Page 5 - phytochemistry general program
P. 5
- 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:
Secondary metabolites. .1
Naturally occurring organic bases. .2
Containing nitrogen in heterocyclic ring. .3
Biogenetically derived from amino acids. .4
Have potent pharmacological effect on animals . .5
They are ppted by alkaloidal ppting reagents. .6
b) Proto alkaloids:
Biogenetically They are derived from amino acids . but .1
They lack a heterocyclic ring e.g. Ephedrine (nitrogen atom is not involved in .2
heterocyclic ring).
c) Pseudo alkaloids:
biogenetically unrelated to amino They are .1
acids (They are not derived from amino acids).
e.g. purine bases [caffeine, theobromine and theophylline]
The Role of Alkaloids in Plants
1- Protective against insects and herbivores (bitterness and toxicity).
2- Products of detoxification in
metabolic reactions (waste products of metabolism)
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