This document discusses several classes of alkaloids, including β-carboline, imidazole, purine, and others. It provides details on the occurrence, chemical structure, synthesis, identification tests, uses, and isolation methods for specific alkaloids. Key alkaloids discussed include harmine, harmaline, yohimbine, reserpine, pilocarpine, caffeine, theobromine, and theophylline. The document also outlines methods for isolating caffeine, theophylline, and theobromine from tea leaves.

1. β-Carboline, Imidazole and
Purine based Alkaloids
By
Dr. Mostafa Mahmoud Hegazy ( PH.D.)

2. Alkaloids of the β-Carboline Group
L-Tryptophan
N
H
NH2
O
OH
N
H
NH2
– CO2
Tryptamine
N
H
N
1
2
34
5
6
7
8
9
-carboline
Peganum harmala
alkaloids
Yohimba alkaloids
Rauwolfia alkaloids

3. Harmine and Harmaline
Occurrence
The seeds of Peganum harmala, Fam.
Zygophyllaceae.
They are hallucinogenic alkaloids
N
N
CH3
H3CO
H
HarmalineHarmine
7
9
4
1
3
56
8 N
N
CH3
H3CO
H

4. Chemical Synthesis of Harmine and Harmaline
N
H
NH2H3CO
6-Methoxytryptamine
CH3CHO
pH 6-7
glyoxal
CH2OHCHO
Tetrahydroharmine
Dehydrogenation
Harmine
H3PO4
Harmaline
PdN
NH
CH2OH
H3CO
H
N
NH
CH3
H3CO
H

5. Tests for identification
Harminean  Orange color.
Harmaline  Yellow brownish gray
color.
Color tests
Marquis' reagent
Harmine  Blue color Green
Harmaline  Greenish brown color.
Mandalin’s
reagent
Harmine + gold bromide  Rod-shaped crystals.
Harmaline + platinic chloride  Small fern-like
crystals.
Crystal tests
•Effects of harmine and harmaline
•Harmine and harmaline are the main active principles of a hallucinogenic
drink, known in South American regions. They have no therapeutic use.
◘ Small dose: tranquilizer effect.
◘ Large dose: CNS stimulant and hallucinogenic effects.

6. Yohimba Alkaloids
Yohimbine (Aphrodine)
Occurrence
Yohimbine occurs in the barks of the West African tree
Pausinystalia yohimbe = Coryanthe yohimba, Fam. Rubiaceae.
N
H
N
OH
H3COOC
Yohimbine
H
H
H

7. Tests for identification
Yohimbine + conc. H2SO4 + crystals of K2Cr2O7  violet
streaks  blue green (c.f. strychnine).
Uses
Yohimbine is mainly used as an aphrodisiac drug (dilate
blood vessels).

8. N
N
R
H
H
H
H
OCH3
O
H3CO
O
O
H3CO OCH3
OCH3
Reserpic acid part 3,4,5-Trimethoxybenzoic acid part
N
N
H3CO
H
H
H
H
OCH3
O
H3CO
O
Reserpic acid part 3,4,5-Trimethoxycinnamic acid part
Reserpine R = OCH3
Deserpine R = H
O
OCH3
OCH3
OCH3
Recinnamine
Rauwolfia or (snake root)
* Rauwolfia is the dried rhizome and roots of Rauwolfia serpentina (Apocynaceae).

9. Hydrolysis of Rauwolfia Alkaloids
Reserpine
Hydrolysis Reserpic acid + Trimethoxybenzoic acid + Methanol
Deserpedine (Demethylated derivative of Reserpine)
Deserpedine
Rescinnamine Reserpic acid + Trimethoxycinnamic acid + Methanol
Hydrolysis
Deserpic acid + Trimethoxybenzoic acid + Methanol
Hydrolysis
Chemical test
Reserpine +
p-Dimethylaminobenzaldehyde Reagent
p-Dimethylaminobenzaldehyde
glacial acetic acid
H2SO4
Green color turns red
in excess of acids

10. Powdered Rauwolfia roots
- moistened with 10% NaHCO3 or Na2CO3 solution
(weakly basic alkaloids)
- extracted with benzene.
Benzene extract
Shake with dil. acid
Alkaloidal salts in aqueous layer
Extract with CHCl3
CHCl3 layer
contains weakly basic alkaloids
Residue
Crystallization from MeOH
Crystals
Reserpine
Mother liquor
Rescinnamine and Deserpidine
evaporated to dryness and the alkaloids
are separated by column chromatography.
Aqueous layer
Evaporate

11. * Rauwolfia was used as an antidote to snake-bite, to remove white
spots in the eyes, against stomach pains, fever, vomiting, and headache.
* Excellent antihypertensive and tranquillizer activity.
Uses

12. L-Histidine
NH2N
H
N
O
OH
N
N
CH3
O
O
CH3
N
N
CH3
O
O
CH3
N
N
CH3
O
O
H
HO
PilosinePilocarpine Isopilocarpine
ALKALOIDS DERIVED FROM HISTIDINE
Imidazole Alkaloids
The imidazole alkaloids found in Jaborandi leaves
(Pilocarpus microphyllus and P. jaborandi; Rutaceae)
Imidazole
H
N
N

13. * Pilocarpine is oily non-volatile liquid alkaloid.
* Pilocarpine is a mono-acidic tertiary base, having a lactone ring and
an Imidazole nucleus.
* The lactone ring in Pilocarpine is opened by caustic alkalis but not
affected by ammonia, this leads to loss the activity.
* The imidazole ring in Pilocarpine is destroyed by oxidation with KMnO4

14. Iso la t io n o f Pilo ca rp in e
Shaken with HCl and the alkaloidal salt is
allowed to crystallize
Powdered leaves of Jaborandi
- Extract with benzene.
- Benzene layer acidified with dilute HCl
Acidic aqueous layer
- Alkalinized with NH3
- Extracted with CHCl3
CHCl3 layer
- Treat with Na2CO3 solution

15. Uses
* Pilocarpine is a cholinergic agent and stimulates the muscarinic
receptors in the eye, causing constriction of the pupil (miotic) and
enhancement of outflow of aqueous humour (treatment of glaucoma).
• The effects are similar to those of physostigmine and the two agents are
sometimes combined.
• Pilocarpine gives relief for dryness of the mouth that results in patients
undergoing radiotherapy for mouth and throat cancers.
• Pilocarpine is antagonistic to Atropine.
• As muscarinic agonists, pilocarpine and analogues are also being
investigated for potential treatment of Alzheimer’s disease.

16. C hem ical T ests:
1) Helch's test
Aqueous solution of Pilocarpine salt + drops of H2O2 + drops of K2Cr2O7 Violet
color
2) Ekkert's test
Aqueous solution of Pilocarpine HCl + Na nitroprusside + dil NaOH
leave few minutes then acidify with HCl
Wine-red color Green color
Na2S2O3

17. PURINE ALKALOIDS
• Purines are derivatives of a heterocyclic nucleus consisting of
a six-membered Pyrimidine ring fused to a five-membered Imidazole
ring.
Purines are Psudo alkaloids (Are not derived from amino acids but
have nitrogen in a heterocyclic ring)
Pyrimidine
N
N
Imidazole
N
H
N
N
N
H
N
N
1
2
3
4
5
6
7
8
9
HN
N
H
H
N
N
1
2
6
Xanthin
(2,6-dioxy-purine)
O
O
Purine

18. Occu r r e n ce
Tea leaves
Camellia sinensis (Thea sinensis) Fam. Theaceae

19. Tea is the prepared leaves and leaf buds of
Camellia sinensis (Thea sinensis) (Theaceae).
Occurrence
Coffee consists of the dried ripe seed of Coffea
arabica or other Coffea species (Rubiaceae).
Cocoa (or cacao) is derived from the roasted
seeds of Theobroma cacao (Sterculiaceae).
Cola, or kola, is the dried cotyledon from seeds
of various species of Cola e.g. C. nitida and
C. acuminata (Sterculiaceae)

20. ● The purine alkaloids Caffeine, Theobromine, and
Theophylline are all methyl derivatives of xanthine.
N
N
H
N
N
O
O
CH3
H3C
Theophylline
(1,3-dimethylxanthine)
HN
N
N
N
O
O
CH3
Theobromine
(3,7-dimethylxanthine)
CH3
N
N
N
N
O
O
CH3
CH3
H3C
Caffeine
(1,3,7-trimethylxanthine)
1
3 3
7
1
3
7
* These alkaloids are very week bases, they
form salts only with strong acids.

21. TheobromineTheophyllineCaffeine
Sparingly
soluble
Soluble
Soluble
Insoluble
Partially soluble
Insoluble
Soluble
Soluble
Insoluble
Soluble
Soluble
Insoluble
Insoluble
Soluble
Solubility:
H2O
Boiling H2O
Cold NH4OH
Cold NaOH
CHCl3 and
Benzene
weak base
“form salts with
strong acids
HCl”
more acidic, can
form salts with
both acids and
bases
weak base
“form salts with
strong acids
HCl”
Physicochemical characters of Purine alkaloids.

22. TheobromineTheophyllineCaffeine
Slightly Soluble in H2O,
ethanol and CHCl3.
Soluble in H2O, and ethanolSoluble in H2O, benzene,
ethanol and CHCl3
Insoluble in Ether and
Benzene
Insoluble in benzene.Sparingly soluble in Ether
Freely Soluble in dil
acids and alkali but
insoluble in NH4OH
Freely Soluble in dil acids,
alkali and NH4OH
Soluble in dil acids
It can form salts with both
acids and bases.
It is more acidic than
Theobromine
Weak base.
Decomposes by strong
caustic alkalis.

23. Tests for identification
This test is positive with caffeine, theobromine and
theophylline
Crystals of caffeine + drops of conc. HCl + KClO3,
evaporated on water bath  red color  violet on
exposure to ammonia vapor.
Murexide
test
This test is positive with caffeine and theophylline
A alkaloid solution + tannic acid  white precipitate
dissolves in excess of the reagent.
Tannic
acid test
This test is characteristic for theobromine.
Alkaloid solution + conc. HCl + Br2 water + FeSO4 + NH3
 blue color
FeSO4
test
These alkaloids give No precipitate with Mayer’s Reagent

24. Uses
Caffeine
CNS stimulant, not analgesic but increases effect of analgesic to
relieve headache, fat burning preparations and weak diuretic action.
Theobromine
Little stimulant action, more diuretic activity than Caffeine, and little
smooth muscle relaxant.
Theophylline
Low stimulant action, effective diuretic, and smooth muscle
relaxant for relief of broncho-spasm (respiratory stimulant).

25. ISOLATION OF CAFFEINE, THEOPHYLLINE AND THEOBROMINE FROM TEA
Powdered Tea Boiled with H2O
Filter
Lead acetate
(to ppt. Tannins)
Filtrate
- Add Sod. hydrogen phosphate
to remove excess lead
- Conc
Filter
Filtrate
CHCl3 layer
CAFFEINE
Aq. layer
Shake with CHCl3
(Theophylline & Theobromine)
Add NH3
Soluble Insoluble
THEOPHYLLINE THEOBROMINE