaves and flowering tops of Atropa
belladonna Linn. (European Belladonna), belonging to family Solanaceae.
It contains about 0.35% of total alkaloids calculated as hyoscyamine.
• Main Alkaloids are:
3. Hyoscine (Scopolamine).
Hyoscyamine is the major natural alkaloid with negative optical rotation (l-
During extraction hyoscyamine racemizes to the optically inactive dl
Both alkaloids composed of tropine base and tropic acid
The drug is used as adjunctive therapy in the treatment of
functional digestive disorders, including spastic, mucous and
ulcerative colitis; diarrhoea, and pancreatitis.
Due to anticholinergic property, it is used to control excess
motor activity of the gastrointestinal tract and spasm of the
Decrease motility of smooth muscles so used as
Consumption of Belladonna checks excessive perspiration of
patients suffering from tuberculosis.
Belladonna acts as a parasympathetic depressant.
It is one of the ingredients of the preparation known as Belladona
plaster (Surgi Pharma) for backache, stiffness of muscles and boil,
21. Synonyms: Crude Opium; Raw Opium; Gum Opium; Afim; Post.
Biological Source: Opium is the air dried milky latex obtained by incision
from the unripe capsules of Papaver somniferum Linn, or its variety P.
album Decand., belonging to family Papaveraceae.
Opium is required to contain not less than 10% of morphine and not less
than 2.0% of codeine. The thebaine content is limited to 3%.
C.C: The alkaloids are combined with meconic acid.
The other alkaloids isolated from the drug are codeine (0.8–2.5%), narcotine,
thebaine (0.5–2%). noscapine (4–8%), narceine and papaverine (0.5–
2.5%). Morphine contains a phenanthrene nucleus
The drug also contains sugars, sulphates, albuminous compounds, colouring
matter and moisture.
Opium and morphine have narcotic, analgesic and sedative
action and used to relieve pain, diarrhoea dysentery and
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.
Opium, morphine and the diacetyl derivative heroin, cause