This document provides information about alkaloids found in plants. It defines alkaloids as nitrogenous organic compounds that are basic in nature. Alkaloids are found distributed across many angiosperm and gymnosperm families as well as some fungi. They serve functions like protecting plants from herbivores and regulating growth. Alkaloids are extracted from plants using organic solvents and tested for using precipitating and coloring reagents. They exhibit a variety of pharmacological activities and are used as medicines, like morphine as a pain reliever.
15. Alkaloids
Definition : Alkaloid = Alkali like
• Alkaloids are organic nitrogenous substances
usually found in plants. They are
heterogenous group of compound either from
chemical, biochemical or physiologic view
points.
• As name suggests they are alkaline in nature.
• Contain one or more than one nitrogen
(usually heterocyclic)
18. Alkaloids
Properties
• Basic in nature
• The nitrogen atom present responsible for
alkaline activity – resembles ammonia in
chemical property
• The nitrogen may exist as
• Primary – RNH2
• Secondary – R2NH
• Tertiary – R3N
Amine
19. Alkaloids
Properties contd..
• Alkaloids are converted into their salts by aq.
mineral acids
• The chemical rules designate that the names
of all alkaloids should end in ‘ine’
20. Alkaloids
Functions of alkaloids in plants
• Poisonous agents protecting the plant against
insects and herbivores “Animals that feed chiefly on
plants”.
• End products of detoxification reactions.
• Regulatory growth factors.
• Reserve substances capable of supplying nitrogen
or other elements necessary to the plant’s
economy.
21. Alkaloids
Functions of alkaloids in plants contd…
• Involved on acid metabolism in plant
• Storing and transportation of acid
• Do not participate in metabolic sequences
• Not solely the waste or end products of
metabolism.
22. Alkaloids
Extraction
Extraction is carried out by Organic solvents
Clear extract dried under vacuum
Plant material powdered in to fine powder
Moistened with water
Strong solution of alkali added (mostly liq. NH3)
Precipitation of alkaloid
Extracted with organic solvents (mostly CHCl3)
Separated by solubility method
24. Classification of Alkaloids
• Generally, there are two broad divisions:
1.Heterocyclic or typical alkaloids, divided into 14
groups according to their ring structure.
2.Nonheterocyclic or atypical alkaloids, sometimes
called ‘protoalkaloids’.
• Alkaloids are usually classified according to the
nature of the basic chemical structures from
which they derive.
26. Tests for alkaloids
There are several general reagents, which may
be used to test the presence of alkaloids or to
help their identification. This includes the
alkaloidal precipitating reagents and the
alkaloidal coloring reagents. In addition, there
are some special reagent that can be used for
recognizing and confirming the identity of each
alkaloid.
27. Tests for alkaloids
Alkaloidal precipitating reagents:
1. Mayer’s reagent (potassiomercuric iodide
solution)
2. Wagner’s reagent (solution of iodine in
potassium iodide)
3. Dragendorff’s reagent (potassium bismuth
iodide)
29. Pharmacological activity and uses
Alkaloids are particularly interesting substances
because of their multiple pharmacological
activities:
1.on the CNS, whether they are depressants
(morphine) or stimulants (caffeine);
2.on the autonomic nervous system:
sympathomimetics (ephedrine) or
sympatholytics (yohimbine, certain ergot
alkaloids), parasympathomimetic (pilocarpine),
anticholinergics (atropine, hyoscyamine), or
ganglioplegics (nicotine).
30. Pharmacological activity and uses
In addition, alkaloids include
• Local anesthetics (cocaine),
• Agents to treat fibrillation (quinidine)
• Antitumor agents (vinblastine)
• Antimalarials (quinine)
• Antibacterials (berberine)
• Amebicides (emetine).
