general Isolation methods for alkaloids isolation, identification and analysis of phytoconstituents like Caffeine, Atropine, Glycyrrhetinic acid, Podophyllotoxin

1. Isolation, Identification and Analysis of
Phytoconstituents
General methods for isolation of alkaloids
Atropine
Caffeine
Glycyrrhetinic acid
Podophyllotoxin

2. General methods for isolation of
Alkaloids

3. Method A
• The powdered material that contains alkaloidal salts is moistened
with alkaline substances like sodium bicarbonate, ammonia,
calcium hydroxide, etc., which combines with acids, tannins and
other phenolic substances and sets free the alkaloids bases.
• Extraction is then carried out with organic solvents such as ether
or chloroform.
• The concentrated organic liquid is then shaken with aqueous acid
and allowed to separate.
• Alkaloid salts will be present in aqueous liquid, while many
impurities remain behind in the organic liquid.

4. Method B
• The collected powdered material is extracted with water or
aqueous alcohol containing dilute acid.
• Chloroform or other organic solvents are added and shaken to
remove the pigments and other unwanted materials.
• The free alkaloids are then precipitated by the addition of excess
alkalis like, sodium bicarbonate or ammonia and separated by
filtration or by extraction with organic solvents.
• Volatile liquid alkaloids (nicotine and coniine) are isolated by
distillation.
• The powdered material that contains alkaloids is extracted with
water and the aqueous extract is made alkaline with sodium
carbonate or ammonia and the alkaloid is distilled off in steam.
• This could be collected and purified.

5. CAFFEINE

6. • Caffeine or 1,3,7- trimethyl xanthin is a purine base present along
with other related bases like theophylline and theobromine in
coffee, tea, cocoa, kola and mate.
• Although caffeine is largely produced synthetically, it is usually
isolated from tea leaves or recovered from coffee seeds.
• Tea leaves contain 1–4% of caffeine while coffee seeds contains
1–2% of caffeine.
• Caffeine was first discovered by Robiquet in coffee in 1821, and
mid later in 1827, Oudry found it in tea leaves.

7. Isolation of caffeine :
• The coarse powder of tea leaves is extracted with boiling water
and the aqueous extract is filtered while hot.
• The warm extract is treated with lead acetate to precipitate
tannins and filtered.
• The excess of lead acetate present in the solution is precipitated
as lead sulphate with dilute sulphuric acid.
• The filtered solution is boiled with charcoal to remove colouring
matter, if any and filtered to remove charcoal.
• The filtered decolourized solution is extracted with chloroform.
• The combined chloroform extract after evaporation gives caffeine
as a white material.
• It is re-crystallized with alcohol.
• Melting point: 235–237°C

8. Chemical tests for caffeine :
1. Caffeine and other purine alkaloids, gives murexide colour
reaction.
• Caffeine is taken in a Petri dish to which hydrochloric acid and
potassium chlorate are added and heated to dryness.
• A purple colour is obtained by exposing the residue to vapors of
dilute ammonia.
2. Caffeine also produces white precipitate with tannic acid
solution.

9. • Thin Layer Chromatography of Caffeine
• Dissolve 1 mg of caffeine in 1 ml of chloroform or methanol.
• Spot the sample on TLC plate
• Mobile phase : ethyl acetate–methanol–acetic acid (80:10:10).
• Visualize the dried TLC plate by exposure to iodine vapour.
• Caffeine develops a spot at Rf value 0.41

10. ATROPINE

11. • Atropine is a tropane alkaloid from the members of the
Solanaceae family.
• It is present in
• Atropa belladonna (Deadly Night shade),
• Datura stramonium and
• Hyoscyamus niger (Henbane)
• Other important solanaceous alkaloids are hyoscyamine, hyoscine
(scopolamine), apoatropin, belladonine and nor hyoscyamine.
• Atropine is an optically inactive levorotatory isomer of
hyoscyamine

12. • Atropine is isolated from the juice or the powdered drug.
Hyoscyamus niger is the preferred source for the manufacture of
atropine because of its high alkaloidal content, with D.
stramonium and Atropa belladonna next in order.
• The powdered drug material is thoroughly moistened with an
aqueous solution of sodium carbonate and then extracted with
ether or benzene.
• The alkaloidal bases are extracted from the solvent with water
acidified with acetic acid.
• The acid solution is then shaken with solvent ether to remove
colouring matter.
• The alkaloids are precipitated with sodium carbonate, filtered
off, washed and dried.
• The dried mass is dissolved in solvent ether or acetone and
dehydrated with anhydrous sodium sulphate before filtration.

13. • The filtrate after concentration and cooling yields crude crystals
of hyoscyamine and atropine from the solution.
• The crude crystalline mass is separated from the solution.
• The crude crystalline mass obtained after filtration is dissolved in
alcohol, and sodium hydroxide solution is added and the mixture
is allowed to stand until hyoscyamine is completely racemized to
atropine which is indicated by the absence of optical activity.
• The crude atropine is purified by crystallization from acetone.
• Melting point: 115–116°C

14. • Second method of isolation of atropine :
• The powdered material is extacted with absolute alcohol.
• The solvent is removed by the distillation to get a syrupy mass.
• The residue is then treated with 1% HCl.
• The acid solution is further purified by shaking with light petroleum ether.
• Sufficient quantity of ammonia is added to make the solution alkaline,
then treated with an organic solvent like chloroform.
• The chloroform solution is further shaken with dilute acid and the acid
solution is made alkaline with ammonia and again extracted with
chloroform.
• The solvent is removed by distillation and the residue comprises crude
alkaloids.
• The crude alkaloidal portion is neutralized with oxalic acid to get the
oxalates of atropine and hyoscyamine.
• Further these may be separated by fractional crystallization from acetone
and ether in which hyoscyamine oxalate is more soluble.

15. • Identification :
• Vitali–Marin test :
• Dilute solution of atropine, when treated with concentrated nitric
acid and the mixture evaporated to dryness on the steam bath,
produces a pale yellow residue.
• The residue gives a violet coloration when a drop of freshly
prepared solution of potassium hydroxide is added.

16. • Thin Layer Chromatography of Atropine
• One percentage solution of atropine dissolved in 2 N acetic acid
• Stationary Phase : Silica gel-G plate
• Solvent system (MP) :
• n-Butanol/acetic acid /distilled water (4:1:5)
• water/ acetic acid (8:2)
• Detection : UV Chamber
• Atropine gives the Rf value 0.18.

17. GLYCYRRHETINIC ACID

18. • Glycyrrhetinic acid is a pentacyclic triterpenic acid obtained from
the roots and stolons of Glycyrrhiza glabra family Leguminosae
commonly known as liquorice.
• A major component of liquorice root is a sweet triterpenic
saponin glycoside glycyrrhizin, which is a potassium and calcium
salt of glycyrrhizic acid about 6–14%.
• After hydrolysis, it gives two molecules of gluconic acid and an
aglycone glycyrrhetinic acid.

19. Isolation of glycyrrhetinic acid
• The crude drug is first extracted with chloroform.
• Chloroform extract is discarded.
• The marc is again extracted this time with 0.5 M sulphuric acid.
• The acid extract is cooled and shaken with chloroform.
• The combined chloroform extract is concentrated and dried to
yield glycyrrhetinic acid.
• Glycyrrhizin is hydrolysed to glycyrrhetinic acid during extraction
with sulphuric acid.

20. Second method of isolation of glycyrrhetinic acid
• Liquorice powder is extracted with boiling water to isolate
glycyrrhizin.
• The aqueous extract is concentrated, dried and used as liquorice
extract.
• The liquorice extract can be dissolved in water and acidified with
hydrochloric acid to pH 3-3.4 to precipitate glycyrrhetinic acid.
• The precipitate is filtered, washed with water till neutral pH and
then dried to yield glycyrrhetinic acid.
• Ammoniated glycyrrhizin, used in pharmaceutical trades is
prepared by precipitating glycyrrhizic acid from liquorice extract,
dissolving it in ammonia and drying the solution after spreading
in a thin film on a glass plate to give shining dark brown flakes.
• Melting point: 300°C

21. Thin Layer Chromatography of Glycyrrhetinic
Acid
• Dissolve 1 mg of glycyrrhetinic acid in about 1 ml of methanol-
chloroform (1:1) mixture.
• Stationary Phase : silica gel-G plate
• Solvent system (MP) : Toluene– ethyl acetate–glacial acetic acid
(12.5:7.5:0.5).
• Spray the dried plates with 1% vanillin-sulphuric acid or
anisaldehyde-sulphuric acid and heat for 10 min at 110°C.
• glycyrrhetinic acid gives purplish spot corresponding to the Rf
value 0.41.

22. UV Spectrophotometric method for estimation of
glycyrrhetinic acid
• Preparation of standard stock solution:
• The standard stock solutions of glycyrrhetinic acid is prepared by
dissolving 10 mg of glycyrrhetinic acid in Phosphate Buffer
(pH6.8) : Ethanol in 70 : 30 proportion and final volume is
adjusted with same solvent in 10ml of volumetric flask to get a
solution containing 1000 μg/ml of glycyrrhetinic acid.
• Aliquots of working stock solutions of glycyrrhetinic acid are
prepared with in the same solvent to get concentration in range
of 5-35μg/ml of glycyrrhetinic acid.

23. • Analysis of the herbal extract:
• Accurately weighed 20 mg of herbal hydroalcoholic extract of
Licorice is transferred to 10ml volumetric flask and dissolved in
Phosphate Buffer (pH-6.8): Ethanol in 70: 30 proportions and final
volume is adjusted with same solvent in 10ml volumetric flask.
• The sample solution was then filtered through Whatman filter
paper.
• From the above solution 0.1ml of solution is taken and diluted to
10ml with Phosphate Buffer (pH-6.8): Ethanol in 70: 30
proportions to get final concentration containing 20μg/ml of
glycyrrhetinic acid.
• Analysis of solution:
• The absorbance of resulting solutions (standard and test) were
measured at 254nm.
• A calibration curve of concentration vs. absorbance is prepared.

24. PODOPHYLLOTOXIN

25. • Podophyllotoxin is obtained from the root and rhizome of
Podophyllum hexandrum and Podophyllum emodii.
• Family : Berberidaceae
• Podophyllotoxin is a tetrahydronaphthalene derivative with OH and
lactone groups.
• The attachment at cis-position is responsible for the purgative
property and the attachment at trans-position corresponds for
anti-cancer property of the drug.
• Melting point: 114–118°C

26. Isolation of Podophyllotoxin
• Commercial podophyllin is obtained by extraction of powdered
rhizome/roots of P. emodii with methanol.
• Then it is reduced under vacuum.
• Semi-solid mass is put into acidulated water (10 ml HCl in 100 ml
water).
• The precipitates are allowed to settle.
• Filtrate is decanted and residue washed with cold water.
• Resin obtained is dried, and upon drying, it gives dark brown
amorphous powder called PODOPHYLLIN.
• The obtained powder is extracted with chloroform and further
purification is done by repeated re-crystallization from benzene
alone or alcohol benzene mixture followed by washing with
petroleum ether/hexane yield PODOPHYLLOTOXIN.

27. • Another method of extraction to obtain pure podophyllotoxin is
by dissolving the CHCl3 soluble fraction in alcohol.
• Then it is refluxed with neutral aluminum oxide so that solution
becomes light yellow.
• To alcoholic solution benzene is added which yielded
podophyllotoxin of 95–98%.
• Another method of isolating podophyllotoxin from
podophyllin/crude podophyllotoxin involves extraction over a bed
of neutral alumina with solvents like benzene, toluene, xylene,
etc., for about 1.5–4 h.
• Re-crystallization from organic solvents such as hot benzene,
toluene and xylene yields pure podophyllotoxin (95–97%).

28. Thin Layer Chromatography of Podophyllotoxin
• Podophyllotoxin is dissolved in methanol and is spotted on the
TLC plate.
• Solvent system - Toluene: ethyl acetate (5:7)
• Detecting agent is sulphuric acid.
• Spot of Podophyllotoxin under day light has violet colour.
• Rf value : 0.39