Page 2 - Phytochemistry 2 (06-PG 605)

Alkaloids

Introduction:

 Alkaloids are extremely difficult to define, because they do not represent a
homogenous group of compounds from either, chemical, biochemical or
physiological point of view.

 The term alkaloid or alkali-like was previously applied to basic nitrogen-cont.
(heterocyclic ring) Compounds of plant origin with pharmacological activity
but

- Some alk. are known to have simple and or acyclic amine structures, others
as colchicine is not basic and its nitrogen atom is not incorporated in
heterocyclic ring.

- Some alkaloids are derived from animal source, together with some
synthetic & semisynthetic comp. are closely related to natural alkaloids e.g.
apomorphine & homatropine.

The most accepted definition is obtained by classifying alkaloids into 3
groups:

a – True (Typical) alkaloids.
b – Proto alkaloids.
c – Pseudo alkaloids.

a) Typical (True) alkaloids:
1. Secondary metabolites.
2. Naturally occurring organic bases.
3. Containing nitrogen in heterocyclic ring.
4. Biogenetically derived from amino acids.
5. Have potent pharmacological effect on animals .
6. They are ppted by alkaloidal ppting reagents.

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