Page 3 - phytochemistry II -pharmD general
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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.
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