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148 Textbook of Pharmacognosy and Phytochemistry I
Chemical Identification
For detection of steroid nucleus: To the
glycosides test solution in acetic anhydride,
add few drops of sulphuric acid, positive test
gives reddish violet-green colouration.
Test for 2,6-deoxy Sugar
Keller-Killiani test: Glycosides (digitalis and
strophanthus) dissolved in acetic acid containing
traces of ferric chloride and add concentrated
sulphuric acid along the sides of test tube. At
the junction of the liquids, reddish-brown
colour gradually reduced to blue colour is
indicative of positive test.
Legal test: To 1 ml test solution, add 2 ml of
pyridine, 2–3 drops of sodium nitroprusside
followed by one to two drops of 20% sodium
hydroxide. Appearance of pink or red colouration
is the positive test for five membered lactone
ring (cardenolide).
Baljet test: To 2–3 ml of the test solution add
2 ml solution of picrate solution—yellow,
orange to deep red colour. This test is for
cardenolide and negative for bufadienolide.
Xanthydrol test: This colour reaction specific for
2,6-dideoxy hexoses. To the test solution add 1%
solution of xanthydrol in glacial acetic acid
containing 1% hydrochloric acid. Occurrence of
red colour because of 2,6-deoxy sugar.
Antimony trichloride test: For presence of α-
β-unsaturated lactone ring at C-17.
To the test solution add few drops of
antimony trichloride and trichloroacetic acid
followed by heating the solution, occurrence
of blue or violet colour indicates the presence
of α-β-unsaturated lactone ring.
Raymond test: For the presence of active
methylene group. To the alcoholic extract of
glycoside test solution add 0.1 ml of Raymond’s
reagent (1% solution of m-dinitrobenzene in
alcohol) followed by few drops of sodium
hydroxide solution (20% (w/v)). Appearance
of violet colour indicates positive test for
methylene group.
Structure
• Steroidal nucleus must be present
•3β-OH group involved in glycoside linkage
•14β-OH group at C-14
• A/B ring junction is cis
• B/C ring junction is trans
• C/D ring junction is cis
• Additional OH groups at C-5, C-11 and C16 may be present and the presence of
lactone ring at C-17
Fluorescence reaction of cardiac glycoside
The cardiac glycosides in acidic condition,
derivatise into dehydro derivative and
becomes fluorescent in nature, higher the
number of conjugation, increase in fluorescence
intensity, e.g. aglycone substitution at C-14,
16 give didehydro derivative with the result
trienone has 3 double bonds conjugated with
carbonyl group become more intense fluorescent
and useful to visualise.
TLC chromatogram: The reaction is temperature dependent and influenced by the
respective acid. Reactivity increases from
H
→ CH3SO3H → H2SO
2PO4
4
Subsequent use of oxidant increases the
fluorescence with different colours. For spot
observation phosphoric acid can be used alone
or along with ferric chloride or with sulphuric
acid.
Quantitative Analysis for Cardiac Glycosides
The reaction between digitoxin and 3,5dinitrobenzoic acid (Kedde’s Reagent).
i. Kedde investigated the use of 3,5-dinitro-
benzoic acid for the estimation of digitoxin
and other cardiotonic glycosides.
Introduction to Secondary Metabolites 149
0.4% ethanolic solution (52–58%) of
reagent mixed with glycosides in dilute
ethanol, and 0.1 N sodium hydroxide
solution in fixed amount is then added
and intensity of colour is measured at a
wavelength between 5350 and 5500 Å.
Procedure: The glycosides after extraction
with dilute alcohol purified with lead
acetate solution are hydrolysed in the
presence of hydrochloric acid, the aglycone
extracted with chloroform, repeatedly two
times for the complete extraction, washing
with water, drying over anhydrous
sodium sulphate, evaporation under
vacuum. The residue dissolved in dilute
ethanol, added 3,5-dinitrobenzoic acid
and colour develops with sodium
hydroxide is measure at wavelength of
540 nm.
ii. The French Pharmacopoeia used Baljet
reaction (picric acid) to estimate the
aglycone of foxglove. As per the pharmacopoeia requirement the quantitation of
aglycones fraction, i.e. lactone ring of the
cardenolide glycosides.
iii. HPLC: In these days total quantity of
glycosides concentration is being estimated
by means of HPLC.
SAPONIN GLYCOSIDES
Saponin glycosides are widely distributed in
higher plants. They form colloidal solution in
water, and form honeycomb foam on shaking
that remain persistent for 20 to 30 minutes.
They have bitter acrid taste. Because of
this property drug-containing saponins are
sternutatory and irritant to mucous membranes.
They have ability to lower the surface
tension of aqueous solution, hence used as
emulsifiers in fire extinguishers.
They hemolyse red blood corpuscles (RBC)
especially of cold blooded animals. Hence,
many saponins are used as fish poisons.
On hydrolysis they yield an aglycone
known as a “sapogenin” which form readily
crystallisable compound upon acetylisation.
In human and other warm blooded animals
saponins are not very toxic on oral admini-
stration as they are absorbed in the intestines,
only to a small extent.
Pharmacologically saponins have antitumour,
chemopreventive, antihepatotoxic, antifungal,
antiphlogistic, immunomodulating and
molluscidal activities.
They also have shown activity on the cardiovascular system, the central nervous system
(CNS) and on the endocrinal system.
Classification
Saponin glycoside are divided into two types,
based on their chemical structure of the
aglycone (sapogenins).
Steroidal saponins: They are derivative of
steroids with spiroketal side chains (neutral
saponins).
Triterpenoid saponins: They are acidic
saponins.
Distribution
Steroidal saponins: They are distributed in
monocotyledons angiosperm, i.e.
Liliaceae family (smilex, asparagus)
Agavaceae family (agave, yucca)
Dioscoraceae (diosogenin)
Fabaceae (fenugreek)
Solanaceae (tobacco)
Scrophulariaceae (foxglove)
Steroidal aglycone possess a skeleton with
27 carbons which comprise six rings; E (furan)
ring F (pyran).
Steroidal saponins cause rapid hemolysis
whereas triterpenoid have slower effect.
Triterpenoid saponins are predominantly
present in dicotyledons, e.g. Leguminosae,
Araliaceae, Caryophyllaceae (glycyrrhiza root,
quillaja bark, polygala senega roots, panax,
and ginseng, etc.).
150 Textbook of Pharmacognosy and Phytochemistry I
Classification on the basis of number of
sugar chain in their structure. They are
monodesmosidic having single sugar chain
normally attached at C-3.
Bidesmosidic saponins having two sugar
chains, often attached with C-3 (ether linkage)
and second attached as ester linkage at C-28
(triterpene saponin) or at C-26 an ether linkage
(furostanol saponin).
Tridesmosidic saponins having three sugar
chains.
Physicochemical properties: Due to the
presence of lipid soluble aglycone and water
soluble sugar chains in their structure they are
of amphiphilic nature.
Saponins are surface active compounds with
emulsifying, foaming and detergent property.
In aqueous solution they form micelle above
a critical concentration called critical micelle
concentration (CMC), which depend upon
temperature, pH and salt concentration.
Addition of cholesterol increases their CMC,
size and viscosity.
Qualitative Test
Test Solution
All saponins are soluble to some extent in 80%
alcohol, they are usually extracted with this
solvent to perform chemical tests.
I. Hemolysis test: Test solution is mixed with
standardised red blood corpuscle (RBC)
suspension, the RBC will hemolyse. This
indicates positive test, although steroid
saponins will hemolyse rapidly while the
terpenoid saponins slow in reaction hence not
easy to differentiate.
II. Liebermann-Burchard test: To 1 ml test
solution in a test tube, add chloroform (10 ml),
2 ml acetic anhydride, after shaking the test
tubes add 0.2 ml concentrated sulphuric acid,
followed by heating on water bath maintained
at 40°C, appearance of blue or blue green
colour or red, pink and purple colour for
steroidal and triterpenoid saponins, respectively
can be used to differentiate the steroidal and
triterpenoid on the basis of colour (Table 7.1).
Test for steroid: 2 ml of dry extract dissolve
in acetic anhydride heated to boiling, cooled
then add 1 ml of concentrated sulphuric acid
along the side of the test tubes.
Formation of green colour—steroids
Formation of pink colour indicate triter-
penoid.
Salkowski reaction: 2 mg dried extract shaken
with chloroform, to the chloroform layer add
conc. sulphuric acid alongside of test tube slowly.
Formation of red colouration, indicates the
presence of steroids.
Principle: Sterols react as typical alcohol with
strong sulphuric acid (H
2SO4
).
Acetic anhydride used as solvent and
dehydrating agent.
H
used as dehydrating and oxidising
2SO4
agent.
Quantitative Analysis of Saponins
Extraction of saponins from the crude drug by
the following method and dissolved the pure
saponins in 80% alcohol.
Quantitative estimation can be done by
means of colorimetry, measuring the colour
intensity produced by Liebermann Burchard
test reagent at 430 mm wavelength.
Scheme: Defat the drug material with light
petroleum ether, defatted material, extracted
with 70% alcohol (ethanol/methanol) by soxhlet
extraction process. Filter and concentrate the
extract under vacuum, residue suspended
in water, extract the aqueous layer with
chloroform (twice), remove the chloroform
layer, the aqueous layer further extracted with
n-butanol (three times), washed the n-butanol
extract with water, dried over anhydrous
sodium sulphate and evaporate under vacuum.
Concentrated extract suspended in diethyl
Introduction to Secondary Metabolites 151
Table 7.1: Liebermann Burchard test
Hemolysis test Froth test Liebermann Burchard test Group
+ ve + ve Blue or green Saponin probably steroid
+ ve + ve Red, pink, Probably triterpinoid
purple or violet
+ ve + ve Pale yellow Saturated steroidal or saturated
triterpenoid
+ ve – ve Red, pink, purple Saponin absent diterpene,
or violet triterpene, sterols or related
polycyclic substance
– ve – ve Pale yellow Saponin, unsaturated terpenes,
sterol absent but may contain
saturated sterol and saturated
terpenes
– ve + ve Pale yellow, red pink, Saponin absent probably
purple or violet free diterpene acids
ether, precipitation will take place, separate
the precipitate, it will be pure saponin.
Chromatographic Analysis and Spectral
Analysis
Sapogenins: Hydrolyse the dried plant tissue
with molar hydrochloric acid for 2–6 hours
(reflux). Hydrolysed solid matter, extracted
with petroleum ether, residue dissolved in
chloroform, concentrate and subjected to thin
layer chromatography (TLC) on silica gel
plate.
Solvent System
Acetone : Hexane
4:1
Chloroform : CCl
4
: Acetone
2:2:1
Spray reagent antimony trichloride in con-
centrated hydrochloric acid.
Colour reaction—pink to red colour.
Saponins: Being polar, they can be separated
on paper chromatograph or on TLC using
cellulose plate.
Solvent systems such as:
i. Butanol (saturated with water)
ii. Chloroform : methanol : water
13 : 7 : 2
CYANOGENIC GLYCOSIDES
Cyanogenic glycosides consist of an a-hydroxy
nitrile stabilised by a glycoside linkage, to
sugar moiety.
Organic compounds in plants which on
hydrolysis liberate hydrocyanide (HCN). It is
generally recognised that a small amount of
HCN occur free in plants, but the large amount
is combined in glycosidic linkage. High
concentration of cyanogenetic glycosides have
been reported to be present only in seeds of
few species of plants of Rosaceae family.
Screening Tests
I. Sodium picrate paper test: Place 2 g of
moist shredded plant material or crushed
seeds in a small test tube, followed by the
addition of four drops of chloroform (to
enhance the enzyme activity). A strip of filter
paper saturated with sodium picrate solution
(5 g Na
, 0.5 g picric acid and water to 100
2CO3
ml). Dry the strip and insert between split
cork stopper and then introduce into the neck
of the test tube containing reaction mixture
while inserting the paper strip not to touch the
152 Textbook of Pharmacognosy and Phytochemistry I
side of the test tube. Heat the test tube at 42°C
for 1–2 hours, change in the colour of strip
from yellow to reddish brown indicates the
positive test for cyanogenic glycosides.
II. Feigl-Anger paper test: This paper strip is
useful for quick semi-quantitative analysis of
cyanogenic level of sample. This screening
method is particularly useful when large number
of field samples are to be checked. Positive test
based on colour conversion of the copper reagent
to blue-purple in the presence of cyanide.
by dipping into the mixture solution of 0.5%
copper ethyl acetate solution in chloroform
and 0.5 g tetrabase in 50 ml chloroform (4,4′-
methylene-bis-N-N-dimethyl-aniline) sigma.
Using gloves and tweezers dip the paper in
solution and dry by hanging on the retort
stand. Once dried, store in air-tight ambered
glass container.
Procedure is same as for sodium picrate
paper.
Quantitative Assay Method
Total Cyanide Determination
Substance: Flax seed, apricot, apple seed and
bamboo shoot.
Method: Picrate kit method.
Picrate method: Plant material to be analysed
quantitatively weighed out (immediately after
grinding in glass pestle mortar) into a small
flat-bottom plastic vial or glass vial, add
phosphate buffer (0.5 ml of 0.1 M at pH 4–10)
followed by exogenous enzyme in the case of
cyanoglucoside solution. A picrate paper
attached to plastic backing strip (Bradbury
et al, 1999) is added, close the vial immediately
with screw stopper. After about 16 hours at
30°C, remove picrate paper and immerse in
5 ml water for 30 minutes. Measure the
absorbance at 510 nm and total cyanide (ppm)
determined by the equation
Total cyanide content (ppm) = 396 ×
absorbance × 100/Z
where Z = weight (mg) of ground powder or
leafy material.
FLAVONOID GLYCOSIDES
Flavonoids are plant pigments based on C6C3C
carbon skeleton, e.g. flavones, isoflavones,
flavonones, catechin, leucoanthocyanins,
anthocyanins and aurones.
Flavonoids are found in plant kingdom in
the form of aglycone as well as heterosides.
As aglycone they are found in woody tissues
and heteroside in flowers, fruits and to some
extent in leaves.
Based on degree of oxidation and saturation
of the heterocyclic ‘C’ ring flavonoid may be
classified into following groups:
6
Introduction to Secondary Metabolites 153
Aurone and chalcone: Chalcone and aurone
also contain C
6-C3-C6
backbone. These groups
include 2-hydroxy chalcone, 2-hydroxy
dihydrochalcone, 2-OH retrochalcone, aurones
(2-benzylidene coumaranone) and auronol.
Isoflavonoid
Physicochemical properties: Flavonoids are
yellow coloured pigments, e.g. flavones,
flavonoles, chalcones and aurones. But there
are few which are colourless, e.g. flavans,
flavanones, isoflavones.
On treatment with alkali some give blue
coloration, e.g. anthocyanidins and in acidic
media colour change to red.
Flavonoids are crystalline compounds
soluble in water and alcohol but insoluble in
organic solvents. Aglycones are soluble in
ether and chloroform. Under ultraviolet light
flavonoids give fluorescence of different
colour. Yellow
→→
→ orange
→→
Flavonoids on treatment with AlCl
→→
→ brown
→→
→→
→ red.
→→
give
3
different colour in ultraviolet region. This
property can be used for identification, e.g.
Flavone group—Green
Flavonol group—Yellow to yellowish
green
154 Textbook of Pharmacognosy and Phytochemistry I
Chlacone group—Brown-pink
Aurone group—Pale brown.
Qualitative Tests
Shinoda’s test (cyanidin reaction): Four to five
pieces of magnesium ribbons are added to
alcoholic extract solution of flavonoids,
followed by concentrated hydrochloric acid.
Appearance of reddish colour indicates the
positive test for flavonoids.
Alkaline reagent test: To the flavonoids extract
add few drops of sodium hydroxide solution.
Intense yellow colour indicates flavonoid or
phenolic compounds but on addition of dilute
acetic acid, yellow colour disappears which
indicates the confirmation of flavonoids.
Wilson’s reaction (Boric acid): On treatment
with boric acid, flavonoids form complex
between hydroxyl group and carbonyl
group. Which is not destroyed by addition of
citric acid alcoholic solution.
Oxidising agents (Ferric chloride): Flovonoids
get oxidised to form green or violet colour
complex with iron (ferric chloride).
Catechins on treatment with concentrated
hydrochloric acid, catechin produce red colour.
Quantitative Analysis
i. Total phenolic contents: As the quantity of
flavonoids present in vegetable or fruits drugs
are usually low, data generally being recorded
as total phenolic contents which can be most
conveniently assessed by spectrophotometric
method.
Colorimetric procedure for plant extract
sample depends on the reaction of the flavonoid
with one of a numbers of reagents of varying
selectivity.
Folin-Ciocalteu reagent, which has been used
before and after precipitation of flavonoid in
acidic methanol and vanillin are the classic
reagent.
Acid hydrolysis is done by refluxing the
plant material with hydrochloric acid or
formic acid, then aglycones are extracted with
chloroform or ether.
Separation: Separation is done by liquid
chromatography (LC). Usually reverse phase
(RP) mode is best way on C
or C18 bounded silica
8
columm in conjunction with binary mobile phase
system such as acidified water, methanol and
acetonitrile, less commonly tetrahydrofuran as
organic modifier.
Formic, acetic and tetrafluoroacetic acid
used.
Folin Ciocalteu
The reaction forms blue chromophore constituted by a phosphotungstic-phosphomolybdenum complex, where the maximum
absorption of the chromophores depends on
the alkaline solution and concentration of
phenolic compound, hence the quantity of
alkali should be in excess to check the
cloudiness due to excess alkali, lithium salt
added in the reagent which prevents turbidity.
Method: Take coarsely powdered drug
sample about 1 g, extracted with 1 ml ethanol,
centrifuged at 2°C for 10 minutes. Separate the
aliquot, extract with 10 ml of 80% ethanol and
centrifuge. Pool the aliquot and evaporate to
dryness. Dissolve the residue and prepare
Introduction to Secondary Metabolites 155
dilute extract of different concentrations in a
10 ml test tube and total volume to 3 ml with
distilled water, add 0.5 ml Folin-ciocalteu
reagent (1 : 1 with water) and 2 ml sodium
carbonate (20% w/v) solution heated on
boiling water bath for 1 minute and measure
absorbance at 650 nm (after cooling the
reaction mixture) against the blank reagent.
Standard curve to be drawn by using the
standard phenolic campound (catechu).
ii. Total flavonoid contents: Aluminium
chloride colorimetry method.
Aluminium chloride method: Aluminium
chloride forms stable complex with C-4 keto
group and either C-3 or C-4 hydroxy group of
flavone and flavonol respectively. In addition,
it also forms acid stable ortho-dihyroxyl group
of A or B ring of flavonoid.
Method: 1 ml of known dilution of plant
extract is used. Place in test tube, add methanol
to make volume 2 ml, add 0.1 ml of aluminium
chloride (AlCl
) 10% w/v solution, then add
3
0.1 ml of sodium acetate and 2.8 ml distilled
water. Keep the test tube for 30 minutes at
room temperature, colour develops and
absorbance measured at 415 nm by using
spectrophotometer.
Standard curve prepared by using standard
solution of quercetin.
Alternative Method by Zhishen et al (1999)
In this method known volume of plant extract
(flavonoid fraction) transferred to 10 ml
volumetric flask, add distilled water to make
up the volume to 5 ml, then add 3 ml
sodium nitrite (NaNO
aluminium chloride (AlCl
) (1: 20), then add 3 ml
2
) (10% w/v). After
3
6 minutes add sodium hydroxide 2 ml (1 mol)
solution and final volume made-up to 10 ml
with more distilled water, mix well, the colour
develops, measure the absorbance at 510 nm
by means of spectrophotometer. Absorbance
to be measured against blank solution.
COUMARIN AND THEIR GLYCOSIDES
Coumarins are benzo-α-pyrone derivatives.
These are found in plants both in free state and
as glycosides. It smells like fresh hay and
vanilla was originally used as flavouring agent
but now its use has been banned by British
Food Standards Agency, followed by Germany,
China and other countries. They have
made a law to forbid the usage of coumarin
as food additive. It is found in Tonka beans
(Dipteryx odorata family Fabaceae) and sweet
woodruff (Asperula odorata family Rubiacea).
In ammoniacal solution, these compounds
have a blue, blue-green or violet fluorescence.
This property of coumarin is being used for
qualitative test for coumarin containing
plants such as umbelliferous resin present in
asafoetida and galbanum.
Furanocoumarins are formed by fusion of
furan ring to coumarin at either 6 and 7 position
or 7 and 8 position and occur particularly in
the families Rutaceae and Umbelliferae, e.g.
celery fruits. Bergapten occurs in bergamot oil.
Coumarin found in 150 species belonging
to over 30 different families.
Properties
Occurs as colourless, prismatic crystals.
Have characteristic fragrant odour and a
bitter, aromatic, burning taste.
The glycosides are soluble in water and
dilute alcohol.
In free state are soluble inorganic solvent,
e.g. ether and chlorinated solvent.
Qualitative Evaluation
Spot test: They give blue or violet fluorescence
in ammoniacal solution.
Presence of lactone: Place few drops of
concentrated ether extract of the plant in a
porcelain dish, add one drop of saturated
156 Textbook of Pharmacognosy and Phytochemistry I
solution of hydroxyl amine hydrochloride and
one drop of saturated alcoholic potash. Heat
the mixture on open flame till it starts
bubbling, after cooling add 0.5 N HCl to
acidify the mixture followed by drop of 1%
ferric chloride solution. Appearance of violet
colour indicates the positive test for lactone ring.
Quantitative Evaluation
Widely used method for quantitative estimation
is based upon the conversion of coumarin to
coumaric acid which in basic solution gives
characteristic yellowish-green fluorescence on
exposure to ultraviolet rays.
A known weight of drug to be analysed
extracted with dilute alcohol by heating in a
stoppered vessel on water bath, followed by
addition of sodium hydroxide and heat it
again, it will convert the coumarin to coumaric
acid with the appearance of green fluorcesence
which can be measured spectrophotometrically.
A freshly prepared coumarin standard,
concentration of 0.1, 0.25, 0.50, 0.75 and 1.0%
coumarin per mol, in 0.5 N NaOH, irradiated
and read. The instrument used adjusted
to read 100 with a fluorescence standard
consisting 0.77% of quinine sulphate per ml
in 0.1 N H
. A curve to be plotted from the
2SO4
reading of the coumarin standards. Coumarin
equivalence value for the sample to be read
from the curve.
Dicotyledons family
Rubiaceae, Leguminaceae, Polygonaceae,
Rhamnaceae, Ericaceae, Euphorbiaceae,
Lythraceae, Saxifragaceae, Scrophulariaceae
and Verbenaceae.
Absent in Bryophyta, Pteridophyta and
Gymnosperms but occurs in fungi and lichens.
Pharmacologically, the drug containing
anthraquinone glycosides are purgative in
nature. The derivatives of anthraquinone
responsible for purgative action are: Dihydroxyphenol, e.g. chrysophenol.
Trihydroxyphenol, e.g. emodin or
Tetrahydroxyphenol, e.g. carminic acid.
Carmine natural red cochineal.
ANTHRAQUINONE GLYCOSIDES
Anthraquinone glycosides: These glycosides,
upon hydrolysis, yield aglycones that are di-,
tri-, or tetra-hydroxy anthraquinone or modification of these compounds, e.g. frangulin
hydrolyzes to form emodin and rhamnose,
examples of drugs are: e.g. Rhubarb, senna, aloe,
cascara, etc.
Plant families:
Monocotyledons: Only in Liliaceae family.
C-glycoside, e.g. barbaloin.
Anthraquinone glycosides are present in
drug as free state as well their derivatives. As
Introduction to Secondary Metabolites 157
it get easily hydrolysed, their derivatives often
are found in plant as orange-red compound,
e.g. medullary rays of rhubarb and cascara. As
glycosides are soluble in hot water or dilute
alcohol, while aglycones are soluble in organic
solvents.
Test: Macerate the powdered drug with
organic solvent (ether preferably) after
filtration, filtrate is shaken with aqueous
ammonia or caustic soda, appearance of pink
red or violet colour in aqueous layer indicates
the presence of anthraquinone derivatives.
Borntrager Test for Anthraquinone Glycosides
Hydrolyse the drug (powder form) with
alcoholic potash or 2 M sulphuric acid by
heating for 5 minutes, filter and on cooling
extract with chloroform or dichloromethane,
shake the oraganic layer with dilute solution
of ammonia, red or pink colour in ammonia
layer indicates the positive test.
Modified Borntrager’s test: This test is being
used for anthraquinone glycosides having CC linkage, e.g. aloe-emodin. Ferric chloride or
dilute hydrochloric acid are used for oxidative
hydrolysis. The anthraquinone liberated is
extracted with carbon tetrachloride. Add
ammonical solution to the carbon tetrachloride
layer, will produce rose red or pink violet
colour is positive test for anthraquinone
glycosides.
Test for anthrone and anthranols: Anthrone
and anthranol are the derivatives of
anthraquinone, occur free or as their glycosides.
They are isomeric to each other. Anthrone is
pale yellow in colour, non-fluorescent and
insoluble in alkali.
Anthranol is brownish yellow in colour and
are strongly fluorescent in alkali solution.
Test: Give green fluorescence with borax or
other alkaline solution. Anthranol on treatment
with fuming nitric acid converted to anthraquinol
which give violet colour on addition of ammonia.
Oxanthrone
It is intermediate product between anthrone
and anthranol. Oxanthrone gets oxidised to
anthraquinone by heating the powder drug
(cascara). Boil the powder drug with alcoholic
potash (0.5 N) along with dil. hydrogen
peroxide solution, after cooling add few drops
of acetic acid, acidified mixture is extracted
with benzene. Shake the benzene layer with