Lecture notes glycosides

1. Glycosides
Definition:
Glycosides are (usually) non-reducing compounds, on hydrolysis by
reagents or enzymes yield one or more reducing sugars among the
products ofhydrolysis.
1- Alcoholic or phenolic (aglycone):e.g., O-Glycoside
2- Sulphur containing compounds: e.g., S-Glycoside
3- Nitrogencontaining compounds: e.g., N-Glycoside
4- C-Glycoside
ALPHA AND BETA GLYCOSIDES
1- Sugars exist in isomeric α and β forms. Both α and β Glycosides
are theoretically possible.
2- All natural glycosides are of the β Type.
3- Some α linkage exists in sucrose, glycogenandstarch. Also the
glycoside K-strophanthoside(strophanthidin-linke
to strophanthotriose (Cymarose + β-glucose + α- glucose).
CLASSIFICATIONAND NOMENCLATURE:
1- According to the type of glycosidic linkage:α- glycoside (α-sugar) and
β-glycosides (β-sugar).
2- According to the chemical group of the aglycone involved into the
acetal union:
a. O-glycoside (OH group)
b. S-glycoside (SH group).
c. N-glycoside (NH group).
d. C-glycoside (C group).
3- According to the nature of the simple sugarcomponentof the
glycoside:
a. Glucosides (the glycone is glucose).
b. Galacosides (the glycone is galacose).
c. Mannosides (the glycone is mannose).
d. Arabinosides (the glycone is arabinose).
4- According to the number of the monosaccharides in the sugar moiety:
a. Monoside (one monosaccharide) e.g., salicin.
b. Biosides (two monosaccharide) e.g., gentobioside.
c. Triosides (three monosaccharide) e.g., strophanthotriose.

2. 5- According to the physiological or pharmacological activity ‘therapeutic
classification)
a. Laxative glsycosides.
b. Cardiotonic glycosides.
6- according to the correlationto the parent natural glycoside:
a. primary glycosides e.g., amygdalin, purpurea glycoside A,
b. Secondaryglycosides e.g., prunasin, digitoxin.
7- According to the plant families.
8- According to the chemicalnature of the aglycone:
a. Alcoholic and phenolic glycosides (aglycones are alcohols or phenols)
b. Aldehydic G (aglycones are aldehydes).
c. Cyanogenic G (aglycones are nitriles or derivatives of hydrocyanic acid).
d. Anthracene or anthraquinone G (aglycones are anthracene der.).
e. Steroidal G (aglycones are steroidal in nature, derived from
cyclopentanoperhydrophenanthrene) .
f. Coumarin G (aglycones are derivative of benzo α-pyrone).
g. Chromone glycosides (aglycones are derivatives of benzo-δ-pyrone)
h. FlavonoidalG (aglycones are 2-phenyl chromone structure).
i. Sulphur containing or thioglycosides(aglycones are contain sulphur).
j. Alkaloidalglycosides (aglycone is alkaloidal in nature) e.g.,
glucoalkaloids of solanum species.
Sugars in glycosides:
1- Monosaccharide (glucose in salicin, rhamnose in ouabain)
2- Disaccharides (gentiobiose in amygdalin).
3- Trisaccharides (strophanthotriose).
4- Tetrasaccharides (purpurea glycosides)
5- Rare sugers (deoxy sugers)
6- Sugar linked in one position to the aglycone rarely in 2 positions as
sennosides.
DEOXY SUGARS
A- 6-deoxy sugars
e.g., 1- methylpentoses
2- α-L-rhamnose.
B- 2,6-deoxysugars (calledrare sugars)
e.g.,

3. 1- D.digitoxose 2- D.cymarose 3- diginose
C- 2-deoxy sugars
e.g.,
2-deoxy-D-ribose
Characteristic of2-deoxy sugers:
1- Give positive Schiff’s test for aldehydes.
2- Positive Keller-Kelliani test.
PHYSICAL AND CHEMICAL PROPERTIES
Diversity in structure makes it difficult to find general physical and
chemicalproperties:
1- A- Most glycosides are water soluble and soluble in alcohols.
B- Either insoluble or less soluble in non polar organic solvents.
C- More sugar units in a glycoside lead to more soluble in polar
solvents.
2- Glycosides do not reduce Fehling’s solution, but when are susceptible
to hydrolysis give reducing sugars (C-glycosides are exceptions).
STABILITY AND HYDROLYTIC CLEAVAGE:
1- Acid hydrolysis:
a- Acetal linkage between the aglycon and glycone more unstable than
that between two individual sugars within the molecule.
b- all glycosides are hydrolysable by acids non specific (except C-
glycosides).
c- Glycosides containing 2-deoxy sugars are more unstabletowards acid
hydrolysis even at room temperature.
d- C-glycosides are very stable (need oxidative hydrolysis).
2- Alkali hydrolysis:
1- mild alkali
2- strong alkali
3- Enzyme hydrolysis:
1- Enzymatic hydrolysis is specific for each glycoside there is a specific
enzyme that exerts a hydrolytic action on it.
2- The same enzyme is capable to hydrolyze different glycosides, but α
and β sterio-isomers ofthe same glycoside are usually not hydrolysed by
the same enzyme.
3- Emulsin is found to hydrolysed most β-glycosidelinkages, those
glycoside are attacked by emulsin are regarded as β-glycosides.
4- Maltase and invertase are α-glycosidases, capable of hydrolyzing α-
glycosides only.
EXTRACTION AND ISOLATION OF GLYCOSIDS:
1- Water mixed with different proportions of methanol or ethanol (most
suitable extracting solvent).

4. 2- Non-polar organic solvents are generally used for de-fating process.
3- Glycosides are not precipitate from aqueous solutions by lead acetate.
GENERAL METHODS OF ISOLATION INVOLVE:
1- Destructionof hydrolysing enzymes.
a. Drying for 15-30 min. at 100 C˚.
b. Place plant in boiling water or alcohol 10-20 min.
c. Boiling with acetone.
d. Cold acid pH treatment.
e. Extract at very low temperature.
2- De-fating or purification of the plant material (in case ofseeds).
3- Extraction of the glycosidal constituents by alcohol, wateror dilute
alcohols. Sometimes ether saturated with water for dry material.
4- Concentrate the alcoholic extract (to get rid of the organic solvent). Add
water (or hot water)→ filter any precipitate.
5- Purify aqueous extract:
a- Extract non glycosidal impurities by org solvent.
b- Water soluble impurities precipitate by lead acetate.
6- Precipitate excess lead salts.
7- Isolation of the glycosides from the purified aqueous solution, by
crystallization.
QUALITATIVE TESTING OF GLYCOSIDE:
They do not themselves reduce Fehling’s. but reducing sugars upon
hydrolysis.
To test for the presence of glycosides
Estimate reducing sugars before and after hydrolysis. (by acids or
enzymes)
TESTS DEPENDING ON THE CHEMICAL NATURE OF THE
GENIN:
1- Steroidalor cardiac glycosides:
Give positive Liebermann’s test (steroidal structure).
2- Anthraquinone glycosides and/oraglycone:
Give positive Borntrager’s test, characteristic reddish coloration with
alkalies.
3- Flavonoidalglycosides and/oraglycones:
Characteristic color with, NH4OH, AlCl3, FeCl3.
4- Cyanogenetic glycosides give upon hydrolysis hydrocyanic acid can be
easily tested by change Na bikrate paper (yellow) to red color.
5- Sulphur containing glycosides give black precipitate of silver
sulphate upon treatment with AgNO3 solution.
TESTS DEPENDING ON THE SUGAR PART:

5. 1- Keller Killiani’s test for 2-deoxy sugers:
Specificity of action of the hydrolyzing enzymes is often applied for the
identification of the sugar moieties of glycosides or even the glycoside as
alcohol.
1- Scillarin A [acid hydrolysis] →→→ Scillaridine A + Scillabiose
Scillabiose [Scillabiase] →→→ Rhamnose + glucose.
2- Prunasin [Prunase] →→→ glucose + HCN
+
3- Amygdalin [amygdalase] → Prunasin + glucose
4- Myrosin enzyme is specific for thio D-
glucosides e.g.,Sinigrinand sinalbin.
SPECIAL TESTS BASED ON THE CHEMICAL STRUCTUREOF
THE GLYCOSIDES:
Determination of the glycosidic linkages:
1- By the use of α and β glycosidases.
2- By acid hydrolysis of glycosides, immediate optical activity
measurement of the resulting solution.
Colorreactions basedon the sugarmoiety [2-deoxy sugars]:
1- Keller Killiani:
glacialacetic acid containing + FeCl3 + H2SO4 → brown ring free from
red (acetic acid a quire blue).
2- Xanthydrol:
xanthydrol in glacial acetic containing 1% HCl + glycoside [heat]→ red
color.
N.B. Stability indicating after extraction. U.S.P.
Medicinal importance of glycosides:
1- Cardiac drugs: cardiotonic glycosides e.g., digitalis glycosides,
strophanthus, squill.
2- Laxatives e.g., anthraquinone glycosides of senna, aloes, rhubarb,
cascara, frangula.
3- Counter irritants e.g., thioglycosides and their hydrolytic products
‘allylisothiocyanate’
4- Analgesics e.g., methylsalicylate ‘a hydrolytic productof gaultherin.
5- Anti rheumatic e.g., salicin.
6- Some glycosides are claimed to reduce the capillary fragility e.g.,
flavonoidal glycosides, rutin, hisperidin.
7- Anti-inflamatory: e.g., the glycoside glycyrrhizin has a demulcent,
expectorant and antispasmodic action.

6. 8- More recently as an anticanceragente.g., amygdalin known in the U.S.
as Laetrile.
CARDIAC GLYCOSIDES:
1-The genins of all cardiac glycosides are steroidal in
nature, that act as cardiotonic agents.
2-They are characterized by their highly specific action
cardiac muscle, increasing
tone, excitability and contractility of this muscle, thus
allowing the weakened heart to functionmore efficiently.
All cardio active glycosides are characterized by the
following structural features:
1- The presence of β-OH at position C-3, which is always involved in a
glycosidic linkage to a mono, di, tri, OR tetra saccharide.
2- The presence of another β-OH group at C-14.
3- The presence of unsaturated 5 or 6- memberedlactone ring at position C-
17, also in the βconfiguration.
4- The A/B ring junction is usually (cis), while the B/Cring junction is
always (trans) and the C/D ring junction is in all cases (cis).
5- Additional OH groups may be present at C-5, C-11 andC-16.
1- Cardiac glycosides that α-β unsaturated 5-membered
lactose ring in position C-17 are known as cardenolides. These
are represented by thedigitalis and straphanthus group.
2- Digitalis glycosides contain angular methyl group at C-
10, while strophanthus glycoside are characterized by presence
of either an aldehydic(CHO) or primary alcoholic (C`H2OH)
group at C-10.
Cardenolides
Digitalis glycosides R=CH3
Strophanthus glycosides R=CHO OR CH2OH
3- Cardiac agents that have doubly unsaturated 6-
membered lactone ring in position C-17 are referred to
as Bufadienolides.
4- This group includes the squill glycosides and thetoad venom,
Bufotoxin.

7. Bufadienolides
Squill glycosides R1=OH, R2=H
Bufotoxin R1 & R2 = estergroup
5- The glycone portion at position C-3 of cardiac glycosides
may contain four monosaccharide molecules linked in series.
Thus, from a single genin one may have a monoside, a bioside, a
trioside or a tetroside.
6- With the exception of D-glucose and L-rhamnose, all the
other sugars that are found in cardiac glycosides are
uncommon deoxy-sugars e.g., Digitoxose, Cymarose,
Thevetose.
Digitoxose Cyamarose Thevetose
Isolation difficulties:
1- Major difficulty in the isolation of 1ry glycosides from the crude
drug.. why? because 1ryglycosides are converted into secondary
glycosides by hydrolysable enzymes.
2- Other difficulty is the existence of several closely related
glycosides in the same drug, which are extremely difficult to
separate and purify.
THE CARDENOLIDES
Origin: D. purpurea, D. lanata, D. lutea and D. thapsi
The structures of the common aglycones of
thedigitalis group are indicated below:
Compounds R1 R2
Digitoxigenin H H
Gitoxigenin H OH
Digoxigenin OH H
DX = Digitoxose, DX(AC)=Acetyldigitoxose,G = Glucose.
1- Glycosides derived from Digitoxigenin:
a- Lanatoside A = Digitoxigenin---DX---DX----DX(AC)---G.
b- Acetyl-digitoxin = Digitoxigenin---DX---DX----DX---(AC).
c- Digitoxin = Digitoxigenin------DX---DX----DX.
d- Purpurea gly A = Digitoxigenin---DX---DX----DX---G
2- Glycosides derived from Gitoxigenin:
a- Lanatoside B = Gitoxigenin---DX---DX----DX(AC)---G.

8. b- Acetyl-gitoxin = Gitoxigenin---DX---DX----DX---(AC).
c- Gitoxin = Gitoxigenin------DX---DX----DX.
d- Purpurea gly B = Gitoxigenin---DX---DX----DX---G
3- Glycosides derived from Digoxigenin:
a- Lanatoside C = Digoxigenin---DX---DX----DX(AC)---G.
b- Acetyl-digoxin = Digoxigenin---DX---DX----DX---(AC).
c- Digoxin = Digoxigenin------DX---DX----DX.
d- Deslanoside = Digoxigenin---DX---DX----DX---G
1- The 1ry glycosides Lanatoside A, Lanatoside B,
Lanatoside C are acted by specific enzymewhich split
the terminal glucose, give the 2ryglycosides acetyldigitoxin,
acetylgitoxin and acetyldigoxin respectively.
2- The deacetyl-lanatosides A, B and C can be obtained by
the alkaline hydrolysis of the corresponding lanatosides.
3- Digitoxin, gitoxin and digoxin are obtained by the action
of alkali on their acetyl-derivatives.
SCHEME:COMPLATE
B- THE STROPHANTHUS GROUP
1- The glycoside K-strophanthoside (a trioside),K-
strophanthin B (bioside) and cymarin (a monoside) were
isolated from differentstrophanthus species.
2- The 1ry glycoside K-strophanthoside gives by hydrolysis one
molecule of glucose and the 2ryglycoside K-strophanthoside
B or K- strophanthin B.
3- The later gives by hydrolysis one molecule ofglucose and
the tertiary glycoside cymarin, which on turn hydrolyze into
the genin K-strophanthidinand the deoxysugar cymarose.
The seeds of Strophanthus gratus contains another glycoside
named Ouabain or (G-strophanthin),which yield on
hydrolysis rhamnose and theaglycone ouabagenin.
Ouabagenin differs from K-strophanthidin in having 2
additional (OH) groups at C-1 and C-11 and having a
1ry alcoholic group at C-10 instead of the aldehydicgroup.

9. Ouabain (G-strophanthin)
II-THE BUFADIENOLIDES
This group of cardioactive agents includes the squillglycosides
(the scillarins) and the Toad poison(Bufotoxin).
The genins of squill glycosides differ from those of the
cardenolides in two important aspects:
1- They have six membered doubly unsaturated lactone ring in
position C-17.
2- They have at least one double bond in the steroid nucleus.
The Bufadienolides of Squill
Name of glycosides Structure
Glucoscillarin Scillaridin A ---RH—G---G
Scillarin A Scillaridin A ---RH—G
Proscillaridin A Scillaridin A ---RH
PHYSICAL AND CHEMICAL PROPERTIES OF
GLYCOSIDES:
1- SOLUBILITY:
* The different cardiac glycosides show different solubilities in
aqueous and organic solvents. They are
usually soluble in water or aqueous alcohol andinsoluble in
the fat solvents with exception of chloroform and ethylacetate.
* The higher number of sugar units in the molecule, the greater
solubility in water but lower soluble in chloroform.
* Alcohols are good solvents for both the glycosides and the
aglycones. Therefore, they are considered as the solvents of
choice for the extraction of all CG from drugs.
* pet.ether and ether are used for defatting process of drug, they
do not dissolve CG.
2- STABILITY:

10. 1- Acid hydrolysis cleavage of the glycosides into aglycones and
sugar residues.
2- Specific enzyme usually coexist with CG in plants, which
may split the primary G into G with less sugar units. Thus, CG
deteriorate during drying and storage unless special precautions
are taken.
3- So it is required by many pharmacopoeias that CG
containing drugs must contain not more than specified moisture
content and that these drugs should be stored in sealed
containers overdehydrating agents.
4- It is recommended to heat stabilize these CG, by destroying
the enzymes at higher temperatures. At higher temperature,
the tertiary OH gp at C-14 may split off as water, leading to
formation of an inactive anhydro-form of CG.
5- The gitoxin has in addition to tertiary OH at C-14
another secondary OH at C-16. Both OH gps split as water by
the action of H2SO4 with the formation oftwo additional
double bonds. These with the double bond of the lactone ring
from a conjugated double bond system that makes the
compoundfluorescent in UV light.
The detection of gitoxin in other digitalis G is based on the
above mentioned reaction.
CHEMICAL IDENTIFICATION OF CARDIAC
GLYCOSIDES
1- CGs are steroidal in nature, give +Ve
withLiebermann’s and Salkoviski’s test.
2- CG that contain deoxy-sugars are distinguished by Keller
Kiliani’s test, e.g., digitoxose and cymarose.
3- Cardenolides are distinguished from thescillarins by a group
of color reagents, that are all alkaline solutions
of aromatic nitro compounds, namely,
Kedde’s reagent, 3,5 dinitrobenzoic,

11. Raymond’s reagent, metadinitrobenzene,
Baljet’s reagent, picric acid,
Legal’s test, alkaline solution of sodium nitroprusside.
4- All these nitrocompounds react with the active methylene of
the five membered lactone ring (in alkaline medium) to give
characteristic colors.
MEDICINAL IMPORTANCE
1- Cardiotonics, CHF, rheumatic heart disease, atherosclerosis,
HTN.
2- Diuretics (capillary of the kidneys are dialated).
SAR:
1- The glycone part displays a great influence on the solubility and
the rate of absorption and distribution of the glycosides to the
site of action.
2- Small change in the molecules such as a change of the location
of the OH gp, modify the cardiac activity or even eliminate it
completely.
3- The saturation and/or cleavage of the lactone ring, destroys the
cardiac activity.
Therefore, the closely related CG, differ greatly in the rate of
absorption, duration of action and their cumulative effect.
CARDIAC DRUGS OFFICIAL IN BP &USP
1- digitalis leaf (digitalis tablets)
2- digitoxin tablets 200μg/tablet
3- digoxin injection contain 0.0025% digoxin
4- digoxin tablets contain 250μg/tablet
5- gitalin, lanatoside C, deslanoside, strophanthus, strophanthin,
ouabain and squill.
ANTHRAQUINONE GLYCOSIDE:
TYPES OF ANTHRAQUINONE GLYCOSIDE
1- O-glycosides where the aglycone moiety is 1,8
dihydroxyanthraquinone derivatives, e.g.,
2- O-glycoside where the aglycone moiety partially reduced 1,8
dihydroxy anthraquinone, e.g., Oxanthrone-type.
Emodin-oxanthrone-9-glucoside
3- C-glycoside where the aglycone structure (anthrone der.)

12. Barbaloin
4- O-glycosides where the aglycone moiety is di-anthrone der.
(i.e., dimmer) e.g., Sennosides where there is C-C bridge
between the anthranol units.
Sennoside A&B
The most widely used drugs that contain anthracene
compounds are:
SENNA LEAF:
Consists of the dried leaflet of Alexandrian or
Khartoum senna, Cassia senna (C.acutifolia),Tinnevelly
senna (C.angustifolia).
Constituents:
Dimeric anthracene glycosides derived from two anthrones
moieties which may be:
1- Similar anthrone moiety (Homo-dianthrones) i.e., 2 rhein
anthrone moieties condensate through two C-10 atomes. Thus it
can be exist in two optical forms, Sennoside A (L- form) &
Sennoside B (meso form).
Sennosides A &B
2- Or different (Hetero-dianthrones) i.e., one rhein-anthrone &
one emodin anthrone, Sennoside C (L- form) and Sennoside D
(meso form).
Sennoside C&D
CASCARA
The dried bark of Rhamnus purshiana FamilyRhamnaceae. B.
P. specified that the collection must be made at least one year
before the bark is used (fresh bark contains an emetic principle).
Constituents:
A- Four primary glycosides:
1- cascarosides A&B (glycosides of barbaloin)
2- cascarosides C&D (glycosides of chrysaloin)
B-Two aloins (secondary glycosides):
Barbaloin derived from (C-10-C-glycoside) of aloe-emodin

13. anthrone and chrysaloin derived from (C-10-C-glycoside) of
chrysophanol anthrone.
C- A number of O- glycosides:
e.g., derived from emodin, emodine oxanthrone, aloe emodin
and chrysophanol.
E- Free anthraquinones:
Aloe emodin, chysophanol and emodin.
FRANGULA BARK:
1- Frangulin (frangula emodin rhamnoside).
2- Glucofrangulin (frangula emodin glucorhamnoside).
3- hydrolysis of glucofrangulin yields frangulin and glucose.
4- Hydrolysis of frangulin gives frangula emodin and rhamnose.
RHUBARB
1- Consist of glycoside of rhein, rhein anthrone, chrysophanol and
aloe emodin.
2- Dianthrones of heteroanthrone types are palmidin A, B, C,
Rheidins, sennosides A&B and their oxalate esters (sennosides
E&F).
3- The presence of tannins in rhubarb makes the drug constipating.
So in small doses, rhubarb exerts no purgative action but acts
only as intestinal astringent, but large doses cause purgation.
USES:
Cascara is a purgative, mainly in the form of liquid extract, elixir
or as tablets prepared from a dry extract.
The laxative action of the crude drugs is always higher than
from their content of anthracene der. The different
anthracene der. contained by the crude drug are said to
exert asynergistic action.
Thus, the naturally occurring anthracene glycosides were
found superior to thesynthesis of numerous hydroxyl
anthracene der.
Some of these synthetic compounds act too drastically and
also caused kidney damage.
The only compound which is used to some extent in current
medicine is danthrone. It is also used as a standared in

14. colorimetric assays of anthraquinone glycosides.
Danthrone
Note:
1- The 1ry glycosides are more active than the aloins while the
free anthraquinon have little purgative activity.
2- C-C glycosides, aloins are very resistance to hydrolysis and are
not easily hydrolysed (like other anthrones and anthranols) to
corresponding anthraquinones.
3- Aloin type glycosides are present in aloes and other anthracene
bearing drugs of the family liliaceae.
SAR
1- Glycosilation:
The purgative action of anthracene bearing drugs is owed to
their anthracene glycosidal content rather than their content of
free anthracene aglycones (i.e., glycosylation is the main
requirement for activity, as the sugar moiety serve to transport
the aglycone to the site of action in the large intestine).
2- Hydroxylation:
Hydroxylation of C-1, C-8 is essential for activity. Increase
hydroxylation leading to increase solubility.
3- Oxidation level:
The degree of oxidation at positions C-9 & C-10 plays an
important role in the pharmacological activity. Higher oxidation
level at C-9 & C-10 caused lowering of activity. i.e., anthrones
and anthranols are more potent than their corresponding
oxanthrones, which in turn more active than their corresponding
anthraquinones. Complete reduction of C-10 &C-9 lead to
complete loss of activity.
4- The nature of substances at C-3:
Derivative with CH2OH (as in aloe emodin) are more active than
those with CH3 substitution. The latter more active than
derivative with COOH substitution at C-3.
Anthraquinone glycosides containing adimer more active than a
monomer.

15. 5- Effect of storage on the active of anthracene glycosides:
a- Prolonged storage of anthracene bearing drugs may bring
oxidation of anthranols and anthrones to give the less
active anthraquinones. Thus, the activity of drugs decreases by
time. However,anthraquinone glycosides do not cause
anygriping action (like anthranol and anthone), thus no
antispasmodic such as belladonna is prescribed with them.
b- Drugs as senna, Aloe and cascara preparationsretain their
activity for a long time.
c- Cascara and frangula must be aged for one yearbefore it is used
for medicinal preparation.WHY?
Stability is achieved as follows:
1- In senna, there is dimeric glycoside in which a C-C bridge
between two anthrone units is formed (the C-10 position of one
anthrone is involved in a C-C-covalent bonding with C-10 of the
other anthrone). Thus, the C-10 position can not be easily
oxidized and the anthrone structure is stabilized.
2- In the aloe, the aloins (barbaloin & chrysaloin) contain C-C
glycosidic linkage (anhydroglycosides) stabilise the anthrone
structure.
4- In cascara, cascarosides have an additional O-glycosidic
linkage (beside the C-10-C glycosidic linkage. The solubility of
cascarosides is increased and thus, produce higher
pharmacological activity.
PROPERTIES OF ANTHRAQUINONE DERIVATIVES:
The glycosides are extracted and hydrolyzed by boiling the drug
with acids.
The aglycones are extracted from the acidic solution with ether
or benzene. Upon shaking the ether or benzene layer with
aqueous alkali or ammonia solution, the aqueous layer assumes a
deep red color, because of the formation of anthraquinone salts.
Borntrager’s reaction can distinguish anthraquinones from

16. anthrones and anthranols whichdo not give the test unless they
are converted to anthraquinone by oxidation with mild oxidants
such as hydrogen peroxide or ferric chloride.
Official anthraquinone drugs in B.P and U.S.P.:
1- Senna leaf & senna fruit (pod).
2- Aloes.
3- Cascara tablets, elixir, dry exract, liquid extract.
4- Rhubarb powdered, tincture.
5- Danthrone
6- Frangul bark
FLAVONOIDAL GLYCOSIDES
- Flavonoidal compounds are considered as the largest group of
naturally occurring phenols.
- Flavonoidals constitute the majority of the yellow colored plant
pigments.
- Many flavonoidal compounds present as a glycosidic or as a
free forms.
- All derived from the same parent nucleus, 2-phenyl-benzopyran
(flavan), thus they have a basic C-15 skeleton.
Flavonoidal compounds are classified according to
the oxidation level of central pyran ring they are classified
into flavones, isoflavones, flavonols,flavanones, (true
flavanoids) anthocyanidins,chalcones and aurones.
True flavones, are 2-phenyl chromones (2-phenyl
benzopyrone), while isoflavones are 3-phenyl chromones der.
Flavonols are 3-hydroxyflavones, while flavanones are 2,3-
dihydro der. of flavones (2,3-double bond is lacking).
(2-phenylbenzopyran) (2-phenylbenzopyrone)
Anthocyanidines, chalcones and aurones are lack the typical
flavone structure. Anthocyanidins and its glycosides
(anthecyanins) are ionic oxonium salts. This is responsible for

17. the permanent blue, purple, violet, mauve, and red color of
flower, fruits and leaves of higher plants.
Anthocyanidins and anthecyanins are soluble in polar solvents.
Cyanidin chloride is an example of anthocyanidines .
Chalcones, have no central pyrone ring, so they are not true
flavonoidal compounds. The parent compound chalcone, is
chemically phenyl-styryl ketone, or benzylidene acetophenone.
Aurones are oxidized forms that are obtained by enzymatic
oxidation. Instead of the central pyrone ring of the normal
flavonoidal structure, auroneshave five membered ring.
Chalcon Aurone
PROPERTIES OF FLAVONOIDS
Flavonoids dissolve in alkalis give intense yellow color
solution, on the addition of acid become colorless.
Flavonoids exhibit strong fluorescence under UV light.
Flavonoidal glycosides are soluble in water and alcohol.
Ethylacetate is the solvent of choice for the extraction of
flavonoids from aqueous solution.
Flavonoids compounds may be characterized through
the investigation of their UV Spectra, that usually show two
main bands,
1- Band at higher wavelength (band I) which is attributed to
the cinnamoyl fraction of the flavonoidal structure Why?.
2- Band at lower wavelength (band II) which is due to
the benzoyl fraction of the flavonoidal structure.
STRUCTURE: COMPLETE
Band I >> 300 nm
If R= H R=OH R=O-substitution
Flavones flavonols 3-sub flavonol

18. Band I: 304-350 nm Band I: 352-385 Band I: 328-357
Band II << 300nm
(250-280 nm)
Note:
More OH in ring A: Bathochromic shift in band II.
More OH in ring B: Bathochromic shift in band I.
Shift reagents:
Back to lab.
EXAMPLE OF FLAVONOIDS GLCOSIDES
1- Diosmin: flavone glycoside
Occurance: buchu leaves, Barosma crenulata F. Rutaceae.
Uses: diuretic and diaphoretic action of the leaves is owed in
part to diosmin, and in part to diosphenol, the main constituent
of the volatile oil of the leaf.
Diosmin
Upon hydrolysis, diosmin yields rhamnose, glucose
and diosmetin.
2- Rutin and quercetrin: are examples of flavonol glycosides
a- Rutin occurs in the leaves of buckwheat. It is the 3-
rhamnoglucoside (called rutinose) of the genin quercitin.
It gives on hydrolysis the aglycone (quercitin)beside one
molecule of glucose, and one molecule of rhamnose.
Rutin is used to
1- Decrease capillary fragility.
2- It is a biflavonoids that plays a true vitamin function.
b- Quercitrin is quercitin 3-O-rhamnoside.
It occurs in the bark of Quercus tinctoria.
Quercitrin yield upon acid hydrolysis rhamnose and quercetin.
The aglycone quercetin occurs in bearberry leaves (Uva Ursi)
and has a diuretic action of the leaves.

19. 3- Hesperidin: it is an example of flavanones. It is the main
flavonoidal glycoside of citrus fruits.
Upon hydrolysis by acid, hesperidin gives rhamnose, glucose
and hesperitin.
Uses:
1- Hesperidin appears to be identical to vitamin P (citrin).
2- It is necessary for absorption and retention of vit C that lead
to decrease capillary fragility.
3- Decrease CVD and HTN.
Uses of flavonoids:
1- Increase capillary resistance and decrease vitamins C & P
deficiency.
2- They are recommended in the treatment of thrombopenia (blood
coagulation).
3- They are reported of value in the treatment of influenza, when
given with ascorbic acid.
Isoflavone:
1- Genistein show significant oestrogenic activity.
2- Rotenoids employed as insecticide.
Flavono-lignans
Coupling of a flavonoid moiety with hemi-lignan molecule by
oxidative coupling.
SILYMARINE
The leaves and fruits of Silybum marianum family Compositae
contain silymarin (silybin).
1- Silymarin is a very effective lipotropic and hepato protective
therapy.
2- It is a free radical scavenger.
3- Supportive treatment of acute and chronic alcoholic poisoning
and toxin induce hepatitis.
4- It is used for treatment of liver cirrhosis caused by plant
toxins (mushroom, amanita), silymarin is applied as intravenous
injection.

20. 5- Silymarin is available in the market in the form of tablets,
effervescent granules. Trade name legalon, silyhexal,
silirex…etc.
Synthetic flavonoids
Flavoxate:
Uses:
To remove pain (anti-spasmodic) and anti-inflammatory of the
genitor urinary tract.
Flavoxate tablets are available under several names: Urispas,
Uronid, Spasurit, Genurin).
SAPONINS
* Saponins are a group of amorphous colloidal glycodides which
is wiedly distributed in the higher plants.
* Have ability to form lasting foam when shaking in aqueous
solution.
* They are excellent emulsifying agents (modify surface
tension).
* Formerly used as detergents to replace soap (e.g., quillaia).
* Saponins are colorless and optical active. They form colloidal
solution with water and are soluble in alcohol and dilute
alcohols.
* Saponins have haemolytic properties, they precipitate the
cholesterol and lethisins that exist in the memberanes of the
red blood cells and thus haemoglobin is liberated. So,
saponins are extremely toxic when injected into the blood
stream. However, they are not harmful when taken orally.
* Saponins are difficult to purify. However, they precipitated

21. from solutions containing them by the addition of a solution
of the sterol, filtering off the insoluble sterol-saponin
compound and boiling it with toluene which resolves the
compound again into sterol (which is soluble in toluene) and
saponin (which is insoluble in toluene).
Chemically:
Saponins are classified according to the genin part into:
1- Steroidal type C25.
2- Triterpinoidal type C30.
Both types of saponins have the glycosidic linkage atposition 3.
Medicinal importance of saponins:
1- The steroidal saponins are structurally related to modern
synthetic compounds that have a therapeutic significance, such
asadrenocortecoids and the sex hormones. So, they are a
suitable precursors in the partial synthesis of these hormones,
e.g., Diosgenin(sapogenins) isolated from the rhizome
ofDioscoria species.
2- Saponins increase the rate of absorption of many
pharmacological active substances (e.g., cardiac glycosides).
3- Many saponin-containing drugs are used asexpectorants (e.g.,
Ipeca, Senaga and liquorice) as their contents of saponins
stimulate bronchial secretion and also activate the ciliary
epithelium of the bronchi.
a-The triterpenoidal saponin glycoside,glycyrrhizin, is the main
sweet principle ofliquorice. It is calcium and potassium salts of
glycyrrhizic acid, which in tern is the diglucuronic
acid glycoside of glycyrrhitinic acid.
b- Beside being a valuable flavouring and sweetening agent,
liquorice has demulcent, expectorant and antispasmodic action.
All these activities attributed to the saponin, glycyrrhizin.
c- Recently, glycyrrhizin was shown to be effectively in gastric
ulcer treatment and have a cortisone like action in rheumatic

22. arthritis and other inflammatory diseases.
Saponins drugs officially in the B.P and U.S.P:
1- Quillaia bark: used as emulsifier.
2- Liquorice root: used as flavouring agent and expectorant.
TANNINS
1- Tannins are widely distributed phenolic plant constituents.
It is characterized by being able to combine with proteins of
animal hides thus preventing theirputrefaction and converting
them into leather (true tannins).
2- Tannins are detected qualitatively byGoldbeater’s skin test (a
tanning test), and can bequantitatively estimated
by absorption on standard hide powder. Only high
molecular weight tannins that are capable of tanning hide.
It is more acceptable to define true tannins as those high
molecular weight phenolic plant constituents that can be
detected by Glodbeater’s skin tanning test.
3- True tannin solutions have the ability of precipitating soluble
proteins (gelatine), heavy metals, alkaloids and glycosides.
4- This will exclude simple molecular weight compounds such
as gallic acid, catechin, flavan-3,4-diol and chlorogenic acid,
that usually coexist with true tannins. These simpler tannins like
compounds are referred to aspseudotannins.
TRUE TANNINS ARE DISTINGUISHED INTO TWO
MAIN CLASSES:
Hydrolysable tannins
Condensed tannins
1- Hydrolysable tannins:
a- These can be hydrolyzed by acids or enzymes to
give phenolic acids (gallic or ellagic) and glucose, so
called phenolic acid glycosides.
b- Tannins of gallic acid are called gallitanninsand those

23. of ellagic acid is called ellagitannins.
c- Dry distillation of hydrolysable tannins gives pyrogallol. This
class is named pyrogallol tannins.
d- Gallitannins and ellagitannins react with ferric salts to give
bluish color precipitate.
2- Condensed tannins:
a- These are more resistant to hydrolysis upon prolonged heating
with acids.
b- They undergo decomposition (not hydrolysis) to give a red
soluble compound (phlobaphane).
c- Condensed tannins are derived from catechin and flavan, 3,4-
diol.
d- Dry distillation of condensed tannins gives catechol. This
class is named catechol tannins.
e- Being phenolic, it reacts with ferric salts to give greenish
color precipitate.
ALCOHOLIC AND PHENOLIC GLYCOSIDES
1- Salicin:
Salicin is classified as:
1- Alcoholic glycoside, as it contains freeprimary alcoholic
group.
2- A phenolic glycoside, as its aglycone is phenolic in nature.
Salicin
PROPERTIES OF SALICIN:
1- Salicin is obtained from different species of Salix, the principle
commercial source is Salix fragilis.
2- Salicin is used for many years as a remedy in the treatment of
fever and rheumatism.
3- It is now used as an analgesic-antipyretic in case of periodic
fever. It is better tolerated in the stomach than sodium salicylate,
asprin and other antipyretics and anti-inflammatory agents,
which have largely displaced in medical practice.
4- Salicin is hydrolyzed by the
enzyme emulsininto saligenin (Salicyl alcohol) and glucose.
5- Acid hydrolysis of salicin gives glucose and a
phenolic ether called saliretin which is a condensation product

24. of two molecules ofsaligenin.
6- Oxidation of saligenin gives salicylic acid and this accounts for
the medicinal value of salicin.
ARBUTIN
1- Arbutin is a phenolic glycoside that occurs in bearberry
leaves Arectostaphyllos uva ursi.
2- When hydrolysed with acids or with emulsin it yields glucose
and hydroquinone.
3- It is used as diuretic and also has bactericidal action. This
activity is due to the hydroquinone given by hydrolysis.
4- Uva ursi leaf contains also methylarbutin (the methyl ether of
arbutin), that also contributes to the diuretic and urinary
antiseptic action of the leave.
ALDEHYDE GLYCOSIDES
GLUCOVANILLIN:
1- Glucovanillin is a glycosidal constituent of green vanilla pods.
2- The fruits of the plant (pods) are collected and carefully cured.
To permit enzymatic action on the glycoside with the liberation
of vanillin (the aglycone) which is the principal flavouring
constituent of the pods.
3- Vanillin is widely used as a flavouring agent. It may be obtained
from vanilla pod or prepared from the
glycoside coniferin, lignin or from thephenolic volatile oil
constituents eugenol.
1- From Coniferin and lignin
2- From Eugenol
The bulk of vanillin which is produced commercially is
prepared from lignin, which gives upon hydrolysis coniferyl
alcohol.
Lignin is obtained in extremely large amounts as a by product
of timber industry.
CYANOGENIC GLYCOSIDES
1- These are glycosides that are yield hydrocyanic acid as one

25. of their hydrolytic products.
2- Plant containing these glycosides are toxic.
3- The aglycone part is cyanohydrin of a carbonyl compound
(condensation product of HCN with analdehyde or keton).
4- The majority of cyanogenic glycosides are derived of
benzaldehyde cyanohydrin.
AMYGDALIN
D-Mandelonitrile gentiobioside
1- Amygdalin is the most widely distributed cyanophore glycoside.
2- It occurs in several Prunus species, and is obtained from bitter
almonds (Prunus amygdalus Var. amara Family Rosaceae).
3- Amygdalin is considered as gentiobioside of D-
mandelonitrile. Gentiobioside is a reducing disaccharide
consisting of two molecules of β-glucose linked by β-1,6
linkage.
4- Acid hydrolysis of amygdalin split two molecules of glucose
and one molecule of mandelonitrile. The latter decomposes
spontaneously to form benzaldehyde and HCN.
5- Different enzymes act upon amygdalin in different ways:
DETECTION OF CYANOGENIC GLYCOSIDES
The plant material is cutted into small fragments and then a filter
paper moistened with sodium picrate is then suspended in the
neck of the flask, the flask is stoppered and incubated in a warm
place (40˚C) for about 30-60 min. By this time, the coexisting
enzymes act upon the glycosides with the liberationof
HCN which turns, the sodium picrate paper convert to brick red
color.
SULPHUR CONTAINING GLYCOSIDES:
Thioglycosides
1- A number of plants of the family Cruciferae yield glycosides
containing sulphur.
2- Hydrolysis of these, yield volatile
genins ofthiocyanate structure e.g., mustard oils.
3- The best known compounds Sinigrin and Sinalbin,two

26. glycosides occurring in black mustard and white mustard seed
respectively.
4- The glycosides and their specific enzymes are found
in different cell in the seeds. They donot interact until they are
brought together by the distruction of the cell walls.
5- The general structure of thioglycosides is:
6- The anion is called the glucosinolate ion, R may be aliphatic
or aromatic. The cation (X) may be asimple metal ion or
a complex organic cation, e.g., sinapine ion of sinalbin.
7-Sinigrin gives upon hydrolysis, glucose, allylisothiocyanate
(volatile oil of mustard) and potassium acid sulphate.
8- Hydrolysis of the glycoside sinalbin gives a phenolic
isothiocyanate (Acrinyl isothiocyanate), glucose and the acid
sulphate of a quaternary alkaloid,sinapine.
9-Black and white mustard seeds are used as rubefacients and
counter irritants. These effects are attributed to their contents of
thioglycosides.
COUMARIN GLYCOSIDES:
Aglycone 1- coumarin (benzo-α-pyrane).
2-coumarin derivative (hydroxyl and methoxy coumarins).
3- Umbelliferone [7-hydroxy coumarin] is the lactone of umbellic
acid which occurs both in the free state and in the form of
glycosides in someresins of the Umbelliferae (Asafetida and
galbanum).
4- Coumarin and its derivatives give blue or violet fluorescence in
aqueous ammonical solutions (conjugated double bond system).
This is made use of in qualitative testing for coumarin,
coumarin derivatives and coumarin glycosides and drugs
containing them.
5- The oleo gum resin galbanum that contains umbelliferone in
a free state is distinguished from asafoetida that contains
only combind umbelliferone, by the addition of ammonia to its
aqueous alcoholic extract, when the characteristic blue
fluorescence is given. Asafetida responds positive to the

27. fluorescence test only after acid hydrolysis.
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