UNIVERSITY OF SCIENCE & TECHNOLOGY,CHITTAGONG

PREPARED BY:APUSI CHOWDHURY

Roll no:898

CHEMISTRY OF ALKA-LOIDS

CONTENTS Introduction

Properties of alkaloids

Why alkaloids are basic ???

Classification of alkaloids

Test for alkaloids

Conclusion

References

INTRODUCTIONAlkaloids are a group of naturally occur-ring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar structure are also termed alkaloids. In addi-tion to carbon, hydrogen and nitrogen, alkaloids may also contain oxygen, sulfur   and, more rarely, other elements such as chlorine, bromine, and phosphorus.

PROPER-TIES OF

ALKALOIDs

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Basic in nature Most alkaloids are well-defined crys-talline substances which unite with acids to form salts.In the plant they may exist in the free state, as salts or as N-oxides.In addition to the elements carbon, hydrogen and nitrogen, most alka-loids contain oxygen.Give a precipitate with heavy metal iodides

WHY ALKA-LOIDS ARE BASIC IN

NATURE???

Alkaloids usually contain one nitrogen atom, Although some, like ergotamine may contain up to 5. The nitrogen may exist as primary amine, secondary amine or tertiary amine. Because the nitrogen atom con-tains unshared pair of electron so alkaloids are basic and resemble ammonia’s chem-ical properties. The degree of basicity varies greatly, depending on the structure of the molecule and the presence and lo-cation of other functional group.

CLASSIFICATION OF ALKA-LOIDS

According to pharmacognosy, alkaloids are

broadly classified into two classes depend-ing upon whether the nitrogen is a part of a ring or not.

1] Non-Heterocyclic Alkaloids or Atypical Al-kaloids

2] Heterocyclic Alkaloids or Typical Alkaloids

NON HETROCYCLIC These are also sometimes called

proto-alkaloids or biological amines. These are less commonly found in nature. These molecules have a ni-trogen atom which is not a part of any ring system. Examples of these include ephedrine, colchicine, ery-thromycin and taxol etc.

NAME STRUCTURE

Ephedrine

Colchicine

Name Structure

Erythromycin

Taxol

Heterocyclic Alkaloids or Typical Alkaloids:

Structurally these have the nitrogen as a part of a cyclic ring system. These are more commonly found in nature. Heterocyclic alkaloids are further subdivided into 14 groups based on the ring structure containing the nitrogen.

NAME HETROCYCLE EXAMPLE

Pyrrole and Pyrrolidine

Pyrrolizidine

NAME HETROCYCLE EXAMPLE

Pyridine and

Piperidine

Tropane

NAME HETROCYCLE EXAMPLE

Quinoline

Isoquinoline

NAME HETROCYCLE EXAMPLE

Aporphine

Quinolizidine

NAME HETROCYCLE EXAMPLE

Indole

Indolizidine

NAME HETROCYCLE EXAMPLE

Imidazole

Purine

NAME EXAMPLE

Steroidal

Terpenoid

TEST FOR ALKALOIDS

• Saturated solu-tion of picric acid.

• Observation: yellow precipi-tate

• Mercuric potas-sium iodide so-lution

• Observation: white precipi-tate

• Potassium bis-muth iodide solu-tion.

• Observation : or-ange coloured precipitate

• Iodine in potassium io-dide

• Observation : red-brown pre-cipitate

HAGER’S REAGENT

MAYER’S REAGENT

DAGEN-DROFF’S

REAGEN

T

WAGNER’SREAGEN

T

CONCLUSION:Alkaloids have high pharmacological and physiological activities:

on the CNS, they are depressants (morphine) or stimulants (caffeine).on the autonomic nervous system; anticholinergics (atropine, hyoscyamine).In addition, alkaloids include local anesthetics (cocaine), agents to treat fibrillation (quinidine), antitumor agents (vinblastine), antimalarials (quinine), antibacterial (berberine). Occur naturally which simply the methyl ether of morphine and converted to morphine in the body.Used in prescription cough medicines and as analgesic. Atropine is used as antidote to nerve gas poisoning.

References• Evans, W. C. Trease and Evans Phar-

macognosy, 16th ed.; Elsevier: New York, 2009.

• Varro E. Tyler, Lynn R. Brady & J..E.Robbers Pharmacognosy, 9th ed; U.S.A, 1988

• www.webcrawler.com 

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