Alkaloids: Introduction, Property and classification

Alkaloids are major secondary metabolites reported in higher plants. In this PPT I have covered Introduction, Property, Clarification and identification tests.

1. ALKALOID: ANOVERVIEW
Presented by
Mr. O. P. Verma
Associate Professor
Dept. of Pharmacognosy
Goel Institute of Pharmacy and Sciences,
Lucknow

2. Content
➢Metabolites
➢Definition
➢Exceptionswithrespecttodefinition
➢Distribution,occurence&formsofalkaloids.
➢Physical&chemicalproperties
➢Classificationofalkaloids
➢Chemicaltestforalkaloids
➢Extraction,isolation&purificationofalkaloids

3. Primary Metabolites Secondary Metabolites
Themetaboliteswhicharerequiredfor
thegrowthandmaintenanceofcellular
functionarecalledprimarymetabolites
Secondarymetabolitesdonotplayarolein
growth,development,orreproduction.
However,theyplayaroleinecological
functionslikedefensemechanisms,serveas
antibiotics,andproducepigments.
Primarymetabolitesarecompounds
thataredirectlyinvolvedinthegrowth
anddevelopmentofaplant
Theyalsoindirectlysupportthecell,in
sustainingtheirlifeforlongduration.
Producedinlargequantityand
extractioniseasy
Producedinsmallquantityandextractionis
difficult
Primarymetabolitesareapartofthe
basicmolecularstructureofan
organism.
Secondarymetabolitesarenotapartofthe
basicmolecularstructureofanorganism.
Ex.vitamins,aminoacids,nucleosides
andorganicacids
Ex.alkaloids,Glycosides,steroids,antibiotics,
toxins
Difference between Primary Metabolites
and Secondary Metabolites

4. Alkaloids
Definition
Alkaloidsarebasicheterocyclic
nitrogenouscompoundsofplant
originthatarephysiologically
active.

5. Modified Definition:
Alkaloids are cyclicorganic
compoundscontainingnitrogenina
negativestateofoxidationwithlimited
distributionamonglivingorganisms.

6. Exceptions with respect to definition:
➢Basicity:Somealkaloidsarenotbasice.g.
Colchicine,Piperine,Quaternaryalkaloids.
➢Nitrogen:Thenitrogeninsomealkaloidsis
notinaheterocyclicringe.g.Ephedrine,
Colchicine,Mescaline.
➢PlantOrigin:Somealkaloidsarederived
fromBacteria,Fungi,Insects,Frogs,
Animals.

7. Distribution and occurence:
Rare in lower plants.
Families rich in Alkaloids: Apocynaceae,
Rubiaceae, Solanaceae and Papaveracea.
Families free from Alkaloids: Rosaceae,
Labiatae.

8. Distribution in Plant:
➢All Parts e.g. Datura.
➢Barks e.g. Cinchona
➢Seeds e.g. Nux vomica
➢Roots e.g. Aconite
➢Fruits e.g. Black pepper
➢Leaves e.g. Tobacco
➢Latex e.g. Opium

9. Forms of Alkaloids:
➢Free bases
➢Salts with Organic acids e.g. Oxalic,
acetic acids
➢Salts with inorganic acids e.g. HCl, H
2SO
4.
➢Salts with special acids: e.g.
Meconic acidin Opium
Quinic acidin Cinchona
➢Glycosidal form e.g. Solanine in Solanum.

10. Function in Plants
➢Protective.
➢Detoxification.
➢Sourceofnitrogen.
➢Growthregulators.
➢Sourceofenergy.

11. Physical Properties:
I-State:
➢Mostalkaloids are crystalline solids.
➢Few alkaloids are amorphous solids e.g. emetine.
➢Some areliquidsthat are either:
Volatilee.g. nicotine and coniine, or
Non-volatilee.g. pilocarpine and
hyoscine.
II-Colour:
The majorityof alkaloids are colorlessbut some are
colorede.g.:
➢Colchicine and berberine are yellow.
➢Canadine is orange.
➢Betanedine is red.

12. III-Solubility:
➢Bothalkaloidalbasesandtheirsaltsaresolubleinalcohol.
➢Generally,thebasesaresolubleinorganicsolventsand
insolubleinwater
Exceptions:
➢Basessolubleinwater:caffeine,ephedrine,codeine,
colchicine,pilocarpineandquaternaryammoniumbases.
➢Basesinsolubleorsparinglysolubleincertainorganic
solvents:morphineinether,theobromineandtheophyllinein
benzene.
➢Saltsareusuallysolubleinwaterand,insolubleorsparingly
solubleinorganicsolvents.
Exceptions:
➢Saltsinsolubleinwater:quininemonosulphate.
➢Saltssolubleinorganicsolvents:lobelineandapoatropinehydrochlorides
aresolubleinchloroform.

13. Chemical Properties:
I-Nitrogen:
Primary amines R-NH
2 e.g. Norephedrine
Secondary amines R
2-NH e.g. Ephedrine
Tertiary amines R
3-N e.g. Atropine
Quaternary ammonium salts R
4-N e.g d-Tubocurarine
II-Basicity:
➢R
2-NH >R-NH
2 >R
3-N
➢Saturated hexacyclic amines are more basic than aromatic
amines.

14. III-Oxygen:
➢Most alkaloids contain Oxygen and
are solid in nature e.g. Atropine.
➢Some alkaloids are free from
Oxygen and are mostly liquids e.g.
Nicotine.

15. IV-Stability:
➢Effect of heat:
Alkaloids are decomposed by heat,
except Strychnineand caffeine
(sublimable).
➢Reaction with acids:
1-Salt formation.
2-Dil acids hydrolyze Ester Alkaloids e.g.
Atropine

16. General Classification:
➢True (Typical) Alkaloidsthat are derived from
amino acids and have nitrogen in a heterocyclic
ring. e.g Atropine
➢Protoalkaloidsthat are derived from amino
acids and do not have nitrogen in a heterocyclic
ring. e.g Ephedrine
➢Pseudo alkaloidsthat are not derived from
amino acids but have nitrogen in a heterocyclic
ring. e.g Caffeine
➢False alkaloidsare non alkaloids give false
positive reaction with alkaloidal reagents.

18. Chemical classification:
1. Pyrrolidine derivatives
Ex. Hygrine, cocaine etc.
2. Pyperidine derivatives
Ex. Piperine, lobeline etc.

19. 3. Pyrrolizidine derivatives
Ex. Echimidine,
Symphatine etc.
4. Tropane derivatives
Ex. Atropin

20. 5. Quinoline derivatives
Ex. Quinine, cinchonin,
Cinchonidine etc.
6. Isoquinoline derivatives
Ex. Morphine, narcotine,
Narcein, codein
etc.

21. 7. Indole derivatives
Ex. Vincrisrine,
Vinblastine, etc.
8.Imidazole derivatives
Ex. Pilocarpine,
Isopilocarpine etc.

22. 9. Aporphine derivatives.
Ex. Boldine etc.
10. Quinazoline derivatives.
Ex. Vasaka etc.

23. 11. Purine derivatives
Ex. Caffeine etc.
12. Diterpene derivatives.
Ex. Aconotine.

24. 13. Steroidal alkaloids.
Ex. Solanidine
14. Duazocin alakloids
Ex. Lupanine.

25. Biosynthetic classification:
Alkaloids Precursor Example
Indole alkaloids Trymptophan
amino acid.
vincristine,
vinblastin etc.
Piperidine
alkaloids
lysine amino acid(piperin, lobaline
etc.
Pyrrolidine
alkaloids
ornithine amino
acid.
Nicotine etc.
Isoquinoline
alkaloids
tyrosine. morphine, codein,
emetine etc.
Imidazole
alkaloids
histidine pilocarpine,
isopilocarpine etc.
Amino/proto
alkaloids
phenylalanine
amino acid.
ephedrine etc.
Quinazolidine
alkaloids
Lupinine amino
acid.
vasaka etc.

26. Chemical tests for alkaloids :
1.Dragendorff’s test-
Dragendorff’s reagent
(Potassium-bismuth-iodide solution)
Test-
1ml of drug+1ml of dragendorff’s reagent-
A reddish brown ppt. shows presence of
alkaloids

27. 2. Mayer’s test-
Mayer’s reagent
(Potassium mercuric iodide solution)
Test-
1ml of drug extract+1ml of mayer’s reagent-
Whitish or cream coloured ppt shows
presence of alkaloids.

28. 3. Hager’s test-
Hager’s reagent
(Saturated aq. solution of picric acid)
Test-
1ml of drug extract+3ml of hager’s reagent
Yellow coloured ppt shows presence of
alkaloids.

29. 4. Wagner’s test-
Wagner’s reagent
(Iodine-potassium-iodide solution)
Test-
Drug extract+wagner’s reagent
Brown or reddish brown colour shows
presence of alkaloids.

30. 5. Tannic acid test-
Test-
Drug extract+5% tannic acid solution-
Buff colour ppt. shows presence of
alkaloids.

31. Extraction, Purification and Isolation of Alkaloids from
Powdered plants
➢Extraction and purification
Method I:
Thepowderistreatedwithalkalistoliberatesthefreebasesthat
canthenbeextractedwithwaterimmiscibleorganicsolvents.
Method II:
Thepowderedmaterialisextractedwithwateroraqueous
alcoholcontainingdiluteacid.Alkaloidsareextractedastheir
saltstogetherwithaccompanyingsolubleimpurities.
MethodIII:
Thepowderisextractedwithwatersolubleorganicsolvents
suchasMeOHorEtOHwhicharegoodsolventsforbothsalts
andfreebases.

33. ➢Liberation of the free bases:
Alkalisareusedtoliberatefreebases.Alkalismustbestrong
enoughtoliberatefreebases.However,choiceofstrongalkalis
mustbeavoidedinsomecases:
1-Ester Alkaloids e.g. Solanaceous Alkaloids
2-Amide Alkaloids e.g. Colchicine
3-Phenolic Alkaloids e.g. Morphine
4-Lactone Alkaloids e.g. Pilocarpine
5-Fatty Drugs due to saponification and emulsion formation.

34. ➢NH
4OH:
Most widely used due to many advantages:
1-Strong enough to liberate most of alkaloids
from their salts.
2-Milder than fixed alkalis so more safe.
3-Volatile so easy to get rid of it.
➢Other Alkalis:
Na
2CO
3, NaHCO
3, Ca(OH)
2, MgO.

35. Identification of Alkaloids:
➢Melting point
➢Colour test
➢Optical Rotation
➢Microcrystal test
➢HPLC, GC, GC-MS
➢UV, IR, NMR, MS.

36. THANX
FOR
GIVING
YOUR
VALUABLE TIME